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ETX FREQUENTLY ASKED QUESTIONS (FAQ)
Last updated: 23 June 1997
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ETX FREQUENTLY ASKED QUESTIONS (FAQ) |
This ETX FAQ was prepared by Dominique Rodriguez. It is presented here with the permission of the author. Please address all comments, corrections, and additions to Dominique. Dominique's email address was changed at the end of June 1997; I will post the new one as soon as I receive it.
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ETX Frequently Asked Questions List (FAQ)
Dominique RODRIGUEZ domino@anacad.fr v0.alpha_3, 23 June 1997
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Answers to Frequently Asked Questions about Meade ETX telescope
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1. Introduction
* 1.1 Overview
2. Miscellaneous Questions
* 2.1 I'm a novice, and I have some questions. Where should I start?
* 2.2 What Usenet Newsgroups are there for the ETX?
* 2.3 Are there any good WWW links for ETX stuff?
* 2.4 What are good places to buy ETX's and accessories?
* 2.5 When is the next Meade coming out? Should I wait?
* 2.6 What are the specifications of the ETX?
* 2.7 Can the unit be attached to a standard camera tripod?
* 2.8 How does the ETX compare to the TeleVue Ranger?
* 2.9 How does the ETX compare to other instruments?
* 2.10 Do I need a perfectly level surface for doing the polar alignment?
* 2.11 Can the ETX be a first scope for a novice?
* 2.12 Meade advertises a resolution of 1.3", is it true?
3. What kind of accessories can I used on my ETX?
* 3.1 Which tripod can I used?
* 3.2 Which cases/bags can I used?
* 3.3 Which eyepieces can I used?
* 3.4 Which barlow lenses can I used?
* 3.5 One told me that using a Barlow on the ETX will give a too dark image?
4. What possible mechanical modifications/enhancements can I make on my ETX?
* 4.1 Can I computerized the ETX? (goto function)
5. Contributors
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1. Introduction
This FAQ is maintained by Dominique RODRIGUEZ (domino@anacad.fr)
1.1. Overview
The purpose of this FAQ is to provide answers to commonly asked
questions about the Meade ETX Telescope. This list contains
information which has not necessarily been verified, and is not
guaranteed to be correct. It has been compiled from various postings
in the newsgroups sci.astro.amateur, as well as other sources.
2. Miscellaneous Questions
* 2.1 I'm a novice, and I have some questions. Where should I start?
Having access to Internet, start there. There are innumerable WWW
sites on the subject of astronomy and advice to the beginners. Also
try local astronomy stores - they will have information about local
clubs, meetings, star parties, seminars, observatories and
planetariums.
* 2.2 What Usenet Newsgroups are there for the ETX?
You can find info on sci.astro.amateur, there is also a mailing list
dedicated to the ETX, for subscribing goto:
o http://metxug.elendil.com/newsltr/newsindx.html
* 2.3 Are there any good WWW links for ETX stuff?
Try http://www.weasner.com/etx/ which is a good starting point.
It has links to many other pages of interest.
* 2.4 What are good places to buy ETX's and accessories?
Check at the authorized Meade dealer of your area:
o http://www.meade.com/dealers.d/dlrtop.html
Try subscribing to ASTROMART or visit their site:
o http://www.astromart.com/
* 2.5 When is the next Meade coming out? Should I wait?
They will not tell. Don't wait. ETX is a great scope that will give
you years of good service. The technology did not change much since
Newton, and his telescope would be quite useful today. It makes more
sense to go for a better or bigger scope than to wait for next design
and waste all this observing time. Remember that ETX offers foremost
portability and ease of set up. That will make it more likely for you
and your family to use it. Bigger and more complex scope will give you
better image, but the pain of taking it out and setting it up will
make you turn on the TV instead. I know some people that have both and
their ETX time is few times that of the bigger scope time. Don't wait!
I waited 20 years too long.
* 2.6 What are the specifications of the ETX?
Optical design.........................................Maksutov-Cassegrain
Clear aperture.................................................90mm (3.5")
Focal length................................................1250mm (48.6")
Focal ratio (photographic speed)....................................f/13.8
Near focus....................................................3.5m (11.5')
Resolving power...............................................1.3 arc secs
Super Multi-coatings..............................................standard
Limiting visual stellar magnitude.....................................11.7
Maximum practical visual power........................................325x
Optical tube dimensions.............10.4cm dia. x 27.9cm long (4.1" x 11")
Secondary mirror obstruction...........................27.9mm (1.1"); 9.6%
Telescope mounting..................................fork type; double tine
RA drive motor................................................4.5-volts DC
Hemispheres of operation.......................north and south; switchable
Slow-motion controls..................................manual; R.A. and Dec
Bearings...............................................R.A. and Dec: Nylon
Materials:
Tube body................................................aluminum
Mounting........................high-impact ABS, steel reinforced
Primary mirror......................................Pyrex. glass
Correcting lens........................BK7 optical glass, Grade-A
Telescope dimensions...................38cm x 18cm x 22 cm (15" x 7" x 9")
Telescope (incl. tripod) net weight........................4.2kg (9.2 lbs)
Telescope shipping weight.................................5.6kg (12.4 lbs)
* 2.7 Can the unit be attached to a standard camera tripod?
Yes, technically possible but not advisable. The scope weighs about 5
kg and if used in equatorial position it puts serious strain on most
tripods. It may make it unstable and you can ruin your ETX. A quality
of mounting can be measured by how long does it take to stabilize
after touching it. Most cheap tripods will take 5 to 10 seconds which
makes them in my eyes nearly unusable. Every time you adjust something
or a slight breezes will make them swivel and shake. I have seem
mounts that shake when one thumps the ground next to the tripod.
Notice that almost all photo tripods come to a narrow point someplace
in their set up. If this point is plastic, the tripod is not
usable. The stronger that point the better. This is why tripods made
for VIDEO applications are much better, but often cost more than the
whole ETX. They are designed for heavy cameras and no shakes, but
minimal adjustability. Notice that astro tripods are not connected to
a single point like photo tripods, but rather to a large table, which
makes them much more stable. Notice that the scopes are suspended in
such a way that the center of gravity is over the middle of the
tripod. This is almost not attainable in photo tripods in the
equatorial set up.
* 2.8 How does the ETX compare to the TeleVue Ranger?
Following are all the articles I found on sci.astro.amateur for last
year (1996) concerning this topic.
- from (http://www.mich.com/~bhalbroo/startimes6_96.html)
Some of you may be thinking that, while the ETX vs. Questar test makes
sense, comparing the ETX with the TeleVue Ranger is like comparing
apples to oranges. The Ranger is a short focal length refractor
particularly well suited to stunning wide field views of extended
deep-sky objects. In contrast, the ETX is an f/13.8
Maksutov-Cassegrain with nearly three times the Ranger's focal
length--definitely not a low power, wide field viewing instrument.
- from Tim Gillespie (tgillesp@mail.tds.net)
Clayton E. Cramer wrote:
[edited]
> I could only compare them in daylight. The ETX had a very
> unpleasant black spot with the low powered eyepiece that was in it.
^^^^^ ^^^^
This is really an unfair comparison. The black spot was due to two
factors:
1) A low powered eyepiece produced a rather large exit pupil and 2)
Being daytime, your pupil was contracted, thus being unable to accept
the large exit pupil. This secondary shadow would not be apparent at
night.
I find that the easiest way to select a purchase is to compare features
side-by-side. So, here goes. Some of these criteria are objective data,
others are subjective and reflect my opinion (your mileage may vary):
ETX Ranger
--- ------
optical performance: very good (though obstructed) excellent
(unobstructed)
focal length: 1250mm 480mm
focal ratio: 13.8 6.8
aperture: 90mm 70mm
central obstruction: 27.9 mm diameter none
light gathering area: 73.2cm^2 (9^2 - 2.79^2) 49cm^2
mount: passable equatorial none
price: $500 - $600 $1000 (?)
fit and finish: fair excellent
portability: excellent excellent
ease of use: excellent fair (no mount)
D Rodriguez Here: the price of the Ranger is wrong, Tim send an
aknoledgement in a latter mail saying he quoted the price of the
Pronto, the Ranger is $600.
- from Tim Gillespie (tgillesp@mail.tds.net)
Scott Kroeger wrote:
> Also the ETX doesn't gather quite as much light as it's aperture
> suggests. The ETX has two mirrors (which I'll guess are about 94%
Good point Scott. However, I believe that both mirrors are coated for
96% reflectivity, not 94%. This equates to a reflective transmission
loss of 7.84%, bringing the ETXs effective light gathering area closer
to 67.5 cm^2.
> reflective, does anybody thing Meade is doing better than this) and a
> deeply curved corrector which will tilt the AR coatings off normal for
> the incident beam over a substantial fraction of the aperture. AR
> coatings work best on-axis (where you can't see them). I have seen a
> little off-axis reflection from a head-on view of the ETX front end, so
> some light is coming back off the corrector. I wouldn't hazard even a
> wild guess as to how much.
>
> If we presume the transmission losses are equivalent for the Ranger
> objective and ETX corrector, we can simply take the 73.2cm^2 x 0.94 x
> 0.94 and get 64.7cm^2.
Quite true, recall that the Ranger is an air-spaced doublet, giving four
air-to-glass interfaces which probably about offsets the effects due to
the deep curvature of the corrector on the ETX. Lets split the
difference, and say about 65cm^2 effective area. That is about a 33%
greater light grasp for the ETX.
> Given the inevitable shift of energy from the airy disc to the
> diffraction rings in the ETX (because of the obstruction) I think it's
> small light gathering gain might be offset by the somewhat more diffuse
> star images which lower surface brightness and can cause dim stars to
> fall below the eye's detection threshold. For diffuse objects the ETX
> will give brighter images, but for dim clusters, globular resolving and
> planetary views I'd expect a close race (perhaps dominated by the
> difference in eyepieces needed to get the same FOV).
Couldn't have said it better. The ETXs aperture DIAMETER is about 29%
greater than the Ranger, but its aperture obstruction is about 31% (by
diameter, NOT area) so, if we make the EXTREMELY tenuous assumption that
both relationships (aperture to resolution, and obstruction percentage
to resolution) are essentially linear, the effects more or less cancel
each other out.
In my experience, the Ranger gives superb lunar and planetary
images. I have only looked through the ETX once, and found its images
excellent as well. A side-by-side comparison would be interesting. I
also find it interesting that the ETX is more suited to high power
viewing than the Ranger due to its higher f-ratio and longer focal
length. For example, a 4.8mm eyepeice in the ETX gives a magnification
of 260x. To get the same magnification on the Ranger, you would need
either a 1.8mm eyepiece (with the attendant poor eye relief) or a 2.5x
barlow (with its attendant transmission loss, potentially reflective
extra surfaces and other aberrations)
> But there is that big difference in price and the ETX's EQ mount. Those
> are two pretty important distinctions in my book.
I guess the difference is whether you are interested in performance or
quality. IMO, the ETX equals, and in deep space performance, exceeds
the Ranger in performance, but lacks the feel of quality that all
TeleVue products possess.
- from Wil Milan (wmilan@airdigital.com)
I've compared the ETX and the Ranger directly. After doing so, I bought
the Ranger. The ETX is a very nice small scope, but after a few weeks of
use I've found the Ranger nothing short of amazing. With a mild Orion
Skyglow filter I can easily see the Veil nebula, the North American
nebula, and other objects which many find elusive on much larger scopes.
I've also used it at high power and was amazed that the image did not
break down even at 288x (100x per inch!).
Though I originally bought the Ranger for use as a guide scope on a
couple of larger scopes, I've found it so capable that it is now my
standard "quickie" scope for short sessions and for traveling. Based on
my experience I would not hesitate to recommend the Ranger over the ETX.
That's not to take away from the ETX, which I do think is a very nice
scope, but the Ranger is a true jewel.
- from Wil Milan ("Wil Milan"@ccm.ch.intel.com)
... [stuff deleted] ...
You also left out of your comparison that the mount which comes with the
ETX is a small tabletop tripod, which means one has to have a table or
other flat platform on which to set it. Unless one has already broght along
a solid table for some other reason, bringing a tripod for the Ranger is
a lot less trouble than bringing a table for the ETX.
... [stuff deleted] ...
- from Jeffrey R. Hapeman (jhapeman@students.wisc.edu)
Well, Jay, with the recent price inreases in the ETX, the spotter
version is very close in price to the Ranger (and the astro more
expensive). I have done side-by-side comparisons of the Ranger and the
ETX, and MUCH TO MY SURPRISE, the Ranger won out at all magnifications I
expected the extra aperture of the Meade to win out). To make the
comparisons fair, I used the same Meade series 4000 eyepieces in each
scope (but obviously not the same focal lengths--that would result in
unequal magnifications). When I tried to figure it out, I figured it
probably had to do with all of the following: 1)amount of unobstucted
aperture, 2) transmission of the glass (BK-7 for the ETX corrector, and
I believe BK-7 for the one element of the Ranger/Pronto doublet and of
course, ED for the other), 3) transmission of the coatings, and 5) the
reflectivity % of the two mirrors in the ETX (probably 86-89%). Overall,
with a little calculation, it's easily seen how the Ranger could have
won.
As for resolution--well that's easy to figure out. The Ranger won hands
down, very easily, using a standard resolution chart form Leica--no
central obstruction in the Ranger.
Finally--meow back--there isn't much plastic in the Ranger (except for
the cap and a set screw or two), whereas the Meade is at least 1/2
plastic. So, to me, the question is, which scope is a better long-term
value. I'd vote Ranger any day, even though I really like the Meade
otherwise--I have nothing against them and own many of their products.
Finally, the Ranger beat out a Questar--probably for the same reasons.
So now I'll reveal a bias--I sold my Questar as a result and bought a
Pronto (plus some great eyepieces and pocket change, to boot). I'm now
preparing for the flames of the Questar owners (and I too have a
hacksaw, but I never used it on my Questar).
- from harveym@fiendzone.demon.co.uk (Harvey Mace)
I want to buy one of these scopes and hoped to find some information
on the internet to help me make the choice, but so far I have found
contradictory reports, eg. in the review in Star Times
(http://www.mich.com/~bhalbroo/startimes6_96.html) the ETX gave better
resolution on a chart test, while a recent posting in this group
stated the Ranger was clearly better in this respect, etc.
[stuff deleted]
- from Jeffrey R. Hapeman (jhapeman@students.wisc.edu)
Harvey:
I totally agree with Jim's advice in every respect. See my post in
reply to Jay from earlier tonight. I know Bill Ferris, whose article on
the Ranger/ETX/Questar you referred to earlier. In fact, when he left
Eagle Optics, I took his place (I had to fund my hobby somehow, and I
was always in there buying something). Bill told me that other ETX's
(such as the one I looked through at Eagle, using the same charts,
eyepieces, etc. as Bill) that came in after that one (it was one of the
first, if not the first, we got in stock) did not and apparently
continue to not perform as well. I found the Ranger to be both brighter
and and sharper at any given magnification than the ETX. This was
especially noticeable at higher powers (around 200x)., where the Ranger
was considerably brighter.
Finally, having looked through many Meade (and Celestron) scopes, and
having star-tested numerous of the above and several Rangers and
Prontos, I must say that the Tele Vue products are VERY consistent in
their quality. With Meade or Celestron, you COULD get a real cherry of a
scope, but you also COULD get a real dog (I should know--my first 8" SCT
form Celestron was awful, the second is as close to perfect as any SCT
I've ever seen--lucky me!). With Tele Vue, I've only ever seen very good
optics or the very rare cherry (which is hard to tell from the "average"
Tele Vue Ranger/Pronto which would be "cherry" by Meade or Celestron
standards). Don't take this as a slam to Meade or Celestron--I own
scopes form both companies and love 'em, and also have many accessories
form both. It's just a fact of life--you usually pay more for the good
ones. What's so amazing about the Ranger is it's quality at such a low
price. Right now, there's no other scope that can compete with it in the
quality for the price market.
- from wdferris@aol.com
Harvey Mace wrote:
>does anyone really know which scope gives better images for high power
>work (x200+) using high quality eyepieces?
Your question really gets to the primary difference between the Ranger and
small aperture Mak-Casses like the ETX. The Ranger is designed to provide
low power, wide field views. Its focal length is 480mm. The Tele Vue
4.8mm Nagler, for instance, will give you a 100x view. You need to slap
on a 2x Barlow in order to get to 200x. At 200x, even a Nagler provides a
true field of view of only 0.41 degrees. An object centered at 200x will
drift outside the eyepiece field of view in 3 minutes. An extended object
like a planet will kiss the edge within about half that time.
The Ranger, an excellent wide field instrument, is not really at its best
at such high magnifications.
A longer focal length scope like the ETX is designed to get you in the
200x range more comfortably. Its focal length is 1250mm. The Nagler
4.8mm will give you 260x, the Nagler 7mm about 178x. No Barlow is needed
and this is important since very wide field eyepieces like the Naglers
already put a lot of glass between you and the object of interest. An
clock-driven equatorial mount is a valuable asset, if you plan to
regularly observe at mags in the 200x range. Clock drive lag
notwithstanding (see Sky & Tel's review in the January 1997 issue), the
ETX's motor drive is capable of keeping objects within the eyepiece field
at high power.
If you are looking for a scope that will be used regularly at 200x on the
Moon and planets, then the ETX has a definite advantage over the
Ranger--not an advantage in resolution, necessarily, but in oveall ease of
use.
* 2.9 How does the ETX compare to other instruments?
Here are some comparison found on the net:
- from R. Aguirre (ralpha@softcom.net)
Was wondering if anyone ever did a comparision on the Optical
similarieies between an ETX a C-5 and a GP-102 (non ED)
model. STRICTLY OPTICAL SIMILARIEIES WITHOUT TAKING INTO ACCOUNT
ANYTHHING HAVING TO DO WITH THE MOUNTS OR COST. My first thoughts
would be the Smaller ETX would be good, the GP-C102 would be better,
and the C-5 would be best for planetary views. I've never looks thru
a C-5, but I have seen an ETX on saturn using a 7mm Nagler and it was
razor sharp, as was Jupiter. Conditions were under dark clear moonless
skies. Thats about 180x. I've peeked thru a GP-C102 using the 7mm
also and it was also fantastic at about 150x. Can the design of the
ETX really hold a sharp focus out to 250 to 300x? Seems to be the
claims of some non-ETX users? I suspect not but I dont know? How about
the GP-C102? I figured it would be spent at about 200x. How about the
C-5? I am just not to impressed with small Schmidts but this is only
based on what I have seen in, for example, the Celestron Catalogs?
Basically, i'd assume they would all be similar in overall performance
for planetary sharpness though I'd guess the C-5 would win the limited
Deep space contest. What makes the ETX design so impressive for
planetary observing. Based on advertisements ( which I seldom believe
with out first hand experience), shouldnt the ETX then be the star
performer in this group in overall optical sharpness and performance.
Or, shouldnt the refractor win the sharpness contest? If being
somewhat similar in aperatures size or focal lenghts, could anyone
really tell a difference? Now lets throw in a star performer, the AP
102 traverler. Why can this scope make claims to remain razor sharp at
and above 300X. My guess is that this one would vaporize the ETX,
GP-C102 and C-5 in every catagory? I've looked thru a traveler with
the same 7mm eyepiece and a 3x televue barlow and was not impressed
with the sharpness on both Jupiter and saturn. Looks like the 260x was
over extending the upper limits of this scope, though probablly at
200x it would have been pretty nice. Having a large and heavy 10"
Schmidt, I've been searching for a smaller light scope for quick 1 hr
sessions in my back yard at a moments notice or for ultra portability.
In order of appeal to me considering all factors, cost, mounts etc, My
current direction is C-5, ETX, GPC-102 and Traveler. The traveler is
definately the most desired, but the cost is pretty steep for a little
scope. For some reason, I am just not attracted to any of the televue
refractors, to me, the Traveler has that market covered completely.
- from Loren A. Busch (busch@ix.netcom.com)
Ralph
I own both an ETX and a C5+. For ANY application (without considering
the small size of the ETX) or viewing the C5+ outperforms the ETX. I
base this on extensive testing this last summer setting the two scopes
side by side and using the exact same eypieces in both.
This is not suprising considering the additional aperature on the C5.
There is no comparison on the drive bases. The C5 is supurb, the drive
base /fork mount for the ETX sucks. I have removed my ETX from the
fork mount and use it on a good tripod.
Optically, based on the ETX scopes I have seen, they are a very good
buy, excellent value for the dollar. The optics star test better than
anything in the price range and better than a lot of products that sell
for much more. But if you want a very portable scope of superb
performance and can stand the additional size (and price) of the C5+ it
is a better choice.
(I actually have two ETX'x: one the astro mount, one the spotter. I
have them mounted together as a fantastic binocular)
- from Donald Tabbutt (DonTabbutt@worldnet.att.net)
Hello Ralph,
I have an ETX that I bought mainly for travel. However, I think it may make
a nice guide scope for my 8" f/10 LX200 and I have ordered the Losmandy
stuff to mount it. In the meantime, I used its tripod block to piggyback it
on the LX200 last Sunday night for an A-B comparison. The short conclusion:
there is no comparison; the ETX is a little scope and the 8" SCT is a
comparatively big scope. The most striking and immediate difference is
brightness. One plus to the ETX, though, is when focused on Capella it
forms a perfect Airy disk with a single small diffraction ring...something
I've never seen in the SCT, although it appears to focus as well...but no
diffraction ring.
Saturn was jumping around in the LX200 like I had lost "vertical hold", but
was O.K. in the ETX...I guess proving small scopes handle bad seeing better
than big scopes. On Christmas night I used the ETX by itself on Saturn and
could see banding at 187X with just a hint of Cassini's division as a
contrast change in the rings. But I couldn't see Tethys or Dione...just too
dim. I see them regularly in the SCT. In short, I couldn't do an A-B on
Saturn because of the seeing Sunday, but have had much better views in the
SCT in the past. I even imaged the ammonia cloud storms on Saturn with a
CCD camera last October through the SCT, and got images nearly as good as
those published by Donald Parker in S&T's December issue. Until I read that
issue, I thought the storms were some sort of image processing artifact.
With averted vision Christmas night, I think I saw those storms through the
ETX. They appear visually as ragged edges on the south side of the south
equatorial band.
On the deep space side there is really no comparison. One caveat...there is
a lot of light pollution here, and I will have to do another comparison at
a dark site. I put a .63 reducer on the SCT to even up the magnifications
(about 48X) using the standard 26mm Plossl on both scopes. I looked at NGC
1857, a small cluster in Auriga mentioned recently on s.a.a. (they were
having trouble seeing it through a Ranger), and saw it clearly and brightly
in the SCT, but barely in the ETX. The same goes for other small clusters.
They are there, but dim compared to the SCT. I used an O III filter on both
scopes for M76 and NGC 7662 and saw them in the SCT (without the reducer)
but not at all in the ETX. M31 was fine in both scopes, but M33 did not
show up in the ETX (light pollution, I'm sure). Later, as M42 cleared the
trees, it was nicely visible in both scopes, but again much brighter and
more finely detailed in the 8". I couldn't see NGC 2024 in either scope. I
didn't try splitting any doubles.
By now, the Moon was rising, and after it cleared the trees I used all
kinds of powers to look at it...up to 300X on the SCT and 187X on the ETX.
Bad seeing caused me to back off, but I'd call it a draw on the Moon. Both
scopes were clear, tack sharp, and very contrasty, with the same small
details equally visible. Again, the SCT was brighter, but at lower powers I
have to use an ND filter with it. The ETX was fine without a filter.
In summary, aperture wins. The ETX meets my needs as a traveling companion
and will probably make a good guide scope. The optics, in my experience,
are superb, but it will not outperform a larger aperture scope with decent
optics. The ETX mount is a different story I'll save for another post if
anyone is interested.
I hope this helps answer some of your questions.
- from Allen Chan ( chana@andr.UB.com )
i brought the etx to a telescope shop to compare it with a C5. the
shop had a TV pronto, so i compared this scope also. the salesman was
the official second opinion in this comparison.
first, we normalized the comparison by setting the three scopes to the
same magnification. since the C5 has the same focal length as the ETX,
we use the same type of eye piece in the C5. the pronto need a much
high mag eye piece.
we look at a gargoyle on the across the street. specifically, we
looked into the dark mouth of the gargoyle to simulate low light
conditions.
the ETX was noticeable sharper than the C5, but the C5 was brighter.
the pronto was a used scope and the image did not seem as clear as
either mirrored scopes, so i started to ignore it. the ETX gave a
cooler blue-ish tint to the image while the C5 gave a warmer yellowish
tint.
the salesman also thought that the ETX gave a sharper image that the
C5. however, these test were done in daylight conditions. in night
time astromony conditions, the larger mirror of the C5 might have a
greater effect. for daytime conditions, the ETX won the comparison.
* 2.10 Do I need a perfectly level surface for doing the polar alignment?
Here is a thread found in sci.astro.amateur:
This is a common misconception. For polar alignment, all that is necessary
is that the RA axis [the ETX fork arms in this case] have to point to the
pole. It doesn't matter one bit whether or not the table is level. A level
surface makes alignment easier, but it is not essential.
and the following:
In article (824@portugal.win-uk.net),
Jonathan Silverlight (jsilver@portugal.win-uk.net) wrote:
>I don't see how this works. If a polar mount is aimed at the pole
>but isn't level it must be offset E or W and will drift
>accordingly.
Jonathan,
If a polar mount is aimed at the pole, as you stated, (ie. the mount's
polar axis is aligned with the Earth's rotational axis), then the
attitude of the tripod is totally irrelevent. The important thing to keep
in mind here, is that if the polar axis of the mount is properly aligned,
you can forget about what's holding it up (ie. the tripod, pedestal,
whatever...). However, it *is* more difficult to achieve a polar
alignment using the "drift method" if your tripod is poorly leveled to
begin with.
* 2.11 Can the ETX be a first scope for a novice?
The answer to this question is not simple ;-)
One easy answer is yes, every telescope can be a first scope for a beginner!
here are some articles:
- from Cliff Newman (cnewman@inforamp.net)
> I can't agree with this. The ETX is **NOT** a "beginner scope", any more
> than a Questar is.
Yes it is and I'll tell you why: people will buy this AND use it for the
same reason they buy those cheap dept. store scopes: it looks like a
telescope, it's really portable, and it is great for all the things that
newbies (like me) want to look at. There is a lot of very good advice
offered here and elsewhere telling new observers to stick with
binoculars. This advice, while sound, will fall on deaf ears because new
observers don't want to use binoculars; they want to look through a
telescope. The ETX looks not just like a telescope but a high tech
telescope. That's why it's going to become the best selling telescope in
the world over the next few years (at least according to one experienced
observer at a star party who got his first look through my ETX). And if
you don't stick with astronomy you've got a killer terrestrial scope
too.
In my admittedly untutored view, what makes a really good "2nd" scope is
a 10" Dob. I'll likely keep my ETX and move up to something like that
that I can set up at my cottage and use it whenever conditions warrant.
When I have to drive or fly someplace, I'll take the ETX.
Cliff
> A good 6" dob is roughly the same price (or slightly cheaper) and HUGELY
> better as a first telescope than an ETX would be.
>
> Chris
>
> ----------------------------------------------------------------
> Chris Marriott, SkyMap Software, U.K. e-mail: chris@skymap.com
> Creators of fine astronomy software for Windows.
> For full details, visit our web site at http://www.skymap.com
- from ??? overfall@ixl.net (Leander)
>...snipped...
>Unless you live in a very dark site, I predict that you will not use your 8
>inch SCT nearly as much at home once you get your ETX. I know that I use my 3
>inch refractor at home much more often than my 10 inch dob. By the same token
>I use my 10 inch much more often from my dark sky site.
>P.S. Aperture always wins, but there are wonderful objects to observe through
>any sized aperture from naked eye to world class observatory giants.
Very good point.
A lot of discussion has been ongoing on this thread about the
advantages of larger scopes vs smaller scopes, with some valid
points made by all. The usual recommendation for newcomers is to get
a 6" or 8" dobsonian. Practically, however, this may not suit all
buyers' needs.
I think we have a tendency to forget that the needs of an
individual newcomer may not fit with our standard recommendations.
Do they live in an apartment. Are they in a dark or a
light-polluted area? How much weight do they want to or are able to
carry? Do they want to take out their scope in one piece, or in
several pieces and set it up each night? How much time do they have
for an average observing session? What are their interests
ultimately, as well as immediately; do they hope to do
astrophography, ccd astronomy, or visual only; planetary, deep sky
or both? Comet hunting sometimes or primarily? Don't know yet? Do
they know how to collimate or want to learn collimation? Will they
be travelling by plane a lot?
For many, the standard dobsonian may not be the best choice. A
small refractor such as the Celestron 80mm or the Pronto or the
Ranger on a decent mount may be better, and get used more; so might
a small sct-type such as the C5+ or the new Meade. For some, even
the lowly Astroscan may be the best choice. A C4.5 Newtonian might
be better than a 6" dobs for many people. Or the dobs may be
perfect.
Rather than dealing with personal prejudices and preferences, we
could better aid newcomers by addressing THEIR needs, not our needs
foisted upon them.
Big aperture is great to view through, and usually involves a
scope which is a pain to set up, especially when you are tired or
have limited time.
Portability still gets a scope which will see all the Messiers,
planets, and a good number of other items. If the scope can be
carried out in one trip, set down, and begin looking, it will be
used often. If people travel and want to bring their scope, a small
one will get used while the big one stays home.
Instead of buying the biggest aperture they can afford first, then
wishing they had an easier to use portable, why not introduce
them to the skies with a portable, then when they are comfortable
with all they can see with this scope, get a light-bucket to see
even more, with less confusion.
Probably the one critical question is, do they want to do
astrophotography? Well, then they will need a motorized equatorial
mount; but they may still want to start with an alt-az, and upgrade
later to a heavier motorized mount which will have to be
polar-aligned (adding to set-up time), and may now involve multiple
trips for set-up.
We have a portable, a light-bucket, and binoculars, and the
light-bucket gets used the least because of its 20minute set-up and
total 90-pounds weight in 3 trips. Also, our viewing since moving to
a light-polluted area is not as good, so the smaller Pronto actually
does much better. Some nights, there is only enough time for a quick
binocular view before the clouds roll in (1996 was SUCH a great
viewing year...not).
These are my opinions, and not everyone will agree. But I've
gotten a number of family and friends into astronomy over the years,
and did not recommend the same scope for all of them, because of the
above considerations. Of note, though, they are all still using
their telescopes, which is, after all, the only true ideal.
- from Mark S. Cronan
Chris Marriott (chris@chrism.demon.co.uk) wrote:
>with respect, Cliff, the fact that you've bought it (and lots of other
>people will too) doesn't make it a good beginner's telescope. You can't
>defeat the laws of physics - at the end of the day it IS only a 90mm
>telescope which imposes SEVERE limits on its usefulness for astronomy.
>Even a cheap 6" Dob is going to show far, far more objects than your ETX
>will.
>The ETX is a *great* portable telescope - I've got one on order myself!
>- but I stand by my conviction that it is NOT a good "general purpose"
>telescope for the novice amateur astronomer.
Well Chris, I've got to disagree. For some reason you think a "general
purpose" scope is what a beginner needs. You stress, in fact, the
number of objects that can be seen. I don't think thats the
appropriate criteria to judge a beginners scope. What a beginner
needs is 1) Something simple to use. The ETX is simple to use, since
it requires no real collmination every time you use it, and comes with
alt/azimuth mounting system and tracking motor. 2) Something which
will show you the "major" things to be seen. The ETX will show you
pretty much any Messier object. It won't get you the horsehead nebula,
but then a beginner should not be going after the horsehead nebula to
start with. A beginner will instead be using, probably, a beginners
book of objects. Such a book will list items which the ETX should be
able to view without too much trouble. It will also get you good
views of the planets, moon, and sun (with a filter). So, while it is
not a "general purpose" scope, it is a "general beginners" scope,
IMHO.
* 2.12 Meade advertises a resolution of 1.3", is it true?
There are several report claiming such a result, here are two:
- from andromed@atm.dal.ca (Michael Boschat)
Michael Boschat ( Astronomer ) E-mail: andromed@atm.dal.ca
Atmospheric Sciences Phone: (902) 494-7060
Dept. of Oceanography FAX: (902) 494-2885
Dalhousie University
Halifax, Nova Scotia
CANADA, B3H 4J1 ASTRONOMY Web Page: http://www.atm.dal.ca/~andromed
Date: Aug.5/6
Time: 0120 UT
Location: Halifax, Nova Scotia, CANADA
Lat: N44
Long: 63W
Limiting magnitude (visual): 4.5
Seeing (1 to 5 - best to worst): 2
Instrument: ETX Spotting Scope 90 mm Makustov, f/13.8, 48x, 167x, 312x
Object: The double star Xi Ursa Majoris, Jupiter, Comet Hale-Bopp
Well, it stayed clear and I had a nice Airy Disk, so I went after
the theoretically resolving limit of the ETX which is 1.3 arc seconds.
The double star Xi Ursa Majoris according to the books is 1.3 arc seconds
with companions of 4.3 and 4.8.
So with 312x I focused on Arcturus till I got the Airy Disk, then doing
some manouvering with the finder..ugghhh... I found Xi. Lo and Behold
it was seen as 2 stars touching!!!!!!!!!!!! Gezzz...!!! I let out...
It looked like this at 312x;
(*)
(*) /N
the () is the Airy Disk |_ E
So, it was seen without any problems....except for one that I just
came across, I have slight mirror shift. When I wen back to Arcturus
I had to re-focus a bit, so I will assume slight mirror movement.
But, the ETX split to it's limit! I am amazed.
Date and UT of observation: Aug.11/12, 1996
Location & latitude: Halifax, Nova Scotia, CANADA, 44N 63W
Limiting magnitude (visual): 5.5
Seeing (1 to 5 - best to worst): 2.5 - 3
Instrument: 90 mm Makustov, f/13.8
Magnification: 48x, 167x, 208x, 312x
Object: Eta Corona Borealis
Category: Close double star of 1 arc second
Description:
Using the ETX focused on Epsilon Bootes at 312x to get the best possible image
I then moved to Eta Corona Borealis. It appeared at moments of steady
seeing as a small elongation. This shows that the ETX seems to be able
resolution of near 1 arc second on excellent nights! I was amazed to see
the slight elongation in a North East ( since the image is reversed )
direction. The components are 5.6 and 5.9 magnitude.
Again the ETX, despite falling apart is showing it's performance in the
optics!
3. What kind of accessories can I used on my ETX?
* 3.1 Which tripod can I used?
Chuck Faranda ( chuckfa@ix.netcom.com )
I use a Bogen 3001 and have had good results, it's both sturdy and
portable.
* 3.2 Which cases/bags can I used?
Meade ETX bag is too large and poorly designed. Many people find video
camera bags to be much better and less expensive.
* 3.3 Which eyepieces can I used?
ETX is slightly different in it's construction than most scopes. You
may find that certain wide angle eps have an obstruction in the field
of view where the edge of the mirror is. I think that you would do
well trying to complete a set of eps that is parfocal. Otherwise you
will be adjusting focus, sometimes quite substantially. This can be a
pain. In my severely limited experience I found that long eye relief
eyepieces were extremely sensitive to the eye being aligned with the
optical axis of the eyepiece, causing me to lose the view even with
slightest movement of the head. The bottom line is TEST EACH EYEPIECE
BEFORE BUYING! Most stores have no problem with you bringing your ETX
into the store to try an eyepiece. Star Parties are great for
comparing eyepieces as well. I tested some highly acclaimed eps and
found them unusable on my ETX.
get from metxug
- from Fred Smith ( fsmith@wage.cyberspace.com )
I bought a 9mm Nagler to use with it, but I found the image to be not
at all sharp - at least compared to the 26mm super plossl that came
stock. BTW, the 15mm Panoptic was wonderfully sharp on it.
- from Chuck Faranda ( chuckfa@ix.netcom.com )
Hi Fred,
I just got my ETX last week, so far it's great. I've used it with the
26mm Plossl and a 15mm Teleview with fine results.
There isn't any collmination adjustments on the scope, so you'll just
have to trust Meade's QA program, my scope was very well aligned. I
think your problem with the 9mm Nagler may center on the fact that you
are approaching magnification of 40 per inch of aperature. So the
image may show signs of degradation. You may want to try the Nagler
under dark, clear, steady skies and reevaluate the results. The
quality of an image under high magnification (138X in a 3.5" can be
considered high by some standards)in any scope is dependnat upon
seeing conditions.
- from Alvin Huey ( huey@wheel.dcn.davis.ca.us )
I have used it with a 9mm Nagler, but my views are wonderfully
sharp. I actually did the star test with the 9mm Nagler, and it turned
out very well. Jupiter was sharp with the 9mm Nagler. I also used my
13mm Nagler with it and it worked out well also. Didn't try my 16mm
Nagler yet, since I have a 15mm Ultrascopic, which I bought for this
scope. Of course couldn't use my 20mm Nagler and 35mm Panoptic. (Wish
I could...) About the tight fit with the finder, I fits but it rubs
against the finder holder. I plan to take the finder out and put some
kind of 1 power finder on it. Any suggestions, I'm a big Telrad user,
I have one on each of my other three scopes.
- from steve (steves@flinet.com)
> I recently compaired the 26mmSP that I got with my
> LX200 with the one I got with my ETX. There is a
> !/4" difference in length. One is 2 3/4" long and the other
> is 3" long. I'm not sure which one came with what.
> I thought the two eyepieces were the same but they
> aren't even parfocal to each other.
>
> Does anyone know what gives here?
>
> Jim
Jim;
This is what the ETX manual says (in my words);
"The 26mm Super Plossel that comes with the ETX is a special "low
profile" version. It is optically identical to the standard model, just
shorter for a lower profile on the scope. It is not going to be
parfocal with the regular Meade SP line."
* 3.4 Which barlow lenses can I used?
I use TeleView x2 and it provides me with satisfactory service,
especially with the 26mm ep. I have an 8mm ep and with that Barlow it
is at the edge of usability, but Saturn looked quite decent.
- from J HOPPER (JHopper@prodigy.com)
I used a TV 2.5x Barlow with the 26mm on my kids' ETX, and it was
excellent. The downside is that it's awfully stupid-looking, sticking
way up. Ruins the whole "low-profile 26mm" concept. You also have to
be careful not to slam the Barlow into the diagonal, there's nothing
to stop it. I don't think they make the 2.5x or 1.8x anymore, now
having 2x and 3x. No idea if they're just renamed or what. Barlows'
power varies anyway depending how you use them. If you can get a
used, mint one for $50 like I did you're doing well, I'd say.
Don't think I tried it with my 15mm TV on the ETX, but that combo also
worked OK on my 7", though not as well as the 26mm. Perhaps because
on the 7" that's awfully high power for mediocre seeing.
* 3.5 Someone told me that using a Barlow on the ETX will give a too dark image?
Too dark for what? For faint nebulae yes, for Venus or Moon no. ETX is
a small scope so almost anything can overpower it. Keep in mind that
many of us are used to NASA space probe fly by pictures or Hubble
space telescope shots and sometimes we intuitively expect similar
pictures in our eyepiece. The truth is that in most cases no Earth
based telescope regardless of size can give us that kind of detail and
clarity as the space shots made with CCDs, to not even mention our
poor ETX.
4. What possible mechanical modifications/enhancements can I make on my ETX?
Get yourself a solar filter - that will extend your viewing time to
daytime and give you more fun. Tuthill told me that he is coming up
with a 90 degree viewfinder. For me this would be a must! Some kind
of a due cap is also useful. One should be able to make one easily
with black fabric and velcro. Tuthill also offers a camera piggy
back mount, which allows one to use the lousy clock drive of the ETX
to take long exposures with one's camera. Meade of course offers
camera attachments to use ETX as a lens. I know that some people tried
CCD cameras with success. But good CCDs cost much more than few ETXs
put together.
and also check at http://metxug.elendil.com/extfix1.html for the
Declination Control Fix.
* 4.1 Can I computerized the ETX? (goto function)
Lets remember why we bought an ETX - small, inexpensive, easy to use.
With computer it becomes complicated, hard to set up, unreliable and
expensive. But if you really want to do this, JMI has the set up for
you ranging from $399 to $699 with their installation. Call them at
800-247-0304 or outside of USA at 303-233-5353, fax 303-233-5359.They
take plastic.
5. Contributors
Many thanks to Jurek Zarzycki (jurek@apple.com) who gave me lots of inputs.
END OF FAQ#################
###########################
FUTURE EVOLUTION TO BE DONE:
NEW ENTRIES:
FINDER
------
I find the finder scope to be almost worthless, given its position on the
OTA. I think I would like to replace it with a small unit finder. Any
recommendations?
COLLIMATION ADJUSTMENT
----------------------
Finally, am I correct in believing that there are no "user correctable"
collimation issues with a Mak such as the ETX? I have read from many
postings that the optics on the ETX are potentially excellent, when Meade
quality control passes muster. What is the recommended way for a novice
to judge the optical quality?
(Is that true, about no collimation screws. I thought that the three hidden
hax screws in the plastic mirror mount is it, even tough they my not be evenly
spaced.) Read the S&T May '95? Issue about star testing, or try Suiter's book "Star
Testing Astromical Telescopes.
MISC COMMENTS
-------------
Luis Arg|elles wrote:
>
> I'm in the process to purchase my first scope and I wonder if this is a
> good scope.
I've had one for seven months but haven't used it much since last Fall,
given the rotten weather arond Toronto this winter. Finally got out this
week on a so-so night and remembered what it is I like about the ETX.
>
> #1.: Portability
The whole works fits into a bag about the size of a smallish camera bag
and weighs about 15 lbs. I use a Manfrotto 144 tripod which increases
the load by 50% or so.
> #1.: Quality optics
Definitely. As luck would have it another chap showed up with a Pronto
(that's the one with the 2" focuser, right?) and we agreed that he had
slightly more contrast than I had but image quality was otherwise not
very different and his scope cost about twice what mine did. I also had
the advantage in being able to apply more magnification (a dim and shaky
image of Mars at 250x, but then it wasn't great seeing). I hadn't polar
aligned very well, so keeping Mars in the eyepiece was a frustration;
but then the Pronto had no clock drive at all.
One thing I learned: an experienced observer with an LX200 on an
equatorial mount, had Mars at 100x at the same time as me. His image was
a lot brighter than mine, so bright he put in filters to dim it down. At
200x he couldn't get an acceptable image either due to conditions. So on
an average or below average night I don't see any huge advantage to the
bigger scope - although I'd kill for his drive.
> #3.: Easy operation
The biggest advantage to the other scopes, especially the LX200 was the
size of the controls. The tiny focusing knob on the ETX makes focusing
kind of fiddly and nearly impossible with gloves. Otherwise, it's a
really easy scope to use and if you take the time to polar align
properly the clock drive will keep an object in the eyepiece long enough
for a good, hands-off, no shake look. BTW, I don't think the finder
scope is totally useless, as some have suggested, but I did add an Orion
EZ Finder 1x finder and that helps in polar aligning and most other
searching that I've attempted so far.
#4.: Very basic astrophotography
No joy here I'm afraid. I've taken some moon shots but that's about it I
would think: star trails of course, but the clock drive is not up to
keeping an object centred beyond a few seconds or tens of seconds. Even
getting an object centred and then waiting for the backlash to take up
(and that does seem to take 20-40 seconds) will see the object half way
out of the field of view.
> I would like to hear your opinions.
It's a really good little scope for visual observing. One of the nicest
things about it is the comments from experienced observers: they nearly
all love the image and are impressed with the performance. You can buy
more aperture for the same money but you can't take those scopes on a
plane with you and you likely won't want to haul them too far by bus
either. I don't suppose I'll be in love with this scope forever,
although I've kept my first wife for over 30 years, so who knows?
Hope this helps.
Cliff
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