Last updated: 30 September 2007

Subject:	1.25" to 2" adapter review
Sent:	Sunday, September 30, 2007 16:37:50
From:	Lee Vincent (
Adapting to the Big Picture
Lee Vincent

For me, the whole point of having a telescope is to see bigger and
better views of the universe.  So it's no surprise that I'm always
looking for a wider angle 1.25" eyepiece for my ETX-125.

The 1.25" 26mm eyepiece that came with this scope provides a 0.82 degree
field of view (FOV) at 73x.  In order to get a bigger, better view, I
purchased a 40mm Plossl that modestly broadened the FOV to 0.92, but
reduced the magnification to 48x.

This was somewhat of an improvement, but I still wasn't completely
satisfied, so an ad I saw recently in Astromart really caught my
attention.  It was placed by CNC Supply, Inc. and read as follows:

"This 2" ETX eyepiece adapter can really open up your view. The results
are remarkable. Works well even with wide field 40mm eyepieces. Anodized
aluminum construction with a brass compression ring to prevent marring
eyepiece barrels. Threaded for 1.25" eyepiece filters.

"Important Note: This adapter requires a fair amount of back focus and
is only recommended for catadioptric telescopes with a moving mirror
focus system, will not work with most reflectors or refractor. Not for
ETX60/70/80 due to lack of back focus."

This sounded intriguing.  With this adaptor in my ETX, I could use my 2"
ultra wide angle eyepieces in order to increase the field of view by as
much as 50% or even more in some cases without reducing the

The $49 price tag seemed a bit steep for this little item, so I thought
I'd check out  I've done business in the past with
Manish at Agena and found him to be nothing short of a class act.  His
prices always seem to be competitive, so I was not surprised to find
what appeared to be a similar adapter for $20 shipped to my door.

For 20 bucks, it might be worth a try, but before I placed my order, I
checked out Mike Weasner's ETX  Mike's site
has an abundance of information related to the ETX, but didn't have any
reviews on this adapter.  Mike did tell me, though, that he would be
concerned about vignetting and balance problems.

Vignetting was one of my concerns as well, but I had already tried
hand-holding a couple 2" ultra wide angle eyepiece's--very nice, sharp,
wide angle views right to the edge.  In fact, my 26mm Orion Q70 has a
slightly wider FOV than my 1.25" Meade 40mm eyepiece.

Though Mike's website did not have any reviews on an adapter of this
sort, it did have an article by Chris Brown dated December 17, 2005. 
Chris attached a 1.25" barrel to an inexpensive 2" Erfle and was pleased
with the results when used in his ETX-90.   "Achieving focus was not a
problem, nor was the weight of the eyepiece, due to its lightweight
construction."  My larger ETX-125 then should be able to handle a
somewhat heavier eyepiece even with the added weight of the adapter.

I cautiously tested the eyepieces but was not terribly concerned about
weight since my 1.25" 6.7mm Meade UWA eyepiece weighs about the same as
my 2" 26mm Orion Q70.  I've never had any problem with the weight of my
6.7mm UWA, however the heaviest 2" eyepiece I have is about 7 oz more.

So far, I've tried the following 2" eyepieces:

1.	30mm Wollensak -- weight: 19.2 oz; length: 114mm
2.	32mm Orion Q70 -- weight: 14.4 oz (+/-);  length: 120 mm (+/-)
3.	26mm Orion Q70  weight: 11.9 oz (+/-); length: 103mm (+/-)
4.	15mm Knight Owl -- weight: 9.2 oz; length: 80mm

My results were as follows:

Vignetting:  No vignetting with any of these eyepieces.  Just a nice
sharp edge.

Focusing:  No problems at all.

Balance:  This scope is nose heavy anyway, so even the heaviest of these
eyepieces could only help to balance the scope.

It should be noted that I did not do any extensive testing with the
scope in the Equatorial/Polar mode.  I did briefly put the scope in
Equatorial/Polar mode (about 42 degrees) with the heaviest eyepiece to
see what would happen.  I can't imagine that there would be much risk of
even the heaviest eyepiece toppling things.

Slewing:  I realize it's not very scientific, but I'm just basing my
conclusions here on sight and sound.  When I slewed the scope at various
speeds, I did not notice any hesitation nor did the motors sound as if
they were straining at all.

I think I may have to qualify this though.  Let's be honest, these
drives are not quiet to begin with.  In fact they sound very much like
dueling coffee grinders and didn't sound any better or worse with even
the heaviest eyepiece.

If you're concerned about auto-slewing with a long, heavy eyepiece
sticking out of the scope, you can always remove the eyepiece and then
replace it when the slewing stops.

You definitely need to be a bit more careful when aiming at or near the
zenith, but there still seems to be plenty of clearance.

Fit:  I was surprised to see that the adapter seems very stable even
with the longest, heaviest eyepiecenice snug fit without any wobble.

Leverage:  I would be careful at star parties.  Sometimes people want to
hang onto the eyepiece as if it were a handlebar.  With the additional
length/leverage of a 2" eyepiece plus adapter, there could be a problem

Conclusion:  Overall, I'm very pleasethrilled in fact.  For 20 bucks,
I'm able to significantly broaden the view through my ETX 125.  Without
this adapter, I would never even dream of turning my scope to the double
cluster (NGC 869 and NGC 884) and expect to see both in the same
fieldone or the other, but not both.  With this nifty little adapter and
an ultra-wide-angle eyepiece, the pair just fit neatly within the field
of view.  I'm now enjoying a much bigger picture of the universe.




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Copyright ©2007 Michael L. Weasner /
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