Last updated: 28 August 2005
This page documents astrophotography comments, tips, and photos. Contributions welcome. Be certain to see the other articles on the main Astrophotography page.
Subject: ETX 125 guided astro-photo at prime focus Sent: Friday, August 26, 2005 23:44:37 From: Fernando Campuzano (email@example.com) I've recently purchased a digital SLR camera and would like to use it with ETX 125 at prime focus. Instead of Meade 64 T-adapter, I'm unsuccesfully seeking for an off-axis guider similar to Meade #777 for the LX-series, but for the ETX. I've heard about an adapter for the ETX to match accesories for the LX (a Scopetronix model) but didn't find it in any Internet site with shipping in Europe. Could you help me? Do you know some other alternative? or, a good Internet site with shipping in Europe? Thanks in advance Fernando Guadalajara, SpainMike here: What you are looking for is a SCT Accessory Adapter; see the Accessory Reviews: Miscellaneous page. However, three things to keep in mind: 1) the extra weight will require a counterweight to be used, and 2) when in Alt/Az there will be field rotation for long exposures, and 3) when in Alt/Az the forks and base will prevent you from going near the Zenith.
Subject: City astronomy Sent: Tuesday, August 16, 2005 09:01:56 From: Mike Lewis (firstname.lastname@example.org) Your website is valuable. I used it when first setting up to do astrophotography. I'd like to share a photo with you. My small downtown Seattle apartment has only one northern window and the view is about 60d altitude and 30d azimuth. Astrophotography is rewarding, though and a great deal of fun. This photo came out fairly well. The problem of getting rid of glare is the worst. PhotoImpact's Tone Map is excellent for eliminating background noise (and most faint stars) but keeps some visible. I used to go up to Table Mountain or other places but the hassle of setting up for only one or two night's work is awful -- home limits the sky but the elaborate events that need to take place can be in a stable place. JPG's of both the original and the adjusted images are shown. The original was an 11Mb 2272x1768 TIF file. It is not mentioned in the photo that, besides Tone and Gamma adjustments, an unsharp mask was used on the three RGB channels. Next time, the CMYK channels as well. Adjusting gamma on the CMYK images is iffy, there is no good measure and these images are all much different.
Michael Lewis Seattle Postscript: Forgot to mention the photo of Errai was one eight-second exposure at f:2.6.
Subject: Question about dual axis drives for astrophotography -not spamm Sent: Thursday, August 11, 2005 18:58:52 From: John Dooley (email@example.com) Sure like the cool site on the Oracle Observatory, and good luck with any pictures of the meteor storm tonight!!! Mike, I've been toying with ideas for a decent dual axis motorized mount since I picked up a Canon 20D (unfortunately not the 20Da model!!!) and after a fair search have only been able to come up with sellers for these in Canada, UK and Australia. Do you know of anyone who has utilized them for astrophtography and/or a source for one in the 100-200 dollar range??? I have my ETX125ec with a Scopetronix piggy back mount, but dont really have a good enough system set up to transport my scope out to favorable areas and also have not yet invested in a better tripod to support polar alignments. - I did get smart after purchasing my scope a few years ago and sent it directly to Dr. Clay for the Supercharge. Still wish I could have taken advantage of the eyepiece deal when it was so popular, alas!!! poor timing. Anyways, fine business on your Nikon and always looking for news of your travels back from Arizona. Good job packing that little car Mike!!! Wheres the iPod???? John Dooley Victorville, CAMike here: I seem to recall an article in Sky and Telescope some years back about such systems. But I don't remember the details. As to the iPod, check out the frame in the packing movie that shows the front seat loaded; near the center you will see the iPod mini mounted on a Belkin "TuneBase FM for iPod mini".
Subject: etx focal reducer, eyepiece port Sent: Wednesday, August 10, 2005 14:15:40 From: A. Sidney Johnston (ASJ@c-m.com) I have been searching vendor pages for a focal reducer for my ETX 125, where the focal reducer fits into the eyepiece port. I want to use the Meade Deep Sky IMager with a wider filed of view, which the focal reducer shuld provide. Meade has two models, a 2x and a 3x, both advertised as "reducer correctors", which screw onto the back of the telescope, and then hit the fork base if one goes to high DEC. Do you know of any vendor who sells a focal reducer, preferably a reducer corrector, which fits into the ETX eyepiece?? Thanks Sid JohnstonMike here: The Shutan Wide-Field Adapter can be used in the eyepiece hole, as I report on the Accessory Reviews: Showcase Products page.
Thanks for your prompt reply. I had seen your write up about the Shutan wide field adapter. However, I wondered why it is necessary to buy a prism when all that is needed is an in-line device to converge the rays. Perhaps the range of focusing of the ETX is not great enough to properly place the prime focus behind a converging lens of the focal reducer, when the focal reducer is placed in the eyepiece port. Do you think that a design limitation may be why Meade has two models of focal reducer for the in-line rear port, but none for the eyepiece port of the ETX?? Thanks SidMike here: Could be.
I just ordered a focal reducer which screws into the filter threads of either a ccd camera or an eyepiece. I ordered from the link http://webcaddy.com.au/astro/adapter.htm, and I ordered both the lens and the extender tube. If you are interested, I will let you know how it works. Sid Johnston
Subject: Stacked image Anomaly Sent: Wednesday, August 10, 2005 02:42:27 From: C.A.Warburton (C.A.Warburton@lboro.ac.uk) My most recent and best shots of Jupiter ( the AVI's were taken a couple of months ago ) seem to exibit striations accross the image. The Avi's were stacked in Registax and whichever version I use seems to produce the same effect. This unfortunately limits the amount of enhancement I can use as the lines accross the image are enhanced as well. Do you know if any one else has had this problem and if so is there a way of fixing this? I've attached a slightly over enhanced image as an example.Mike here: Stacking isn't the cure for everything. Consider what you overlaying: pixels. Ever look through two window screens or two wire meshes that are superimposed? You will see patterns. This likely what is going on here. You may be enlarging before stacking, which enlarges the pixels. If possible, stack smaller versions of the images and see what happens.
Many thanks Mike, Kind regards, Chris Warburton, Derbyshire U.K.
Subject: Removing "hot pixels" Sent: Saturday, July 30, 2005 23:26:54 From: Tom and Lori (firstname.lastname@example.org) I found a great free program that removed the "Hot Pixels" on your dark digital photography photos. This works well. The name of the program is HotPixels. There is also a great filter simulator that simulates different Wratten filters. Here are the links: http://www.mediachance.com/digicam/hotpixels.htm http://www.mediachance.com/digicam/filtersim.htm Clear skies, Tom
Subject: learning to scale images questions Sent: Saturday, July 23, 2005 20:54:02 From: Steve Dang (email@example.com) Im trying to learn how to scale my images and I have a couple of questions about reducers. Wondering whether you could help me. Attached is a picture of the moon , features of crater plato and vallis alpes. I used a Moggs .63 reducer at 50 mm from the CCD at prime focal on etx 105 ec. Tested the reducer on jupiter and measured the diameter at 31 pixels. Without the reducer jupiter measured 49 pixels arcross. so around .63 x reduction factor. So im fairly confident at this stage that it works at a distance of 50 mm. The etx 105 is at F14 so 14 *.63 = F8.8 Getting the focal length : 8.8 * 105 ( for the diameter of the scope) = 926.1 mm. From http://ccdastrophotography.com/CCDfov.html using a meade dsi. 9.6 microns x 7.4 mins. Somehow i get 4.89 mm X 3.690 mm for the dimensions of the ccd chip. :) w ArcMin = (4.896 x 3438) / 926.1 = 18.17562682215arc mins h ArcMin = (3.690 x 3438) / 926.1 = 13.6985422740 arc mins So get 18.17 arc mins X 13.69 arc mins of sky. Diameter of the moon is 3476 km . moon is 31.38 arc mins around on that day. thus (18.1756268/ 31.38) * 3476 2013.3358455646 kms x axis my ccd is 510 pixels wide thus 2013.3358455646/ 510 kms = 3.9477173442 kms per pixel so Crater plato at 27.66 pixels =~109.1938617 kms diameter. That all seems all nice and fine but I ve increased the distance from the CCD to the focal reducer and the CCD unit closer to the scope so it would focus properly. Increased it from 50 mm to 60 mm. When compare the new images i get a reduction factor of .28 That would bring down my scope to a F4. instead of F8. just by moving it further by 10 mm? http://legault.club.fr/index.html Describes the formula for focal reducers. so for my etx Distance= 50 mm Reduction factor = .6 therefor FR = D/(1-R) = 50 / (1 - .63) = 135 mm focal length of reducer. I was wondering if its possible to transpose this r = 1-(D/fr) because im unsure how to find the focal length of the reducer? When i check it by eye the focal length appears more like 200 mm. And when i use 200 mm in : d = Fr*(1-R) D = 200*(1-.63) = 74mm as the nominal distance to which the reducers works at .63. But at 50 mm i had the same reduction factor? I dont know how to work out the focal length of the reducer to find the focal ratio to ultimately get the fov. hope some of it makes sense.Mike here: Yeah, you lost me at the end. I never thought of a focal reducer having a focal length since what it does is REDUCE the focal length of the main optics, just as a Barlow Lens LENGTHENS the focal length.
Sorry Mike :) Thats fine. Ive found a great site that discusses reducers etc and Ive found my answer :). from here : home.earthlink.net/~celstark/id7.html I bet if i looked in your site i would have found the same link somewhere. I didnt know some basic information on astronomy so this site was good for me. http://www.astronomyforbeginners.com/astronomy/howknow.php#masssun Thanks for replying and i Hope next time I would have some nice pics of galaxies from the southern hemisphere. Melbourne. Australia.
Subject: Re: MaxView DSLR II Sent: Thursday, July 21, 2005 11:30:23 From: Paul Giguere (firstname.lastname@example.org) The Scopetronix MaxView DSLR II looks great (nice write-up) but do you think that it would be too heavy when used with a Canon 10D on my ETX105PE? Paul GiguereMike here: Since I don't have one I can not check the weight but it might be OK, especially if you add a counterbalance (which the Scopetronix Piggyback adapter can become).
Subject: Re: Piggyback astrophotography on ETX105PE? Sent: Thursday, July 21, 2005 07:59:10 From: Paul Giguere (email@example.com) I was wondering if anyone has tried piggyback astrophotography using an ETX 105PE? I'm thinking of getting the Scopetronix mount but it seems to me like the LNT might get in the way of properly mounting the adapter. It seems like the mount may not come down close enough to the forks. Paul GiguereMike here: Just eyeballing my ETX-105PE it looks like there is room both ahead and behind where any interference with the base would occur. But I'd wait for a more definitive response.
Subject: Focusing a Faint object Sent: Tuesday, July 19, 2005 01:41:25 From: Mat Little (firstname.lastname@example.org) After toying around with my new ETX-125PE, i decided to try a polar align, to my suprise it work pretty well for the first try. I saw polaris in my eyepiece, and when asking autostar to go to the andromeda galaxy, it found it, and almost had it dead center. Having purchased the t-mount for my Canon Digital Rebel, I decided to give it a test spin. I pointed the scope at mars, and got it centered in the eyepiece. I then switched the mira so that i could see throw my camera eyepiece. This resualted in mars being a large ring, so i focused it pretty well, with out a problem. ( i have read the article on the hartmann mask, and it seems like a good idea when focusing bright clearish objects) Problem came when i pointed back at the Andromeda Galaxy. leaving the scope alone for about 5 minutes, and checking periodicly, i could see that it was tracking well, and that the galaxy stay center. So i switched the mira, and laid on the ground so i could get to my cameras eyepiece. What did i see? nothing, not enough light to see rings of a possible star. So i turned the focus knob in, like i did with mars to try and see if something could come into focus. Nothing. Any usefull tips could really help, thanks. -Mat Little (and if it helps, im on a very tight budget seeing that i just droped 1k$ on this wounderful telescope)Mike here: Focusing on a camera viewscreen or LCD is a challenge with faint objects. Focusing on a nearby bright star (and using a Hartmann Mask, which will make the star fainter) does help. But then you have the problem of getting the telescope pointed back precisely at the target object. Just one of the joys of doing through the telescope astrophotography. Requires patience.
Subject: Why Polar Alignment for Photography? Sent: Friday, July 15, 2005 07:27:04 From: Brett Yesukaitis (email@example.com) First, I want to thank you for the wealth of information that you and your site provide. It has helped me embrace this new hobby instead of packing it up. I've been working with my ETX-70AT for 7 months now (a Christmas gift), and am starting to look into astrophotography. Considering the limitations of the scope and cost involved, I thought I'd start with the piggyback method. What I am trying to understand is why Polar Alignment is required? One of the selling points of the ETX (and many other Meade models) is the tracking feature. If it indeed tracks the target accurately (within reason), why the special mounting..especially with the Piggyback method? Just curios. Any information or direction is appreciated. Again, thanks for a great site. BrettMike here: Have you ever noticed when looking at constellations in the sky that they change orientation as they march from East to West? For example, Orion rises on his side, stands tall and straight up when he is due South, and the lies back down on his other side as he sets in the West. "You" are mounted in Alt/Az mode, hence you see this rotation. The same thing will happen when doing photography with an Alt/Az mounted telescope. The effect is called "field rotation". You eliminate it by accurately polar mounting the telescope.
Subject: ETX-125PE Sent: Wednesday, July 13, 2005 09:35:23 From: User721401@aol.com (User721401@aol.com) Just wondering if it is possible to photograph the shuttle and ISS when they are docked using the ETX125-PE and the Nikon D70. If it is possible, what suggestions would you have to obtain such a picture. Thanks DanMike here: People have photographed the ISS from an ETX. It appears as a white cross or X. You will need to enter the ISS TLE into the Autostar, then wait for a pass. For more on satellite and ISS tracking see the Helpful Information: Autostar Info page. During the pass you will need to have your camera attached ready to go. Good luck! Looking forward to seeing results!
Subject: Etx 125/ digital camera photography Sent: Tuesday, July 12, 2005 18:44:29 From: al moro (firstname.lastname@example.org) Recently I bought myself a digital camera, the picture that I sent you. I usually hold the lens above the eye piece, but I find that it is difficult because that light seems to come in a angle instead of the full center, when I am trying to take a picture of the moon. I was wondering how I can improve my pictures by using what different type of eye piece. The eye piece that I am using is the standard 26mm that comes with the ETX 125.Mike here: Depending upon the model camera and whether it has a filter attachment thread on the lens, you may be able to use the Scopetronix Digi-T System. See the Accessory Reviews: Astrophotography page for more info.
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