Treehopper
professor emeritus
Reged: 07/29/08
Posts: 582
Loc: Upstate NY
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I did some snooping around and found an interesting article on Weasner's site by a Lee Vincent regarding using 2" accessories in ETX catadioptric instruments. At first I thought the only possible way (if you could do it at all) would be to go through the photo back/accessory port on the back of the focus assembly. While I never measured the portal, it seemed wider than the 1.25" EP port in the built-in "diagonal" on these scopes.
According to Vincent, however, using an adapter he found online, he has used a variety of 2" eyepieces directly through the diagonal port (with the adapter), and has not experienced any vignetting or loss of FOV through the wider angle EP's. The ETX-125, in particular, has sufficient back-focus built into the mechanism as to accommodate the shift in focus.
Here's a link to Vincent's article on Weasner's site. Includes several photos.
Here's a link to Agena Astro, where he bought the adapter.
Would be interested to hear if anyone else has tried this. I'm toying with the notion of experimenting with this some time in the near future to see what kind of views I can get on the 125.
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Tim
Champion of small aperture scopes everywhere!
Meade ETX-125PE
Meade ETX-80
Celestron FirstScope 76mm Mini-dob
 Updated: 09/16/2009
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brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2119
Loc: 55.215N 6.554W
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Quote:
has not experienced any vignetting or loss of FOV through the wider angle EP's.
Not been looking carefully then. The bore in the back port adapter is about the same size as the tube of a 1.25" EP, and the fully illuminated field width is much less than that (restricted by the baffle tube & the size of the secondary mirror "spot"). At least that's the way it was on the ETX 125 I once had.
There is no way of getting a wide field out of these scopes. If you want a rich field scope and are attracted by the ETX mount, get an ETX 80.
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Treehopper
professor emeritus
Reged: 07/29/08
Posts: 582
Loc: Upstate NY
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Quote:
Quote:
has not experienced any vignetting or loss of FOV through the wider angle EP's.
Not been looking carefully then. The bore in the back port adapter is about the same size as the tube of a 1.25" EP, and the fully illuminated field width is much less than that (restricted by the baffle tube & the size of the secondary mirror "spot"). At least that's the way it was on the ETX 125 I once had.
Although purely anecdotal, I've got no reason to doubt Mr. Vincent's observations and experience. If anything, the fact that it has a home on Mike Weasner's very well-respected website slides the bar in favor of his veracity.
Quote:
There is no way of getting a wide field out of these scopes. If you want a rich field scope and are attracted by the ETX mount, get an ETX 80.
Actually, you can open them up pretty good with a decent focal reducer. With regard to the ETX-80...see my sig. 
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Tim
Champion of small aperture scopes everywhere!
Meade ETX-125PE
Meade ETX-80
Celestron FirstScope 76mm Mini-dob
Updated: 09/16/2009
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nighty
sage
Reged: 12/31/06
Posts: 344
Loc: 75w39n
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I have the adapter and have used 32mm 30mm and 26mm 2 inch EPs with the 125. The views are great. You will not be disappointed.
I am not a technical expert, I just look at stars and this set up made me happy.
Only bug is the screw to fix the adapter to the scope seems too short for my fat fingers. The 2 inch ep and the tour of tonight's sky make for awesome outreach possibilities.
Terry
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Stuff to look at stars and things
Scopes For Kids Project
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Treehopper
professor emeritus
Reged: 07/29/08
Posts: 582
Loc: Upstate NY
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Thanks Terry, that lines up with what the article said as well. I wouldn't expect the 40mm EPs would work too well...that may very well be pushing it. But a decent 30-32mm UW would make me very happy.
As far as the screw goes, it seems as though over the Summer someone in the Swap-n-Shop (before it was parsed out) had gotten their hands on a bunch of longer shank screws for just this sort of thing, and was sending them to whoever requested them. Not even sure where he managed to find them, but because he had to order them in bulk, he had a surplus. Sorry, can't recall the particulars, it just seemed to stick out in my mind for some reason when you mentioned it.
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Tim
Champion of small aperture scopes everywhere!
Meade ETX-125PE
Meade ETX-80
Celestron FirstScope 76mm Mini-dob
Updated: 09/16/2009
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Billydee
super member
Reged: 01/23/08
Posts: 186
Loc: Winter Haven, FL
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Here is a company in Florida http://cncsupplyinc.com/ they produce a number of ETX parts (after logging on, scroll down the left side until you find ETX, click on it and scroll down the products). They have a metal 1.25" to 2" EP adapter (threaded for filters) and it is on sale for $27.95. Works on ETX 90/105/125 but it won't work on ETX 60/70/80 because of back focus problems. Not sure if the is what you want but it is nice.
Luck, Bill
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Treehopper
professor emeritus
Reged: 07/29/08
Posts: 582
Loc: Upstate NY
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Awesome, thanks Bill! I also found them at Agena Astro. I was pricing 2" EP's last night online, and you can find decent quality 2" plossls in the 28-36mm range for right around $100, give or take. Of course, those extra-wides are a lot more, but for starting out, I might try around a 32mm to experiment with, and take it from there.
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Tim
Champion of small aperture scopes everywhere!
Meade ETX-125PE
Meade ETX-80
Celestron FirstScope 76mm Mini-dob
Updated: 09/16/2009
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Darenwh
Pooh-Bah
Reged: 05/11/06
Posts: 1224
Loc: Covington, GA
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Wow, I would love to use my ES14 100degree eyepiece on my ETX 90. It would just be alot of fun to use an eyepiece nearly as big as the scope itself. Here is a pic of EXT-90 w/ES14
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Daren
Covington, GA
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Treehopper
professor emeritus
Reged: 07/29/08
Posts: 582
Loc: Upstate NY
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Holy shnikees, Daren! That's a monster! Bet it sees real nice tho!
Hanging that on a 90 tho...you might need a boat anchor on the front end just to counter-balance it! 
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Tim
Champion of small aperture scopes everywhere!
Meade ETX-125PE
Meade ETX-80
Celestron FirstScope 76mm Mini-dob
Updated: 09/16/2009
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nighty
sage
Reged: 12/31/06
Posts: 344
Loc: 75w39n
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I bought the EP's used for less than $30 each. I just saw some in the Swap and shop, If I drop a $30 ep I am not going to cry, and the long focal length makes cheaper
EP's really shine.
Terry
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Stuff to look at stars and things
Scopes For Kids Project
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Darenwh
Pooh-Bah
Reged: 05/11/06
Posts: 1224
Loc: Covington, GA
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Quote:
Holy shnikees, Daren! That's a monster! Bet it sees real nice tho!
Hanging that on a 90 tho...you might need a boat anchor on the front end just to counter-balance it!
That's the truth. Sure will be fun to give it a try though. It will not be the 2" eyepiece I use the most on it though. that would be my 2" 40mm Rini Koenig eyepiece. That eyepiece is a performer and should be great in the ETX 90.
As for the cost of the eyepiece, I won it so no worries. It's worth more than my ETX-90 for sure.
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Daren
Covington, GA
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