kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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Well, the title says it all really. The telescope is orion 100mm f 6.0 achromatic refractor. I just upgraded to the 2in dielectric diagonal and was very excited until I popped in my longest focal length eyepiece, a 32mm 2in astrola and focus was achieved with 1/4-1/8 of an inch left of focuser in travel. My 20 and 25 mm eyepieces come very close to focus with the focuser all the way in My 9mm plossl and 7.5mm ultrascopic come to focus, but once again with a smidgen of in travel left  . With my 2x shorty celestron ultima barlow, no focus with the focuser all the way in 
Short of cutting an inch or so off the tube is there a way to get my eyepieces to focus? Also, are there eyepieces with are designed to focus with the focuser farther back?
It seems to me that orion should have forseen this, why supply a 2in focuser if it is unuseable with a 2in diagonal 
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RussL
Music Maker
Reged: 03/18/08
Posts: 1598
Loc: Cayce, SC
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I think I see what is happening, but I don't know the solution. With the 2" diagonal the center of the eyepiece is moved back by 3/8" (1/2 the difference between 1.25" and 2"). Hmm, like you, it would make me want to shorten the focuser--maybe a half-inch would do. Wish I could give you a better answer. Someone will, I'm sure. 
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--Russell
"Akita mani yo." Observe everything as you walk. (--Lakota)
Celestron Celestar 8 Standard SCT, f10
Celestron 80mm Wide View ref., f5
Criterion RV-6 Dynascope, Newt., f8, (c. 1962)
Sears Discoverer 60mm ref., f7, (c. 1973)
Celestron Ultima DX 10x50, 6.5 TFOV
Tasco 7x35 wide
Several mediocre eyepieces
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Tamiji Homma
sage
Reged: 02/24/07
Posts: 413
Loc: California, USA
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Kroum,
You might want to try to insert 2 inch barlow lens between
telescope and diagonal. It gives you outward focus distance.
You may need extra outward focus distance instead, i.e.:
2 inch extension tube 
telescope focuser -> [2 inch extension tube] -> barlow -> 2 inch diagonal -> eyepiece.
I would guess you acquired to use 2 inch long focal eyepiece
for wider view. Adding barlow in may defeat original purpose.
It may be too late but there are low profile (adding
shorter optical path) 2 inch diagonals. I remembered
Astro Physics MaxBright diagonal is bit shorter...
By the way, I agree with you that there isn't much
information about what combination (telescope/barlow/diagonal/eyepiece/binoviewer) works.
It is often to learn such thing hard way... CN is a good place to
ask before you buy
Tammy
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RussL
Music Maker
Reged: 03/18/08
Posts: 1598
Loc: Cayce, SC
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Wait a minute, Tammy may be right.  Don't go cutting anything yet.
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--Russell
"Akita mani yo." Observe everything as you walk. (--Lakota)
Celestron Celestar 8 Standard SCT, f10
Celestron 80mm Wide View ref., f5
Criterion RV-6 Dynascope, Newt., f8, (c. 1962)
Sears Discoverer 60mm ref., f7, (c. 1973)
Celestron Ultima DX 10x50, 6.5 TFOV
Tasco 7x35 wide
Several mediocre eyepieces
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kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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LOL! Of course I'm not going to start cutting before I exhaust all other possibilities.
Unfortunately getting this diagonal exhausted the funds I have for the time being and I would much rather spend any future funds on better eyepieces.
I found a "ghetto" way of making the barlow work. I unscrew the bottom part of the barlow (it looks just like the bottom barrel part of most eyepieces, and I removed said bottom barrel of my high power eyepieces and put the barlow in instead of it. I can only screw in the barlow a tiny bit, but enough for it to stay on the bottom of the eyepiece and not fall into the diagonal. By doing that I can indeed reach focus with both my 7.5, and 9mm. I don't like doing this though because it's pretty obvious the thread on the barlow and the eyepieces isn't the same. It threads on about half to 1 rev, but it doesn't want to keep going, so I'm still ging to have to find a solution to this diagonal problem. Maybe I can go to orion and have them cut the tube for me  , but I highly doubt it. I really like the diagonal, I don't want to have to go back to the 1.25 or have to buy another one that costs twice as much.
Thanks for the help Russ and Tamiji.
Anyone else have any ideas?
It's strange because the focuser itself has VERY long travel, and it's all useless to me. Maybe this focuser is from a different spec scope and was put on this by mistake...nah, they probably all use the same focuser.
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drshr
sage
Reged: 06/09/08
Posts: 207
Loc: Australia
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I have had this problem also in my 80mm. I found that my cheap Ultra wide angle Night Owl EP's work fine without barlow. Just another alternative.
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Doc
14" F5 DOB.
6" f5 Achro.
TMB/APM 105mm F6.2 CF APO.
"In order to make an apple pie from scratch, you must first create the universe"
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kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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How are those, I was eyeing them on ebay.
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walt r
Carpal Tunnel
Reged: 02/13/07
Posts: 2414
Loc: Doylestown, PA
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I also don't have enough information to offer a solution. My first guess is that the image plane is too close to the focuser and thus inside the diagonal.
He needs to measure where the focal plane is in relation to the focuser to see if the diagonal can be used.
Check here for the distance from the EP flange to the focal plane on TV EPs (I don't know of the existence of this information for other EPs). This can give you an idea of what is required.
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4763
Loc: Zuni Mtns, NM
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Doesn't the Orion come with a 1.25" diag?
This is fairly common. a 2" diag adds a lot of distance in there compared to a 1.25".
I guess short of making the tube a little shorter, you could search around and find the shortest distance 2" out there, it would probably work.
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4763
Loc: Zuni Mtns, NM
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PS: If you unscrew the diaginal barel, does it happen to attach right to the draw tube?
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kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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I haven't tried attaching it directly to the draw tube. When I get home today I might try it. It will make it very uncomfortable to see, though since I will no longer be able to rotate the diagonal.
I think I have decided to live with it for now. I may or may not upgrade the focuser in the future, and I don't want to do any tube cutting before I know how the situation will sit with the other focuser, and I guess I will have to screw the barlow directly onto the eyepiece for high power views... or jsut buy really short fl eyepieces. It might even be beneficial to the telescope to have focus be so far in, less torque on the focuser tube from the heavy diagonal+eyepieces.
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GeorgeDuke
Pooh-Bah
Reged: 04/24/03
Posts: 1164
Loc: PARADISE! (So.Florida)
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Threads on the barlow element and the filter threads of your eyepiece should be the same unless one or the other is made wrong. It is very common to attach a barlow element to the bottom of an eyepiece to give you a different power. The 80deg OWL or Birdseye (same eyepiece) 20mm is the 30mm with a barlow element on the bottom! I bought the 30mm and the GSO 2" ED barlow to give me both for less money.
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George
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LX200GPS 203mm f10
StellarVue SV102ED2 Feathertouch Ser#0018
Celestron 130mm f15.4 Mak
LXD75 GOTO with Orion 16" pier extension
Desert Sky DSV1 dual head ALT-AZ mount
Baader Hyperion 8mm ,13mm, 21mm and 8-24mm Zoom + FTRs
2" GSO ED barlow, Orion 2" Prism Diag. 2" WO Dielectric
Chinese Scopes, Chinese Eyepieces, Chinese Wife, Love them all!
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kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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That's exacly the kind of eyepiece I am looking to get. How do the OWLs perform? How far from the center of the FOV does it start getting fish bowl-ie?
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drshr
sage
Reged: 06/09/08
Posts: 207
Loc: Australia
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The OWL's are very good. Not quite as bright as my Meade UWA's and at F5 there is some slight field curvature. At F6+ they are great. Best thing is they will solve your problem and give you an 80deg field of view!
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Doc
14" F5 DOB.
6" f5 Achro.
TMB/APM 105mm F6.2 CF APO.
"In order to make an apple pie from scratch, you must first create the universe"
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kroum
super member
Reged: 08/28/08
Posts: 165
Loc: Bay Area, CA
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I don't know if this is not allowed, but can you guys point me to a place where I may procure them? Or if not, PM me?
I remember seeing some on ebay a week or 2 ago, but no more...
Edited by kroum (09/08/08 06:31 PM)
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drshr
sage
Reged: 06/09/08
Posts: 207
Loc: Australia
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I bought mine from eBay. Fast delivery and well packed. Nice all black look. They are now my most used EP's on all my scopes because they are so much lighter than the Meades and Televues so there are no balance issues and the crayford focuser doesn't struggle near zenith. You are right, they are no longer on eBay which is a shame as I would like their 11mm. I have all the others and they are almost parfocal. I am sure they will return 
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Doc
14" F5 DOB.
6" f5 Achro.
TMB/APM 105mm F6.2 CF APO.
"In order to make an apple pie from scratch, you must first create the universe"
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