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Collimation with an electronic eyepiece?

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#1 Snaproll

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Posted 25 December 2007 - 08:36 PM

I've never used a Meade #902 Electronic Eyepiece but was wondering if it may be used for collimation.

With the 10" SCT I currently have I can barely reach the collimation knobs and still look through the eyepiece. Currently I have a C14 coming in and imagine collimation has to be a two person job... or not? :question:

What I'm thinking is running the video eyepiece to either a 5" TV or to some video eyeware so I can stay by the corrector and adjust collimation. I could also have the controller handy to recenter the star if it shifts because of a collimation correction. In short, I could collimate the scope myself... assuming that the Meade eyepiece can resolve the collimation rings. It's supposed to be the equivelent of a 4mm eyepiece, should be good enough if this is a fact.

Does anyone know if the Meade eyepiece is good enough to do collimation?

I'm also planning on using a Hutech Rebel XT via Fastar/Hyperstar lens. I focus the Rebel with a Stiletto. I figure it could be kind of rough trying to see in the eyepiece while focusing it while it's mounted to the corrector plate. If this eyepiece works, then I could use it on the Stiletto as well. With the Fastar option the C14 becomes a f1.9 so focus shouldn't be as critical I would guess. I know I can use a laptop to find focus for the camera but would like to stay away from using a PC in the field.

Any thoughts? Has anyone else tried this, or is there a better collimation/focusing option?

#2 JimK

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Posted 25 December 2007 - 11:09 PM

I've not tried using the electronic eyepiece (EEP) with my C-8 sct yet, but I imagine to see diffraction rings a bright star is needed. The focal length is about 7mm, giving about 290x magnification in my C-8, so it might work. With scattered area storms and various holiday stuff happening, it'll be several days before I can try it, but I will.

#3 b1gred

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Posted 26 December 2007 - 12:42 AM

Artificial star??

#4 Chris Schroeder

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Posted 26 December 2007 - 08:01 AM

Hey Jim, the Meade E-EP are cheap enough, I've got a 5" B&W portable TV. If nothing else it'll be good for public out reach. It the Meade doesn't work, I bet my Orion Star shooter will, 1280x1024 resolution and 15 frames per sec.

#5 Snaproll

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Posted 26 December 2007 - 09:28 AM

"...it'll be several days before I can try it, but I will."

Thanks Jim, if you get the chance I would appreciate it.

An artificial star would be OK Randy, but I'm not sure how much mirror flop there will be with the C14. I usually like to collimate in an area of the sky where I'm going to image.

Chris, it's funny, I couldn't find out any information on the Starshooter short of early reviews. From what I gather it's about the equivelent of a Meade DSI. I wonder if Orion discontinued it? I don't think it would work for my purposes though, too expensive for one and it looks like it's only USB output. I really want to stay with video output so I don't have to have a PC in the field.

If the Meade eyepiece isn't sensitive enough I know the STV will work, but the Meade EP if it works, will be much smaller.

#6 JimK

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Posted 29 December 2007 - 10:52 PM

Short Answer - I do not believe that the Meade electronic eyepiece (EEP) can be used for properly collimating an SCT.

Discussion
1) I did not know where the center of the field was on the display screen, and that parameter is vital in sct collimation. I suppose that I could center an object with my 2.5x barlowed 25mm kellner cross-hair eyepiece, then tape a circle printed on a transparent sheet onto the display in the correct spot, but I didn't have time to do that.

2) When out of focus, some diffraction rings could be seen, but only hints of rings could be seen when in focus. The magnification was about 290x, and I did not have time to see if a barlow would add more infocus rings. The display itself was somewhat fuzzy, which I believe is the nature of the EEP output itself, so I don't think that the image will ever be crisp enough for collimation needs (even after adjusting the EEP contrast dial).

Parameters - Orange-tube C-8 SCT, no diagonal or focal reducer, 7:30 PM MST, 28 F & no wind (calm), scope acclimated several hours (no tube currents observed in defocused star image), initially 30% cloud cover, but increased rapidly to over 90% (giving only 5 min of observing time), jet stream probably overhead because of rapidly moving clouds, Rigel used as collimation star because of magnitude (0.14) and moving cloud cover (although altitude was only about 20 deg). This meant that the star image was dancing around, also not a great way to perform collimation. Fortunately I did not adjust the sct secondary screws in this situation.

Epilogue - I will only use an optical eyepiece to collimate a telescope.

#7 Snaproll

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Posted 30 December 2007 - 03:52 PM

Thanks for taking the time to check it out Jim. I think the concept will still work, but what I'll use will be the STV which is more sensitive. I think I'll try that first. Again, my thanks for the info.

#8 ccs_hello

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Posted 30 December 2007 - 03:59 PM

I suspect not be able to see defraction rings clearly is not because of imager's sensitivity but not enough spatial resolution. Just my 2 pennies :) :).

Clear Skies!

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#9 Snaproll

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Posted 30 December 2007 - 04:05 PM

Well, I'll give it a try with the STV when the scope gets here, see how it goes. Perhaps Chris can lend me his EEP and I can try it before picking one up.


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