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Orion64
scholastic sledgehammer


Reged: 11/29/09

Loc: Western Cape, South Africa
Ready to give up on AP new
      #5631286 - 01/19/13 10:37 AM

Hi folks, I know this seems a bit drastic, but I am really tired of struggling with the same issue for over a year. I have now spent almost 6000USD on my equipment upgrade. Since then it was only trouble.
My system actually only has one flaw, but this makes it impossible to take photos.
I have a carbon fiber 10inch f/4 newtonian. I purchased the ASA korr reducer/ corrector. My spacing is perfect, although I tried a lot of spacings. Stars in all corners are perfect, EXCEPT one. The one corner is drastically out of focus with lots coma.
I dont think its the ccd. When rotating, the corner gets better but others get worse.
The only answer I get is orthogonality. but I have changed everything in my system now. Nothing gets the problem better.
I have calculated my correct offset of secondary and used how glatters tools in combo with Jason Khadder's colimation steps to colimate my system. No difference. Should I maybe colimate without offset???????
I must add that I have some focusser sag, but I have tried improving it to see the effect and no change to my problem.

The only solution I have to continue my hobby is to do mosaics. This way I can overlay the good part of my 2nd image over my bad part of the 1st image.


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vpcirc
Post Laureate


Reged: 12/09/09

Loc: Merced CA
Re: Ready to give up on AP [Re: Orion64]
      #5631346 - 01/19/13 11:10 AM

Newts are very sensitive to collmanation. The faster the optics the more flaws will show. I wonder if you have a defect in a mirror?

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fetoma
Carpal Tunnel
*****

Reged: 09/26/06

Loc: Southern New Jersey
Re: Ready to give up on AP new [Re: vpcirc]
      #5631588 - 01/19/13 01:32 PM

If you have focuser sag, try imaging with the focuser on top of the tube.

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guyroch
Vendor (BackyardEOS)
*****

Reged: 01/22/08

Loc: Under the clouds!
Re: Ready to give up on AP new [Re: fetoma]
      #5631601 - 01/19/13 01:38 PM

Quote:

If you have focuser sag, try imaging with the focuser on top of the tube.




I have to agree. How much weight do you have from hanging on the focuser?

I have the same issue right now with my AT8RC. I put the same gear/weight on my AT6RC and all is fine. But on the AT8RC I can't seem to fix it. I understand your frustration first hand.

Guylain


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Orion64
scholastic sledgehammer


Reged: 11/29/09

Loc: Western Cape, South Africa
Re: Ready to give up on AP new [Re: guyroch]
      #5631609 - 01/19/13 01:42 PM

I found an adapter that adjusts any tilt that one has in the optical path. So I wihl place my order on monday and try this out. Its not expensive, so its definitely worth giving a go.

Tonight is one of those clear wind still nights, however my equipment stays in doors until my adapter arrives.


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: Ready to give up on AP new [Re: guyroch]
      #5631611 - 01/19/13 01:42 PM

Are you sure that the sensor is correctly mounted in the camera housing?

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SANDRO78
super member


Reged: 06/12/12

Loc: fr
Re: Ready to give up on AP new [Re: Orion64]
      #5631672 - 01/19/13 02:29 PM

Effectively, there is a problem on the set up, but I hope that you will arrive has to solve your concern(marigold)??
You have ask advice has ASA or to the manufacturer of the CCD?

Go courage!!


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Orion64
scholastic sledgehammer


Reged: 11/29/09

Loc: Western Cape, South Africa
Re: Ready to give up on AP new [Re: SANDRO78]
      #5631746 - 01/19/13 03:22 PM

I cannot confirm that there is no fault with the sensor, however,as I stated when I rotate the camera, the unfocussed corners shift to another spot.

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zerro1
Postmaster
*****

Reged: 08/02/09

Loc: Smokey Point , 48.12°N 122.25...
Re: Ready to give up on AP new [Re: Orion64]
      #5631785 - 01/19/13 03:40 PM

Quote:

I cannot confirm that there is no fault with the sensor, however,as I stated when I rotate the camera, the unfocussed corners shift to another spot.




I take that to mean that the defocussed location does not rotate with the camera...

Do you have this problem without the reducer/corrector?


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Orion64
scholastic sledgehammer


Reged: 11/29/09

Loc: Western Cape, South Africa
Re: Ready to give up on AP new [Re: zerro1]
      #5631847 - 01/19/13 04:47 PM

Could not test this because I only have the one reducer. Wouldnt I have horrible coma all over when testing without a reducer?

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jmasin
Carpal Tunnel


Reged: 12/22/08

Loc: Murphy, TX (DFW)
Re: Ready to give up on AP new [Re: zerro1]
      #5631851 - 01/19/13 04:50 PM

Brett,

Others gave good advice and it seems you have something to try. Don't give up, I have known that level of frustration before, so can relate. It is worth it when you get it right.

Jon


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zerro1
Postmaster
*****

Reged: 08/02/09

Loc: Smokey Point , 48.12°N 122.25...
Re: Ready to give up on AP new [Re: Orion64]
      #5631916 - 01/19/13 05:29 PM

Quote:

Could not test this because I only have the one reducer. Wouldnt I have horrible coma all over when testing without a reducer?




I would think it should be fairly uniform with well focused good looking stars in the center region and increasing coma radiating to the edge of field. If it looks like a normal uncorrected field then it's possible the reducer/corrector is introducing the distortion

You may want to consider just a coma corrector without the focal reduction...

Edit:: I'm pretty sure that moonlite sells a really nice focuser assembly that would solve sag without buying a whole new "APO" scope, for somewhere in the $300 dollar range.

Edited by zerro1 (01/19/13 10:03 PM)


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mmalik
Post Laureate
*****

Reged: 01/13/12

Loc: USA
Re: Ready to give up on AP new [Re: Orion64]
      #5632228 - 01/19/13 09:15 PM

Quote:

Ready to give up on AP




Don't; here are some thoughts/suggestions, I am afraid you'll have to spend just a bit longer.

1. Ditch your Newtonian; buy or test your setup on an APO if you have access to one. That will rule out the scope. Personally, I am for APOs when it comes to AP; rest are just half measures in my opinion.

2. To rule out its not the scope, try a DSLR on the same setup if you have access to one. May borrow one if you can or just buy a good one that you may also keep using alongside the CCD.

3. You seem to have too much weight for your focuser; changing scope with an APO may bring a solid focuser into the picture.

4. Orthogonality of the sensor, if true, will require fixing or swapping your existing CCD with a different one. One of the above should help to confirm/reject that conjecture.

5. Last, but not least; start salvaging your entire setup in favor of starting fresh and recouping some of your losses. Weakest link in your setup are your scope/focuser in my opinion.


Some useful links in light of the above:

APO consideration...

DSLR consideration...

DSLR image processing instructions...

Other CCD alternatives...


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blueman
Photon Catcher
*****

Reged: 07/20/07

Loc: California
Re: Ready to give up on AP new [Re: Orion64]
      #5632327 - 01/19/13 10:16 PM

I had my years of frustration with reflectors. Flexure, coma, field curvature all of the problems that you can face, I wrestled with in spades.

I finally went to a good APO refrator and never had to deal with these issues again.

Am I saying reflectors are bad? No. I am saying they can be very difficult to deal with and life is too short.
Blueman


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vpcirc
Post Laureate


Reged: 12/09/09

Loc: Merced CA
Re: Ready to give up on AP new [Re: blueman]
      #5632353 - 01/19/13 10:34 PM

I'd ditch the CGEM before anything else!

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JWalk
Pooh-Bah


Reged: 06/06/10

Loc: San Antonio, TX
Re: Ready to give up on AP new [Re: vpcirc]
      #5632460 - 01/19/13 11:49 PM

Quote:

I'd ditch the CGEM before anything else!




Don't knock the CGEM!!! It is capable. Couldn't resist Mikey


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elbee
professor emeritus


Reged: 05/02/09

Loc: Arizona
Re: Ready to give up on AP new [Re: JWalk]
      #5632556 - 01/20/13 01:46 AM

Quote:

Don't knock the CGEM!!! It is capable.



uhhh, Paramount? is that the consequence of a close relationship with a CGEM


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Orion64
scholastic sledgehammer


Reged: 11/29/09

Loc: Western Cape, South Africa
Re: Ready to give up on AP new [Re: elbee]
      #5632711 - 01/20/13 07:46 AM

Thanks for the replies guys. I have access to an apo refractor. I will try my setup on this in the mean while

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vpcirc
Post Laureate


Reged: 12/09/09

Loc: Merced CA
Re: Ready to give up on AP new [Re: elbee]
      #5632771 - 01/20/13 09:15 AM

Quote:

Quote:

Don't knock the CGEM!!! It is capable.



uhhh, Paramount? is that the consequence of a close relationship with a CGEM




Yea I started with one those &$$@@%~} mounts. Jimmy is giving me a hard time because he shot beautiful images on one. (He got a good one)
I hadn't read Wodaski's book when I started telling me most of money should be in the platform. I was also doing a typical beginner mistake and going for the most aperture I could afford, then reality set in! Once I bought my first AP, I'd never go back to a low end mount. I'd image with a 15 year old APO and a 5 year old camera before I'd image with a poor platform!
Jimmy why don't you send that AP1600 with encoders back and put that new RC 16" on a CGEM deluxe? Lol In all fairness, CGEMs have gotten better since I owned one 4 years ago.


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JWalk
Pooh-Bah


Reged: 06/06/10

Loc: San Antonio, TX
Re: Ready to give up on AP [Re: vpcirc]
      #5632818 - 01/20/13 09:41 AM

I wouldn't put much on top of the CGEM. I think my FSQ was about at the limit of one.

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