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Celestron ASGT for Astrophotography?

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#1 buckeyestargazer

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Posted 07 February 2013 - 01:04 PM

I am contemplating buying a used Celestron ASGT mount for very wide-field astrophotography with a CCD camera and 50mm SLR lens. Are these mounts good for wide field photography? I've read that the periodic error is quite large, but is it too much for an autoguider to overcome with such a wide field? How difficult is it to polar align reasonably accurately. Does anyone know if a Losmandy illuminated polar scope will fit into the ASGT?

Thanks in advance!

#2 jrcrilly

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Posted 07 February 2013 - 01:16 PM

At 50mm and using a OSC camera, you would be working somewhere around 30 arcseconds/pixel. The CG-5 could almost manage that without guiding at all. With guiding, there should be no issue.

There are non-illuminated polar scopes that will fit, but I'm not aware of any illuminated units. The built-in polar alignment routine is simple and effective; I much prefer it over bending over to peer upwards through a PAS, as I had to do in the old days.

#3 bunyon

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Posted 07 February 2013 - 01:18 PM

Joel, I've shot a lot of 50mm with a CG5 with no guiding. PEC is large but for wide fields, it isn't that large. With an autoguider, I've used this mount up to 2000mm and 2 minute subs. I think it would do well for what you want and give you a little room to grow.

A couple of examples, unguided, at 50mm:

Posted Image


Posted Image

These were stacks of multiple 3 minute subs with no guiding and no rejected subs.

#4 buckeyestargazer

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Posted 07 February 2013 - 01:57 PM

Thanks for the replies; that is all very reassuring. Regarding autoguiding vs. not guiding, my camera is a mono cam and I'll be doing some narrowband imaging, which will require somewhat longer exposures than 2-4 minutes. At this image scale I'll be aiming for 10min to as much as 20min subs in narrowband.

Re: the Losmandy illuminated polar scope, I thought I read somewhere else that a "sleave" or something could be removed from the ASGT so that the Losmandy scope could be threaded into the mount. As I already have a Losmandy polar scope, I was hoping to be able to use it with the ASGT.

#5 rmollise

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Posted 07 February 2013 - 02:05 PM

Actually, given an even middling polar alignment, you won't have to guide at this focal length.

#6 Mike X.

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Posted 08 February 2013 - 02:09 AM

I don't know if it helps you but here are some of my photos with a CG5-GT (ASGT) during the years from 2009 up to now:
http://www.astrobin....chael_Xyntaris/

The photos are unguided up to 2010 (with a C6 F:45mm) and guided from 2011 up to now.I use a SW Equinox 80 ED for wide field F:500mm

#7 buckeyestargazer

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Posted 08 February 2013 - 09:18 AM

Nice gallery Mike. Good to know that others are using this mount for AP. I should receive my ASGT in a few days!

#8 nganga

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Posted 08 February 2013 - 01:09 PM

I am contemplating buying a used Celestron ASGT mount for very wide-field astrophotography with a CCD camera and 50mm SLR lens. Are these mounts good for wide field photography? I've read that the periodic error is quite large, but is it too much for an autoguider to overcome with such a wide field? How difficult is it to polar align reasonably accurately. Does anyone know if a Losmandy illuminated polar scope will fit into the ASGT?

Thanks in advance!


Joel,

You can do astrophotography with the CG5. Here is on example of an unguided image with a 300mm lens:

http://www.flickr.co...157624886088450

I have used it with longer focal lengths as you can see in the rest of the collection. Guiding can be "interesting", but that's another story. I have no experience with the Losmandy polarscope yet.

Clem

#9 orlyandico

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Posted 08 February 2013 - 01:29 PM

i'm thinking of selling my CGEM, but before i do, i'm using it.

generally 2 minute exposures at 336mm unguided are OK, but not all the time - depends on where the scope is pointing.

at some positions i can get 6 minutes unguided without trailing. but at other positions only 1 minute.

PEC is on. the raw PE is about 40" and it's about 25" with PEC.






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