Celestron CG-5 GOTO for Astrophotography?

[renderwerks]

Hi,

I've been looking at mounts for astro. I found someone selling a Celestron CG-5 GOTO (with the 2" tripod legs) that has upgraded high precision worm gears in it.

I have a Celestron Onyx 80EDF (500mm f/6.5), a Canon 40D and lenses from 11mm up to 200mm. I'll probably be getting a WO focal reducer as well (reduce to 400mm).

Assuming a good polar alignment, how long of an exposure could I get with this setup? I would like to evenually shoot some DSO's that would show realitively large in the images.

Could the mount be upgraded any more? Motors, etc...

Thanks,

[Nighthound]

I'm not familiar with the mechanics of this mount or how easy it will be to access the gears, etc. but it's always helpful to upgrade lubricants as well. Having gear upgrades will certainly be a good thing but knowing the quality of the upgrades is going to be difficult until you test them. It would be nice to know if the worm gears are adjustable for fine tuning tension which would be very helpful for minimizing any gear slop(backlash). If you don't get some experienced user input here I would suggest posting these questions at Cloudy Nights. You're bound to get some answers there.

What are your exposure length hopes with the 80mm?

[renderwerks]

I'm not familiar with the mechanics of this mount or how easy it will be to access the gears, etc. but it's always helpful to upgrade lubricants as well. Having gear upgrades will certainly be a good thing but knowing the quality of the upgrades is going to be difficult until you test them. It would be nice to know if the worm gears are adjustable for fine tuning tension which would be very helpful for minimizing any gear slop(backlash). If you don't get some experienced user input here I would suggest posting these questions at Cloudy Nights. You're bound to get some answers there.

What are your exposure length hopes with the 80mm?

Thanks Steve,

I'll try a post at cloudy nights.

I'm not sure about exposure lengths. I've never done this. What I hope to acheive is sufficient exposure to be able to get some depth and detail in objects like the nebula in Orion, Andromeda galaxy and pleiades for starters. I'll want to take multiple exposures and stack them before PP in PS3.

What I'm hoping for is enough to keep me busy with the 80mm and a mount for perhaps a year or more. I'll probably get a chance to venture out perhaps 20 weekends a year (weather permitting).

[Nighthound]

You're welcome Rick. I would aim for 2-3 minutes with the mount you choose. Pose the question at CN for some actual exposures accomplished with the CG-5 or the like. Auto guiding would make the long exposures more attainable but would also require a guide scope and second camera(more $) so to get started I would try to get the best GEM you can budget and the fact that you're paying close attention to gear upgrades, etc. makes me feel confident you'll do just that. Keep us posted.

[FarmerDave8N]

You're welcome Rick. I would aim for 2-3 minutes with the mount you choose. Pose the question at CN for some actual exposures accomplished with the CG-5 or the like. Auto guiding would make the long exposures more attainable but would also require a guide scope and second camera(more $) so to get started I would try to get the best GEM you can budget and the fact that you're paying close attention to gear upgrades, etc. makes me feel confident you'll do just that. Keep us posted.

I've done 2-3 minutes on a stock CG-5, with a throwaway rate of 25-30% at 300mm - 480mm. Autoguiding helps significantly - the PE on those mounts is not the greatest - but replacing the gears should help.

Bear in mind that you can autoguide fairly cheap with a cheap scope ($150) with a cheap camera (DSI=$100/webcam=less), and free software. I know of some folks who are autoguiding with finder scopes, even.

Oh, and +1 on the CN suggestion. Lots of AP knowledgeable folks there.

David

[renderwerks]

Thanks for the responses. I have been checking out CG-5 mods over at astronomyboy.com. That is the site where I got some ideas for my barn door mount (still waiting on the motor!:mad:). They have several sources and read alongs for improving the mount. From what I've read, the CG-5 (and others) are clones of the Vixen Great Polaris mount. Who knows, by the time I'm done researching, I might be able to afford a better GEM!

[renderwerks]

OK, so I got several responses (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2747408/page/0/view/collapsed/sb/5/o/all/fpart/1) on Cloudy Nights. Sounds positive. Most say 2-3 minutes are possible without guiding, and a few have said better than 10 minutes with autoguiding. But, there's a new wrinkle...

I was over at the Oceanside Photo & Telescope (Opt) website looking at GEMs and came across the new iOptron GEM mount (http://www.optcorp.com/product.aspx?pid=439-278-12272&kw=&st=0). I went to the iOptron website (http://www.ioptron.com/products_con.aspx?pro=GO%20TO%20MOUNTS&id=19)and read up on it. Any experience or opinions on this?

I additionally was searching CG-5 upgrades and came across a website: Trapezium Telescope (http://trapeziumtelescopes.com/cms/) They perform "tune-ups", OTA refinishing (painting), custom fabrication and other services. They also sell iOptron products "because they are high quality". They additionally say they will eventually sell other products that "meet their high standard of quality" and will soon sell mounts of their own design.

Not knowing this company, I wondered if iOptron might own this website... Does anyone have experience/knowledge of this company? What do you think?