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#1 redog

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Posted 18 June 2013 - 08:45 PM

Hi all. First post here. I'm looking for a best-bang-for-the-buck mount for long exposures, in the 30 min. range (and 15 pound capacity). From what I've read here, most of the digital guys are setting high ISOs and getting images at fairly short exposure times, but I'm looking at making images with 100 ISO film (Mamiya RZ; Cambo 4x5)). I've looked at iOptron and Celestron, and need to keep the price to around $500-600 US (used is fine). Don't need "GoTo" technology. So far the Celestron CG-5 and Orion Atlas EQ look good. Any advice would be greatly appreciated. Thanks in advance!

#2 PaulEK

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Posted 18 June 2013 - 10:31 PM

Either of those (newer CG-5 or Atlas) might be fine. The CG-5, used, should be a good deal now, since it was recently upgraded to the new VX. Lots of folks have gotten good use out of the CG-5, at least those actually sold by Celestron, and not the generic 'clones'. The Atlas is a much heavier and heavier-duty mount, and also more expensive, typically.

The thing is, as you say, most folks are not taking long exposures anymore. I own an Atlas, and I'm not sure how well mine would do with 30 minute exposures.

I also own an old Vixen Super Polaris (the CG-5 was originally a copy of this mount). Unlike the newer generation mounts, it is not designed for auto-guiding. There are fixes for this, but beyond my skills. But it has amazingly smooth tracking, and is very solid, with almost no play in its gears. I have taken 30 minute hand-guided (with the controller and a cross-hair eyepiece) images with it. Its solid performance, compared to the Atlas, is why I wonder about the Atlas for long exposures, but this might just by my particular Atlas. Vixen, by the way, sells a descendant of the Super Polaris: the Great Polaris 2 (GP2). It has a load capacity of 22 pounds, though that's for visual.

By the way, the Atlas has a smaller sibling, the Sirius, which might be cheaper, and is definitely lighter (43 pounds, compared to 76 pounds for the Atlas. Did I mention that it's heavy?) The Sirius is rated to hold 30 pounds, visually. All the Orion mounts used to be available without go-to, but I no longer see that option on the Orion website. Used ones will still be available, but possibly without the option of autoguiding.

I've also read good things about the iOptron mounts. They are light-weight, but hold quite substantial loads for their sizes. But since I have no direct experience with them, I can't really comment on their abilities.

I now have a Losmandy G-11, and it will be my imaging mount when I get around to taking photos with my recently purchased Pentax 6x7. That's overkill for what you want to do, but it's a multi-purpose mount for me.

Good luck

#3 Madratter

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Posted 19 June 2013 - 09:40 AM

Wow. 30m is really pushing a mount hard. I have had both the CG-5 and the Atlas. I definitely would not want to attempt this with the CG-5. With the Atlas, you might be able to make a go with this depending on how long the focal length of your setup is.

#4 Doppler

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Posted 19 June 2013 - 03:01 PM

The following thought came to me, but I am wondering if I might be missing something obvious, because I have never seen such a setup....??

I see SCT fork mounts (without scope) come up for sale fairly often - You could fashion a plate (between the forks) to mount the camera on, and build a (wooden) wedge, and have something pretty stable, for pretty affordable. It would be an "equatorial camera fork-mount." You'd need to do something for polar scope (mount a cheap rifle scope?).

What am I missing?

#5 Doppler

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Posted 19 June 2013 - 03:21 PM

Okay, I found something like what I was thinking....

http://www.cloudynig...5842045/Main...

#6 Nightfly

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Posted 19 June 2013 - 06:01 PM

I use a fork mounted 8" SCT (permanently mounted) as my piggyback platform. I have performed exposures beyond 60 minutes with no field curvature and a few in the two hour realm without problems.

Because many areas I photograph are ideal at the meridian, this setup does not require a meridian flip as does german equatorial mounts.

The 8" SCT also functions well as a guide scope. I've routinely managed the big Pentax 67 and 300mm lens in any position in the sky and lenses as big as 400mm if shooting near the meridian at low to medium angles.

Take the tour.....

http://www.flickr.co...57626760790621/

Jim




http://nightflyphoto...y.blogspot.com/

https://www.facebook.com/Nightflyastro

#7 Nebhunter

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Posted 21 June 2013 - 12:57 PM

I'm not going to suggest any mount for you other than to declare that the fork mount offers many advantages for astro photography compared to equitorial. I've watched Jim work his mount especially near zenith. Nice.

My other suggestion is to consider the typical considerations for any mount. Whatever the visual limit is - eg: 30 lbs load, then divide it in half for astrophotography = 15 lb load.

If you can - buy a larger mount now and the best you can afford. It will simplify your astro life. I cannot tell you how many of us have gone thru 2 or 3 mounts upgrading as we got further into the hobby. So the wasted money and time doing that is not the way to go if you can avoid it.

I used an Atlas or EQ6 for a couple of years. It's a very good solid mount and they have made improvements over the years specifically periodic error and using a better saddle system. I did 45 minute exposures manually guided back then with no issues using a tripod and a quick drift alignment procedure.

Hope the helps and don't loose too much sleep over the mental anguish you are headed for. But I do suggest you make a chart with a list of items for each mount so you can make proper comparisons. If you try to keep track of everything mentally - you will end up there. :)

igor

#8 Madratter

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Posted 25 June 2013 - 11:47 AM

Fork mounts do have an advantage in that they do not need to meridian flip. On the other hand, getting ones that are really good for astrophotography isn't easy (equatorial wedge that doesn't vibrate like crazy, low PE, guides well in both axis).

One advantage of GEMs (besides more availability of good ones) is that they are easier to get your equipment balanced properly.






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