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Best GO-TO GEM under $1500

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#1 chitown

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Posted 23 February 2009 - 08:58 AM

So guys, I was wondering if I should seek expert advise from you regarding my future purchase: a gem!

Here is what my equipment will look like:
1. Orion 110mm Refrector (main scope)
2. Orion ST 80mm (guide scope + orion guider)
3. Orion short finder scope
4. Meade Deep Sky III CCD

The purpose of this setup is astrophotography.

What in your eyes is a good go-to mount under $1500 that can hold all this equipment and be reliable for years to come?

ALSO: Why do some people use a "dovetail" type setup? What advantages do one get from it? (Sorry if my question is too stup!d, as I have never seen a gem in my life and gathering all information via this forum!)

Thanks!
:question:

#2 rmollise

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Posted 23 February 2009 - 10:00 AM

The purpose of this setup is astrophotography.

What in your eyes is a good go-to mount under $1500 that can hold all this equipment and be reliable for years to come?

ALSO: Why do some people use a "dovetail" type setup? What advantages do one get from it? (Sorry if my question is too stup!d, as I have never seen a gem in my life and gathering all information via this forum!)

Thanks!
:question:


The best? For my money, it's a tossup: The Orion Atlas or the Celestron CGEM (very similar, made by the same company).

All except the smallest GEMs use a dovetail mount. Why? It allows the telescope to be easily removed, and allows numerous telescopes to use the same mount just by installing the requisite type of dovetail adapter.

;)

#3 ragebot

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Posted 23 February 2009 - 10:02 AM

Short answer is the Atlas from Orion. It seems to be the choice budget mount. My main reason for the Atlas choice is it is quite capable of supporting a larger OTA than you currently have, and no one ever complains about a scope being over mounted.

Dovetail is a rather generic term, like car. Just as a car can be a Yugo or a Rolls Royce you can get dovetails of different sizes and quality.

Sometimes a dovetail is called a plate. It is bolted to the OTA, or telescope, and then attached to the mount via a clamp like device.

While not always the case the term dovetail is often associated with the Losmandy style dovetail which is bigger in size, and sometime better quality, than the perhaps the more common Vixen-c style plate, which is sometimes also called a dovetail. There are also other styles of plates or dovetails.

Some "advantages" of using a dovetail include the ability to easily balance the OTA on the mount and the ability to quickly and easily set up and break down the OTA from the mount.

#4 Dave H.

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Posted 23 February 2009 - 12:27 PM

Chitown,
Here is a photo of my CGEM mount. As you can see, the dovetail is mounted in the mount's "saddle", and the optical tube's mounting rings are mounted to the dovetail. As you can easily surmise when in use the optical tube is rested inside the mounting rings and secured in place with light tension on the rings.

Hope this helps explains how these pieces all work together.

I can't argue with either of the previous posts having owned both the CGEM and Atlas, these are the best mounts in the sub $1500 price range. I am partial to the features of the CGEM, but these mounts are both made by Synta and are very similar, and the Atlas has a very large and loyal following.

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#5 ragebot

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Posted 23 February 2009 - 01:02 PM

The only reason I did not include the CGEM is it is much newer than the Atlas.

There is no reason to suspect that the CGEM is any less durable than the Atlas, but all new products by definition do not have a record of how durable they are.

Still I did just get an iOptron MiniTower, knowing full well it does not have a record, good or bad, for durability. I would also mention the CGEM has newer and probably better software.

#6 Al Canarelli

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Posted 23 February 2009 - 04:42 PM

If money is no object, go with the CGEM. However, it you don't truly mean those words, and money does carry some weight, then I would go with a Celestron Advanced Series GT. The cost of this mount is only $599, so why go overkill if the CG5GT will do the job?

Both of your telescope weigh in at 12.5 pounds. Add another pound for the guide camera, 1 pound for the rings and another 2 pounds for the main camera. That brings you to about 16 to 17 pounds total load. This is all well within the load limit of the CG5GT.

#7 ragebot

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Posted 23 February 2009 - 08:04 PM

If money is no object, go with the CGEM. However, it you don't truly mean those words, and money does carry some weight, then I would go with a Celestron Advanced Series GT. The cost of this mount is only $599, so why go overkill if the CG5GT will do the job?

Both of your telescope weigh in at 12.5 pounds. Add another pound for the guide camera, 1 pound for the rings and another 2 pounds for the main camera. That brings you to about 16 to 17 pounds total load. This is all well within the load limit of the CG5GT.


Then add another how many pounds for the counter weights to balance the 16-17 pounds and you have a load of probably close to 30 pounds that the motors and gears have to move around often in temps that makes the lube not work as well as it could. It is much easier to do a good job with a big mount and a small OTA than a small mount and a big OTA.

I would always pick a bigger mount given the choice.

#8 Rusty

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Posted 23 February 2009 - 08:10 PM

In between the Atlas EQ-G/CGEM and the AS-GT is the Sirius EQ-G - I rally like mine, and 17 lbs is no sweat.

#9 Greg S

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Posted 23 February 2009 - 09:00 PM

I've never used either mount but if the CGEM uses a losmandy style saddle then go with that mount. The narrower vixen style saddles and dovetails flex too much with imaging which is my experience from using an old GPDX.

#10 Domerman

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Posted 23 February 2009 - 09:18 PM

I think you should consider transportation in your quest for a gem mount. I am also considering something in the sub $1500 range and what I realized is that there is a huge weight increase from a CG5 and Sirius EQ-G (about 40 lbs each) to a CGEM and Atlas EQ-G (about 75 lbs each). Of course, the latter choices allow for much more stuff to be mounted and allow for greater expansion in the future. However, I do not plan on buying a really hefty mount until I am able to buy an observatory in the very distant future.

#11 PGW Steve

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Posted 23 February 2009 - 09:31 PM

A 110 and an 80, get the Atlas or the CGEM...I have an Atlas/EQ6 and love it. I like the freshened up CGEM but I'll wait for others to beta test it first. The Atlas has a long list of happy users and a proven track record, that was important to me when I purchased mine.

#12 watcher

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Posted 23 February 2009 - 10:14 PM

I really like what I read about the CGEM, but the Atlas can use EQ-MOD, and the CGEM can't. So, pick your poison.

#13 Al Canarelli

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Posted 23 February 2009 - 10:43 PM

Then add another how many pounds for the counter weights to balance the 16-17 pounds and you have a load of probably close to 30 pounds that the motors and gears have to move around often in temps that makes the lube not work as well as it could. It is much easier to do a good job with a big mount and a small OTA than a small mount and a big OTA.
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Wait a minute! My understanding is that a listed payload does not include counter weights. So at 16 or 17 pounds total payload, one is well below the listed payload of the CG5GT mount. Now if you feel more at ease with a larger mount at about 3 times the cost, go for it. But why advise others to spend their money as you spend yours?

#14 ragebot

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Posted 24 February 2009 - 03:09 AM

Then add another how many pounds for the counter weights to balance the 16-17 pounds and you have a load of probably close to 30 pounds that the motors and gears have to move around often in temps that makes the lube not work as well as it could. It is much easier to do a good job with a big mount and a small OTA than a small mount and a big OTA.
============================================================
Wait a minute! My understanding is that a listed payload does not include counter weights. So at 16 or 17 pounds total payload, one is well below the listed payload of the CG5GT mount. Now if you feel more at ease with a larger mount at about 3 times the cost, go for it. But why advise others to spend their money as you spend yours?


I am not claiming you have to add the weight of the counter weights to the listed payload; just that the motors and gears have to be able to move all that weight around.

I have a LDX55 mount and an iOptron MiniTower, both of which are capable of using with my ED80, and in fact the LDX55 came with my AR5. But there is a real difference between how stable the AR5 (or the ED80) is on the Atlas or the other two mounts.

My experience is that money spent on a big mount is money well spent.

#15 RogerRZ

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Posted 24 February 2009 - 05:57 AM

Then add another how many pounds for the counter weights to balance the 16-17 pounds and you have a load of probably close to 30 pounds that the motors and gears have to move around often in temps that makes the lube not work as well as it could. It is much easier to do a good job with a big mount and a small OTA than a small mount and a big OTA.
============================================================
Wait a minute! My understanding is that a listed payload does not include counter weights. So at 16 or 17 pounds total payload, one is well below the listed payload of the CG5GT mount. Now if you feel more at ease with a larger mount at about 3 times the cost, go for it. But why advise others to spend their money as you spend yours?


I am not claiming you have to add the weight of the counter weights to the listed payload; just that the motors and gears have to be able to move all that weight around.

I have a LDX55 mount and an iOptron MiniTower, both of which are capable of using with my ED80, and in fact the LDX55 came with my AR5. But there is a real difference between how stable the AR5 (or the ED80) is on the Atlas or the other two mounts.

My experience is that money spent on a big mount is money well spent.




Those weights actually make life easier on the motors. That's what counterweights are for.

That being said, EQ6 all the way. At this price, nothing else comes close...

#16 chitown

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Posted 24 February 2009 - 08:56 AM

Thanks guys.

Dave: Thanks for posting the picture.

I think I might lean towards Atlas. Does any of you have GPS module with it?

#17 ragebot

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Posted 24 February 2009 - 10:03 AM

Thanks guys.

Dave: Thanks for posting the picture.

I think I might lean towards Atlas. Does any of you have GPS module with it?


I do. There is another thread that addresses this issue and it got rather testy.

I think it dose just fine; but some peeps dont think it is cost effective. :question:

#18 Al Canarelli

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Posted 24 February 2009 - 10:28 AM

I am not claiming you have to add the weight of the counter weights to the listed payload; just that the motors and gears have to be able to move all that weight around.
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Counter weights make it easier for the motors to move all that weight around. If your bedroom windows were not counter weighted, you wouldn't be able to open them. I once read that a huge telescope in an observatory is turned (and relatively quickly) by a tiny motor (just a few HP). We're talking hundreds of tons here. The only reason the small motor can do this is because the observatory is counter weighted and finely balanced.

You then say, "My experience is that money spent on a big mount is money well spent." To which I say...maybe. The problem is, which mount is big enough and at what point is it too big?

#19 rmollise

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Posted 24 February 2009 - 10:53 AM

You then say, "My experience is that money spent on a big mount is money well spent." To which I say...maybe. The problem is, which mount is big enough and at what point is it too big?


The only answer? "It depends." The CG5/LXD75 are _fine_ for imaging with a C8 with a guidescope (even an 80mm guidescope) mounted. For visual, you can even put a C11 on there. But for much beyond a C8, yeah, the Atlas is the way to go. I have also found the Atlas to be more consistent...a little wind...or not quite correctly balanced and the Atlas don't care. The CG5 will sometimes serve up oblong stars under those conditions. That said, I've taken a lot of pictures with the CG5 and continue to use it since it usually delivers the goods with what I use on it...the C8 at f/4 with an ST2000...and it's so easy to schlep around... :lol:






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