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#1 divers

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Posted 22 February 2009 - 11:05 AM

I am sure this has been asked, but hey....one more time...

Just got my CGEM from Astronomics...went to put my C11 on it and found out the rails do not fit. The dovetail does not seem to be deep enough to fit into the mounts saddle. So....someone please tell me where to get a proper dovetail so I can use this beautiful mount.

Robert

#2 mclewis1

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Posted 22 February 2009 - 01:04 PM

The CGEM saddle is a Losmandy D compatible saddle, so just about anything labeled Losmandy or Losmandy D or CGE will fit. The vendors who make these are Losmandy (of course), ADM, Baader, Celestron, and many others. What you don't want is anything that is "vixen" or CG-5 compatible.

That said there are a some variables, unfortunately some vendors have machined dovetail rail/plates (the bigger D compatible ones are often called plates instead of a rail) in sizes that can be a problem in other vendor's saddles. Generally you won't go wrong with a "real" Losmandy D plate or one from a good quality vendor such as ADM.

What is on your C11? Something in the back of my mind reminds me that there was something "funny about the saddle on LXD650s ... but I'm not certain about that. I no longer know anyone who has one that I can check with.

#3 Dave H.

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Posted 22 February 2009 - 02:02 PM

You might consider this adapter from ScopeStuff. This is what I have on my CGEM, and allows your CGEM to accomodate use Vixen/CG5 dovetail rails like the one on your C11.

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#4 mclewis1

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Posted 22 February 2009 - 02:50 PM

Robert,

Can you provide us with a picture of your current C11 rail and how it attaches to the LXD650?

It turns out that there are a variety of ways to attach a scope to an LXD650, and most likely as Dave is assuming is that your C11 has a vixen compatible rail on it (a vixen compatible rail is 1.75" wide at it's widest point). If this is true then you have a few options.

Add a vixen compatible adapter to your CGEM ... as Dave mentioned Scopestuff has an nice SS_TV2 adapter for $89, ADM has a LOS-VIX for $99.

The other approach that I was suggesting in my earlier post is to replace your existing rail (whatever it is) with a Losmandy D plate (Losmandy DC11) which is available for $95-100.

The adapters won't require any extra work (if your existing rail is really a vixen compatible one) and are a few dollars cheaper. The new plate will be more solid and will put the scope a bit closer to the mount (less counterweight required).

Personally I think a vixen rail on a C11 is ok for visual work but doesn't make sense for imaging, especially if you're going to piggyback a refractor on the C11 as well ... it's just not stiff enough to prevent any flexing with all that weight on it. The larger Losmandy D plates will support quite a bit more weight without any flexing.

#5 divers

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Posted 22 February 2009 - 02:58 PM

I have a full length d style with radius blocks on my C11. When I had my LXD I used an ADM saddle. The CGEM saddle is different. The plate is the long one in the picture.

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#6 mclewis1

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Posted 22 February 2009 - 03:23 PM

Robert,

Thanks for clearing that part up ... there's obviously no need for any rail/plate 101 discussion.

So your Losmandy D plate doesn't fit well in the stock CGEM saddle ... hmmmm, this is interesting. All the initial reports on the CGEM were that the saddle looked and measured like any other Losmandy D compatible saddle. For comparison the existing CGE (not CGEM) saddle works fine with the Losmandy D plates.

Any chance of a picture of the miss match with your setup?

I do know that Celestron CGE rails and Losmandy D plates are slightly different, the sides of the CGE rail are indeed a bit "deeper". The CGE rail also tends to fit slightly loosely in real Losmandy D saddles but that the ADM D saddles by the nature of their design have enough latitude to handle this, so perhaps the CGE rail is also going to be the one that fits the best in the CGEM's saddle.

It is likely that the quickest fix for you is to use the real orange Celestron CGE rail (they are one piece with no radius blocks) for your C11.

#7 divers

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Posted 22 February 2009 - 03:50 PM

please notice the gap under the plate.

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#8 mclewis1

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Posted 22 February 2009 - 05:25 PM

Robert,

Is the whole angled side of the dovetail in contact with the angled side of the saddle?
Is the lower area of the plate (where the holes are in your picture ... just above the angle side of the dovetail) in contact with the topside of the saddle?

If yes to both questions then I think you are fine. Yes that's a pretty big gap under the plate but some gap is not unusual and if the whole angled side of the dovetail is in good contact (on both sides) with the saddle then that is the most holding power the saddle can exert on the dovetail. The dovetail plate resting on the bottom of the saddle doesn't provide any holding power.

Sure having a dovetail that is in contact with the whole saddle side plate would provide more piece of mind but I don't think it would be any more solid. You will have to ensure that the dovetail is properly seated in the saddle before tightening it down and moving the mount but I don't think that is any different than anyone else with a big scope and a Losmandy D plate.

This picture is my C11 with it's Losmandy DC11 mounted on a CGE saddle. The sides of the dovetail and the saddle line up well but there is a gap under the plate ... in my case it's just a bit more than 1/16".

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#9 mclewis1

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Posted 22 February 2009 - 05:26 PM

And the shot of the actual gap ...

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#10 Dave H.

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Posted 22 February 2009 - 05:38 PM

My bad. :foreheadslap:

Obvious poor assumption that you had a CG5 dovetail rail as so many C11s are sold with this rail. Frankly I am very surprised and would have never guessed you were using a Losmandy d series dovetail. I have always understood the conventional widom to be that the Losmnady and CGE dovetails are 100% compatible. So much for conventional wisdom. :tonofbricks:

I'm still very confused. :confused:

I totally agree with the previous post that on a C11, a CGE or Losmandy dovetail fit right to the saddle would be far more secure than an adapter. On my lighter tubes that all have CG5 type rails including the F8 6" achro the adapter works OK, but this is certainly a totally different problem, and one I would have never anticipated. Keep us posted on your solution, and good luck.

#11 mclewis1

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Posted 22 February 2009 - 05:40 PM

Robert, In looking at your picture some more I think one of the differences is that the CGEM saddle appears to be cast and the CGE saddle has been machined so it looks like there is better contact in the CGE saddle. The issue seems to come down to whether the CGEM saddle sides are smooth enough to ensure good contact with the angled sides of the dovetail so that the top of the CGEM saddle jaws fit high up into the angled "corner" of the dovetail.

I think I'd experiment with the D plate and CGEM saddle and see where the saddle would "let go" of the plate. See just how much the saddle has to open before the plate can slip out. That may help your piece of mind. If it's close and you're still uncomfortable with the setup then I think the CGE plate in place of the Losmandy plate will be the way to go. Either that or replace the CGEM saddle but I don't think that is an option from any vendor ... yet.

#12 divers

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Posted 22 February 2009 - 05:51 PM

I have some thinking to do. Thanks for all the replies.

#13 Lane

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Posted 23 February 2009 - 12:56 AM

Divers - I have a Losmandy D Plate on my C9.25 and it mounts exactly the way you show in your picture with a gap underneath. That is just how it fits and it works fine. I don't think having it touch the bottom of the saddle is going to add anything except maybe more weight. But if it really bugs you, just wait, because it won't be long now before ADM and others create a replacement saddle for the CGEM. It is just still to new right now, but all the kinds of replacement parts you can get for the Sirius and Atlas will be coming for the CGEM too.

#14 divers

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Posted 24 February 2009 - 02:46 PM

Well...after using the CGEM a couple times....the standard d style rail gives me the heeby-jeebies. The CGEM saddle just barely has enough to hold onto. I am suprised more have not seen this issue. My next step is to email Anthony at ADM and see what he has. BTW - the mount rocks. I did a very careful alignment the other night. I place my 12mm reticle eyepiece and slewed to Rigel...centered it precisely (just a tad off) and left for 1.5 hours...when I cam back was still centered (albeit just a tad off).

#15 chollman

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Posted 24 February 2009 - 03:17 PM

Doesn't anybody where you bought the mount have any suggestions? I was thinking of buying the cgem for my 8" newt. I will run into the same problem.

#16 divers

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Posted 24 February 2009 - 03:20 PM

Spoke with Astronomics...Celestron does not sell the CGE rail seperately. I am sure Anthony will be making something soon....he always seems to fill the niche.

#17 chollman

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Posted 24 February 2009 - 03:31 PM

Not to be too critical, but should Celestron sell this mount without a mounting plate or rail? Do they expect us to make one ourself? That is a pretty important part for them not to supply. Borderline rediculous to me.

#18 jrcrilly

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Posted 24 February 2009 - 03:43 PM

Not to be too critical, but should Celestron sell this mount without a mounting plate or rail? Do they expect us to make one ourself? That is a pretty important part for them not to supply. Borderline rediculous to me.


The mount manufacturer has no idea what type of optical tube will be installed - and thus no idea of the kind of dovetail rail (length? radius blocks? flats for rings?) the user will need. Takahashi and Astro-Physics don't provide rails (or even saddles) for this reason but nobody seems to complain. It'd make more sense to blame those OTA manufacturers who don't provide a rail of letting the customer down - but, of course, there are two very common dovetail sizes and the OTA manufacturer doesn't know which you'll need for your mount.

Whatever type of rail is required for a given optical tube, it is readily available from the usual sources - primarily Losmandy and ADM. By the way - Losmandy doesn't include a rail with their mounts, either.

#19 divers

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Posted 24 February 2009 - 03:47 PM

I have to agree with John. I "think" the OTA being supplied on the CGEM "kits" probably have rails that fit well. Anyone want to buy a nice d-style rail :)

#20 chollman

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Posted 24 February 2009 - 03:53 PM

Divers said he didn't like the fit of the Losmandy 'D' plate. I have not seen a reasonable answer here. Do you have to jump through several hoops or spend way too much? I have a 70" long tube 10" diam. about 22 pounds in weight. What plate can I attach my rings to that won't make me worry about a proper fit?

#21 divers

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Posted 24 February 2009 - 04:08 PM

...that's the "problem" with buying something new to the market....growing pains!

#22 chollman

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Posted 24 February 2009 - 04:12 PM

Ouch!! I think I'll wait a while.

#23 Lane

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Posted 24 February 2009 - 07:25 PM

Divers, I still don't see why this is a problem. My Losmandy bar on my 9.25 fits the same as yours. My ADM D to V adapter also fits the same way. And I have no intention of replacing anything. As long as it holds and it sturdy why worry about it. I put my 9.25 on my CGEM and lifted the entire setup by the dovetail bar just to see how strong it is and I don't think you could knock it out of that saddle with a hammer. But if you really don't like it then the best solution is to replace the saddle not the dovetail. If you replace the saddle then every other dovetail you buy will also fit the way you want. So if you can just wait a little while someone like ADM will create a replacement saddle for the CGEM. Most mounts have replacement aftermarket saddles available the CGEM is still just to new.

#24 divers

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Posted 24 February 2009 - 08:18 PM

Lane -

Personal preference. The rail that comes with the OTA that actually comes with a CGEM in the kit is different from the d style. It is indeed a little deeper and fits better.

#25 Lane

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Posted 24 February 2009 - 08:49 PM

I have the standard celestron cge type bar on my C11 and my C8. They do go a little deeper into the saddle but there is gap under them as well they don't touch the bottom of the saddle either.






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