Posted 22 February 2009 - 11:05 AM
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.
Posted 22 February 2009 - 01:04 PM
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.
Posted 22 February 2009 - 02:02 PM
Posted 22 February 2009 - 02:50 PM
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.
Posted 22 February 2009 - 02:58 PM
Posted 22 February 2009 - 03:23 PM
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.
Posted 22 February 2009 - 03:50 PM
Posted 22 February 2009 - 05:25 PM
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".
Posted 22 February 2009 - 05:38 PM
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.
I'm still very 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.
Posted 22 February 2009 - 05:40 PM
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.
Posted 22 February 2009 - 05:51 PM
Posted 23 February 2009 - 12:56 AM
Posted 24 February 2009 - 02:46 PM
Posted 24 February 2009 - 03:17 PM
Posted 24 February 2009 - 03:20 PM
Posted 24 February 2009 - 03:31 PM
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.
Posted 24 February 2009 - 03:47 PM
Posted 24 February 2009 - 03:53 PM
Posted 24 February 2009 - 04:08 PM
Posted 24 February 2009 - 07:25 PM
Posted 24 February 2009 - 08:18 PM
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.
Posted 24 February 2009 - 08:49 PM