Celestron 94216 Dovetail ... C8 to CG5 ????
Posted 02 October 2012 - 08:00 AM
Celestron has dovetail #94216 :http://www.celestron.com/astronomy/celestron-8-inch-dovetail-bar-cge.html
That page is terrible at describing the product:
- It does not tell what it is used for
- The text is focused on what it does not fit
- It does not describe the product dimensions
- The support page links to a dimensioned diagram that does not include:
- The screw hole dimensions for the distance between the holes on one end of the OTA
- The size of the dovetail
It sorta looks like it would fit both the C8 & the CG5 mount but I don't find anything that indicates it will work and some indications that it may not work.
QUESTION: Will the 94216 fit on the C8 & fit the CG5 mount?
- The Screw hole spacing on one end of the OTA is 1.75"
- The Dovetail dimension needs to 1.75"
Thanks in advance,
Posted 02 October 2012 - 08:32 AM
Can you describe why it does not fit? What is different?
Posted 02 October 2012 - 08:48 AM
Posted 02 October 2012 - 09:12 AM
With these you can see the difference.
When looking at the Celestron dwg of 94216 it is hard to determine the rail dimension (especially since it is not dimensioned on the print)
Posted 02 October 2012 - 09:13 AM
You need a "Vixen" size dovetail bar. This is just a piece of machined metal that screws into your C8 and has a rail for the clamp on your CG5 mount head to grab. The clamp on a stock CG5 is sized for the "Vixen" size bar.
You can buy the proper sized product at Scopestuff see here: Scopestuff dovetail for C8
The product #MDC8 is what you need. $79 including shipping. This dovetail bar comes with a mounting bracket that attaches to the bottom of the C8 like a rectangular ruler and the dovetail then screws onto that. All the screws are included. Its rather easy to do.
Posted 02 October 2012 - 09:29 AM
Or, get some aluminum plate and build an adapter which becomes an issue of "money" or "effort". :-)
Posted 02 October 2012 - 09:53 AM
Posted 02 October 2012 - 06:27 PM
Posted 09 October 2012 - 01:47 PM
Posted 10 December 2012 - 09:58 AM
That's all i can say about those dovetails...Mine ordered was the 84217, the one to fit the c9.25. Well, no they don't fit. The dovetail is about half an inch too short.
I know it's because the newest c925 are sligtly longer than the pre-2004 c925, but still...it doesn't take a genius to understand that some old cg5-c925 users might want to upgrade their OTA to a losmandy-type mount.
Half an inch....in terms of engineering, i don't know how to call that.
Well, that or the saddle. The cgem saddle can adapt to smaller width than the standard losmandy width, but not as narrow as a vixen width. And since their is no intermediary between losmandy and vixen, i don't see the point of a saddle that can adapt to slightly narower losmandy-type dovetails, but not to Vixen type.
If i can't return it, I thought i would cut my new cgem compatible dovetail in two, drill holes near the end to screw some steel and fill a gap for about 1/2 inch. Nobody has done that?
Posted 10 December 2012 - 12:05 PM
Posted 10 December 2012 - 12:33 PM
About the bar for the 11', its curvature wouldn't fit the c925 ota.
I guess i'm gonna stick to my current solution: a losmandy piggyback plate and ring system that i never used for its intendded purpose (too heavy for a c925-cg5) until i realized i could use the plate and adaptors in place of my vixen-type dovetail.
Posted 10 December 2012 - 04:20 PM
When the GP-C8 was introduced the dovetail and saddle assumed the current missionary position we all know and love. The Vixen provided 1.75" wide dovetail had a 2.5" wide flange that ran the length of the bar, fit the curvature of the front and rear cells and provided fitment points for the 1.75" spaced counterweight bracket holes.
After the GP was dropped in favor of the CG-5 Vixen continued to supply the dovetail bars for a while. Then Celestron found a cheaper bar without the flange. To use it they had to replace the counterweight holes with two drilled closer together. Some tubes have just the two close holes others have both sets of holes. Like dimensioned lumber, the nominal 1.75" wide bar shrunk to 1.7" and is now called the univeral mounting bar.
Losmandy's D bar is 3" wide. Celestron's CGE/CGEM bar is about 0.125" narrower, but the CGEM saddle will accept the Losmandy bar. I've milled adapters to fit the 13" universal bar on C8s, but have found it easier to buy the Orion Atlas 3" saddle, machine off the bottom flange, bolt a short length of 1.7" bar to it and fit 3" D or CGE bars to may scopes. The Atlas adapter then converts any 1.7" saddle to a 3".
Machining an C8 dovetail bracket from 5/16th plate.