What options are there to attach a 80mm refractor piggy back to a C9.25?
Well I'm smiling! I recieved an unepxected payout from a job I did 5 years ago - just the right amount to purchase a Celestron 9.25" Carbon Fibre OTA with XLT.
I plan to use it to replace my 5" MAK, and I want to connect a Williams Optics 80mm Megrez to it.
I wish to set it up piggy back, but I notice the C9.25 OTA has a dovetail plate that runs the whole length of the tube. So what options do I have?
What fittings do I need as I'm unsure if the C9.25 has any pre-machined threads for a piggy back OTA, nor how you'd fit mounting rings given the obstruction of the dovetail plate?
Suggestions anyone, I want to look like this, but with the C9.25 instead of the MAK.
The C9.25 CF XLT should ship with the (wider) CGE dovetail mounting rail, not the (narrower) Vixen one. Therefore, your mount will require a Losmandy style saddle plate to accept the 4” wide (3” dovetail) rail.
There are also mounting holes on the top of the corrector cell and rear mirror cell. I believe that Losmandy sells a mounting plate for the C9.25 - see here: http://www.losmandy.com/secondary.html#DC
Then, you add Losmandy rings and that should do the job.
Thanks - You can apparently order the C9.25 in Carbon Fibre with a narrow CG5 rather than the wide CGE mounting plate.
Can you clarify something for me when you said "There are also mounting holes on the top of the corrector cell and rear mirror cell", can I read this that there are mounting holes on both the top and bottom, at the front and the back of the OTA (4 threaded holes not two - all strong enough to be weight bearing?)
If this is the case its simplicity to attach what I have and desire to the CG5 and piggy back it as per my photo above - you just need the right sized bolts in stainless steel to go into the thread and run this thru the bar I already have holding the Megrez.
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I was alternately think get 10 or 11 inch mounting rings with 3 screws and pads and attach this over-size rings to the C9.25 above and around its dovetail plates.
I definitely want to avoid the saddle plate if that is what connects two OTAs to a flate plate which in turns attaches to the mount - I just don't like the look of them (ascetics) and I want to keep everything piggybacked.
Finally the Losmandy range looks extensive - but of the 50 things on that page I'm unclear which I need? The DC9.25 I guess - but its just another dovetail plate like the CG5s, it doesn't get the piggyback going for me.
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A final option may be to get two 9.25 rings, drill through them top and bottom and thread the top, then remove the right size dovetail, attach the rings and reattach the dovetail through the rings, then use the threads at the top of the rings to attach the Megrez using the bar I already have.
But that picture infers that the C9.25 does have load bear bolt threads top and bottom, front and rear - so perhaps that gives me all I need right out of the box!
Bottom of OTA:
The Vixen and CGE style dovetail mounting rails are attached via 3 holes; a single drilled/tapped hole on the corrector cell and two drilled/tapped holes on the mirror cell. The single front hole is a larger diameter than the 2 rear holes.
Top of OTA:
There are 4 drilled/tapped holes; 2 on the corrector cell and 2 on the mirror cell, all the same size.
I fitted a 4mm thick, 3” wide aluminium bar to the top 4 holes (2 front, 2 back) and mounted my WO 80mm ED on there using the WO 90mm rings but exceeded the weight specs for my mount so I never used this combo in anger. It certainly seemed rigid enough.
I then fitted a brass door handle to the top plate for lifting and carrying the OTA but I have since removed the handle as I felt it might have been upsetting the collimation by mechanically stressing the relationship between front and rear cells. This was a nervous Nellie reaction - not based on rational thought so take it with a large pinch of salt.
Note that there are pairs of holes available on the side of the OTA cells too, but only those holes with a cross head screw are available. Holes blanked of by grub screws should not be fiddled with unless you know they were made for use by the user. Otherwise, something may fall off inside the OTA.
From memory, the finderscope holes may be blanked off by grub screws?
Ah, very good Dennis, forgot that was in the background. lol
Hadn't thought of formal attaire in the dome, there is also a table in there for Champer's and biccies
It is actually there to hang my old heavy observing coat, in the warmer months it is fine to observe and image in short sleeves up to about 0100 but after that it starts to get a bit cold, saves throwing it in one of the bins, it just hangs there and looks out of place.
