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C-8 fork adapted for side by side imaging

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#1 Brian Risley

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Posted 11 March 2009 - 09:35 PM

Here are a couple of shots of my latest project. Taking a C-8 OT fork setup and making a side by side mount for a Cometron 80mm f5 refractor and C-90. The 80mm is for imaging with the C-90 for guiding. This was made from several aluminum angle bracket pieces (covered with black felt).
This fork is from my 1972 C-8 that was rebuilt. I recently picked up a new 'old style' fork that is like the original fork that came with the scope. I had this drive base changed by Celestron in 1979 due to problems with the RA lock.
I am waiting on a motor to arrive to get the dec fully motorized for guiding. I utilized the counterweight bar weights from my 1980 C-8 to help offset the weight (I may tap the weights to allow threading in the older threaded C-8 counterweights, as imager/diagonal add more top weight.) The C-90 is mounted using a Celestron Precision Slow Motion Adapter for guide star centering.
(Now I need another tripod/wedge :)
Brian

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#2 Brian Risley

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Posted 11 March 2009 - 09:36 PM

Image #2

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#3 johnfdean

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Posted 12 March 2009 - 03:11 PM

Neat. But this rasies a question. What is the weight limitation on the fork?

#4 Brian Risley

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Posted 15 March 2009 - 01:07 AM

Well, the counterweights were meant for the C-8 that was on this fork, so I don't think that the weight issue will be too big a deal. I used the forks with the C-8, counterweights, C90 with an OM-1 and tangent assembly, so I think the forks can handle it. Just mounted the Hankscraft motor for the Dec axis, looking at what it will take to make the drive corrector interface to a GPUSB. Seems pretty simple, 4 single pole double throw relays, a 100K pot and a 400k resistor. The Celestron controller is a lot easier to do than my other drive corrector, which is an original Meade unit that is joystick controlled and hard wired. I also have an old Willman Bell Gemini Twin Track that has a broken joystick, I will have to see if I can get it to operate with pushbuttons. If I can, then I can use it too.
Brian

#5 Kaizu

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Posted 15 March 2009 - 10:23 AM

I just wonder if the crossbar could be turned around, so that the centerlines of the scopes were nearer the declination turning center line. Maybe the system would work without the counterweight. I think that the heavy counterweight on so thin rod may cause vibration problems.

Kaizu

#6 Brian Risley

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Posted 17 March 2009 - 12:21 AM

Kaizu,
Yes, it does work better turned around! Thanks. Have to test on a fork with imager on so I can see what weights I do need, may just have to make a mount for my smaller screw based weights that I can have travel the shaft/rotate for best balance.
I replaced the dec part of the WB drive corrector joystick with a 10k multi-turn trim pot and 2 switches. I also adjusted the internal RA offset, so I think it is working now! Have to wait for some clear skies to test.
I think I have all the details needed to make the Celestron drive corrector GPUSB interfaceable.
Brian






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