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Repurposing a Fork Question

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#1 Starhawk

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Posted 06 April 2009 - 12:47 AM

I am considering getting an old Celestar Delixe mount to dismount the OTA, and then fabricateva trapeze mechanism to serve as a support for for small refractor and reflector scopes for astrophotoghraphy. I feel like I don't need the computer capabilities of the usual mounts, and I like the idea of being able to run for extended periods of time on a couple 9v batteries. All in all, I am thinking relatively light mount, no car batteries to lug, and good enough tracking for up to 500mm focal length images with 45- 60 second exposures.

Has anyone out there tried doing this? Are there terrifying gotcha details I am neglecting? Thank you for anything you can add.

#2 JAT Observatory

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Posted 06 April 2009 - 07:09 PM

I think your biggest hurdle will be get the balance correct.

#3 Eddgie

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Posted 06 April 2009 - 09:29 PM

Get an old Polaris mount with RA drive. This drive runs for hours on a single 9V Battery. It will be far more stable than a wedge mounted fork, and lighter to boot.

#4 AlienFirstClass

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Posted 07 April 2009 - 12:13 AM

I am considering getting an old Celestar Delixe mount to dismount the OTA, and then fabricateva trapeze mechanism to serve as a support for for small refractor and reflector scopes for astrophotoghraphy. I feel like I don't need the computer capabilities of the usual mounts, and I like the idea of being able to run for extended periods of time on a couple 9v batteries. All in all, I am thinking relatively light mount, no car batteries to lug, and good enough tracking for up to 500mm focal length images with 45- 60 second exposures.

Has anyone out there tried doing this? Are there terrifying gotcha details I am neglecting? Thank you for anything you can add.


I would like to see what you come up with...I too have a SCT mount that I would like to reuse.

#5 ibase

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Posted 07 April 2009 - 04:24 AM

Sometime back I deforked my old original Nexstar 8 OTA to use on another mount. I attached a Vixen type dovetail to the old mount:

Posted Image

Now I can mount my ST-80 and also a coming WO 102ED or any scope with a Vixen-style dovetail on this old mount.

Best,

#6 Starhawk

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Posted 07 April 2009 - 03:48 PM

Thank you to everyone for the feedback. I have a couple of avenues I am going to continue on:

On the fork question, I am dropping the Celestar conversion, largely since it costs more to buy (ahem, a reason to think about that came up Monday) and still won't be as good as the NexStar 8 GPS I already own- I will just have to buck up and tote a battery or make sure I can park nearby. The conversion will use a carbon fiber structural tray I made using a cheap rectangular cake pan as a tool. I'll need to make adapters for the fork arms, and have already been making vixen dovetail clamps. I will be sure to post pix when it is together.

On the mobile battery powered mount, I already have a Vixen Polaris I adapted to CG-4 motors on both axes with a 10:11 gearing ratio change to go from the speed for the 130 tooth CG-4 motors to the speed for 144 tooth Vixen worm. However, it has fairly large periodic error at close to 80 seconds, peak to peak sinusoid movement, so I am planning to incorporate a mechanical first order drive corrector. I have already modified the mount for having a vixen dovetail clamp and a new lattitude adjuster (the original collapsed). It's a good mount, but putting two tubes on it seems to be a stretch. It does look really good with my white tube C5 on it- it would seem Celestron missed a match made in heaven, there.

I'll let you know how that goes.






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