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Finally finished De-Forking the ETX90

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#1 Don Taylor

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Posted 26 May 2013 - 05:43 PM

Finally finished de-forking my original (non go-to) ETX90. It has excellent optics. I bought it new for ~$200 just after the go-to versions came out. I've been frustrated by the original RA only drive - frustrations documented by others here on CN.

I plan to use it mostly with the Vixen Porta mount, but I've installed another dovetail bar to the original threaded inserts in the OTA. That bar is mainly used to attach a GSO RACI finder but can also serve if I want to mount the ETX on the Celestron CG5GT or the Canadian Telescopes Duo-T mount.

The rings are Crawmach for a 4.080" OTA. The main dovetail bar is a 7" ADM. The secondary bar is a 7" Astro-Tech.

The finder is mounted via an Agena mount foot attached to an ADM saddle adapter which serves double duty as a safety stop when mounting the ETX via the secondary dovetail. There's another ADM saddle adapter on the primary (side) dovetail as a safety stop too.

The Porta head is shown here mounted on a Bosch surveying tripod but will fit on the CG5 tripods as well. The Porta is equipped with an ADM saddle replacing the usual Vixen part.

Finally, the dew shield is an Astrozap.

Here's a few photos:

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#2 highertheflyer

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Posted 27 May 2013 - 06:33 PM

That's an absolutely beautiful setup and gosh, for a scope of their age, I do know of their qualities.
Mine is mounted on an early Ioptron GoTo for star parties, and only the thoughts for sightings with that focal ratio, the primary finder scope mounted alongside.
Very nicely done,
Jim

#3 wd4ohd

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Posted 08 December 2013 - 09:43 PM

I want to defork my ETX90EC for use with an iOptron IO-3100 GEM mount. Can you give me any directions about how to remove the OTA from the fork or point me to directions online? I've been looking for some info on how to go about it, but so far to no avail.
Thanks
Bob

#4 Don Taylor

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Posted 09 December 2013 - 10:17 PM

I want to defork my ETX90EC for use with an iOptron IO-3100 GEM mount. Can you give me any directions about how to remove the OTA from the fork or point me to directions online? I've been looking for some info on how to go about it, but so far to no avail.
Thanks
Bob


Sorry for the delay - I don't check this forum very often.

To defork - there are 4 small Allen head screws that must be removed. Level the ota and on either side there are 2 screws that attach a small plastic arm from the mount to the sides of the plastic backplane of the scope. (Just forward of the flip mirror knobs). Remove these 4 screws. Then you need to gently spread the mount arms and the tube can be slipped free.

You can mount the ota using the threaded holes on the bottom or use rings which is much more secure.

I've changed the setup from the photos somewhat - I have now 3 vixen style dovetail bars so the scope can be mounted on the Porta, the Duo-T, or either of the equitorial mounts ( since the tube and eyepiece do not rotate).

Let me know (or send pm) if you need pictures etc of the deforking process






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