I recently purchased a new SCT optical tube assembly to
replace my lovely orange tube C8 that I retired from action. I’m pleased to say that the Old Girl has
found a new home with a collector who will look after her.
So, this new SCT needs a mount.
I purchased this scope knowing that I have a German
Equatorial Mount (GEM) that can take it.
However, GEM mounts do not place the eyepiece at the most convenient
location. There is also the meridian
swap in order to keep the motor drive loaded appropriately without undue
stain. Yet a fork mount has a much more
limited range of eyepiece placement, and is not affected by the strain of
meridian shift.
So, I’ve got a new OTA, but which set of forks?
One reason that I bought this particular OTA is that it has
screws on it that would seem to correspond with the coupling holes on the fork
mounting plates. I have an old set of
forks from the same brand as the OTA, so why not look at seeing if I could
couple this OTA with these old forks?
I’ve been using these old forks as my video astronomy rig, having made a
platform that spanned the forks.
Alas at first glance not.
The OTA appeared to be wider in diameter than the span of the forks and
the coupling holes did not match. The
latter was by just 1mm, but enough for the screws not the fit.
So begins the search for a set of forks to match, and an
interesting saga of near misses, useless sources of information, wonderful
people willing to help, and pigheaded, devil may care, try it and see try to
fix it attempt.
So, after the question asking, frustrations, and fruitless
searching, the promise of finally a clear sky and the chance of finally doing a
sketch of the Moon, I decided to have another go at fitting the OTA to the old
forks. I mean, how hard could it be,
right? So after dinner, I disappeared
into my workroom and let the Devil take over!
I decided to take the arms off the mount, modify the holes
to allow the screws to fit the OTA. This
was very quick and easy to do as it was just a minimal amount of material that
I had to adjust. To my joy, the third
hole in the coupling plate was a perfect match to the corresponding hole on the
OTA. Bonus! This allowed me to first couple the tynes to
the OTA with this third, leaving the two other holes easier to deal with.
Once both tynes were fitted, I lowered the OTA onto the
mount. I expected there to be a gap
between the mount and the tyne attachment points, and had thought of a way to
deal with it. But to my surprise, there
was no gap! It was a perfect match! Perfect!
Finally I have a brand new SCT OTA with the convenience of
the fork mount that I preferred. I am
overjoyed that I have been able to once again re-purpose the old forks. The wedge I made some time ago and my kids
decorated it, and the tripod is a surveyors’ tripod. So my “new” scope is a real Frankenstein,
made up of old and new, DIY and re-purposed.
And it all works brilliantly 😎
Now, to get scope time once again. I’m hoping that the sky
finally clears this weekend. The
forecast is promising. I’m now all
dressed up, and nowhere to go until the clouds clear. Oh, well, that’s how things go with astro…
Alex.