116RE: [William-Optics] Re: [Telescopes] Digest Number 917
- Jan 1, 2001I created an illustration that shows how to best balance the Megrez for
imaging, but it also applies to the use of weighty eyepieces. The basic idea
is to offset the scope from the center of the mount head by using an
over-sized dovetail. I uploaded the illustration to the Files section of the
Wm. Optics egroup:
This technique can be used with any wide-field, fast refractor. Note also
the use of an extension tube. You can also use one visually. The ideal
solution is one that threads onto the diagonal, but a conventional extension
tube will also work. A threaded extension tube is supplied with the Megrez
for imaging, if I am not mistaken; I will have to see if there is an
arrangement that would let you use it with eyepieces as well.
From an imager's point of view, it is always better to have a shorter tube,
as one can always make up the difference with extension tubes. There is
nothing simple you can do about a tube that is too long.
The New CCD Astronomy Book
web site: http://www.newastro.com
From: Archer Sully [mailto:archer@...]
Sent: Monday, January 01, 2001 2:56 PM
To: firstname.lastname@example.org; William-Optics@egroups.com
Subject: [William-Optics] Re: [Telescopes] Digest Number 917
> For people like Ron who have had the scope for a few more week now,I haven't had nearly the time to use this scope as I'd like, but
> care to gave us some follow ups??
> Especially comparing them to similar sized RFT, from Tak FS78, to the
> Chinese 80 F5. On both visual, photo, and CCD performances.
I have played around with mounting it a bit, and I do have some
1. The tube is one inch (25mm) too short. There isn't an eyepiece
in my collection that I don't have to pull out a bit to reach focus,
even with a 2" (TeleVue) diagonal.
2. Related to point 1, the tube is difficult to mount and balance
on a garden variety (in my case, Vixen Polaris) GEM. I can only
use one of the supplied rings, so the scope is a bit less stable
than I'd like. I suspect that with a proper adapter it would be
easier, as I could locate the mounting rings close together and
use both of them. However, even then the focuser knobs will interfere
with the head, so that only the full rotation of the focuser won't
be possible. Shortening the tube won't help this, but adding
some weight to the business end will.
3. The focus lock/roller clutch works well. I did a bit of solar
photography yesterday, and focus stayed put nicely after locking
everything down. Camera was an OM1, so I wasn't pushing it, but
I think it will work well for the task that I acquired the instrument
for (eclipse photography). I'll be posting the images on my own
website in the coming days for anyone's edification and amusement
at my very green technique ;-).
4. The optics and baffling on this scope are excellent. Still haven't
gotten a proper star test done, but I expect it to be very good. The
views through the scope are very nice indeed, even though the aperture
Going forward, I expect to fabricate a new adapter plate
for my current mount for use at home. For travel use, I'll
have to come up with an appropriate head for a heavy duty camera
tripod (probably a Velbon Carmagne). This will either involve
a barn door of some sort (type IV?) or if I'm feeling flush
perhaps I'll just spring for the Tak Sky Patrol II.
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