Sunday, August 1, 2010


My first scopes were of the cheap department store variety.  When I started getting serious about the hobby, though, I invested in an Orion SkyQuest XT6 Classic Dobsonian.  It uses a parabolic primary mirror.  The aperture is 150mm (6 inches), and the focal length is 1200mm, which gives it an f/8.0 focal ratio.

Orion SkyQuest XT6 Classic Dobsonian
I use the XT6 primarily for visual observation, but I also use it for planetary imaging.

When my old Meade EQ60 equatorial mount broke, I purchased an Orion ShortTube 80 (ST80) Equatorial Refractor.  This little achromat is a nice wide-field telescope.  I sometimes use it for visual, but mostly use it for imaging.  The aperture is 80mm, and the focal length is 400mm.  That makes it an f/5.0, which is pretty fast.

Orion ST80 on EQ-1 Mount, DSLR mounted piggyback
Chromatic aberration can be an issue with brighter objects, but the objective lens dust cap has a smaller inset cap that allows the scope to be stopped down to about an f/9.0:

Dust cap with inset cap removed
The ST80 sits on an Orion EQ-1 equatorial mount.  This mount is fine for visual, but terrible for astroimaging. With patience and a lot of hard work, though, I can still get some decent images out of this setup.

Back in the early 1990s, Sam Houston State University purchased a Takahashi Epsilon-200 astrograph and NJP mount.  There are only about three dozen Epsilon-200s in the world, and less than a dozen in the United States!  Unfortunately, the person who purchased it left the university shortly thereafter, and no one knew what to do with the scope.  It sat, forgotten and used, for years.  During a Huntsville Amateur Astronomy Society (HAAS) meeting in 2006, Mike Prokosch showed the scope to Anjal Sharma, who recognized what a gem it was.  After about two years of work hunting down and replacing missing parts, cleaning everything, and upgrading the electronics, the Epsilon-200 was ready for action!  Anjal compiled a slideshow that details the rebuild.  It can be viewed here.

Anjal trained me on how to use the Epsilon-200, or as we like to call it, the Yellow Beauty.  I have had a blast using it, but have only scratched the surface of its potential.  I purchased a Canon EOS Rebel XS DLSR camera, which I attach to the scope using a T-ring adapter.  I have had some problems with the mount, though, but think that I have isolated the problem to the declination motor.  Hopefully we can get this problem fixed soon.

The Epsilon-200 has a 200mm aperture (8 inches) and an 800mm focal length.  That gives it an f/4.0 focal ratio.  The large aperture and fast focal ratio means that it can gather a lot of light very quickly, which is advantageous in astroimaging.  It has a hyperbolic primary mirror (hand ground by Takahashi mirror makers, as I understand) and utilizes a large field flattener lens.

Takahashi Epsilon-200 on NJP Mount

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