Mel Bartels' telescopes and telescope making

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Some of My Telescopes

My first home built telescope - a 8" f/7 on a horseshoe equatorial mount. As a kid, I had fallen in love with the 200" Palomar scope. Since my dad worked in home building, I used wood.  Here's a sketch from the side, and a sketch of the yoke. 

My next home built scope - a 10" f/5.   I built my own drive using wood putty to form the impressions and a metal threaded rod attached to the motor. Because many threads were in contact at any one time, errors in the threads were averaged and there was no backlash. Here are sketches of the fork arms, base, and cradle.  I built a cold camera (here's a sketch) to take long exposure astrophotographs at prime focus of the 10". For more on the 10", see April, '79 Sky and Telescope.

I also experimented with quick change self-collimating diagonal mounts. A small bolt attached to a plastic plate pressed against a spider vane. Each diagonal's plastic plate and bolt were collimated individually. This gave me the option of switching diagonals for wide field viewing and narrow field high power viewing. Despite many hours of critical planetary comparison, I was never able to see much difference between closely sized diagonals.

I combined what I had learned with the 8" and 10" into a new larger scope, a 14" f/5. All motions were motorized, including a sliding eyepiece and camera holding plate that the diagonal was attached to.

I built a color enlarger to process the negatives taken with the 14", along with a slide projector and blink comparator.

I used an unusal guiding arrangement where inline dual 3.1" diagonals grabbed 90% for the home built cold camera, and 10% of the light for a guiding eyepiece focused on the exact field of view that the camera was photographing.

I built an observatory that consisted of a roll-off shelter. First light throught the 14" at the Orion Nebula was so breathtaking,

I told myself that someday I would have a 24". The focal ratio is f/5.5 and a 6" f/4 was used as a finder. I trailered the 24" to very dark skies in the Oregon Cascade Mtns. Here are three views of the trailering in action: image 1 image 2 image 3  And here is an early version of the 24" in an A-frame (a smaller view) truss tube arrangement.

After doing the 24" by hand, I quickly realized that a grinding and polishing machine was a necessity. Steve Swayze later used this machine to work his 40" f/5 with. Incidently, that 'little' finder scope is a 12" f/4 by Swayze!

Aperture fever led to the 30" f/4, showed in its test bed for star testing the figure of the primary setup for a public lunar eclipse party. The unaluminized mirror was perfect for lunar viewing. Here is what the pitch lap for the 30" looked like. Here is what a tiled plaster grinding tool looks like. Here is the grinding log for a 20" mirror.

Here are two sketches for German Equatorial Mounts: this is an extended polar axis, and this has a lowered counterweight.

Here are two sketches of unusual yoke equatorial mounts: the first is an offset yoke with counterweight, and the second is a bent yoke.

A 12" f/6 dob with a very open A-frame truss tube.

A 10" f/5 dob, typical of scopes built for friends.

A 17.5" f/4.5 horseshoe, built for a friend.

A 17.5" single armed dobsonian sketch.

A fork mount capable of handling medium newtonians, built for a friend.

A typical sketch of fork arms, and a side view.

First iteration of my 20", at '94 Oregon Star Party (Swayze's 40 inch is in the background). This version won a Riverside RTMC merit award in 1994. An early version of the stepper drive circuit.

An early iteration of my 20", at '95 Oregon Star Party, Richard Berry and his cookbook CCD is on the left.

A later iteration of my 20", 1996, showing the 1 arm fork rocker. A view showing the scope loaded into the trailer.

An even later iteration of my 20" into a super ultralight version with piggybacked 6”.

Current version of the 20 inch with the trilateral mount (2003)

A 10" f5 equatorial torque tube mounted scope by Greg Babcock equipped with sector drives that I built.

A 12” f/4 tilted Dobsonian, called a PED (polar equatorial disk), sometimes called a Rob-A-Dob, after Rob Adams, who specialized in this type of mount, 1988.