Rick sits to view through the 20" F/3 MX telescope - MX stands for
"Mike's eXperiment". The 1.25"-thick primary mirror was made by Lockwood Custom Optics.
ON A WARM, sunny afternoon at the Okie-Tex Star Party
in late September of 2008, Rick Singmaster and I were discussing the
amazing performance of the 16.5" FX with the 17mm Ethos/Paracorr combo
(if you haven't already, read the Okie-Tex 2008 article that I wrote for more about this).
We started talking about
just how fast a Newtonian telescope could be. At issue were the optical
fabrication and collimation tolerances. Could a faster mirror be made
to our optical standards and could the telescope hold collimation as it
was moved around?
It seemed there was only
one way to find out - to actually build one. We were aware of a 25" F/3
telescope that had been built some years before, but we thought it
prudent to experiment with a smaller instrument that would require a
bit less time and effort to construct.
A couple of years ago I
bought some 20" F/3 mirror blanks. They are Pyrex, and only 1.25"
thick. I thought about making a 20" classical Cassegrain or R-C with
these used as the primary mirror, carefully mounted, of course. I even
had two polished out and ready to figure. So, the logical path forward
was for me to figure one of these mirrors to a parabola and put it in a
telescope. I thought about building my own telescope for a while, but
then I decided that my time was better spent making mirrors at that
point. Lucky for me I was sitting next to a guy that could built a very
good telescope, knew how to collimate it properly, and didn't mind
observing from a seated position over the WHOLE sky.
I figured the mirror in
late 2008, and shipped it off to get coated. Rick received it in
December, and the scope was mostly done at that point. Cold weather
postponed the application of the wood finish for a little bit, but
eventually it was done, and Rick said he planned to take it out on the
next clear night, which was forecast to be damn cold.
I came home from a meeting of the Champaign-Urbana Astronomical Society
and noticed that the message light on my machine was blinking. I played
it and Rick's voice spoke "Mike, it's Rick, I looked through you
telescope tonight. Give me a call." Way to spill the beans, Rick.
So, I called, and to make
a long story short, despite a night of bad seeing, the telescope
performed reasonably well, giving round stars. Nothing looked too bad,
but the seeing was not good enough to say much more than that. The next
night of observing followed some collimation tweaks, including squaring
the focuser more precisely. At F/3, every little bit is important, and
it paid off. Images were even better.
Finally, a decent night
came with warmer temperatures. The F/3 was set up next to a 20" F/3.7
that I had recently completed, and the shoothout was underway. Here's a
photo of Rick with the 20" F/3.7 FX to the left (Rick's right) and the
20" F/3 on the right.
Rick stands between a 20" F/3.7 FX (left) and the 20" F/3 MX (right)
Basically, in comparing
the two telescopes, once the mirrors equalized a bit, the differences
in the images were fairly minor, and were evident only upon careful
inspection around the edges of the Ethos field. The view at the center
was essentially identical, with the thinner mirror having a slight
advantage as the temperature dropped quickly.
The following are quotes from Rick, about comparing the two telescopes:
"Very favorable comparison."
"Most of the time you wouldn't know which 20" you were looking through."
These quotes are about the 20" F/3 MX:
"The views are what you'd expect to see in a good telescope."
"This telescope has exceeded my expectations."
"The damn thing is just amazing."
"The (observing) chair is a must, the ladder is not!"
That's it for now. Rick
and I will meet at an undisclosed location in Missouri and I'll get
acquainted with my new telescope. I'll add more photos here of that
event and eventually some photos from Chiefland and the Winter Star
- Mike Lockwood, Lockwood Custom Optics