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By Greg Mort
Some time back in the forums discussions there was a question about what a TriSchiefspiegler Telescope was. That query being answered the notion then was raised about limitations, pluses and minuses and so on. Having had a bit of experience with such tilted component telescopes or (TCT's) I thought I might offer some information to Cloudy Nights readers.
Back in the day there was a monthly classified paper called "The Starry Messenger" which preceded the Internet classifieds we know and love today. It offered all the great things you might find today in classifieds but the response time was a slower pace and one contacted each other via phone or mail. (Can you imagine ?) Anyway, in June of 1998 (on page 11) (I kept the issue) there appeared an add from a gentleman out of Terra Haute, Indiana who was offering a set of 12.5" f/20 TriSchiefspiegler optics for $1000 dollars. I was very curious having owned a 4.5" f/29 Kutter design (two mirrors) made by Tomas Dobbins. (well known author and telescope designer/builder.) In fact it was Dobbins himself, that on more than one occasion had proclaimed these types of optical arrangements as "The Ultimate Planetary Telescopes."
By virtue of having owned a tiny 4.5" TCT and understanding what Mr. Dobbins was talking about, this made me wonder what a much larger aperture instrument might be capable of. So I decided to find out. In a few days the optics arrived along with the largest piece of graph paper I had ever seen. 4 feet by 9 feet. The seller was kind enough to send a schematic showing the exact layout and position of the three mirrors. Primary 12.5" Secondary 6" Tertiary 6".
I suddenly realized I had bitten off quite a lot as I began making plans for constructing the optical tube assembly and fork mount. I proceeded in any case and some 8 weeks later I had completed the first stages of the project. With much anticipation I placed the optical components in the large coffin shaped structure. (during the construction I often joked to my wife that, "If I die during this project, use the container to bury me in) For the initial test the fork was mounted alt azimuth style till the 1/2" birch fork was (ultimately) reinforced by a friend who welded a 1/4" steel frame that fit inside the fork!
Well after considerable fabrication and sweat imagine my shock and horror when I gazed down into the eyepiece and saw only light… no image good or bad of any kind! It was the same feeling I had some years earlier when my brand new Gibson SG Guitar tumbled out of it's case, down a flight of stairs (you know, in slow-motion) and the neck sheared completely off! What had I done wrong, clearly something very bad.
After I collected myself some old spark in the back of my stunned brain reminded me of an article in Sky and Telescope some years ago. A gentleman name A. L. Woods. Went back to the issue and it had his address and phone number. I decided to give him a call, at least to cry about my failure to somebody. He could not have been more kind and helpful.
In a heartbeat Mr Woods explained how to construct an alignment target to fit on the front of the scopes opening. A kind of cross-hairs and concentric circles deal out of tracing paper. Imagine my relief when it all cam e together! I was completely renewed ! My investment in dollars and two months work was not in vain after all.
By this time it was late summer and by chance that year Jupiter was in the evening sky. My first view though the "Monster" was nothing more than mind boggling. Not only was there more detail than ever witnessed by this observer, but the color and contrast were a revelation of unexpected delight.
Mr. Dobbins was spot on. These were amazing systems.
With further investigation I became aware of the amount of detail "within" the Great Red Spot" as well as subtle albedo markings on two of the Galilean satellites. And yet the scope was not even mounted equatorially. Drawbacks? there are any number. Starting with size. Hardly a portable telescope! The completed system is nearly 500 lbs.
I decided to build a roll out scope from a stationary structure. The base of the set up has ten large casters which keep it polar oriented coming out of the 10 ft x 15 ft shed. Cool down? After sunset the scope must be opened up to let the large air mass in the tube come to equilibrium with the night air.
Collimation? I have improved on this over the years via laser application. The main advantage of this is I can do it alone. Originally it was best done with two people, one looking in the eyepiece tube, one tweaking mirrors.
Part two of the story is interesting as well. When I originally received the optics they needed re-coating. The report came that all three mirrors were "Under-polished" That came as a surprise to me judging by what I had seen. So for over ten years I used the scope as is. Enjoying it immensely. Then about a year ago I decided to sell the scope, in fact, readers of Cloudy Nights may remember my ad in the classifieds.
When my wife found out about my idea to let the scope go on to another life, she wisely encouraged me to think again. At this point I took her suggestion to heart and decided to look into having the optics looked at again. Finding someone to deal with them took a bit of searching but in the end good fortune provided a most happy outcome. Yes, the mirrors surfaces were indeed "Very Rough". I began to wonder, what would they be capable of when smoothed? An optical master named Gordon Waite answered the challenge. Between his talents and the expertise of Richard Buchroeder from Tucson Arizona (Genius of this particular 3 mirror system) (I make people laugh when I say the scope's proper name quickly… "BuchroederTriSchiefspiegler"
Dr. Buchroeder was very kind with emails and information sharing with Gordon Waite. In the end the retro-fitted optics with 1/53 wave surfaces proved to be, literally, beyond belief.
Just a very few nights ago, with some good steady air, I enjoyed a view of the planet Saturn unlike any I had seen to date. To think I had almost let this scope slip away? That would have been a major mistake.
The long and the short of all this is… Anyone who would like to consider such a telescope should not enter into it half heartedly. But, if done properly, a system like this will give much pleasure in planetary, lunar, double star and even globular cluster observing.
- Mason Dixon, David Lane and BinoGuy like this