Improved baffling of the six inch folded refractor
In my design there is a bulkhead near the focuser. See Constructing a Folded Refractor. This is mostly for structural support of the tube. It increases the rigidity. But the baffling incorporated at that point is fairly ineffective. The geometry makes it nearly impossible to block stray light from the objective (like an off-axis street light) from entering the eyepiece. However, I was able to do a very effective job of baffling by making a stop that fits on the inside of the focuser tube. That is the way Unitron did it and it seems to work just fine.
The focuser at the top of the picture is from a Unitron 131C, 75mm folded refractor. At the bottom is the draw tube from my scope. Notice that I have put a blackened light stop at the end of the draw tube. The size of the hole in my version is only 7/8 inch. This is just barely enough for full illumination at the center of my eyepiece. I am using the scope for planetary and lunar observation so this works well for me. I can easily enlarge the opening if necessary but the light fall-off at the edge of the field is not even noticeable. And stray light from my irritating street light is not a problem.
This is a Unitron 4 inch mount alongside a nearly identical home-built mount of unknown origin. The similarities between them are numerous. They both have the Unitron style declination slow motion controls, large high quality setting circles and are nearly identical in size and overall design. But the home-built mount actually has several improvements over the superb Unitron, including a breathtaking mechanical clock drive adjustment mechanism. The unknown maker of this mount was a genuine craftsman of the highest caliber. I call this mount a Uni-Clone with the greatest possible respect. You can see closeups of the mount, clock drive and corrector on Youtube at http://youtu.be/d1VNP8gpH-I .
Six Inch Folded Refractor
I have updated my Folded Refractor page as promised earlier. Please check it out if you are interested in strange telescopes. I include the steps I take to align and collimate the scope. Since I last built one about twenty years ago I had to learn this all over again with this more recent scope. I could not find anything useful online about this process so I thought this might, at least, give someone else a place to start. Hope you enjoy!
I used to get frustrated when I read about Amateur Telescope Making (ATM) projects that required machine tools since I did not have access to a machine shop. I still strongly support modest projects designed for the vast majority of telescope enthusiasts who do not have the inclination to buy a metal lathe nor the time to learn how to use it. It is great fun to test the limits of your skills with simple materials. I still enjoy making telescopes and parts from wood. It is a great challenge to make inexpensive telescopes that perform nearly as well as the best commercial products available. John Dobson inspired a lot of us!
Eventually I discovered that I needed metal to experiment with some novel concepts and designs. As my ATM creations became more sophisticated I had to develop metalworking skills. It is very easy to be drawn away from telescopes. Home Machinists like to make their own tools and create wonderful mechanisms. It is an entire world! Though I have been seduced into a few such projects, I have steered away from all that and always return to my first love – telescopes.
I am working on a page devoted to my six inch folded refractor. I could not have built it without my small home machine shop. I have come to love my lathe and mill as much as my telescopes. My Southbend 10K lathe is one of my most prized possessions. It is an exquisitely beautiful example of perfect design and functionality.
- A perfect blend of functionality and beauty.
- Exquisite craftsmanship
- Many unique and quirky features.
- Demonstrate superb attention to detail in every nut, bolt and knob.
- Uncompromising standards of design and execution.
- Deliver breathtaking performance.
- Highly collectible and rare.
- Small works of artistic and engineering perfection.
Another Youtube Tour of a Unitron scope at http://youtu.be/4C9OB9BYiXQ . Enjoy!
I have uploaded a couple of Unitron Video Tours. One is an overview of the 3 inch Unitron 145C. This scope is more properly called a “Frankentron” because it was assembled from various Unitron and shop-made components, like a sort of astronomical Frankenstein Monster. I included some nice closeup views of the beautiful setting circles. Please check it out at http://www.youtube.com/watch?v=-UU8zxAxss0 . The second tour is the 4 inch Unitron 160. There are more views of the spectacular Weight Driven Clock drive as well as a brief tour of the entire system. See this at http://www.youtube.com/watch?v=f4-EvkX7D1s. There is also an amusing time-lapse of the assembly of this telescope at http://www.youtube.com/watch?v=izGbmA_73jc .
Unitron 145C and Unitron 160
I uploaded a video showing the operation of a classic Unitron Weight Driven Clock Drive. This 50 year old device allows a telescope to follow the very slow movement of stars and planets. The stellar motion is undetectable with the naked eye but in a telescope the movement is highly magnified so a tracking mechanism is very helpful. The device works strictly because of gravity, allowing the user to set up the telescope far from any source of electricity. It works much like a old fashioned Grandfather Clock. Like any old mechanical device, many find it fascinating to watch. Please visit http://www.youtube.com/watch?v=agC1aJMBLlA to see the video.
Unitron Weight Driven Clock Drive
Unitron Weight Drive at night
Unitron 3 inch scope with Weight Drive
The old Double Arm Drive invention is still alive and kicking after all these years. When I recently updated the links on my page, I found that a lot of people still build them despite the extremely short exposure times and stacked processing available with modern digital astrophotography. As a matter of fact, my interest was rekindled a couple of years ago when I bought a Canon T1i and I got out the original Type 3 Double Arm Mount I made back in the 1980′s just for fun. I was able to produce some very nice shots with minimal post processing and no stacking at all.
Here is an example:
This was taken with a modified Canon T1i using a 50mm lens at f 2.5 for 2 minutes 30 seconds mounted on a Double Arm Drive. You can see the Lagoon and Triffid nebulae as smallish red glows near the middle as well as the large dark nebula sometimes called “The Pipe” toward right center.
My son, Richard, has created this new blog and website for me. It will now be much easier to edit and add content. I will be blogging about my new six inch Folded Refractor project so please stay tuned. This is a picture of it.