Post by tomg on Jul 27, 2015 8:23:14 GMT -5
Hi,
After years of using Schmidt-Cassegrain, I decided that I would build a refractor. Not just any one, but a folded refractor.
I received my Istar 6" F/15 lens about 6 months ago, and started construction. I had acquired a 4 inch 1/20 wave flat, and also a 70mm 1/10 wave elliptical secondary for the folding of the light path.
The first version of this, was built using a 10" diameter aluminum tube, with aluminum baffles, ½ inch aluminum rods as stringers, and had 1/4" aluminum end plates. While it was a success, I realized that my current mount was not up to the 24 pound payload without accessories. I was surprised considering that I had spent a lot of time and I had thought that the compressed length of 34 inches would mean less weight as well. I then decided that I would by a new mount, that was state of the art, and chose a new AZ-EQ mount being released this year, that could hold two 30 pound telescopes if needed.
I redesigned the tube, and chose the Istar Asteria open tube design as a model. I used 1 x 1 x 1/8 inch aluminum and marine grade HDPE board (1/2 and 3/8 thick). I chose this material because it is easy to work with, machines easily, and of course is impervious to moisture. I chose a shape that was aesthetically pleasing and a bit radical. Current weight is 16 pounds with turret eyepiece.
Currently, I have tested it using an artificial star to fine tune it, and comparing the alignment with my Questar 3.5, and they both are spot on.
I have had a few short hours observing and I am delighted with the results. Finally, a set of optics that are up to my expectations!
Thanks,
Tom Gideon
After years of using Schmidt-Cassegrain, I decided that I would build a refractor. Not just any one, but a folded refractor.
I received my Istar 6" F/15 lens about 6 months ago, and started construction. I had acquired a 4 inch 1/20 wave flat, and also a 70mm 1/10 wave elliptical secondary for the folding of the light path.
The first version of this, was built using a 10" diameter aluminum tube, with aluminum baffles, ½ inch aluminum rods as stringers, and had 1/4" aluminum end plates. While it was a success, I realized that my current mount was not up to the 24 pound payload without accessories. I was surprised considering that I had spent a lot of time and I had thought that the compressed length of 34 inches would mean less weight as well. I then decided that I would by a new mount, that was state of the art, and chose a new AZ-EQ mount being released this year, that could hold two 30 pound telescopes if needed.
I redesigned the tube, and chose the Istar Asteria open tube design as a model. I used 1 x 1 x 1/8 inch aluminum and marine grade HDPE board (1/2 and 3/8 thick). I chose this material because it is easy to work with, machines easily, and of course is impervious to moisture. I chose a shape that was aesthetically pleasing and a bit radical. Current weight is 16 pounds with turret eyepiece.
Currently, I have tested it using an artificial star to fine tune it, and comparing the alignment with my Questar 3.5, and they both are spot on.
I have had a few short hours observing and I am delighted with the results. Finally, a set of optics that are up to my expectations!
Thanks,
Tom Gideon
