The Celestron C90 Maksutov Cassegrain Telescope
Mar 02 2015 05:00 PM by skyaddict
William Optics Zenithstar 71ED and Twilight I M...
Feb 28 2015 10:53 AM by Ahab
If you want to Master your craft, read Lessons...
Jan 07 2015 11:29 AM by AstroDad
Celestron Ultima 80
Dec 16 2014 05:54 PM by Gianluca67
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I have devised a laser collimation test for Cassegranian systems. An on axis laser beam falling onto a 3M type reflective film creates a “virtual pinhole.” The backscattered light is sufficient to form an adjacent image from the primary that may be adjusted until it is brought into coincidence with the “virtual pinhole. This collimates the primary and allows the secondary to be collimated by conventional process, similar to Newtonians.
A process is described, utilizing readily available resources, for the fabrication of super-lightweight graphite-epoxy thin-wall tube structures. The heart of the process is in the compression molding tooling, which yields smooth exterior surfaces, and in the breakaway mandrel that forms the inside wall.
I had a set of Synta mirrors in storage which I had taken out of my Orion XT-6. I wanted to build a scope for them and after giving the project some thought I decided to build a strut Dob out of wood. The intended purpose of this scope would be for use at lower magnifications on deep sky objects. With a lot of miscellaneous stuff lying around, as well as access to a lot of scrap materials and discarded items, one of my goals became to build the scope as economically as possible while reclaiming and recycling as much as I could. The project would also be a good learning experience and an opportunity to try out different design ideas. The entire Dob was made with only a few old power tools and hand tools, as well as a small drill press and a Harbor Freight mini-lathe. I used a portable work bench I made to do all the wood cutting and sanding in my back yard. The rest of the work was done in my single car garage.
Not into “heavy scientific” work? Just want to enjoy the colorful rainbows of other stars, or see the fascinating absorption line detail in the solar spectrum? A number of options, some quite inexpensive, are available to display spectra for you.
My first impression is excellent. The WO Star 71 has a wide, well illuminated, flat field of view, exactly what I was looking for.
I started writing this article as a way to collect my thoughts on the new scopes. My plans were to send it to my contact with Meade, just to let him know what I was thinking, since I communicate with beginners looking for what scope to purchase.
Cloudy Nights members may be interested in a Schmidt camera that I made twenty odd years ago. Although photographic equipment has moved on since then, and Schmidt’s original design will now appeal to few, the novel method of making the corrector plate might still be useful in making a Schmidt Cassegrain telescope or astrograph.
The whole truly is greater than the sum of its parts, and this assembly really re-ignited my passion in this hobby.