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Old 07-23-2013, 12:14 AM
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Default Hatbox Telescope and Mount

I have been working on a telescope and mount that are (still) in the final stages of fabrication. After machining a worm gear or two and developing the control software, I will be able to control it from my iPad. The telescope is a 6-inch F10 (6 inch mirror diameter, 60" focal length) Newtonian model. The mirror was hand ground and polished under the direction and with the assistance of a local amateur astronomer who holds an annual workshop for amateur telescope builders. About 40 hours of grinding and polishing was required to generate the correct 'figure' for the primary mirror. The polished glass was then coated with a durable reflective surface.

Smaller Newtonian telescopes such as this are most commonly constructed using a long cylinder, with the primary mirror (the big one) mounted on one end, and with the secondary mirror (a much smaller one), focuser and attached eyepiece on the other end. The cylinder needs to be a larger diameter than the primary mirror, and is usually at least as long as the focal length. This cylindrical assembly then needs to be mounted so that it can be easily pointed at an object of interest. Transporting such a telescope in a passenger car leaves little room for passengers and luggage.

Another method of construction involves breaking the telescope into an upper and lower section, with most of the weight (due to the large primary mirror) being in the bottom section. The upper section is connected and aligned with the lower section using a truss system of light tubes. This allows for much easier transport of the telescope, but requires that the upper section be very light in order make a practical mounting arrangement.

A third method of construction uses three sections. This adds a middle section to the second method described. The middle section is located at the center of gravity of the assembled telescope, which makes it possible to have a relatively compact mounting arrangement. The design challenge for this telescope was to reduce the size of the telescope for transport.

The following picture shows the assembled telescope on its mount. The mount shown is not yet complete.




Here is a link to a Flickr set which illustrates the packaging of the Hatbox Telescope:
Hatbox Telescope and Mount-1 | Flickr - Photo Sharing!


Here is a link to a Flickr set which shows more details of the telescope and mount design:
DSC_3131 | Flickr - Photo Sharing!

This project has been an ongoing effort for a number of years now. The German Equitorial Mount is a half scale version of a mount that supports a much heavier and much better constructed telescope. This implementation has used bushings where the original used precision bearings. I will try to answer questions that I am qualified to answer. It was necessary to cut the worm gear out of metal as the epoxy that I had used in the original gear was breaking, and was not accurate enough.

I can elaborate on details of interest in response to questions.

Charles
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Last edited by CharlesWilson; 07-23-2013 at 11:54 PM. Reason: removed wanton asterisk
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Old 07-23-2013, 07:47 PM
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Default Re: Hatbox Telescope and Mount

Nice. Do you have to calibrate the mirrors each time it is set up or are there accurate enough stops in the legs to make this only an occasional necessity? I would guess you have to use this in very dark places. That stray light effect...
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Old 07-23-2013, 08:22 PM
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Default Re: Hatbox Telescope and Mount

Quote:
Originally Posted by Wonderwino View Post
Nice. Do you have to calibrate the mirrors each time it is set up or are there accurate enough stops in the legs to make this only an occasional necessity? I would guess you have to use this in very dark places. That stray light effect...
The ability to adjust the primary mirror is built into the lower section, and can be adjusted while looking through the eyepiece. It is performed once after each assembly. The adjustment of the secondary mirror is very easily performed also. The distance between sections is kept constant on all sides when Joining with the poles. I use an 'Astronomical Story Stick' when setting the distance between sections.

There is a black nylon shroud that wraps around the assembled telescope, which is used under all circumstances. It is used at night even in Northern Vermont.
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