A 10.5 inch [27cm], F2.7, 2.4 degree field of view Telescope

By Mel Bartels, June 2014

This telescope is all about the perfect balance between seeing limited resolution, aperture for going deep extreme wide field and compact-lightweight for that grab-n-go use. A telescope that is a joy to use, a telescope that is a joy to carry about, will be a scope that is a joy to observe through.

This scope is a larger twin of my 6 inch [15cm] F2.8, 4+ degree field of view telescope. Both mirrors were ground, polished and figured in tandem.

This scope continues my exploration of ever faster telescopes, starting with my 13.2 inch F3.0, followed by my 6 inch F2.8. I am so pleased with the pinpoint star images and dark field of view. Views of Saturn at 200x are very sharp. It's marvelous - a real joy.

To give you a taste, here's a sketch of the sweeping bridge that connects the Lagoon Nebula to theTrifid Nebula, showing the contrasty large field; and a sketch of the B84a area showing beautiful dark nebulae north of M23.
 

The 10.5 inch mirror is a meniscus mirror, slumped so that the glass has constant thickness from center to edge. As such there is no figure change when cooling, though because of the thin plate glass, the cool down period is very short, measured in minutes.

Here is additional information:
The Sketchup model is at https://3dwarehouse.sketchup.com/model.html?id=udbf9072e-5d62-420f-86bf-6b8d4ddb092e
How I made the mirror is at http://bbastrodesigns.com/JoyOfMirrorMaking/JoyOfMirrorMaking.html
The 6 inch smaller sibling that I discovered the Pleiades bubble http://bbastrodesigns.com/6inchF2.8/6%20Inch%20F2.8%20Telescope.html
The 13 inch that started it all http://bbastrodesigns.com/ZipDob/ZipDob.html

Here are images of the scope.





Checking alignment at the Dexter Oregon State Park public star party, July 2014.

The skeleton before the 1/8 inch veneer was added. The mirror box is separate.

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