"I have designed an optical system that can be thought of as an unobstructed Newtonian telescope," wrote Jose Sasian in Telescope Making #38. The design has the advantages of the Newtonian; a comfortable viewing position and the potential for a simple mounting. The secondary may be larger to avoid a turned-edge and left circular.
Jose Sasian relaxes behind the unobstructed Newtonian of his own design. The open frame telescope has doors which close over the optics for dust protection. | ||
Details of Jose's toroidal secondary mounting and latching cover. The double curve is polished into this mirror by means of a simple jig. | ||
Craig Engelhorn's rendition of the unobstructed Newtonian. The tube goes from being round at the primary to being oval at the secondary. | ||
Front view of Craig's telescope reveals the secondary tucked out of the way. A Ronchi grating showed perfectly straight lines proving that double curve mirrors can be made well by amateurs. |
Primary diameter | 150mm |
Radius of curvature | 3600mm |
Figure | paraboloid |
Angle of tilt | 2°.25 |
Distance to secondary | 1400mm |
Secondary diameter | 46 x 65mm |
Radii of curvature | 5900 and 11780mm |
Angle of tilt | 42°.75 |
Distance to image | 365mm |
System f/number | 10.92 |
Focal length | 1638 |
Image plane tilt | 8° |
Curator: Hartmut Frommert
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