Sunday, 19 April 2009

Focal reduction and image scale with a Mintron

The standard C/CS 1.25" adapter is about 28mm long. A focal reducer lens will attach to the end of this tube and change the F/ratio of the system, producing an optically faster system with a smaller image scale and wider field of view. I have produced 1.25" adapters of various lengths to demonstrate that different image scales (via different F/ratios) are produced with different length adapters. This is important for some telescopes that are unable to focus in enough when a focal reduced lens is used with a normal length adapter.

Focal Reducer Lens

Mintrons fitted with a 12mm or a 28mm adapter, a focal reducer lens and a light pollution filter.

The MTV-23S85HC-EX-R monochrome deep-sky Mintron was used with an f/10, 6" Schmidt Cassegrain telescope.

M3 with the 0.5 focal reducer and a 28mm adapter

M3 with the 0.5 focal reducer and a 20mm adapter

M3 with the 0.5 focal reducer and a 12mm adapter

The differences in image scale can be seen in these images and can be comparted with the image below produced with no focal reducer.

M3 with no focal reducer

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