Astromart

>>I feel a bit naked doing this but I thought I would put OMI's specs on the mirror I just purchased (used) up for review:
http://tinyurl.com/yele62q>>

It shows a synthetic interferogram, so basically it doesn't give you the actual mirror data. No way to verify the results, I'm afraid. You will have to take their word for it, the data is not complete.

The attached image shows a real interferogram of a 1/10 wave .98 Strehl Ceravolo mirror. Note how smooth it is with no wiggles (zones) and essentially no edge zone.

Rolando

November 9, 2009 03:44 PM Forum: Refractors

TEC 160FL better color correction than TOA?

Posted By Roland Christen

Theoretically the TOA has the best color correction of any present commercially available refractor. Reason is that it has 2 wide airspaces which are used as two extra elements to correct for sphero-chromatism (spherical over and undercorrection at the ends of the spectrum).

Close airspaced lenses using FPL53 and BK7 are next in color correction, and depending on the focal ratio, will have some sphero-chromatism.

Oil spaced lenses can have similar color correction depending on the active element (Fluorite or ED) and mating glass, and they will also have some sphero-chromatism depending on F-ratio.

Oil spaced and close airspaced lenses will have fastest cooldown time. Wide airspaced lenses (like the TOA) are less stable in dropping temperatures, which may negate the lower spherochromatism of this design.

All of the above will work quite nicely for visual and imaging applications. See attached image of Horsehead taken with a 155 EDF lens, which is an oil spaced optic with FPL53 and BK7 glass. I think you would have trouble getting any better image with any other 6" refractor, which means to say that you will achieve essentially the same result with any of the refractor designs, regardless of marketeering claims of superiority (assuming they are well figured).

Rolando

November 10, 2009 09:00 PM Forum: CCD Imaging and Processing/Solar System