Posts Made By: Roland Christen

November 23, 2009 03:04 PM Forum: Refractors

SIX INCH F12 D&G REFRACTOR.

Posted By Roland Christen

Congratulations. You have an excellent telescope on a beautiful mounting.

Rolando

December 3, 2009 04:43 PM Forum: CCD Imaging and Processing/Deep Sky

Tony Hallas has made a 3 DVD set of how to process deep sky images. How to get good star colors is discussed, among a miriad of other advanced techniques and tricks. We'll be selling this set on the AP web site soon, if you're interested. Probably be up next week.

Rolando

December 3, 2009 11:59 PM Forum: Equipment Talk

Northwest Suburban Astronomers annual swap fest

Posted By Roland Christen

Hi Gordon. Can I bring some of my stuff? grin

Roland

December 5, 2009 10:18 PM Forum: CCD Imaging and Processing/Deep Sky

NGC 660

Posted By Roland Christen

WoW! Excellent!!

Rolando

December 18, 2009 10:35 PM Forum: Maksutovs

Gregorian Maksutov ?

Posted By Roland Christen

>>Which led me to wonder why there aren't any of them about, that I'm aware of, in useable astro apertures. And if not; why not? >>

Because the distance from secondary to focus is longer, therefore the secondary must be larger diameter than with a normal Mak.

Rolando

December 22, 2009 07:20 PM Forum: CCD Imaging and Processing/Deep Sky

16.5 Hours of NGC7380 Wide Field

Posted By Roland Christen

Very innovative setup, well done!

Rolando

December 23, 2009 05:22 PM Forum: Refractors

Pinched Optics?

Posted By Roland Christen

If the lens cell is too tight versus the diameter of the glass, then it can pinch when it gets to a certain low temperature. Aluminum shrinks at a rate more than twice that of glass. If the temperature gets too low, say below zero, the cell will put intense pressure on the glass and the optics could crack in half.

These simple cells really cannot be made with too much clearance because that could produce coma in warmer temperatures.

Rolando

December 31, 2009 06:13 PM Forum: APM