by Richard Crisp
I took three exposures of 30min each with halpha last night
the brighter stars exhibit a reflection halo surrounding them. the more off-axis they are, the more asymmetric the reflections become. they are some rather complex reflections actually reflecting within the Halpha filter itself and the lens element.
the filter is made of two sheets of optical glass forming a sandwich with the dielectric filter stack placed between the two sheets of glass for protection.
The glass can create noticeable reflections if the stars are bright and the nebula image so dim as to not swamp out the reflected light
this is a dim object.
http://www.narrowbandimaging.com/sh2_129_150mm_cm10_ha_page.htm
the dimmer stars are round throughout the image so the asymmetry in the bright stars is due to reflections etc.
Posted on sf-bay-tac Sep 05, 2005 15:59:35 PT
Converted by report.pm 1.2 Mar 10, 2006 22:07:53 PT