I purchase a Skywatcher 150mm Evostar ED (1200mm fl/ f8) a couple of weeks back. Last night was clear and I got the scope out for its first light. It was a very bright sky with the moon one day past full so I thought this would be a good time to check the scope’s ability to deal with chromatic aberration, (CA). I didn’t use a moon filter.
Using a 17mm Orion Stratus eyepiece (68 degree apparent fov) I centered the moon and noticed CA along the small terminator (green). There was no CA along the limb, around craters, or anywhere else I could see. I changed the eyepiece to a 25mm plossl (52 degree fov) and did not notice any CA. A 10mm plossl (52 fov) gave another CA free view. I didn’t stay out long as the sky was becoming somewhat hazy and my test was limited to these focal length eyepieces.
I know this was a very short session with this scope and I plan on pulling an all-nighter as soon as the opportunity presents itself. I have a few questions: About the Stratus-Why does it show CA when the plossl did not? What is a better test for CA? What eyepieces should I purchase for this scope? Thanks for any advice!