Friday, August 16, 2013

Mirrorless - not by design

I saw a post on Cloudynights where Rob (pfile) noted where he'd seen a page from a photographer that removed the mirror from their Canon camera in an effort to control vignette.

The interesting thing is that their flats seem to greatly mirror the effect that I see with my Pentax camera.  The vignette is not as strong as the Canon, probably because Pentax's Shake Reduction system requires a bigger mirror box.

I'm not prepared to make this modification yet.  However, I may get to it eventually, especially if I ever get another camera body for IR use.

Here's a video of the K10D in bulb mode for reference and to see what the relative size of the mirror boxes are.

For reference, here is an example of a flat after analysis by CCDInspector:
Before I actually consider doing a mod to the camera, I would like to work on centering the camera to the telescope.

Another thing I've noticed is that even with the flocking of the flattener and other work, I still see off-axis reflections.  I noticed last night when imaging IC1396 that Akaris created a bright spike into the frame.  I think that there is something inside the scope that is setting up a reflection.

I looked down the throat of the telescope under intense daylight and was pleased to see no light coming in.  This means that any remaining light leaks are in the camera body.  Most likely at the dremel hole for the finger.  Time to wrap up the camera body with a sock!

Also while looking, I saw that the feathertouch focuser has exposed baffles that are bright and shiny.  These should be covered with a flat material.  I'm not sure if there's enough clearance in the drawtube to allow the flocking paper to be used.  I'll try pulling the focuser and lining it next week.