Friday, July 5, 2013

M16 in process

As a consolation prize for not going to GSSP because of an injury, I've worked on some practice shots over the last two nights.  The weather is clear and the moon is absent, allowing a small chance to get some decent data.  It's not as good as if I got out of town, but with enough subs, the signal to noise ratio will improve.

Two nights and 11 reasonably good exposures shows promise.


This is a screengrab from PixInsight, just after a quick crop and Auto STF.  Note the relative smoothness of the lighter areas and the noise in the background areas nearby.  This is a 200% view.

Ambient temperatures were pretty warm this night - lows were only in the low 70s.  EXIF temps on the lights read from 16-18 C.  The TEC was set to -10C.  It's likely that the camera was really near 10C.  The local dewpoint was 54 F and the camera body was wet, giving my conclusion.

I did repeat the Marek-style polar alignment again before starting.  There was a need to touch up in AZ and ALT.  Did these adjustments with the scope facing West.  Also used a 3 minute duration exposure to elongate the star trails.

Based on the calculations on this spreadsheet, so long as I have a tight, single pixel line, I should have no problems with drift over the course of the night from field rotation.

Today, I checked the bolts on the mount and a few were slightly less tight than I'd prefer.  Probably due to the heat cycle of the day.  Tightened everything down.

Before starting another run, I did the V check again.  No need to adjust in ALT, and there was a need to adjust in AZ!  Probably due to the tightening of the bolts.

I'm going to run the session with no PEC to see if I still see RA drift.