Sunday, October 21, 2012

Eclipse 2012 - first field testing

Time is passing too quickly. Every other night I dream of technical details concerning Coronal photography, waking up after a few minutes. There are many details to worry about. Getting myself and the setup out under the skies, doing some test shooting on celestial targets, will help resolve many questions and quell my nighttime worries.

My first test was done in daytime, using the Baader solar filter. I wanted to practice setting up, framing the Sun in the camera field-of-view and focusing using live view on the PC. Running a full test script with Eclipse Orchestrator will also be useful: will the camera settings update correctly, will the tracking be good enough to keep the Sun centered throughout the session, will small sunspot details be visible?

Solar image through Baader  AstroSolar filter. Click to enlarge.
Just outside the dotted ring some broad, ring-like artifacts can
be seen. I think these are due to digitization levels becoming
visble after contrast stretching.
The first daytime session generally went quite well. Setting up was easy - I just did a casual polar alignment by dailing in my latitude on the AstroTrac wedge and orienting the setup axis roughly towards north. Focusing with live view worked well, tracking seemed stabile. I did not notice a lot of vibrations. At right is shown one of the images from the test script with 1/1250 second exposure time at ISO400. Small details in active region 11589 are visible. I did notice that these seemed to vary somewhat in visibily from frame to frame. Since the exposure time is very short I think this is caused by atmospheric turbulence. All in all I am quite happy with this first session as it did confirm the basic functionality of the setup.

However, what about doing all of this in the dead of night which is what I must be able to do in Australia next month? Will longer exposures remain sharp? Exactly how sharp (stars are great for gauging this)? The waning moon is a great test target since it will appear low in the eastern sky just like the eclipse. Read about my nighttime forays in the next blog posting.

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