Friday, June 22, 2012

Travellers solar setup

Today I practiced using the small solar H-alpha setup I will be using for our upcoming trip to Mallorca and - later on - to Australia for the total solar eclipse of 2012. I also used this setup for shooting full disc views of the recent Venus transit and that went well. It features a Coronado SM60/BF10 0.7Å H-alpha filter, f=420mm ED refractor on an AstroTrac mount.

This time I wanted to have a go at some more resolution, so I plugged in a 4x powermate. The optical resolution of the 60mm aperture H-alpha filter is around 2.3". The effective focal length of my setup with a 4x powermate is around 1700mm; hence the image scale on the Skynyx 2-2M camera is 0.5"/pixel. I will thus be oversampling the optical resolution by a factor ~4 at 1x1 binning. If needed I can use 2x2 binning and oversample by a factor ~2. I should therefore be able to get close to the maximum possible resolution with this aperture.
Travellers solar H-alpha imaging setup
Setting up is quite fast since polar alignment isn't really that important for this kind of work. In addition, everything is light and small - unlike my other setup which uses a Tak EM200 mount and a 6" refractor. In order to reach focus a 2" diagonal has to be inserted before the rest of the imaging train. The whole arrangement pressed the Crayford focuser and mount pretty hard, but I could still focus and navigate around the solar disc. I am using the Baader Stronghold for holding the scope and enabling fine-tuning of pointing. It was not the completely smooth, solid experience you get with the EM200 mount - but that thing isn't about to sneak on as carry-on luggage anytime soon!

The Sun was pretty quite today and it was late in the afternoon, but I still shot some 1500-image sequences of  a pair of prominences. Stacked best 60 frames using AviStack, wavelet filtered using Registax, and colorized in Photoshop - see results below.
Best 60 out of 1500 frames; 20msec exposure time with gain=3

Best 60 out of 1500 frames; 5msec exposure time with gain=7

Now I just need to foam pad a small carry-on airline suitcase and I am ready for take-off to Mallorca next week!

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