Sun Spot group near Limb

Date of image 22/07/2016

Equipment: SW Skymax 150 (f12) at prime focus with a home-made Baader solar film filter (full aperture). The telescope was mounted on an EQ5 pro. Camera: Canon 550D in 640x480 movie crop mode set at 1/1000s exposure ISO1600, the frame rate was 60fps. I chose a higher ISO setting because I had read that this noise will actually decrease quantisation error when stacking 8-bit/channal frames. 

I am very please with this pic, it shows the same sun spot grouping I have photographed over the past week but now it is close to the solar limb, faculae are clearly visible. I also like the fact that the curvature of the limb also gives a sense of perspective for the Sun spots. Weather was ok, there was a lot of turbulence in meaning focusing was even more difficult that on devious days imaging. I took several movies each time slightly nudging the focus and this was the best result.

The total movie duration was about 5 minutes. The best 25% of frames were selected and decompressed by Pipp, Stacking and editing was done with RegiStax 6. I used about 40 alignment points. I think about 400 frames made it into the final stack. I did not ramp up the wavelets because I was getting ringing effects at the limb. I also do not like that bloated look that features get when wavelets are overdone. 

The telescope was not tracking well here, I kept adjusting the azimuth but I did not have a lot of time to get a great PA,