A discussion at our last astronomy club meeting had me thinking it would be fun to try sketching the Sun over a period of time. As luck would have it, I had made a sketch earlier that afternoon, so decided to give it a go for a week.
All observations were made using the TMB 80 refractor and a Delos 10mm eyepiece @ 48x. I did try using the R.C but found the TMB’s image was just that little bit sharper, no matter what eyepiece combo I used on the bigger scope. The detail sketch made on the 24th was made using the Altair Astro 250mm with Delos 14mm @ 145x
The one thing that did surprise me is how well the positioning matches the SOHO images taken on the same day. I didn’t use any kind of grid on the eyepiece or the drawing to help locate positions, which just goes to show how well the eye is capable of judging such things.
One problem I did find was with the scope mounted on an Alt Az mount. The cardinal points rotate in the FOV over the course of a day, which make aligning all the images so North was upward, proved to be a real pain. This changing angle is called the parallactic angle. Fortunately I discovered Helio Viewer suite of software by Peter Meadows which helps with this alignment. The software will also calculate the sunspot latitude and longitude as well as many other measurements. I’ve downloaded the software and once I understand how these all work, will try running my sketches and images through them.
I’ve also dug up a copy of the BAA’s ‘Observing Guide to the Sun’ that I acquired at the Winchester Weekend this year – which I guess I ought to read 🙂
21, June 14:04 UT. Seeing: II: Mostly Stable Transparency: V: Poor
24, June 15:49UT. Close-up detail of Sunspots 2095 and 2097.