H Alpha from the 10th

[David Smith]

I took quite a bit of H Alpha data on the 10th but was struggling to process on the day, so I just processed the frame containing the big AR and then moved on to Ca-K and white light. With a bit of time on my hands tonight I decided to have another go at it.

In the past I have always tried to use the QHY5-IImono at full resolution (1280x1024) and struggled to get full frame illumination to be able to get a decent flat field. So on Sunday I switched the QHY down to 640x512. This does several things, 1. the reduced frame size fits inside the sweet-spot of the PST 2. ROI fits inside the area of the sweet spot which is less affected by newton rings 3. frame rates are higher so I can get 1000 frames in less time.

First I took 200 de-focused frames in a quiet area of the Sun for a flat and then 15 panes of 1000 frames in a rather haphazard manner! Unforutnately clouds came over before I could cover the entire disk. Used AS!2 to generate a flat file but when I usedthis during stacking it left me with bright fringes around the output images. So I put the flat into GIMP and stretched it 50% and hey presto, now the output images from AS!2 are much more even.

After a quick batch process through Imppg, Autostitch was able to assemble all 15 panes into something recognisable. Some minor tweaks in GIMP produced the image below. Shame I missed a bit near the AR but as a proof of concept I am pretty happy. Compared to some of my previous efforts it is relatively free of newton rings and relatively even-toned across the mosaic. Not sure how often I will have the patience to sit and shoot a 20-25 pane mosaic though!

[Pete Presland]

Got the main area of action!

[laudropb]

A lot of work but the end result was worth it. Very nice image.

[Davey-T]

Looks good to me David, doing this on iPhone so driving me nuts 

Dave

[Ewan]

David, really glad you persevered with the data stitching, as you say proof in the pudding but above all you just learnt something new.

Yep res isn't the be all & end all, a lower res bigger fov is great for FD's where as high res for close ups is a must.