Attempting some solar imaging this week, and a few questions...

[Dave882 (David)]

I don't get out with the scope during the day much, but I certainly do enjoy a bit of solar viewing when i get the chance. I've had my current setup a year or so now: an old Daystar Quantum SE 0.5A unit that has some serious years on it, and an etalon that's probably overdue for refurb, attached to a Konus 120mm acro 1000mm fl, via the Baader TZ4, Optolong R-CCD 2" filter and a zillion extension tubes.

I had a bit of time last Wednesday 6th, so after a couple of hours scanning the various active regions with the binoviewers/powerswitch giving around 100-200x ish mag, I was quite impressed with the seeing conditions and decided to do some imaging with the ASI178mm.

I managed a number of captures using ASICAP, aiming for around 2000-2500frames, 10ms exposures and experimenting with different gain settings. I even gave myself a pat on the back for the foresight of taking flats!

On to processing. I'm not new to planetary processing, but boy this made me feel like an absolute idiot. Firstly, the flats didn't work at all as As!4 failed to recognise the files I'd taken (with the ASIAIR cause my laptop had been overheating badly...). Secondly, I couldn't get rid of some very obvious and awful stacking artefacts - checkerboard & watermark appearance. There didn't seem to be any rhyme or reason as they showed up in different places each time (even when i did multiple videos of exactly the same region!). I did manage to reduce them by making my align points much larger, but not completely... also ensuring that I had the entire image covered in align points seemed to help a bit too...

I've attached a few of my images and while I'm actually impressed by some of the detail that's come through, I'd really appreciate some advice on what I'm doing wrong in capture/processing.

So a few questions...

-What's the best parameters for capture and stacking?
-How do you take flats and apply them successfully in AS!4?
-Do you take multiple images for proms and surface detail and combine or find a middle ground on the exposure for both?
-I realise I'm imaging at close to 4000mm - so obviously I need to use a reducer in the train after the SE. Any suggestions?

Probably got a heap more than that but don't want to bombard you with too many! I really appreciate any thoughts and suggestions!!

[Unigraph (Harald)]

Hello David,

I have two tips for you:

1. the exposure time of the prominences is determined by their brightness. If this is too low in your setup, you will need two separate exposures for the surface and the prominence.

If the half-width of your filter system is very narrow, you can usually manage with one exposure time for the surface and prominence. This should not be the case with your setup.

2. I always make flats in Firecapture (FC), i.e. the flat is already taken into account during the exposure. This is very easy in FC and the stacking program has no problems with dirt on the sensor because the images are already clean.
I create the flat with a triple layer of transparent film in the light path or, in your case, in front of the optics with a brightness of around 60 - 70% of the histogram.

cs Harald
www.unigraph.de

[John W (John Wilkinson)]

Hi David, I'd say you have a lot of dirt on your optics. Give them a good clean a number of times. The images aren't bad. Keep experimenting and you will get better results.

Cheers, John W.

[Dave882 (David)]

Thanks Harold and John I really appreciate your input. Definitely much to work on. My opportunities to do solar imaging are few and far between but I’m keen to improve and I’ve also just found out that there’s a solar toolbox for PI so I’m looking forward to give that a whirl too with some better data.