stacking the sun

[glowingturnip]

Hi All,

So I've got a run of a sun surface close-up of an interesting sunspot group, taken with a DSLR, have about 150 frames of which 20 or so are good quality - can see granulation on the surface, good detail in the spots etc, focus looks good.  There's no limb present in the frames.

However, I'm really struggling to stack them - Autostakkert gave a recognisable but very blurred stack, Maxim DL gave garbage (auto correlation), DSS won't even try (no stars).  Registax did the best, see below, but this is not a patch on any of the individual frames:

Interesting that on the Registax stack, the very small spots look quite sharp, I guess it used those as align-points, but the big spots have lost all detail, I guess it doesn't do a uniform shift of all the frame.  (also interesting that there are so many small sunspots, I thought).

Any tips on how I can stack this data better ?  I let AS!2 and Registax choose their own align-points, maybe I should be more specific ?

[allcart]

Did you have AS2 set to surface before you analysed? You should.

[glowingturnip]

yes, it was.  Forgot to mention, also had a full disk run from the same session, AS2 did that one just fine

[cgarry]

It does not look like you have applied any wavelets yet.  You need to do this (or some other form of sharpening) to bring out the detail and improve on the individual images.

Cheers,

Chris

[glowingturnip]

no no, it's definitely the stacking - here's the best individual frame - quick initial stretch to see what's there, much better than the stack result above and I know i could get a lot more out of this in post-processing, but i just can't seem to stack them together

[Bizibilder]

Try just one align point and center it on the well defined spot on the left. Set the AP size at 128.

[Steve Ward]

I agree with the single align-point in this case as Roger has suggested.

My fear is that if this is the best sub of the bunch you will struggle to get much from the stack , it looks a long way from being in focus to my eyes ... 

[Steve Ward]

Sorry about that .

Pesky edit feature timed out on me half-way through .... 

I'll try again .

My fear is that if this is the best sub of the bunch you will struggle to get much from the stack , it looks a long way from being in focus to my eyes ... 

To justify the comment , here's my take on the region in question , a crop from a Full Disc shot made stacking just six frames ...

Focus is the most critical factor in any imaging and Solar is no exception , unfortunately the daytime atmosphere can play havoc with attaining focus , patience is the key , no quick 'chuck on a Bahtinov mask' fix here.

It's a case of getting what you think is focus and then monitoring the screen until you see the detail 'pop' out , if you don't see it after a minute then tweak focus and monitor again , it will become obvious when the detail jumps out at you , it's just a matter of patience.

When it does pop then lock the focuser very gently and rattle off a set of 100 or so frames , and then go through them to pick out the crisp ones , discard all the rest as they'll do nothing to improve the result.

Ten very good frames will beat 60 poor ones every time ... 

Happy hunting .... 

[glowingturnip]

that's certainly the picture I want to aim for   .  Will have a go with a single align-point tonight and see what I get. 

[glowingturnip]

Apologies for bumping an old post, but finally got round to processing this one:

I'm not surprised I was having difficulties stacking it, the seeing was terrible - I could see the geometry of the group on the right literally change before my eyes from one shot to the next.  Guess I should get up earlier before the atmosphere heats up.  Final image was 3 frames from about 110, stacked with DynamicAlign in Pixinsight, and even that was a struggle.

Still not as good as Steve's though  

[Steve Ward]

Can often be confusing between seeing and focus , the details can appear to be suffering from bad seeing when in fact the focus is just fractionally off .

I have an advantage with a USB controlled focus set-up and I would struggle without it , knowing there's a slight shift in focus from the centre of disc to the limb highlights just how critical it is , and how hard to judge at times.