From: Ray Byrne <ray@in4media.co.uk>

Date: February 8, 2010 9:31:23 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Sunday Sun Day

Hi Alan,

Congrats on Spaceweather airing of you lovely image/images. Thanks for that info I've often found that stacking WL sunspot images just seems to make things worse so I'll take your advice. I'm dead keen on doing some imaging of Solar activity but it's snowing here at the moment (I've not even christened a 4" ED APO I bought last year especially for the purpose yet). I've also got a special kit to turn my 80mm ED APO into an Ha scope which includes using part of a PST (I'm on the lookout for a used one) I've got a Solarmax 40 to tide me over. Do you Keith's image stacker for searching through the frames?

ATB

Ray

On 8 Feb 2010, at 16:15, Alan Friedman wrote:

Hi Jim,

Machine processing of solar images is very difficult due to the tremendous morphing that happens in normal daytime seeing. Even equally sharp frames can have a significant form change from frame to frame. I find this problem a little less pronounced on prominences than on surface details of the chromosphere. I use stacking most of the time on solar prominences, but often work with a single frame, or perhaps averaging two or four hand selected frames in Photoshop when working with the solar disk in average daytime seeing. Stacking reduces noise, but it also greatly softens the detail... unless the seeing is particularly good. And often the details change so much that the alignment process just doesn't work. 

The good news is that the solar chromosphere is so bright you can usually expose with no gain and get very nice individual frames. 

In terms of frame selection, I usually start with a larger selection of frames than I expect to use (by setting a lower CI) and then go through them one by one to reject the ones that are not up to snuff. It is time consuming, but it will improve the results. 

best,

Alan

On Feb 8, 2010, at 10:12 AM, jimchung2338 wrote:

I was out enjoying the Sun probably at about the same time Alan was, only I was on the other shore of the Lake Ontario.

The seeing was very occasionally fleetingly good and I got my first good sunspot capture as shown here:

http://tech.groups.yahoo.com/group/Astro_IIDC/files/Solar/Sunsportcompared.jpg

Here's my question which Milton will undoubtedly address.
The images were stacked with Lunar-Solar alignment, 64x64 pixel comparison area and horiz and vert fine alignment. I also stacked with a 6.5 variance per pixel.

What I found was that AstroIIDC had a hard time accurately assessing the sharpness levels of each frame. Oh, and I successfully cleaned the CCD so absolutely no dust motes remained to confuse AstroIIDC.

On the top, the left is 200 images/1500 stacked and on the right I hand selected about 100 frames and rejected another 100 that were undeniably blurry. You can see the right side is noticeably sharper.

On the second row is the same sunspot but with the etalon tuned past the Ha wavelength. Again the left is 200 stacked images but the right was only about 40 hand selected images - the rejected ones were very blurry. The right side is significantly sharper than the left.

Each pair of images underwent identical PS sharpening.

Any insights?

Jim