Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

H-Alpha 12 Aug (The effect of seeing?)


Macavity

Recommended Posts

Quite thought I lost the knack of H-Alpha solar imaging?
(If I had ever found it! lol) Or my Lunt 50 was "broken". :o

Frankly, I find it difficult to tell "seeing quality" from the
monitor, but I do notice a *significant* difference in the
fraction of events aligned / stacked in "default" Registax.

Seeing.jpg

The image (07:53) aligned/stacked 1948/2181 frames
The image (09:55) aligned/stacked only 249/2189! ;)
I changed little else? What a difference just 2hr made?

Of course one could do things better... but this might
be a possible way of "knowing", before I waste a whole 
morning (Tens of Giga Byte of disk) before realising! :p

At the moment, I check JETSREAM forecasts too??? :D

http://www.metcheck.com/UK/jetstream.asp

Ah Well! Here's a basic "combi" image from 8 o'clock:

DispProms.jpg

P.S. Had a few goes at the PROMS, but none better those already shown here! :D
I was struck by the significant variation in brightness! In the event of good seeing,
I did wonder about "bracketing" exposures then contrast masking etc. etc. but...

Link to comment
Share on other sites

Thanks folks! Of course, the above "theory" may or may not be true. :p

But I did wonder why (apparently!) the image is more "soft" the further
away from the point chosen for Registax to *align* stacked images too?
I did think I might have developed some sort of "aberration" as well! :D

Link to comment
Share on other sites

I love the colour composite.  The seeing can change from second to second sometimes as you'll know.  Not always, but generally, at my home location the seeing is much more likely to be good in the early morning, even when the sun is very low.  Late in the day can be good too, but not nearly so often as in the morning.  The middle of the day is nearly always poor, but once in a while I might get a pleasant exception :smile:.  If I'm pushed, I'll try my luck in almost any conditions.  I also find that frequently the same seeing seems to have a more detrimental affect on white light than H Alpha.

Link to comment
Share on other sites

2 hours ago, Macavity said:

Quite thought I lost the knack of H-Alpha solar imaging?
(If I had ever found it! lol) Or my Lunt 50 was "broken". :o

Frankly, I find it difficult to tell "seeing quality" from the
monitor, but I do notice a *significant* difference in the
fraction of events aligned / stacked in "default" Registax.

Seeing.jpg

The image (07:53) aligned/stacked 1948/2181 frames
The image (09:55) aligned/stacked only 249/2189! ;)
I changed little else? What a difference just 2hr made?

Of course one could do things better... but this might
be a possible way of "knowing", before I waste a whole 
morning (Tens of Giga Byte of disk) before realising! :p

At the moment, I check JETSREAM forecasts too??? :D

http://www.metcheck.com/UK/jetstream.asp

Ah Well! Here's a basic "combi" image from 8 o'clock:

DispProms.jpg

P.S. Had a few goes at the PROMS, but none better those already shown here! :D
I was struck by the significant variation in brightness! In the event of good seeing,
I did wonder about "bracketing" exposures then contrast masking etc. etc. but...

Nothing 'Basic' about that ! it's a lovely image, I'd be proud of that one.

Link to comment
Share on other sites

Interesting comparison,  I don't think I have ever stacked that many frames (1900).  I am sure there is a equation to indicate how frames are needed for optimum SNR (signal to noise ratio), but I will allow somebody with more understanding of this to maybe say what that is. 

Always nice to get a good end result though, that is a fine set of images.  

Link to comment
Share on other sites

Thanks again folks... "So many variables, so little time"? :p

I think it notable that there are some brave souls who document such things...
Some "usual suspects" are revealed by a Google Search! :D

As a quick experiment, I tried simply "moving the slider" in Registax 5 to reduce
the number of optimised & stacked frames from (almost) 2000 to a mere 100! 
The frame "quality" number correspondingly rose from 90% to 97% ...
And the stacking time is (naturally) considerably reduced! :)

Frankly, I struggle to see any difference between:

Full sample 1948/2181 frames at 90% quality

SunHalpha_075359A_default.jpg

 

Small fraction 100/2180 frames at 97% quality...

SunHalpha_075359A_cut100.jpg


FEWER event to process is always good! Always assuming I haven't got my images mixed up! :D 

For Registax 5, it seems like a "good thing"  to have a fairly large align box size (128x128) and then
to cut back a "fair bit" into the lowest quality value? That does seem something of a consensus too? :)

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.