5 replies to this topic

[gstrumol]

Took the PST out early this morning. Seeing was listed as below average in Astrospheric, and verified visually!  It was a fairly dull Ha sun this morning, compared to recent days; few and muted filaments, and only one prominent prom.

 

Here are the results:

 

(click to enlarge)

 

first taken with the zoom EP set to capture the full disk. Then setting it to maximum zoom (8mm):

 

(click to enlarge)

 

Finally, here is a comparison of two different tone curve shapes, applied to the zoomed image:

 

(click to enlarge)

 

A sinusoidal tone curve produces an inverted image that easily includes the prominences. Once inverted in GIMP you get dark prominences and a darkening around the rim, giving a hemispherical look to the disk. The more monotonically increasing curve (right) tends to remove the prominences but gives a more uniform disk appearance.

Edited by gstrumol, 21 May 2024 - 02:25 PM.

[David Rosenthal]

Nice images Gary and thanks for the IMPPG curve samples, I struggle with that tool

[David Rosenthal]

Gary,

I took my last image into IMPPG, started with your curve, and tried this to keep the background dark and the proms visible. Kind of a cool effect.

Attached Thumbnails

• 

Edited by David Rosenthal, 21 May 2024 - 12:42 PM.

[gstrumol]

Gary,

 

I took my last image into IMPPG, started with your curve, and tried this to kappa the background dark and the proms visible.  Kind of a cool effect.

Yes, that is the third type of tone curve I sometimes use. I call that one 'the hump' because of the initial bump in the curve before coming down and proceeding 'normally'. 

 

Edited by gstrumol, 21 May 2024 - 12:46 PM.

[rigel123]

Took the PST out early this morning. Seeing was listed as below average in Astrospheric, and verified visually!  It was a fairly dull Ha sun this morning, compared to recent days; few and muted filaments, and only one prominent prom.

 

Here are the results:

 

at1.jpg

(click to enlarge)

 

first taken with the zoom EP set to capture the full disk. Then setting it to maximum zoom (8mm):

 

at2.jpg

(click to enlarge)

 

Finally, here is a comparison of two different tone curve shapes, applied to the zoomed image:

 

at3.jpg

(click to enlarge)

 

A sinusoidal tone curve produces an inverted image that easily includes the prominences. Once inverted in GIMP you get dark prominences and a darkening around the rim, giving a hemispherical look to the disk. The more monotonically increasing curve (right) tends to remove the prominences but gives a more uniform disk appearance.

Does Gimp allow you to raise shadows?  I think if it can do that you can bring the proms out on that image on the right.

[gstrumol]

Does Gimp allow you to raise shadows?  I think if it can do that you can bring the proms out on that image on the right.

It can be done with a modification of the hump:

 

(click to enlarge)

 

but it's a delicate balance of prominence and surface detail. And the prominences aren't as 'prominent' as in the other approach.