Solar Processing... Over-Sharpening
- Lowjiber
- Orion Spur Ambassador
- Articles: 2
- Posts: 975
- Joined: Tue Apr 30, 2019 12:30 pm
- 4
- Location: Las Vegas, Nv, USA
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
Solar Processing... Over-Sharpening
Quoting NASA...
"Our Sun is surrounded by a jacket of gases called an atmosphere. The corona is the outermost part of the Sun's atmosphere. The corona is about 10 million times less dense than the Sun’s surface. This low density makes the corona much less bright than the surface of the Sun."
When we capture a solar image of the center of the surface, the "thickness" of the corona is much less than when we capture an area closer to the limb. That results in a gradient across the surface that is lightest in the center, but darkening a bit as our eye travels toward the limb... That's a good thing because we want the surface to appear as a "ball".
When we capture a prominence, we are still looking through the density of the corona. Proms are nothing more than a dense cloud of incandescent ionized gas within the corona... Resulting in their beautiful "feathery" appearance. To prove the point, here's a NASA image of several proms surrounding Sun...
Do any of those proms look like pieces of uncooked spaghetti? No. Why? Because the ionized gases are "mixing" with the gases of the corona.
As solar imagers we have to deal with the excessive corona gasses surrounding our prom and mitigate to a certain extent the corona over the surface. There are several ways to do that... Curves, Gradient blending, Levels, Burning, etc. But the most dangerous "tool" in the box is without a doubt SHARPENING. Don't misunderstand, sharpening is a legitimate tool when used properly, but overdo it and your image may look like it belongs in a comic book.
The small comparison below has an image on the left that was processed properly (It won some kind of award back in 2018.) On the right is the same image over-sharpened... Note that the surface looks contrived and the proms are beginning to get the uncooked spaghetti look. I've seen images sharpened even more, but couldn't bring myself to go any further. LOL
So new solar-heads, the next time you pull the sharpening pencil out of the crayon box dull it a bit before ruining your current masterpiece.
Clear Skies & Stay Safe
"Our Sun is surrounded by a jacket of gases called an atmosphere. The corona is the outermost part of the Sun's atmosphere. The corona is about 10 million times less dense than the Sun’s surface. This low density makes the corona much less bright than the surface of the Sun."
When we capture a solar image of the center of the surface, the "thickness" of the corona is much less than when we capture an area closer to the limb. That results in a gradient across the surface that is lightest in the center, but darkening a bit as our eye travels toward the limb... That's a good thing because we want the surface to appear as a "ball".
When we capture a prominence, we are still looking through the density of the corona. Proms are nothing more than a dense cloud of incandescent ionized gas within the corona... Resulting in their beautiful "feathery" appearance. To prove the point, here's a NASA image of several proms surrounding Sun...
Do any of those proms look like pieces of uncooked spaghetti? No. Why? Because the ionized gases are "mixing" with the gases of the corona.
As solar imagers we have to deal with the excessive corona gasses surrounding our prom and mitigate to a certain extent the corona over the surface. There are several ways to do that... Curves, Gradient blending, Levels, Burning, etc. But the most dangerous "tool" in the box is without a doubt SHARPENING. Don't misunderstand, sharpening is a legitimate tool when used properly, but overdo it and your image may look like it belongs in a comic book.
The small comparison below has an image on the left that was processed properly (It won some kind of award back in 2018.) On the right is the same image over-sharpened... Note that the surface looks contrived and the proms are beginning to get the uncooked spaghetti look. I've seen images sharpened even more, but couldn't bring myself to go any further. LOL
So new solar-heads, the next time you pull the sharpening pencil out of the crayon box dull it a bit before ruining your current masterpiece.
Clear Skies & Stay Safe
John (Urban Astronomer) Apertura AD10 Dob; XLT 150 Dob; XLT 120EQ; Lunt Solar 60 PT/B1200; ES AR102; SW Pro 100ED; 2 SW Pro 80ED's; 90mm Eq; WO Z-61; SW 90mm Virtuso Mak; 2 Orion ST-80's; Quark-C; Cams: Polemaster, ASI120MM-S, ASI174MM & ASI174MM-C
- Gordon
- Site Admin
- Articles: 1037
- Posts: 8268
- Joined: Wed Apr 24, 2019 10:52 pm
- 4
- Location: Cottonwood, AZ
- Status:
Online
-
TSS Awards Badges
TSS Photo of the Day
I Broke The Forum.
Re: Solar Processing... Over-Sharpening
Thanks for the lesson John!
Your insight is always appreciated!!
Your insight is always appreciated!!
Gordon
Scopes: Explore Scientific ED80CF, Skywatcher 200 Quattro Imaging Newt, SeeStar S50 for EAA.
Mounts: Orion Atlas EQ-g mount & Skywatcher EQ5 Pro.
ZWO mini guider.
Image cameras: ZWO ASI1600 MM Cool, ZWO ASI533mc-Pro, ZWO ASI174mm-C (for use with my Quark chromosphere), ZWO ASI120MC
Filters: LRGB, Ha 7nm, O-III 7nm, S-II 7nm
Eyepieces: a few.
Primary software: Cartes du Ciel, N.I.N.A, StarTools V1.4.
Scopes: Explore Scientific ED80CF, Skywatcher 200 Quattro Imaging Newt, SeeStar S50 for EAA.
Mounts: Orion Atlas EQ-g mount & Skywatcher EQ5 Pro.
ZWO mini guider.
Image cameras: ZWO ASI1600 MM Cool, ZWO ASI533mc-Pro, ZWO ASI174mm-C (for use with my Quark chromosphere), ZWO ASI120MC
Filters: LRGB, Ha 7nm, O-III 7nm, S-II 7nm
Eyepieces: a few.
Primary software: Cartes du Ciel, N.I.N.A, StarTools V1.4.
- notFritzArgelander
- In Memory
- Articles: 0
- Posts: 14925
- Joined: Fri May 10, 2019 4:13 pm
- 4
- Location: Idaho US
- Status:
Offline
-
TSS Awards Badges
Re: Solar Processing... Over-Sharpening
Thanks for a very nice discussion of the perils of over processing. However there is one statement that is astrophysical problematic.
https://en.wikipedia.org/wiki/Limb_darkening
The corona is irrelevant to this effect.
Because the corona is so transparent it is impossible for the gradient of brightness across the solar disk to be caused by differing thickness of the corona. In fact if there were no corona at all the gradient would still exist. The phenomenon is known as "limb darkening" and depends only on the properties of the photosphere and chromosphere.Lowjiber wrote: ↑Tue Jul 28, 2020 3:48 pm
When we capture a solar image of the center of the surface, the "thickness" of the corona is much less than when we capture an area closer to the limb. That results in a gradient across the surface that is lightest in the center, but darkening a bit as our eye travels toward the limb... That's a good thing because we want the surface to appear as a "ball".
https://en.wikipedia.org/wiki/Limb_darkening
The corona is irrelevant to this effect.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
- Ben Cartwright SASS
- Orion Spur Ambassador
- Articles: 0
- Posts: 654
- Joined: Fri May 17, 2019 10:39 am
- 4
- Location: SE New England
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
Re: Solar Processing... Over-Sharpening
If you show both images to non-solarheads they tend to prefer the sharper "spaghetti" look.
I wonder if some of the softness that we find right is caused by our atmosphere? How do space telescopes see the proms?
I wonder if some of the softness that we find right is caused by our atmosphere? How do space telescopes see the proms?
I might not always be right but I am never wrong, once I thought I was wrong, but I was mistaken...
Ferengi Rule of Acquisition #59
Free advice is seldom cheap
"Sometimes having is not so pleasing as wanting, it's not logical but it is true"
Commander Spock
Canon DSLR's R7, R6II, 5D, 7D2, 90D 21 lenses incl. 100-400L mk ii, 70-200L mk iii f/2.8, RF600/11
Lunt LS50 DS, LS80 DS, Lunt 102ED, Stellarvue SV80 APO, Orion ST80, 127 MAK, Skywatcher Evostar 120ED, 102 MAK, Celestron 8" Edge HD, 102AZ
Skywatcher EQ6-R Pro
ZWO ASI071MC-cool, ASI174mm, ASI174mm-cool, ASI178MC-cool, ASI290 mini, ASI120MM-S, ASI120MC Revolution Player One mm (178 chip)
Ferengi Rule of Acquisition #59
Free advice is seldom cheap
"Sometimes having is not so pleasing as wanting, it's not logical but it is true"
Commander Spock
Canon DSLR's R7, R6II, 5D, 7D2, 90D 21 lenses incl. 100-400L mk ii, 70-200L mk iii f/2.8, RF600/11
Lunt LS50 DS, LS80 DS, Lunt 102ED, Stellarvue SV80 APO, Orion ST80, 127 MAK, Skywatcher Evostar 120ED, 102 MAK, Celestron 8" Edge HD, 102AZ
Skywatcher EQ6-R Pro
ZWO ASI071MC-cool, ASI174mm, ASI174mm-cool, ASI178MC-cool, ASI290 mini, ASI120MM-S, ASI120MC Revolution Player One mm (178 chip)
Create an account or sign in to join the discussion
You need to be a member in order to post a reply
Create an account
Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute