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Last Ganymede transit w/ASI120MM 1 resize 1.35X

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#1 edsplace

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Posted 06 December 2012 - 05:02 PM

I found the best capture from last nights transit and re-sized it 1.5X the image didn't hold up, so I downsized it 10%. It looked better. The albedo features on Ganymede are easier to see, but I am not sure there is any more detail to them. I found after processing all the videos that as I increased the gain edge artifacts would form, if I kept the gain below 50 they were much less noticeable or not there. I also found that in the green channel there were edge artifacts if focus was just a little bit off, or in poor seeing when there were no artifacts in the other channels. This was the only downfall I have found so far, and I am not sure I would consider them a problem.

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#2 Erik Bakker

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Posted 06 December 2012 - 06:48 PM

That's a beauty Ed. Worlds in all sizes.

#3 DesertRat

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Posted 06 December 2012 - 06:53 PM

Looks great Ed!

Artifacts can come from some kinds of really diabolical seeing types, the camera or the stacking process. What kind of edge artifacts are you referring to?

Glenn

#4 edsplace

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Posted 06 December 2012 - 07:26 PM

I have attached an image that I have used excessive wavelets on to show the effect clear. You can also see they are constant throughout images in the animation I made here https://dl.dropbox.c...0612-0353ut.gif if you look on the edge you can see the line stays fair stationary throughout the 23 frames.

reminds me a bit of the Phillips 740K when excessive gain was used.

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#5 Kokatha man

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Posted 06 December 2012 - 07:32 PM

.....I don't believe those are camera artefacts per se Ed - I could be wrong of course, but they look much more like low gamma to me! :)

I hope/presume you're using "Gamma=50"....?

As I said beforehand, I haven't experienced any such effects personally..... :question:

#6 edsplace

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Posted 06 December 2012 - 07:50 PM

Yes, I had the gamma set at 50. They may not be camera artifacts, they could be from AS2!, from capture setting, or even from the capture program. I have been able to "find" these rings in every other camera I have had (Phillips Vasta, Pihillips 740K, Sac7b, LPI, Sac8, SaC 4.2, Homebrew FCLabs CMOS, DMK21, and now this) some were more apt to produce the rings than others. This camera seems like it may be a bit touchy. Again... this camera outperforms all other cameras I have used, and I have been able to work around the rings.

#7 Kokatha man

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Posted 06 December 2012 - 07:57 PM

.....I also meant to say that I've seen low gain create that effect also.....but you're saying that the higher the gain is, the more likely they are....? :question: :confused:

#8 edsplace

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Posted 06 December 2012 - 08:03 PM

With the 740K I would get bad ringing with high gain and longer exposures if the object still remained dim. Filling up less than 50% of the histogram.

#9 DesertRat

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Posted 06 December 2012 - 08:04 PM

You can make any camera yield these onion rings. Usual cause is incorrect gamma. And even for gamma 1.0 sometimes if the exposure is not suffiently pushed the limbs fall in a flat part of the response curve. In other words the effective gamma is not what its set to. What you then have is large parts of the limb separated by too few counts. Then you get the posterization or the ringing effect seen here.

Glenn

#10 edsplace

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Posted 06 December 2012 - 08:06 PM

That makes sense. I will increase the gamma next time out and see if it helps.

#11 DesertRat

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Posted 06 December 2012 - 08:16 PM

Increasing the gamma may not be the best approach. Not sure about this camera but if 0.5 is gamma 1 (not the best number in my view to assign gamma 1) I'd try bracketing at 0.4 and 0.6, and also different gain settings. Yeah I know its a lot of work, but somebody has to do it! The good news is you don't need a lot of frames to determine the best combination, and you could do the whole test in red light just to keep it simple.

Increasing gamma can mean two totally different things in the image processing world, depending on the program being used. For a camera increasing gamma should appear to lessen the contrast across the planet, pushing it even higher the planet should appear almost all gray.

Edit: If you choose to test gamma as written above, also select 0.5! I left that out in error. :p

Glenn

#12 edsplace

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Posted 06 December 2012 - 09:51 PM

Doh! My gamma was set at around .25 (25) somehow in all the excitement I must have unknowingly moved the slider. It has been reset to .5 (50). Il. See how it works out next time. On a not great night ill run some gamma/gain test.

#13 zAmbonii

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Posted 06 December 2012 - 09:56 PM

On a not great night ill run some gamma/gain test.

I'll take your bad night images anytime over my good night images! ;).

#14 Kokatha man

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Posted 07 December 2012 - 12:11 AM

Doh! My gamma was set at around .25 (25) somehow in all the excitement I must have unknowingly moved the slider. It has been reset to .5 (50). Il. See how it works out next time. On a not great night ill run some gamma/gain test.


Heck, I pulled another one back from my C/T2 thread blooper in my own thread Ed :lol:.....tbh I really though that was the issue for you (hence my first response) but I didn't want to sound rude bout it..! ;)

FireCapture's log texts do have a couple of furphies, but they're allways a good port-of-call first-up to check your camera settings. :)

But great to put a finger on something - we're expecting to see even better images from your next decent seeing session! :waytogo:

#15 DesertRat

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Posted 07 December 2012 - 12:20 AM

Good catch Ed! I would stick close around 0.5 (gamma 1 ?) and vary other exposure settings to see if there is an optimum. Those logs are handy. Writing up your own notes sometimes helps also! Its amazing what you can forget in a span of hours, but at least the logs are written.

Problem with finding an optimum is that seeing trumps everything else by such a wide margin that night to night and even minute to minute variations can be misleading.

Glenn

#16 TorstenEdelmann

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Posted 07 December 2012 - 12:47 AM

Darryl,

FireCapture's log texts do have a couple of furphies...



Let me know what entries you have in mind and I can try turning them into code of law :lol:

Torsten

#17 Kokatha man

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Posted 07 December 2012 - 01:23 AM

Hi Torsten - I wouldn't want anyone to think that I have an ounce of criticism towards your supremely excellent software...particularly after all the work you did on the ASI120MM DirectShow camera (which types you'd already said to Sam and me were only kept viable on FireCapture by virtue of people's requests.....)

And tbh the only "furphy" I can now see is the exposure value in each log - it is perpetually "Shutter=1000.0s"

Many pardons if I seemed critical in any way....! :rainbow: :grin:

#18 MvZ

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Posted 07 December 2012 - 07:13 AM

Gamma setting 50 on this camera is actually gamma 1. It is actually the default setting for the camera. Ah well, it brings a bit of variation to all the camera's out there, sometimes gamma 100 is gamma 1.0, or gamma 0 (for the good old vesta pro), and now it is 50 ;)

#19 TorstenEdelmann

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Posted 07 December 2012 - 07:34 AM

Hi Darryl,
Don't worry I was just kidding. I'm happy to receive any comment that helps me improving the program.

it is perpetually "Shutter=1000.0s"



Is that only for the ASI or also for your other cameras ?
Torsten

#20 wenjha

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Posted 07 December 2012 - 07:48 AM

Hi Ed
The inner ring usually come from bad seeing .
here is a test I did.
I think short exposure can reduce the inner ring problem.

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#21 edsplace

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Posted 07 December 2012 - 10:23 AM

Sam, I think you are correct about some ringing also being from bad seeing. I had average seeing the other night I am fairly sure the problem was my .25 (or .5 if you move 0 ganma to 1 where Emil likes it, personally I think that Gamma 32 should be 0 it maxes out at around 212 and bottoms out at -273)

I will dig through my logs and see when I moved the slider over, check images pre and post movment.

#22 MvZ

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Posted 07 December 2012 - 10:29 AM

Now I'm confused, but that is fine.

(as long as it is clear that you should use gamma 50 for this particular camera, because that is the most neutral/linear setting. This corresponds to an actual gamma correction value of 1.0: http://en.wikipedia....ma_correction).

#23 Kokatha man

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Posted 07 December 2012 - 11:07 AM

Hi Darryl,
Don't worry I was just kidding. I'm happy to receive any comment that helps me improving the program.

it is perpetually "Shutter=1000.0s"



Is that only for the ASI or also for your other cameras ?
Torsten


Hi Torsten - I'm pretty sure it's only with the ASI cam: I think it is fine and gives the correct exposure values on the Flea3. :)

Sometimes the Flea3 logs would give weird focal lengths and quite large variations between reds and the green/blues but atm the ASI cam values are nearly allways "5000mm" for red and "5050/60mm" for the other 2 channels.....but perhaps this is a natural result of diffraction etc altering image scales slightly between channels - I presume FireCapture does some simple measurement of the image to arrive at the log values... :question:

#24 edsplace

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Posted 07 December 2012 - 01:15 PM

Sam, I do think the ring you show may be an artifact of bad seeing and the rolling shutter. I think that everyone else has it correct with my image that the ring was caused by a poor gamma setting. I'll run a couple of tests on the next night that is below average seeing with different gamma/exposure/gain and see if I can find anecdotal correlations.

#25 KpS

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Posted 07 December 2012 - 02:39 PM

it is perpetually "Shutter=1000.0s"


Is that only for the ASI or also for your other cameras ?
Torsten

I just made a test for ASI120MM and DMK21AU618. FC 2.2 beta (Build:#35) gives the correct exposure values on the DMK. The logs for ASI perpetually shows "Shutter=1000.0s" independently of exposure.






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