Jump to content


Photo

Last Ganymede transit w/ASI120MM 1 resize 1.35X

  • Please log in to reply
43 replies to this topic

#26 DesertRat

DesertRat

    Fly Me to the Moon

  • *****
  • Posts: 5228
  • Joined: 18 Jun 2006
  • Loc: Valley of the Sun

Posted 07 December 2012 - 03:08 PM

I don't think its seeing, although seeing can do some strange things.

Rather at the lower gain the response was not as linear in that region (gamma NOT 1) as it was with higher gains. I've used lots of cameras over the years and have seen this before. At low gains the left side starting at zero intesnsity starts off flat with an effective gamma much less than one.

Glenn

#27 TorstenEdelmann

TorstenEdelmann

    Messenger

  • -----
  • Posts: 457
  • Joined: 29 Sep 2004
  • Loc: Landsberg, Germany

Posted 07 December 2012 - 06:10 PM

Hi Darryl,

Thanks, I will check the log entry for the ASI

ometimes 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


Please read these FL values in FireCapture as rough estimation. It's impossible to get an exact value on live data considering the error factors involved like seeing, orientation on the sensor, gain settings etc.

Torsten

#28 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 07 December 2012 - 06:14 PM

Okay I was not a WinJupos believer, I may be now. It seems as though with this image I have low noise and more detail when combining in Winjupos then if I do the color combine and luminescence layer. The polar areas and equatorial zone look to have more/finer detail while the whole image looks lower noise.

Attached Files



#29 Kokatha man

Kokatha man

    Fly Me to the Moon

  • *****
  • Posts: 6995
  • Joined: 13 Sep 2009
  • Loc: "cooker-ta man" downunda...

Posted 07 December 2012 - 06:33 PM

I don't think its seeing, although seeing can do some strange things.

Rather at the lower gain the response was not as linear in that region (gamma NOT 1) as it was with higher gains. I've used lots of cameras over the years and have seen this before. At low gains the left side starting at zero intesnsity starts off flat with an effective gamma much less than one.
Glenn


...I'll weigh back in here - Glenn is definitely correct here imho and is what I first said to you Ed in a couple of posts after you posted that image (hopefully absolving me of any further "guilt" :lol: from losing my "C's & T's" :grin: )

Looking at Sam's images it might be hard to see absolutely clearly on my laptop (why I really don't like processing on it!) but definitely the bottom right hand image in Sam's 4 is identical and (again imho) caused by either gamma and/or lowish gain.

The others (and I can't see the same effect in them as in the bottom RHS image) are caused (imho!) by excessive wavelets and/or deconvolution (referring to the more pronounced edge that runs around the inside periphery of the planet's limb/circumference.)

Sometimes this one is quite hard to avoid unless one opts for very smooth and somewhat greater lack of sharpness/clarity in the end image - but if you want to remove said you can lasso the planet and then "Select>modify>contract" an appropriate number of pixels followed by "Select>inverse" and then apply a little Gaussian blur to remove this.....that and modest destaturating of that very edge are sometimes helpfull for both this and when RGB aligning the channels on detail in the central region of the planet leaves a slight misalignment on the limbs (which it can often do.)

This is all best done either before reducing the image scale back down to your desired size, or with the aid of the magnifying tool...I see many, many fine images here where that procedure or something similar has been applied to them :)

Not being argumentative on this Ed but I fail to see how you could prescribe any of these effects to "rolling shutter" - I've shot a couple of "hi-res" images now - the ones in my last thread and again last night (will post later :)) and so far I don't see any of this.....which is why I challenge that assumption about the rolling shutter! :)

All good discussion material methinks! :grin:

# edit: corrected my text...

#30 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 07 December 2012 - 06:55 PM

I agree with everything you say could be the cause of the rings Darryl.

#31 DesertRat

DesertRat

    Fly Me to the Moon

  • *****
  • Posts: 5228
  • Joined: 18 Jun 2006
  • Loc: Valley of the Sun

Posted 07 December 2012 - 07:38 PM

Good one Ed! We need to humble Darryl sometimes! But this time I think Darryl is on to something. In some seeing conditions its possible a rolling shutter could create some problems, but honestly I'm not sure we have seen an example of this yet.

You can have seeing of the gods and still get diffraction ring limb effects. Oversharpening makes it more obvious. In fact the better the seeing the more obvious they become. But in that case one should not sharpen as much. A scope out of collimation will make the effect worse on one side.

Actually in poor seeing these go away, you have a fuzzier ball with no clear edges which when sharpened would have shown a ring (single diffraction ring) effect.

The last image of the 4 that wenjha (is that Sam?) taken at lowest gain shows a different phenomena due to non linear response at the low end. This is something any camera can show under the right conditions unless fitted with very expensive electronics. If you carefully play with levels you can see it in the other images as well, but at a much lower level. The different phenomena I refer to is the multiple adjacent rings at the limb sometimes called onion rings.

For people starting out in this hobby I always recommend to push gain to almost uncomfortable levels. Then you can back off if you please. Interestingly it is often easier to focus a grainier image on the screen as it puts the eye-brain into a different mode. But the main thing it does is to put the bulk of your samples in the linear range of the camera, and besides the real payoff in lucky imaging is having lots of frames which will control noise when stacked. More gain usually means more samples as you generally increase the frame rate.

Glenn

#32 wenjha

wenjha

    Vendor

  • -----
  • Vendors
  • Posts: 737
  • Joined: 24 Sep 2008
  • Loc: SuZhou China

Posted 07 December 2012 - 07:47 PM

I forget to attach one in good seeing
Yes, Ed experiment is the best way to prove it.
this is my test to find the best setting to capture jupiter.
From my test I think exposure below 20ms will be a good option.
And Emil is right that 50 of gamma will be the linely response value.

Attached Files



#33 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 07 December 2012 - 08:16 PM

I was not trying to humble Daryl, I do agree with him. Those are all causes for rings in images, and there is no arguing against his statments. My original statment was weak "ring you show may be an artifact" and I sure as the heck am not stepping out any further on that branch :-)

#34 wenjha

wenjha

    Vendor

  • -----
  • Vendors
  • Posts: 737
  • Joined: 24 Sep 2008
  • Loc: SuZhou China

Posted 07 December 2012 - 08:44 PM

Hi Glenn
Yes, I am Sam.
I am not fully agree with you.
because the ring always apear in a poor image.not very good one.
Also I found that if I stack too many frames when seeing is bad can cause onion rings too.
So I am sure it come from bad images.

And it has no bussniess with gloable shut or progressive shut. because I saw it when I use spc900nc.

#35 Kokatha man

Kokatha man

    Fly Me to the Moon

  • *****
  • Posts: 6995
  • Joined: 13 Sep 2009
  • Loc: "cooker-ta man" downunda...

Posted 07 December 2012 - 09:10 PM

Heh-hee fellas - I'm not averse to a little humbling and I make my share of mistakes and errant claims..! :rainbow: :lol:

I appreciate discussions where we can investigate various issues on the topic of our passion - planetary imaging.

On that note I agree to a certain point on "diffraction ring limb effects" Glenn, but I have almost never seen them per se personally on Jupiter (Mar most certainly!)

I say "per se" because I have no real idea whether those that appear with over-sharpening are in fact already there waiting to be "brought out" so to speak, but I do know in (say for example) the images I got last week that were in "good" seeing it was very hard to get any limb artefact, even pushing the wavelets or deconvolution OTT. :question:

Anyways, "humble away" if it's necessary fellas.....as long as we all learn something! :grin:

#36 DesertRat

DesertRat

    Fly Me to the Moon

  • *****
  • Posts: 5228
  • Joined: 18 Jun 2006
  • Loc: Valley of the Sun

Posted 07 December 2012 - 09:44 PM

Hi Sam,

The images you just posted all show sharpening effects on the right side, the bright limb of Jupiter on that date. That is magnified by diffraction (its hidden in the stacked image). If a scope is out of collimation (in the 'right' direction) it will make them stronger. But you can also sharpen a computer generated perfect gray circle and get that effect as Darryl was commenting on overshapening.

The onion ring effect is a different phenomena caused by non linear operation. I've never seen that result from poor seeing when the settings are correct. Onion rings are multiple rings usually about the outside of a planet, but some of us have seen them so bad they cover the entire planet! I suppose if you had some kind of pathological seeing condition where the planet was throbing in size at semi-discrete sizes you could get something like that. :question:

Darryl, yes I was just joking with you. This kind of thread is what makes this forum useful!

Glenn

#37 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 12 December 2012 - 12:05 AM

Update. Took the camera out tonight. I didn't notice that all setting in Firecapture were saved for each color channel, and the green channel was set at 12. I thought the Gamma setting was for all channels. I should have known better, the green channel was the channel that rings were occurring the worst. After changing the setting tonight, no rings at all. The problem did lie between the ground and the computer.

#38 zAmbonii

zAmbonii

    Vanguard

  • -----
  • Posts: 2420
  • Joined: 19 Jan 2008
  • Loc: Ypsilanti, MI

Posted 12 December 2012 - 03:58 AM

Any decent images?

Seeing was supposed to be poor, so I didn't bother. Will probably get the scope out tonight if it stays clear like it says.

#39 Kokatha man

Kokatha man

    Fly Me to the Moon

  • *****
  • Posts: 6995
  • Joined: 13 Sep 2009
  • Loc: "cooker-ta man" downunda...

Posted 12 December 2012 - 05:31 AM

Update. Took the camera out tonight. I didn't notice that all setting in Firecapture were saved for each color channel, and the green channel was set at 12. I thought the Gamma setting was for all channels. I should have known better, the green channel was the channel that rings were occurring the worst. After changing the setting tonight, no rings at all. The problem did lie between the ground and the computer.


.....that's why Sam & me harassed Torsten so much :grin: to get FireCapture fully-compatible with the ASI120 cameras Ed.....it's the best capture software there is imho, and a real credit to Torsten..! :waytogo:

#40 MvZ

MvZ

    Surveyor 1

  • *****
  • Posts: 1583
  • Joined: 03 Apr 2007
  • Loc: The Netherlands

Posted 12 December 2012 - 05:48 AM

The onion ring effect is a different phenomena caused by non linear operation. I've never seen that result from poor seeing when the settings are correct.


I agree with this. I have processed many images (with other cameras), many under poor seeing conditions, but never found onion rings with correct camera settings. If it was caused by bad seeing, I would have seen them. I have not, so it is not caused by poor seeing. Perhaps it is only enhanced by the camera under poor seeing conditions. In that case I suspect adding more noise to the raw images (gain up) should deal with the problem, forcing the pixels to not have any quantization problems (basically increasing the variability of the pixels, allowing for a wider dynamic range after stacking).

In practice I have not found any of these problems at all though with the camera so far.

#41 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 12 December 2012 - 01:17 PM

Z,

Nothing good. The images at capture looked fantastic, with little planet undulations. I was excited about the images, but in the end below was all I could get. there was considerable upper atmosphere scintillation stopping fine detail from coming out. Tonight CSC shows not so good, Calsky says above average.

Attached Files



#42 zAmbonii

zAmbonii

    Vanguard

  • -----
  • Posts: 2420
  • Joined: 19 Jan 2008
  • Loc: Ypsilanti, MI

Posted 12 December 2012 - 02:50 PM

I would be happy with that image with my webcam on a less than average night :). I'm a little bummed because when I got home there was a DHL sticker on my door. I missed the ASI120MC delivery by about 30 minutes and will have to wait until tomorrow to get it in my hands.

Doesn't look like there will be another decent night until next week :(.

Probably going to use tonight to experiment a little. I need to get the latest FireCapture loaded up so I can get used to using it, and mess around with the features some.

#43 edsplace

edsplace

    Ranger 4

  • *****
  • Posts: 353
  • Joined: 02 Nov 2011

Posted 12 December 2012 - 03:02 PM

You can drive to the DHL hub and they will give you camera. I have done that before, I think the courier is based in the Detroit Metro area.

#44 zAmbonii

zAmbonii

    Vanguard

  • -----
  • Posts: 2420
  • Joined: 19 Jan 2008
  • Loc: Ypsilanti, MI

Posted 12 December 2012 - 05:43 PM

I gave them a call and could only pick it up in the morning. They said their drivers were out late for pickups because of the holiday season. Their hub is over by DTW so it wouldn't have been too far of a drive. I'll just wait till they deliver it again tomorrow :p






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics