Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

ZWO ASI294 MC pro

  • Please log in to reply
254 replies to this topic

#101 barrett_flansburg

barrett_flansburg

    Explorer 1

  • -----
  • Posts: 79
  • Joined: 30 Dec 2014

Posted 01 May 2018 - 01:36 PM

Sounds like a crop factor of 1.5x to me, since the baseline is a fullframe 36mm x 24mm sensor. 36mm = 1.5 x 24mm and 24mm = 1.5 x 16mm. So your 480mm telescope with the 294 sensor would behave like a 720mm lens on a fullframe camera in terms of field of view. 



#102 jor223

jor223

    Lift Off

  • -----
  • Posts: 7
  • Joined: 26 Sep 2017

Posted 01 May 2018 - 03:21 PM

Sounds like a crop factor of 1.5x to me, since the baseline is a fullframe 36mm x 24mm sensor. 36mm = 1.5 x 24mm and 24mm = 1.5 x 16mm. So your 480mm telescope with the 294 sensor would behave like a 720mm lens on a fullframe camera in terms of field of view. 

Thank you Barry,

 

I made a mistake, I meant to say 19 x 13mm. According to the specs this is the sensor size of the ASI 294 mc pro. I am just starting and trying to decide between the Explore Scientific ED80 or the 102, both carbon fiber and the price difference right now is about $300. The fact that this camera would double the focal length (in terms of field of view) is something to consider I suppose.

Any advise would be greatly appreciated.

Thanks again!


  • akulapanam likes this

#103 Foobaria

Foobaria

    Viking 1

  • *****
  • Posts: 510
  • Joined: 16 Apr 2017
  • Loc: New Mexico, USA

Posted 01 May 2018 - 04:02 PM

Thank you Barry,

 

I made a mistake, I meant to say 19 x 13mm. According to the specs this is the sensor size of the ASI 294 mc pro. I am just starting and trying to decide between the Explore Scientific ED80 or the 102, both carbon fiber and the price difference right now is about $300. The fact that this camera would double the focal length (in terms of field of view) is something to consider I suppose.

Any advise would be greatly appreciated.

Thanks again!

Please get the 80, but i started with a 102 then went to an 80, so much easier to use, better f ratio, lighter, etc., many reasons to go with an 80 over a 102.   The 80 is cheaper too.  And it takes a wider view often. 


Edited by Foobaria, 01 May 2018 - 04:29 PM.


#104 jor223

jor223

    Lift Off

  • -----
  • Posts: 7
  • Joined: 26 Sep 2017

Posted 01 May 2018 - 05:44 PM

Please get the 80, but i started with a 102 then went to an 80, so much easier to use, better f ratio, lighter, etc., many reasons to go with an 80 over a 102.   The 80 is cheaper too.  And it takes a wider view often. 

The ones that you mention are very good reasons to get the 80, also your experience with both is very important. I will follow your advise. Thank you so much!

 

Jorge



#105 bulrichl

bulrichl

    Vostok 1

  • -----
  • Posts: 139
  • Joined: 27 May 2018
  • Loc: La Palma (Canary Islands)

Posted 28 May 2018 - 09:36 AM

Hi,

 

it has become rather quiet on this topic lately. I am new to this board and want to introduce myself. I was using a Takahashi FSQ 106N with a Canon 600D for some time. Due to warm summer nights here on the Canary Islands I wanted a cooled camera in order to diminish thermal noise as possible. So I purchased a ASI294MC Pro which was used since January 2018. As a result of unusual cloudy skies in the last months there were only few occasions suitable for astrophotography. Some results are:

 

NGC 2023:           32 x 300 s
M 78:                   52 x 300 s
M 81, M 82:        190 x 150 s
M 84, M 86:          95 x 150 s
IC 4603, IC 4604: 34 x 300 s

 

All frames were taken at gain 120 and a temperature of -15 °C.

 

Unfortunately I am experiencing the same colored background artifacts that were shown in this thread. This artifact is neither caused by light pollution nor is it IFN signal: I integrated 50 frames before meridian flip and 60 frames thereafter (no rotator was used). The problematic background was at the same sensor positions, which is evident in the appended images ("Image_1.JPG" and "Image_2.JPG", STF Autostretch applied in PixInisght).

 

Image_1.JPG

Image_2.JPG

 

Of course, this problem is worse with images containing extended regions of background, so it manifests itself especially with widefield images. It limits the extent to which the image can be stretched, and makes imaging of very weak structures like IFN nearly impossible.

 

Apart from that the camera seems really amazing to me, so I would like to know whether there are new ideas of avoiding these artifacts.

 

@Andy:
Did you finally give up with this camera or did you find a way to manage this issue? I am very curious.

 

Bernd



#106 A. Viegas

A. Viegas

    Mercury-Atlas

  • *****
  • Posts: 2994
  • Joined: 05 Mar 2012
  • Loc: New York City/ CT

Posted 28 May 2018 - 01:29 PM

Hi Bernd. Did you take darks immediately after the lights or did you use a master dark ? Also it seems like the 294 is best utilized at lower exposure lengths and slightly higher gains. I use 120s and gain 200 and I take darks right after the exposure of lights and I don't have that gradient.

Al

#107 jgraham

jgraham

    ISS

  • *****
  • Posts: 20193
  • Joined: 02 Dec 2004
  • Loc: Miami Valley Astronomical Society

Posted 28 May 2018 - 03:23 PM

I do all of my imaging from my light polluted backyard so I frequently deal with odd gradients of all sorts. Something like this is easily fixed with a synthetic flat, it will remove the gradients and the color from the background. It can limit how hard you push the processing, but that comes with the territory for me.

 

Love my ASI294MC Pro!



#108 John Miele

John Miele

    Gemini

  • *****
  • Posts: 3411
  • Joined: 29 May 2005
  • Loc: North Alabama

Posted 28 May 2018 - 06:43 PM

Hi John,

 

Will a regular flat remove the gradients you speak of or do you need to use a synthetic flat? And if so, could you briefly describe how you create one? I have an ASI071 just sitting here waiting for a clear sky and 1st light and I will likely have to deal with gradients as well. Thanks...John

 

Edit: Oh I just found the synthetic flat tool in Nebulosity. Is that what you use?

 

Edit 2: One last question...after you use the synthetic flat, do you also use a regular flat for the dust bunnies?


Edited by John Miele, 28 May 2018 - 06:59 PM.


#109 andysea

andysea

    Soyuz

  • *****
  • topic starter
  • Posts: 3515
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 28 May 2018 - 08:37 PM

Bernd, first off nice images!
I think I have been able to manage the uneven background by cooling slightly less, -15, and doing shorter subs, 120s. There is some residual thermal noise but it’s very low and usually It doesn’t show up on a normally stretched image. I also took new flats with aluminum foil covering the front of the camera. Now I seem to get better data.

#110 AhBok

AhBok

    Vanguard

  • *****
  • Posts: 2266
  • Joined: 02 Dec 2010
  • Loc: Lakeland, TN

Posted 28 May 2018 - 09:17 PM

I also worked through my problems similarly. I was taking my lights at night and my darks, dark flats and flats during the daytime. I thought I had everything covered well, but finally figured out I was experiencing light leaks. I am now using a Newtonian and was getting light in through the mirror. I covered everything with aluminum foil to find the leaks. I now take my calibration frames at night or in a darkened room, with my PC screen partially covered. The gradient I have now is mostly due to light pollution which is much easier to deal with in post. I also keep my exposures down to 2 minutes, though I am sure I could go much longer at a darker site.

 

AFAIAC, problem solved and it was my lack of experience with this particular camera. Doggone it is sensitive!



#111 jgraham

jgraham

    ISS

  • *****
  • Posts: 20193
  • Joined: 02 Dec 2004
  • Loc: Miami Valley Astronomical Society

Posted 28 May 2018 - 09:41 PM

I use regular flats most of the time. The synthetic flat tool in Nebulosity works very well on typical symmetrical gradients, but struggles with some of the odd gradients that you can get from passing scrum and light pollution. When none of the standard tools work, a synthetic flat is the last option, but it can be a useful tool for salvaging a useable image. I have a PDF that I wrote a couple of years ago, but it is too large to upload. I'll see if I can condense it down to just the text. Briefly, I use standard flats to remove dust motes and the usual gradients from the optical system, I then make a foreground mask and use that to delete the foreground using a representative region of the background as the fill color. I then smooth this background image using a median filter to make the synthetic flat. This flat will contain all of the oddball gradients and the color of the gradients. I then subtract this from the image and correct the resulting offsets in the black and white points. Once you get the hang of it, it is easy and very effective.

 



#112 bulrichl

bulrichl

    Vostok 1

  • -----
  • Posts: 139
  • Joined: 27 May 2018
  • Loc: La Palma (Canary Islands)

Posted 29 May 2018 - 06:33 AM

@A. Viegas:
I used 110 darks, 111 flat-darks and 40 flats. The dark frames were taken separately. At light frame acquisition the difference between camera  and ambient temperature was 29 - 27 degrees, and the maximal cooling power was only about 50 %. Dithering was applied. My workflow (in PixInsight): Image calibration with MasterDark and MasterFlat [Flats calibrated with MasterFlat-Dark], Debayer, Alignment, Integration).
The artifact definitely is not present in my MasterDark. The debayered MasterDark (same stretching applied as in the integration) shows 'amp glow', but not a trace of colored background is detectable in it. Furthermore, when I subtract the bias-offset from each light frame and then calibrate with MasterFlat, the same colored background with the same strength results after debayering, alignment and integration. So this artifact is only in the light frames, and I consider the explanation of ZWO (thermal differences between light and dark frame acquisition) wrong.

 

@jgraham:
As I showed already, this "odd background" is not caused by light pollution.
I guess you are referring to background modelization as "synthetic flat"? PixInsight has the powerful processes DynamicBackgroundExtraction [DBE] and AutomaticBackgroundExtractor [ABE]. However, I was not successful in removing this artifact completely with DBE. Furthermore, very weak structures (like IFN) might be removed by these techniques as well.

 

@andysea:
Thank you for the kind words regarding my images.
> I think I have been able to manage the uneven background by cooling slightly less, -15, and doing shorter subs, 120s.

> There is some residual thermal noise but it’s very low and usually It doesn’t show up on a normally stretched image.
In the case of the 2 shown images the cooling was moderate (cooling power about 50 %) and the exposure time was only slightly more (150 s).

 

> I also took new flats with aluminum foil covering the front of the camera. Now I seem to get better data.
Do you mean new dark frames?

 

@AhBok:
> I was taking my lights at night and my darks, dark flats and flats during the daytime.
So did I.

 

> I thought I had everything covered well, but finally figured out I was experiencing light leaks. I am now using a Newtonian and was getting light in through the mirror.

> I covered everything with aluminum foil to find the leaks. I now take my calibration frames at night or in a darkened room, with my PC screen partially covered.
Dew cap and top cover of my FSQ106N are made of metal. Between focuser and camera, everything is screwed together. In fact not a trace of colored background is detectable in my MasterDarks (see my answer to A. Viegas). So I rule out that light leaks are causing this in my case.


I did not mean to discredit this camera. However, I am intrigued by the fact that this artifact is so well reproducible. Here is another integration of 190 x 150 s, taken one month before (STF Autostretch applied):

 

Image_3.JPG

 

Compared with the 2 images above the artifact again appears in the same regions of the sensor.

 

Thanks to all who responded to my post.

 

Bernd

 



#113 AhBok

AhBok

    Vanguard

  • *****
  • Posts: 2266
  • Joined: 02 Dec 2010
  • Loc: Lakeland, TN

Posted 29 May 2018 - 10:08 AM

Bernd,

Ok, I see your point. I think I’ve been looking at this superficially. I’ve been troubleshooting this as a gradient I could not fix in post. This is how I found that my calibration frames were experiencing a light leakage. Once that was fixed, I was left with a gradient that is easily fixed using the wipe function in StarTools. I assumed the gradient was LP because it responded well to gradient removal. I’ll do similarly and see if the gradient pattern I now have is a fixed pattern. If so, that is a shame, but mine is still easily fixed in post.

#114 jgraham

jgraham

    ISS

  • *****
  • Posts: 20193
  • Joined: 02 Dec 2004
  • Loc: Miami Valley Astronomical Society

Posted 29 May 2018 - 11:44 AM

"... very weak structures (like IFN) might be removed by these techniques as well."

 

Yep, synthetic flats work great at removing gradients, but there's not a good way to discriminate between what's a gradient and what's not. Areas that are awash in H-alpha cane be tough to deal with. However, under my sky conditions that is rarely a problem.



#115 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 11:50 AM

The thing that is curious to me is, the pattern seems to be quite consistent, and yet it is still not removed with dark calibration. I am having a hard time understanding why that is. If the pattern is so consistent that it shows up the same night after night, even days or weeks apart, why can it not be calibrated out?


  • Merc and jdupton like this

#116 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 12:46 PM

Does anyone have any data they could share? I just want to fiddle with it a bit and see if there is a way to fix the issue with some calibration and maybe some pixel math.



#117 andysea

andysea

    Soyuz

  • *****
  • topic starter
  • Posts: 3515
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 29 May 2018 - 12:51 PM

Bernd, yes sorry I meant to say that I took new darks not flats.

 

Jon,

That is indeed curious and I don't quite understand why it's happening. The pattern in my earlier data sets taken at -20 with 300s subs is actually slightly different from night to night. That is what lead me to believe that it was some condensation related issue, also partly due to the fact that the shape of the pattern was irregular and more organic. ZWO however is adamant about it being caused by uneven cooling and about environment temperature having an effect on it.

 

That being said, I still was able to get images that I considered very good. Especially the new ones taken at -15 with 120s subs.

I know that QHY is working on their version of the same camera and their release seems to be getting pushed back more and more. I wonder if they are running into the same calibration issue.

 

I have a lot of data that is ready to be shared. It's 5Gb of files and too big for my free dropbox account. I'll find another way and post the link.


  • ito304 likes this

#118 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 12:59 PM

Hmm, interesting. If it is due to uneven cooling due to a too-small TEC, I think that is a product defect that ZWO should fix. The TEC does need to be large enough to properly cool the whole sensor, and do so consistently. 

 

But it is still curious. Lets assume that the pattern does change slightly. I would think that calibration would mostly take care of the differences...unless I am just not quite understanding the magnitude of how much the pattern changes from night to night?



#119 andysea

andysea

    Soyuz

  • *****
  • topic starter
  • Posts: 3515
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 29 May 2018 - 03:34 PM

I agree with you Jon.
Following ZWO's theory I took darks at about the same ambient temperature as my lights, that should have mitigated the issue but it didn't seem to make much of a difference. 

Regarding the TEC cooling, I don't know exactly what the details are but apparently the 294 sensor does not allow for placing the cooler directly on the back of the sensor itself. I am not quite understanding this and seeing the actual sensor would probably help in this regard.



#120 bulrichl

bulrichl

    Vostok 1

  • -----
  • Posts: 139
  • Joined: 27 May 2018
  • Loc: La Palma (Canary Islands)

Posted 29 May 2018 - 06:01 PM

Hi Jon,

 

OK, here is a link to a zip file with:
- 4 light frames, 2 before / 2 after m.f. (CFA data, FIT format),
- MasterDark (CFA data, XISF format),
- MasterFlat (CFA data, XISF format),
- 2 integrations, 1 before / 1 after m.f., (RGB data, XISF format).

 

The MasterDark is built of 100 dark frames, the Flat frames are calibrated with a MasterFlat-Dark built of 111 Flat-Darks, the MasterFlat is built of 40 calibrated Flat frames. The first integration is made of 50, the second integration of 57 calibrated, debayered, aligned light frames.

 

https://www.dropbox....ndmann.zip?dl=0

 

Let me know if you see indications of inconsistent calibration.

 

Cheers,

Bernd


  • Jon Rista likes this

#121 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 06:52 PM

I agree with you Jon.
Following ZWO's theory I took darks at about the same ambient temperature as my lights, that should have mitigated the issue but it didn't seem to make much of a difference. 

Regarding the TEC cooling, I don't know exactly what the details are but apparently the 294 sensor does not allow for placing the cooler directly on the back of the sensor itself. I am not quite understanding this and seeing the actual sensor would probably help in this regard.

Hmm...I think Sony sensors may often come on their own little PCB, and the sensor itself is mounted on that PCB, with cover glass and everything already in place. You then just have to integrate that little board into whatever device you need it to be a part of. So, I guess I could believe that there may not be an easy way to attach the TEC directly to the back of the sensor, if that is how that particular sensor comes from Sony. If that IS the case, it might make that particular sensor a bit less viable for astrophotography than some others, sadly...

 

 

Regarding mitigation options for the issue. Have you by chance tried to apply a slight convolution filter to a master dark, then just subtract that convolved version of the dark from an individual light with PixelMath (you might also need to first add a pedestal, which could be done by adding the median or the mean of the convolved dark first)?



#122 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 06:58 PM

Hi Jon,

 

OK, here is a link to a zip file with:
- 4 light frames, 2 before / 2 after m.f. (CFA data, FIT format),
- MasterDark (CFA data, XISF format),
- MasterFlat (CFA data, XISF format),
- 2 integrations, 1 before / 1 after m.f., (RGB data, XISF format).

 

The MasterDark is built of 100 dark frames, the Flat frames are calibrated with a MasterFlat-Dark built of 111 Flat-Darks, the MasterFlat is built of 40 calibrated Flat frames. The first integration is made of 50, the second integration of 57 calibrated, debayered, aligned light frames.

 

https://www.dropbox....ndmann.zip?dl=0

 

Let me know if you see indications of inconsistent calibration.

 

Cheers,

Bernd

Any chance I could get some individual dark frames from you as well? I do not need 100...but, 10 would probably do, to get enough of a statistical feel for discrepancies between the dark frames themselves and the lights.



#123 jdupton

jdupton

    Surveyor 1

  • *****
  • Posts: 1877
  • Joined: 21 Nov 2010
  • Loc: Central Texas, USA

Posted 29 May 2018 - 07:19 PM

Jon,

 

Hmm...I think Sony sensors may often come on their own little PCB, and the sensor itself is mounted on that PCB, with cover glass and everything already in place. You then just have to integrate that little board into whatever device you need it to be a part of. So, I guess I could believe that there may not be an easy way to attach the TEC directly to the back of the sensor, if that is how that particular sensor comes from Sony. If that IS the case, it might make that particular sensor a bit less viable for astrophotography than some others, sadly...

 

 

Regarding mitigation options for the issue. Have you by chance tried to apply a slight convolution filter to a master dark, then just subtract that convolved version of the dark from an individual light with PixelMath (you might also need to first add a pedestal, which could be done by adding the median or the mean of the convolved dark first)?

   I think you have hit on the root of the problem. The information on Sony's Product Website says the IMX294CJK sensor is packaged in a 248 pin LGA package. That means that it has to be mounted directly onto a PCB since all pins are only accessible from the bottom side (opposite side from the sensor face) of the chip. Any camera using this chip would seem to have to cool it through the attached PCB. That in itself makes the task difficult unless a company goes to the added expense to have a custom ceramic intermediate pseudo-BGA "PCB" built to take the leads to the edges rather than the back face.

 

   No wonder companies are having trouble designing a camera around this wonderful sensor.

 

 

John


Edited by jdupton, 29 May 2018 - 10:35 PM.

  • Jon Rista likes this

#124 rockstarbill

rockstarbill

    Fly Me to the Moon

  • *****
  • Posts: 6155
  • Joined: 16 Jul 2013
  • Loc: Snohomish, WA

Posted 29 May 2018 - 07:33 PM

Any chance I could get some individual dark frames from you as well? I do not need 100...but, 10 would probably do, to get enough of a statistical feel for discrepancies between the dark frames themselves and the lights.

I can take as many as you want. What temp and how many. I assume Unity gain?



#125 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 23593
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 May 2018 - 07:35 PM

I can take as many as you want. What temp and how many. I assume Unity gain?

Whatever settings you intend to actually use the camera at, really.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics