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

Sony IMX183 mono test thread - ASI, QHY, etc.

  • Please log in to reply
1005 replies to this topic

#76 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 12:47 PM

 

 

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

I don't really think either camera would really be all that great at f/10...however, either should be ok at f/7, with the ASI1600 having the benefit of a larger FoV. 

 

As for microlens diffraction. With VERY bright stars, I have seen a rather interesting diffraction artifact (I need to get some test data to show it), but I haven't seen the same kind of microlens reflections as with the ASI1600. I don't know exactly what causes the issue in the ASI1600, so I don't know whats different about the ASI183, but if you encounter any sensor diffraction with the 183 it's a more pleasing effect.

 

from what I have read the cover glass over the 1600 sensor is not ar coated, per Sam this is how the sensor is made so zwo can't do anything about it......was just curious if the sony sensor had ar coated cover glass or not and might have not have that same problem.....

 

https://zwoug.org/vi...bbb86912ad3fe25

 

I am far more likely to image at f7 or f2.1 , makes me lean towards the 183, with the smaller pixels it might allow me to image a few midsize targets at f2/1 rather than f/7 , since the higher resolution would allow me to crop a bit more of the image, and imaging at f/2.1 is soooo much easier....

 

thanks for your reply

 

Well, that's the assumption, that the cover glass is not coated. I don't know that anyone knows for sure what the exact cause of the microlens diffraction is, though, is my point. 

 

I don't know if the cover glass of the IMX183 is coated or not either. I don't see any visual difference between the two cameras...nothing that indicates one is multicoated and the other not. I have seen diffraction effects with the IMX183 on bright stars...but as mentioned, it is a more interesting pattern without the grid of microlenses around the star. 


  • Pug likes this

#77 suvowner

suvowner

    Ranger 4

  • *****
  • Posts: 362
  • Joined: 22 May 2016
  • Loc: Arkansas

Posted 02 December 2017 - 01:13 PM

 

 

 

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

I don't really think either camera would really be all that great at f/10...however, either should be ok at f/7, with the ASI1600 having the benefit of a larger FoV. 

 

As for microlens diffraction. With VERY bright stars, I have seen a rather interesting diffraction artifact (I need to get some test data to show it), but I haven't seen the same kind of microlens reflections as with the ASI1600. I don't know exactly what causes the issue in the ASI1600, so I don't know whats different about the ASI183, but if you encounter any sensor diffraction with the 183 it's a more pleasing effect.

 

from what I have read the cover glass over the 1600 sensor is not ar coated, per Sam this is how the sensor is made so zwo can't do anything about it......was just curious if the sony sensor had ar coated cover glass or not and might have not have that same problem.....

 

https://zwoug.org/vi...bbb86912ad3fe25

 

I am far more likely to image at f7 or f2.1 , makes me lean towards the 183, with the smaller pixels it might allow me to image a few midsize targets at f2/1 rather than f/7 , since the higher resolution would allow me to crop a bit more of the image, and imaging at f/2.1 is soooo much easier....

 

thanks for your reply

 

Well, that's the assumption, that the cover glass is not coated. I don't know that anyone knows for sure what the exact cause of the microlens diffraction is, though, is my point. 

 

I don't know if the cover glass of the IMX183 is coated or not either. I don't see any visual difference between the two cameras...nothing that indicates one is multicoated and the other not. I have seen diffraction effects with the IMX183 on bright stars...but as mentioned, it is a more interesting pattern without the grid of microlenses around the star. 

 

ah ok I see.........I wonder if the back illuminated design of the sony sensor is making a difference...

 

here is an interesting company in San Diego that removes sensor cover glass...it seems it would be unnecessary since the sensor is behind the ar protect window.....wonder what they would charge ??

 

http://pacificxray.c...ensor-services/



#78 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 01:18 PM

 

 

 

 

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

I don't really think either camera would really be all that great at f/10...however, either should be ok at f/7, with the ASI1600 having the benefit of a larger FoV. 

 

As for microlens diffraction. With VERY bright stars, I have seen a rather interesting diffraction artifact (I need to get some test data to show it), but I haven't seen the same kind of microlens reflections as with the ASI1600. I don't know exactly what causes the issue in the ASI1600, so I don't know whats different about the ASI183, but if you encounter any sensor diffraction with the 183 it's a more pleasing effect.

 

from what I have read the cover glass over the 1600 sensor is not ar coated, per Sam this is how the sensor is made so zwo can't do anything about it......was just curious if the sony sensor had ar coated cover glass or not and might have not have that same problem.....

 

https://zwoug.org/vi...bbb86912ad3fe25

 

I am far more likely to image at f7 or f2.1 , makes me lean towards the 183, with the smaller pixels it might allow me to image a few midsize targets at f2/1 rather than f/7 , since the higher resolution would allow me to crop a bit more of the image, and imaging at f/2.1 is soooo much easier....

 

thanks for your reply

 

Well, that's the assumption, that the cover glass is not coated. I don't know that anyone knows for sure what the exact cause of the microlens diffraction is, though, is my point. 

 

I don't know if the cover glass of the IMX183 is coated or not either. I don't see any visual difference between the two cameras...nothing that indicates one is multicoated and the other not. I have seen diffraction effects with the IMX183 on bright stars...but as mentioned, it is a more interesting pattern without the grid of microlenses around the star. 

 

ah ok I see.........I wonder if the back illuminated design of the sony sensor is making a difference...

 

here is an interesting company in San Diego that removes sensor cover glass...it seems it would be unnecessary since the sensor is behind the ar protect window.....wonder what they would charge ??

 

http://pacificxray.c...ensor-services/

 

I would still want the cover glass. I would just want to replace it with one that is definitely AR coated. You wouldn't want to leave the sensor itself exposed, as if you ever needed to clean dust motes off and such, you would have to touch the sensor itself...not recommended (they are quite fragile, and the CFA and microlenses often just rub off!)


  • Pug likes this

#79 Stamos

Stamos

    Vostok 1

  • -----
  • Posts: 145
  • Joined: 30 Oct 2015
  • Loc: Athens, Greece

Posted 02 December 2017 - 05:04 PM

Just look at the dark frame of QHY183C. Only glow of on middle of right side still exist. But all the corner/ top/ down glow is completely removed by our technology. 

 

 

Qiu, are there any circuitry differences between the color and the mono version of this sensor?

 

It would be very nice if you could share a couple of raw long exposure dark frames to make a more direct comparison between the cameras.



#80 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 05:08 PM

Quick FYI, I asked ZWO about the FPGA-based glow reduction, if they had done anything like that. It sounds like they have already been doing some of that with their cameras, but in the last response it sounds like they were able to either eliminate or greatly reduce the three corner glows. Sounds like it is a firmware thing, so it might be fixable just with firmware update. I don't yet know if that is something the user could do, or if the camera would have to be sent in. In any case, sounds like there may be some improvements in amp glow coming for the ZWO cameras. Hopefully more soon...


  • Stamos likes this

#81 andysea

andysea

    Soyuz

  • *****
  • Posts: 3511
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 02 December 2017 - 05:22 PM

That's good to hear. My ASI294 has a very similar glow, perhaps just a bit less pronounced.



#82 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 05:26 PM

That's good to hear. My ASI294 has a very similar glow, perhaps just a bit less pronounced.

In the data I tested for the ASI294, it seemed to have the same glows, only the right side starburst was higher up the frame. Actually, the ASI294 seemed to already be missing the upper left corner glow, and ZWO did say they were already disabling some of the glow sources. Sounds like they may have found a few more, though, and if they can eliminate the two lower corner glows for the ASI183, they should be able to do it for all the rest of their cameras, as those glows seem to look identical across all the Sony ASI cameras i've tested.


  • Pug likes this

#83 andysea

andysea

    Soyuz

  • *****
  • Posts: 3511
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 02 December 2017 - 05:40 PM

I think you're correct. I don't have the dark frame in front of me right now but I remember the two bottom corner ones, fairly small, and the large starburst glow on the right.

Hopefully it will be corrected via a user installed firmware update.


Edited by andysea, 02 December 2017 - 05:41 PM.


#84 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 05:46 PM

I do want to stress, the difference in noise with the amp glows + calibration is imperceptible in a single frame. Once you stack, all the noise gets averaged down and the signal grows, so it's even less of an issue. I think the main use cases for eliminating amp glow are going to cater more towards the live view stuff (EAA) and planetary, and very short exposure imaging with camera-controlled exposures. For DSO, I don't think there is going to be any real change in IQ with or without amp glow prevention.



#85 andysea

andysea

    Soyuz

  • *****
  • Posts: 3511
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 02 December 2017 - 06:02 PM

Yeah that was pretty much my takeaway from all the threads that discuss the amp glow.

I have to say the IMX183 mono looks very interesting. I might get one of those cameras once they hit the market. It seems to be a great match for my FS-60 or even the FSQ106/reducer combo.


  • poobie likes this

#86 rafiosso

rafiosso

    Lift Off

  • -----
  • Posts: 16
  • Joined: 11 Nov 2017

Posted 05 December 2017 - 03:43 AM

Jon, thank You for putting so much work in testing. I have imx178 uncooled and like it a lot, but wanted something with bigger chip. The imx183M looks like a nice Christmas gift for me smile.gif


  • Pug likes this

#87 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 05 December 2017 - 11:27 PM

You are welcome. I actually have more to come. I've been trying to acquire some more data, however my mount is acting up again, so I've lost some nights. Tonight is looking ok (according to Astrospheric, I'm in a gap between jetstreams, and seeing is pretty good), so hopefully I'll be able to finish at least one image, maybe two. These will be images with 10 minute subs.

 

I am also putting together some demonstrations of quantization error, what kinds of signals it affects, and what swamping the read noise (and therefor the quantization error) actually looks like, and why it doesn't take much to average out the quantization even with a 12 bit camera.


  • TimN, dvalid, Pug and 2 others like this

#88 NorthField

NorthField

    Viking 1

  • *****
  • Posts: 924
  • Joined: 01 Jun 2017
  • Loc: SW Missouri

Posted 05 December 2017 - 11:41 PM

Do you think this camera would be a good fit with a 100 mm, 580 fl refractor? Resolution is my new “must have”

I try to read as much as possible and not ask questions, but...

#89 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 05 December 2017 - 11:53 PM

Do you think this camera would be a good fit with a 100 mm, 580 fl refractor? Resolution is my new “must have”

I try to read as much as possible and not ask questions, but...

Sure! I think it would fit just fine. I'm using a 150mm aperture, 600mm fl refractor myself right now. Diffraction would contribute slightly more to spot size with a 100mm aperture, however the only time that would matter is on nights when you have very good seeing.

 

Note that if you don't generally have good seeing to start with, and good seeing is very rare, then you might not benefit from the smaller pixel size. In that case, I would recommend the ASI1600 instead. I would figure out what your seeing is on average (and ironically, the larger your image scale is (the smaller the "/px), the easier it is to accurately measure your seeing...if you can borrow an ASI178 or QHY178 from a friend, which also has the same size pixels, and use it on your longest FL scope, that would probably be the best way to measure), as well as determine how often you have better than average seeing, and determine how often your seeing delivers stars around 2" or smaller. If you often have seeing that allows 2" or smaller stars, then the IMX183 will work great. If you usually have seeing closer to or greater than 3", then the ASI1600 would be better.

 

In my case, I seem to be in an area where we are hit and miss for the jetstream. I have nights like tonight, where we are mostly jetstream free, and seeing is good or great. I have other nights (like the ones coming over the next few days, according to forecast) where seeing gets up to around 2.8" or so, sometimes even worse, and I lose most of the benefit of the ASI183MM's smaller pixels. I seem to have nights of better seeing slightly more often than nights of poor seeing, so the smaller pixels are working well enough for me right now.


  • h2ologg, Pug and NorthField like this

#90 calypsob

calypsob

    Aurora

  • *****
  • Posts: 4683
  • Joined: 20 Apr 2013

Posted 06 December 2017 - 01:54 PM

You are welcome. I actually have more to come. I've been trying to acquire some more data, however my mount is acting up again, so I've lost some nights. Tonight is looking ok (according to Astrospheric, I'm in a gap between jetstreams, and seeing is pretty good), so hopefully I'll be able to finish at least one image, maybe two. These will be images with 10 minute subs.

 

I am also putting together some demonstrations of quantization error, what kinds of signals it affects, and what swamping the read noise (and therefor the quantization error) actually looks like, and why it doesn't take much to average out the quantization even with a 12 bit camera.

Wow astrospheric is amazing!



#91 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 07 December 2017 - 12:19 AM

 

You are welcome. I actually have more to come. I've been trying to acquire some more data, however my mount is acting up again, so I've lost some nights. Tonight is looking ok (according to Astrospheric, I'm in a gap between jetstreams, and seeing is pretty good), so hopefully I'll be able to finish at least one image, maybe two. These will be images with 10 minute subs.

 

I am also putting together some demonstrations of quantization error, what kinds of signals it affects, and what swamping the read noise (and therefor the quantization error) actually looks like, and why it doesn't take much to average out the quantization even with a 12 bit camera.

Wow astrospheric is amazing!

 

Yeah!! I am loving it. The jetstream view is really nice, and they also have the aerosol optical depth view as well. Very useful. I have been correlating seeing to jetstream, and I'm seeing some interesting stuff. Being close to or right on the edge of the jetstream seems to be the worst. You get both scintillation and jumping, and the jumping around of the star makes FWHMs so much worse. When I'm in the jetstream but not in the worst of it (blue to purple, not hot pink, in the Astrospheric map), scintillation is higher, but the stars tend to jump around less (barring local phenomena anyway), and while I don't get as good an FWHM in the jetstream as out, it's better than being around the edge of it. Not sure yet what being in the worst of the jetstream is like...haven't had a clear night with that being the case yet. Dark blue/purple on astropsheric is around 180km/h or so, whereas bright magenta is 300km/h...so, large difference.



#92 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 07 December 2017 - 12:30 AM

Quick FYI, I asked ZWO about the FPGA-based glow reduction, if they had done anything like that. It sounds like they have already been doing some of that with their cameras, but in the last response it sounds like they were able to either eliminate or greatly reduce the three corner glows. Sounds like it is a firmware thing, so it might be fixable just with firmware update. I don't yet know if that is something the user could do, or if the camera would have to be sent in. In any case, sounds like there may be some improvements in amp glow coming for the ZWO cameras. Hopefully more soon...

Quick update. I just had one of the ZWO engineers TeamView into my laptop and update the FPGA firmware on my ASI183. I have an earlier model, so they had to tweak the firmware a bit, seems they have made a few hardware changes since I received my copy of the camera. Anyway, the FPGA firmware has been updated. I'm waiting on an updated driver to go along with it, and then I should be able to test and see what happens with the amp glows.

 

Having them log in and do the firmware update is a pretty seamless process. It took about 15 minutes, most of that was them needing to adjust the firmware to my older version of the hardware. I think in most cases it probably wouldn't take longer than 5 minutes. Pretty interesting, if that's all it takes to update the FPGA. Means that if they manage to update any of their other Sony based cameras to remove some of the amp glows, existing cameras should be able to be updated for those who want the improvements...no need to ship the camera back or anything like that.

 

I'll post more once I get the updated driver and can do some testing.


  • h2ologg, GaPrunella and rafiosso like this

#93 Anemone

Anemone

    Sputnik

  • -----
  • Posts: 40
  • Joined: 16 Jul 2010

Posted 07 December 2017 - 05:38 AM

Hi Jon,

What can be said about the IMX183 QE? according to the ptgrey website the mono sensor has a 84% QE at 500nm, which is similar to the QE of the old KAF-1603ME and the KAF-3200 used in scientific research albeit on different wavelengths... How does this compare to the ASI1600 with its 60% QE in reality? and how do new low noise sensors compare with the older high QE sensors  such as the KAF-1603ME and others(Noise, QE and realistically on the ground). although back illuminated, I still see some old sensors having a much higher QE in the infrared wavelengths. does low noise make up for the lack of QE at some wavelengths? 

I'm prospecting as to whether the IMX183 sensor is suitable for light curve photometry, spectroscopy and other scientific applications versus other sensors on the market now.


  • Pug likes this

#94 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 07 December 2017 - 12:17 PM

Hi Jon,

What can be said about the IMX183 QE? according to the ptgrey website the mono sensor has a 84% QE at 500nm, which is similar to the QE of the old KAF-1603ME and the KAF-3200 used in scientific research albeit on different wavelengths... How does this compare to the ASI1600 with its 60% QE in reality? and how do new low noise sensors compare with the older high QE sensors  such as the KAF-1603ME and others(Noise, QE and realistically on the ground). although back illuminated, I still see some old sensors having a much higher QE in the infrared wavelengths. does low noise make up for the lack of QE at some wavelengths? 

I'm prospecting as to whether the IMX183 sensor is suitable for light curve photometry, spectroscopy and other scientific applications versus other sensors on the market now.

I haven't done head-to-head comparisons to evaluate Q.E. of the two ASI cameras. I also have never personally used some of the better known high Q.E. KAF cameras out there, so I cannot speak directly to them.

 

If there are some basic tests you would like me to do to evaluate this stuff for you, just let me know. I would like to know the suitability of these cameras for such scientific stuff as well. I can pick up a filter for spectroscopy if I need to (always wanted to get one.) 


  • Anemone and Pug like this

#95 Anemone

Anemone

    Sputnik

  • -----
  • Posts: 40
  • Joined: 16 Jul 2010

Posted 07 December 2017 - 12:58 PM

 

Hi Jon,

What can be said about the IMX183 QE? according to the ptgrey website the mono sensor has a 84% QE at 500nm, which is similar to the QE of the old KAF-1603ME and the KAF-3200 used in scientific research albeit on different wavelengths... How does this compare to the ASI1600 with its 60% QE in reality? and how do new low noise sensors compare with the older high QE sensors  such as the KAF-1603ME and others(Noise, QE and realistically on the ground). although back illuminated, I still see some old sensors having a much higher QE in the infrared wavelengths. does low noise make up for the lack of QE at some wavelengths? 

I'm prospecting as to whether the IMX183 sensor is suitable for light curve photometry, spectroscopy and other scientific applications versus other sensors on the market now.

I haven't done head-to-head comparisons to evaluate Q.E. of the two ASI cameras. I also have never personally used some of the better known high Q.E. KAF cameras out there, so I cannot speak directly to them.

 

If there are some basic tests you would like me to do to evaluate this stuff for you, just let me know. I would like to know the suitability of these cameras for such scientific stuff as well. I can pick up a filter for spectroscopy if I need to (always wanted to get one.) 

 

The first thing that caught my attention regarding the IMX183 mono is its very high QE and that its BSI to be honest, a feat found in very expensive CCDs in the past years used for scientific research that not everyone could afford, and looking at its price now, it's becoming something affordable and available to many. I already know the sensor in the ASI1600 is linear and is very well suited for spectroscopy and photometry despite the 60% QE (I read a review on it somewhere), but would like to know how it stacks up against a higher QE sensor of nearly similar size in that regards. So Yes Jon if I may ask and it's not too much trouble, I would like to see how this new high QE sensor translates practically in some tests  :-)


  • Pug likes this

#96 andysea

andysea

    Soyuz

  • *****
  • Posts: 3511
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 07 December 2017 - 01:02 PM

I have the QSI532 class1 sensor, I can do whatever test people would like as long as I have clear directions.
  • Pug likes this

#97 dvalid

dvalid

    Ranger 4

  • -----
  • Posts: 322
  • Joined: 02 Apr 2014
  • Loc: Georgia

Posted 07 December 2017 - 01:17 PM

Jon, I know, this question has been asked many times, opinions are divided though. Your vision would be very valuable to me. 

 

Does the pixel size affect total exposure time? Does the sensor with smaller pixels need longer exposure to collect the same amount of signal (presume all other properties are equal)? 

 

It seems, the IMX183 is a very sensitive sensor and its tiny pixels are great for resolution, but how about exposure times? This question emerged once again to me after seeing a single 300 sec frame of ZWO294 camera. 

 

Thanks in advance.

 

David



#98 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 07 December 2017 - 01:19 PM

 

 

Hi Jon,

What can be said about the IMX183 QE? according to the ptgrey website the mono sensor has a 84% QE at 500nm, which is similar to the QE of the old KAF-1603ME and the KAF-3200 used in scientific research albeit on different wavelengths... How does this compare to the ASI1600 with its 60% QE in reality? and how do new low noise sensors compare with the older high QE sensors  such as the KAF-1603ME and others(Noise, QE and realistically on the ground). although back illuminated, I still see some old sensors having a much higher QE in the infrared wavelengths. does low noise make up for the lack of QE at some wavelengths? 

I'm prospecting as to whether the IMX183 sensor is suitable for light curve photometry, spectroscopy and other scientific applications versus other sensors on the market now.

I haven't done head-to-head comparisons to evaluate Q.E. of the two ASI cameras. I also have never personally used some of the better known high Q.E. KAF cameras out there, so I cannot speak directly to them.

 

If there are some basic tests you would like me to do to evaluate this stuff for you, just let me know. I would like to know the suitability of these cameras for such scientific stuff as well. I can pick up a filter for spectroscopy if I need to (always wanted to get one.) 

 

The first thing that caught my attention regarding the IMX183 mono is its very high QE and that its BSI to be honest, a feat found in very expensive CCDs in the past years used for scientific research that not everyone could afford, and looking at its price now, it's becoming something affordable and available to many. I already know the sensor in the ASI1600 is linear and is very well suited for spectroscopy and photometry despite the 60% QE (I read a review on it somewhere), but would like to know how it stacks up against a higher QE sensor of nearly similar size in that regards. So Yes Jon if I may ask and it's not too much trouble, I would like to see how this new high QE sensor translates practically in some tests  :-)

 

Sure! Sounds like Andy can do some testing on the CCD side. Just let us know what you need, procedures for how to do the test would be ideal. 

 

I have not been able to determine exactly how the ASI183 compares to the ASI1600 yet. I've been keeping the ASI183 on the scope in it's given orientation so I wouldn't have to worry about field rotation problems or anything like that. At some point here, I'll be ready to take the ASI183 off, and put the ASI1600 back on for some comparison testing. 

 

That said, I feel the ASI1600 might be slightly more efficient? At least at a high gain for narrow band on the ASI1600, the read noise seems to be the largest differentiator...I get about 1.3e- RMS on the ASI1600, and at Gain 53 on the ASI183 it's 2.4e-. The difference there is actually quite large, and may somewhat swamp the difference in Q.E. But it also is not an apples to apples comparison. Additionally, for photometry, the star signals are bound to be very strong, so the read noise difference probably won't matter anyway. 

 

Anyway, just let us know how you want us to test. 


  • Pug likes this

#99 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23576
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 07 December 2017 - 01:25 PM

Jon, I know, this question has been asked many times, opinions are divided though. Your vision would be very valuable to me. 

 

Does the pixel size affect total exposure time? Does the sensor with smaller pixels need longer exposure to collect the same amount of signal (presume all other properties are equal)? 

 

It seems, the IMX183 is a very sensitive sensor and its tiny pixels are great for resolution, but how about exposure times? This question emerged once again to me after seeing a single 300 sec frame of ZWO294 camera. 

 

Thanks in advance.

 

David

On a non-normalized basis, yes. Absolutely, the pixel size affects exposure time. If you are going for resolution, then it will be a factor. This is actually a part of the reason why I am using 10 minute subs, vs. the 3 minute subs I used with the ASI1600. The smaller pixel size collects fewer photons per unit time, so to get the same pixel SNR you need longer subs. The other part of the reason is the higher read noise of the ASI183. It's 2.4e- vs. 1.3e- (for my narrow band work), so that, too, required me to increase exposure times.

 

Note that on a normalized basis, the differences in Q.E. are not as large (or rather, they remain unchanged as it's an instantaneous factor). They mostly boil down to the read noise difference. Also note that Q.E. affects exposure time, but the Q.E. difference isn't even going to account for a single stop in this case...84% vs. 60% (~1.4x), whereas the strait up read noise difference is a stop...2.4e- vs. 1.3e- (~1.9x), and the area-normalized read noise difference is over a stop...3.8e- vs. 1.3e- (~3x). The read noise, on a non-normalized and normalized basis, is the more significant factor.

 

Factoring in the 1.4x BENEFIT to the ASI183 due to Q.E. against the 3x DETRACTOR from the ASI183 due to read noise, plus accounting for glow and dark current, I came up with 7 minutes as the necessary exposures to get the same kind of SNR per sub as I was with the ASI1600 at 3 minutes.

 

I ended up shifting from a moderately high gain of 150-200, down to gain 53, in order to balance out my dynamic range as well. At gain 200, the ASI183 had less DR and more read noise (by a small amount, ~1.5e- vs. 1.3e-) than the ASI1600. While at a higher gain, I needed maybe 5 minute subs, I was clipping stars a bit too much. Moving to gain 53, I used 10 minute subs, but did not clip stars as much. It's always a balancing act. 

 

I shared a single 10 minute Ha sub earlier in the thread, in a comparison of calibrated vs. non-calibrated to show amp glow correction. Note that even though it is narrow band, I have extremely high LP, plus moonlight, plus haze...so it isn't the best of subs (few of my subs are any better these days....it's amazing how bad the LP has gotten around here, even 3nm filters suffer too much background contamination IMO). I did see the ASI294 single exposure, and I am pretty sure that guy is at a fairly dark site, deep yellow zone, maybe green zone. So take that into consideration. I have many 5, 7 and 10 minute single sub images from my green zone dark site that look just as good. wink.gif The power of a dark site is superior to just about any camera technology, by a long shot. 


Edited by Jon Rista, 07 December 2017 - 01:40 PM.

  • poobie, dvalid and Pug like this

#100 akulapanam

akulapanam

    Mercury-Atlas

  • *****
  • Posts: 2537
  • Joined: 26 Aug 2012

Posted 07 December 2017 - 03:22 PM

Jon, I know, this question has been asked many times, opinions are divided though. Your vision would be very valuable to me.

Does the pixel size affect total exposure time? Does the sensor with smaller pixels need longer exposure to collect the same amount of signal (presume all other properties are equal)?

It seems, the IMX183 is a very sensitive sensor and its tiny pixels are great for resolution, but how about exposure times? This question emerged once again to me after seeing a single 300 sec frame of ZWO294 camera.

Thanks in advance.

David

At the same arc sec resolution and aperture no. Note to achieve this you need a very fast scope. For many refractors the 183 has more resolution than is usable for the aperture of the scope.

Etendue calculation for speed of imaging looks like aperture ^2 * arc sec resolution ^2 * qe

Edited by akulapanam, 07 December 2017 - 03:24 PM.

  • mikefulb and dvalid like this


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