1767 replies to this topic

[jlandy]

did you apply the same stretch to the 1800 as you did the 900?

[tolgagumus]

did you apply the same stretch to the 1800 as you did the 900?

Raw fits files are in this folder. It's screen stretch on PI 

 

https://www.dropbox....fvJXfOk7sa?dl=0

[FirstC8]

I recall QHY had done some work on reducing amp glow on their cmos cameras, some were quite effective.

One of the best example is the IMX224 chip. ZWO came out with the ASI224mc camera first. It has severe amp glow issue.

QHY was quite late getting their 224 chip out but they had shown a significant amp glow reduction. It required hardware modification.

Edited by FirstC8, 29 April 2016 - 02:07 PM.

[Jon Rista]

Tolga, what is the gain setting you have been using on these frames?

[bigeastro]

I am still on board with the purchase.  Your satisfaction will depend on your expectations and your application of the camera in the right environment, equipment; user experience included.

 

I think it is a perfect value play for people who are looking to upgrade from DSLR into a cooled CMOS chip that should produce equivalent if not better images.  If the intent is to use it on a short focal length instrument with no binning, then the deal gets even better.  When you are planning to mainly take 5 min or shorter subs with some longer, then it gets even sweeter.  Finally, the specter of possibly overcoming the amp glow and using it for longer exposures, NB imaging, and other more high end applications, makes the camera even more attractive.

 

I kind of meet all the requirements above, so I think it will meet my expectations.  This is further enhanced by the fact that I do want further experience in cooled CMOS technology so as the technology develops I understand it better from real world experience.  

 

So I am not deterred by the amp glow.  I think that for the duration of my typical subs for the forseen future, I will be in the five to 10 minute range and I think I will be able to calibrate out the amp glow.  I also don't do any mosaics.  They just take too much time and I am a sky wanderer sometimes just taking images to see what is out there. 

 

The one thing that does bother me is the first report of less than 60% Quantum Efficiency.  However, this report is probably as reliable as the manufacturer's report if not slightly less so and hopefully we will get real measurements soon.  I still think it is a heck of a deal for a DSLR upgrade and more.  You know in regards to this last point.  Is not the QE associated with the temperature of the chip?  If so, then the report of the chip usage in another camera, which is not probably cooled would be unlikely matched in the cooled version?  Don't know.

Edited by bigeastro, 29 April 2016 - 02:17 PM.

[Jon Rista]

The report of 48% Q.E. was for a bayer CFA version of the sensor used in a mirrorless camera. Color sensors have lower Q.E. I don't think a color KAF-8300 would have any higher Q.E. than that. Actually, IIRC from the datasheet for the KAF-8300, the color sensor has 33%/40%/33% Q.E. for Red/Green/Blue channels. The KAF-8300 mono is 56% Q.E. So if the color version of the Olympus sensor has 48% Q.E. in the green channel, then I think that bodes well for the mono version having around 60%.

[bigeastro]

Thanks John,

I am still tickled pink, and can't wait for delivery, although I did comment to Sam to take his time with the beta testers and make it as good as it can be... within reason.  I am missing some real nice, end of the imaging season skies.  Sunset and the following two hours is clear, then the everglades burp and low clouds move by for about three hours, then it turns clear for the balance of the night.  It is pretty interesting to see the burping everglades in infrared drift over our location as the offshore breeze kicks up every night.  Days are 92 and nights are 70.

[FirstC8]

The setpoint cooling and precise calibration should address the amp glow issue.

The issue with the 224mc was at the time there was no setpoint cooling, or no cooled 224mc at all, that made the amp glow a real issue.

Having said that, one of the things I am looking forward to is a super cooled, low noise and high sensitivity chip that can obtain decent images without calibration, at least for bright DSOs, and some years later even for faint objects.

To reach that goal, amp glow (and other FPNs) need addressed out of the gate.

Edited by FirstC8, 29 April 2016 - 02:29 PM.

[tolgagumus]

Tolga, what is the gain setting you have been using on these frames?

Hi Jon,

There are 3 presets in the ascom driver.

Highest dynamic range gain 0, offset 10


This is the setting I use

[josh smith]

The setpoint cooling and precise calibration should address the amp glow issue.

The issue with the 224mc was at the time there was no setpoint cooling, or no cooled 224mc at all, that made the amp glow a real issue.

Having said that, one of the things I am looking forward to is a super cooled, low noise and high sensitivity chip that can obtain decent images without calibration, at least for bright DSOs, and some years later even for faint objects.

To reach that goal, amp glow (and other FPNs) need addressed out of the gate.

 

You'll still always want at least flats and bias frames.  But otherwise, you're describing a Sony sensor.

[bigeastro]

Yes,

 

It is a Sony sensor, which would be an easy decision, except maybe for current price points, and more importantly chip size.  We need a larger Sony chip and a lower price point.  They may answer our call with a CMOS and not a CCD.

[bigeastro]

Okay Tolga,

Quit messing around and get us some beautiful images.  We are all tired of various gray images with different density of bright white dots and differential brightness on the corners.  It has been helpful.  Thank you.  However, now it is time to go ooogh and ahhhhh that is beautiful.  Especially in filters that let only different wavelengths of light through to the chip.

 

We will all do the clear sky dance for you as we did for Ram when he purchased his 16200 and was beta/production testing it.  We were able to part even Seattle skies for his first light.  Hopefully we can do the same for New Jersey.

[Jon Rista]

Tolga, what is the gain setting you have been using on these frames?

Hi Jon,

There are 3 presets in the ascom driver.

Highest dynamic range gain 0, offset 10


This is the setting I use

Thanks. Any chance you could do a unity gain dark and a high gain dark? Curious how that may affect the amp glow... I imagine if it is amplified along with everything else...the amp glow could be very bad at high gain. That might be a problem.

[bigeastro]

That is a good point Jon.  I would expect the amp glow should be worse at high gain. 

[bigeastro]

I think I measured the amp glow at 5% across the sensor on the earlier images but they were not long exposure and I don't know what the gain setting was on them.  I think you recently measured them at 27% with the longer exposures.

[FiremanDan]

I think I'm going to have to sacrifice the FOV and go with a smaller CCD. I mainly want to do narrowband and I don't see that amp glow being conducive to the long exposures needed. Some of you seem really optimistic and you have more knowledge and experience. Maybe I'm missing something but that last dark had amp glow over most of the image.
I hope I'm just being overly pessimistic.

[josh smith]

I think we all knew or guessed there was going to be significant amp glow. The question has always been how bad will it be, will it calibrate fine, and how much noise will be present in the high glow regions ok faint targets after calibration. I don't think the level of glow is surprising or something to panic about yet. Likely it will be a complete non issue on most bright targets. The question I believe was asked or at least by me, was how will the increased noise in the glow regions look on very faint and extended nebula as well as how will it do on mosaics.

[Jon Rista]

I think I'm going to have to sacrifice the FOV and go with a smaller CCD. I mainly want to do narrowband and I don't see that amp glow being conducive to the long exposures needed. Some of you seem really optimistic and you have more knowledge and experience. Maybe I'm missing something but that last dark had amp glow over most of the image.
I hope I'm just being overly pessimistic.

I think you should do what feels right to you. If you don't think you could handle the amp glow, then I think getting a clean CCD is good. I am planning on getting a CCD myself in the long run...I just did not want to be left without a viable means of imaging from my back yard this summer and for however long it takes me to get the CCD. I'm happy to play guinea pig with the ASI1600 and narrow band imaging as well. The high amp glow will likely kill off any ideas for high speed imaging (1-10s) with LRGB as well...but, oh well. Should be fine for longer exposures.

[bigeastro]

Jon,

I think your clear sky chart is broken. It is white from left to white . You may want to check that.

[Jon Rista]

Jon,

I think your clear sky chart is broken. It is white from left to white . You may want to check that.

I ordered a piece of astrophotography equipment. .............   

Edited by Jon Rista, 29 April 2016 - 03:47 PM.

[FiremanDan]

 

I think I'm going to have to sacrifice the FOV and go with a smaller CCD. I mainly want to do narrowband and I don't see that amp glow being conducive to the long exposures needed. Some of you seem really optimistic and you have more knowledge and experience. Maybe I'm missing something but that last dark had amp glow over most of the image.
I hope I'm just being overly pessimistic.

I think you should do what feels right to you. If you don't think you could handle the amp glow, then I think getting a clean CCD is good. I am planning on getting a CCD myself in the long run...I just did not want to be left without a viable means of imaging from my back yard this summer and for however long it takes me to get the CCD. I'm happy to play guinea pig with the ASI1600 and narrow band imaging as well. The high amp glow will likely kill off any ideas for high speed imaging (1-10s) with LRGB as well...but, oh well. Should be fine for longer exposures.

 

 

Long exposure is what I am worried about. The 900 and 1800s dark frame is what has me nervous. The cooled 300 looks great. 

[keithlt]

I would like to try the osc version with a 3nm Ha filter in a short fast system.  whats that called Ha-rgb?

[Peter in Reno]

I am curious whether the glows in longer exposures will work with dark scaling? My original QSI 660 (Sony ICX-694) has similar looking glows but the difference in glows and non-glows area of the image was insignificant that I was able to easily use dark scaling from 30 minutes dark subs with 7 to 10 minutes lights without issues. Because many people had concerns with QSI glows, QSI eventually fixed it and not only the glows were gone in 30 minute darks but the read noise actually went down.

 

Usually AMP glows are located in one location and commonly at one corner of the image but this one looks very similar to my original QSI 660 camera so I am kind of doubting these are "AMP" glows but more like inherent in Sony sensors and may be easily calibrated out including dark scaling. For those that has done dark scaling with other cameras, please let us know if dark scaling is possible with this ASI1600 camera.

 

FYI: See QSI 660 glows discussion. Look at post #65 for before and after fix.

 

http://www.cloudynig...ony-chip-issue/

 

Thanks,

Peter

[Madratter]

My concern with the amp glow would be that it is almost certainly a noisy process. And it probably follows the standard rule of the SQRT(signal). The amp glow amount is the signal. So in areas with high amp glow, the amount of noise from that glow could become quite significant.

[josh smith]

I am curious whether the glows in longer exposures will work with dark scaling? My original QSI 660 (Sony ICX-694) has similar looking glows but the difference in glows and non-glows area of the image was insignificant that I was able to easily use dark scaling from 30 minutes dark subs with 7 to 10 minutes lights without issues. Because many people had concerns with QSI glows, QSI eventually fixed it and not only the glows were gone in 30 minute darks but the read noise actually went down.

Usually AMP glows are located in one location and commonly at one corner of the image but this one looks very similar to my original QSI 660 camera so I am kind of doubting these are "AMP" glows but more like inherent in Sony sensors and may be easily calibrated out including dark scaling. For those that has done dark scaling with other cameras, please let us know if dark scaling is possible with this ASI1600 camera.

FYI: See QSI 660 glows discussion. Look at post #65 for before and after fix.

http://www.cloudynig...ony-chip-issue/

Thanks,
Peter

While the appearance is similar, the magnitude is not. The glow on the Sony sensors was on the order 1% for long subs, not 30% on shorter subs. However your point is still valid and will be interesting to test. It be interesting to see dark calibrated dark in the meantime with typical sky value offset to see the noise that is remaining.

Edited by josh smith, 29 April 2016 - 04:19 PM.