1.81
#...
·
1
like
|
|---|
|
I'm curious about what gain settings you various 071 owners are using. Any thoughts on "Highest Dynamic Range" versus "Unity"? Looking forward to seeing the feedback on this subject. Stargazer66207 |
9.53
#...
·
1
like
|
|---|
|
Hi Ron. I have only used unity gain with my Zwo 071 mcpro. Seems to work well. I will vary the exposure time according to the darkness of the sky I'm imaging from. Mike |
6.94
#...
·
2
likes
|
|---|
| I just sold my ASI071 (and bought an ASI2600MC) but it was a very nice camera. At the end I allways had it at gain 200, offset 30, -15°C. Sticking to one gain setting made my master-dark library smaller. Not sure anymore why I chosed gain 200, maybe because it was commonly used by others. |
|
1.81
#... |
|---|
|
Goran thanks for your input! Stargazer66207 |
3.61
#...
·
2
likes
|
|---|
|
Hi! I use it at “unity” gain after I experimented with the other two gains. it seem to works best at unity with my set up. With the other two gains I had problems with banding and strange gradient ( I don’t remember which one did what). I only change the exposure length depending on the object and filter used. |
|
1.81
#... |
|---|
|
Francesco, Thanks for your input. Unity gain seems to work well. Stargazer66207 |
5.49
#...
·
3
likes
|
|---|
|
Hi Stargazer66207, Elmiko and Francesco, I've had an ASI-071 MC PRO for about a year now, and have been getting pretty good results so far. I've just started exploring the pros & cons of using different settings, and trying to understand the tradeoffs between gain, noise and dynamic range. I finally managed to work out that, although increasing gain reduces noise, it also reduces the Full Well Depth (FWD), meaning that the pixels saturate with a lower level of light, resulting in a correspondingly reduced dynamic range. I often wondered what was meant by 'Unity Gain' - I though that just meant Gain = 1 ... fair enough ?? But I couldn't understand why 'Unity Gain' was significantly different to Gain = 0, particularly when the gain can be adjusted 0-240. Then I wondered why the graph of GAIN(e-/ADU) in the camera's documentation had an arrow at Gain = 94, then suddenly realised that this is actually the 'Unity Gain' setting. That is, it's the gain where 1 electron = 1 ADU - which is completely obvious when you look at the vertical axis of the chart. So, 'Unity Gain' refers to the gain in e-/ADU - NOT in db. What is 1 ADU ? That's one Analog-to-digital unit, the minimum increment the camera's internal Analog to digital converter is capable of resolving. So, at a gain of 240 the Read Noise is minimised, but so is the FWD. At Gain = 240, the FWD = 3k, which is 1/16 of the maximum of 48k, so the dynamic range drops from about 14 stops to about 10 stops, the difference being -4, and 2^-4 = 1/16. AHA ! It all makes sense now. So - I will start shooting at gain settings higher than 'unity = 1' from now on  In terms of 'Offset', I'm still not certain what that actually is - can someone enlighten me - but in the ASI-071MC Pro it is fixed at a value of 65. The other thing is 'Dark Current' which is reduced by cooling the sensor. The ZWO documentation is not very clear on this point, and a lot of ZWO users have asked whether the 'Target' setting in the ASIAIR software is the absolute temperature, or the delta from ambient ... it is definitely the absolute temperature. To minimise noise, the best thing is to cool the sensor to at least -5°C, and if you go to -10°C you get a marginal improvement. The maximum cooling achievable is 35°C below ambient, so you can easily get to -10°C if the ambient is anything up to +25°C. Whether you select a low temperature will depend on your setup - for example, if you are battery-powered you might prefer to minimise power consumption, which increases exponentially with the temperature differential. The last thing to think of is the DEW Point, which can create issues with fogging. You can find the Dew Point at your location using websites such as Clear Outside. Basically, if you cool your sensor below the Dew Point, you may need to turn on your Dew Heater, which consumes about 4 Watts and is only ON or OFF - another thing to think about if you are battery powered. Anyway - I hope some of this info is helpful Gary (Sydney, Australia) |
|
9.53
#...
·
1
like
|
|---|
| Thanks for sharing this Gary! Lots of useful information! |
|
1.81
#...
·
2
likes
|
|---|
|
Gary wow, you certainly did your homework ! Thanks for posting this info. I now understand a lot more about these ZWO camera settings . Stargazer66207 |
|
3.61
#...
·
1
like
|
|---|
Gary JONES: Thank you Gary for posting and sharing this information! Very useful! I was actually watching this YouTube video about asi071 some days ago, also quite informative: https://m.youtube.com/watch?v=qFx1CU4aB0E |
|
5.49
#...
·
1
like
|
|---|
|
Hi Francesco, Many thanks for that nice compliment Thanks also for the YouTube link - that was very helpful, and correlated directly with my experience. I also had the frosting issue with a checkerboard pattern across my sensor, exactly as the video shows at 6:50. I overcame this by setting my equipment up an hour or two before I wanted to start imaging, switching on the cooler and the dew heater, and letting everything stabilise to ambient temperature. You can see the frosting and how it gradually disappears in the movie below. 20210822-201843 = NGC-6242 - Open Cluster.m4v In terms of camera settings, in my next session I'm planning to shoot at 0, 90 and 240 gain and see what difference it makes in terms of noise and dynamic range. Gary |
|
3.61
#...
·
1
like
|
|---|
|
Many thanks Gary! I fortunately did not have the problem of frosting on the sensor, but I always have the camera’s dewheater on and, like you do, I start the cooler as the first thing when I connect the camera (my scope is permanently outside during the winter). Cool video you did showing the frosting disappearing! Interesting to see the result of your test at 0.90 and 240! Cs! Francesco |
|
5.49
#...
·
2
likes
|
|---|
|
Hi again I did some imaging last night to test the effects of different gain, exposure and sensor settings had on image quality. The 4 images below are individual lights taken during the same session, using the settings you can see in the image headers :- Gain = 90, 240 Exposure = 60s, 120s Temp = -5°C, -20C. I've normalised each image using identical settings - so of course the images with a longer exposure look lighter than those with shorter exposures, and the images with lower gain look darker than those with higher gains. Quite honestly, I cannot see any significant difference at all in the level of noise in these images, but there is a difference in dynamic range - as you can see in the 120s exposure with gain = 240, the stars are saturated. I think I'll try these experiments again, perhaps with a few more combinations of different settings. If anyone would like to do something similar, it might be helpful to compare notes Gary =====  |
|
3.61
#... |
|---|
|
Hi Gary! Well done! Yes I agree, I neither can see any difference in noise in any of the images, so -5 or -20 seems to do little to noise level. Maybe just a little more “grainy” image the one at 60s at -20, but barely visible. Actually, all 4 images are very clear with almost no noise at all! Congratulations🙂! Unfortunately the weather here in southwestern of Sweden is mostly bad until mid January. Last autumn I could image only 3 times in 5 months. It will be therefore very difficult for me to conduct any experiment☹️ Thanks for sharing the information and data! Cs/Francesco |
|
5.49
#...
·
1
like
|
|---|
|
Thanks Francesco, Yes, it is very difficult to see any real difference. Actually the 60s image at -20°C should be the least noisy, because it was taken at the lowest temperature, and with the highest gain. It is a bit overexposed thought - so when I try this experiment again, I will try to get equivalent total exposures, so will try gain = 240 and exposure time of (say) 30s to see how that looks Best regards, Gary |
