ASI1600MM Pro: Gain and Offset Settings

[STEVE333]

I've recently purchased and started using a ZWO ASI1600MM Pro cooled monochrome camera. I had no idea of where to set the Gain (0-300) and Offset for this camera. Several nice users here on the forum provided some guidance.

Today I did a bit of Google searching and found some very useful information from Jon Rista who I've always found to be a reliable source. The thread is at the link below and Jon's post is the second post in the thread.

https://www.cloudynights.com/topic/5700 ... 00mm-cool/


The fifth post in the thread shows Jon's discussion in equation form. I put the equation into Mathcad and produced the following graph:

ASI1600MM Target Average by STEPHEN KING, on Flickr

The Horizontal axis is the ASI1600MM Gain setting.

The vertical axis is the Target Average Counts (16 bit) you want to achieve with your exposure. There is a curve for ASI1600MM Offsets of 10, 20 and 50. I measure Target Average Counts using the Pixel Aid tool in APT. You may have a different way to measure this.

EXAMPLE: For a Gain of 139, and an Offset of 50 you should aim for a Target Average Counts of about 1300. Adjust the Exposure length to achieve the desired counts. The desired counts will ensure that you have a long enough exposure to achieve optimum Signal-to-Noise while still maximizing your Dynamic Range.

I haven't had a chance to try this out yet, and, am looking forward to giving this a try tonight if the fog will stay away long enough. The exposures I've used so far have been much longer than this analysis suggests, and, many of the stars have been saturated. Hopefully this will improve the quality of the data I collect. Clouds come in tomorrow, so, tonight will be the only chance to try for a while.

Hope you find this useful.

Cheers,
Steve

[Baskevo]

Ooooh this is very interesting, Steve! I had no clue what the Pixel Aid tool was used for. Let me know how this goes!

So I'm assuming sky quality and brightness would all impact the image, affecting the correct target average counts?

Unfortunately, I am cursed with about 2 weeks of clouds and rain... So I am patiently awaiting your results. Thank you for sharing this!

[STEVE333]

Ooooh this is very interesting, Steve! I had no clue what the Pixel Aid tool was used for. Let me know how this goes!

So I'm assuming sky quality and brightness would all impact the image, affecting the correct target average counts?

Unfortunately, I am cursed with about 2 weeks of clouds and rain... So I am patiently awaiting your results. Thank you for sharing this!

I was very happy to find this information. Fortunately, making this graph was easy because of my background.

I didn't know what the Pixel Aid tool did either. I was very happy to learn how useful it can be.

Unfortunately, last night when I set up, my mount (and APT?) got "lost". After doing Polar Alignment I told the mount to go to a star for 1-star alignment. APT warned me that the star was below the horizon!! Not true, the star was high in the sky. No matter what I did I couldn't get the mount to behave and I ended up without a single image to try out the above analysis!!!! . This hobby can be so satisfying and then so frustrating. You can guess which one it was last night. Now I too have clouds in the future. Sigh ....

Cheers,
Steve

[TheButcher]

Excellent Work Steve!
I am gona test it.

Also to note from reading around that the higher the Offset the better compared from 0. And I read something about ZWO locking it at 50 and people messing with the offset were running into issues so that was their best practice to lock it IMO. I know others can't change it from 50 in some programs, but at least with Sequence Generator Pro it is adjustable still but I always make sure it is 50, now making it higher I have never experimented with it so not sure? But I think there is a good reason enough just to leave the offset at 50 and go from there. I could be wrong though since I am fairly new to the 1600mm-P.

[STEVE333]

Excellent Work Steve!
I am gona test it.

Also to note from reading around that the higher the Offset the better compared from 0. And I read something about ZWO locking it at 50 and people messing with the offset were running into issues so that was their best practice to lock it IMO. I know others can't change it from 50 in some programs, but at least with Sequence Generator Pro it is adjustable still but I always make sure it is 50, now making it higher I have never experimented with it so not sure? But I think there is a good reason enough just to leave the offset at 50 and go from there. I could be wrong though since I am fairly new to the 1600mm-P.

Thanks for the feedback TB. I've been using Offset=50 also. It doesn't "eat up" very much of the Dynamic Range, so, I think I'll also leave it at 50. The above analysis means I'll definitely be shortening my exposures. I guess that's because of the fairly high LP where I live. My forecast showed two weeks of constant rain/showers/clouds. Grrrrrrrrr. I really want to test this. If you get any results maybe you can share them here?

Cheers,
Steve

[TheButcher]

Excellent Work Steve!
I am gona test it.

Also to note from reading around that the higher the Offset the better compared from 0. And I read something about ZWO locking it at 50 and people messing with the offset were running into issues so that was their best practice to lock it IMO. I know others can't change it from 50 in some programs, but at least with Sequence Generator Pro it is adjustable still but I always make sure it is 50, now making it higher I have never experimented with it so not sure? But I think there is a good reason enough just to leave the offset at 50 and go from there. I could be wrong though since I am fairly new to the 1600mm-P.

Thanks for the feedback TB. I've been using Offset=50 also. It doesn't "eat up" very much of the Dynamic Range, so, I think I'll also leave it at 50. The above analysis means I'll definitely be shortening my exposures. I guess that's because of the fairly high LP where I live. My forecast showed two weeks of constant rain/showers/clouds. Grrrrrrrrr. I really want to test this. If you get any results maybe you can share them here?

Cheers,
Steve

Hey Steve, I did go by that chart and kept the offset at 50 on all and set the gain to 150 again and kept the ADU around 1400-1500 for each RGB and L (Ha is a different story, I messed up on it and left it set at 150 and had to keep raising the exposure time because it was at 900 or so even at a 10 minute exposure.) Tomorrow night I am setting it to 300G for Ha until it reaches around 2800 or so.

As far as the RGB Red was 85 sec at 150 and 40 sec for G and B. I also did a Lum with 20 sec exposures at Gain 100. And got 1400 ADU. I used it or that Needle Galaxy image. Now the Lum I had to expieriment with because I sold my other LUM because it was meant for a doublet refractor with CA and was not working well with my RC. So I did not use any filter for it and let it capture UV & IR. I was impressed But I heard it is not recommended for refractors and to use the IR/UV cut with the 1600.

I also read somewhere that 1600 does best with more stacked shorter exposires then longer ones combined. At least in light polluted skies. It is different from traditional CCD's/DSLR's and such they were saying. At least that was what I learned from that read. So I am going to stick with that philosophy to try to get as many frames as I can vs medium to longer exposure like 2-4 min for RGB on lower gain. And use that chart above you made. Also was mentioned that the only real advantage of taking longer exposure is not having to deal with all of those frames. (Now Dark skies could be a lot different) this was more targeted towards a somewhat light polluted sky which most of us have. I am 5 miles away from where the white zone starts from Philly So I am the purple color between white and red.

[STEVE333]

Hey Steve, I did go by that chart and kept the offset at 50 on all and set the gain to 150 again and kept the ADU around 1400-1500 for each RGB and L (Ha is a different story, I messed up on it and left it set at 150 and had to keep raising the exposure time because it was at 900 or so even at a 10 minute exposure.) Tomorrow night I am setting it to 300G for Ha until it reaches around 2800 or so.

As far as the RGB Red was 85 sec at 150 and 40 sec for G and B. I also did a Lum with 20 sec exposures at Gain 100. And got 1400 ADU. I used it or that Needle Galaxy image. Now the Lum I had to expieriment with because I sold my other LUM because it was meant for a doublet refractor with CA and was not working well with my RC. So I did not use any filter for it and let it capture UV & IR. I was impressed But I heard it is not recommended for refractors and to use the IR/UV cut with the 1600.

I also read somewhere that 1600 does best with more stacked shorter exposires then longer ones combined. At least in light polluted skies. It is different from traditional CCD's/DSLR's and such they were saying. At least that was what I learned from that read. So I am going to stick with that philosophy to try to get as many frames as I can vs medium to longer exposure like 2-4 min for RGB on lower gain. And use that chart above you made. Also was mentioned that the only real advantage of taking longer exposure is not having to deal with all of those frames. (Now Dark skies could be a lot different) this was more targeted towards a somewhat light polluted sky which most of us have. I am 5 miles away from where the white zone starts from Philly So I am the purple color between white and red.

Hey Butcher - sorry to be so long in responding. A bit of internet problems on my main laptop (scary!!) and I was away for a few days.

Sounds like you have even worse LP problems than I do. Thanks for sharing your results so far. Finding the best settings and exposures for this camera is a lot more work than I had anticipated. Keeps the "gray matter" working.

I was able to get out one night last week and captured my first LRGB data. I've been used to capturing 8 min Light frames with my DSLR and Duo-Narrowband filter, so, when I saw how short the exposures would be if I followed the recommended mean ADU from the graph, I panicked and used 2 min exposures. That produced a mean ADU of about 3660 ADU which is well above the recommended 1300 ADU for my gain of 140 and offset of 50. I processed that data and posted an image a few days back, but, wasn't happy with the results.

Since that time I've been conducting an experiment on improving the Flats. Very surprising results, and, I'll be posting about that sometime soon after a bit more experimenting. I can say that I have tried several different sets of flat frames with mean ADU values or 25000, 15000, 10000, 7000, 5000 and 3000. So far it looks like the flats with mean ADU of 3000 are clearly the best! I never would have guessed that. Still more testing (really the testing is processing using the new flats) to verify how well these new flats work for all four filters. A lot of processing and bookkeeping, but, this is a good time for that.

I'll keep you posted.

Steve

[Baskevo]

THREE THOUSAND?! are you serious!? That is crazy! I wish I had seen this before I unscrewed my camera to try and save my data I can't wait to try this! That is crazy to me

[STEVE333]

THREE THOUSAND?! are you serious!? That is crazy! I wish I had seen this before I unscrewed my camera to try and save my data I can't wait to try this! That is crazy to me

I'm still in the experimental stage. The flats taken with mean ADU=3000 produced the best Master Flat for the data which itself had a mean ADU=3600. I don't yet know if the two numbers being nearly the same has any significance, or, is just a coincidence. I hope to know better once I extend the experiment to the Red and Green channels.

By the way, I needed to use 100 individual Flats with mean ADU=3000 to produce a MasterFlat with acceptable noise level.

More to follow.

Steve

[Baskevo]

Well please share your results when you are done testing! I am very interested in this... I never got the dust mote removed from my LRGB images, and now I have to scrap em :/

[STEVE333]

Well please share your results when you are done testing! I am very interested in this... I never got the dust mote removed from my LRGB images, and now I have to scrap em :/

Before you scrap them you might want to check out this approach that sometimes works.

http://www.iceinspace.com.au/forum/arch ... 66961.html

Steve

[Baskevo]

Well please share your results when you are done testing! I am very interested in this... I never got the dust mote removed from my LRGB images, and now I have to scrap em :/

Before you scrap them you might want to check out this approach that sometimes works.

http://www.iceinspace.com.au/forum/arch ... 66961.html

Steve

ooooh okay I will give it a shot!! I'm praying it will work!

[rv3211]

I joined the forum so i could answer this post. I've been waiting some software that calculates the minimum and optimum ADU for any astro cam.

I've been testing it extensively with the ZWO ASI1600MM-Pro.

Imagine my delight when comparing my results to those on Steve's chart and realising they match almost exactly.

I can confirm Steve's numbers are good. The ADUs here will swamp read noise and produce great results.

Cheers
Rick

[AstroBee]

Just curious if any of you folks have run the sensor analysis in SharpCapPro and compared its results?
Also, wondering if the results of the original v1 model of the 1600mm would be the same as the latest v3 (Pro) model? I am still rocking the original version that ZWO released many years ago.

[sdbodin]

Just curious if any of you folks have run the sensor analysis in SharpCapPro and compared its results?

I tried to run it, but could not make it work. Spent an entire afternoon on it, then gave up and resorted to my 'don't think' method, just set 200 gain, 50 offset and call it good.

Works for me,
Steve

[AstroBee]

Just curious if any of you folks have run the sensor analysis in SharpCapPro and compared its results?

I tried to run it, but could not make it work.

Strange. Anyway, here's my sensor analysis report via SharpCapPro.
https://drive.google.com/file/d/1ZASUOO ... sp=sharing

[Gordon]

I've run the Sharpcap sensor analysis report a couple different times just to check for 'consistency' and it seems to be pretty accurate. I've tried using it with both Sharpcap and NINA to get a 'recommended' exposure time, but the results weren't even close to what I expected, either way too long or way to short.

[STEVE333]

I've run the Sharpcap sensor analysis report a couple different times just to check for 'consistency' and it seems to be pretty accurate. I've tried using it with both Sharpcap and NINA to get a 'recommended' exposure time, but the results weren't even close to what I expected, either way too long or way to short.

Hi Gordon - Unfortunately I don't know how to use my analysis for a color camera. Otherwise I would run the analysis for your system. However, it sounds like the Sharpcap sensor analysis report is working for you.

Cheers,
Steve