As we know all ASI cameras enable us small setting adjust through ASCOM camera driver such Gain and Offset. In this short article we will show you few test images how cameras setting affect on your captured image. For this test we used ASI1600MM-Cool and ASI071MC-Cool, two very popular ZWO DSO cameras.

ASI ASCOM camera driver interface is very simple. In this case we tested only predefined settings values for Gain and Offset. We have three options; highest dynamic range (G: 0 O: 10), unit gain (G: 139 O: 21) and lowest read noise (G: 300 O: 50). Which setting is the best for DSO imaging?

asi-cameras-ascom-settings

 

ASI1600 camera setting test

First test we made with 30-cm f4 telescope, ASI1600MM-Cool and L filter. We point telescope on very popular target M1, Crab Nebula in the constellation of Taurus. We captured three images with highest dynamic range, unit gain and lowest read noise settings. All three images were exposed 200-seconds at -20°C and bias, dark and flat not used. As we see lowest read noise settings give us very saturated images (stars and nebula). Reason for this is very low full well (bellow 1K) at this gain and offest values. Unit gain give us much better result. We have saturated only brighter/bigger stars. From our point of view the best result give us highest dynamic range. Gain and offest values for this preset give us full well 20K. We got not saturated stars, good background pattern and also very good SNR. If we exposure too long the sky glow will cover the read noise and there is no big difference with low read noise (LRN) and high read noise (HDR) camera settings.

ASI1600-M1_Gain-settings

Short exposures with HDR and LRN camera settings on same objects give us much more interesting results. Both images were exposed 10 x 10-seconds at -20°C and bias, dark and flat not used. On this case we see LRN image have less noise and higher SNR.

ASI1600-M1_HDR_LRN_10x10sec

Another test images were exposed 20 x 5-seconds at -20°C and bias, dark and flat not used. LRN image have less noise and higher SNR.

ASI1600-M1_HDR_LRN_20x5sec

For final test we compared 1 x 1-seconds exposure image at -20°C and bias, dark and flat not used. Result is very similar. LRN image have less noise and higher SNR.

ASI1600-M1_HDR_LRN_1x1sec

 

ASI071 camera setting test

We also made test with 135-mm f2.8 lens, ASI071MC-Cool and L filter (2″ IR-UV CUT ). We point telescope on very popular Virgo Cluster (cluster of galaxies). Also in this test we captured three images with highest dynamic range, unit gain and lowest read noise settings. All three images were exposed  at 200-seconds at -20°C and bias, dark and flat not used.  As we see lowest read noise settings give us very saturated stars, especially in R in G channel. At this values we have full well only 3K. Unit gain have similar issues, but yes with lees saturated stars. Also in this test we think the best result give us highest dynamic range with full well only 46K.

vigro-cluster-asi017-gain-settings

Short conclusion

Our visually conclusions are, highest HDR settings give better result at longer exposures. We have got not saturated stars, good SNR and also very good or same read noise pattern like images with LRN values. But if you preferred shorter exposures due your “lucky imaging technique” or mount track limit we prefer LRN settings.

49 Responses to Cooled ASI camera setting in ASCOM driver
  1. Avatar

    Hi,
    I have the non-cooled asi178mc. I am interested in DSOs and using a guided ES102.
    What is the best Gain and Offset and is their an ideal or recommended exposure length?

    I am trying Gain = 10, offset =30 and 120 sec exposure 24 RGB. would I be better with G=0, O=20 HDR that you recommend above?

    Also if I use higher gain I get bad Amp Glow.




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    • Avatar

      Yes, our default HDR setting was tested by our engineer. A little higher offset like 30 is OK.
      Amp glow can be calibrate by dark frames.




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  2. Avatar

    Thanks Sam, excellent products




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  3. Avatar

    Hi Sam I have had the ASI1600MM for a while and have now acquired an ASI1600MC. Plenty of information about on gain and offset settings for the MM camera but not a lot of mention for the MC model. What are the recommended settings for the colour camera, are they the same?
    Thanks for help




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  4. Avatar

    Hi ZWO,

    Firstly, many thanks for the excellent 1600MMC.

    Some folks have been using Gain values of up to 500 for some NB targets, with relatively shorter exposures.

    Your “benchmark” LRN gain setting is at 300, even though one can adjust up to 600 (I think).

    Could you comment please on whether there is any benefit at all in trying the very high gain settings re read noise?

    Thanks for any response.




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    • Avatar

      Hi Roger, For 1600mmc camera, gain>300 will be digital gain, read noise will be all the same between gain300-600.




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