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.

15 Responses to Cooled ASI camera setting in ASCOM driver
  1. I like the flexibility of Asi1600mm-c , It’s really game changer, I started using my own two week ago , usually I do unity gain with narrowband & It yeld good results at shorter exposures , I’m still learning & I will try LRN & HDR as i got clear sky

  2. Thanks for sharing this “official” article. It’s good to read ZWO opinions in this matter.

    Thans again. Best wishes,

    Aleix Roig
    PRADES, Tarragona (Catalunya-Spain)

  3. Hi, thanks for sharing this kind of official evidence.
    I am a user of a non-cooled asi178mc and I would like to know the correct values ​​for long exposures (HDR) and shorter exposures with the “LRN” image technique in order to take advantage of my configuration.

    Thank you

  4. Thank you for this write up. Could you please clarify if these images are linear or streched in any way?

    Thank you!

  5. would the same exposure settings apply to the asi 1600 color, for the 10,5 and 1 second exposures ???

    when using the astrolive software for mac, I only see the option to adjust gain, what offset is it using at gain 300 and is it adjustable ?

    thx for posting this….

  6. Thanks for this information, Sam.

  7. Hi Sam
    This ‘instruction’ article is highly informative and very valuable for folks like me just setting up my 1600MC. More like this please!!!

  8. Have just moved across to mono camera from DSLR, and purchased from FLO in the UK, the bundle 2 kit with 31mm filters for f4/f5 Newtonians.

    Obviously lots to learn, and I am currently setting up my Dark and Bias libraries.

    This is an excellent article, and really opens my eyes to Gain/exposure choices.

    Many thanks for this guide, and many thanks for changing my reality, with this excellent camera.


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