SGPro ASI1600 Settings

[blinky]

Hi,

 

Can somebody confirm the figures in the screenshot are correct for an ZWO ASI1600 Mono?  I want the gain set to 300 here as I want SGPro to use that gain for focus runs - I will set the gain/offset in each sequence, but why does the settings screen shown not have a section for Offset?

Edited July 30, 2019 by blinky

[han59]

I don't use SGP except for some testing, but any other gain then unity gain =139 will reduce the ASI1600 dynamic range and give virtual no improvement in noise values. For proper stacking, you have to use the same gain for darks, flats and bias images so I always stick to unity gain.  I can't help you with the offset setting. In my humble opinion these settings should be only adjustable in the ascom driver or not adjustable at all.

[spillage]

Yeah that looks the same as my settings.

[blinky]

Excellent, thanks folks

[symmetal]

With CMOS cameras, as hardware binning has no advantage over software binning apart from a quicker download time, which can be useful for autofocus, you could set the 2x2 binning gain at 300 (or whatever binning you use for autofocus) on the Control Panel and your 1x1 binning at the gain you normally use for imaging. Offset is not avaiable to be set on the 'Control Panel' as offset is not accessible to programs through Ascom and SGP used Ascom only for device communications.

On the Autofocus options panel select 2x2 (or whatever you wish) as the binning so it uses your gain 300 setting. The e-/ADU and read noise settings on the Control Panel are only used to determine the ideal exposure time listed in the Image Statistics panel so don't need to be set if you don't use this feature. 

As there were many requests for offset to be able to be changed, the SGP team reluctantly modified the program to allow the Zwo native camera driver to be used as an alternative to the Ascom driver. The setting for Zwo native driver offset was put in the Sequencer/Event/Settings panel where it's out of the way of the nornal Ascom settings.

As I imagine you normally only image at 1x1 binning for the 1600, I would leave the Control Panel 1x1 gain as not set, and set your most commonly used gain/offset in the Ascom driver itself. Only those events where you actually use a different gain would then have to have their gain/offset settings changed.

Personally, as it's easy to forget to set the right gain/offset settings, as they are not easily visible, along with having to have sets of darks for all of these different settings, just use one offset for all gain settings. Take a stack of short exposures 0.5secs or so at the highest gain you'll use and examine the histogram to see if it is black clipped. You'll need to use a higher offset than those 'recommended' by Zwo, as the Zwo offsets do black clip images. The slight loss of dymanic range by using too high an offset at a lower gain is not significant.

As han59 says, I also just use unity gain for all exposures as it makes everything so much easier, with only darks needed for different exposure times only.

Alan

[blinky]

Interesting, I was using a different ga8n/offset for narrowband than rob, you dont this is necessary? 

[symmetal]

Using higher gain (2x unity is often quoted) for narrowband may mathematically give you a slight S/N advantage I believe over unity gain so there's no harm in doing that. It's more a case of the extra hassle in having to keep track of what settings are being used for different filters that I use unity gain for everything.  I think it's worth just using one offset setting for all to gain settings you use to remove one variability, I use 56 to just avoid clipping blacks, vlaiv uses around 64 I think to be doubly safe. The only point of using offset is to keep the image data within the limits of the A/D converter so that it doesn't clip the black end of the image. The Zwo recommended offsets don't quite achieve this.

Alan

[spillage]

No sure why I did not notice the gain values before. With the 1600 I do not think you can bin the camera as binning can only be done afterwards in software.

[symmetal]

You can set binning in a CMOS camera but it is effectively just software binning applied after the sensor has been read so the only 'benefit' is a smaller file size and therefore quicker download. 

Alan