Understanding Gain Setting Parameter in PHD2 for my ZWOASI120MM-S

[Martin Dowd]

Ive been successfully using the ZWOASI120MM-S camera to guide in an Orion 60mm Guide Scope  ( 240mm FL ) with my Newts ( up to 1000mm FL ) for a number of year now and have never really bothered or needed to review the gain setting in the PHD2 Camera tab of the Brain.( its always been left at the default of 95 )

I'd like to get an understanding of how the camera gain parameter works in PHD2 so I can optimize or improve SNR on guide stars especially using the Multistar guiding feature.I realise seeing conditions play a huge part but in SNR but I just need a further understanding of how I can maximise this cameras performance when guiding.

The ZWO performance graphs for this camera show a usable gain range of 0 to 100

Unity gain is 29 where read noise is quite low

Gain 0 is at highest dynamic range at full well of 14.5K but read noise is high

Appreciate any advice on how the PHD2 gain parameter works and a recommended or optimal gain setting for my ASI120MM-S guide camera

Thanks

Martin

[Brian Valente]

Hi Martin

you'll need to use the zwo ascom driver, the gain and related settings are available in the settings button in the equipment connection dialog box

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Brian Valente

portfolio brianvalentephotography.com 

[Brian Valente]

Hi Martin

My apologies, I hit the send button before writing the rest of my response ;)

What kind of SNR are you getting now for guidestar and how many stars are you getting for your multi-star?

I don't really see gain playing a big role in snr - the higher you gain the camera, there is more noise, so noise reduction might be another option to consider in your settings

You might increase your minimum star SNR to about 20 and see what how that impacts your guidestar selection

you can also try switching to auto exposure and in the Camera tab setting your camera settings to a min and max exposure maybe 1.5-4 secs for auto and the target SNR at 20. 

If your SNR is really that poor, you might consider binning the camera and see if that makes a difference for your conditions. 

 

On Tue, Apr 5, 2022 at 6:01 PM 'Martin Dowd' via Open PHD Guiding <open-phd...@googlegroups.com> wrote:

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[Martin Dowd]

Hi Brian,

Thanks for replying

Yes I'm aware how to find the Ascom camera settings ( I was told years ago that this camera should be set to 8 bit ? )

As I mentioned in my post Ive been guiding successfully for years but just wanted to know what the gain setting parameter means in the PHD2 Camera tab. (  mine has been left at 95 for years )

Is this setting a percentage of your Ascom gain setting or other ??

I image at two sites ( Main Home located in Suburbia Bortle 8 and at my Retirement getaway at a coastal rural retreat Bortle 3 )

Main Home my SNR ranges 20 to 30 and at my Retirement place SNR ranges from 20 to 50 ( Ive been using Multistar guiding for 6 months and in most cases PHD2 finds 9 starts out of 12 but Ive had nights where only 5 stars are found.

The post is really about finding out what this Gain parameter means in the Camera tab and secondly can I fine tune my ZWOASI120MM-S camera' performance in any way

Await your further advice

Thanks

Martin

[Brian Valente]

HI Martin

Gain is a zwo setting between 0-100. I"m not sure how ZWO measures it and what that number actually represents. Gain is just signal amplification, including the noise, so it's not really changing the ratio. If you want to better understand camera gain in general there are a lot of videos and posts available on that. 

For your SNR results, I would stick with what you are using. Those SNR numbers are good, and better SNR is not going to make much of any difference to your guiding. 

Most folks aren't fiddling with gain settings in their guide cameras. As you've said, the most important is SNR, and it sounds like you are doing quite well in that department

The camera works in either 8 or 16 bit quite well, although with multi-star guiding, i personally don't think 16 bit really buys you much more

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[Martin Dowd]

Hi Brain,

Thanks, yes Ive looked at Robin Glover's tutorials on Camera gain and so forth

I think Ive found something

Ive just read through the PHD2 manual and under Advanced settings in the Camera tab , it mentions that the Gain parameter you set in this box is actually a percentage between the minimum and maximum gain values supported by the camera

So in my case the ASI120MM-S camera according to the ZWO performance graphs has a usable Gain range from 0 to 100, so therefore if I set the Gain parameter in PHD2 to 95 , the cameras gain should be 95

Does that sound correct ?

[bw_msgboard]

Just check the manual, always a good place to start: :-)

 

https://openphdguiding.org/man/Advanced_settings.htm#Camera_Tab

 

Bruce

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From: 'Martin Dowd' via Open PHD Guiding [mailto:open-phd...@googlegroups.com]
Sent: Tuesday, April 05, 2022 7:28 PM
To: Open PHD Guiding
Subject: Re: [open-phd-guiding] Understanding Gain Setting Parameter in PHD2 for my ZWOASI120MM-S

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[Brian Valente]

>>>So in my case the ASI120MM-S camera according to the ZWO performance graphs has a usable Gain range from 0 to 100, so therefore if I set the Gain parameter in PHD2 to 95 , the cameras gain should be 95

Does that sound correct ?

the ASCOM configuration screen is the ZWO settings screen and is external to PHD, so there's nothing in there PHD is presenting to you. Whatever ZWO says it is, is what it is

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[Martin Dowd]

Ive just upgraded PHD2 from 2.6.9 dev4 to 2.6.11 , connected my camera , clicked on Brain , selected Camera tab and in the Camera properties , the Gain box has been removed whereas in 2.6.9 dev4 it was there.

Probably a good thing in my case

On another note, I currently use 2 rigs and eventually will be using 3 rigs ( existing 6" Newt with ASI120MM - S guide camera , existing 8" Newt with ASI120MM-S guide camera and  new CF 10" Newt with ASI290MM guide camera ) at 2 different locations

In the Equipment section I have named my 2 existing rigs in Equipment profile,  but in the Camera drop down there are only 2 ASI camera presets ( ASI Camera (1) Ascom and ASI (2) Ascom ) am I able to edit a camera type to have say ASI (3) Ascom for my newest rig  ?? Or am I stuck just using say ASI (2) Ascom again ?

Thanks

[Brian Valente]

Hi Martin

>>>In the Equipment section I have named my 2 existing rigs in Equipment profile,  but in the Camera drop down there are only 2 ASI camera presets ( ASI Camera (1) Ascom and ASI (2) Ascom ) am I able to edit a camera type to have say ASI (3) Ascom for my newest rig  ?? Or am I stuck just using say ASI (2) Ascom again ?

This is a limitation of the ASCOM driver supplied by ZWO, and it's currently at 2 total cameras. 

Also make sure to update your ZWO camera drivers and ascom drivers when you update PHD, they often are released in lockstep together

 

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[Martin Dowd]

Brian.

Thanks

Yes I have previously updated all the ZWO drivers but still only 2 cameras are shown in the PHD2 drop down

I updated Ascom last year to 6.5

The latest Ascom 6.6 notes don't show any ZWO updates

Thanks again

Martin

[Ken H]

Hi - the ZWO ASCOM drivers are on the ZWO website and they just updated the ASCOM one in March - v6.5.2 https://astronomy-imaging-camera.com/software-drivers. It helped me but I reverted to the native ZWO driver last night and had some good runs with it instead of through ASCOM.

Good luck

Ken

[Martin Dowd]

Thanks Ken