12 replies to this topic

[mikewayne3]

I just ordered a asi294 this will be my first cooled camera.

I've been using a DSLR so this will be different.

Any suggestions on gain and offset would be greatly appreciated.

Mike

[sctbrd]

Offset: https://daleghent.co...g-camera-offset

Should be at least at the setting that brings the histogram off the left side. Higher gains will need a higher offset so you should check the offset per the link for each gain you plan using.

 

Some people use 30 all the time, you can try that as a starting point.

 

Gain is based on how much you want to see vs how much noise you are willing to allow. The 294 has pretty low noise above 100 gain. My recommendation is to start at 300 or 350, get used to it, then lower it, play around with it, afterwards. Someone else can give a more experienced recommendation, but for me it was more satisfying being able to see things faster/easier with the higher gain when I started out.

 

"They" say to stay away from gains 90-100, some say anything below 120 because of the way this sensor works.

 

There seems to be a weird anomaly with exposures around 1 second with the 294, so be aware of that- anything .9 sec to 1.2 sec.

Edited by sctbrd, 24 May 2022 - 01:24 PM.

[mikewayne3]

Thanks for the reply.

I think the only time I'll be doing 1 sec will be to focus.

Or perhaps next winter wile getting the trapezium.

BTW the scope I'll be using is an AT72ED

[barbarosa]

Generally I set gain to 120 or 121 (the product sheet says HCG (high conversion gain) mode kicks in at 120 or above), Occasionally I set it at 300, but my darks are I think now all made at 120. The graphs on the product page clearly show the effect on noise and dynamic range. S

 

I know a couple of guys who used to always set the gain high 300 or 350, but have gradually shifted to a a longer exposure at 120 or 121.

 

For some targets and some conditions the best exposure might be 8 seconds, but for most DSOs I find 60s or more is good.

 

It could be worth your while to pay for a copy of SharpCap Pro just to get the Smart Histogram tool. It has a stored model for the 294 or you can run a sensor analysis on your camera, but the results are usually almost identical. The histogram itself gives  you some indication on the goodness of your gain and exposure settings. The Smart Histogram also has a "Brain" tool that uses the sensor analysis and some sky brightness measurements to suggest gain, offset and exposure settings for unity gain or max dynamic range and has a user selectable option for allowable noise level. Not the be all/end all tool but a very good place to start.

 

Alternatively try using the ASI software suite. It defaults to a limited number of gain and exposure settings. The, and the results can be good and you get some information about settings that work.

Edited by barbarosa, 24 May 2022 - 02:32 PM.

[mikewayne3]

Thanks Barbarosa 

As a matter of fact I already have sharpcap pro

Up till now I've been using it for polar alignment with my ASI 120 and I think its well worth it.

Mike

[DirtyRod]

Take a look at the graphs for the 294. Setting the gain at 300 or 350 significantly lowers the dynamic range and full well depth which could lead to blown out stars. I'd keep it closer to 120 and utilize the histogram for deep sky imaging. For a planetary camera I sometimes go that high but then it's all extremely short exposures under 1 second. 

 

For offset, I generally use 20-30 for my cameras. Just enough boost to keep from clipping the blacks on the left side of the histogram. 

[Fegato]

I have an ASI294mc pro. I use 120 gain (near enough unity). This is where HCG kicks in ( or it might be 117?). With HCG you get low read noise and DR at 0 gain levels, so this is a sweet spot.
I have offset at only 8, as Craig Stark’s method suggested this. Go a little higher perhaps.

[Fegato]

Regarding short exposures - bias levels are unpredictable, so shoot flats 2s or more to be safe and use dark flats. It’s not just around 1s - it’s all the way down to zero.

[unimatrix0]

Thanks Barbarosa 

As a matter of fact I already have sharpcap pro

Up till now I've been using it for polar alignment with my ASI 120 and I think its well worth it.

Mike

You could also live stack with Sharpcap,  just set a specific gain and exposure time and click live stack. It's fun , I used it for the first 3 months of my journey into astrophoto. 

Also, do a sensor analysis on your new camera with Sharpcap. 

You could also start off by Sharpcap, before you move into N.I.N.A or APT or Asiair, and make a sky measurement to find the optimal gain and offset and exposure for your sky quality. Sharpcap will tell you exactly what those values should be . 

[mikewayne3]

Thanks for all the suggestions I'm really looking forward to using it

Mike

[AstroVagabond]

I leave them at the default for my ASI294MM Pro and for that matter at the default for my ASI533MC Pro.

 

I'm a second year beginner. I place my effort on polar alignment, guiding, focus, and achieving an optimal exposure length for the skies I image under which are Bortle 7-8 and Bortle 3-4.

 

I expect if I tweak gain and offset I could achieve additional benefit but it's just not something I care to place any energy into at this time.

 

I expect we all have our personal preferences which is the way t should be in my view.

[mikewayne3]

I leave them at the default for my ASI294MM Pro and for that matter at the default for my ASI533MC Pro.

 

I'm a second year beginner. I place my effort on polar alignment, guiding, focus, and achieving an optimal exposure length for the skies I image under which are Bortle 7-8 and Bortle 3-4.

 

I expect if I tweak gain and offset I could achieve additional benefit but it's just not something I care to place any energy into at this time.

 

I expect we all have our personal preferences which is the way t should be in my view.

Thank you very much

Mike

[CCDMike]

I use a offset of 7 (checked with blackpoint in the histogramm on bias images) and a gain of 120 (300 if you use L-eNhanced etc.) with good results.

 

Best

Mike