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Gain 0 on ASI

ZWO ASI294MC
14 replies•410 views
Fabio Acquarone avatar
Fabio Acquarone avatar
Hi to all,

 after years of work using the unity gain about the specific ASI Camera used, in my case ASI 294 MC G=120 i am wondering if in some cases using G=0 is a better choice.

Has anyone did some test or frequently using G=0 for faint objects ? 
Could it be an advantage in polluted skies ?

Thanks!
Nick Grundy avatar
Nick Grundy avatar
I stick to a default of 105 gain on most everything, except when shooting RGBstars, and then I dial it back to 0gain. 

also curious myself
GIANNI MELIS avatar
GIANNI MELIS avatar
[pre]What focal ratio do you use? the smaller the focal ratio, the greater the risk of saturating the stars with the gain… I have been using gain 0 for years because I mostly photograph at F2, certainly with gain 0 you would saturate the stars less… but it depends on the focal ratio… It may be necessary to take more shots to achieve the same integration gain[/pre]
Fabio Acquarone avatar
Fabio Acquarone avatar
GIANNI MELIS:
What focal ratio do you use? the smaller the focal ratio, the greater the risk of saturating the stars with the gain... I have been using gain 0 for years because I mostly photograph at F2, certainly with gain 0 you would saturate the stars less... but it depends on the focal ratio... It may be necessary to take more shots to achieve the same integration gain

Interesting ... yes you are right.  In my case i vary from F2.2 to F6.5 .... so i think 0 is worth to be tested.
andrea tasselli avatar
andrea tasselli avatar
Aperture matters, not just f/ratio. And expsoure length. I see no point in deviating from gain = 120 (for the ASI294MC).
Fabio Acquarone avatar
Fabio Acquarone avatar
andrea tasselli:
Aperture matters, not just f/ratio. And expsoure length. I see no point in deviating from gain = 120 (for the ASI294MC).

Ok Andrea...but in general ? If i talk about ASI 2600 ? ,,do you see that the difference is about camera characteristics ? What to look for ?
Rodrigo Roesch avatar
Rodrigo Roesch avatar
The 294MC does not like long exposure since it generates a lot of background artifacts that are difficult to get rid. So if using 0 will represent longer exposure time, I would stick to unity unless you are just imaging from a light polluted sky that does not let you go longer anyway
Fabio Acquarone avatar
Fabio Acquarone avatar
Rodrigo Roesch:
The 294MC does not like long exposure since it generates a lot of background artifacts that are difficult to get rid. So if using 0 will represent longer exposure time, I would stick to unity unless you are just imaging from a light polluted sky that does not let you go longer anyway

Thaks Rodrigo, i usually do 5 min exposures with ASI 294 MC...and i am happy with this...i was in genreal trying to undertand G=0 if a possible way, but i think i think to understand  that depends mainly on the camera feature rather than a general approach ?
andrea tasselli avatar
andrea tasselli avatar
Fabio Acquarone:
Ok Andrea...but in general ? If i talk about ASI 2600 ? ,,do you see that the difference is about camera characteristics ? What to look for ?


*Whatever gives you the highest dynamic ange with the lowest RON with an eye, all other things being equal to the FWC+. For the 2600 it would be at minimum gain, which is close to unity, if I recall right. So, yes, it depends on the sensor and circumstances.
Tony Gondola avatar
Tony Gondola avatar
You should always shoot the 294 sensor at a gain of 120. The reason for that is it greatly reduces the read noise while giving the same dynamic range that you get at gain 0. The read noise on this sensor is rather high so it's really a no brainer.
Well Written Concise
ScottF avatar
ScottF avatar
Rodrigo Roesch:
The 294MC does not like long exposure since it generates a lot of background artifacts that are difficult to get rid. So if using 0 will represent longer exposure time, I would stick to unity unless you are just imaging from a light polluted sky that does not let you go longer anyway

How long do you consider too long for that camera? Is ten minutes ok, or no?
Rodrigo Roesch avatar
Rodrigo Roesch avatar
Rodrigo Roesch:
The 294MC does not like long exposure since it generates a lot of background artifacts that are difficult to get rid. So if using 0 will represent longer exposure time, I would stick to unity unless you are just imaging from a light polluted sky that does not let you go longer anyway

How long do you consider too long for that camera? Is ten minutes ok, or no?

I would say no more than 5 min. I have gone longer and it becomes very difficult to calibrate due to blotchy background.
John Hawk avatar
John Hawk avatar
To get your best images with an ASI294C is to take Flats and Flat Darks longer than 3 seconds and go with a gain of 120. It's an issue that has been well documented on the internet and by ZWO as well. The longer Flats and Flat Darks make a world of difference when it comes to artifacts. Good Luck and Clear Skies!
Helpful
andrea tasselli avatar
andrea tasselli avatar
Never taken flats longer than 1s, with CMOS cameras including the 294MC.  Always calibrated well.
GIANNI MELIS avatar
GIANNI MELIS avatar
For my The flat is Ever necessary .. my times flat is in to the order on 4 to 9 seconds .. depending the filter used