Using an FSQ 106 with .6x reducer and the ASI 1600 I am shooting 120 sec RGB subs for the rosette. If I try to shoot 120 sec luminance subs, the frame is almost totally white--very bright gray. Obviously, 120 sec is way to long for luminance at my location. I tried 30 sec luminance subs and they look OK. But I am wondering if there is a benefit to using 30 sec lum subs when the RGB are 120 sec. Would more RGB be better?
the general question is, should luminance subs be the same duration as RGB subs to realize the full benefit of luminance in an image.
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My L’s are generally 1/2 of R, G, and B. The L bandwidth is roughly the sum of the 3.
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Jeff Ridder:
My L’s are generally 1/2 of R, G, and B. The L bandwidth is roughly the sum of the 3.
That's good to know....thanks
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Rodd -
This thread may be helpful:
https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/
It is natural that your L needs to be shorter than RGB, especially if you're shooting from a light polluted site. With your 0.6 reducer, you will quickly saturate the sensor.
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Rodd -
This thread may be helpful:
https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/
It is natural that your L needs to be shorter than RGB, especially if you're shooting from a light polluted site. With your 0.6 reducer, you will quickly saturate the sensor.
Ain't that the Truth!!!
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Rodd -
This thread may be helpful:
https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/
It is natural that your L needs to be shorter than RGB, especially if you're shooting from a light polluted site. With your 0.6 reducer, you will quickly saturate the sensor.
One must take the charts with a grain of salt I think, as they are a bit unrealistic. I think it is a good example of theory colliding with the real world. I tried going the really short sub route--using 2000 subs for an image is not for me. And if I take 6 sec subs, the count would be more like 10,000 subs. Taking 10 sec subs if problematic for many reasons. Not the least of which is framing. Also, the risk of missing poor subs due to clouds or wind is much higher. I simply will not visually inspect 10,000 subs. Totally relying on software is risky as well.
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One must take the charts with a grain of salt I think, as they are a bit unrealistic. I think it is a good example of theory colliding with the real world.
Those times are minimums... meaning, you don't gain anything from a SNR standpoint by going longer. But as the thread points out, there are many reasons for going longer, several of which you also pointed out. In your case, as long as your subs are above those minimums, and they very likely are, you lose nothing from an SNR standpoint.
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One must take the charts with a grain of salt I think, as they are a bit unrealistic. I think it is a good example of theory colliding with the real world.
Those times are minimums... meaning, you don't gain anything from a SNR standpoint by going longer. But as the thread points out, there are many reasons for going longer, several of which you also pointed out. In your case, as long as your subs are above those minimums, and they very likely are, you lose nothing from an SNR standpoint.
I don't think I believe the theory. When I take a 6 sec sub I see absolutely no signal and noise. When I take a 2 minute sub, I see a lot more signal, and similar noise. The signal goes WAY up with time--and I don't see the noise going way down--so how can the SNR be the same?
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Rodd Dryfoos:
Using an FSQ 106 with .6x reducer and the ASI 1600 I am shooting 120 sec RGB subs for the rosette. If I try to shoot 120 sec luminance subs, the frame is almost totally white--very bright gray. Obviously, 120 sec is way to long for luminance at my location. I tried 30 sec luminance subs and they look OK. But I am wondering if there is a benefit to using 30 sec lum subs when the RGB are 120 sec. Would more RGB be better?
the general question is, should luminance subs be the same duration as RGB subs to realize the full benefit of luminance in an image.
Rodd,
One key factor here is the sky brightness. I haven't tried the F3 reducer on 6200mm yet. But it's kinda scary. 
For F5, what I am using is L 120s and R/G/B 180s at f/5.0 with Gain0/Offset 50 (ASI6200mm).
Hope it helps.
-Min
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Min Xie:
Rodd Dryfoos:
Using an FSQ 106 with .6x reducer and the ASI 1600 I am shooting 120 sec RGB subs for the rosette. If I try to shoot 120 sec luminance subs, the frame is almost totally white--very bright gray. Obviously, 120 sec is way to long for luminance at my location. I tried 30 sec luminance subs and they look OK. But I am wondering if there is a benefit to using 30 sec lum subs when the RGB are 120 sec. Would more RGB be better?
the general question is, should luminance subs be the same duration as RGB subs to realize the full benefit of luminance in an image.
Rodd,
One key factor here is the sky brightness. I haven't tried the F3 reducer on 6200mm yet. But it's kinda scary.
For F5, what I am using is L 120s and R/G/B 180s at f/5.0 with Gain0/Offset 50 (ASI6200mm).
Hope it helps.
-Min
My sky brightness is scary! I'll try 60 sec. I know 30 works--I'll have to measure median values. If you have the .6x reducer--you have to try! With full frame you'll have a monumental FOV. You will get vignetting but it should calibrate out.
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I have the ASI1600MM Pro and use it under Bortle 4/5 skies. My standard settings are:
L: 60s @ 76 Gain (15 Offset)
RGB: 120s @ 76 Gain
SHO: 300s @ 139 Gain
Works for most.
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Jeff Ridder:
I have the ASI1600MM Pro and use it under Bortle 4/5 skies. My standard settings are:
L: 60s @ 76 Gain (15 Offset)
RGB: 120s @ 76 Gain
SHO: 300s @ 139 Gain
Works for most.
Thanks--that's what I use for RGB and SHO....I have a suspicion that 60 will be a bit much for Bortle 6, but I'll try it. I guess I could go 45 (But then I need new darks!)
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