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Exposure Duration

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#1 JTNX01DC

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Posted 10 May 2021 - 06:17 PM

Is there an advantage to use, for example, 5 exposures of 5 minutes each vs. 50 exposures of 30 seconds each for stacking? Any general advice for exposure times for EAA. Tks tons!



#2 jerahian

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Posted 10 May 2021 - 07:23 PM

Is there an advantage to use, for example, 5 exposures of 5 minutes each vs. 50 exposures of 30 seconds each for stacking? Any general advice for exposure times for EAA. Tks tons!

For EAA, I generally use short exposure lengths.  Depending on the target, my exposure lengths can be between 20-60s, but most often 30s, even with my SCT at f/10 (I do crank my gain to 300 or so on the SCT though).  For me, the benefit of EAA is to experience the gradual enhancement of the target signal through the noise, so I tend to prefer very short exposures and to watch the progression with each new sub.  I don't see any benefit using longer exposures.

 

-Ara


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#3 bips3453

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Posted 10 May 2021 - 09:46 PM

There are some good tips around adjusting the exposure length while doing live stacking with SharpCap. Here is a good one from Clouzot and Phil. 

 

https://www.cloudyni...cap/?p=10341236


Edited by bips3453, 10 May 2021 - 10:57 PM.

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#4 DSO_Viewer

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Posted 10 May 2021 - 10:47 PM

Is there an advantage to use, for example, 5 exposures of 5 minutes each vs. 50 exposures of 30 seconds each for stacking? Any general advice for exposure times for EAA. Tks tons!

I do not think that 5 minute exposures are truly EAA.

 

Steve



#5 roelb

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Posted 11 May 2021 - 04:12 AM

Don't known your equipment nor camera but for my scopes (see equipment list) I use mostly:

Lodestar X2 Mono: 20 ... 30 s

ASI290MM: 8 ... 10 s (gain 350)

ASI224MC: 15 ... 30 s (gain 350)

ASI533MC-Pro: 15 ... 45 s (gain 350)


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#6 Tiago Ferreira

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Posted 11 May 2021 - 06:10 AM

No way i would wait 5 minutes in EAA session to see an image (even if i could).

However for astrophotography i would probably wait even more if i could.

My favourite EAA exp: 4s


Edited by Tiago Ferreira, 11 May 2021 - 06:11 AM.


#7 DSO_Viewer

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Posted 11 May 2021 - 11:56 AM

Don't known your equipment nor camera but for my scopes (see equipment list) I use mostly:

Lodestar X2 Mono: 20 ... 30 s

ASI290MM: 8 ... 10 s (gain 350)

ASI224MC: 15 ... 30 s (gain 350)

ASI533MC-Pro: 15 ... 45 s (gain 350)

But I thought the Lodestar CCD cameras were way more sensitive than the CMOS cameras.

 

Steve



#8 alphatripleplus

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Posted 11 May 2021 - 01:20 PM

But I thought the Lodestar CCD cameras were way more sensitive than the CMOS cameras.

 

Steve

Higher read noise with a CCD camera ( approx 7e to 10e for the Lodestar X2) means you want longer single sub-exposures to avoid a noisy background (from read noise) compared to a low read noise CMOS camera. However, I've found that taking say 5min total of 30 sec subs with a Lodestar X2 will go about as deep as 5 min total of 10 sec subs with an ASI290MM. The 290MM has higher resolution (smaller pixels), but those two cameras are very close in sensitivity (faintest star visible).

 

The 1e read noise of the 290MM vs the 7e-10e read noise of the Lodestar means I can take shorter subs with the 290MM.


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