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ASI 1600mm Pro narrow band exposure settings

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#1 SandyC8

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Posted 14 October 2019 - 08:48 AM

I have just started giving narrowband a try. My first target was the W. Veil with Ha and the next night, Oiii. The first set of exposures I use unity gain, -10C and 240 sec. subs x 50. The next night with Oiii, I noticed that it took a little more exposure to focus then with the first set of subs, I noticed that even stretched the veil was just barely visible. So, I increased the exposure time to get a decent signal. In retrospect, I think that was a mistake. I use APP and in the past trying to process an image with using subs with different exposure times hasn't worked out well. When using different narrow band filters, how do you adjust the exposure between the different filters. I would guess by changing the gain and using the histogram???

 

Thanks



#2 Jcwillis4

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Posted 14 October 2019 - 09:05 AM

Normally, my Oiii data is more exposed than the Ha for the same amount of time, if the filters are the same bandpass width (i.e. 7nm).  Was this over just the last few days?  If so, it’s likely the moon causing the biggest issues.  Oiii is in the blue spectrum, and takes a bigger hit than Ha when the moon is near full.

 

Beyond that, I refer back to this thread a lot to check my minimum exposure times.  It’s very helpful.

 

https://www.cloudyni...d-maybe-qhy163/


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#3 richorn

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Posted 14 October 2019 - 09:31 AM

I have been using 200/50 (gain/offset) for all my backyard narrowband shots. I find Ha much stronger a signal than OIII. Most nights I’m limited to 5 minute subs, so I just take more OIII images. On the few occasions that everything really works then I take 10 minute subs for OIII. For my LRGB images, I’m limited by Bortle 6 to 30 second subs at 76/12.

I have been doing most of my integration in APP, and it doesn’t seem to care at all what the different exposures are. Just make sure you have matching darks and flats for the various gains/exposures/temps/filters.
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#4 SandyC8

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Posted 14 October 2019 - 10:24 AM

Thanks...for the reply....both help a lot. I think you are right....the moon has made a mess of things on my first attempt. 

 

Thanks again.....

 

Lynn



#5 Jcwillis4

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Posted 14 October 2019 - 07:50 PM

And I should clarify that the sky background is more exposed on my Oiii, but the signal vs that background is stronger in Ha for most nebula.  The Veil has so much Oiii in it though that you should see it pop decently.



#6 SandyC8

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Posted 14 October 2019 - 09:05 PM

Thanks John...your Astrobin is beautiful...I can only wish...maybe someday...:-) Nice looking family.....two of my grandchildren are in the park now....




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