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Recommend Camera settings (ZWO 1600 Pro) for Bodes Galaxy/Cigar Galaxy/ IFN

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#1 ehanes7612

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Posted 19 March 2019 - 11:23 PM

I will be taking a week long trip with my gear to an area just east of 29 palms , Ca in two weeks.There are no light domes in the direction of Bodes from this position.  It will be a new moonish time and the area is grey/black bortle zone 2. My equipment will be a Tak 85 (no reducer so F5.3) with astrodons LRGB and the ZWO 1600. I was thinking of a gain setting of 139 and imaging for 2 minutes for each sub...but if anyone else has other suggestions , I am all ears. I am hoping to capture the IFN in good detail also


Edited by ehanes7612, 19 March 2019 - 11:53 PM.


#2 44maurer

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Posted 20 March 2019 - 12:26 AM

Can’t help you with your question, but you will like the skies in that area. I spent 8 days last summer northeast of 29Palms. I could see the Milky Way from 1 horizon to the other.

When I was there, it was windy every evening, calm during the day. I’m not sure how the winds are at this time of the year, it you may want to check on that and possibly make arrangements for a wind breaker of some sort.

This site was fairly accurate when I was there. https://www.windy.co...054,8,m:eB2acVJ

#3 ehanes7612

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Posted 20 March 2019 - 12:29 AM

Can’t help you with your question, but you will like the skies in that area. I spent 8 days last summer northeast of 29Palms. I could see the Milky Way from 1 horizon to the other.

When I was there, it was windy every evening, calm during the day. I’m not sure how the winds are at this time of the year, it you may want to check on that and possibly make arrangements for a wind breaker of some sort.

This site was fairly accurate when I was there. https://www.windy.co...054,8,m:eB2acVJ

For sure, I have been at this spot twice before. I go in the spring. It's on the border of Cleghorn Lakes Wilderness Area So quiet and dark (windy though at times) ..the boom boom boom from the marine base is interesting too. I would really like to build a cabin down there one day. I want to get down there in the summer eventually though...prime viewing of the MW center


Edited by ehanes7612, 20 March 2019 - 12:43 AM.


#4 Stelios

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Posted 20 March 2019 - 12:54 AM

I think you should image longer for the color filters in order to "swamp" the read noise from a Bortle 2 area. I would do 120" Lum and 240" RGB. 



#5 ehanes7612

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Posted 21 March 2019 - 01:44 AM

I think you should image longer for the color filters in order to "swamp" the read noise from a Bortle 2 area. I would do 120" Lum and 240" RGB. 

thanks



#6 gundark

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Posted 24 March 2019 - 01:16 AM

You have a camera with very low read noise, so you needn’t expose for long to swamp it. When I am in the desert with my 4 inch f/7 refractor and a ASI1600MM-cool, I typically expose luminance for about 60 seconds and RGB for 120 seconds at a gain setting of 76. I adjust my exposure time according to how many stars I am clipping.

The conventional wisdom is that you should expose to a certain sky background level, which is true to a point. Conventional wisdom also says that you should expose even longer at a dark site because the sky glow is less. The problem with that is that star flux is constant regardless of light pollution, and if you expose longer just because you are under a darker sky, you are going to start blowing out stars and losing star color in your final image.

You have a faster scope than mine. You may find that a gain setting of 139 and two minutes plus on your exposures may blow out too many stars. Just experiment and go for whatever setting gives you a decent background sky level and does not clip more than a few stars.

#7 ehanes7612

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Posted 24 March 2019 - 05:53 PM

You have a camera with very low read noise, so you needn’t expose for long to swamp it. When I am in the desert with my 4 inch f/7 refractor and a ASI1600MM-cool, I typically expose luminance for about 60 seconds and RGB for 120 seconds at a gain setting of 76. I adjust my exposure time according to how many stars I am clipping.

The conventional wisdom is that you should expose to a certain sky background level, which is true to a point. Conventional wisdom also says that you should expose even longer at a dark site because the sky glow is less. The problem with that is that star flux is constant regardless of light pollution, and if you expose longer just because you are under a darker sky, you are going to start blowing out stars and losing star color in your final image.

You have a faster scope than mine. You may find that a gain setting of 139 and two minutes plus on your exposures may blow out too many stars. Just experiment and go for whatever setting gives you a decent background sky level and does not clip more than a few stars.

I know what clipping is when I process...but I don't know how to test if I am clipping in the field


Edited by ehanes7612, 24 March 2019 - 05:54 PM.


#8 gundark

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Posted 25 March 2019 - 09:31 AM

You didn’t mention what capture software you have, but if you are using Sequence Generator Pro, it has a couple of features that are useful for determining proper exposure.

First, if you mouse over any pixel (e.g. in the core of a bright star) SGP will tell you the brightness value of that pixel. If the pixels in your star cores are maxed out at about 65k ADU, then those stars have been clipped. You can also mouse over the background to see what your background level is in those areas.

Second, SGP has a image statistics box that provides useful information about your subframe, such as minimum, maximum, and median pixel values.

Using these features together, you can determine what your background sky value is, and how many stars you are clipping.

I’m sure other capture programs have similar features.

Hope this helps.

#9 ehanes7612

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Posted 25 March 2019 - 04:02 PM

yes, I use SGP...good to know .. learn more about SGP every week



#10 OcativeOrg

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Posted 26 March 2019 - 04:58 PM

I am going to image M81 tonight from Arlington VA.
I have a 4 inch f7 APO. I have been reading articles and attempting to figure out exposures.

I started at a gain of 75 on the ZWO 1600. That was giving me a mean and median over 1000 at 1 minute. I pulled back the gain to 40 and at 1 minute got the mean down to 600-700 max 65500 and min 256. From my 9 bortel zone (had a sky glow filter) I understood that my mean should be about 500. I dropped my exposures to 40 seconds. Then shot for about 2 hours.

Questions is it best I stay at 75 gain? And 10 offset? Should I have any offset with the ZWO 1600?
At 75 gain I might be shooting 30 second ? exposures.

How do I mouse over in SGP to see if I am blowing out the core?
I assume there is no way to do this live? But after the exposure.

I am heading out to set up in an hour, so any exposure advice wouldbbmost welcome. Thx

#11 Jon Rista

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Posted 26 March 2019 - 06:11 PM

What kind of light pollution do you have?

 

I am imaging these two myself right now. I am using an FSQ106, f/5, ASI1600 @ Unity Gain. My skies are ~18mag/sq", right at the border of a red and white zone. I'm using 30 second subs with RGB filters, and swamping read noise squared by ~150x...

 

I'm also clipping over a dozen stars, some a fair amount. 


Edited by Jon Rista, 26 March 2019 - 06:11 PM.


#12 OcativeOrg

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Posted 26 March 2019 - 06:29 PM

I am right out side of Washington DC, it is not good. I have a sky glow filter and shooting 1 shot color. 

 

I guess I might try 30 second subs. 




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