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Confused about SNR settings
#1
Question 
Greg,

I am confused about the SNR settings in the Observing Plan -- I'm trying to set a Target SNR of 60 or the "Expose for" Target Object of things like Faint Stars and I get an error under the exposure time for my "No Filter" filter.

The message doesn't really tell me why I am getting the error but I am assuming it is because the program thinks it can't reach the targeted SNR.  Since the conditions under which I will be observing (times, moon presence etc.) are not specified until we get to the scheduler, would this be about my location information? e.g. how bright the sky is? 

I'm operating under the assumption that to reach a target SNR would primarily require more integrations to reach the desired signal level, but clearly I am wrong in this assumption -- can you help me understand what I am missing?

Thanks!

Mitch

Well I answered part of my question, altering the location sky brightness certainly changes the behavior and the exposure times. So one question answered -- the next part of the question is why I am not getting plans for exposure times out to many hours long usually. I'm thinking the program is telling me that going much longer won't have much improvement on the SNR correct?

If that is true, I wonder if there is any value to exposing longer (other than having more subs to select from and more I can throw out if they are not up to snuff).

I'm trying to exercise SGPs ability to gather data over multiple nights automatically so that's what is pushing me to try for such long exposure totals. Maybe this is not the right approach?
This really the first time I have been able to plan and execute multiple observing sessions automatically so I'm taking full advantage, but perhaps I should focus on higher quality subs for a shorter amount of time?

Thanks!

Mitch
17.5" Newtonian w/ Parallax Instruments HD200C Mount
TeleVue NP-101 w/ Vixen GP-DX Mount

Celestron C6 w/ AVX Mount
 
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#2
Hello,

Is this the error?

"One or more filters are unable to reach the target SNR. This may be because the signal is blooming, exceeds the maximum ADU, or is too faint."

If not, what is the error you are seeing?
Clear skies,
Greg

SkyTools Developer
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#3
(2019-04-14, 08:59 PM)theskyhound Wrote: Hello,

Is this the error?

"One or more filters are unable to reach the target SNR. This may be because the signal is blooming, exceeds the maximum ADU, or is too faint."

If not, what is the error you are seeing?

No, just the word "Error" appears over in the Filters section under Exp. Time column on the Edit Imaging Project screen, Exposure Goals and Filters tab.  Here is a screenshot. 
https://www.dropbox.com/s/d8897r6nvd1x0y...e.PNG?dl=0

Well I take that back -- when I click done, I do get that error message.
https://www.dropbox.com/s/d9giixv76xgllm...1.PNG?dl=0
17.5" Newtonian w/ Parallax Instruments HD200C Mount
TeleVue NP-101 w/ Vixen GP-DX Mount

Celestron C6 w/ AVX Mount
 
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#4
Hi,

I'm not really clear on your camera and telescope, but an SNR of 60 (which is pretty high) on a 17th magnitude star is likely asking too much. It's not that you need to expose longer or even expose for multiple nights. It's more that you just can't get there. I think the cutoff in these circumstances is 24 hours of exposure time, and you are not getting to an SNR of 60. Try a more reasonable SNR or a brighter star.
Clear skies,
Greg

SkyTools Developer
Reply
#5
Thanks Greg -- that answers my question. My scope is a Televue NP-101 and Camera is a 60Da with an image scale of 1.642 arc sec/px
17.5" Newtonian w/ Parallax Instruments HD200C Mount
TeleVue NP-101 w/ Vixen GP-DX Mount

Celestron C6 w/ AVX Mount
 
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