Basic guidelines for narrowband imaging +/- Full Moon


david w pearson
 

My experience with some full moon limited testing with increasing moon separation distance using a 7nm Ha filter has shown.... that
the background noise will become asymptomatic at about 60 deg distance from the moon.  I saw a 57 % reduction in background noise in going from 18 deg to 42 deg moon separation, and then another 17% reduction from 42 to 63 deg moon separation.   very flat beyond 60 deg.
Background median value is 5x lower at 63 than 18 deg.   
In previous testing from full moon down to quarter moon has shown that the asymptote is about the same at 60 deg.   Of course the background and noise get worse from quarter moon to full moon.    Nothing you can do about that , except either accept the increase in noise or don't shoot near full moon.
SII results were the same.    However ,Oiii doesn't like any moon illumination, so unfortunately Oiii must compete with LRGB for imaging time.

Sorry i don't have any 3nm Ha results to provide....i would guess they would be similar.
dave

Ps....data based on 5 min exposures at -20degC with SBIG CCD camera at 7200 feet.

On Monday, January 17, 2022, 11:16:08 AM PST, Ted Mickle via groups.io <tedmickle@...> wrote:


I’d like to do some 3nm H-alpha imaging about 30 degrees away from the Moon tonight at 1,000mm focal length.

Does anyone have rough guidance on narrowband imaging when dealing with a Full Moon?  In other words, how bandpass, focal length and angular separation can be quantified for each of the narrowband filters?

Any guidance is appreciated.

Ted





Emilio J. Robau, P.E.
 

Thanks Tom,

That is good information with exhibits.


Tom Blahovici
 

Same with the S2 filter. No noticable gradients. They will probably show up when color combined.
On the other hand, O3 shots can't be taken with a moon around in my experience.


Tom Blahovici
 

This was taken 2 nights ago when the moon was 30 degrees away. 20  minute subs with an fsq106 and ap1100. Used with 12nm cheapo baadwr filter. You be the judge...no processing, just calibration. Taken at -25C.
Tom


Emilio J. Robau, P.E.
 

Interesting comment on the OII.  I will avoid that tonight for sure.   I am happy with just Ha.  I also run an X2 guider and have never had any problems with this with or without a full moon.  I don't think you will have any issues on that point.  Ted,  I am going with your parameters and we can compare notes if tonight turns out to be as good as forecasted.


 

Hi Ted

I don't have any quantifiable details to offer, but anecdotally I've had good results imaging narrowband under full moon. 

 I would probably not imagine as close to the moon as 30 degrees due to reflections in the instrument (truss design). Lately I've been imaging Ha and SII @ 8nm about 160 degrees from the full moon. The data looks good to me.

Here's a recent example of 8nm Ha on NGC 2014 about 10 hours (600sec exposures on a 16803 ccd @ 3500mm) under moonlit conditions (including last night's nearly full moon)


I have never had good results imaging OIII under moonlit conditions

Brian

On Mon, Jan 17, 2022 at 11:16 AM Ted Mickle via groups.io <tedmickle=me.com@groups.io> wrote:
I’d like to do some 3nm H-alpha imaging about 30 degrees away from the Moon tonight at 1,000mm focal length.

Does anyone have rough guidance on narrowband imaging when dealing with a Full Moon?  In other words, how bandpass, focal length and angular separation can be quantified for each of the narrowband filters?

Any guidance is appreciated.

Ted






--
Brian 



Brian Valente


Ted Mickle
 

Marcelo,

 

I’m using a non-encoded 1100GTO mount and guiding with a Lodestar x2 camera.

 

Tonight’s forecast is for “mostly clear” skies so I’ll give it a go.

 

Ted

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Marcelo Figueroa via groups.io
Sent: Monday, 17 January, 2022 20:27
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Basic guidelines for narrowband imaging +/- Full Moon

 

Sounds like a good plan, I would just pick the farthest target from the moon that you can. And of course only Ha.

 

And, does your mount have encoders, are you using guiding? I ask because if you are shooting without guiding and based on a modeling of the sky, there is no major problem, the model doesn't care if there is a moon or not*. But if you are guiding, the guiding telescope can easily be blinded by the moonlight.




*please correct if this is wrong.


Marcelo Figueroa
 

Sounds like a good plan, I would just pick the farthest target from the moon that you can. And of course only Ha.
 
And, does your mount have encoders, are you using guiding? I ask because if you are shooting without guiding and based on a modeling of the sky, there is no major problem, the model doesn't care if there is a moon or not*. But if you are guiding, the guiding telescope can easily be blinded by the moonlight.



*please correct if this is wrong.


Emilio J. Robau, P.E.
 

Aaron,

That is probably good advice, but would throw me into the category of not worth trying at this time of the year.  As a result, if the weather permits tonight, I am going for the relaxed standard that Ted posted.   Interested in seeing more data on this.


AaronW
 

Many have advised me that when full, the moon needs to be 60 angular degrees away from your target when capturing Ha or Sii, and 90 degrees away when capturing Oiii.  But that's for a 100% illuminated moon.  Not sure how that changes as the moon wanes.


On Mon, Jan 17, 2022 at 11:16 AM Ted Mickle via groups.io <tedmickle=me.com@groups.io> wrote:
I’d like to do some 3nm H-alpha imaging about 30 degrees away from the Moon tonight at 1,000mm focal length.

Does anyone have rough guidance on narrowband imaging when dealing with a Full Moon?  In other words, how bandpass, focal length and angular separation can be quantified for each of the narrowband filters?

Any guidance is appreciated.

Ted





Emilio J. Robau, P.E.
 

Ted,

I think your plan is a good one.  The problem with this time of year is that the targets get pretty slim as the full moons approach galaxy season.   There are few targets available that meet your criteria.   I have been waiting for three or so days, two of which were actually quite good viewing conditions to get the moon to move east during the early evening so I can target milky way NB targets.   Tonight may be a good night to start and I would be using your criteria.  The further away from the moon the better because even with NB filters, the moon can be pretty devastating and cause some real reflection and gradient issues.   


Ted Mickle
 

I’d like to do some 3nm H-alpha imaging about 30 degrees away from the Moon tonight at 1,000mm focal length.

Does anyone have rough guidance on narrowband imaging when dealing with a Full Moon? In other words, how bandpass, focal length and angular separation can be quantified for each of the narrowband filters?

Any guidance is appreciated.

Ted