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Imaging narrowband versus a 'darker' sky location.

Filters Acquisition LRGB Monochrome Narrowband One-Shot Color Backyard Astrophotography Dark Site Light Pollution
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Pele Johnson avatar
Pele Johnson avatar

Hi all,

If I am imaging with 3nm filters (either mono or OSC) say from a Bortle 6 location - no moon (my garden). Would using the same filters/cameras in a Bortle 4 location provide much better data, worth travelling to…. or would it not be really as viable for the 2hr drive there and 2hrs back for the difference in data?. I am thinking it has to do with SNR but thought I would throw it out there and ask. I do get the darker the location the better the data but was just interested in whether it is worth the 4hrs both ways to do this. LRGB I get that this would be ideal.

Thank you.

andrea tasselli avatar
andrea tasselli avatar
No, not really…
Arun H avatar
Arun H avatar
Pete - same situation as you. It is not worth the drive for narrow band. It is definitely worth it for broad band, though, although life has a way of not permitting two hour drives back and forth at random times when the weather and moon find it worth their while to throw us a bone.
Quinn Groessl avatar
Quinn Groessl avatar

Darker skies will pretty much always mean better data. But I wouldn’t spend 2 hours of my time and gas money in this situation. For LRGB, I would.

I haven’t yet, but one of these days I’m going to go to a dark sky site that’s about 1.5 hours from me. According to this site its SQM is 21.93. The same site has my house at 21.36, although I know it’s closer to 21.1. The only two reasons I haven’t is because I feel like I should bring a second rig in case people want to see things, and I really like to sleep while my stuff is doing its thing. Maybe next year.

Pele Johnson avatar
Pele Johnson avatar

Arun H · Oct 23, 2025 at 11:28 AM

Pete - same situation as you. It is not worth the drive for narrow band. It is definitely worth it for broad band, though, although life has a way of not permitting two hour drives back and forth at random times when the weather and moon find it worth their while to throw us a bone.

Thats what I was thinking. Yes when the celestial gods align its usually when I cant get there lol.

Pele Johnson avatar
Pele Johnson avatar

Quinn Groessl · Oct 23, 2025 at 11:45 AM

Darker skies will pretty much always mean better data. But I wouldn’t spend 2 hours of my time and gas money in this situation. For LRGB, I would.

I haven’t yet, but one of these days I’m going to go to a dark sky site that’s about 1.5 hours from me. According to this site its SQM is 21.93. The same site has my house at 21.36, although I know it’s closer to 21.1. The only two reasons I haven’t is because I feel like I should bring a second rig in case people want to see things, and I really like to sleep while my stuff is doing its thing. Maybe next year.

Thank you I just received a SQM Meter today, so I am going to try and monitor a couple of these sites I have access to. And I love just going to bed and letting it do its thing. I am trying to find out how to stat very warm at a remote site and make the effort all worthwhile :) A big sleeping bag I can walk in is starting to sound good.

Quinn Groessl avatar
Quinn Groessl avatar

Pele Johnson · Oct 23, 2025, 02:06 PM

Quinn Groessl · Oct 23, 2025 at 11:45 AM

Darker skies will pretty much always mean better data. But I wouldn’t spend 2 hours of my time and gas money in this situation. For LRGB, I would.

I haven’t yet, but one of these days I’m going to go to a dark sky site that’s about 1.5 hours from me. According to this site its SQM is 21.93. The same site has my house at 21.36, although I know it’s closer to 21.1. The only two reasons I haven’t is because I feel like I should bring a second rig in case people want to see things, and I really like to sleep while my stuff is doing its thing. Maybe next year.

Thank you I just received a SQM Meter today, so I am going to try and monitor a couple of these sites I have access to. And I love just going to bed and letting it do its thing. I am trying to find out how to stat very warm at a remote site and make the effort all worthwhile :) A big sleeping bag I can walk in is starting to sound good.

The closest one to me is a state park. https://dnr.wisconsin.gov/topic/parks/newport/darksky

I bought a meter last year. I use it occasionally, but I primarily image from home so once I’ve measured it a few times throughout the lunar cycle I kinda have an idea of what it is.

Tony Gondola avatar
Tony Gondola avatar

I agree with everyone else, probably not worth the effort for narrow band but it would be for LRGB. Another way to look at it, and maybe someone can quantify this but how much SNR would you gain by taking the time and effort to go to a remote dark site verses simply spending another night or two on the same object at home?

Arun H avatar
Arun H avatar
Tony Gondola:
I agree with everyone else, probably not worth the effort for narrow band but it would be for LRGB. Another way to look at it, and maybe someone can quantify this but how much SNR would you gain by taking the time and effort to go to a remote dark site verses simply spending another night or two on the same object at home?

Many years ago, I built this table. The logic behind this was the following: how many hours of imaging time to you need to estimate the mean sky background from a Bortle X site to the same error, as a proportion of the mean, such that this normalized error becomes what you would get from a B1 site? Estimating the mean sky background with high accuracy allows you subtract it out and the DSO is a fixed perturbation on that mean.




This is for LRGB imaging. There are other benefits to dark sky imaging - much easier removal of gradients as an example. There is a big reason people do remote imaging. It is a huge advantage, and not just in the amount of available clear sky time. You can go a LOT deeper in a given time.
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Tony Gondola avatar
Tony Gondola avatar

Arun H · Oct 23, 2025, 05:05 PM

Tony Gondola:
I agree with everyone else, probably not worth the effort for narrow band but it would be for LRGB. Another way to look at it, and maybe someone can quantify this but how much SNR would you gain by taking the time and effort to go to a remote dark site verses simply spending another night or two on the same object at home?


Many years ago, I built this table. The logic behind this was the following: how many hours of imaging time to you need to estimate the mean sky background from a Bortle X site to the same error, as a proportion of the mean, such that this normalized error becomes what you would get from a B1 site? Estimating the mean sky background with high accuracy allows you subtract it out and the DSO is a fixed perturbation on that mean.




This is for LRGB imaging. There are other benefits to dark sky imaging - much easier removal of gradients as an example. There is a big reason people do remote imaging. It is a huge advantage, and not just in the amount of available clear sky time. You can go a LOT deeper in a given time.

Tony Gondola avatar
Tony Gondola avatar

Tony Gondola · Oct 23, 2025, 05:30 PM

Arun H · Oct 23, 2025, 05:05 PM

Tony Gondola:
I agree with everyone else, probably not worth the effort for narrow band but it would be for LRGB. Another way to look at it, and maybe someone can quantify this but how much SNR would you gain by taking the time and effort to go to a remote dark site verses simply spending another night or two on the same object at home?


Many years ago, I built this table. The logic behind this was the following: how many hours of imaging time to you need to estimate the mean sky background from a Bortle X site to the same error, as a proportion of the mean, such that this normalized error becomes what you would get from a B1 site? Estimating the mean sky background with high accuracy allows you subtract it out and the DSO is a fixed perturbation on that mean.




This is for LRGB imaging. There are other benefits to dark sky imaging - much easier removal of gradients as an example. There is a big reason people do remote imaging. It is a huge advantage, and not just in the amount of available clear sky time. You can go a LOT deeper in a given time.

Is this chart indicating if I had a total integration of 39.06 hours in B8, I could get the same SNR in 3.99 hours under B4? I’ve picked B4 because it seems to be a case of diminishing returns as you go lower on the scale. Plus, if you live in B8, B4 is relatively accessible whereas B1 or two would be harder to find or get to.

Arun H avatar
Arun H avatar
Tony Gondola:
Is this chart indicating if I had a total integration of 39.06 hours in B8, I could get the same SNR in 3.99 hours under B4? I’ve picked B4 because it seems to be a case of diminishing returns as you go lower on the scale. Plus, if you live in B8, B4 is relatively accessible whereas B1 or two would be harder to find or get to.


Yes. And yes, B4 is much easier than B1. Keep in mind that B4 is better than it may seem since many B4 sites are "contaminated" by light domes from nearby cities near the horizon. So objects at high sky altitude would be much less effected and could do better than these numbers suggest.
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Pele Johnson avatar
Pele Johnson avatar

Arun H · Oct 23, 2025 at 05:05 PM

Tony Gondola:
I agree with everyone else, probably not worth the effort for narrow band but it would be for LRGB. Another way to look at it, and maybe someone can quantify this but how much SNR would you gain by taking the time and effort to go to a remote dark site verses simply spending another night or two on the same object at home?


Many years ago, I built this table. The logic behind this was the following: how many hours of imaging time to you need to estimate the mean sky background from a Bortle X site to the same error, as a proportion of the mean, such that this normalized error becomes what you would get from a B1 site? Estimating the mean sky background with high accuracy allows you subtract it out and the DSO is a fixed perturbation on that mean.




This is for LRGB imaging. There are other benefits to dark sky imaging - much easier removal of gradients as an example. There is a big reason people do remote imaging. It is a huge advantage, and not just in the amount of available clear sky time. You can go a LOT deeper in a given time.

Thank you, I will go through this and hopefully understand it and make use of it. Thank you

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Jaymz Bondurant avatar
Jaymz Bondurant avatar

Pele Johnson · Oct 24, 2025, 06:02 PM

Thank you, I will go through this and hopefully understand it and make use of it. Thank you

Just remember, as Arun said, this specific chart only applies to LRGB imaging. The concept is still the same with SHO, but there are diminished returns; especially with 3nm filters such as yours. As you can see from Pele’s chart, even moving from a Bortle 6 to a Bortle 5, the reduction in imaging time is quite drastic. Your SHO filters, however, will see almost no difference.

As Quinn stated above, “Darker skies will pretty much always mean better data”. You can remove the words “pretty much” and it’s a 100% accurate statement. If you took your gear to Antarctica’s Dome A, even budget 7nm filters would provide you a small SNR boost because of skyglow and zodiacal light.

I’ve made similar charts for my gear. I live in a Bortle 6 but only shoot in a Bortle 2. This should really put it into perspective. Assuming no filters at all, I could shoot an hour in my Bortle 6 backyard and then go to my Bortle 2 site and get the same SNR in 6 minutes. If I use SHO filters in my Bortle 6 backyard for an hour and then go to my Bortle 2 site, I still need just a hair over 45 minutes for the same SNR. That’s because SHO filters are already so good at blocking out unwanted the wavelengths. So, it’s really just a matter of how far you’re willing to drive for how much improvement. In my case, it’s an hour and a half drive each way. If I’m shooting broadband, I get a 90% improvement and 10x the SNR per hour. That’s clearly worth the drive. With SHO, I get a 25% improvement. That’s not negligible by any means. But is it worth 3 hours of being on the road plus setup and tear down? That’s questionable.

In your case, having very tight 3nm filters and only moving from Bortle 6 to Bortle 4 plus a 2 hour drive to boot, I would 100% stay home (and I’m obsessed with dark skies). You’d probably have to shoot for a week straight before you saw any noticeable improvement. Even with 7nm filters, I wouldn’t make half that drive.

To clarify, though…if you ever want to shoot broadband, the jump from Bortle 6 to Bortle 4 is much more drastic than many people realize at first. If you’re after a galaxy or reflection nebula, I would highly recommend making the 2 hour drive and making a weekend of it. Even if you can only shoot for a single night, the improvement will be very much noticeable.

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