I just made an update trying to correct for narrowband imaging. It assumes (or tries to assume) skyglow is negligible and only focus on DSO signal. There is a dropdown "Narrowband Correction." Feel free to test (as long as the image isn't too large)

deepskydetail.shinyapps.io/Sub_Length_C...

Great post! Re narrowband filters: I think in dark skies, there is such low skyglow getting through, that the calculator struggles. That's not a bad problem! Skyglow is usually unwanted noise. I probably need to adjust things to only focus on DSO signal in those conditions.

Are Your Subexposures Long Enough? - Dave's Astrophotography Blog How long should my subexposures be? I'm not sure how many of us put a ton of thought into this. I myself have some rules of thumb that seem to work reasonably well for me. I've done a little reading o...

@deepskydetail.bsky.social recently posted a neat tool for estimating minimum sub exposure times. I played around with it and wrote some general thoughts on noise and subs. photonphanatic.com/2026/04/12/a...

#astrophotography

M81 and M82 taken from a Bortle 3 location.

ZWO 294MM Pro, f/7.5 refractor with 0.8x reducer, about 2.5 hours of data. #astrophotography

Glad you found it useful!

Today's #Artemis II launch.

The fixes are now live. The online tool has been updated, and the buymeacoffee links now have correct versions. You can also get them on GitHub: github.com/deepskydetai...

Hi everyone. I just realized there is a bug in the sub-length calculator code. If you're not using unity gain, then the Min.Sub2 estimates will be off (and some others). The Sub Optimization stuff is still correct. But, I'm going to update the app later today and send out a fix. Sorry about that!

Here is the video that explains the #astrophotography sub length calculator:

youtu.be/1ABUrerGE54

It tries to separate skyglow from stars/brighter DSO. I hope it will be useful. More details will be in the video with lots of examples.

Basically, you load a dark/bias frame, and a light frame, input your camera's bit-depth, e-/ADU based on gain, and light frame's sub exposure time in seconds, and it does the rest.

I made a sub-frame calculator for #astrophotography. It's available free online. as a Windows .exe or a @siril.org python script. Video out tomorrow.

online: deepskydetail.shinyapps.io/Sub_Length_C...)
Windows: buymeacoffee.com/deepskydetail/e/524780
Siril: buymeacoffee.com/deepskydetail/e/524785

Each filter contributes a bit to each color channel. It's a bit complicated, but explained here:

youtu.be/4uUS3vcghiY

This famous nebula has a secret. #science #astrophotography #space YouTube video by Deep Sky Detail

A fun video about the Running Man Nebula. #astrophotography

www.youtube.com/shorts/YHcur...

Got about 13-14 hours of the Soul Nebula over the winter. This is an SHO image, but I used pixelmath to make it more RGB-like. Orion 80ED doublet, ZWO 294MM, various SHO filters I'm testing. I wish I framed it better, but it's difficult without a rotator! @kat-astro-bot.bsky.social #astrophotography

Thanks!

Thanks! Wavelets for the win!

This is about 30 hours of SHO (roughly 10 hours each filter) for the Rosette Nebula. Some people say it looks like a skull, and I can see that too. Rotate the 1st image 90 deg. counterclockwise, and the center of the Rosette is one of the skull's eyes. #astrophotography @kat-astro-bot.bsky.social

Transforming Monochrome Images into RGB with Ha, OIII, and SII. Pixelmath Magic in Siril. YouTube video by Deep Sky Detail

It looks like an RGB image because I combined the stacked SHO images using pixelmath in Siril. I've got a video on how to do that from a couple years ago: youtu.be/4uUS3vcghiY

I've been slowly getting more data of Orion in SHO the past couple months with various filters. I combined ~30 hours worth of data (12 Ha, 9 in SII and OIII each), processing them in Siril and Gimp. I messed with wavelets too much probably #astrophotography #nebula @kat-astro-bot.bsky.social

Thank you!

Measuring the Earth's Shadow. Lunar Eclipse 2025 #astrophotography #astronomy #eclipse #space YouTube video by Deep Sky Detail

This was a fun video I made about last year's lunar eclipse:

youtube.com/shorts/iZWYr...

#astrophotography

And it points out that many imaging acquisition software have histograms that may not be all that useful. For example, the one in Ekos/Kstars shows "intensity" and not "ADU," which makes it really hard to know if you are clipped on the left. Anyway, watch the video. I think it's good :)

If you're looking to minimize satellite trails, planes, guiding errors etc., then you do want shorter sub frames. But, how short can you go? Well, use the histogram to find out! The video goes into detail about the method and tools you can use to analyze your sub frame histograms.

And while it is true that you don't have to pay attention to it, it can still provide valuable information. You can use it to figure out whether your sub-frames are too short. With CMOS cameras and low read noise, sub frames can be very short. But too short is bad.

How to Tell If Your Sub Exposures Are Long Enough. #astrophotography YouTube video by Deep Sky Detail

Histograms, despite what you may have heard, can still be used to figure out what a good sub-exposure time is in #astrophotography. There is an argument I've heard that you don't need to pay attention to the left side of the histogram anymore...

youtu.be/jVGcG989g9E

I've been messing around with adding low frequency data from my f/2.9 sharpstar to data taken with my f/9 RC for Messier 78 in Gimp using wavelets. I'm not sure what to think, but I kind of like it. What do you think?
#astrophotography @kat-astro-bot.bsky.social

Two Times the Detail in Half the Time? What is detail anyway? YouTube video by Deep Sky Detail

I did a quick video comparing two pictures I took of M78. One had 12 hours of data, the other had 23 hours. The 12 hour image had much better SNR. But it lacks something! #astrophotography

youtu.be/3wR8A2T7XEM

Thank you! :)