What exposure time should I use?! Let's answer that!

What exposure time to use for astrophotography is a recurrent question, especially with the waves of CMOS astrocameras now on the market. In this video, I answer this question, from my happy go lucky point of view! Well, that's how I roll, sorry for being lazy!
More seriously, as always, I may be wrong - so let me know in the comments how you determine your exposure time, and if you have any suggestions or if I made some glaring mistakes! This hobby is a continuous learning opportunity, that's one of the things that's great about it.

I am planning to have a video explaining shot noise and thermal noise as well and stacking - and stress the importance of SNR as what we are after!

#astrophotography

[SKYSTRY]

When I tried the exposure calculator, I thought I had accidentally discovered the event horizon of a black hole as it was recommending infinite exposure. Then I realized I had left my lens cap on.

[MrGChuff]

Phew (flops onto chair, cloth in hand, dabbing beads of sweat from ones forehead) ADU and exposure length explained in a simple bite size way. Thanks a million from a mono newbie

[ricardoabh]

Great point, light pollution and filter are critical for this calculation.
But it does deal a bit weak, your method seems good

[astrodysseus]

Good video, but just a small addition. While there are many advantages to expose as little as you need (be sure any of the R, G, B channel are just detached from the left border of the histogram), you may have some cons: you have to stretch your data more, and with that, any imperfections in the data. I am thinking particularly of some sensor banding and pattern issues. They are not always filtered out from flats (even though you can see them here too) and I find that exposing slightly more is better (being 1/4 or 1/5 detached from the left side).

[AnakChan]

Great review. I didn't know N.I.N.A. had a calculator. Taking lots of small exposures do require a decent PC setup behind it. I only have the ASIAir Pro and last week, was contemplating taking pictures of Homunculus Nebula - then realised, to take 100ms exposures with the ASI6200MM (62MP producing 122MB files) was probably NOT a good idea :D.

[johndaley]

I asked about exposure time on one of your newer videos. Did a search on your earlier videos and of course, found this one. I don't plan on using NINA but winging it seems to be the best approach. There's no magical, use this for all. I'm going to look at it as part of my learning curve. Thanks for your insight and being able to express your knowledge. It has helped me a lot.

[jean-clauderoussil]

You not so much lazy, you give me good instructions to do the best of my camera, keep going, god bless you!!!

[angusfraser]

I got this working, I did the SmartCap analysis. What is not obvious is where the sensor analysis is stored. After some seraching I found out it is in your gome user directory under To see appdata you will have to show hidden files in your home directory. Now I poinjt at the sky and get a suggested exposure time which is remarkable good and WAY shorter than I would do if I were doing by eye. Thanks for the video as always great content.

[allenbaylus]

Put my scope up a few weeks ago in a clear night.

First time with my SCT in a year.

I was shooting M101.

5 min looked ok. 2 min and 1 min looked faint.

Shot a few hours at 1 minute expecting to stack then with less star streaking. PI decided that it was not interested in my under exposed pics.

I later realized that I left my L-Extreme in the filter drawer.

Still I should have reviewed this before shooting.

[starpartyguy]

I am only imaging at Cherry Springs state Park, Bortles 3. For years I used SBIG cameras, all with Kodak ccd chips. When I was getting started, I asked around for exposure time suggestions. I kept hearing 10 minute subs. I’ve been doing this for 10 years. Now I move to the Sony cmos chip in a QHY 268m. And since I’m using a c9.25 at f/10, I am binning at 2x2. Obviously I don’t need to use 10 minute subs. So I cut it to 3. I can’t imagine using exposures shorter than that.

[alanrichards]

Think of it this way, you have a 12 oz glass a 6 oz glass and a 1 oz glass out in the rain, after 1/2 hr the 1 oz glass is full and the other 2 are 1/6 and 1/12 full as it continues to rain the glasses keep filling except for the 1 oz which over fills, now think of the 1 oz glass as high gain and the 12 oz as low gain or exposure time. Most people think that if they expose for 5 min they are getting better results because there single frame has more detail in it but in many cases it's like the 1oz glass which is overfilling, sure the bottom looks good but were is the top it's in the 6 and 12 oz glass. They have full dynamic range and the 1 oz glass has low end range but loses it in the high end. The best results will be to fill the glass (any one) 90% full and shoot more exposures. So from my house I go out and shoot 100 exposures at 30 sec the dynamic range is good but no shadow detail so I shoot 100 more and it's there so now I know for my sky and moon I need to shoot 200 at 30, from a dark sight I might get away with 100 at 30 but in either case you would get full dynamic range. Secondly as for banding in images if you stretch your bias and the histogram shows it to fall into a range of 0 to 500 lets say your lights have to start above 500 (600 - 1000) is better if the light starts it base point at 250 you get banding in you image it is not a software or driver problem it's exposure.

[yangyunbo]

thanks cuiv, i will try this function in nina.BTW nina has inproved a lot, i just used the 1.8.10 version but the 1.10 beta looks much better than before

[danielmills]

Cuiv! another cracking video, thank you for all your knowledge and info! Clear skies brother

[miodragpetkovic]

You are The Legend Geek not Lazy... Superb and so inspirated videos. Keep going and full suport.

[dravenack]

You have explained the best I have seen and I have read a lot always leading me to confusion…and I tried asking on an astrophotography forum and those assholes just rip me a new one for not being as smart as them..so thanks

[alanrichards]

I was just thinking I started this hobby with a Atik Horizon OSC and there software limits your exposure to 120 seconds, you can overnight it and expose for 2 hours if you like but they know with the sensor they have and there gain settings over 120 seconds will over fill the well, so they recommend low gain for max dynamic range, I think they are playing to the beginner, make it simple. My feeling is that max exposure is were a unstreched image will show maybe 1 star or no stars but yet start it's baseline over the bias.

[thebst]

Helo cuiv whats the best exposure for the hyperstar?

[testboga]

You want to use the median to not get screwed over by extreme values. Median is the correct value.

[elmikol]

Another outstanding video Cuiv! I like your sense of humor!

[ericbelanger]

Merci pour les excellents tutoriels :) un beau bonjour du Québec :):) merci encore