DSLR DSO ISO and Exposure times with camera and lens

[TheButcher]

Hi All,
I got a few questions on how to image with my new DSLR. I ended up getting the T6 and came with the regular lens and a 75-300mm lens. I know it is nothing special, but all I could do right now. I am running it on my EQ6-R and wondering what would be an average setting with ISO and F/Number to shoot for. I plan on imaging the North American Nebula or Viel probabluy around 200mm?

I downloaded Backyard EOS trial and messed around and think I got the hang of it. I just got to work on focusing.

S with that said in Bortle 8 Skies with the moon out, what would be a good target exposure time? I know the moon is not the best time to image, but I am mere practicing and learning. Then to capture them in the RAW CR2 Cannon file and take Darks ns RAW DSS. Do I need Flats as well? Right now I am away from my backyard but in slightly darker skies but still in a red zone, just further away from the white zone.

Any advice would be great.

Thanks

[Baskevo]

Hi the butcher! I am not sure how experienced you are, so forgive me if I'm stating some things that you may already know!

Someone may have a different opinion on this, but from my understanding it all depends on your target, location, and quality of tracking.

As far as the f/number, lower is always better. So figure out what focal length you want for the target, and choose the lowest F/number, that's what I always do. For canon cameras, I wouldn't go above ISO 1600, otherwise you will get too much noise. Usually 800 or 1600 are the sweet spots.

A good exposure time would be one that a) doesn't cause trailing stars, and b) doesn't blow out your image. There are basically two camps: you can go for as long exposure as you can without completely blowing out the histogram, so your images will appear super bright until you stack and process, or you can try to keep the histogram somewhat low, below half way with 30 or 60 second subs. Just make sure you don't do too long exposures where all you see is white (i.e. blowing out the histogram). You will have to experiment with the exposure time, and possibly do some more research on the benefits of exposure time vs. keeping the histogram to the left (maybe someone here has an opinion).

I started with a canon t7i DSLR in a bortle 8, and it was very difficult. All of my pictures were very noisy and there was a lot of gradients. It will make it harder to process, but it can definitely be done! And you'll be able to capture some really cool stuff, even if it is noisy! I would start off with a lower exposure time, maybe a minute, on the Viel nebula.

You will see a huge improvement if you do:
lights - as many as you can get
darks - between 20 and 50
flats - between 20 and 50
bias - same number as flats

I always tried to shoot my darks, flats, and bias with the same ambient temp (so if it's 60 degrees outside when you take lights, you'll want it to be 60 when you take calibration frames), usually right after I'm done with lights. Also, I always did the same ISO for all calibration frames.

-Darks are the same exposure time as your lights.
-For flats, place a t-shirt in front of the OTA, and expirement with the short exposure times (usually between 1 and 3 seconds) with an iPad or something bright in between the t-shirt and OTA. You can also point it at the morning sky with the t-shirt and try that way. Try to get the histogram to between 1/3 and 1/2 the way for your flats. This works for most people, but it may not work (it didn't for me). You will have to keep experimenting. I also recommend taking flats RIGHT after darks, don't turn off the camera or anything, because you can risk the camera shifting or the auto-cleaning turning on (which took me a month to figure out).
-For bias, same exposure as flats but with the dust cover on.

Other tips:
Turn off the screen when you are taking subs to keep the camera as cool as possible.
Turn off auto-focusing.
Turn off image stabilization.
Double check the focus if you are running a long session, as the focus will change with the temp.
White balance doesn't matter when shooting in RAW.
Make sure your batteries are charged!
And always always have fun Even when you are infuriated lol

[TheButcher]

Thx James that helps alot. Especially with the knowing hat I should not gohigher then 1600. I will try to keep it at 800 and see what happens. I am used to imaging with my 1600mm and refractor but sold the refractor and RGB filters to up to a new mount. The iOptron cem70. Still on backorder and ordered a month ago lol was hoping I would of got it sooner and then sell my Eq6 R and get a new refractor and filters. Bur oh well. The DSLR setup was the best I could manage right now. And I thought it would be great to have and learn, then to piggyback wit widefield and to do other photography.

Ill take those calbration frames.

[Baskevo]

Thx James that helps alot. Especially with the knowing hat I should not gohigher then 1600. I will try to keep it at 800 and see what happens. I am used to imaging with my 1600mm and refractor but sold the refractor and RGB filters to up to a new mount. The iOptron cem70. Still on backorder and ordered a month ago lol was hoping I would of got it sooner and then sell my Eq6 R and get a new refractor and filters. Bur oh well. The DSLR setup was the best I could manage right now. And I thought it would be great to have and learn, then to piggyback wit widefield and to do other photography.

Ill take those calbration frames.

Oh wow a month! I am strongly considering upgrading to an iOptron mount in the next week, so that is good to know. I upgraded from a DSLR to the as1600, and I was supposed to sell my DSLR to pay for it, but I kept it to hopefully do some milky way and widefield shots at some point! When I finally make the trip out to the dark site, I'm going to give it ago with just the DSLR, a tripod, and an 8mm - 50mm zoom lens, and see how things go

Good luck butcher! Let me know how it goes!

[TheButcher]

Thanks James,

Yeah I purchased it in late June and just called today, still another 2 weeks. Butto be honest, I am really enjoying this wide field. I am out right now and set the iso to 800 and the lens is at 150-200mm I think and its at F5. I am taking 150 sec exposures and just amazed at how many stars there are. I am shooting the North American Nebula. Beffore that I did some Neowie. Gona take the flats tomorrow, just gona pull it in the garage. Then the Darks tomorrow nightaround the same temps, and some Bias. I never did Bias with my 1600mm or 183mm, they seemed to messs mine up but this is probably differen. But I am hooked on the ultra wide field image so far. So next refractor I get I will ut it on, And maybe the C-11 lol That should be interesting.

Thanks for the help

[Baskevo]

Thanks James,

Yeah I purchased it in late June and just called today, still another 2 weeks. Butto be honest, I am really enjoying this wide field. I am out right now and set the iso to 800 and the lens is at 150-200mm I think and its at F5. I am taking 150 sec exposures and just amazed at how many stars there are. I am shooting the North American Nebula. Beffore that I did some Neowie. Gona take the flats tomorrow, just gona pull it in the garage. Then the Darks tomorrow nightaround the same temps, and some Bias. I never did Bias with my 1600mm or 183mm, they seemed to messs mine up but this is probably differen. But I am hooked on the ultra wide field image so far. So next refractor I get I will ut it on, And maybe the C-11 lol That should be interesting.

Thanks for the help

That's awesome that it is working for you! Be careful with taking flats on a different day. Make sure the sensor cleaning is off, and be very careful not to move the focus (if that is possible with a lens). Either way, you may not need it as much since you are in dark skies, but I have an entire set of subs that I can't use now from my camping trip in a bortle 3 because I forgot to take flats

For the ZWO ASI1600, bias cause problems. Most people take flat darks instead (I am sure you know about that), which are similar to bias frames. To take bias frames with a DSLR, you just take images at the lowest shutter speed possible for your camera (should be 1/4000s). You won't need them if you don't take flats though.

I am excited to see your results! I can't wait to try wide field!

[TheButcher]

Thanks James,

I had a good run until 3am then the started to roll in. I took the camera off the mount and left it in the same position, I only put the cap on. I didn't turn it off, just in case if it would move the focus. I find out after I take the flats and darks today. I wish I brought my lightbox for the flats but oh well I will just use a screen or maybe take it outside to do sky flats. I will do Bias also.

It was a lot of fun just staring at all the stars. The EQ6 R handled it well unguided for 140 sec. Even though it was only 2-3 lbs on there. But I pushed it to 400 sec just to try it out and it was fine, just overexposed.

I will post the images when I process them today or tomorrow.

Thanks again