Pleides untracked

[PatrickO]

I'm hoping to have a go at M45 Pleides using a Nikon D7200 or D7500 (I've got both) and a 200-500mm f/3.5-5-6 lens. 

My first time doing DSO imaging.

What technique and process is best? 

Thinking of 350mm which would frame it like this:

[WolfieGlos]

Hi,

Untracked is possible but you will be limited on sub length by Earths rotation or else the stars will be trails instead of circular objects.

You'll need to avoid star trails, and to work this out commonly it’s the rule of 500, but I found 400 works better (some even say 300). Basically divide your focal length by 400 to get the sub length before trailing occurs in your subs.

So allowing for the APSC sensor, you’d be looking at 400 / (350 x 1.5) so less than 1s per sub. You’ll need a higher ISO, probably 3200 if not more, and then manually track the target as it moves across the sky.

I’ve never done this with longer focal lengths, only 10mm or 35mm lenses (20s and 7s subs) so good luck with it 🙂

[PatrickO]

1 hour ago, WolfieGlos said:

Hi,

Untracked is possible but you will be limited on sub length by Earths rotation or else the stars will be trails instead of circular objects.

You'll need to avoid star trails, and to work this out commonly it’s the rule of 500, but I found 400 works better (some even say 300). Basically divide your focal length by 400 to get the sub length before trailing occurs in your subs.

So allowing for the APSC sensor, you’d be looking at 400 / (350 x 1.5) so less than 1s per sub. You’ll need a higher ISO, probably 3200 if not more, and then manually track the target as it moves across the sky.

I’ve never done this with longer focal lengths, only 10mm or 35mm lenses (20s and 7s subs) so good luck with it 🙂

Thanks! 

I could take the focal length to 200mm and use 1 second exposures for simplicity.  However, I would then be using less of the sensor.

How many exposures would you say I need?

[WolfieGlos]

It all depends how deep you want to go, and how good of an image you want really.

M45 is quite bright so you should be OK with a few hours. I hope I'm not teaching you to suck eggs so to speak, but the key for astro imaging is total integration time of all your individual frames. It's all about signal vs noise (SNR). 1hour is OK, 4 is better. For a bright target like this you might get away with somewhere inbetween, but if you want to pick up all of the surrounding dust then a lot more is needed. So with 1s subs, that's a lot!!!!

If you've got a faster lens (say f/2.8) then you can get there quicker. A single 1 minute sub at f/2.8 is the same as a 4 minutes at f/5.6.

This is what I achieved in 5 hours last year with a 72ED refractor at f/5.8 in 5 hours, with a Canon 800D. The nebulosity (for me) looked pretty good, and the surrounding dust is showing but is seriously noisy. I don't think I used any noise reduction software on it, which may have helped.

By all means give it a go, be great to see what you get 🙂 And if you like it and want to invest, then a simple star tracker (say a Sky Watcher Star Adventurer) will allow you to track the sky and use longer subs, a lower ISO - and fewer files. Great for shutter count, less stacking time and less storage on your HDD.

Hope that helps  

 

[PatrickO]

18 minutes ago, WolfieGlos said:

It all depends how deep you want to go, and how good of an image you want really.

M45 is quite bright so you should be OK with a few hours. I hope I'm not teaching you to suck eggs so to speak, but the key for astro imaging is total integration time of all your individual frames. It's all about signal vs noise (SNR). 1hour is OK, 4 is better. For a bright target like this you might get away with somewhere inbetween, but if you want to pick up all of the surrounding dust then a lot more is needed. So with 1s subs, that's a lot!!!!

If you've got a faster lens (say f/2.8) then you can get there quicker. A single 1 minute sub at f/2.8 is the same as a 4 minutes at f/5.6.

This is what I achieved in 5 hours last year with a 72ED refractor at f/5.8 in 5 hours, with a Canon 800D. The nebulosity (for me) looked pretty good, and the surrounding dust is showing but is seriously noisy. I don't think I used any noise reduction software on it, which may have helped.

By all means give it a go, be great to see what you get 🙂 And if you like it and want to invest, then a simple star tracker (say a Sky Watcher Star Adventurer) will allow you to track the sky and use longer subs, a lower ISO - and fewer files. Great for shutter count, less stacking time and less storage on your HDD.

Hope that helps  

 

Firstly, to me that is a truly beautiful and astounding image.

Thank you for the information. I'll reread it a few times and try to take it in.

[Swillis]

Might be worth a look at YouTube. 'Nebula photos' has done several videos of untracked imaging including this one of the pliedes. Which should give you a good idea of what to expect.