Iso limit 60d

[Tsleel2811]

I'm getting into astrophotography and I always see people shooting at iso 3200 and above. When I shoot people in a dimly lit room the noise is unacceptable even at 1600. Is there anyway to produce a good photo with a 60d at higher ISOs than 1600? Is it something in the settings? Or the exposure triangle?

[Tsleel2811]

I really do appreciate it. I didn't know there was so much math involved but you already did that for me. I don't think I'm going to venture out into buying a f1.4 lens I can do with star smearing. That's actually what I'm going for here. On another post it was recommended that I take multiple shots and stack them together. I think that's the way I'll go.

If u get a tracker wouldn't it smear the foreground because it's following the stars?

[TCampbell]

So if you WANT star trails, that's a completely different discussion.

Set your camera to shoot 30 second exposures.

Also set your camera to "continuous" drive mode (like you'd use for to burst for sports photography), get a remote (wired) shutter release because these usually have a "lock" button on the shutter.  You can press and lock the shutter button on the release and it'll just keep taking photos continuously.

Then press and lock the shutter button and let the camera continuously shoot another frame every 30 seconds... and leave it going for a good long while. 

You'll need a free program called StarStaX which will merge all your exposures (each of which have a short trail) so that you end up with a single merged frame that has very long trails.

This is an area where longer focal lengths actually help because it means the stars appear to move more in 30 seconds than they would in a wide angle lens.

As for the tracker...

The same rule that applies to how much something can move before you can notice it in the stars ALSO applies to the land.  So without the tracker, the land doesn't move at al, but the stars move at 15 arc-seconds per second.  Tha rate of 15 arc-seconds per second is also known as "sidereal" speed in astronomy (pronounced "sid" "ear" "ee" "ol").

With a tracker that can track at sidereal speed, the stars will appear to not move at all in a long exposure (assuming the tracking head was precisely polar aligned to the celestail pole).

However... if you have a tracker that can track at 1/2 sidereal speed, then the "land" will appear to move at 7.5 arc-seconds per second AND the stars will ALSO appear to move at 7.5 arc-seconds per second.  But recall that at that 15 arc-seconds per second speed, we could divide 600 by the focal length of the lens to arrive at the number of seconds we can expose before we notice the blur.  Well... if everything is moving half as fast (7.5 arc-seconds per second instead of 15 arc-seconds per second) then we can expose for TWICE as long (it's like dividing 1200 by the focal length instead of 600 by the focal length).  BTW, that 600 is based on a full-frame camera so we still have to factor in the crop factor.    But still... if you halve the apparent rate that everything seems to move then you can expose for twice as long.

This means the tracking head is even useful for night time landscapes because it can double your possible exposure duration (assuming it has a setting to rotate at 1/2 sidereal rate, but most of the trackers I know of ... including the Sky Watcher "Star Adventurer", the iOptron "Sky Tracker", and the Losmandy "Star Lapse" all have that capability.)