I have a 60Da which is Canon's camera specifically designed especially for astrophotography (the standard 60D filter is replaced with a different filter which allows more full-spectrum light through and dramatically increases sensitivity in the "reds" (camera's designed for normal photography actually trim the visible light spectrum to mimick the sensitivity of the human eye and the human eye isn't actually particularly sensitive to reds.)
It turns out the ideal ISO setting for a 60D is ISO 800.
But there are a few things you need to know to go along with this. I'm doing astrophotography of "deep sky objects" (DSOs). I'm not shots of the Milky Way over landscapes at night. Because of this difference... I either attach the camera to a telescope like I did for this shot:
Or I put the telescope on a "tracking" head (apparently I haven't uploaded a prior example and that shot is on my other computer). But the "tracking head" just means you're using a normal camera + lens combination but the "head" is rotating at the same rate that the earth is rotating -- but in the opposite direction (it cancels out the movement of the sky so you can take very long exposures without the stars "smearing" due to the rotation of the Earth.)
BTW, the shot above is not a single image... I shot many 8-minute long images and those are then combined using a stacking process. The color and contrast details are "stretched" to exaggerate them (otherwise the image would mostly just appear as a black & white). So to be clear... this NOT what you get straight out of the camera. The adjustments above cause the younger & bluer stars to look more "blue"... and the older and more yellow stars appear more "yellow". (So the color differences aren't made up - but they are exaggerated).
I do have some examples of images that where the colors are not exaggerated -- they really do come out of the camera looking pretty vivid. It all depends on the object.
The reasons ISO 800 turns out to be ideal is because this is the magic ISO for a 60D which maximizes the "upstream" signal amplification and minimizes the "downstream" signal amplification. This tends to produce the strongest "signal to noise ratio" (SNR) and astrophotography is all about maximizing the SNR. The reason we shoot a LOT of images of the same object is to improve the SNR even more.
The image-aquisition steps to astrophotography are somewhat nit-picky... and the image processing process is even more nit-picky.
There are numerous web-tutorials that can help... I have found the "photographingspace.com" website and "DSLR-astrophotography.com" website seem to have quite a bit of good info.
Your camera is very capable of capturing fantastic images... but it will require some work on your end (it require work no matter which camera you use.)
