Histogram

[Astronator]

I was just wondering, how far on the right side of the histogram is "okay" to be after a long exposure?

If I shoot long exposures with my telephoto lens the image becomes very bright.

[Davesellars]

More or less 20 to 33% from the left is recommended.

[Astronator]

Thank you!

[MattJenko]

You may find also, that it is one channel which veers off to the right. As long as it doesn't come up hard against it and saturate then it is manageable, although as mentioned, middle to left is usually the best. If you do find that you are overexposing, but need the duration to get some fainter detail in parts of the image, then do different exposure lengths. I tend to do this to get nicer star colours for nebula images, as the nebula requires longer exposures, which saturates stars. The only object which usually requires different exposure lengths for the object itself is M42, the Orion Nebula, because the core is just so bright.