I have recently began taking more pictures at night. I have noticed at 100% view I see small red and purple specks that I do not believe are stars. They do not trail like the stars. These are 1 minute or less exposures.
Is this "noise" or something else. I do a poor job staying out of dusty areas and wonder if there is something inside the camera.
Your assumption, that there may be noise in your shot, is absolutely correct. But there is more!
In night photography, the two problems, most often met, are noise and compression artefacts. The noise is taken care of with the settings prior to shooting and the artefacts with the right option selection before publishing.
The noise: This is rather easy to get under control. Since you know that you're heading for a long exposure time, make sure that the ISO setting is low, 100-200 ISO. That should do it!
The compression artefacts: This is responsible for the "muddy" rendition of the uniform black areas in the shy. To keep this in check, select highest quality compression before saving/publishing to jpeg. This ugly artefact is a side effect of too high jpeg compression.
I hope I answered you question. If yes, I want to see your next shot.
>> So for a given ev a longer exposure at a low iso is better than a shorter exposure at a higher iso?
That is a general rule of thumb, but in an image such as yours, it isn't necessarily quite that simple.
You did not indicate your exposure, nor does your image contain the shooting EXIF. But if you significantly reduce ISO (slowing the shutter speed to compensate) you will significantly increase the star trailing. You may or may not want that. You have to find a happy medium between the star trailing you will accept and the noise you will accept.
Noise reduction tends to treat stars like noise. There is not much difference between the odd bright noisy speck and a faint star, especially if there is no trailing. I think that tends to limit the amount of NR you can apply, and that has to be considered too.
I'm not seeing the "small red specks" even on the larger view, but these may be hot pixels which show up more with long exposures. In camera "long exposure noise reduction" can be used to removed these.
Thanks to All for your help. I turned on the Long Exposure Noise Reduction and kept ISO near 100 and noticed the specks gone. Exposed for the same amount of time (1:15sec ish) and everything was better but I need to try again tonight to recreate the image.