Odd speckles in flat files

ice crystals, possibly.

Willem Jan Drijfhout:
Looks indeed like condensation on your sensor. If you look closely, you will probably find them on your lights as well. Turn off cooling for a bit, until they're gone. Then turn cooling back on but try to cool down very slowly.

Indeed and alternatively, letting the camera stabilize at its cool down temperature for 15-30 minutes before imaging can help with icing.

That's it thanks guys. It was dew. problem solved.

If this is a sky flat then I vote stars, the dots are too well defined to be dew. When you do sky flats you have to make sure that the sky is bright enough and the exposure short enough that this doesn't happen. You could use a diffuser but that just makes it more complicated then it needs to be. I've recently started using NINA's flat wizard and it's great. In multi mode when you tell it to go it will step through all your filters and automatically find the right exposure for the percentage of the histogram you want. I generally run it about 10 min. after sunrise and it works a treat.