Thanks Peter for reminding me of that thread, found it here:
http://nikongear.net/revival/index.php/topic,7150.15.htmlFrom that, unless there has been a firmware update improving the situation, it does not seem that D500 is a prime candidate for astrophotography use in the cold unless an external battery pack is used. With the limitation of doing 30 sec exposures, I hesitate to ask you to tax your shutter that much with meaningless exposures, however if you insist I would suggest the following (after all it sounds like one would not get that many shutter actuations).
The following assumes that you have a freezer with room for the D500 without any grip:
1. Set shutter speed to 30 seconds, ISO to 1600 (that is what I typically used for deep space imaging with a telephoto lens - going higher might blow out stars, depending on background illumination). If you have an AF lens attached, set AF to manual.
Set Exposure Delay Mode to 3 seconds.
2. Program the D500 to start exposures 2 hours ahead (to allow it to cool down), interval 36 seconds (to allow for writing to the card), number of exposures to 999x1 .
Do not turn on live view.
3. Put the D500 with lens and lens cap on in a ziplock bag and place in the freezer right away in a normal horizontal position so that it rests on the base. (simulating attachment to a tripod).
3b (Ideally you would swap battery shortly before 2 hours are up with a warm fully charged one before it starts exposing, but as the interval timer will then have to be restarted and condensation can form during the swap, you could skip this step and just test worse case scenario with a cold battery.)
4. Let it sit until it is no longer able to make exposures, for instance you could check back after 3 hours, considering your previous experience.
If you have a suitable freezer thermometer, record the temperature when removing the camera.
Let the camera warm up at room temperature in the ziplock bag.
5. Study the frames and count the numbers and time of first and last exposure.
6. (You might have go into the exposure delay menu again with a fresh battery and stop/reset it, as it sometimes want to go on even if the previous battery run out.)
Comment: I did notice in your previous thread that problems appeared at ISO 3200-6400, but I think it makes sense to use ISO 1600 for the test. We need to keep in mind that for astrophotography and particularly deep space imaging, it is not the ISO but the amount of light gathered that determines noise level. ISO adjustments are just used to ensure that the background signal is digitized at a high enough level to allow stretching, typically histogram 1/3 from the left.
By the way, how did you solve your problems on the occasion of the referred thread?
One last thought is that if the battery is charged at very high temperature, the charger might cut off before it reaches its nominal charge as voltage will be higher, so find a cool place with normal room temperature to charge batteries if possible.
