"Subject too dark"

[OzStarGazer]

Tonight I could see the sky very clearly and was excited, but my camera would not take a pic because it said that the subject was too dark and that I had to use a flash. I was using bulb and the maximum ISO, which is not that high in the Nikon D5100. I tried to increase/compensate the exposure, but it still would not take a pic.
Anyway, any advice? :) The other day it took a pic OK, even if there was noise because I didn't use a tripod. And there are stars in the photo, so it is capable of it... But today it would not do it...
Thanks!

[LightningNZ]

Apparently you need to take it off the "auto ISO" setting.
Cheers,
Cam

[sheeny]

If there is something large enough and bright enough on one of the focus points for you camera such as the moon, it may take a photo, but otherwise not. You probably need to set the camera to manual focus, so that it doesn't have to "see" anything.

Al.

[OzStarGazer]

Hello, thanks.

It was actually the ISO recommended for stars.

I am afraid Al is right. I will have to try manual focus, although it will be very difficult with an eyepiece and stars... It is funny because the other day it was dark too and the settings were exactly the same. But there might have been a little bit more light. Well, it was in the morning, just past 4am the other day, and yesterday it was maybe 10 - 10:30pm. The manual says the conditions for viewing are better in the morning; maybe the camera notices the difference better than the naked eye!