Taking pictures of really dark objects with Nikon D40?

I have a project for one of my courses that requires me to take a picture of a constellation, since this is the best camera I can borrow off my friends I attempted to take a picture of a different constellation just to test out the camera, but it constantly tells me that the "object is too dark" no matter what mode I try, is there a suggestion on how I can take a picture of a constellation? The specs are on this site http://www.kenrockwell.com/...on/d40.htm

It will tell you that no matter what. Here's what you do: You will need:

Nikon D40
Tripod

First, take the camera, point it at a bright object far away, and push the shutter half way down to focus the lens at infinity.

Second, click the A/M switch to M and don't touch lens adjustments - it's now set to be in perfect focus for the stars. If you do change the zoom or change it by accident, repeat step 1

Thrid, set the camera to Manual mode. Turn the dial on the top to M. Adjust the shutter speed (thumb wheel) to 30" (30 seconds). Hold down the aperture button (behind the shutter button) and make the F number as small as possible - probably somewhere between f3.5 and f5.6.

Fourth - set the camera to self-timer mode. This will prevent the camera from moving when you shoot.

Fifth - Mount the camera on a tripod and push the shutter button. After the timer ends, the picture will take. It could take another 30 seconds to process the photo.

If the photo is too bright, increase the aperture (make the f number bigger) or make the shutter speed shorter

If the photo is still too dim, you can increase the ISO. The site you linked to tells you how to do this. The D40 does decent through ISO800, and could be usable at ISO1600

If you still can't make it bright enough, you need a faster lens (like the AF-S 35mm f1.8), or the cheaper option would be the ML-L3 remote, which will let you have up to a 30 minute shutter speed.

Go to your nearest aircraft graveyard

seriously all you are ever going to get is a few bright spots on a black background.

Set the camera on manual and take a series of photos ( with a tripod if you have one ) exposures up to about 8 seconds.

Look at them on a computer screen to see what results you have as the review screen will not show much detail for this.

Congratulations. You have proven that cameras are just dumb boxes that require substantial and knowledgeable input from the person using it to achieve the desired results. Of course the person using the camera must be knowledgeable about photography and understand how to use the camera in Manual Mode.

Unless you have a tripod with an equatorial mount and a fairly long lens or access to a telescope with an adapter to allow mounting the camera about the best you can hope for is star trails. Astrophotography requires long exposures which the camera is incapable of producing if used in one of the Auto modes. You must be in Manual and set the shutter to bulb and have the camera on a tripod.

These sites will give you guidance:

http://www.danheller.com/star-trails

http://www.astropix.com