Focussing on the night sky

Hi everyone,
I was trying to photograph the constillation "the plough" last night, but had real problems getting my camera (D7200) to take anything, as i presume it had nothing to focus on.
I wasnt looking to achieve any amazing astrophotography shots, but found it difficult to get anything at all.
Eventually i switched lens to the kit lens, 18-55mm and managed a few shots. It wouldnt let me use my remote shutter button though, so i got some minor blur as i had to manually use the shutter release on the camera, to get it to take at all

Is there any way of "over riding" the system so it simply takes the picture regardless? I was hoping that with a long exposure it would have picked out the stars, but it simply wouldnt take at all
Any help would be appreciated
Thanks

Have you tried putting the camera in manual focus mode and manually focusing it? I don't have a 7200, but I would think this should work for most cameras.

On the d7100 In Custom Settings Menu "Auto focus" a1 AF-C and a2 AF-S can both be set to Release in which case the camera will take a picture in focus or not. Probably the same locations on the d7200.

Manually focus on something distant (infinity) and leave it there. At my house, there is a very distant street light that I often focus on for my night sky shots. In manual focus the camera will not attempt to refocus on the sky and it should let you release the shutter regardless of focus. The night sky is too dark for autofocus. But if the moon is visible you can usually autofocus on the moon. Also use manual exposure with auto iso turned off. Play with shutter, aperture and iso settings. Keep iso fairly low. Start with 100 and only raise it if you must to keep the shutter speed faster. I don't know anything about star movement, but the moon is too fast moving for a slow exposure and will show a trail unless you use a fairly quick shutter speed. You can practice on distant street or house lights. Things in the sky are sunlit but tiny so your camera will badly over expose the scene if left on its own.

nickt said:

I don't know anything about star movement, but the moon is too fast moving for a slow exposure and will show a trail unless you use a fairly quick shutter speed. s Things in the sky are

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@Wakefieldowl - Good advice from nickt (see above) and with regards to the exposure you should apply the 500 rule. For example if you were using a 50mm lens for stars then the maximum numner of seconds you should expose for to avoid star trails is 500 divided by 50....so 10 seconds. However if you used your kit lens at 18mm then it would be 500 divided 18, so you would get away with about 28 seconds.

Thank you all so much for great advice. It really is much appreciated.
I tried again last night using your advice and got much improved results
Thanks again

If you know ahead of time you are doing a night shoot, you can focus to infinity during the day and use some gaffer tape or do like others suggested above. If there is a planet to focus on, it makes things easier.

You can use "mirror-up" and use an exposure delay (d-4) to help prevent camera shake. If you don't like "mirror-up" you can still set the exposure delay or use the self-timer (c-3) to let the camera settle down after you press the shutter. I think the self-timer allows for a longer delay.
I use 'live-view' to zoom in, and I have a small magnifying glass because sometimes you think the stars are in focus, and they aren't. My vision is terrible, so I need all the help I can get.

Another thing to keep in mind is that on nights when the atmosphere is unsteady (poor seeing), it can be really difficult if not impossible to get a sharp image because the stars twinkle so much.

My fn2 button is programmed for "my menu" that way I can access the exposure delay and other items I use often without diving into the internal menus every time (and not remembering where the setting I need is located ) I also have a bank set-up for night time where the exposure delay is always set at 4 seconds.

If I can find the link of the tutorial I watched, I'll post it.

Peter7100 said:

@Wakefieldowl - Good advice from nickt (see above) and with regards to the exposure you should apply the 500 rule. For example if you were using a 50mm lens for stars then the maximum numner of seconds you should expose for to avoid star trails is 500 divided by 50....so 10 seconds. However if you used your kit lens at 18mm then it would be 500 divided 18, so you would get away with about 28 seconds.

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Doing a little napkin math, at 10 seconds, the proper F stop for the moon at ASA 100 would be approximately 10 stops down from F16. This is assuming you use the sunny 16 rule for the sunlit moon surface. All the F stop charts I see usually stop at F64. This would be way beyond that.

My point is movement of the moon is not an issue for pictures exposed properly for the moon. Stars, requiring so much more exposure, are a different ballgame, despite moving more slowly.

Now, if you are using a shorter focal length lens, are exposing for stars or some other much dimmer subject, and are not interested in any detail in the moon itself, then you could get into shutter speeds that produce an arc or an oval vs a dot.

Thank you all so much for great advice. It really is much appreciated.
I tried again last night using your advice and got much improved results
Thanks again

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@Wakefieldowl - please be sure to log in so your posts are visible to the forum members. I'm glad they were able to help you.

With a D7200 the way to do this is manual focus in LiveView. On your tripod set the camera or lens to Manual Focus. Now activate LiveView, move the focus point box in the LCD using the cursor pad to a prominent visible star. Now use the zoom+ button to zoom in the display view as far as it goes. Adjust the focus ring by hand until the star is as small as possible in LCD. Small point of light=infinity focus.

This can be done for any night sky photography. Taking photos of the moon, Venus, or some other planet: pick a star to focus on first. Infinity focus on a star is infinity focus on anything in the sky.

Thanks so much for all the replies. I have tried again using the methods and had much improved results
Thanks again