Bracketing the Moon

Taking pictures of deep sky objects turned out to be tough.  I had a ways to go and some more equipment to gradually collect before my pictures would improve.  The silver lining is that there is a target in the sky that is much easier to photograph because it is big and bright but most importantly it does not take multiple stacked photos or need long exposures.  The Moon is a beautiful target and I have even seen some great moon shots just holding an iphone camera to an eyepiece and snapping the picture.

The moon does not need a long exposure to get a good shot.  Usually you will not need over half a second of exposure and probably much less.  Every photo session is different and  conditions are going to vary.   Variables include the phase of the moon, the camera ISO, the base aperture, the sky conditions, and even where in the sky the moon is located.  There will be some trial and error to determine the best exposure.

This chart is a simple starting point on where you might start an exposure setting.  This is only a starting point to give you an idea of ballpark you will be in.  In my example pictures below I actually used an ISO 200  setting (instead of ISO 400) and my exposures were much shorter than in the chart.  I want to emphasize that the chart is nothing more than a guide to start with.  The atmospheric conditions, the telescope or lens, the camera, the ISO, and the position of the moon in the sky are all going to change the shutter speed you will need.

There is one trick I learned when shooting the moon that can really help out.  Most DSLR cameras will be able to bracket.  Go ahead and set your camera to whatever setting you are going to shoot your target.   In my case, I chose ISO 200 and a 1/200s shutter speed for a moon that is a little over half full.  Then put the camera in bracket mode and hold the trigger.  Bracket mean the camera will take a picture using the settings you wanted, but if you keep taking pictures it will add over and under exposed pictures.  In other words it will give a picture on each side of the original shutter speed.  My camera will only do a series of 3 photos.  So if I am in bracket mode and push the trigger 3 times I will get the expected picture (1/200s), an overexposed picture (1/50s) and one underexposed picture (1/800s).  The over and under exposed pictures are only over and under relative to the original picture settings.

Nikon D90 "BKT" button in middle of side camera

View when "BKT" button is depressed.  3 photos per bracketed session.

Bracketing helps find the right exposure quicker because the camera is automatically giving you three data points instead of you manually adjusting settings.  In my example the original setting does not look too bad.  The overexposed clearly looks washed out.  I personally like the underexposed the best as it shows detail a little better in my eyes.  The bracketing is a nice tool to see that my shutter speed should be somewhere between 1/200s and 1/800s and helps me quickly narrow down where my optimal shutter speed should be on a particular night.

Overexposed bracket photo ISO 200 1/50s

Original setting ISO 200 1/200 s

Underexposed bracket photo ISO 200 1/800 s