Blood Moon: a rare & stunning experience

After the supermoon in fall 2014, the next big astronomical event was to follow on September, 28th 2015: a lunar eclipse. For about an hour, the full moon was entirely in the earth’s shadow and turned into a so-called “blood moon” due to the red light being deflected by our atmosphere to the moon’s surface. That and the fact, that the moon – being very close to the earth – also was a “supermoon”, made this event a “not to miss one”. The next constellation of that kind will take place in 2033! So: how to catch such an event with your camera?

What lens to use?

With a normal wide-angle lens, the moon would just appear as a small dot of about 1mm size on a postcard sized print: smartphones for sure are a no go. A large zoom or telephoto lens must be used: for cameras with a “crop sensor” 300mm – 500mm are a good starting point, “full frame sensor” users should look at of 500mm and above, if they aim to catch the moon up close. With those focal lengths, a sturdy tripod, remote shutter release and mirror lockup are a must to get a sharp picture.

How to focus?

With a clear and bright moon, most lenses have no problem focusing properly. If your camera offers the option to switch from phase autofocus to contrast autofocus (most of the times, this happens by choosing “live view”), do that! If you are looking for the last bit of sharpness, do it manually by electronically zooming in on the display of your camera and adjusting focus meticulously.

Proper exposure

You for sure have made the experience, that a bright, full moon calls for exposure times of 1/50 to 1/250, depending on the aperture and ISO-settings you use. You should use spot measurement, and I suggest to underexpose a bit. Best to also check the histogram or at least mark overexposed parts by using options such as “highlights” on your camera’s display.

Special case “blood moon”

To properly photograph the lunar eclipse needs some special considerations. First of all, it is pretty dark, since it is in the earth’s shadow and only illuminated by the red spectrum of the light deflected by earth’s atmosphere. This requires long exposure times. But be careful: the moon travels fast, and since you use long focal lenghts, the maximum exposure time to get a sharp shot is limited. With a 300mm lens, you should not exceed 1 second, better be below 1/2 second – the longer the focal length, the shorter the maximum exposure time.

To achieve these exposure times, you have to raise ISO, which, together with the red-ish colours, makes your pictures prone to noise. At certain times, I had to raise ISO to 6400… So: choose a lens with a high maximum aperture, that will give you better results.

Focusing on the blood moon is tricky, too. Auto-focusing in live view is not possible at all, manually focusing extremely difficult. So: better use the bright moon before the eclipse to focus, then switch over to manual focusing mode and do not touch focus! Please don’t assume, you can rely on the “infinity”-mark on your lens: with most modern lenses, this will NOT produce proper focus on distant objects…

On astropix.com, I found an in depth article by Jerry Lodriguss on focusing methods for astrophotgraphy. The so-called Hartmann Mask seems to be a very good way to achieve proper focusing. Unfortunately, I discovered that article too late to test it with the lunar eclipse…

I invite you to add your tipps and tricks on astrophotogography in the below comments section and to view the gallery of my blood moon pictures and some other of my favourite moon-shots.