Super Moon - Blood Moon

The most unusual thing about last night was that in the UK, well Hampshire anyway, we had the clearest, quietest and moderately warm night that I can remember for a long time.  That meant that we had very good conditions for a rather unusual astronomical event.  Normally, our luck runs along the lines of “interesting stuff happening tonight”, with the interesting stuff being something like a lunar eclipse, meteorites, aurora etc. Sure enough the event is then bound to be hidden by anything from overcast skies to a full-on storm.  Almost always it’s a complete anticlimax.  It’s even happened for me with solar eclipses.  

Last night was a welcome exception and we were able to see the full ‘super’ Moon combined with an eclipse of the moon by the Earth.  All from my back garden.  It was well worth the effort of getting up in the middle of the night to watch the spectacle and feeling a bit knackered today.  We did some viewing through binoculars - no telescope here but it didn’t really need one.  

I also took the opportunity of taking the photos shown here.  All the shots were taken on a Nikon D7200 with a (very new) Nikon 200-500mm f5.6E plus a Nikon 1.4 teleconverter (which amounts to a 1050mm f8 lens equivalent).  Mounted on a hefty tripod (Gitzo GT3532LS) plus head (Uniqball 45X) and shot with mirror locked up and a cable shutter release.  All exposures were manual to get over the challenge of a bright subject against a black background.  I also used manual white balance because using Auto WB is going to screw up with a heavy colour cast on the subject.  All images were moderately cropped and processed in Lightroom, mainly with a little noise reduction for the high ISO pics.  

First, the full ‘Super Moon’.  Last night, the moon was at its closest orbital distance (i.e. perigee) to the earth so appeared bigger and brighter than it normally does.  We had quite strong moon-shadows!

Next, partway through the eclipse.  At first it looks like a crescent moon but it is different because the eclipsing moon has a soft or ‘fuzzy’ boundary between light and dark areas of the surface caused by light refracting through the Earth’s atmosphere.  Normally that line (i.e. the ‘terminator’ between day and night) is sharp and distinct on a crescent moon because the Moon has no atmosphere.  At this stage, the part of the Moon’s disk in eclipse shadow doesn’t look very red because the sunlight on the remaining surface overwhelms that faint glow (see the footnote for a techy discussion on this last point).  

Finally, the fully eclipsed ‘Blood Moon’ at about the fullest part of the eclipse.  This is very challenging to photograph.  First, although you can see it well by eye when attuned to the dark, there is very little light now being reflected (and all the stars come out - a few are caught in the frame).  Autofocus doesn’t work and it’s also difficult to focus manually because it’s so faint.  Additionally, the Moon’s angular velocity is quite high.  It visibly moves across the viewfinder as you are trying to focus.  I think it’s generally recommended that you need 1/400s to really freeze it at this sort of magnification.  Here I had to use both a high ISO and longish shutter speed.  Motion isn’t entirely stopped but this was the best compromise I could get so I’m pretty happy with this being decidedly not an astro-photographer.  

Two bonus points from last night.  First, as far as I can tell, no ‘end-of-days’ event has taken place.  I always prefer not to wake up to find the Earth tearing itself asunder.  That just spoils the day.  Second, as I was standing outside watching with my wife at 4am in the pre-dawn cool, we could hear a tawny owl screeching away as it flew around the local area.  Unfortunately but not unsurprisingly, we were not lucky enough to get a glimpse of the bird.  But its always good to hear owls in a town.  


Footnote: For the technical minded, looking at the exposure values of the partial and full eclipse images, there is about 13 about ‘stops’ exposure difference between the mid values of the two images. That means the shaded area in the partial eclipse image is reflecting less than 1/8000 the light of the sun illuminated area. That is a lot of contrast difference.  The D7200 sensor, reportedly, has about 9 to 10 stops of dynamic range.  As I’d been aiming to record the sunlit portion of the Moon, the shade area is basically beyond the range of the sensor to pick up any detail.  This coupled with some other factors like the dynamic range decreasing as ISO increases, my exposure not using the very top end of the sensor range and, possibly, using a 12 bit RAW format rather than the camera’s maximum of 14 bits explains why the shadowed areas of the Moon’s disk shows completely black.