Eddington and comets

Members of the Eddington Astronomical Society met at Kendal Castle early on Sunday morning (was that really only yesterday?), to have a look for comet ISON.  There was a good turnout, which meant my photography session wasn’t quite the lonely vigil it usually is. I guess that was down to the presence of the Discovery Channel who are making a documentary about comet hunting, organised through our society Secretary the tireless astronomy outreacher Stuart Atkinson.  To be honest, I was really only there to boost the numbers, as I didn’t think the seeing would be too good – the forecast was well over 90% humidity.

But the humidity wasn’t too bad, especially in our elevated position up Castle Hill, and it was great fun to be staring at the sky with friends for a change!

For the most part, it made sense to stick with the 6 x 60-seconds at ISO 1600 on the new 300mm lens at f/5.6.  I have the dark frames and flat frames for this combination already on file.

First up, comet Lovejoy, very easy to find at an elevation of 54 degrees, well above the mist, and just north of the Beehive Cluster in Cancer.

Comet C/2011 W3 (Lovejoy) 300mm f/5.6, ISO 1600, 6 x 60 sec.

Comet C/2011 W3 (Lovejoy)
300mm f/5.6, ISO 1600, 6 x 60 sec.

 PixInsight allows stacking on the comet centre, so the starts are slightly trailed.

Then on to ISON, by star-hopping from Regulus through Mars straight down the ecliptic.

Comet C/2012 S1 (ISON)
300mm f/5.6, ISO 1600, 6 x 60 sec.

ISON doesn’t present as well as Lovejoy, owing to its position nearer the horizon.

That went well, so a quick trip over to LINEAR, rising next to Arcturus.

Comet C/2012 X1 (LINEAR) 300mm f/5.6, ISO 1600, 6 x 60 sec.

Comet C/2012 X1 (LINEAR)
300mm f/5.6, ISO 1600, 6 x 60 sec.

LINEAR doesn’t look anywhere near as good as last week’s capture.

After that, I left the camera running, for twenty more frames of ISON.

Comet C/2012 S1 (ISON) 300mm f/5.6, ISO 1600, 20 x 60 sec.

Comet C/2012 S1 (ISON)
300mm f/5.6, ISO 1600, 20 x 60 sec.

These have processed quite well in PixInsight to remove most of the sky glow. I might return to these frames and see if I can’t eliminate more of that background colour. I’d also like to try putting the comet back onto a set of frames stacked on the stars.

ISON, finally!

After all the fuss and hyperbole and general excitement in the astronomy press, I finally managed to get a 5am clear sky and have a go at comet C/2012 S1 (ISON), using my newly-acquired (but about fifteen years old) Nikkor ED 300mm f/4. This lens is autofocus, so no reassuring “thunk” as the focus ring hits the infinity stop. On the other hand, it fixes focus on first-magnitude Altair!

The standard for this session was six frames of 60 seconds for all shots. I also took a set of dark frames, flat frames and bias frames, and had a play with the processing suite PixInsight, which I’ve downloaded for a 45-day trial. More of that later.

SITL ISON 6x60

Comet C/2012 S1 (ISON)with Mars
300mm f/5.6, ISO 1600, 6x60sec.

ISON is in Leo, next to Mars, and still invisible to the naked eye. I couldn’t resist a little cheer when I saw this in the camera display. The stars are trailed because the six frames are stacked by aligning on the comet.

1ISON

Comet C/2012 S1 (ISON) with Mars, cropped.
300mm f/5.6, ISO 1600, 6x60sec.

Most pictures benefit from a little cropping, and this is no exception.

ISON agg

Comet C/2012 S1 (ISON) with Mars, cropped.
300mm f/5.6, ISO 1600, 6x60sec.

A bit more crop and slightly more aggressive processing, still looks okay. The tail is tinged with green as the icy comet sublimates and releases cyanogen, emphasised by Mars’s red hue.

2Encke

Comet 2P/Encke
300mm f/5.6, ISO 1600, 6x60sec.

Still in Leo, Comet 2P/Encke is a few degrees to the north.

3LINEAR

Comet C/2012 X1 (LINEAR)
300mm f/5.6, ISO 1600, 6x60sec.

Comet C/2012 X1 (LINEAR) is only a few degrees away too, in the constellation Coma Berenices.