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.

 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.

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.

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.

PANSTARRS time-lapse video – processed

The unprocessed version of this video was rather disappointing. See PANSTARRS time-lapse video for details.

I took a fresh look at Fred Espinak’s videos of PANSTARRS, and compared our exposure settings. Fred’s videos used the same camera and lens as mine, but he chose f/5.6, ISO 800, 2 sec and ISO 1600, f/5.6, 4 sec. My settings of ISO 400, f/8, 2 sec are two stops and four stops respectively darker than Fred’s, and it shows.

This version of my same video has been reprocessed in Photoshop to boost the exposure by two stops. It’s crude, but shows how much better that choice of setting would have been. I have also taken the opportunity to sharpen the frames a little, and crop too. The cropping accentuates the judder of the movement caused by taking a two-second exposure every five seconds – and processing to play at 15 frames per second.

Fred Espinak’s video of PANSTARRS with the Moon is just stunning.  Arizona does have wonderful skies.  Cloudy skies in the North-West of England are very frustrating, but I live here by choice, so shouldn’t grumble.  On the other hand, it would be nice to have another go at this comet before it fades away.

PANSTARRS time-lapse video

The frames for this video were taken at Eddington Astronomical Society’s “Comet Watch” public event on Wednesday, 13th March 2013.  A clear but cold evening found us at Kendal Castle with a crowd of up to a hundred members of the public, who joined us in looking through telescopes, binoculars and cameras to enjoy the spectacle.

All JPEG frames 200mm f/8, ISO 400, 2 sec.

Comet PANSTARRS sets on the western horizon from Kendal Castle.

I’m not terribly happy with this one.  It would be easy to blame the distractions of the crowd, people wanting to have a look, ask questions, offer opinions, but I welcome all of those interactions so they can’t be to blame.

I should have realised how much the sky would darken as the comet aproached the horizon in the fading twilight, so a brighter exposure – anticipating the final conditions – would have been better.  That comes down to lack of experience, so lessons learned and I’ll have another go as soon as the sky is clear again.

First night out with the D90

This was the first night out with my Nikon D90 – and its remarkable 18-200mm lens – in December 2010.  I wanted to get a feel for how it would handle at night time, as I was planning to capture the total lunar eclipse coming along in a few days.  Almost a full moon, snow-covered ground and clear skies.  For a newcomer to digital SLR, the functionality of the D90 just blew me away.  Even by moonlight, the D90’s autofocus worked like lightning.

18mm f/22, ISO 1600, 30 sec.

A quick capture of Orion rising behind Kendal Castle.  18mm, 30 seconds exposure and the star trails are just noticeable when viewed at full size (much more on that to come later).

60mm f/4.8, ISO 1600, 1/6 sec.

  An audacious shot direct into the Moon, cropped to show the Pleiades.  Not quite astrophotography, but the possibilities are starting to show themselves.