Sunday, 29 March 2009

The Green Owl

We had a pretty display of stars from the city the other day; a clear, transparent night seemed to be underway so I got my 8" SCT out and drove up to the middle of a dark heath with a view over the sea. Fantastic! The light from the north came more from the milky way looming in the background, stationary above the sea. There was an aurora-esque shaft of light shooting out at right angles across the constellation Cepheus. A few dark clouds were actually sillhouetted against the milky way background. Ursa Major was approaching over head and I pointed the scope to it, attached my camera, focused, but the strong, cold wind was blowing the stars into little fuzzy flower shapes. I removed the dew shield, knowing that the wind would look after any condensation and set to work with a few 1 minute long snaps of the Owl Nebula, M97. Half way thorough, I ended up changing the 9V battery for my motor, and trying to repair a broken wire that has broken under field conditions like that was not nice. I spent ages trying to get Deep Sky Stacker to recognise my fuzzy stars but it was useless - I forced it to stack 16 in the end (which I had individually modified) and then it gave me stupidly blue pictures. I spent an equal age trying to work with Registax and I processed in Paint Shop Pro. The pic here is the 16 x 1 min Deep Sky Stack, ISO 1600. Apologies for the slightly yellow stars. You can see the Owl's eyes and central star. The Owl nebula, M97 is a 3' wide, 12th magnitude planetary nebula near the tip of The Plough.

Thursday, 19 March 2009

Venus sweeps inside Earth's orbit

On approach to 'inferior conjunction' Venus is now a large, thin crescent, oriented horizontally - a rather strange angle for such northern latitudes and disappearing rapidly into the twilight. I dashed out to a local field with my brother and got about 40 very rapid snaps straight down my 8" SCT using a 2x barlow lens (f.l. ~ 3.9m). It's amazing how bright it still was considering how thin the crescent phase was, which by the way was easily seen in 10x binoculars and not quite by eye. I could see a fine backlit lower edge to the globe at 200x, seething in the low atmospheric turbulence and its brilliant white colour was dispersed into a near perfect spectrum. I stacked the best 17 of the 1/500" pictures (ISO 1600) and got a beautifully smooth rainbow crescent. Whilst this looked wonderful I had to use the RGB realign tool in Registax to shift the blue down and red up by 8 pixels to get a much sharper white crescent. Here's the final imaged cropped to a 500x500 bitmap.

Sunday, 15 March 2009

Lulin encounters the Eskimo

Popped down to the observatory tonight as the weather was virtually promised to be clear. I had to walk past a load of kids getting up to dodgy things in the village hall car park as they had parked in the way of the gate to the observatory field. I don't mind 'club' music but there was some boring but extremely loud, monotonous, repetitive rave music coming from the hall where they were all gathered outside, smoking. Still, they were no bother, the moon was out of the sky, the floodlights weren't on - the only problem was the large amount of passing cloud the weathermen hadn't predicted again - the liars! (about 5 'octas' worth, I believe). I could see the constellation Gemini, which is where the comet Lulin was currently sailing as it was quite near overhead. The scope worked fine, I got lucky with several clear patches and captured 6x30second pics of the comet, but then I realised the comet was very near the Eskimo or Clown nebula. I squeezed both into one camera field at a push and got 3 shots - and thought this was much more worthy of a blog entry. The nebula is slightly overexposed, but it was a balancing act to process. I've included the Lulin shot also, processed to see the tail. I put the telescope to sleep (as we say) and got straight out and straight home in good time for bed for once (not that I have gone to bed, I am an astronomer after all).

Tuesday, 3 March 2009

The butterfly nebula in the constellation of the unicorn

I pushed the processing of this little planetary nebula (NGC 2346) until I could just see the wing shapes around it, that give it the name of the butterfly nebula. It was not obvious to see visually, although there was definately a bluish haze around the central star. This star is a spectroscopic binary, and is variable - possibly due to dust orbiting around the pair every 16 days. The dust could also explain the infra-red emission. I thought I'd give you a wide field shot; 20' x 30' is the raw field from the 20" scope and I took 8 x 15 second pictures at ISO 1600 on the Canon EOS 350D.