Monday, 30 May 2011


This is SN2011at in PGC26905 Hydra. I would like to get into doing something useful so I thought I’d make a start by finding what supernovae were out there. I found this on (American Association of Variable Star Observers). Variable stars are not really my interest, but making an accurate measurement of the brightness (photometry) would give me some satisfaction, and if it were to become easy or routine to measure, it might just become rewarding enough to contribute to ‘citizen science’. I have authored a few papers so am aware of what is required, and it is usually a lot of work and stress being accurate enough. However, with the equipment here in front of me it seems a bit of a shame to use it on frivolous fancy pictures alone (as lovely as they are!). Now we have an Atik, we just need a V filter to speed up the process. The trouble with photometry with a DSLR is the green channel data only approximates a V filter and needs to be corrected using the colour (Blue-Visible) value as well as the atmospheric extinction and field flatness.
I got an estimate of 14.90mag at 2320UT (06/04/2011) but that could have been out by + or – 0.20mag and I didn’t have a good selection of reference star data (error based on differences between reference stars and measured values). If B-V for the supernova is 0 then there is a +0.13 correction, so it is 15.03 mag, if B-V=0.7 then correction is 0. The image was also so blurred that the supernova light mixed with the galaxy and some nearby stars. So there could be another + correction. Still … pretty good for a start, and for a faint PGC galaxy low down in Southern Hydra.

Sunday, 29 May 2011

29P/Schwassmann-Wachmann (1) 2345-2351UT 06-04-2011

This faint comet was swimming through Sextans near Southern Leo and it plunges back through the border into Leo in late June 2011. Normally its feeble luminosity would hover around 13th magnitude, but it had had a little outburst that peaked around the time of my 6x1 minute photos (April 6 2011), putting it at perhaps 12th mag. As is usual with comets to me, they look much fainter. As well as dust in the comet's tail, there is some dust obviously on my camera's sensor.

The Headphones Nebula

This secretive little critter is lurking in the unlikely constellation of Lynx (the Lynx in case you didn’t guess). For some reason, you don’t normally find planetary nebulae there. It is called Jones-Emberson 1 (PK 164+31.1). The same Mrs Jones, I believe, that discovered Jones 1 in Pegasus. It looks about as faint as Jones 1, although is listed as brighter. As all astro-imagers say “it needs more exposure”; I only got 10 minutes of good enough quality images. Well, yes, it is a noisy (grainy) image, but it is also one of those very pleasing rare and unusual objects. The nebula looks a little bit ‘on the skew’ but is roughly symmetrical, making it not really look like its moniker above. I had to restack this using the super pixel mode on Deep Sky Stacker to get it to pick 10 1 minute frames, rather than the original 8. I’m a big fan of the super pixel mode – it combines the 2x2 colour matrix into one nice coloured pixel, and means I am not over sampling the image as much. Plus it speeds things up by a factor of 4.

The Spindle Galaxy

It's a galaxy in Sextans (NGC3115). I like the abbreviation for that constellation.


We got an Atik CCD! Woohoo! It’s a 383+, with an 8.3 megapixel 22mm diagonal Kodak chip. Here is a picture of M61, luminance. Stacked in Maxim from 30 x 1 min pics binned 3x3 (9 pixels read out as 1 for extra sensitivity) with the camera at -10deg C. I’ve processed it so you can see all those extra faint outer spiral arms and galaxies around it. I was struggling to combine the 2 x 1 minute Red Green and Blue exposures with the Luminance – the result is below, detrailed a little. Now we’re just fighting against tracking errors and light pollution!


This is the same thing as above with the Canon 1000D and focal reducer.


The star Sirius twinkles on a late winter’s evening. Around it the stars of the greater dog, Canis Major lie. If you imagine a line between the dogs front leg and Sirius, extend it back through Sirius 2 – 3 lengths you will come to the star clusters M46 and M47. This is a close up on the North of M46, with all the brighter stars on the image being cluster members. As you can see there is a planetary nebula (NGC 2438) lying in the same direction as this cluster, which I have brought out in the processing. The nebula is probably closer to us than the cluster, and thus is not really hiding within it. It’s a nice thing to view but sadly we’ll have to wait until late in the year before this curious alignment is in our skies again. I moved the blue down and red up to correct for the atmospheric refraction messing up my pictures of low objects!

Pastel shades of wispy gas

I stuck an 8 inch mask on the 20 inch to cut down the blurring effects of seeing, not realising that by doing a long exposure would reintroduce the blur. Nevertheless, because I was pointing the scope at such a beautiful bright region of spacetime, I captured a pretty pastel picture of these wisps of gas without diffraction spikes. There is a little tuft on the edge of each star, presumably caused by the central mirror edge protruding slightly into the 8 inch mask. I may have saturated the trapezium at the centre, but the nebula centres have come out deliciously mottled and shaded. Especially, see the star at centre bottom with a deep shadow next to it.