Thursday, 28 April 2011


The billions of stars that make this wonderful smooth shape, which appears nearly edge on from our Galaxy, lie 29 million light years away, in the south of the constellation of Virgo. This vast stellar city is nicknamed the Sombrero galaxy for obvious reasons. Officially known as M104, you can see the bright nucleus, and sharp, symmetrical dust lane around the edge. There are also 1 or 2 background galaxies visible. M104 has been imaged in infrared light that penetrates the galaxy to show the dust lane going all the way around. It's an incredibly aesthetically pleasing object that 'floats' in the sky like saturn with its ring. It lies quite a way outside (south) of the main Virgo galaxy cluster, but is quite bright due to that nucleus. It is a little smaller than you may expect, and the dust lane can be seen with a moderate telescope from the UK, low in the southern sky in spring. This picture was composed from just 7 x 1-minute exposures on the 20-inch BAS scope at f/3 (along with some daylight flat fields that didn't work). It just looks beautiful to me.

Tuesday, 19 April 2011


Now I’ve got my modified camera – look at all the red stuff it reveals. This is the jellyfish nebula that I blogged before. I can now see all the red stuff - Hydrogen galore! – it’s like taking off a pair of sunglasses. I mosaiced 2 pics here. Both were guided on Propus, which is responsible for the shard of light you can see just off the bottom. The jellyfish gives a lovely impression of the nebula floating in the vast sea of the heavens.

Abell 31

I know I’ve been going for faint targets, but this one has taken 7 or 8 attempts and exposing various equipment flaws that have shown up along the way. When I finalise the stack of 30 or 40 images, I still see nothing. Possibly a few grainy speckles appear on stretching the contrast. I had to combine 2 or 3 sets of stacks, and keep blurring, brightening, adjusting the variation in the background. It was virtually a month’s project and rather futile really, as there are some much better pictures, with much better equipment out there. Why do I do it? Because I can, and I enjoy persevering with the equipment to see what it can achieve. This thing is so big and faint that it is 0.4% brighter than the overhead light pollution background level (SQM reading averages 21.0). It’s probably even less than that at the altitude I took it at… and I cannot get a decent flat field image! So, all things considered, it might look a bit ugly, but it’s a monster. A strange, old monster that’s dissipating slowly into space. Search for it under PK219+31.1 or Abell 31 (details: 12.2m/17’x16’ – that’s big).

IC 2162

What the hell is this? It looks like some invisible steam train, But then one cloud looks like a poppy. Don’t overlook the little fuzzy on the left. There is a beautiful juxtaposition with the star at far left, which is too faint to be seen with the naked eye. The object here is catalogued as IC 2162 and it appears here a collection of nebulae which are in Orion’s right arm. I wonder if it is connected with the nearby Monkey nebula (below). It’s a relatively smooth picture, as this was quite bright compared to my other subjects, and high in the dark, clear part of the sky. It took about 10 minute exposures to capture this weird thing.

Abell 29

Two red arcs take their trip across the southern sky

Unseen to all passers by

They were once a star that started to die

Surely that must be the first poem written about Abell 29 (PK244+12.1)? The nebula is hidden behind a grainy fog because it’s incredibly faint (14.3m/6x4’) and low down in the constellation of Pyxis the Mariner’s Compass. The grain is inherent in the camera. It took about half an hour’s worth of minute exposures at f/3 on the 20-inch with the modified Canon 1000D. Also a lot of teasing and tweaking was involved in the processing. I keep thinking I can see a hint of blue inside the red arcs. Hmm… a bit of an achievement from the UK, this one.

Abell 21

This large planetary nebula is more of a ragged, asymmetric set of vast gaseous arcs strewn across the outer shell of a little dying star’s former atmosphere. The star is tiny, and shining with an extremely hot blue colour (at magnitude 15.9). If you look carefully, you can see the little blue dot at the centre of the arc. The picture reveals some blue oxygen and hydrogen (beta) emission nearer the centre and more reddish strands further out – presumably hydrogen (alpha) and some sulphur ions. This nebula is known as the Medusa nebula (Abell 21, PK205+14.1) and is located in the South of Gemini. I see Barnfield Bob (see friends) has beaten me to blog an image of this. His optics and tracking are quite superior to the twenty inch I use. Still, I think this stack of about 20 minute-long snaps (+ flats & darks) has revealed a lot of detail in this object. I have tried imaging this object before several times and not been happy with the result on the non-converted camera and unguided scope. I have seen it visually in the scope, and it is quite impressive (the scope is the impressive thing!). It was relatively easy when high in the sky on a dark winter’s night, although an Ultra High Contrast filter was necessary to reveal the ghostly, filamentary details.

Thursday, 7 April 2011

By observing, we introduce a human element to what’s really there.

On one of my rare moments of astronomy time I was aiming the big scope to a patch of nebulosity I had seen in the south of the constellation Monoceros, the unicorn. It was supposed to be the seagull nebula, but I was slightly off in my positioning and was attracted to this rather brighter nebula to the upper right instead. It was around the star HIP34116 (a mag. 7 sub-arcsecond double) and it looked like a heart on my camera, but on processing the heart shape appeared again in a larger form. I’m sure it’s not just me that can see a heart. What’s more, a broken heart! A giant heart-shaped nebula - it always amazes me what stuff is up there. However, hearts don’t really look that shape, I’ve seen quite a few dissected. The shape, called a cardoid (for reasons you may well suss out), is a name for a type of mathematical curve, θ = . I conclude thus mathematics is related to biology (and that was via astronomy). P.S. As I'm posting this, a Radio 4 programme on maths in biology has just come on.

Sigur Rós

This is the rosette nebula (NGC 2237,8). A beautiful rosy coloured object, with filaments, dark lanes, dusty blobs, and meandering, snaking streamers all lit up by a bright cluster of stars at the centre of the central chasm (NGC 2239,2244). It looks like a tunnel, as I am trying to imagine it in three dimensions. I see one of the stars, the bright one at the centre I used to guide the telescope, is slightly yellower than the others. This object is depending on what instrument you are using, annoyingly or satisfyingly large. By annoyingly large, I mean that it won’t come close to fitting into my camera field on the big scope, even with a field-widening lens on it. If you are slightly more impressed with the sharpness of the stars on this pic, it is because I had to mosaic 4 pictures together. As is usual, I don’t want to spend all night on the scope and so I just took one single 1 minute exposure on each quarter of this final image, and merged them all, manually at home. Just 1 minute exposure - that’s nothing, for such a wonderful amount of detail. Perhaps I should do a 3x3 or 4x4 mosaic to get even more of it in, but the astronomer has precious little time. Here is a rough calculation of the time astrophotographers have to work. 60% it is too light because of twilight or the sun is up (depends on latitude). 50% of the time the moon is up, making it too light. 50% of the time it is inconvenient to get to the observatory (plus we need to sleep). 70% of the time it is too cloudy (depends on how much cloud your country loves). 50% of the time your equipment doesn’t work or doesn’t work properly. That’s 40% x 50% x 50% x 30% x 50% = 1½%.

Retro Computer Games

Here is my latest one of the Pacman Nebula in Cassiopeia, captured with about 5 minute exposures on my modified Canon 1000D on the ‘big scope’. He is eating the pills (the stars), although there are quite a few more of them here than in the 80’s arcade game. The nebulosity is more extensive thanks to the camera filter removal (the modification mentioned above). The nebula looks like it has been trailed or blurred, but it actually is like that. The dust lanes have a very wispy appearance. The prominent one is the dark spot at the top, which you can take as the ‘eye’, although I prefer to see the eye as the bright blue cluster (NGC 281). Not a very long exposure was required for this one – I even picked it up in a single 1 minute shot through a 135mm f/2.8 lens and a bit of processing. However I could have done with a fractionally wider field and a better angle.

So faint… it isn’t actually there.

George Abell spotted his 17th splodge on the deep sky survey in this location and classified it as a faint planetary nebula (a fluorescent stellar corpse) of 18.5 magnitude. This is in the realms of extremely dim, 1/40th as bright as Pluto, and Pluto is 1/2500th as bright as the faintest star you can see with the naked eye, and that is dimmed further by being smeared over a small area. The red smear across the top of the photo represents a lesson in how to be careful when taking space photos. It must have been caused by the red computer mouse light from across the dome! When you get into the realms of extremely dim everything’s too light. Phones are out of the question and monitors must certainly be off. Plus there’s an annoying LED that comes on my new camera while it’s exposing. How dumb. Notwithstanding the distracting straight line upper right of centre, I have marked the location and size of the nebula on the photo, where I can sort of half-imagine a very faint reddish ring. Well this was later classed as not a nebula at all it was a plate flaw, which was obvious and just to the left of my marked area. Is it a circular collection of stars below the detection limit of the instrument? Or is it just that the background ‘static’ noise in my camera has fortuitously created a false nebula in combination with a computer mouse?