Wednesday 17 November 2010

California here we come

This is a little bit of the California nebula (NGC 1499) taken with the autoguided 20" scope. I combined 6 x 90 second exposures. It makes sense in theory to get as long exposures as possible, because it's not just a case of taking more shorter exposures. With the longer exposures, there is less noise, because a large part of the noise is from reading the sensor. The problem we have is rotation, which limits the exposure time until you see stars forming short trailed arcs at a distance from the guide star. Therefore, we can only do long exposures in the East or West. Had my camera been modified for astronomy, this picture would be full of bright red nebula.
As it is, it is pink, but still lovely.

NGC 1501

Little close up of the best few 30 second subexposures of this quirky green ring living up in the faint northern constellation, Camelopardalis. The camel-leopard is a giraffe, of course. I processed it with patience in Registax, which is great at sharpening, but doesn't seem to be able to rotate and stack, nor stack dark frames. So I cropped it.

Galaxy hiding behind star

This is Mirach, in Andromeda, blazing away as a bright, 2nd magnitude star, 200 light years away from us. In the same line of sight, absolutely unconnected, lies NGC 404, a faint 10th magnitude galaxy that is rather hidden in the glare of Mirach. The galaxy is many millions of light years away, but the smudge we see is only 1500th as bright as the star, and that light is spread out so as to make it yet harder to see. This picture is exposed and processed so the difference is nowhere near that great. Good things, digital images!

NGC 6905

Here’s a little planetary nebula in Delphinus. Another one of my ‘unusual’ objects, not in the sense that it’s difficult to photograph, but not many people would think of photographing it. It was visible as a little ring in the 20” and I could just see the central star. Wow! There are two brighter arcs to the west and east (top left and bottom right in this orientation) and there are faint extensions (ansae) to the north and south, that show up better on longer exposure photos.

The Fireworks galaxy (NGC 6946 in Cepheus)

In this little Catherine wheel of a galaxy there have been lots of supernovae, hence the title. It makes us wonder why there aren’t as many in our own Galaxy, the Milky Way. But we realise we are IN our galaxy, and it is full of DUST. I use the word full loosely. The dust blocks our view of the majority of our galaxy, and so we’re unlikely to have seen all the supernovae that have gone off in the last few hundred years. So come on, Betelgeuse or rho Cassiopeiae, give us a nice show soon.

Stefan’s Quintet (Pegasus)

This little galaxy group is a challenge to see in most amateur telescopes. However, I have seen all 5 galaxies in our 20” scope. It’s rather trailed as it was taken before the auto-guiding camera was used on the big scope. Also it was high in the sky so the scope had to spin rather quickly to keep track of it. Consequently, there is some rotation, which appears to pivot around the star at the top. This is a sign that the computer did not quite know exactly what position the telescope was in. Looking at this group makes me wonder how our own local group would look from a planet there. It would be a patch of dim smudges in a large telescope, dominated by Andromeda, the Milky Way and M33, rather further apart.

Hartley 2

Here is a picture of the Comet Hartley 2 from 10th October (not very current). Perhaps it should be renamed Harley 2, because of its ability to move during the time it takes for its picture to be taken. The green colour comes mostly from the molecule C2. Hmm... I wonder what that smells like. I tried to process to give the most coma and tail, but probably have included some optical artefacts due to not using a flat field correction to the image.

Wednesday 3 November 2010

I (also) see 405... and it is VERY interesting.

Disclaimer: apologies 'littlebeck'... I couldn't resist posting this first. I'm in a rare mood for blogging, and I thought this picture couldn't wait any longer for its submission into the blogosphere. For the reader, we were both attendant at the ultimate test of the 20"'s guiding using an STV camera - a 5 minute exposure on an alt-az scope, and this pic didn't actually come from my Canon EOS 350D. I was impatiently waiting to test my own camera and its focal-reducing adapter before imminent cloud arrival (see IC410 post). Here is my stack of the 5 good 5 minute shots of IC405. This is such a wierd looking patch of sky, and in this instance the Canon's lack of red sensitivity has enhanced the colour contrast between the different parts of the nebula. The nebula is otherwise known as the Flaming Star Nebula, and this is just the centre surrounding the 6th magnitude star in the shot (the faintest star you can see, unaided). This star was the guide star and was responsible for the STV units loud beeps as it corrected the telescope's position. (P.S. I'm currently listening to Radiohead: Everything In Its Right Place and reading too much meaning into song lyrics).
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