Saturday, 29 August 2009

Obscure Nebula - looking deeper

We had compared our images of Gyulbudaghian's Variable Nebula (HH 215, GM 1-29) and neither of us could see anything definate. It was the last deep-sky night for a fortnight as the moon was setting at 11pm as a distorted deep orange almond sinking behind the horizon. So, I was inspired to take another good bunch of 30" pics. All in all, I stacked 46 (including the previous pictures - below) to get a total exposure of over 25 minutes at f/4.8 on the 20" telescope. Here is the result. This picture is improved enough for you to see the Herbig-Haro jet HH 415 and the background nebulosity is clearer. HH 415 can be found by going below and slightly left of the bright blue star right of centre to find a bright-looking 13th magnitude star. There is a very faint star just below this and the object is the small streaky blur just below that. As for the main object around PV Cephei (just below centre), I still can't really see much there. With this picture, I increased the saturation, as it had somehow dropped during processing. So now the colours of the stars are revealed and they are stunning! This is especially useful on PV Cephei, which is clearly revealed to be a dim red colour, sitting in its dark patch of nebulous dust. Who knows what magnitude it's at now!?

Saturday, 22 August 2009

The Helix Nebula

Contrary to what I've seen written, the Helix nebula is not the closest planetary nebula to us. It is one of my favourite objects but it is quite elusive, as it can only been seen at certain times under good conditions from UK and I had a good window of opportunity the other night. I took several shots, about 60 in all I think, 45 of which were good enough to stack (22x30",22x15" + 1'). The main trouble is that the nebula is so diffuse, it was barely visible on the individual pictures because of LIGHT POLLUTION! The worst culprits round here seem to be rural industry and carelessly aimed, wasteful and unnecessary security lights. So, to combat this, I stuck in a 40mm eyepiece on the 20" (60x) with a Lumicon UHC filter screwed on and the detail in the helix's structure was amazing and the centre of the nebula was filled in with a cool blue glow. I've done a lot of careful processing on the final image, as the flat fields were not as flat as I'd have liked (I took them on a white door indoors). It still looks quite noisy I think, but it's a beautiful object that I've been waiting a long while to photograph this well.

Gyulbudaghian's Variable Nebula

In this picture of Gyulbudaghian's nebula, North is down. It was ~ 8 mins worth of exposure on the 20" scope nearly overhead (5x1' + 6x30" + 17"). The nebula, which was discovered to be variable in 1977, has been very, very faint recently. The white lines point to the star PV Cephei, which is also faint. If you compare it to a previous image you will wonder what has happened to it... Strange star! (image courtesy STSci)

Friday, 7 August 2009

M19, the elongated globular cluster

Just a quick post to keep the blog ticking over. M19... A curiously elongated globular. One of my sharper images on the 20", but still a but fuzzy. I had to play around with the colour, as Deep Sky Stacker decided to give the midtones a green tinge when it stacked the pics. If I remember right, this was about 10 x 15 second shots on the 20", when it was tracking well, with darks and a flat. As far as globulars go this one is very close to and slightly further away than the centre of the galaxy, and we're looking at it through a plethora of distant stars and a bit of dust. It's an impressively big and bright cluster and it can be seen in binoculars at magnitude 6.8 in the constellation Ophiuchus. But why is it elongated? My instinct tells me it's tidal forces from the centre of the galaxy, but that's pure speculation.