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Sunday, September 05, 2010


Comet 103P/Hartley via GRAS

Left image: 120 second image taken with GRAS 05, clear filter. Right image: Stack of 4 120 sec images.

So it's been pelting down with rain here. In Australia, when a drought breaks, it BREAKS. With with all the flooding, people hit by lightning, not to mention the 70 Km/hr winds removing the garden furniture, astronomy is off the menu, so to speak. Even the Global rent-a-scope facility up north has been hit by really bad weather.

However, the global rent-a-scope network has scopes over in New Mexico, USA. So while the Australian network is under cloud, now was a good time to try and see if I could image 103P/Hartley. The great thing about the US scopes is that it's deep night over there while it's daytime here, so I don't have to wait up until the wee hours for the comet to rise.

I imaged the comet using the medium deep scope GRAS-05. I went for 120 second exposures because of my previous experience with the scopes. I took 4 concurrent exposures. For the images above I took the pre-calibrated files the system sends back. The first is a single file with brightness and contrast adjusted using ImageJ. In the second, I manually aligned the comet images in ImageJ (using the translate function, a right pain let me tell you), then added them with the image calculator function, then messed around a little with the contrast.

The result isn't too bad, the stacked image shows a decent coma and little tail. People aren't getting much better structure with longer exposures and more stacking. Here's a false colour animation I made from those 4 images (the bright objects to the right and below are hot pixel artefacts I can't get rid of). I'll certainly be keeping a remote eye on this comet as it evolves.


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