M31 with a Meade DSI Pro II – redux

Okay, temptation overtook me again . I pulled out the IR blocking filter and took an hour’s worth of images, plus enough calibration frames that I should have been able to eliminate the flaws in the previous images. The results, below, are better, but there are a few nagging issues.

[G2:41283 class=g2image_centered exactsize=800]

This time, with the IR blocking filter, the bloated stars are mostly gone. What’s left is probably due to crappy optics of the 50mm finder. The calibration frames have also fully removed the dust shadows. I didn’t think about it the first time around, but my source for the flat frames is an electroluminescent panel which doesn’t put out much (any?) IR, so the flats may not have really been illuminating the focal plane the way the image was.

What’s left that’s annoying is those little bright squiggles. They look to me like hot pixels that are not being fully removed by the dark frames. I’m not sure how, but I’m not sure what else to blame them on. The final image (above) is from 120 30-second exposures. The mount, an AstroTrac TT320X-AG, was unguided and the images slowly drifted during the hour long sequence. So, after aligning them, anything fixed in the focal plane, like a hot pixel, would appear to drift.

I used Maxim DL to process the images, and there is a way to build a map of bad pixels which is will then remove and fill in from surrounding pixels, but there is nothing obvious in the dark frames that would warant marking these bad. I guess I’m going to have to look a lot closer at them….

Still, not a bad image considering the equipment. I will add that I’ve concluded that using the AstroTrac for this is unnecessarily painful. I really need to get my Losmandy GM-8 back together. The issue is that the small field of view makes it very hard to get pointed at what you want and to frame it well.