Daily Archives: June 30, 2005

Mac Astro Software

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I’m not happy with the state of astronomical image-processing software on the Mac. I’ve been using Keith’s Image Stacker for the past few days, and while it’s better than nothing, it’s not better by much. So far it has crashed several times, and in one case managed to remove all trace of work in progress (in fact, trying to save the work in progress triggered the crash). The interface is not well thought out, and it doesn’t protect you from silly errors. In trying to remove one frame from a stack I wound up removing all frames – there’s no fail-safe asking whether you’re sure you want to wipe out all your work….

iCCD and iAstronomy looked as though they might be worthwhile, but iCCD doesn’t support digital SLR cameras, and iAstronomy doesn’t support Canon 20Ds (supposedly the author is working on it, but he hasn’t responded to my queries)July 3 – Steve Bryson responded, more later. I’ll be looking at PC software shortly, turning to the Dark Side if I must.

Cheating

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The cloud gods have been having a conversation over the observatory, so I’m still playing with the M57 captures from last week. There’s a small 14th magnitude (14.8 – but that’s integrated rather than surface brightness, and so not seen at the same time as 14th magnitude stars) spiral galaxy [IC1296] close to the Ring. You can see it in this link[hmm, seems to be broken now]. Knowing that the galaxy is present — i.e., cheating — with a lot of processing and a certain amount of wishful thinking you can see the core of the galaxy in this image (roll your mouse over the image to see the equivalent normal image):

M57 area showing supposed galaxy

It’s just a dot in the image, so not directly identifiable as a spiral galaxy. It’s much fainter – to the point of being a smudge not much better than variation due to noise in the normal image.

Can’t see it? You have to believe! [And if the mouse rollover does nothing for you, you need a newer browser...]

This started out as a stack of 7 10-second images with a common dark frame removed. Some of the stars which are definitely there are as low as magnitude 15.3, and the central star of M57 is clearly present at magnitude 15.2. There’s still a lot of noise – the images were captured at ISO1600 using an uncooled Canon 20D in 30 degree Celsius conditions (and lots of mosquitoes!). Some stars I expected to see were not found, or are dimmer than expected. I’m not sure if I processed them out of the image or if there was a problem with colour sensitivity. The visual magnitude limit at the time was 2 or 2 1/2, and the sky was a nasty reddish brown from the sky glow. Removing the sky glow has compromised the colour, but if the haze ever goes away I will try again with longer exposures in an attempt to capture the colour properly. Unfortunately weekend predictions are for clear skies with poor transparency.