Monthly Archives: November 2009

Oops! One small step forward, a big step back.

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I’ve upgraded my camera from a Canon 40D to a Canon 7D, having been seduced by the many improvements in the camera ergonomics and much touted additional capabilities. There was a little sticker shock in the upgrade – cameras are pricey!

With the upgrade I have moved deep into a world of over-sampling, where the individual pixels are smaller than the theoretical smallest size of a single point of light in an image. In a seeming paradox, that smallest size is independent of the diameter of the telescope, and is entirely determined by the f-ratio of the scope. My largest scope is f/10, and in order to match the scope to the chip, I should reduce the f-ratio below about f/6.8. There are focal reducers to do that, but I’ll pass on them for the moment – I can’t afford them so soon after the upgrade.

I knew about the diffraction limit going in and took it into account when I made my decision to buy. What I did not appreciate was the difficulty of converting the RAW image produced by the camera into a usable TIFF or even JPEG image needed for processing and display. It seems every new camera requires a radical change in the way RAW images are stored. The manufacturer’s conversions are adequate for terrestrial images, but for astronomical work they (or a more detailed tuned version) must be incorporated into the astronomical image processors. That’s a big ‘Oops!’ because it means that for some time to come I will be limited in how I process my image captures, and when the imaging software does get upgraded I may have to wait a while to save up for a purchase. Sometimes these kinds of upgrades are standalone, and sometimes they get bundled up with other software upgrades. In the first case there is usually no more than a nominal charge, but in the second the cost can be substantial. Ugh! Could be a further sticker shock in my future.

Oof! Stayed up too late!

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For some reason my diurnal rhythm is way off, and I’ve been getting to sleep around 5 am or so and then I’ve been getting up around 8 or 9. That’s a bad thing for anyone to do, but it’s stupid for a diabetic as it generally leads to trouble balancing blood sugar. I’m paying or it now, because for the first time in a while the weather is actually cooperating, and it’s both clear and dark – but unfortunately I’m too tired to do much imaging. To make it worse I have a new 7D which just has to see first light.

I pointed it at Orion, set the focal length to 24 mm, aperture to f/6.3, and fired off 10 8-second shots at ISO 6400. I can’t process them the way I would like (the camera is too new to be supported by my favourite software), and I still have to create some darks, but I have to say I like the results.

For a quick view, I duplicated one image as a new layer, then ran a Gaussian blur over that layer to get a rough cut at a sky gradient, set it to a 50% fill, and then took the difference between the layers to get an image with most of the light pollution gradient gone. It’s not great, but it’s good enough for first light.

While I took a series of 10 shots, I haven’t processed the full series into one image yet. The entire constellation of Orion will be covered. Here’s a close crop from one frame of the image series, processed as described above. This is just the region around M42, and is definitely not a deep image:

Close crop of wide angle Orion image

I’ll post the full Orion image when it’s processed, though I’m not sure if I will link to the original size image or just a reduced version – it’ll be huge at the original size.

LATER: I’m having trouble processing the images – not enough cache space left on my main drive, and the external drives are too slow – but I now perceive some trailing. Back to the drawing board….