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Messier 3 - another shot at ccd imaging this globular cluster

This is my latest picture of Messier 3. I took a few hundred images of 6 seconds each using Nebulosity with my Macbook Pro in the garden. On top of my Celestron NexStar 5SE telescope was a dew cap, which does make a lot of difference it turns out. The Lumicon deep sky filter was also in place (just before the zenith prism). All images were taken with the Meade DSI II pro ccd camera. From time to time I hand adjusted the NexStar to center the globular cluster M3 in the ccd. I don’t autoguide (yet). The NexStar 5SE isn’t equipped to use an autoguider, though I’m sure it would be possible to hack together some sort of autoguiding system. In fact, I wouldn’t be surprised if the electronics are identical to the NexStar 6SE which does have an autoguider port. But enough about that.

Inside, I handpicked the best pictures, which left me with 266 frames to stack in Nebulosity. I subtracted with a bad pixel map and aligned all the pictures using Translation + Rotation + Scale while saving each file instead of a stack. I love this technique, because I can then preview all the aligned pictures and toss out the ones that are slightly mis-aligned, or blurry. I find it easier to decide when I see all the pictures aligned. I then stacked the remaining frames using None (fixed) and did some post processing with curves and levels. I sharpened the image using Sharpen. I find Sharpen and Laplacian sharpen filter nicer for globular clusters than Tighten star edges.

Of course it took me at least 6 hours in total (imaging and post processing) to create the above picture. Which brings me to the limits of image quality. I created a similar photo of M3 months ago, and that photo was of much less quality. There is of course a sharp limit in terms of image resolution, based on the diameter of the main mirror of the NexStar 5SE, which is five inches. Maybe the above picture is hitting that limit. But the light pollution and the camera quality – which could easily be blamed for lesser quality pictures by a novice – certainly aren’t the true limits of taking beautiful pictures. By taking enough pictures and taking the time to read the manual of Nebulosity (and trying out several techniques), it seems to me that the picture quality to a certain degree is a function of the amount of time spent. Or should we say, the lack of boredom 🙂

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  1. […] we have Messier 3 again. Not as good as this attempt from a while back, but then again, I was kinda tired this evening so I didn’t take too many exposures. This is […]

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