Month: July 2022

This image is from 18 5-minute exposures. With luck, I’ll get some more tonight and sharpen it up a bit.

Edit: As promised, here’s the same image with additional exposures:

The single exposures aren’t bad on their own. However, the noise in the image is terrible:

(The electronics in the image sensor caused the odd artifact along the upper right edge.)

For your convenience, here are a couple of 100% crops of the single vs. combined images.

Single exposure:

Note the many tiny bright blue dots. These are defects in the image; pixels that fired inappropriately. There are many other fine grain flaws, but the blue dots stand out.

…with 65 sub-exposures:

The blue dots are gone.

When I started this hobby I thought the purpose of multiple exposures was to make dim objects brighter. But it isn’t — the goal, the magic sauce, is noise reduction. With many exposures, the errors cancel out, and a clearer view of the underlying reality emerges. We hope.

In the single exposure above, the inaccuracies of the individual sensor elements give a gritty character, as if the image was a sand painting made with somewhat impure sand. The image that results from combining the 65 sub-exposures has much less of that gritty appearance.

NGC7635, the “Bubble Nebula”, is towards the lower left, and M2 is the open cluster along the upper right side.

The Hubble has, as usual, produced a lovely rendition of the Bubble — I guess we could call it the “Hubble Bubble“.

On a different note, the New Space Telescope has dropped its first images, and they are spectacular, as expected. Ditch astrophotographers such as myself tremble in awe. Several side-by-side comparisons of HST and NST images show wonderful improvements in clarity and detail. Stephan’s Quintet has special significance to me because it is the most difficult object I ever saw visually, back many years ago when my eyes were better and I had a 10″ Dobsonian. It was only discernable with averted vision, but definitely there.

However, the Hubble images are still as exquisite as they ever were. The universe has wonders at every scale — it is a fractal of wonder. The Hubble reveals wonders at its scale. The New Space Telescope reveals wonders at a different scale. And My Little Telescope (MLT) reveals wonders at its scale.