M33 – Pinwheel Galaxy

Subject: M33 - Triangulum (Pinwheel) Galaxy
Telescope: Celestron CPC 800 with f/6.3 reducer
Camera: Canon Rebel T1i
Technique: 55 approximately 30 second lights at 800 ISO. Total exposure time of 29 minutes 20 seconds. 8 darks. 50 biases.
Prime focus. Stacked with Deep Sky Stacker. Post-processing in Photoshop.

This image was a bit of a gamble for me. My previous stacks were of higher ISO lights in the range of 1600 to 6400 ISO. Because of the way higher ISO images are taken, they basically increase the gain of each pixel. This results in brighter images at the cost of more noise. For my particular camera, there is a threshold at about 800 ISO where any increase does not add to the amount of photons detected, but simply starts to blow out the image in order to make it brighter. Tonight I tried keeping all of my lights at a low ISO and relied on my post-processing abilities to bring the image out. Fortunately, it all worked out well and I am happy with the result.

At approximately 2,723,000 light years away, the Triangulum (or Pinwheel) galaxy is one of the furthest objects from Earth that can still be visible to the naked eye in great conditions. It is about 50,000 light years across making it the third largest galaxy in our home group behind the Andromeda and Milky Way galaxies. It gets its name due to the fact that it is located inside the Triangulum constellation and is sometimes referred to as the Pinwheel galaxy due to its shape.

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