NGC 7331 is a spiral galaxy in the constellation of Pegasus. It is 50 million light years away and was once said to look like the Milky Way. But the Milky Way is now believed to be a barred spiral like M109. It is, however, very unusual in that the core rotates the opposite way to the disc. How this came about is obscure. It has been selected by the "HST Extragalactic Distance Scale Key Project" as a secondary standard for extra-galactic distances being calibrated by Cepheid variables. Its distance is 49 million light years which makes it 30,000 light years across.
There is a particularly good colour picture of this galaxy in the APOD for 12th August 2011.
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I've not had a great deal of success with this galaxy, and this is my first half-decent image, and my first attempt in colour. The galaxy is surrounded in the sky by smaller galaxies and one of them shows in this picture but I have been unable to find a designation for it. Date and Time: 18th August 2011 23:55 to 00:33 UT Camera: MX716 Telescope: LX200 with 0.33 focal reducer and Astronomik CLS and RGB filters Capture: star_mx7. 60 seconds exposure, 10 frames for CLS, and 6 frames for RGB. Processing: star_mx7. Dark subtraction, non-linear stretch 25, background. Registax. Stacked all frames for each filter. The three resulting pictures were then combined with the LRGB technique. |
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I was not very happy with the image above so I tried again five weeks later. This is a monochrome image taken through a simple CLS filter. It is a sharper picture, and the above picture failed to pick up the colour that larger telescopes can see. Date and Time: 29th September 2011 21:31 to 21:36 UT Camera: MX716 Telescope: LX200 with 0.33 focal reducer and Astronomik CLS filter Capture: star_mx7. 60 seconds exposure, 10 frames. Processing: star_mx7. Dark subtraction, non-linear stretch 25, background. Registax6. Stacked all frames. Gaussian wavelets Scheme 1. |
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