M101 - The Pinwheel Galaxy in Ursa Major

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M101, the Pinwheel Galaxy, in LRGB.

Location: Ballauer Observatory in Azle, Texas

Seeing: 8/10 (1.4 FWHM)

Transparency: 4/10

Date and Time: December 29, 2003 @ 11:00PM

Equipment: Tak FSQ-106 @ f/5, and Celestron CGE mount

Camera: SBIG ST-7E with CFW-8a color filter wheel, standard SBIG filters

Exposure Info: LRGB image (L = 5 x 10 minutes, R = 3 x 5 minutes, G = 3 x 5 minutes, B = 5 x 5 minutes) all binned 1x1

Processing Information: Dark frames, gradient removal, registration, Sigma combine and DDP in MaxIm 3.0. Levels, Curves, Gaussian Blur and Unsharp Mask in Photoshop 7.

Exposure Notes: Composite images were taken low in the sky in too much light pollution. Although this shot has 105 minutes of total exposure time, the size of the galaxy should fill the frame from top to bottom. Need much more exposure time in like conditions.

About this Object

M101 forms a perfect equilateral triangle with the last two bright stars in the handle of the big dipper. This makes this spiral galaxy easy to find, but not necessarily easy to see. Though the picture doesn't show it, M101 is actually very large in apparent size, nearly 30 square arc minutes. Therefore, the magnitude of this object is spread over a large surface area. For this reason, dark skies and bigger apertures are necessary to bring out the spiral structure, though the entire galaxy is also visible in a good small scope, even in binoculars. One more interesting thing about this object: this is a duplicate object in the Messier catalogue. Not only is it the 101st object, but also the 102nd. This is why we say there are only 109 Messier objects, even though the last one is numbered M110.

🤖 AI-drafted · unverified

What it is: M101 is more commonly cataloged as the Pinwheel Galaxy (the name "Whirlpool" is usually reserved for the similarly-shaped M51). It is a grand-design face-on spiral.
Constellation: Ursa Major
Distance: ~21 million light-years
Apparent magnitude: 7.9
Angular size: ~28.8 × 26.9 arcminutes
Coordinates: RA 14h 03m 13s, Dec +54° 20′ 56″

This summary was generated by an AI assistant from general astronomical references, not from Jay's own notes on this specific image. Treat every detail above as a starting point for research, not settled fact.