Derby and District Astronomical Society

Messier 40 (Winnecke 4)

Double Star in Ursa Major      RA 12h 22m 24s  Dec +58d 05m 00s

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Adrian Brown captured this image of M40 on the 3rd April 2006. It was taken using a Skywatcher 80ED refractor at f7.5, an ATIK ATK16HR camera and a Celestron CGE mount. Astronomik RGB and CLS filters were also used. The total exposure times for each RGB filter were red 20 minutes, green 20 minutes and blue 20 minutes, with 5 minute sub-exposure times used. M40 is actually the double star in the centre of the image, the only Messier object that is not a nebula, galaxy or star cluster. In 1660 the astronomer Johannes Hevelius recorded a nebula at this position. Charles Messier observed only the double star but nevertheless recorded it in his catalogue. The stars have almost equal magnitudes of 9.0 and 9.3. The bright yellowish field star above right of M40 in the two o'clock position is 70 Ursae Majoris (you may have to scroll to see the whole image). The 13th magnitude barred spiral galaxy NGC 4290 is visible some distance above M40 between the twelve and one o'clock positions. The nucleus of this galaxy has a stellar appearance. However it is most certainly the case that this galaxy was not the nebula that Hevelius recorded. The galaxy NGC 4284 is also just visible above NGC 4290 and forms a triangle with two faint stars.



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