The Flickr Messier40 Image Generatr

Sometimes I find there are nothing like as many stars to see as other times.

Take this picture which includes M40, a pair of bright stars that Charles Messier thought was a double star. It is in Ursa Major (or the Plough, near to Megrez the star that connects the handle to the plough).

The stars form an optical pair, lying along the same line of sight, but not physically connected to each other as they are now known to be at different distances from Earth. One is about 470 light years away and the other is over 1000.

Messier was trying to identify nebulae but at that time it was hard to distinguish between galaxies and nebulae. This one of the few objects that made it into his catalogue that were neither.

What he missed were two spiral galaxies that my C11 picked up near to M40. The larger one just under the word Major is NGC 4290 and the much fainter one below that is PGC 39934.

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Telescope: Celestron C11-A XLT Schmidt Cassegrain OTA
Mount: SkyWatcher EQ6-R Pro

Controller: ZWO ASIAIR Plus 256G
Main Camera: ZWO ASI533MC Pro at -10C
Filter: ZWO UV/IR cut filter
Focuser: ZWO EAF
Guide Camera: ZWO ASI174MM Mini guidecam
Guide via: ZWO OAG

Stacked from:
Lights 12 at 120 seconds, gain 101, temp -10C
Darks 30 at 120 seconds, gain 101, temp -10C
Flat 30 at 430ms, gain 101, temp -10C
Dark Flat 30 at 430ms gain 101 temp -10C

Bortle 4 sky.
Integrated the saved frames in Astro Pixel Processor.
Processed in PixInsight
Added captions in Photoshop CS4

Messier 40 (also known as M40, Winnecke 4 or WNC 4) is a double star consisting of two unrelated stars in the constellation Ursa Major. We had a little spare time after the target we were shooting set behind trees so we slewed the scope over to Winnecke 4 for a quick and easy shot and another Messier object to tick off the list. Double stars are extremely common in the Universe so the inclusion of this one in the Messier catalogue was a mistake.

WNC 4 was discovered by Charles Messier in 1764 while he was searching for a nebula that had been reported in the area by Johannes Hevelius. Not seeing any nebulae, Messier catalogued this double star instead. It was subsequently rediscovered by Friedrich August Theodor Winnecke in 1863, and included in the Winnecke Catalogue of Double Stars as number 4. The American astronomer Robert Burnham Jr. called M40 "one of the few real mistakes in the Messier catalog [sic]," faulting Messier for including it when all he saw was a double star, not a nebula of any sort. Amusingly, within about 16 arcminutes East of M40 are 2 galaxies discovered by William Herschel 25 years later and would have been classed as nebulae at the time. Herschel also discovered the 3 galaxies North of M40.

I measured the separation between the two stars to be approximately 52 arcseconds. In 2016, parallax measurements from the Gaia satellite showed that the two stars involved (HD 238107 and HD 238108) are unrelated, confirming previous suggestions by astronomers Brian Skiff and Richard L. Nugent. As measured by Gaia, the two stars are 1142 light years and 456.6 light years distant, so one is over twice as far as the other.

The galaxies in this image are, from left to right: NGC 4362, NGC 4358, NGC 4335, NGC 4290, NGC 4284.

010 x 300 second exposures at Unity Gain (139) cooled to -20°C
050 x dark frames
020 x flat frames
100 x bias frames (subtracted from flat frames)
Binning 1x1
Total integration time = 50 minutes

Captured with APT
Guided with PHD2
Processed in Nebulosity and Photoshop

Equipment:
Telescope: Sky-Watcher Explorer-150PDS
Mount: Skywatcher EQ5
Guide Scope: Orion 50mm Mini
Guiding Camera: ZWO ASI120MC
Imaging Camera: ZWO ASI1600MC Pro
Baader Mark-III MPCC Coma Corrector
Light pollution filter

Messier 40 is one of the objects in Messier's catalogue that are considered mistakes. The number 40 is wide spaced double star (most likely just an apparent double), and it's hard to imagine why it's in the Messier's catalogue of comet-like objects. Also listed as Winnecke 4.

LRGB, 6x5min each