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Contains:  NGC 4290, The star 70UMa
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M40 (Winnecke 4), NGC 4290, PGC 39934, 


            Jerry Macon
M40 (Winnecke 4), NGC 4290, PGC 39934
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M40 (Winnecke 4), NGC 4290, PGC 39934

Technical card

Dates:May 19, 2020May 20, 2020

Astrodon Gen 2 L 36mm: 16x120" (gain: 99.00) bin 1x1
Astrodon Gen 2 RGB 36mm: 61x120" (gain: 99.00) -12C bin 1x1

Integration: 2.6 hours

Avg. Moon age: 27.01 days

Avg. Moon phase: 7.21%

Bortle Dark-Sky Scale: 4.00

Temperature: 8.00

Basic astrometry details job: 3560582

RA center: 12h 21' 38"

DEC center: +58° 0' 46"

Pixel scale: 0.443 arcsec/pixel

Orientation: 88.574 degrees

Field radius: 0.261 degrees

Resolution: 3432x2484

Locations: Dark Star Observatory, Taos, New Mexico, United States

Data source: Own remote observatory

Remote source: Non-commercial independent facility


An unusual entry within the Messier catalog is Messier 40 (M40), also known as Winnecke 4 (WNC 4), is an optical double star located in the constellation Ursa Major, the Great Bear (the lower pair).

M40 lies at a distance of 510 light years from Earth. It is one of the few Messier objects that are not deep sky objects, but were catalogued by mistake. It was not listed in the New General Catalogue (NGC).

Messier 40 is composed of a G0-type star and an F8-type star with apparent magnitudes of 9.65 and 10.10. The stars are separated by 52.8 arc seconds and form an optical pair, lying along the same line of sight, but not physically connected to each other as they are known to be at different distances from Earth. The brighter component (G0) is designated as HD 238107 and the fainter (F8), HD 238108. The more distant component lies more than 1,900 light years away.

Winnecke 4 was discovered by Charles Messier on October 24, 1764. Messier was looking for a nebula reported in the area by the Polish astronomer Johannes Hevelius in the 17th century, but did not find one, so he catalogued the double star instead. The “nebula” reported by Hevelius may have been the 12th magnitude barred spiral/early type ring galaxy NGC 4290 (visiable at top of image directly above M40), which may have been visible in large telescopes at the time, but not in those Messier used.

A small 17.4 magnitude spiral galaxy PGC 39934 is located just below NGC 4290. It measures only 0.7'x0.2'.



Jerry Macon
License: Attribution Creative Commons

Sky plot

Sky plot


M40 (Winnecke 4), NGC 4290, PGC 39934, 


            Jerry Macon