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public LocationGreenwich, UK
Sunrise: 4:58 
Transit: 13:04 
Sunset: 21:09
sunny   (Daytime)   What's Visible Now?
All Constellations »  Cassiopeia »  Deep Sky Objects » 

H21 - Open Cluster in Cassiopeia

Above the horizon.  Circumpolar today
Altitude: 69.8°   Azimuth: 312.9°   Direction: North-West

H21 is a Open Cluster in the Cassiopeia constellation. H21 is situated close to the northern celestial pole and, as such, it is visible for most part of the year from the northern hemisphere. Given its visual magnitude of 9, H21 is visible with the help of a binocular with a 60-70mm aperture or a small telescope.

The image below is a photograph of H21 from the Digitized Sky Survey 2 (DSS2 - see the credits section) taken in the red channel. The area of sky represented in the image is 0.5000x0.5000 degrees (30.00x30.00 arcmins).

Image of H21 - Open Cluster in Cassiopeia star
DSS2 image of H21 in the Red band. The green region on the image is a representation of the major (1.8 arcmin) and minor (1.8 arcmin) axes of the object's apparent size.

Apparent Coordinates

23h 55m 27s
+61° 52’ 35”

J2000 Coordinates

23h 54m 12s
+61° 44’ 24”

Finder Chart

The simplified sky charts below show the position of H21 in the sky. The first chart has a field of view of 60° while the second one has a field of view of 10°.

Finder chart H21 - Open Cluster in Cassiopeia star
Simplified finder chart for H21 - Open Cluster in Cassiopeia.

Finder chart H21 - Open Cluster in Cassiopeia star
Simplified finder chart for H21 - Open Cluster in Cassiopeia.

Photometric Information

The following table lists the magnitude of H21 in different bands of the electomagnetic spectrum (when available), from the B band (445nm wavelength, corresponding to the Blue color), to the V band ( 551nm wavelength, corresponding to Green/Yellow color), to the J, H, K bands (corresponding to 1220nm, 1630nm, 2190nm wavelengths respectively, which are colors not visible to the human eye).


For more information about photometry in astronomy, check the photometric system article on Wikipedia.

Apparent Size

The following table reports H21 apparent angular size. The green area displayed on top of the DSS2 image of H21 is a visual representation of it.
1.8 arcmin
1.8 arcmin

Rise and Set Times

Location: Greenwich, UK
Latitude: 51° 28’ 47” N
Longitude: 0° 00’ 00” E
Timezone: Europe/London

H21 - Open Cluster in Cassiopeia is circumpolar and transits at 04:28 UTC (altitude: 79.7°)