What is ngc 663?

NGC 663 is a Open Cluster in the Cassiopeia constellation. NGC 663 is situated close to the northern celestial pole and, as such, it is visible for most part of the year from the northern hemisphere.

The following table lists the magnitude of NGC 663 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.

The image below is a photograph of NGC 663 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 0.5x0.5 degrees (30x30 arcmins).

Celestial coordinates for the J2000 equinox of NGC 663 are provided in the following table:

The simplified sky charts below show the position of NGC 663 in the sky. The first chart has a field of view of 60° while the second one has a field of view of 10°.

The 2MASS point source catalog (Cutri et al. 2003) provides a uniformly calibrated database of the entire sky in the near-infrared J, H, and Ks bands with a 10σ detection limit of 15.8, 15.1, and 14.3 mag, respectively. Kinematic information can be obtained to secure the membership in a star cluster by the PPMXL data set, which is derived from an all-sky merged catalog based on the USNO-B1 and 2MASS positions of 900 million stars and galaxies, reaching a limiting V ∼ 20 mag (Röser et al. 2010). The typical error of PMs is less than 2 mas per year for the brightest stars with Tycho-2 (Høg et al. 2000) observations and is more than 10 mas year−1 at the faint limit. However, Röser et al. (2010) noted that about 90 million (10%) objects of PPMXL include spurious entries; they found double or several matches of USNO-B1 stars with a 2MASS star. Kharchenko et al. (2012) have averaged such PMs and computed their errors in sky areas with star clusters including NGC 663. Therefore, we use these PMs instead of PPMXL data.