White subgiant · Cepheus

Alderamin

Also known as: α Cephei (α Cep), HIP 105199

mag 2.549 light-years

About

Alderamin (α Cephei) is a white subgiant of magnitude 2.5 in Cepheus, about 49 light-years away.

Alderamin is in the constellation Cepheus.
Best evenings: around late September it is highest at about 9 pm (10 pm in summer time); a month earlier, two hours later.
Where on Earth: it is seen well, at least 10° up, from north of 17° S.

When it rises and sets tonight, how high it climbs and how much the Moon gets in the way are worked out in your browser for your place.

EyesEasy, even from town.
Binoculars (10×50)A sharp point; binoculars bring out its colour and the fainter stars around it.
Telescope (6–8 inch)Still a point of light at any magnification — stars are too far away to show a disc. Low in the sky, bright stars twinkle and flash colours.

Stars look the same in any instrument: brighter and sharper, but never bigger.

Proper name	Alderamin
Designation	α Cephei (α Cep)
Hipparcos number	HIP 105199
Type	White subgiant
Spectral type	A7IV-V
Colour	Yellowish whiteB−V colour index 0.26
Magnitude	2.5The smaller the number, the brighter.
Distance	49 light-yearsThe light you see left it around 1977.
Proper motion	0.16″ per year across the sky
Constellation	Cepheus
Right ascension (J2000)	21h 18m 34.7s
Declination (J2000)	+62° 35′ 08″