Stephen Tonkin’s Binoc­u­lar Tour

This month, beau­ti­ful blue di­a­monds, a ride on a coaster and bird-spot­ting in Cas­siopeia

Sky at Night Magazine - - CONTENTS - STEPHEN TONKIN’S

Tick the box when you’ve seen each one

1 MELOTTE 20

Also known as Al­pha Per­sei Mov­ing Clus­ter, this is a stun­ningly beau­ti­ful binoc­u­lar tar­get, ex­tend­ing as it does for over 3°. It ex­tends nearly 4° south­east from mag. +1.8 Mir­phak (Al­pha (_) Per­sei). It is an as­so­ci­a­tion of mostly hot young blue (spec­tral types O and B) stars which, in binoc­u­lars, sparkle like di­a­monds on black vel­vet. Only about 60 mil­lion years old, the clus­ter is called ‘mov­ing’ be­cause all the stars share a sim­i­lar proper mo­tion (mo­tion rel­a­tive to the ce­les­tial sphere) of around 33 mil­liarc­sec­onds per year. Ĵ SEEN IT

2 BETA CAM

Beta (`) Camelopard­alis is vis­i­ble to the naked eye at mag. +4.0. Its mag. +7.4 com­pan­ion is a very easy split, even in small binoc­u­lars, 84 arc­sec­onds to the south­west, but this is not the main ap­peal of this star. Beta Cam is clas­si­fied as a yel­low su­per­giant, which is rel­a­tively young at 40 mil­lion years old and in tran­si­tion be­tween be­ing a hot new blue star and a red su­per­giant. Enig­mat­i­cally, it has been seen to brighten by a whole mag­ni­tude in a flash with a du­ra­tion of sec­ond, pos­si­bly its equiv­a­lent of huge so­lar flares. Ĵ SEEN IT

3 STOCK 23

If you pan slightly more than 1 ° due west from mag­ni­tude +4.3 CS Camelopard­alis, you will find an un­re­mark­able lit­tle trapez­ium of 7th and 8th mag­ni­tude stars. This is Stock 23, also known as Pazmino’s Clus­ter. With 50mm binoc­u­lars you can see this is much more than a trapez­ium and you may be able to re­solve about half a dozen stars against a faintly glow­ing patch of sky about 10 ar­cmin­utes in di­am­e­ter. Ĵ SEEN IT

4 ED­DIE’S COASTER

One of the ‘binoc­u­lar clas­sics’, Ed­die’s Coaster is an as­ter­ism that is not eas­ily ap­par­ent in star charts or pho­tographs, but is very ob­vi­ous in 10x50 binoc­u­lars. To find it, look 3° north of Gamma (a) Cas­siopeiae, where you will find a 3°-long wave of 7th and 8th mag­ni­tude stars, rem­i­nis­cent of a roller­coaster, hence its name. Ĵ SEEN IT

5 THE CAS­SIOPEIA TRIPLE CLUS­TER

Look 1˚ to the left (east) of the mid­dle of an imag­i­nary line join­ing Se­gin (Ep­silon (¡) Cas­siopeiae) and Ruch­bah (Delta (b) Cas­siopeiae) and you will eas­ily find the largest and rich­est of these clus­ters, NGC 663. The four bright­est stars ap­pear to be sep­a­rated into pairs by a dark lane. Just shy of 1˚ to the north-north­west is the brighter but smaller NGC 654. The poor­est of the trio is NGC 659, a tiny ghostly glow which may need averted vi­sion, just on the NGC 663 side of the mag. +5.8 star 44 Cas. Ĵ SEEN IT

6 THE OWL CLUS­TER

Us­ing Ruch­bah as your jump­ing-off point, iden­tify mag. +4.3 Mar­fak-East (Theta (e) Cas­siopeiae) and nav­i­gate 2° to­wards it, where you’ll find an easy dou­ble star with its com­po­nents shin­ing at mag. +5.0 and +7.0, sep­a­rated by 135 arc­sec­onds. These are the owl’s eyes. Its body and wings are com­posed of 9th and 10th mag­ni­tude stars that span an area about ° in the di­rec­tion of Gamma Cas. The brighter eye, Phi (q) Cas­siopeiae, is not ac­tu­ally part of the clus­ter: it lies just over half way from us to NGC 457, which is nearly 8,000 lightyears dis­tant. Ĵ SEEN IT

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