Binoc­u­lar tour

If Jan­uary does bring rain, as least you can get an ex­quis­ite view of the Orion Neb­ula

Sky at Night Magazine - - THE SKY GUIDE - With Stephen Tonkin

Tick the box when you’ve seen each one

1 COLLINDER 70

10x Our first ob­ject this month is Collinder 70, 50 the clus­ter that nearly ev­ery­body has seen and yet al­most no­body recog­nises: it’s the clus­ter that in­cludes the belt stars of Orion. On a clear night, you should be able to see 70-80 stars, some form­ing beau­ti­ful curv­ing chains, in this mag­nif­i­cent oval clus­ter. They’re mostly blue-white stars, with a few yel­low ones here and there. They form lots of pairs and some beau­ti­ful curved chains, in par­tic­u­lar the S-shaped chain of brighter stars that weaves its way be­tween Al­nilam (Ep­silon (¡) Ori­o­nis) and Min­taka (Delta Ori­o­nis). SEEN IT

2 SIGMA ORI­O­NIS

10x Sigma Ori­o­nis is vis­i­ble to the naked 50 eye as a mag. +3.8 star about 1º to the south­east of mag. +1.9 Al­ni­tak (Zeta Ori­o­nis), the east­ern­most star of Orion’s Belt. It is in fact a mul­ti­ple star con­sist­ing of five com­po­nents, four of which can be seen visu­ally. You should eas­ily be able to split it into two com­po­nents

with 10 50 binoc­u­lars and see the blue star that is 43 arc­sec­onds from the white pri­mary, but you will need dou­ble the mag­ni­fi­ca­tion to re­solve the next two com­po­nents. SEEN IT

3 THE ORION NEB­ULA

10x The Orion Neb­ula, M42, is a high­light of 50 the win­ter skies and a su­perb ob­ject in binoc­u­lars of any size. It’s vis­i­ble to the naked eye as the cen­tral star of Orion’s sword. Al­though it’s bright enough to be vis­i­ble in quite poor con­di­tions, it’s sen­si­tive to sky trans­parency and is usu­ally best ob­served af­ter rain has cleaned the sky of dust, when you should eas­ily make out the ‘fish’s mouth’ and the ‘wings’. M42 ben­e­fits from pa­tience; the longer you look at it, the more de­tail you’ll be able to see. SEEN IT

4 HIND’S CRIM­SON STAR

15x Hind’s Crim­son Star, or R Le­poris, is the 70 red­dest star in the heav­ens. It’s a Mi­ratype vari­able with a pe­riod of 457 days, and is near its max­i­mum, so should be eas­ily vis­i­ble

5 GAMMA LE­PORIS

10x Gamma Le­poris is vis­i­ble to the naked 50 eye at mag. +3.6. This is a dou­ble star, with the fainter (mag. +6.1) com­po­nent an easy split in binoc­u­lars, be­ing just over 1.5 ar­cmin­utes to the north. This pair of stars is only 29 lightyears away and the pri­mary three times as bright as the Sun. The fainter com­pan­ion, AK Le­poris, is more in­ter­est­ing from an astro­phys­i­cal point of view: it’s a BY Dra­con­istype of vari­able star, the mag­ni­tude of which varies with a pe­riod of about 17 days as star spots ro­tate across its sur­face. SEEN IT

6 M41

10x M41 is 4° south of Sir­ius (Al­pha (_) Ca­nis 50 Ma­joris). This open clus­ter is bright enough to be vis­i­ble to the naked eye in a trans­par­ent sky, and has been known since an­tiq­uity. It’s large enough to be an ob­vi­ous clus­ter of stars in 10 50 binoc­u­lars. From a ru­ral site, you should be able to re­solve up to 10 brighter stars against the back­ground glow of fainter stars if you use averted vi­sion. If the sky is clear enough, you may be able to de­tect that the stars dif­fer in colour, with the bright­est one, near the cen­tre, be­ing yel­low­ish. SEEN IT

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