Solar Ephemeris for Kendal
- on Friday the 15th of December 2023:
- sunrise occurs 08:23
- sunset occurs 15:49
- Astronomical dark begins 18:01
- Astronomical dark ends 06:12 the next morning
Kendal Ephemerides for today are on our Welcome page
Moon Phase Chart
|Phase||December 2023||January 2024|
Winter Coloured Double Stars
Double stars can be very pretty, especially if the two stars have contrasting colours. Double stars have the advantage that they are little affected by light pollution or the phase of the Moon, unlike for example the faint fuzzy blobs of galaxies.
Splitting very close doubles can be an interesting challenge but you may be limited by the resolution of your optics. A very rough rule of thumb is that on an ideal night [do we get those in Cumbria?] your binoculars/telescope can resolve objects that have an angular separation of 140/aperture in mm [5.5/aperture in inches], so for a pair of 10×50 binoculars, you could separate stars if they are 140/50 ~ 3 arc seconds. I suspect 5 arc seconds might be a more likely possibility in this case.
Generally double stars with a colour difference are more interesting and beautiful to observe, especially if they are not too different in brightness. Having said that Castor, α Geminorum, is a pretty double with both stars being white and having a similar brightness.
One classic and rather lovely double star is Albireo in β Cygni – the head of the swan.
The picture above is one I took in September using my 8” Meade SCT and a Canon DSLR. The primary star is a lovely golden yellow at magnitude 3.4 whilst the companion at magnitude 4.7 is a lovely blue colour. They are just splitable using a x20 magnification.
The annotated right-hand picture defines a few of the numbers in the table below. North is up as seen in binoculars, but be careful here as different styles of telescope with give different orientations (never mind the effect of a star diagonal!). For example, a Newtonian, Dobsonian or refractor will give west to the left and north down, whilst a Schmitt-Cassegrain or a Maksutov will give North up and East to the right [as will a refractor and a diagonal).
So what do the labels mean? The separation is just the angular separation in arc seconds of the two stars, whilst the position angle is the angle of the line joining the two stars measured going in a direction through east – so can vary from 0° to 350°.
In the table below;
- are the positional coordinates RA (Right Ascension) and DEC (declination), the equivalent of latitude and longitude;
- the magnitudes of the two stars;
- the colour difference where the bigger the number, the more distinct the difference, determined from the spectral class [colour] of the stars;
- Finally, the optimum magnification based on the opinion of Alan Adler. He found that doubles look their best at a magnification that is approximately 750 divided by the separation in arcseconds. So, for Alberio, where the separation is 35”, 750/35= 21, so 21x magnification looks best. This is a rather subjective measure and don’t worry if you can’t get this ‘optimum’. For example, with my Meade, my minimum magnification is 77x and Alberio looks great!
Sometimes, the human brain plays tricks on you. Despite the temperature of a star, which fixes the colour and the spectral class, if the brighter star has a strong colour, you perceive the fainter star to have the complementary colour [for red that is cyan] rather than its true colour! You’ve probably seen this with an afterimage after looking at a bright coloured object. This is a nice website on this point .And different people see slightly different colours just to confuse things even more.
The following is a list of winter coloured double star systems worth looking at for their colours, based on a 2016 article in Sky and Telescope by Bob King1 – who based his article on an earlier one by Alan Adler2. You might need some planetarium software to find some of these pairs.
|Star||R.A. Dec.||Mags.||Sep.||P.A.||Colour difference||Spec. Class||Optimium magnification|
|η Cas||00h 49m||+57° 49′||3.5||7.2||13″||317°||1.7||G0, K7||58x|
|1 Ari||01h 50m||+22° 16′||5.9||7.2||2.9″||164°||3.5||K1, A6||268x|
|γ And||02h 04m||+42° 20′||2.1||4.8||9.8″||64°||3.5||K3, B8||77x|
|ι Tri = 6 Tri||02h 12m||+30° 18′||5.3||6.7||4″||69°||1||G5, F5||188x|
|η Per||02h 51m||+55° 54′||3.8||8.5||28″||301°||3||K3, A3||27x|
|32 Eri||03h 54m||–02° 57′||4.8||5.9||7″||254°||2.6||G8, A2||107x|
|ρ Ori||05h 13m||+02° 52′||4.6||8.5||7″||64°||1.7||K3, F7||107x|
|14 Aur||05h 15m||+32° 41′||5.0||7.4||15″||226°||0.4||A9, F3||50x|
|ι Ori||05h 35m||+05° 57′||2.9||7.0||10.9″||142°||0.2||O9, B1||69x|
|ι Cnc||08h 47m||+28° 46′||4.0||6.6||30.6″||307°||2.6||G8, A2||25x|
|ζ Lyr||18h 45m||+37° 36′||4.3||5.6||44″||150°||1.1||B7, A8||17x|
|Albireo||19h 31m||+27° 57′||3.4||4.7||35″||54°||3.5||K3, B8||21x|
|31 Cyg||20h 14m||+46° 44′||3.8||4.8||107″||325°||2.9||K2, B3||7x|
|β Cap||20h 21m||–14° 47′||3.2||6.1||207″||267°||3.2||K0, B8||4x|
|γ Del||20h 47m||+16° 07′||4.4||5.0||9″||267°||1.4||K1, F7||83x|
|δ Cep||22h 29m||+58° 25′||4.1||6.3||40.9″||191°||2.5||G2, B7||18x|
Some recommended highlights:
- Eta (η) Cas: Exquisite at 64× with a pale-yellow primary and purple-red secondary.
- Alberio β Cas: Lovely yellow primary and blue secondary but some people see yellow and white!
- 1 Ari: A close pair. Orange and blue – a good example of complementary colour.
- 14 Aur: Yellow and pale orange; subtle.
- η Per: Reddish-orange and blue-green. Another example of complementary colour.
- 32 Eri: Yellow-orange and blue. A close pair, so use 100× or higher to see the colours more clearly. Could be a challenge to find.
- Iota (ι) Ori: Two pure white suns. No colour difference, so no false contrast here!
- Gamma (γ) Lep: Striking gold and green! Of course, since there are no green stars, the complementary perception effect is at play here. Sadly, this is quite low, below Orion, but worth a try
I’ve only seen a few of these but I hope to see some more. I hope you can see some too.
What else to see?
We still have the fabulous Milky Way right over your heads and the asterism of the Summer Triangle consisting of Altair, Vega and Deneb still very prominent. This is a great time of year to see objects of interest in the constellations at the zenith: Cygnus, Lyra and Cassiopeia.
The most obvious star cluster is The Double Cluster (NGC 884/869) situated between Cassiopeia and Perseus. In addition, there is Caroline’s Rose, NGC7789, and M103 in Cassiopeia, M34 in Perseus, M29 and M39 in Cygnus for starters. The area is a joy to behold in binoculars on a dark night. There is the globular cluster M62, sometimes known as the Flickering Globular as it seems to change brightness – purely an optical illusion. For wide field imaging photographic targets, what could be better than M31, The Great Andromeda Galaxy and nearby telescopic M33. In addition, there is the North America Nebula complex, NGC7000, in Cygnus and the California Nebula, NGC1499. With a tracked 70mm lens you could capture both NCC7000 and the Pleiades, M45, in one shot.
Whilst on double stars, you must look at Albireo, b-Cygni. This is a beautiful low power telescopic object the brighter star golden and the dimmer one blue. See photograph later. Similarly, Almach in Andromeda is a pretty colourful double and not too far away, roughly half way between Almach and Cassiopeia, is the planetary nebula M76, The Little Dumbbell in Perseus.
In Perseus, we have another open cluster, M34, and nearby is Algol, the prototype for a class of eclipsing variable stars. Usually magnitude 2.1, it drops to 3.4 every 2.86 days – (2 days 20 hours 49 min), a rather noticeable change.
The two bright and large globular clusters M2 and M15, both about magnitude 6 and 12’ in diameter look good in binoculars or a small telescope. Orion is starting to become prominent in this general direction, but more on that later.The ‘wonderful variable star Mira’ as it is sometimes called, is well placed. (Mira in latin means wonderful). This pulsating red giant star changes brightness by over 6 magnitudes, from about 3 to less than 9, with a period of 332 days. hence changing from an easy naked eye star to invisible without optical aid. It is currently fading from a peak in mid-August and is expected to be around mag 6.5 in December. Try to see if you can measure its magnitude using just a pair of binoculars and your judgement.
The chart from the AAVSO shows various comparison stars visible to a binocular user. Judge where the brightness of Mira, the central cross, compares to the other labelled stars.
In the east,Orion is up around 19:00 and there is so much to see here – worth an article on its own! But will be much better a few hours later. The most obvious telescopic and binocular target is the Great Orion Nebula, M42, always a joy to look at. In nearby Taurus, there is The Pleiades, M45, which are easily seen as a fuzzy patch easily resolvable as stars in a pair of binoculars. This object makes a good widefield photo-op as well as a great telescopic image when misty gas becomes visible. You can also get both M45 and the California Nebula, NGC1499, using a 70mm focal length lens on a DSLR mounted on a tracker mount (i.e. Ioptron or Skywatcher Star Adventurer etc). A much more open cluster in Taurus is the vee of the Hyades with Aldebaran at one end. In addition, there is the Crab Nebula, M1, roughly midway between Capella and Betelgeuse. This fine supernova remnant, the result of the supernova recorded by Chinese astronomers in 1054, is a wonderful photographic object. If you have sufficient resolution, and image every few years, it is possible to see changes within the nebula – a great long-term project!
Scanning through Auriga with binoculars, the trio of Messier objects, M36, M37 and M38, will appear as faint misty clouds if you have a dark sky. Gemini is also now rather prominent too with white Castor above orange Pollux. The only really interesting binocular object is the open cluster M35. Rising about 19:00, there is another hazy naked eye object in the eastern sky – the open cluster M44 Praesepe or the Beehive cluster. A spectacular sight in binoculars. This will be much better by 23:00 when it will be 30° high.
In the west, Cygnus is still prominent for a few more weeks although Lyra is getting lower now but still worth a look. Look out for Delphinius, the Dolphin, as it [being fanciful] frantically tries to swim away from the horizon! The whole constellation neatly fits in the field of view of a standard pair of binoculars. The crowning glory of planetary nebulae, the Ring Nebula, M57, in Lyra is still a splendid fuzzy ring in a small telescope although is starting to get a bit low. Just 2° from Vega is The Double-Double, ε-Lyrae, a binary star in binoculars, but with a telescope each of these two stars is seen to be a double star itself. Of course, the other outstanding object must be the Dumbbell Nebula, M27, planetary nebula. Lovely in a telescope but not particularly well positioned now and by 21:00 mid-month it is probably too low.
Watch out for aurora across the northern region of sky. Ursa Major is not at its best for our map times but it provides a handy reference for north. Of interest is the double star of Mizar and Alcor, once regarded as a test of eyesight but I find fairly easy. Mizar is also a splendid double of unequal components. The separation of only 14.5” requires a telescope to split them. And the pointers, Dubhe and Merak tell you where to look to find Polaris. Finally, there is the binocular and telescopic galactic duet of M81 and M82, also known as Bodes Galaxy and the Cigar Galaxy respectively. M81 is a near face on spiral whilst M82 is edge on. However, M82 is undergoing massive star burst and colour photographs show a striking ‘jet’ of hot hydrogen streaming from the core. The duet makes a fantastic photographic composition. You’ll need long exposures and a focal length greater than 400mm to show it well.