Category: Deepsky log

in the same field of view of the 7x50. They are separated 3 degrees from each other. In the 15x80 only both the cluster cores fit in the 3.5 degree field of view. NGC 6633 has a diameter of 27’ and a visual magnitude of 4.6. In the 15x80 I see a bright star north-northwest of the cluster. I see some 20 to 25 stars of almost the same brightness in the direction northeast-southwest. In the centre of the cluster I can see a triangle of stars.

IC 4756 is much larger. Its diameter is 52’ and its visual magnitude is 4.6.  Through the 15x80 it seems be lie within a trapezium of brighter stars. I can see about 30 to 35 stars but there is also a glow of unresolved stars.

The map below should give you an idea of what you see through a 7 x 50 binocular (North is up. East is to the left). The limiting magnitude is about 9 to 9.5 and the big red circle represent a field of view of 6.1°. IC 4756 is on the left and NGC 6633 is on the right.

Credit and © Capella Soft, “SkyTools2”

M 39
Next on the list was M 39 in Cygnus. This open cluster has a diameter of 31’ and its visual magnitude is 4.6. It is very easy to spot. From Deneb, go about 9 degrees in east-northeastern direction, and you will see the triangular shape of M 39 immediately. In the centre of the triangle I could see a yellowish star. It is a very poor cluster. I counted only 12 to 15 stars.

M 31
From M 39 I turned to Andromeda, to find M 31. Through big binoculars you see the real size of M31. This galaxy is a binocular object! When I move the mirror from the Sky Window up and down, I really see the full size of 3 degrees. M 110 is also clearly visible as a small elongated smudge of light. M 32 is invisible. I could not detect any structure or details in M 31.

Double Cluster / Stock 2
This area is wonderful for observing with binoculars. With the 15x80 Stock 2 is an impressive sight. Its stars form the figure of a man with its arms and legs spread. You will recognize this asterism immediately, using big binoculars. Stock 2 is a large open cluster with a diameter of 1 degree. It is connected to the double cluster in Perseus by a 2 degree arc of stars that runs in the north-south direction. The double cluster looks stunning through any telescope or big binocular, even through the 15x80. The “western” cluster, NGC 869 is also called h Persei, the “eastern” cluster, NGC 884, is called Chi Persei. Both clusters have a diameter of 30’, the size of the full moon.

Interesting is that each of the double cluster components have a true diameter of 65 light-years, while Stock 2 has a true diameter of 18 light-years. But why does Stock 2 look much bigger than the components of the double cluster? That’s because of the different distances they lie away from us. The double cluster lies at a distance of 7200 to 7500 light years, while Stock 2 lies relatively nearby at a distance of 1050 light years. This area is interesting enough to revisit many times, with any kind of optical aid.

Alpha Persei moving cluster (Melotte 20 or Per OB3)
This is a deepsky object for 7x50 binoculars. The 3.5 degree wide open cluster is too big to fit into the 15x80. The small binoculars leave some room around Melotte 20, so it stands out very well from it’s surroundings. In the centre of the field of view I counted 30 to 35 stars. The age of the Alpha Persei moving cluster is estimated at 50 million years. It is thought that the Alpha Persei cluster is one of oldest Gould Belt objects, together with the Pleiades. The Gould Belt is a remnant ring of bright stars, star forming regions and remains of molecular clouds that is tilted about 20 degrees to the galactic plane.

NGC 7789
This big open cluster in Cassiopeia looks like a really bright patch of light through the 15x80. NGC 7789 has a diameter of 25’ and a visual magnitude of 6.7. I could not detect any stars or granulation. The brightest star has a visual magnitude of 10.7. With the 10-inch Skywatcher and a Zeiss zoom-eyepiece, NGC 7789 looked stunning. The whole field of view was filled with maybe 80 stars of equal brightness. At moments like these you wish that you had a 400-inch telescope) Together with NGC 457 and Stock 2, NGC 7789 forms my favorite trio of star clusters in Cassiopeia.

NGC 752 (Collinder 33) and the Golf Putter
About 4 degrees south-southwest of the beautiful double star Gamma Andromedae lies another great binocular cluster, NGC 752. Together with an asterism called “the golf putter”, NGC 752 forms a great couple for observing with big binoculars. The golf putter can be is formed by a chain of bright stars that run from the northwest to the southeast. Three stars in the southeast form the end of the chain. To the east of the asterism lies NGC 752, which could be seen as the golf ball. In the 15x80 the 1.5 degree golf putter and NGC 752 look fantastic.

M 33
We ended the night with M 33 in Triangulum. With the Skywindow and the 15x80 binoculars, M33 is very easy to find. From Beta Andromedae move your binoculars to the south in the direction of the western tip of Triangulum. Keep looking very carefully if you see a really big smudge of light while moving south. Even in a light polluted sky M 33 is very easy to spot using binoculars. It is 67’x41’ in diameter. With the 15x80 I estimated its size around 30’. It is however impossible to see any structure or details in M 33 with binoculars from our light polluted backyard. This object again proves that some galaxies are great objects for binoculars.

both components showed no hint of being doubles themselves. At 80x (25mm) they started to look like they both where doubles. At 133x they where both clearly split and at 200x they looked like two close couples of stars, aligned perpendicular to each other (see image below. North is up and west is to the left. At the top you see Eta Lyra 1 with the A (the brighter lower one of the two) and the B component. At the bottom of the image you see Eta Lyra 2 with the C (the brighter one to the left) component and the D component.

Image from Skytools2 by Capellasoft

The AB pair is separated by 2.6”, the A component has a (visual magnitude) vM 5.4, the B component is of vM 6.5. The position angle is 357 degrees. The CD pair is separated by 2.3”, the C component has a vM of 5.1, the D component 5.3. The position angle is 94 degrees. All four stars seem to have the same colour, white. They are all spectral types A.

Vega (Alpha Lyrae)
This beautiful white-bluish star is the fifth brightest star in the sky, and the third brightest to be seen in our mid-northern latitudes. The five brightest stars are:

1. Sirius -1.46
2. Canopus - 0,72
3. Rigel Kent - 0.27
4. Arcturus - 0.04
5. Vega 0.03

Vega is a multiple star system (3) but I could not detect one of the two faint companions.

Zeta Lyrae
Zeta Lyrae forms a triangle with Vega and the Double-Double. It is a beautiful double star with two bright yellow-white components (vM 4.3 and 5.9), separated by 44”. A great couple for any telescope or big binocular. According to James Kaler the A component is a hydrogen-fusing dwarf and it’s companion, the D component, is a class F “subgiant”.

Delta Lyrae
The next stop is Delta Lyrae and the open cluster Stephenson 1. Delta Lyrae is a very wide pair, which is already split in the finder scope. The magnitude 4.5 Delta Lyrae 2 is separated about 10’ from the 5.6 Delta Lyrae 1.  Delta Lyrae 2 looks orange while Delta Lyrae 1 has a white-bluish colour. Between and around these two stars I can detect a group of 10 stars that probably belong to the open cluster Stephenson 1.

Beta Lyrae
I end my short trip along some doubles in Lyrae with Beta Lyrae. This again is a stunning pair with a bright 3.4 A component and a 8.9 B component as its companion at a position angle of 149 degrees. This close couple is only separated by 46”. Lyrae has some really great doubles for telescopes and binoculars. Earlier this year I observed almost the same stars with the 15 x 80 binoculars, but these beautiful doubles are great for all instruments! The light polluted sky does not affect these beauties too much.

in an arc of 6 stars. Once you know to locate this group, it is very easy to identify the Garnet star.

Mu Cephei in an arc of stars. Map generated with SkyTools2 by Capellasoft

This is the very first time I see the Garnet Star through my big binoculars and it looks really impressive, with its bright deep orange glow.

M 52
Next on the list was M 52. To find M 52, I started at Alpha Cassiopeiae. From there I went in a straight line to Beta Cassiopeiae, and extended the line with the same distance Alpha-Beta. With direct vision there is not much to see, just a hint of a small patch of light. With averted vision, M 52 turns into a hazy path of light, with a triangular form, very easy to see with the 15 x 80. There are 1 or two stars visible. The rest of the cluster just looks like a small nebula.

NGC 7789
M 52 has a magnitude of 6.9 and its diameter is 12’ Another bright cluster in Cassiopeia, NGC 7789 has a magnitude 6.7 but it’s diameter is a bit arbitrary when you read different publications and sources about this beautiful cluster. Most publications state that its diameter is 16’. If you compare both magnitudes and sizes of these two clusters, they should look almost the same through the 15x80 big binoculars, but they don’t! NGC 7789 looks not only a bit brighter, but much larger than M 52. After looking through some recently bought books, I noticed that according to Archinal and Hynes (Starclusters) and Crossen and Rhemann (Sky Vistas) the diameter of NGC 7789 is 25’. I think this is much closer to what you really see, than the 16’ I find in most sources on the Internet. I go for 25’.

You can find NG 7789 by starting at Beta Cassiopeiae. From there you move your binoculars into south-south-western direction for about 3.5 degrees where you will spot the bright cluster immediately. Through the 15x80 I could not resolve NGC 7789. It remained a bright hazy patch of light, though sometimes you (think?) you see a hint of granulation. NGC 7789 is made up of hundreds of stars, but no stars shines brighter than mag 10.7. Under light polluted skies my 15 x 80 never showed any stars dimmer than mag. 9.5 to 10. Anyway, it’s one of my favourites!

NGC 457 (Caldwell 13)
An even more impressive cluster for big binoculars is NGC 457. This cluster lies 2 degrees to the south-southeast of Delta Cassiopeiae. The cluster looks like a “stick man” (or as ET according to other observers). When you look at NGC 457 through the 15 x 80’s, you immediately see the two “bright eyes”, as well as the main “bar” of a body, the arms and feet. The cluster’s diameter is about 20’ (Archinal and Hynes). It’s visual magnitude about 6.4, a great sight through both binoculars as well as through a telescope.

Stock 2
From NGC 457 it’s only a short “trip” to Stock 2, a big open cluster, 1 degree in diameter, that lies between Epsilon Cassiopeiae and the famous Double Cluster in Perseus. Stock 2 looks even more like a “stick man” than NGC 457. The body, arms and legs are very easy to see. In the 15 x 80 you can even see some kind of oval head. You can see about 50 to 70 stars in big binoculars. Stock 2, NGC 457 and NGC 7789 are definitely my favourite clusters in Cassiopeia!

The Double Cluster in Perseus (Caldwell 14)
From Stock 2 it’s again a short hop to the famous Double Cluster in Perseus, NGC 884 and NGC 869. There are no words to describe the beauty of these two clusters through big binoculars or a rich field telescope. This is the first, or one of the first objects I saw through a telescope, almost 30 years ago, and it still is one of my favourites, which I visit on every possible occasion. Both clusters are about 30’ in diameter (as large as a full Moon), and they are separated only by 0.5 degrees. Both clusters are already well resolved, and to me they look like two boxes of jewels in the night sky. As I said earlier, I cannot find the words to describe the beauty of these two great open clusters, so go out and take a look for yourself. It will become one of your favourites too!

With the Double Cluster I ended my observing session for tonight. I used the 15 x 80 and the Sky Window for all my observing tonight. I located the objects with the help of the SkyAtlas 2000 and a printed map of the Mu Cephei area.