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A night of open clusters and double stars
On Tuesday 30th of August 2005 I got the 8-inch TAL 200K out around 20.30 hrs UT. The sky wasn't as clear as on the last two nights, but for observing some open clusters and a few double stars it would be OK. I also had a go at Mars and M77, and I did a little test comparing my two broadband filters, the Baader Skyglow and the Lumicon Deepsky filters. Are they of any use visually?


PART 1: OPEN CLUSTERS IN CASSIOPEIA
To warm up for a long night of observing I started with one of my favourite doubles, Eta Cassiopeiae, also known as Struve 60. The difference in colour and magnitude is just wonderful. The A component is a golden magnitude 3.4 star. At a position angle of 317º lies it's companion, a yellow-orange magnitude 7.5 star. The separation between both stars is about 12", an easy split even at lower magnifications.

After half an hour my eyes where adapted to the dark, and it was time to visit some open clusters in Cassiopeia, M 103 which a have observed a few times before, and a few "new" ones on my list, Trumpler 1, NGC 663 and NGC 654. As you can see on the map below, the four open clusters are all situated in the area between Delta and Epsilon Cassiopeiae. You can enlarge the map by clicking on the image.


image
Map from SkyTools 2 by CapellaSoft


M 103 (01h33.2m +60°42')
This small open cluster looks like a small triangle or Christmas tree. It is only 6' wide and its magnitude lies between 7 and 8. At a magnification of 133 I counted about 20 stars, at 200x about 30. What is clearly visible is that two of its brightest stars can be found at two of the apexes of the triangle. The star at the "top" of the Christmas tree is yellow white. The star at the southeast apex is bright white. Right at the centre of the cluster I detect a pair of stars that seem to be yellow and blue, but I'm not 100% sure about this one. Others report a 9th magnitude red star at the centre. I cannot find it but maybe my telescopes aperture is to small to detect colours of 9th magnitude stars.

Trumpler 1
Now this little gem really surprised me, and I immediately recognized it. I had seen it before, when looking for other objects in the area, but I failed to identify it. I had to use a little averted vision, but I definitely saw two rows of stars, running more or less parallel to each other in NW-SE direction. One row holds tree stars that are very easy to see from my backyard. Using a little averted vision, a fourth star comes into view, while the other row also shows itself with three stars. With averted vision at lest 10 other stars pop into view. Trumpler 1 has a diameter of 4.5' and its visual magnitude is 8.1. It is a detached, strongly concentrated cluster with a large range in brightness and poor richness in stars. Be sure to visit this little gem the next time your in the M 103 area!

NGC 663
My next stop was NGC 663. This 16' wide, magnitude 7.1 open cluster looks more or less elongated, with a beautiful double to the east of it's brightest star. At a magnification of 133x the cluster almost fills the field of view. The best view however as at 100x (20mm Vixen Lanthanum). I counted more than 30 stars, when using averted vision. It's brightest star shines at magnitude 8.4. This is the first time I observed NGC 663, but it won't be the last. I wasn't in the mood for sketching tonight so I will save that for the next time. The image below comes very close to what I saw through the eyepiece. Click on the image to enlarge. The limiting magnitude is 12, north is up and west is to the left.


image
Image from SkyTools 2 by CapellaSoft


NGC 654
About 0.75 degrees to the north-northwest of NGC 663 lies my last open cluster for tonight, NGC 654. This open cluster has a diameter of 5' and its visual magnitude is 6.5.
NGC 654 is a very delicate, small open cluster. It has a lot of stars that seem to be of an equal magnitude. At a magnification of 166x, the stars keep popping in and out of view, but when looking a bit longer using some averted vision I count 15 to 20 stars. At the south-south-eastern edge of the cluster lies a bright, magnitude 7 or 8 star. At 133x the cluster is at its best. It looks like somebody spilt some grains of salt over a black tablecloth. A wonderful view.

About 23.00 UT it was time for a coffee break, but first I wanted to give my two light-pollution filters a little test. After trying them on NGC 654, NGC 663 and Trumpler 1 the conclusion was very simple. The Baader Skyglow left the whole view intact, but didn't make the sky look any darker. The Lumicon deepsky filter definitely darkened the background but......... killed a lot of the faint stars in all three clusters, and coloured the brighter ones. Conclusion: visually these broadband filters are of no use for observing open clusters.


PART 2: DOUBLE STARS, MARS AND M77

At 0.30hrs UT I started with the second part of my observing night with a few double stars in Aries. If you look about 10º south of Triangulum you will see three stars in a more or less crooked row. These are Alpha, Beta and Gamma Arietis, the three brightest stars in the constellation of Aries. I included the map below to give you an idea where to find Aries. Note the position of M 45, the Pleiades. It might help you to locate the three bright stars. I selected four doubles for observing tonight: 1, Gamma, Lambda and Epsilon Arietis.


image
Map from SkyTools 2 by CapellaSoft


Gamma Arietis
I started with the brightest of the four doubles, Gamma Arietis. This is a magnitude 4.8 star, that I can see with my naked eyes from my backyard. With a small viewfinder it is easy to spot. What I immediately noticed that there seems to be no difference in colour or magnitude between the two components. Both shine in a white light and after verifying I found out that both stars are of exactly the same magnitude, 4.8. They are separated about 7.8" and the B component lies at a position angle of 0º. At 100x I really enjoyed these two celestial gems for a few minutes. Double stars are fun, even under light polluted skies!

1 Arietis
This is a close pair of stars, only 2.8" apart from each other. I could split them at 80x (hint) and 100x (sure), but the best view was at 166x. The brighter, magnitude 6.2 A component looks yellow while the magnitude 7.2 B component, lying at a position angle of 166º, looks white. 1 Arietis can be found 1.75º north-northwest of Beta Arietis. A very nice couple!

Lambda Arietis
To locate Lambda Arietis, just go northeast for a little more than 2º. Lambda is a very wide double, separated by 37.4". The A component is yellowish magnitude 4.9 star. The bluish magnitude 7.7 B component lies at a position angle of 46º. This double was at its best with the lowest possible magnification of 62x.

Epsilon Arietis
This double is a very though one. They are almost of equal magnitude (5.2 and 5.5) but only 1.5" apart from each other. Maybe the seeing had deteriorated in the last hour, because I was able to split 1 Arietis, which components lie 2.8" apart, but I was unable to split Epsilon, even at 400x. As you can see on the map above, Epsilon lies almost halfway between Aries and M45. I will have to wait for a more stable atmosphere before trying to split Epsilon Arietis.

Mars
Around 1.45 UT Mars was already high in the southeastern sky, together with the Pleiades. Because the seeing was getting worse I first didn't want to point the telescope at Mars, but on second thought I decided to give it a try. I was surprised! At 166x I definitely detected some darker areas on the rust coloured surface, and both poles looked white. Because Mars was jumping up and down due to the bad seeing, higher magnifications where not possible.

M 77
Around 2.15 UT (I was getting really tired) I decided to go for one last object, M 77 in Cetus. I had never seen it but tonight it was relatively high in the sky, and should be easy to spot. I could see the 4 or 5 stars that mark the tail of Cetus, so I had a go at it. As you can see on the image below, M 77 can be found 3 to 3.5 degrees south of Gamma Ceti, the second brightest star in the tail of Cetus. I didn't expect to see anything at lowest magnification, but I was in for a surprise again. I think that after M 31 this is the easiest galaxy for me to see. Using direct vision, it has a very bright core at 62x, even as bright as a star (9th magnitude) that lies to the east southeast of the galaxy. At 166x, using averted vision, the galaxy almost doubles in size, a round glowing disk with a very bright and large core. A great object to end my long night of observing at 2.40 UT. I can only come to the conclusion that even in a suburban area you can enjoy a long night of deepsky observing. You only have to choose the right objects!

Clear skies!


image
Map from SkyTools 2 by CapellaSoft
Posted by Math on 09/02 at 05:29 AM
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