Last night I had a deepsky observing session at Elsenborn/Sourbrodt (Belgium). The visual magnitude was about 6.1. I used a Bresser 7x50 and the 8-inch TAL 200K Klevtzov-cassegrain. The eyepieces used were a 32mm Televue Plossl and a series of Vixen Lanthanum's ranging from 40mm to 7mm. Time 20.00 hrs to 23.30 hrs UT. No moon.
At 20.00 hrs UT I started of with M46, a beautiful open cluster in Puppis (the ship's stern). It was discovered in 1771 by Messier. The open cluster contains about 150 stars with magnitudes between 9 and 13. The total number of stars is estimated at 500+. Due to its visual magnitude of 6.1 it should have been visible with the naked eye, using averted vision. However, I did not detect it. In the 7 x 50 binoculars I could see M46 together with M47, a magnificent pair. They are both large and bright clusters. M46 is about 27' while M47 is 29' wide. The striking difference between M46 and M47 could be readily seen. M46 is a crowded cluster, the fainter of the two, while M47 is not so crowded, but beautiful because of its bright blue and white stars. A great binocular sight! In the Tal 200K at 166x about 70 to 90 stars could be detected. At 200x the planetary nebula, NGC 2438, could be easily seen. The disk is about 60". The 16th magnitude central star cannot be seen with the 200K. All in all, M46 proves to be a rewarding object to observe. It is one of my favourite open clusters.
After M46 I visited M48 in Hydra (the female watersnake), again an open cluster. For a long time it has been regarded as one of the missing Messier objects, because no cluster can be seen at the coordinates given by Messier. But because of Messier's description of the object it is almost certain that NGC 2548 is M48. There is a 4-degree error in the declination. Messier discovered the object in 1771.
M48 is easy to spot. It forms an equilateral triangle with "the Head" of Hydra and Procyon in Canis Minor. This was also an easy object for the 7x50 Bresser. M48 is a very large open cluster, 54' in diameter. It contains about 50 stars down to the 13th Magnitude. With my 200K, at the lowest possible magnification (62.5x with the 32mm Televue plossl) it didn't fit in the field of view (about 46.5 arc minutes). There are many stars that form nice couple's or triplet's in the field of view. A beautiful open cluster!
At 21.30 hrs UT I pointed the telescope at M51, the Whirlpool galaxy in Canes Venatici (the hunting dogs). M51 was discovered by Messier in October 1773. It was the first galaxy that showed a spiral form. Lord Rosse discovered the spiral form of M51 in 1845 with his 6 foot reflector at Parsonstown, Ireland. M51 is about 35 million light years distant. It has a major satellite galaxy, NGC 5195.
M51 forms a triangle with Eta Ursae Majoris (the end star in the handle of the Big Dipper) and 24 Canum Venaticorum. It lies in the northeast corner of a trapezoid of faint stars. I did not find it with my 7x50.In my 200K M51 and NGC 5195 looked like two concentrated halo's with a bright, star-like, centre. M51 was much appeared much larger than it's companion. I could not see any spiral structure. The "bridge" that visually connects the two galaxies was undetectable.
After M51 I took a quick look at M40, a mistake in the Messier list. At the position of M40 there is no nebula or cluster of any sort. There is just a close pair of stars of equal magnitude (9.0 and 9.3). It is very easy to find. It's just 1.5 degrees north east of Delta Ursae Majoris. Nice if you want to complete your own Messier observing list, but not an object to get exited about.
I closed the night with two beautiful globular clusters, M3 in Canis Venatici and M 13 in Hercules (the Strongman). Charles Messier discovered M3 in 1764. It is one of the three brightest globular clusters in the Northern hemisphere. Its visual magnitude is 5.9, it's brightest star about 12.7. The cluster has a diameter of 16'. It could be easily detected with the 7x50. M3 lies halfway between Arcturus in Boötes and 12 alpha Canum Venaticorum. In the Tal 200K at 166x it was a big and beautiful globular clusters with many stars resolved. It definitely rivals M13!
Halley discovered M13 in Hercules in 1714. It is very bright with a visual magnitude of 5.7. Its diameter is 17'. This globular is a naked-eye object. It can be easily found between 44 eta and 40 zeta Herculis. M13 lies 2.5 degrees south of eta. In my 7x50 Bresser it appeared as a sort of glowing cloud. In the Tal 200k it was spectacular. At 133x and 166x it looked like a glittering sphere of stars, the core very bright with many stars superimposed on a background glow. Many streamers of stars could be detected in different directions. A really beautiful object that deserves some observing time! At 23.00 hrs UT I ended a rewarding night of observing.