Wednesday, 28 July 2010

27.7.2010 - In the Twilight zone

Telescopes: 8" Orion DSE
Obs. place: Koivukylä, Vantaa, Finland
Date: 27./28.7.2010
NE Lim.mag: ~4.5 (south)
SQM-L reading: 17.25 (south)
Background sky: 1
Seeing: 6-7
Transparency: 2
Weather: Nautical twilight. +22.0 - 19.0°C, humidity 82 - 91%, 1016 HPa, calm, NCLs in the northern sky, 97% moon in Aquarius, heat lightnings (2.45 am ->) above the sea to the south. Mosquitoes!

Apart from the furious heat (I'm build for a cooler climate and I have a dense chest hair), twilight and a bunch angry mosquitoes the session was quite enjoyable. The few hours earlier cleaned primary mirror showed sharp images and no collimation related issues came up - never have since the primary mirror is basically stuck. The biggest problem was the heat. I had to have proper clothes to fend off the mosquitoes so naturally I was sweating like a turkey at Thanksgiving (and I feel bad for the turkey!). Noctilucent clouds were visible for the duration of the entire session between midnight and 3 am. Heat lightnings were also spotted low in the southern sky a bit before 3 am. Naked eye limiting magnitude was around 4.5 with the SQM-L meter showing readings between 15.95 and 17.30. Apart from the abysmal background sky, high humidity and really poor transparency seeing was quite good. I couldn't detect nearly any twinkling of stars at the eyepiece or with the naked eye.

So what to watch? After a few bright objects to check out the sky quality (namely M11 and IC 4665) I decided to settle in with only the brightest objects as I suspected from the beginning. If there is a single object I remember seeing as one of the very first in the season, that would be NGC 6910. The cluster didn't disappoint this season either. "Familiar Y-shape obvious even at 38x. Two 7th magnitude stars are in the NE edge. The cluster is quite enchanting but only 5' in size. 15* visible." I decided not to rotate the sketch as usual (north up, east left) so the Y-shape of the group is far more obvious.

NGC 6910 with 8" Orion DSE @ 80x

There was another bright object in Cygnus that was actually on my to sketch-list. This is NGC 6871. I found the position of the cluster quickly but could only spot two double stars reminding me of VdB 1 in Cassiopeia. I had to go back inside and get a map to be sure. Turns out my memory was right on spot but the cluster wasn't. Apart from the two doubles and a slight curve of stars following I couldn't really see anything cluster like in the area. With some imagination and probably luck too I sketched the field and the cluster as I experienced it. It wasn't much but at least I saw and drew the right object. 27 Cygni is the bright star NE.

NGC 6871 with 8" Orion DSE @ 60x

And then again I couldn't go on without starting my Messier object logbook. There was M29 and M39 and I went after the latter. I sketched the cluster to my logbook as well as to a card. I tried to put on some effort on the description for a change and wrote to my notebook: "At 38x a triangular group with four bright 7th magnitude stars. Fairly well detached from the background and without a doubt partly due to the poor observing conditions and twilight. All of the stars appear white in poor transparency with roughly 30* visible. The brightest star in the middle of the group. No obvious double stars. At 80x the cluster has lost its beauty. No additional detail seen. The cluster fills the field of view - size ~40'.

Messier 39 with 8" Orion DSE @ 38x

I left Cygnus behind and with quite a maneuver: I moved the telescope long way nearly directly to east and directly to NGC 7209. This feat surely is something to tell the grandchildren about (at least until they comprehend the term luck). The open cluster showed a few dozen stars in a lovely U-shaped pattern leaving a little "cave" in the middle. I couldn't see the haunting drunken lizard that I've seen more times I care to admit.

NGC 7209 with 8" Orion DSE @ 60x

At around 2 am, just after finishing up the NGC 7209 sketch, the noctilucent clouds had brightened up to fairly bright so I had no choice but to interrupt the session and ride the bicycle to a nearby field and take a few pictures. Sadly I couldn't escape the annoying street lights but at least the NCLs show up in the image well enough:

When I got back it was 2.45 am and had to be up in less than 6 hours but I wanted to go for one more. North of 7209 is another fine open cluster in the little Lacerta. The shape is curious and years ago in my star-drunk stupor called the cluster "The Whip of Indiana Jones". So, I might have watched one of the movies a few weeks before but still, even today, the shape is quite obvious to me. I've also seen a beer tankard in the eastern section of the cluster. Whatever you see, I've always thought of the object as quite tormented. What makes it very curious to my eye is that the cluster is divided into four different concentrations of stars. Oh, and if you've read that the cluster might be nothing more than an asterism or an open cluster with only a handful of members.... that's not exactly true. In the 2008 paper "Memberships and CM Diagrams of the Open Cluster NGC 7243" by E.G. Jilinski et al. the authors found 211 cluster members down to 15.5 magnitude.

NGC 7243 with 8" Orion DSE @ 48x

I'm not a big planet buff and I've actually watched Jupiter perhaps 20 times during my 12 years of observing. Tonight I decided to make an exception and try if I could see something with the good seeing and all. I was worth it. I'm not sure what one should see from Jupiter but I clearly saw 4 cloud bands, the Jovian moons and a faint stars just south of Jupiter's disk and it looked like a 5th moon. The star turned out to be a 8th magnitude HD 965. So with all the excitement at the eyepiece, Jupiter will earn another look in the future.