Observing with Outstanding Transparency

[samgray1]

Date/time: Thursday, August 18, 2011 (2100 - 2315)

Conditions: At Cleveland National Forest, Pine Creek Trailhead (Old Highway 80 & Pine Valley-Las Bancas Road, Descanso, California) (elevation 3600 feet). The skies there are Bortle Dark-Sky Scale class 4 (green). Transparency was 5/5, seeing was 3/5, temperature was a nice comfortable 65 dropping to 60 degrees Fahrenheit, and the wind was calm. The sky was clear and there was no dew. By the charts, the moon rose at 2155, but I couldn’t directly see it until about 2300 because of the local hills.

Observations: Taking advantage of the fact that my wife is away visiting family in Scotland and a favorable weather forecast, I decided to get in a short observing session at my favorite dark-sky spot. Due to necessary after-work chores I got away from the house a bit late, so it was already very dark when I arrived. I checked my collimation and found it to be close enough to perfect that it wasn’t worth adjusting. Since I was racing against time (moon rising soon), I took advantage of this lucky break and got right down to observing.

I tried to check M3, but it was already behind a tree, so I went on to M5.

M5 looked like a cotton ball with stars dotted all around it (very nice). It was nice at 107X, but wanting to check to see what magnifications the seeing would support; I went up to 300X, which was pretty good when moments of clarity came and then settled at 200X as the best level of magnification.

M51 in Ursa Major was measured with my Telrad as about 3 degrees west of Alkaid on a line drawn going straight for Cor Caroli. Using M51’s companion (NGC 5195) as a reference by calling it 12 o’clock, there was a star at 5 o’clock in the swirls and another star at 9 o’clock. From what I could see, the star at 9 o’clock (near where supernova 2011dh was) was outside the swirls. On a previous night at this location under similar conditions I saw the supernova inside the farthest-out arm/swirl, so I think the supernova has now dimmed to the point of blending in and the star I saw at 9 o’clock was a normal star (marked on a picture I saw as 134, magnitude 13.4). The center of the galaxy was bright, then there was a dim part, and then the swirls became brighter again. The swirls ended about ¾ of the way to the star at 9 o’clock. I couldn’t see the bridge between NGC 5195 and M51.

M10 and M12 in Ophiuchus made a nice pair of globular clusters to compare and contrast. I noted that M10 was brighter and rounder than M12. It looked like it had a splatter of bright stars in front of the core. I used 107X magnification to go back and forth between the two. M12 did have a dense core as well, but was not as bright and the stars around it were not as evenly distributed as those in the outskirts of M10.

M13 in Hercules was beautiful (as usual) and at 107X the individual stars resolved really well. On this one I decided to try it at 300X and was really happy I did. The increased magnification brought the background light down to almost black, leaving me with a highly contrasted beautiful globe of bright stars against a nice dark background. The seeing was good enough that I could resolve most of the stars in the core and most of my FOV was filled with this beauty!

M57 (Ring Nebula) was another good one. Since its location is so easy, I just went straight to it using my Telrad and found it right away, still at 300X. It was really bright and beautiful, bright enough that the ring appeared to be light green. The center was obviously not black; it was easy to tell that it was brighter than the sky surrounding the nebula. I couldn’t see the center star though, even with averted vision. Since this target was so bright, I didn’t even try the UHC filter on it.

M27 was also as bright as I had ever seen it. I noticed for the first time that it is actually slightly oblong, and is wider in the directions of the dimmer sides than it is on the brighter sides. I compared the views with and without the UHC filter and found that the UHC brought out a little more detail. I used my 14mm (107X) for this and the rest of my viewing for the night.

At this point in the night I noticed that it was getting lighter and found that although the moon was still behind a hill from my vantage point, it had started shining on the face of a hill to my southwest. I decided I had to skip a few things on my over-ambitious list of things to see and went on to Sagittarius next.

M8 (Lagoon Nebula) was outstanding! I saw more nebulosity in it than ever before (UHC filter still on). Before I had always seen the bright nebulosity on one side and the star cluster on the other side with little to no nebulosity, but this time I could see nebulosity around the star cluster too. I noted that there was a U shape that was not illuminated. Inside the U was the brightest part of the nebula and outside the U was the dimmer part of the nebula that contained the star cluster. The bottom of the U was pointing north.

M20 (Trifid Nebula) (UHC filter still on) was nice. I noted that there were two stars close together in the center of the bright part of the nebula, where the dark lanes join together. There was also another two bright stars spaced farther apart in the dark lane that was pointing straight north. I removed the UHC filter for a second and noted that I could still detect the nebulosity outside the U, but just barely; if I had not seen it with the UHC filter on first, I would not have noticed it. I think the UHC filter is helping me learn to “see” better when I am not using it.

M17 (Swan Nebula) (UHC filter still on) was beautiful and I could see more of it than ever before. Normally I only see the bright swan shape, but this time I noticed that the nebulosity below (north of) the swan and behind (east of) the swan – although it was much dimmer, was actually much larger than the swan shape itself. It was beautiful and green with the UHC filter on, but was basically white without it.

M16 (Eagle Nebula) (with the UHC filter in) also showed more nebulosity then I had ever seen in this nebula before. The nebulosity east of the cluster was easy to see with the UHC filter in, but almost indistinguishable without it. While I had the UHC out, I noted that there is a nice little fan-shaped asterism in there too.

I was going for M11 (Wild Duck Cluster) next, when I got hit in the face with a flashlight… no, it was the moon that had just come over the crest of the hill to my northeast, but it seemed more like the headlight of a car shining in my eyes. I was standing there feeling like a vampire that had got caught in the sun as more and more of the noon became visible when I remembered that I had to work the next day, so I just took a quick look at M6 and M7 with my binoculars and packed it up and drove home.

This night taught me something important: I now know that 5 out of 5 transparency under Bortle class 4 (green) skies easily beats 3 out of 5 transparency under Bortle class 3 (blue) skies. I saw more this night than I have ever seen out at our local club’s dark-sky site (Tierra Del Sol Dark-sky Observing Site). By the way, I’ll be heading out to TDS on Saturday night. I really enjoy discussing astronomy and sharing views with the folks there.

[sxinias]

Congratulations on a great night of viewing. I enjoyed your report. Wish that I were there.

[killersheep]

Wow sounds like an amazing night of viewing!

[reborn]

Wow great report. Ive been a casual observer for about 5 years and this report has prompted me to start an observers log. I can see the benefit of writing my observations down or maybe recording them. Thanks

[xphile]

Awesome report. Thanks!

[Cladinator]

Thanks for an outstanding report, Sam. That sounds like an awesome night of observing.
Shoot us another report when you can. I'm looking forward to reading more.

[samgray1]

Wow great report. Ive been a casual observer for about 5 years and this report has prompted me to start an observers log. I can see the benefit of writing my observations down or maybe recording them. Thanks

Thanks everyone.

Yes, I keep a report file using MS-Word for myself. Now that I have started posting reports on this forum, I have changed the flavor of my reports a little to be better for posting and they are fine for my own records too. It does help to be able to read and recall what your prior observations were.

[Joe Lalumia]

GREAT REPORT! thank you for taking the time to post it up.

Clear skies.

[j.gardavsky]

Hello Sam,

thanks for your excellent report.

Best

JG