Globulars Great and Small

Observing Report - 5/6 July 2003

by Joe Fragola

LocationCoyote Lake Park, Gilroy, CA
Date/Time5 July 2003 21:46 - 6 June 2003 3:15 PDT (6 July 2003 04:46 - 10:15 UT)
Sky ConditionsClear, limiting magnitude approx. 6.2 22% Moon in SW sky; set at 12:30 a.m. PDT
EquipmentOrion XT10 Dobsonian

I had been waivering about heading out to Coyote Lake Park since returning home from a great Italian dinner with the family. The posted “observing intentions” on the TAC list were very sparse. I posted my not-so-firm intent to head out to Coyote Lake if other observers would be there. After receiving confirmation from Dick Cook and Greg Wright, I decided to pack up and head south. The observing site is about a 50-minute drive from my home in south San Jose. I arrived at the park around 21:10 PDT. All the boaters had already pulled out of the lot. There was one astronomer (Matt from Berkeley) with his C-8 already set up and pointed at the near-first quarter Moon. As the Sun set, a light breeze kicked up, but it died down by the time it was dark enough to start the night’s hunt. There was no wind for the rest of the night. My observing plan for the evening was to continue my “formal” Messier survey for the Astronomical League’s Messier Observing Club certificate and pin. My observing list consisted of a few bright open clusters and lots of globulars.

Here’s the list of objects that I recorded.....

All objects were viewed with a 25mm Plossl (50x) and a 12.5mm Plossl (100x) (Note: FOV = field-of-view)

M7 (Ptolemy’s Cluster; open star cluster); Scorpius - this is a loose, rich open cluster; very easy to find with naked eye in dark skies; this cluster sits to the east of Scorpius’ “stinger”; the combination of this cluster being low in the SSE, and observing it across the paved lot I was set up on, resulted in a shimmery view of this cluster; the entire cluster fit in the 25mm FOV, but some of the outer cluster members were outside the FOV when using the 12.5mm eyepiece.

M6 (Butterfly Cluster; open star cluster); Scorpius - this open cluster was a tighter grouping than M7; both M6 and M7 are visible in the 8x50 finder’s FOV; the location of the cluster was a bit higher, but the view was still shimmery due to the heat waves rising off the pavement; I guess the “butterfly” shape of this cluster can be formed in different ways depending on the observer - I saw two ways to imagine a “butterfly” formed out of the stars in this cluster.

With these two easy open clusters in the books, it was time to begin the great globular cluster search.

M80 (globular cluster); Scorpius - this is a tiny globular cluster compared to one like M13; the globular is located near the “head” of Scorpius between Antares and the “claws”; it sits in a nice FOV which I made a rough sketch of in my handwritten notes; can resolve stars at 100x magnification.

DETOUR - I noticed a bright star near the E edge of the finder’s FOV; I checked Starry Night Pro and found that I had stumbled upon the multiple star system Rho Ophiuchi; a quick look showed three main components, but I thought I noticed that the primary had a much fainter and closer companion; this was verified when I zoomed in close with my Starry Night software; colors were white-yellow for primary and blue-white for the two bright companions (mags. 6 and 7).

A nice, unexpected diversion which wouldn’t be my last detour of the night. But for now, back to the globulars.

M62 (globular cluster); Ophiuchus - another small globular cluster, but a bit brighter than M80 was; stars were resolved with 100x magnification; I noted a small pair of relatively bright stars (mag. 7 and 8) at the lower (N) edge of FOV at 50x.

M107 (globular cluster); Ophiuchus - located about 2.75 degrees south of Zeta Ophiuchi; this was a very faint globular cluster; it was very diffuse and did not even look like a globular to me; I asked Matt to come over and take a look; he remarked that if I told him I was pointed toward Virgo, he’d suspect we were looking at a faint galaxy; I confirmed the location of M107 by identifying the field using Starry Night; maybe the presence of the almost 1st qtr Moon washed out the cluster; I’ll have to take another look in the future.

M10 (globular cluster); Ophiuchus - now this is a globular!; after viewing the last three globulars, M10 is more pleasing to view; it was not too concentrated, and I was able to resolve individual stars even at 50x magnification; the view at 100x was very impressive; there were numerous brighter stars sprinkled throughout; 5th magnitude 30 Ophiuchi is located just under a degree to the E of M10.

M12 (globular cluster); Ophiuchus - this target sits in a nice FOV - it lies at the W edge of a diamond or parallogram (a mini-Lyra) of 10th magnitude stars with a larger diamond also in the 25mm FOV to the E; lots of stars resolved in the 12.5mm view at 100x.

M14 (globular cluster); Ophiuchus - back to a faint globular; it was a bit tricky to find - I used the Telrad to eyeball the location about one-third the distance between Beta Ophiuchi and Eta Ophiuchi; this one didn’t show any resolution toward the core at the maximum magnification used (100x); at least it is located in a nice FOV which I sketched in my handwritten notes.

M5 (globular cluster); Serpens - a great globular!; at 50x it is located in the same FOV as 5th mag. 5 SER; able to resolve a lot of stars in core at 100x; this globular is almost as pretty as M13.

M9 (globular cluster); Ophiuchus - this real small glob. was easy to find - in the finder, it lies SE in the same FOV as 2nd mag. Eta Ophiuchi; not much of a view at 50x; with 100x you could resolve some stars near the core using averted vision; the 100x view was the better choice.

M69 (globular cluster); Sagittarius - this one was harder to find than expected; it’s located within the “teapot” asterism of Sagittarius in the same finder FOV as 2nd magnitude Epsilon Sagittarii; there was not much detail at 50x; a bit more detail, but not much at 100x.

M70 (globular cluster); Sagittarius - not much to speak of here either; located in a nice FOV - at 50x there are two perpendicular strings of mag. 9 and 10 stars to the S; it was easily located - 2.5 degrees east of M69.

DETOUR - this time the diversion was Comet Gunn; this faint comet had been close to M70 on July 2 or 3; it showed up on my Starry Night finder field still less than a degree away from M70; nothing spectacular to report on this comet, just seeing it was a nice treat though.

M54 (globular cluster); Sagittarius - I got skunked on this one :( It should have been easy to find - 3 degrees E of M70 and a bit less than 2 degrees W of 2.6 magnitude Zeta Sagittarii in the “handle” of the teapot. I didn’t want to spend a lot of time hunting, because Sagittarius had crossed the meridian and was near the light dome from the city of Gilroy. I still had three more targets to bag in this area.

M55 (globular cluster); Sagittarius - I had expected some trouble given this target’s location away from a really close bright star, but after the previuos “failure” I found this glob. rather quickly; I was able to use the Telrad to get close and then it was visible in the 8x50 finder; this object was fairly bright and spread out; the view was good at 50x; at 100x stars were easily resolved.

M75 (globular cluster); Sagittarius - a tiny globular located in a sparse area for star hopping; I had to get serious and use Starry Night to work my way slowly; I ended up using the finder to hop from stars off the “handle” of Sagittarius; this globular was very tiny at 50x; the view was a bit better at 100x - you could make out a brighter core surrounded by a halo.

M22 (globular cluster); Sagittarius - I had observed this object before; it was a piece of cake to find - one finder field away from the top star in the “lid” of the teapot asterism; it was very bright and impressive, even at 50x; at 100x, the globular just about fills the FOV; lots of resolved stars; this glob. is another that rival M13 for pleasing views; it was a nice way to end my observing list of planned globulars.

It was getting late now (1:30 a.m. PDT/ 08:30 UT). Mars had started it’s climb up into the sky in the SE. I had three open star clusters left on my planned observing list before I went looking at Mars. I decided to skip over M25 and M26 and headed for M11.

M11 (Wild Duck Cluster; open star cluster); Scutum - a very rich open cluster with a brighter star toward the center and a pair of brighter stars out toward the SE edge (at 2 o’clock in the FOV); the cluster fills the FOV at 100x; I noted the famous “V” formation which gives the cluster its nickname.

Mars was still a bit low for any steady views, so I went over to see what Matt was up to. He was hunting down faint NGC planetaries in Scutum. He showed me one that was definitely an eye test to confirm as non-stellar. While I waited for Earth’s rotation to bring Mars higher in the sky, I noted that the constellations of Autumn were already starting to make an appearance. I pointed the scope eastward for a quick view of the Andromeda Galaxy. I also noticed that Hercules was in a reasonable part of the sky to take a peek at M13. Viewing this globular cluster quickly reminded me how impressive it is, especially when compared to some of the night’s earlier globular targets. A light dew had started to form on the outside of my scope and on my observing table. There wasn't enough dew to affect my finder. Just to be safe, I moved my eyepiece case to the back of the mini-van to keep my eyepieces ready for use as soon as Mars was willing.

Mars - I had not planned on staying out so late, but last week’s news about the start of a possible Martian dust storm had me thinking I better get in all the Mars viewing I can do now while conditions haven’t deteriorated. I started cycling through my eyepiece/2x Barlow combinations around 2:14 a.m. PDT (9:14 UT). The views were still boiling. I was able to make out the S. polar cap easily. There was also a darker band just below (in my reverse view) the polar cap - could this be the polar “hood”? During the brief periods of steady seeing, I was able to make out some darker Martian surface features. My maximum available magnification of 334x (7.5mm Plossl + 2x Shorty Plus barlow) was pretty useless. Mars was boiling and very unsteady. According to Matt, the typical “best” magnitude (under “average - good” conditions) to use for Mars is about 250x. I found that my best views were at 200x (12.5mm Plossl + 2xBarlow). After trying the various eyepiece combinations and seeing no improvement, I decided to pack up around 3:00 a.m. PDT (10:00 UT). Before I left, Matt decided that Mars was high enough to attempt some viewing. I checked out the view in his C-8 using 250x magnification. Things were still pretty unstable. Matt put in a red filter and we were able to see more surface markings. The surface detail in the filtered view reminded me of the old sketches done by Percival Lowell and others that later gave rise to the overly imaginative Martian canal theory. I finally got into the mini-van and headed home at 3:15 a.m., leaving Matt there as I found him at the start of the evening - the lone astronomer.

It was a night mainly of globulars - great and small, topped off with some Martian views for dessert. I considered the evening very productive with 20 objects observed. This puts a good dent in my Messier list - about 33% completed now. I can pick up a few objects in the early evenings until the group of Autumn objects becomes more prominent.