Tuesday, April 25, 2000

More Backyard Astro-Card Fun

As noted in last night's observing report, I had constructed a "duck blind" in order to squelch the experiment in fission taking place in my neighbor's kitchen window. By afternoon I had half the surface covered with black garbage bag material (on PVC), and decided the other half could wait, that the neighbors hadn't had their backyard light on recently (where the other half of the blind would be effective), only the kitchen. At 9:30 p.m., amidst the insanity of their dog going berserk at the noise I was making, up it went. I looked, and perfect! There was no light in my backyard from their kitchen. Success! The sky was clouding over, so I went in to pass some time. No sooner did I check back than, to my amazement, the neighbor's kitchen light was off, and (here comes Murphy) the backyard light was on! Oh well, still cloudy.

By 11 p.m. the sky had cleared, and to my amazement all the neighbor's lights were off. Out I went, looking to spend perhaps an hour. Despite the lack of neighbor's lights, the sky seemed bright. There were some puffs of clouds to the west, but they were evaporating. It was warm enough to be outside in a t-shirt.

I took out several Astro Cards, from sets 2 and 4, and began hunting first in Canes Venatici, which was up quite high and a bit north of zenith. I was having trouble picking out Chara (Beta Canum Venaticorum), it was just in-and-out at mag 4.25, so this was not the darkest of nights, although once past zenith to the north, the sky at my home brightens dramatically due to San Jose's light dome. I assume about mag 5 - 5.3 to the south this night.

My equipment for the night, same as last night... 10" f/5.6 Dob with Telrad, 11x70 finder, 19mm Tele Vue Panoptic and Astro Cards.

I began in Canes Venatici, searching out NGC 4490. Sitting about 1/4 the distance from Chara to Cor Caroli is mag 6.35 9 Canum Venaticorum, a nice yellow-white star a couple hundred light years distant. In my finder I could easily see Chara and 9-Camum. About the same distance away from Chara as is 9-Camun sits NGC 4490. This object was easy to find and see, appeared elongated about 2x1 in an E/W orientation. It seemed to have a thick core. A small triangle of mag 11 stars lay about 13' to the north. I was unable to see NGC 4485, which should have been in the same field. In a dark sky, this is a wonderful pair of interacting galaxies to observe. NGC 4490, also known as the Cacoon Galaxy is 6.3' x 3.1' with a magnitude of 9.8 and surface brightness (sb) of 12.9, well within backyard range. On the other hand, NGC 4485 (Arp 269) is much smaller at 2.3' x 1.6' and dimmer at mag 11.9 with an sb of 13.2. I'll try to pull in 4485 again tonight... I think it should be possible.

I next moved on to NGC 4449. Again using my finderscope, I could see Chara and a pair of stars out past NGC 4490, which were perpendicular to a semicircle of dimmer stars with one star alone, centered in the half-circle. This pointed me right at NGC 4449, an equal distance beyond the semicircle from the pair. This is a large galaxy, taking up 1/8 my field of view. It appears elongated N/S and seemed to be shaped somewhat like M104, with a 2x1 ratio along its major axis. I thought it might be an edge-on, but looking at photos today, it is obviously a highly disrupted galaxy, still, in the skies I'm working in, it is easy to mistake it for edge-on due to some of the irregular extensions. The closest dim star sits about 7' E.

I came back to Chara next, and moved to the 9-Canum, then toward and past a mag 8.3 star about 8' away. Took me almost directly out to NGC 4618. It is interesting to look at this galaxy's DSS image the day after. My notes say "small with bright core, round or face-on, diffuse halo, dim star 1/4 FOV to west, briter star 1/3 FOV north, no sign of NGC 4625, dim close double 2/3 FOV to SE, core stellar, possible extended NE/SW." The DSS image shows why it looked round, there is an obvious arm curving north of the bright core This one would be fun in a dark sky. The galaxy, also known as Arp 23, is 4.2' x 3.5' in angular size, mag 10.8 with a sb of 13.5, so, not bad for my backyard!

One of the objects that eluded me the night prior was NGC 4699 in Virgo. I just could not see the guide stars to pin the location down. This night was different. I could just see mag 4.8 Psi-Virginis and mag 4.6 Chi-Virginis. NGC 4699 lay almost exactly between the two stars. Using the finderscope, I put Chi in the center. Three mag 7 stars formed 3/4 of a diamond shape around Chi, and provided orientation. I spotted a dim chain of 5 mag 7 and mag 8 stars to the SSE of Chi, and NGC 4699 lie just off them to the north. 4699 was small, with a bright core and small disk. A star lay 1/4 the FOV east, a dim double oriented N/S was 2/3 the FOV to the west. This was a nice The DSS image confirmed my notes, there is a very bright core, and a face-on disk appearing very dusty. Nice image! The galaxy is larger than the eyepiece view reveal, at 3.8' x 2.6', but at mag 9.5 and sb 11.9, this one is a good in-town object.

My final object for the night was NGC 4697, about 2 degrees away from NGC 4699 to the north. Again using the finder, I was able to see field stars that easily identified the correct field. My notes call the galaxy large, elongated E/W (I had a question mark by that remark) about 3x1, possibly disrupted (another question mark). A nice "L" chain of stars ran from the galaxy's south in and E to W direction, then bending S to N. A mag 9 star sat near the edge of the FOV to the NNE. My last note calls the core of the galaxy stellar. Looking at the DSS image, the only thing wrong in my description was the comment about disrupted. The galaxy is 7.2' x 4.7', bright at mag 9.2 and sb 13.1. The significantly dimmer sb in this one indicates just how bright the core is and how large the dimmer nearly halo must be.

The one object I didn't see that in retrospect I would love to is NGC 4731, very nearby NGC 4699. The DSS image shows this galaxy as a highly disrupted barred spiral. I'll be trying for it tonight, but expect is will be a challenge... although it is mag 11.5, the sb is 14.6 (yikes!).

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