A little Sunday observing report: My first goal (and always one I enjoy) was to catch and track Venus in daylight. I had done so at work without the assistance of the Moon on Friday, but I intended a longer and more comprehensive look today. I brought the telescope out to the side of the house at about 3:40 pm (with the Sun still high in the sky, a little under four hours from setting) and the Moon/Venus pairing near culmination in the south. This would be maximum height for the two bodies for the day, making them easier to pick out. I also didn’t want to wait too late, because it’s not as much of a victory with the Sun lower in the sky. The Moon is currently, as of this writing, passing to the south of Venus (though I’m reading now that it occulted the planet for parts of the Southern Hemisphere). I stayed out about 45 minutes, and during that time the orientation of the two bodies perceptibly changed (the Moon moves across the sky by about half a degree, or about its own diameter, per hour). I first found Venus by looking through the telescope at the Moon and moving up; there was the planet clearly above it. Finding it naked-eye was much more difficult, as it generally is. At elongations from the Sun of more than about 30 degrees, Venus is plainly visible in the sky if one has the exact location. The issue is that it’s just a tiny white point, and the sky is very bright and difficult to concentrate on for long periods of time. Amanda outright refused to even attempt the Moon when she came out for a look. The Moon passing by it affords a locational reference, fixing the eye on a part of space which allows one to more easily catch the planet. At the time I observed, the planet was about a Moon-diameter away, perhaps slightly more, in line with the two crescent cusps. After about 15 minutes of positioning and straining my eyes (while also using the house as a shield from the Sun), I caught it for a split-second, then lost it again. Five more minutes were spent waiting for clouds to clear from the local vicinity, and the operation began again. This time I caught it more quickly, and recovered it more easily when I lost focus. Eventually, during my telescopic viewing (I hit all three spots on the magnification tree), I got to the point where I could just look up from the scope naked-eye and find it. After some eyepiece pictures and some more study of the disk, I went inside. The disk, by the way, is roughly 60%. It’s much, much easier to discern the edges with the lower daytime contrast; Venus is so bright that it causes washout at night. The only issue is that the daytime eye is constricted to a very close match of the 2.7 mm exit pupil on my 28x eyepiece. One issue with the exit pupil being near or over the diameter of your eye pupil is that you can see the secondary mirror shadow, which is somewhat obnoxious, if nothing else. At 70x and 140x, with exit pupils near and around 1 mm, this evaporated. Venus, as I may have mentioned before, appears white to the eye due to its incredibly efficient reflection of solar radiation. It is closer to the Sun than we are, and reflects much more of the light that hits its cloud tops (65%). Probes that get up close to it see a muted beige, but from Earth, it’s really just going to show up white. The disk is clear and crisp, having grown to 15.6 arcseconds (well within the range of small telescopes like mine). Phasing is totally obvious, with very little light bleed; the contrast reduction means I just looked at the planet and little extraneous light. Again, I found myself lamenting my lack of power; this, I am told, is “aperture fever,” which can only be cured with more aperture. Anyway, after I went inside I periodically stuck my head out to see how the system was moving. Over the next few hours, the Venus-Moon pairing moved from the south to the southwest, slowly dropping. The angle between the Moon and Venus was also slowly changing, which became obvious with each new observation. The Sun did not set until 7:23 from here, so I was repeatedly catching the planet in daylight. The Moon orbited past Venus on an hourly scale, pushing Venus further to the west of it as it went. The distance between the two didn’t really change much; Venus was north of the Moon, so even though Luna was passing it, they ended up staying in the sky an equal amount of time. By the time they set, Venus was more to the side of the Moon than above it. The other daylight “observations” were pretty cool as well. At about 5 pm I caught Venus through the window of the front door (a first). Around the time Azarenka won the second set (so, sometime in the 6 pm hour), I did so again, though I note the second time because it just seemed remarkably easy. It was, no doubt, getting easier; with the Sun low in the sky everything up there was becoming more prominent. Finally, after sunset, I observed the bodies one last time, Earthshine becoming prominent on the low crescent Moon and Venus shining like a headlamp, visible to everybody. At the time, Amanda happened to be outside watering the plants, so she got the telescopic view of both of them. She also got Saturn, which had just come into view to the upper left of the assembly. I explained the 2 Librae complex to her, and she exclaimed that it was almost a perfect triangle. I mentioned in my previous note that Saturn would move to that position, though I didn’t really go further than that and had no idea what day it would be. I then explained the “stars confused for moons” concept, though in this case that was not a problem. The one visible moon that COULD be seen by my telescope, Titan, is over 9th magnitude now and very difficult to catch at low altitude. Amanda did not see it when she looked (and probably wasn’t that interested in it in general), and I didn’t see it either while I was centering the planet for her. After Amanda went inside, I did a more leisurely, relaxed study and noticed the moon well off the planet (a few ring-diameters), obviously near elongation, but requiring averted vision and very, very faint. Conjunction is not for two months, but certain aspects of the Saturnian system are already being closed to view. In addition, the planet is setting around 9:30 at this point, which means there is a very limited time to get Saturn at any kind of height. Dim features do not take kindly to altitudes under 20 degrees, and Saturn is going to be below that while the Sun is down from now on. So it goes with that, I suppose. Later on I went out again, going after the same five targets I’ve been looking at for the last week or so. First came the variables. Nova Delphini 2013 continues its dimming, though at a definitively slower pace. I keep confusing Eta and Gamma Sagittae, so it took me a while to find, but once I did I noticed significant changes. The nova is now dimmer than both stars of its “companion double,” located near it, so if it didn’t look like a pedestrian, “blend in” type of star before, it sure does now. The orange hues have become a little bit more pronounced, and I’d say that a faint orange-white is now the primary color (and orange if I had to pick one of the two). This reddening is, as I’ve mentioned before, correlated to the falloff of total brightness from the nova. AAVSO data suggests a magnitude of about 7.4 to 7.5, with a few higher outliers in the 7.2 range which get more infrequent as one gets closer to present-hour observations. I will go with 7.4 to 7.5, meaning in the last four days we’ve lost only 0.2 magnitudes (or 0.05 per day). This is a marked decrease in the rate of dimming, which has been, on average, about 0.12 per day since August 15. Perhaps this means something, or perhaps it doesn’t. From what I’ve read, novae, especially brighter ones, are as predictable as comets, which is to say they can’t be predicted very well at all. The saga here will definitely continue. From there, on to Chi Cygni. I jumped off Eta Cygni at the wrong angle, and it took me far too long to find the area (I can recognize the enclosure if anything else). I corrected myself, found it, and just barely observed the star. It’s in that hazy band between averted and direct vision (mesopic vision?) at 28x, but again, fully visible at 70x (though it’s getting kind of tough there). Color resolution is now beginning to degrade; my eye is not getting enough photons from the star to keep it in the best part of my retina. It’s almost a brown-red color to me now, but not distinct at all, and tough to even see. It’s still there, though, and it’s still got a way to go before it’s totally invisible. I am still wondering what will claim it first, invisibility due to magnitude, or invisibility due to conjunction with the Sun. A look at the charts says it will have to be magnitude, but my telescope stubbornly refuses to stop catching it. AAVSO reports are a little less common for this one (apparently they’re all looking at the nova), but there are two observations on September 8, a 9.7 and a 9.8. There’s a 9.6 from yesterday, so I’m going to split the difference and say 9.7 with a little uncertainty. That’s probably right. After 10, averted vision is a must, and we’re not quite there yet. My real test is going to be what happens when the star approaches 10.5 and requires averted vision. How deep can my telescope go? I then moved over to Neptune, which has “technically” exited the triangle through which it has passed for the past month. I still use the same jump, though, because Neptune is now sitting next to one of that triangle’s vertices in a “double” formation. I found it because that star is red, and Neptune is blue, which created a good contrast and made identification quite easy. I did not notice any real difference between the two except in the blueness; Neptune has a more striking color than any of the stars in the vicinity (especially the 8th and 9th magnitude stars visible in the field). Neptune’s companion (HIP 110439) is magnitude 7.75, while Neptune itself is 7.8. This caused me issues; I had thought Neptune was brighter, and I saw them as equal. I knew it was Neptune (color and position gave it away) but I had to check it out later just to make sure. I went through the magnification tree and really found 70x to be the best magnification. Too much fuzziness was evident on anything higher. Other than the movement (Neptune will pull away over the next week, slowly, slowly exiting), there’s really not much else to report on the outermost planet. Yes, I believe Pluto is not a planet. I then moved east into Pisces, and caught the asteroid Bamberga. The house next door was lit up like the Fourth of July (does anybody turn their lights off anymore?), but I was still able to find Gamma Piscium naked-eye, which made the telescopic star 7 Piscium an easy jump. From there, I saw where Bamberga used to be, and used the Stellarium charts to reference where it currently was. I found it northwest of its prior position, a bit far even for locational references, having moved much faster than I am accustomed to seeing objects move (note that I was burned in this way on Iris just last week). However, I confirmed it, and as such I’ve now added another main-belt asteroid to my observing logs. I ended with Uranus, probably my most favorite part of the “night portion” of observing. The other four objects were quite dim, all dimmer than magnitude 8 and thus quite underwhelming in terms of brightness. Uranus, on the other hand, is a healthy 5.7, brighter than a Jovian moon, and while it is not naked-eye, it is quite bright if telescopically enhanced. Finding Epsilon Piscium naked-eye with the neighbor’s house light illuminating the whole street was way too difficult (PECO thanks you for the donation), but it was found, and I quickly moved to the area I believed the planet to be. It wasn’t there, so I backed up and tried another angle. The only thing that saved me was Delta Piscium, which heads a series of stars that point right at the planet. The only problem is that the star is magnitude 4.4, theoretically visible but not over the light dome of Coatesville and the lights of the neighbors. Uranus formed a sort of very narrow L shape with two stars last time, with the planet being the “vertex.” Since then it’s moved westward to the other side of its “companion,” now sitting within 2 arcminutes of that star (HIP 3357, mag 8.8, if anyone was wondering). Had this been Neptune, we would have had two relatively faint bodies with a color dichotomy, and that would have been that. Not so here. Uranus is twelve times brighter, and dominates the area. It has a green-white hue, which sets it apart from every star, and magnifying it does give it a perceptible, albeit small disk. It’s almost like a cosmic emerald, though perhaps with a little bit more white, and it’s rapidly becoming one of my favorite “challenge targets.” Knowing what Venus looks like at 15 arcseconds, I can guess at how Uranus would appear at extreme magnifications, and it’s quite an interesting thought. So that was it; a whole bunch of movement confirmation as well as observation of some old variables. Nothing remained the same from the last time.
Posted on: Mon, 09 Sep 2013 04:56:05 +0000
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