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Log, Jan 12, 2007

63(+) people: Comet McNaught is really putting on a show far beyond earlier expectations. For the past few days it has been just above the horizon at sunset. I haven't been able to see the entire comet because of clouds on the horizon but some of my friends have had unobstructed views. It is already the fourth or fifth brightest object in the sky after the Sun, the Moon, Venus and rivaling Jupiter. It is a deep diver, passing into the central solar system from above the plane of the ecliptic (the plane of the planets), over, around and then under the Sun, only to leave below the plane of the ecliptic. As it passes unusually close to the Sun, it will be heated much more than usual and there is a fair chance that it may brighten to extraordinary levels becoming one of the first day time comets in the last couple of centuries. If it reaches this highly unusual level of brightness, folks in the northern hemisphere will be basically out of luck, but people in the Southern hemisphere may have something to talk about for years to come. I'm jealous!

I arrived at the Observatory early in hopes that I could see the comet a little better from Charlestown. Clouds made that a false hope. I expected a very iffy night but it turned into one of the most memorable nights I have had at the Observatory in many years. The forecast was for "partly cloudy". Well if the few horizon clouds counts as "partly" then they made their forecast but above 10 degrees the sky was dark, clear and usually steady. It only got better as the night rolled on.

We had gazillions of Cub Scouts [and brothers, sister, Moms and Dads]. They got a chance to see the results when a star partially explodes blasting its atmosphere into space [a thing called a planetary nebula although it has nothing to do with planets]. We saw Albireo where the big thing was seeing the color changes. We went outside and identified constellations and important stars like Polaris and Sirius. Once back inside we looked at M42 where the big thing was the brand new stars and the hydrogen helium gas from which they form. We also tried a wide angle lens later. While the Trapezium was tiny, the field of view was stunning. The Cubs went home before we saw much of Saturn. Initially, Saturn wasn't bad, but it became superb as it rose above 20 degrees (and cleared our pine tree).

By 11 PM, Ernie and I made a really serious attempt to spot the Pup Star - Sirius B. [Yes it’s an intentional pun.] Between us, Ernie and I have over a century of sky watching but neither of us had ever seen the dim second star that accompanies Sirius A which is of course the brightest star in the sky. The difference in brightness is a whopping 9460 times - sort of putting a key chain light on a lighthouse lamp. Imagine trying to see the key chain light against the lighthouse brilliance. For years, the Pup has been just too close to Sirius A to separate the images against the glare. However it is approaching it greatest separation about now.

So did we actually see the Pup? We are both fairly certain that it is the case. We certainly saw a tiny glimmer of light. It was pretty much the right distance from Sirius A (the distance between the two stars is almost double that of Castor nearby which is an ease split). We took every possible precaution against spurious images. We rotated the eyepieces to see if the image rotated (a bad sign!). We did not wear glasses because Sirius A can reflect of the glass' lens back onto the eyepiece. We tried using filters which are supposed to cut down on Sirius A's light while letting the Pup shine though. [This is a greenish filter but frankly I don't think it was worth a whole lot at this job.] If we weren't trying to be perfectly scrupulous in our viewing, I think both of us would say that the century of waiting [between us] is over.

Ernie convinced me to stay on and try for the Horsehead Nebula. You have all seen pictures of the black horse's head against red backgrounds. Well the red background is caused by emission of light in the "beta" line of hydrogen gas. The emission is powered by hidden embedded stars radiating in the ultraviolet. The horse head itself is just more of this gas, that happen to be closer to the Earth and which blocks part of the hydrogen beta red light. Now the human eye actually sees four colors - red, green and blue during the day and a dim color [primarily in the cyan frequencies] when the eyes are dark adapted. Guess what color does NOT give rise to night vision - yup, the color red - in particular the beta lines of hydrogen. Just like we cannot see infrared or ultraviolet with the red/green/blue sensitive cones, we cannot see infrared, red most orange tints and ultraviolet with the cyan sensitive rods.

What all this blather means is that the Horsehead Nebula [and its two evil twins, the California Nebula and the Cone Nebula] are easy to photograph with red sensitive film, or with CCDs which are very red sensitive, but terribly hard to see by eye. Given how big the nebula is, and how much energy it pumps out, it would have made Charles Messier's list in a snap IF Monsieur Messier eyes could have seen the frequency! So how come we can see anything by eye today. Enter a special purpose filter which highlights JUST the hydrogen beta frequency. Make everything else even darker, and the faintest of faint red glows can be seen as a lighter gray obscured by a darker gray.

Did we succeed? Well not to Ernie's satisfaction. We know with exact accuracy that we were correctly pointed. Guide stars we choose were all exactly as we expected. In the past, I have twice seen the Horsehead through our scope with the hydrogen beta filter in place. Last night, for an instance I saw a darker blob against a just barely different background. I could not make out any details. By the time poor Ernie got to the eyepiece this chimera had vanished. And it never returned. We tried and tried but eventually Ernie sang out. "Hey, Les, Orion is vanishing. I just saw Rigel wink out." Yes, this morning's drizzle was moving into the area. We packed up and went home much later than we usually did.

One thing which was spectacular was the performance of our 19 mm eyepiece. For conditions last night, the 214 magnification ocular was ideal. It held images steadier than any higher power forming excellent disks with hints of Airy disks. Lower power oculars gave steady images but lost detail and contrast.

I'm sure by now that some of have noticed the dancing couples at either side of the banner proclaiming that the Sky Theater is funded. We are holding a dinner dance for the benefit of Frosty Drew Nature Center and the Observatory on February 10th. We'll have a live band for dancing. Tickets will be $50 per person with some of the proceeds going towards the Sky Theater and the rest supporting the Nature Center and Observatory programs

-Les Coleman

Leslie Coleman
Leslie Coleman
Entry Date:
Jan 12, 2007
Published Under:
Leslie Coleman's Log
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