Log, Jan 25, 2008

30 people. What a night! As Francine and I opened up, the sky was basically dark down to the horizon except for patches above Providence/Warwick and the Casinos diametrically opposite. The air while not perfectly stable was better than I have seen it for many months. I could look out and see dark lanes in the Milky Way. Francine was making all sorts of exclamations like "I can see Praesepe with the naked eye". To the northwest I could easily see the core of the Great Nebula in Andromeda and hints of the nebulosity that stretches in an elongated ellipse. The only minor stability problem was directly over the ocean at altitudes below 15 degrees. The warmer ocean water at 30 to 35 degrees caused local turbulence with the colder land air that was dropping into the twenties. The night was something like 9 out of 10 until the Moon arose and was probably no worse than 7 out of 10 at that point.

Nothing is more exciting to me as a presenter at FDO than the excited cries of children as they see things which are the glories of the sky. Sometimes the oddest things are the most exciting to them. Mars quickly passed from below 75 degrees elevation into the blind zone we have at the top of the dome. [Yes, I know we can open the top third of the shutter but we discussed that last week.] So I wished to turn to Saturn before the Moon arose. This left a very short time window. Unfortunately, Saturn happened to be in the outer boughs of the pine tree to the south east of the dome. The kids were amazed (and frankly so were we) that while we couldn't see Saturn by eye, enough of its light filtered through the needles to form a so-so image. Later that evening (unfortunately after the Moon was up and some of the younger kids were homeward bound) Saturn presented a really nice image - not perfect by pleasing.

Well what else did we see? We saw M41 (a cluster just below Sirius), M42 (the Great Nebula in Orion), M43, the other part of the Great Nebula and the Trapezium. Not only could we see the four bright stars of the Trapezium [Theta 1 Orionis stars A, B, C and D] but also the much fainter stars Theta 1 Orionis E and F. Seasoned observers could intermittently make out the almost mythical Theta 1 Orionis G. I can't remember when I last saw G for sure and certainly not when a gibbous Moon was nearby.

One gentleman was initially disappointed when he looked in the scope at a cluster and "just saw stars". He mistakenly thought that somehow the telescope was showing him the whole sky rather than a single open cluster. When he realized that the area of the sky we were actually seeing was scarcely bigger than a pin prick he suddenly was very excited. When he learned that the scope was seeing stars more than a quarter million times fainter than his eye could detect he went way suitably impressed.

We saw the Eskimo (always on a cold night!). We split several stars; saw the Moon, and other random objects. We took a twenty minute break to chip ice off our fingers in the warmth of the Nature Center. But eventually the night got late enough that the last kids had left.

Ernie Evans suggested we try an experiment. He had built a gizmo called an apodizing filter out of screening material and cardboard for his 11" scope. He had used it to view the companion star of the brilliant star we call Sirius. In fact Sirius is two stars, a normal blue-white subgiant called Sirius A (the Dog star), and a white dwarf star that orbits the Dog star which most of us call the Pup [in fact Sirius B]. I have been viewing the sky since 1947 through telescopes. During the early years of my observations (mostly with homegrown small telescopes), it never occurred to me to try to view the Pup. I didn't even have a life list. Now, late in my life it has become a goal, but unfortunately the good viewing chances of20 to 30 years ago passed me by and the Pup was snuggled up against the Dog and all but invisible as far north and as close to the Atlantic as we are.

Well we tried out the apodizing filter. First of all the display was dazzling (literally). It operates by moving light away from the central bright star to little radial streak that are spectrums of the star. The effect is most noticeable in bright stars and all but totally invisible in dim stars. The brilliant Dog Star is effectively dimmed just as the Pup is left unchanged. The 10,000 fold brightness difference becomes perhaps a 1000 fold. It is still large difference but much less impossible. Additionally the first diffraction disk surrounding a star is dimmed almost to extinction while brightening the central core. On the down side, Ernie's filter was designed for an 11" scope not a 16" scope. To place it over the 16" scope, about 2.5 inches on all side is masked out completely. It makes the 16" scope behave like an 11". And not even as nice an 11" as Ernie's private telescope but one with a larger central mirror. The result was the 16" scope was effectively about a 10" scope. The mounting arrangements were not ideal either. Basically, Ernie mounted his filter on a cardboard box side larger than the end of the 16" scope. Rubber bands and a string with a couple of make shift hooks made of paper clips attached the whole thing to the 16". While we tried, the filter wasn't exactly centered. The off centeredness leg to a "coma" in the out of focus image of Sirius. The bulge of the coma lined up with what turned out to be a spurious "Pup" star at 8 o'clock as we viewed the image.

Unfortunately for any claim that the 8 o'clock image was the Pup was dashed as soon as we checked the background stars against the Hubble data base. The Pup should have been between 4 and 5, not 8 on the clock face.

We looked again and yes, Ernie, Francine and I saw something at about 4 to 5 on the clock face but I never got a clear separation between the Dog and the Pup. Was the Pup really there? Tentatively I am saying "yes", but I really would like additional strong confirmation. The few folks who stayed with us looked but they didn't seem to see anything for sure.

Was this a lost cause? By NO MEANS! By closing Ernie, Francine and I were tossing around plans for a 16" apodizing filter with proper clips to the telescope's optical tube assembly [OTA]. I think I can create a firm filter (probably with 3/16ths plywood and firm clamps that will not rob more than 3/4ths of an inch in diameter from the 16" - maybe less. We can't make the "ring" of the filter too heavy or the scope's balance will be shot, but a pound or less balanced by a weights on the camera mount should do very nicely. Centering will be no problem if we cut the ring using a "jig" with a saber saw. Not only will this give us a way to cut the Pup free from the Dog, but a better tool for separating close double stars. I'm really excited.

-Les Coleman

Leslie Coleman
Leslie Coleman
Entry Date:
Jan 25, 2008
Published Under:
Leslie Coleman's Log
Subscribe to Leslie Coleman's Log RSS Feed