Sunday, September 16, 2012

A few summer objects and the Sky Commanders

Now that I have had the Sky Commanders for a couple of weeks, I have rectified all the shortcomings of the stalk I had made for it, and I also made a lead to connect it to my Dewbuster. In addition to powering and controlling heater strips, it also has 12-volt outlets to connect other devices that require battery power, such as the Sky Commander computer unit. That way I can power it with my 12-volt, 18 Amp-hour battery and doing so will also enable the built in heater to function as well. Even with the heater on, the Sky Commanders use only 130 milliamps of current, far less than any heater strip and hence it places little demand on the battery. That allows it to work in cold temperatures, as low as -25 degrees Celsius, colder than I would normally ever be exposed to here on the Gulf Coast. LCD displays get sluggish in cold temperatures, and therefore there is a heater inside the computer unit that will enable it to function even during cold winter nights. That feature is going to come in handy since winter is the only time of year where I can reasonably expect clear and dark skies. Summers are usually very murky and cloudy in this region of the world.

I also bought some knobs from McMaster-Carr, a company that offers just about any sort of fastener you can imagine. Four of them were used to make custom threaded bolt and knobs to secure the stalk to the rocker box side, and two are used to attach and detach the altitude encoder. When transporting the telescope I can now remove the computer, altitude encoder, encoder arm and the stalk to protect them from damage, then quickly re-attach them for use at a dark site or at home. I store the computer, altitude encoder and arm, and power lead in the case with the upper tube assembly because they are fragile and expensive too to replace.

I am greatly impressed with the performance of the Sky Commanders on my 15-inch truss-tube Dobsonian. I have located very tiny planetary nebulae that are nearly stellar and only identifiable because they have a peculiar blue or greenish color with them. When I entered these objects into the computer and slewed the telescope to the location indicated by the computer, they were either in the field of view or just outside of it, at 227X or even higher. Even at 425X object appeared in the field of view. Unfortunately, my plans to try them out at a darker site than my driveway fell through once again due to the sudden appearance of thunderstorms. I was hoping especially to get a look at the galaxy NGC-5611 in Bootes, which has a type 1A supernova underway in it at this time. It's at about 13th magnitude and visible to an 8-inch telescope, but Bootes and the galaxy are going to soon be lost in the glare of the Sun. The chance to try them out under darker skies that will have to wait until October at the earliest, this year more than half the time weather made driving to the club's site at the airstrip futile because of wind, clouds and rain. Nevertheless I did observe a lot of star clusters and planetary nebulae from home, and the planets Jupiter, Uranus and Neptune.
NGC-6790 in the constellation Aquila was a planetary nebula that eluded me repeatedly, until a recent article in Sky & Telescope by Sue French provided the clue I needed to find it. It is nearly star like but had that telltale blue-green color that enabled me to zero in on it once the Sky Commanders guided me to the right area of a very dense Milky Way star cloud. Boosting the magnification to 425 and 572X showed not only it's nebular character, but revealed it's oval shape and the central star. It's quite bright and is visible from light polluted locations, the trick is finding it but it can be observed in smaller telescope once located. It's apparent size is no greater than the planet Uranus, with dimensions of 2.5 X 4 arc-seconds. The 4.7mm ES eyepiece provided a much more pleasing view than the 3.5mm Orion Stratus, due to the fact the seeing was mediocre at best and the ES eyepiece is more comfortable to use. It lies in a formation of stars that looks like a very gluttonous slice of pie or pizza, with the nebula in the middle of the round edge of the slice.
The larger but still very small planetary nebula IC-5217 resides in the little constellation of Lacerta, the lizard. Like its terrestrial counterparts, Lacerta is almost hidden among the dense star fields of the Milky Way and surrounded by Cygnus, Andromeda, Cepheus, Cassiopeia and Pegasus. But this little constellation does contain a few note worthy star clusters and this planetary nebula, which appears as a tiny round disk at high magnifications. It resembled the planet Uranus but somewhat larger and much fainter of course. Unlike NGC-6790, it was much easier to spot among the dense star fields along this region of the Milky Way, and was a nice object to observe from my driveway. No sign of a central star was evident, even at 425X.
The open cluster NGC-7086 was one of a number of open clusters I observed in Cygnus. Fairly large and rich, it stood out well with a sinous formation of brighter stars, plus another one that forms a long right triangle with two of them. Other objects observed for the first are the open clusters NGC-7031, NGC-7039 and NGC-7082 in Cygnus, NGC-7772 in Pegasus, and NGC-1027 in Cassiopeia. Recently, a pair of amateur astronomers detected an impact on Jupiter's day side. I have been watching the planet recently to see if any sign of an impact scar exits, but so far I have seen no sign of one. It appears whatever it was, it was too small to have left one, but Jupiter is also showing signs of dramatic changes in it's equatorial belts. This planet is worth the effort to observe it, because it's atmosphere changes constantly and spots, storms and ovals come and go. Perhaps someone will spy the scar left behind by another asteroid or comet that dove into the planet that otherwise could have been meant for us.