OAS Executive Committee 

President- Dave Dunn Ph. (801) 544-7705

Vice Pres- Lee Priest Ph. (801) 479-5803

Secretary- Bob Tillotson Ph. (801) 773-8106

Treasurer- Doug Say (801) 731-7324

JANUARY'S MEETING

The first monthly meeting of the new year will be held this Thursday January 10^th, 2002 in the Ott Planetarium on the Weber State University campus. Cliff Peterson is providing us with a movie on mirror making at the Stewart Observatory Mirror Lab. This is the mirror lab where Roger Angel produces the large honeycombed mirrors.

OAS GOES TO ASTRO CAMP

Text and photos by Lee Priest [Click on the images for a larger view.]

With the Shuttle lined up for the runway, it looked like I was about to make a good landing. Suddenly the approach markings said I needed to bring the nose up. I pulled back on the stick but very quickly the nose was too high. After another over correction, I heard over the intercom " you just dug a ten foot trench in the runway".

Oh well, so much for my career as a shuttle commander; good thing it was only a computer simulation. This is how a group of OAS members and a few extra people spent Saturday morning, the 8th of December. Thanks go to Dave Dunn for wisely trading the Star Party we held for Astro Camp last summer for two missions in their Space Shuttle simulation.

Ed Douglas is manager of the shuttle simulator and was a lot of fun to work with. We had eight people make it so we all got to do both missions. There are eight stations, four in the shuttle and four in mission control. Each mission consisted of a pre-launch, launch into orbit, reentry, and landing. Each station has several switches and lights that need to be watched and controlled at the right time according to the script and we all had head sets to communicate with each other. We all had to work together as a team to make the mission successful. Our second mission was much better than the first, with Jeremy Mathews at the controls; he was able to make a successful landing, which really helped our score. The eight that participated were, Dave Dunn, Lee and Carol Priest, Jeremy and Jason Mathews, Ken Butler, Bill Townsend and his son Dwight.

MINUTES

OGDEN ASTRONOMICAL SOCIETY

December 13, 2001

The OAS met on Dec. 13, 2001. President Dave Dunn opened the meeting. A question was presented on if members were interested in doing winter star parties. A few members were in favor of the suggestion.

The Astro Camp shuttle mission was fun and informative. The space shuttle crew and mission control comprised of 8 people. The first mission score was 69 points, and the second mission scored 177 points. (There was some damage done to the runway as the orbiter landed, but not even a scratch on the obiter.)

There is a planned Messier Marithon for March 15 and 16, 2002 at Dead Horse Point. Dave Dunn has reserved the group site at the State Park there.

The Golden Spike overnighter was a success despite a bit of dew and rain on Saturday night. Friday night was very good seeing, the views Saturn and Jupiter were excellent. On Saturday night, the clouds cleared and the Leonoids came through with a very good show.

The meeting was then turned over to the members for a Show-n-Tell: Dave Dunn presented his 16-inch glass blank that he had ordered. He will grind it down to an F5. Dave also displayed his home built grinding bench built from wood - portable and very functional as it allows the optician to set with the bench.

Wayne Sumner displayed his Russian built Maksutov-Newtonian 102mm. It has a rotating secondary mirror that allows viewing with or without the primary mirror. Ron Vanderhule presented his purchased T&T binocular mount. The tripod is built from 3 aluminum crutches. The top of the tripod rotates 360 deg., the arm for the binoculars is counter balanced and maintains horizontal setting while pivoting for observers height; the binocular mount swivels in both the vertical and horizontal directions. Andrew Pratt presented his battery powered fan mounted on the side of his Newtonian. Useful in quickly bringing the optics down to night time temperatures. Andrew also showed on the planetarium dome pictures that he had taken at several of the observatories at Tucson AZ that he was invited to attend last summer. Lee Brown displayed his photographs of various celestial objects including Mars, Polaris, and Orion.

The meeting was adjourned at 8:50pm.

Alan Jensen for Bob Tillotson

Jim Seargeant's - Images

M15

This image of the globular cluster M15 was built up from frames taken by Jennifer Castle, one of Adam Johnston's students at Weber State, on 15 Nov 01. She took two, 240 sec exposures using the SBIG ST-7 CCD camera at high resolution though the 12" Meade LX200 operating at f/6.3. With a Magnitude 9.03 star available in the ST-7's tracking chip, the AO-7 was able to guide using 0.5 second exposures. The camera cooling system had no trouble getting down to -20C with the cooler nights, and this minimizes the noise generated by the imaging electronics. In the summer months, I often have to use water cooling and contend with frost to operate at such a low temperature - winter is no problem.

It took me a while, but I finally prepared the calibration images needed to make the raw frames into a "pretty picture". With high quality calibration frames, and using Mira AP for each data frame, I subtracted the bias inherent in any CCD chip, subtracted the thermal noise built up over the 240 sec exposures, and divided by the flat frame to take out noise (dust donuts, vignetting) introduced by the optical system. I registered the two cleaned up frames and median combined them. I then used AIP for Windows do apply Digital Development to show the cluster as a concentration of individual stars, rather than just a bright blob.

This is a fairly good image, but the stars are not truly round - they are a bit smeared left to right. This is a flaw in the telescope tracking that I haven't identified. I need to check if any of the plethora of wires hanging from the OTA is causing a drag in the RA motor and also if the colder temperatures causes the oscillator that controls tracking speed to slow a bit. There's always something.

The following information on M15 is from the Students for the Exploration and Development of Space (SEDS) at www.seds.org. (SEDS is a marvelous collection of information and links!)

Globular Cluster M15 (NGC 7078) in Pegasus"Discovered by Jean-Dominique Maraldi in 1746.

Globular cluster M15 is among the more conspicuous of these great stellar swarms. At a distance of about 33,600 light years, its diameter of 12.3 arc min corresponds to a linear extension of about 120 light years, and its total visual brightness of 6.2 magnitudes corresponds to an absolute magnitude of -9.17, or roughly 360,000 times that of our sun. Its brightest stars are about of apparent magnitude 12.6 or absolute magnitude -2.8 or a luminosity of 1,000 times that of our Sun, and its horizontal branch giants are about of magnitude 15.6. The globular cluster is approaching us at 112 km/sec.

This globular cluster has the their rank in known variable star population, after M3 and Omega Centauri; a total of 112 variables have been identified. One of them is apparently a Cepheid of Type II (a W Virginis star).

M15 is perhaps the densest of all (globular) star clusters in our Milky Way galaxy. The Hubble Space Telescope has photographically resolved its superdense core, as shown in this HST image. M15's core has undergone a process of contraction called "core collapse", which is common in the dynamical evolution of globulars; of the 147 known globular cluster within our Milky Way Galaxy according to W.E. Harris' database, 21 have been found to contain a collapsed core (among them, besides M15, the Messier globulars M30 and M70), and there are 8 more candidates, among them M62. It is still unclear if the central core of M15 is packed so dense simply because of the mutual gravitational interaction of the stars it is made of, or if it houses a dense, supermassive object, which would be resembling the supermassive objects in galactic nuclei. The one in M15 would among the nearest and better observable to us, being only little more remote than the Galactic Center and much less obscured by interstellar matter. Although the true nature of these objects remains obscure for the moment, many scientists believe they are strong candidates for "Black Holes".

M15 was discovered by Jean-Dominique Maraldi (Maraldi II, 1709-88) on September 7, 1746 while he was looking for De Cheseaux' comet; he described it as 'A nebulous star, fairly bright and composed of many stars'. Messier and Bode couldn't make this out and described it as 'nebula without stars', so that it remained to William Herschel in 1783 to resolve this fine star cluster.

"With its apparent visual brightness of magnitude 6.2, M15 is about at the limit of visibility for the naked eye under very good conditions. The slightest optical aid, opera glass or small binoculars, reveals it as a round nebulous object. It appears as a round mottled nebula in 4-inch telescopes, with at best the very brightest stars visible, but otherwise unresolved in a fine star field. In larger telescopes more and more stars become visible the outer parts are resolved, with a more irregular, non-circular outline. The compact core, however, stays unresolved even in large amateur telescopes, but the brightest stars can be glimpsed even there. Chains and streams of stars seem to radiate out of this core in all directions, but less concentrated toward the West.

M15 can be found extremely easily: Find the 2nd mag star Epsilon Pegasi, and Theta Pegasi SE of it. Follow the line from Theta over Epsilon and find M15 3 1/2 deg W and 2 1/4 deg N of Epsilon. A 6th mag star is about 20' away to the East, another one of mag 7.5 about 5' to the NNE".