October/November 2001 Issue

From the President's Desk

by Greg Sellek

Well, I'm glad to see the newsletter again. Thanks go out to John Rummel for putting this edition together in such short time. With John's time at a premium, we hope to have a full-time Newsletter Editor soon.

Things at YRS are looking up. The new 12" LX200 in the AKO is installed and running. Doc has been putting quite a bit of time into the new dome and scope, and before long we will have a semi-automated facility. I also wanted to thank Doc for his time and effort in getting the LX200 in the Doc G. observatory fixed. The 16" scope in the KMO is also almost fully operational and interested observing members should speak with Tim Ellestad for further details.

The Minor Planet Project has been temporarily put on hold while the work continues on the LX200's. But, Matt Mills and I had been regularly submitting observations to the Minor Planet Center, and had just gotten down to some real science. We could always use another set of eyes, and I would encourage anyone interested to contact me.

One last item I would like to discuss is public outreach. I feel that as a club it is very important for the MAS to get out there and present itself to the public. Too much of our time together is spent in lighted rooms. Why not spend some time doing what we're really in an astronomy club to do, astronomy? Heck, as long as we're at it, let's invite a few friends, or even a few strangers. If anyone would like to sponsor a public event, or just has an idea of how MAS could better reach the public, please feel free to bring it up at the next meeting.

 

Calendar of Events

October 12 MAS monthly meeting, Space Place (1605 S. Park Street, Madison), 7:00 new member welcome and board meeting, 7:30 main meeting. Presentation: David S. Liebl, UW - Extension, giving a talk on "Progress in Controlling Light Pollution in Wisconsin."

October 17 MMSD Planetarium Public Show (Memorial High School, corner of Gammon and Mineral Point). Shows 6:30 and 7:45 pm. Special Mars Show, learn about the recent amazing discoveries made by the Mars Global Surveyor, and learn about the Mars Odyssey probe, which will arrive at Mars on October 24th.

October 19 - 20 MAS observing campout at Wildcat St Park. Contact Greg Sellek at orion98@home.com for info or to make your reservation.

November 9 MAS monthly meeting, Space Place (1605 S. Park Street, Madison), 7:00 new member welcome and board meeting, 7:30 main meeting. Presentation: Jim Lattis speaking on Giuseppe Piazzi (discoverer of first asteroid).

November 28 MMSD Planetarium Public Show (Memorial High School, corner of Gammon and Mineral Point). Shows 6:30 and 7:45 pm. Explorers of Mauna Kea, the story of the greatest astronomical observatories on Earth, and why an extinct volcano in Hawaii is one of the best places on Earth to do astronomy.

 

New Members

MAS welcomes the following new members since June, 2001:

Mike Becker, Brianna Benson, John Foley, Aaron Goldstrohm, David Kettleson, Charles Paulson, and Ron Weber

 

Editor's Note

Yes, I'm back. Just two months after retiring from the editorship of MAS' flagship publication, I'm back for a few more issues, mostly because MAS desperately needs this communication with its members.

We still need somebody with desktop publishing experience to take over this job. We have had some interest. John Quigley, who's excellent article on occultations appears in this issue, has volunteered to help out, and possibly take over the layout work at some point in the future.

To continue, the newsletter needs your participation. This issue is only six pages rather than the usual eight because of a lack of material. Many club members are engaged in activities that are worth hearing about. Whether it's observing visually with your small backyard scope, or taking digital images with a camera of your own making, consider writing it up and submitting it to this publication. -JR

 

 

Viewing an Occultation

by John Quigley

Tuesday, July 17 saw a unusual gathering of skygazers at the UW Space Place. Whereas most astronomical events are viewed at night, they had come to observe a daytime event: the occultation of Venus by the waning crescent moon. Because of its brilliance Venus is visible through binoculars and even with the naked eye during the day under favorable conditions. Fortunately skies were mostly clear as Jim Lattis of the Space Place brought out telescopes for a dozen or so visitors to follow the occultation closely. They were able to record the moment of the planet's disappearance behind the moon, and Lattis was at the eyepiece more than an hour later when Venus suddenly reappeared on the other side of the moon. Personally I arrived too late to see the disappearance but I was able to note its reappearance through binoculars.

This event led me to undertake a little research into occultations in general. Any occultation of an inner planet (Venus or Mercury) will be observable from a swath that lies predominantly in the daytime-hemisphere of the Earth. This arises from the geometry of the solar system - Venus and Mercury always face mostly the daytime-side of the earth, just as we on Earth see mainly the sunlit sides of the outer planets.

An important feature of occultations is that when a solar system body occults an object that is a point-like source in comparison (such as a star), the "shadow" cast by the body is essentially the actual-size profile of the body itself (as projected on the curved surface of the Earth). In the case of the moon its diameter of 2150 miles can cause an occultation to be visible in a range stretching from Canada to the Gulf of Mexico, as happened on July 17.

On the relatively rare occasions when a large planet such as Jupiter or Saturn occults a star, the event could easily be visible over the entire hemisphere of Earth facing the planet.

Of special interest are occultations of stars by asteroids. When observed and timed by teams of observers (usually amateurs) spread out along the occultation path, they provide scientific data about the size and shape of these minor planets. Some of these asteroids are too faint to be seen directly in amateur telescopes – the observers simply note the times that the star in question "winks out" and when it reappears a few seconds later.

Occultations are observed to try to detect other phenomena as well, such as dark ring systems on outer planets, atmospheres on other solar system moons, companions of asteroids, and tight multiple star systems.

An guide to lunar occultations of brighter objects, with a page devoted to illustrations, is found in the annual Astronomical Calendar by Guy Ottewell. Each January issue of Sky and Telescope has an article with more detail about lunar occultations, while the February issue covers occultations by other solar system bodies (mostly asteroids).

An organization, the International Occultation Timing Association (IOTA), is devoted to the study and observation of occultations. It has a web site: www.lunar-occultations.com/iota.

From North America's point of view the next easily viewable occultation will occur on the evening of November 30 when the nearly-full moon covers up Saturn. Though the moon will be very bright the planet will then be better than zero-magnitude and possibly visible to naked-eye viewers right up to the moment of disappearance. According to the IOTA web site, in Madison Saturn will disappear at 6:51 P.M. and will reappear at 7:28 P.M.. Times will vary from those above according to your specific location.

 

MAS Telescope Scholarship

Each spring, MAS awards a scholarship telescope to a young aspiring amateur astronomer. AJ Carver, our first recipient, is now a senior at Memorial High School, and secretary of the MAS. Our current honoree, Ben Hastil, is enjoying the 8-inch Dobsonian telescope, eyepieces, and astronomy library that are part of the scholarship, from his backyard dark-sky location near Brooklyn, WI.

As MAS looks toward the spring of 2002, it's time to start spreading the word about this award, and getting interested youth to apply. If you know somebody who may be interested in applying for the scholarship, have them contact John Rummel at darksky25@home.com. Membership in the society is not required. Applicants have only to submit a short essay describing their interest in astronomy, and how they plan to make use of the telescope for the year it would be in their possession.

 

Campout at Wildcat Mountain State Park

Members of the Madison Astronomical Society will be holding a group campout event at Wildcat Mountain State park the weekend of October 19th. The park is located near Ontario, WI and is rumored to have some of the darkest skies around.

There is room for up to 75 people at our reserved group camp site, and so far we only have 10 people signed up. The cost is $30 per night for the whole site, so the more members we have attend, the cheaper it will be. I have also heard that if we can get Tim Ellestad to sleep in a tent, Mary will pick up the tab!

Please e-mail me at orion98@home.com to make your reservation! We can cancel our reservation up to four days in advance, so a final go / no-go will be given on October 15th.

Astronomy Camp 2001 - Advanced Camp

by AJ Carver

Asteroids, like most celestial objects, rotate. At the University of Arizona Advanced Astronomy Camp this past June, I participated in a research group to determine the rotational-period of asteroids. Asteroids, also known as minor planets, are often found between the orbits of Mars and Jupiter. They can be as large as 1/3 the size of Pluto, but almost none are bright enough to be seen from Earth with the unaided eye. Like all solar system objects, asteroids shine by the reflected light of the sun.

The method which we used to determine the rotation of asteroids was to take photometric readings using telescopes and photometers. Basically a measure of the intensity of light from an object, these photometric readings can reveal a pattern - and period - of any variation in the intensity of the light over time. By then examining the pattern of this light curve, the rotational period of the asteroid can be inferred.

The intensity of light from an asteroid can vary in two ways. First, there can be differences in the surface albedo, that is the amount of light reflected by different areas of the asteroid. Imagine a basketball, on which we have painted a large white dot. If we record photometric data as the basketball spins, the intensity of light would increase when we are looking at the painted side as opposed to the unpainted. Secondly, the intensity of light can change if the asteroid has an odd, non-spherical shape. Imagine a baseball bat shaped asteroid rotating in such a way we see the long side at one time and the end at the other. The long side would reflect more light back to the photometer compared to end of the bat.

At the astronomy camp my group used a 40-inch reflecting telescope with photometer, which measures light intensity. The observatory was at an elevation of 9,200 feet on Mt. Lemmon in southern Arizona.. After plotting an evening's worth of data our group was very excited. We seemingly had a good start to our research. Unfortunately the following evening's weather did not allow for additional necessary long duration photometric measurements. The data we were able to collect translates into a curve very reminiscent of a sine function. While this could be indicative of a light-curve, we cannot be sure that this is representative of a portion of the asteroid's rotational period since other factors cannot be ruled out without more data. For example, it may be possible that the sky as a whole was either brightening or darkening. Additional data would be needed to eliminate this and other possibilities.

Even though I wish our group could have done more to determine the rotation of asteroids the process was an excellent learning experience. Using professional grade equipment with a group of people who share a common interest provided an amazing opportunity to see how science really works.

 For sale:

AstroPhysics 105mm f6 refractor (new), with 400GTO mount, tripod and accessories. Contact David Liebl, 265-2360.

 A note from your treasurer

Your MAS membership renewals were due September 14th. If you've already paid - Thanks. If not, please do so soon. This is especially important if you have any subscriptions because I send in the renewals for those in October. Your prompt response helps me a lot.

Thanks again. Mary Ellestad

 

A CCD for MAS?

–purchasing options for acquiring a digital imaging camera for the society

by Greg Sellek

As many of you may already know, I have been using a CCD camera at Yanna Research Station for almost a year now. I have become fascinated with the use of such a device,  not only for our research into minor planets, but with simple imaging of the many faint fuzzies I have seen so many times though the eyepiece. Matt Mills and I have made great progress in perfecting our minor planet searching techniques, and we are frequently submitting our data to the Minor Planet Center. I have also seen others take fantastic images their first try with the CCD. Although I am very grateful to have the use of the CCD camera which is currently on loan to me, the fact that it does not belong to me or the club limits its general use by observing members.

 A recent set of donations from Dr. Greiner has given the MAS a second 12" LX200 and an automated dome at Yanna Research Station. This presents the MAS with a perfect opportunity to create a semi-automated CCD imaging facility. With the addition of a CCD camera owned by the club, we could truly introduce our observing members to the joys of CCD imaging, whether it be for fun or research.

 I am not by any means saying that MAS is required to buy a CCD camera. Instead, I would like to present the membership with the possibility of acquiring a camera and see if other people feel that having a permanent camera available for all observing members would be a good idea. In the hopes that the majority of the membership would support such a goal, I have prepared a list of three CCD cameras which I think would be best suited to general imaging on the 12" LX200. Each has its unique advantages and disadvantages, and I will try to list those to the best of my knowledge.

My top candidate is the LISÄÄ Color Megapixel CCD camera. It is a new addition to the CCD field and is yet untested among the imaging community. However it boasts the ability to take a color image of any object in a single exposure. This is an amazing feat among CCD cameras. It also has a large CCD chip, giving a large field of view of the sky. Its major disadvantage is that it is less sensitive than a black and white CCD camera and has no built-in autoguider. The Lisaa Color Megapixel is currently selling for about $2500.

 The second choice is the SBIG ST-8E. This camera has been available for several years and has proven to be the workhorse of many CCD operations. It has a large pixel array giving it a wide field of view. Used alone, it is a B&W camera, but with the addition of a color filter wheel (CFW-8), it makes color images possible by combining images taken through  red, green, and blue filters. It also has a built-in autoguider. Its main disadvantages in my opinion would be its cost and larger learning curve for color imaging. The ST-8E is currently priced at about $6000, with the CFW-8 costing an additional $850.

 The AP7p by Apogee is the most sensitive camera among the three. According to several ex-users of the ST-8E, this camera increased their imaging capabilities by 1 to 2 magnitudes on a 12" scope. It has a smaller pixel array than the ST-8E and the color megapixel camera. It's cost is similar to the ST-8E at around $5500. It has no built-in autoguider.

Recommendations

 Considering the overall use of a CCD camera, I would have to choose the LISÄÄ Color Megapixel camera as the camera of choice for the club. Its low cost and ease-of-use in obtaining color images would seem to be ideal for the beginner or intermediate CCD users. The loss of some sensitivity could be compensated for by taking slightly longer exposures. The ST-4 autoguiding CCD camera donated to the MAS by Dr. Greiner would serve as the autoguider for this configuration.

 If the club decides that a CCD camera for use by the observing membership is desirable, funding for such a camera would have to be discussed amongst the membership at large. I would hope that funds could be generated though donations to the MAS, but purchasing the camera outright might be discussed as well.

 I believe that CCD imaging is part of the future of amateur astronomy. While some of us will always be content to look with our own eyes, others will want to capture the details that a CCD camera can provide. I know that some of you may feel intimidated by computers and thus be hesitant to try your hand at CCD imaging. However, I assure you that once the equipment is setup properly, imaging with a CCD camera is fairly easy to do. 

I would encourage everyone to do their own research into the various CCD cameras available. If you feel that I should have included a camera that was omitted, please let me know. In addition, I would be happy to answer any questions you might have.


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