St. George Astronomy Group
The St. George Astronomy Group is an informal association of amateur astronomers in St. George, Toquerville and other nearby communities in southwest Utah.
The group was formed to (a) exchange ideas and
foster fellowship among people with an interest in astronomy, (b) to host
public star parties, and (c) to promote proper lighting and dark skies over southwest Utah.
are no officers, dues, or formal meetings. Membership is open to anyone who
wishes to actively participate in hosting star parties and working for dark
skies over St. George.
People who wish to know about the group's public activities can join our mailing list, or check the Calendar.
We have had a busy summer so far and more public outreach events are in the planning stages.
Nancy and I have always been interested in astronomy. However, work and family seemed to occupy all of our time during our working years.
After retirement, we found that we had time to become involved in astronomy. We found a good used telescope and learned how to use it. We really like public outreach and have participated in star parties at the National Parks whenever we have the chance. Some of our astronomy friends that live nearby suggested that we should get involved in the scientific side of our astronomy hobby.
We attended a symposium put on by the Society For Astronomical Sciences (SAS) (http://www.socastrosci.org/). At the symposium we met Dr. Russ Genet who told us about a double star workshop that was being held in Apple Valley, California. Russ recommended a book “Observing and Measuring Visual Double Stars” by R.W. Argyle (Editor). Dr. Genet pushes double stars. If you do a Google search on “double star” his name will come up on most of the meetings and most of the published papers on the internet.
I found that Springer had the book for half price, so I bought the eBook edition and started reading.
Double Stars seemed like something we could do. We found that there are over 100,000 binary stars listed in the latest Washington Double-Star Catalog (WDS), but fewer than 2,000 have “well-determined" binary star orbits.
The Naval Observatory has a list of "neglected" binaries. These are star systems with separation >3 arc-sec and brighter than 11th magnitude (hence most are within the range of a careful amateur astronomer) that have not been measured for more than 20 years. The "neglected binaries" list contains over 6,400 star systems. Professional astronomers do not have the time to take the double star measurements and the Naval Observatory is counting on amateurs to make observations, and report as much data as they can.
The International Association of Double Star Observers (IADSO) and the High Desert Astronomical Society (HiDAS) held a three-day, two-night double star workshop on June 13 – 15, 2013. The workshop was held at the Lewis Center for Educational Research (LCER) (Thunderbird campus) in Apple Valley, California (http://www.jdso.org/volume10/number2/Brewer_160_164.pdf).
At the workshop we were introduced to the various methods of measuring double stars. The methods covered were: the use of an astrometric eyepiece, video drift method using a low cost video camera, the Lyot double image micrometer, and a CCD camera mounted on a telescope. We also found that light pollution, and moon light, is not a problem with most double stars. The Lewis Center is right behind the largest shopping center in Apple Valley, California. The sky to the south was really bright. Yet all the teams were able to capture and measure double stars.
I had purchased an astrometric eyepiece so I wanted to learn how to use the eyepiece to measure double stars. We joined the astrometric eyepiece team and spent two nights observing and taking data. Here is a picture taken of Delta Cephei through the astrometric eyepiece during one of the runs.
At the workshop Rick Wasson, from Murrieta California, gave a paper on using the Video Drift Method to measure double stars. Rick main focus is Asteroid Occultations, but he had read a paper that the same hardware could be used for double star observations. Rick uses an Orion 12 inch f/4.9 Dobsonian telescope, with a video camera in place of a 1¼” eyepiece. The video camera cost less than $100. A Canon camcorder recorded the digital video stream on cassette tape. All the software that Rick was going to use was "freeware". While we did not have time to observe with Rick and his team at the workshop, I was interested in learning his method. I gave Rick my card and told him if he needed any help to give us a call.
Rick picked Epsilon Lyrae, a famous Double Double star for his video runs. Ordinary binoculars shows Epsilon Lyrae as a double star. But a closer look through a telescope reveals that each of the two stars in the Epsilon Lyrae system is, in itself, a double star. That’s why Epsilon Lyrae is famous for being the Double Double star, a single point of light to the eye that’s really four stars in one. One stellar pair circles around the other stellar pair in an intricate gravitational dance.
After the workshop, Rick called Nancy and I and asked if we would try some of the data reduction. Since we both had worked with a lot of software in our careers, we said we would give it a try. Rick gave us four video runs to analyze. Rick did a great job writing a procedure for reducing the data from the video runs.
One of the major problems with free astronomy software is the steep learning curve that is involved. There are four software programs that are required to process the video files. The software was difficult at first. I gave Rick a couple of phone calls when we were not sure about something. Once we figured out how the software worked, processing the files went pretty fast.
After a few months only one person on Rick’s team had submitted any data. Rick asked if we would do the rest of the video runs so he would have data to publish his paper. We finished up the rest of the video files. We processed a total of 9 video files for each pair of stars.
After all the drifts had been analyzed, Rick discovered that all the frames had been “stretched” 12.5% horizontally. So we started searching for the error.
The video camera that Rick was using to record the video runs has a CCD chip that had rectangular pixels and not square pixels. I found some software that would look at the header file of the AVI video files. The camera has a CCD chip which is digital. The output of the camera is an analog video stream. The video stream was recorded on a digital recorder (converted from analog back to digital). When the recorder records the video, the video was converted to square pixels. Then the digital stream was imported into the computer. Each time the file was copied and saved, the header would change the aspect ratio of the video chip. After we identified the source of the error, we calculated a correction factor for the camera and applied it to the data.
Richard L. Nugent and Ernest W. Iverson were also using the video drift method to measure double stars. Nugent and Iverson, who were pioneers in the video drift method, came up with a very simple solution to the video problem (http://www.jdso.org/volume10/number3/Nugent_214_222.pdf). Their simple solution is to use a “Calibration Double Star” for one time calibration of the equipment. The Calibration Double Stars have a known Separation and Position Angle.
Nugent and Iverson calibrate their recording system by adjusting the image aspect ratio until it matches the real sky. This calibration procedure only needs to be done once, and is valid until the hardware in the video path changes.
Nancy and I worked with Rick to get paper finished and ready for submittal to “Journal of Double Star Observations (JDSO)” published by the University of South Alabama. We knew that the paper would be peer reviewed, and that the editors of JDSO, and an umpire would also review the paper. Many hours were spent carefully wording each paragraph, we wanted to make sure the paper did not get rejected. The paper was accepted with out any changes and was published in the January 1, 2015 “Journal of Double Star Observations” (http://www.jdso.org/volume11/number1/Wasson_36_41.pdf).
There was a lot of work involved in producing this paper, but we really learned a lot.
We encourage anyone who has an interest in double stars or an interest in doing some “science” with their astronomy equipment to attend a workshop, join a group like the “International Association of Double Star Observers (IADSO)”. The IADSO membership is free.
If you are not interested in double stars, but would like to find some of the other opportunities for amateurs to make a contribution to science, there is a great book by Robert Buchheim, “The Sky is Your Laboratory, Advanced Astronomy Projects for Amateurs”.
While we like the challenge of doing science with our telescope and learning new things, we still really like public outreach. When someone, young or old, looks through our telescope and sees: the rings of Saturn, the moons of Jupiter, a star cluster or a double star, it is very gratifying.
Total Eclipse of the Moon
Early Saturday Morning, April 4
Residents of St. George and surrounding communities – and the western United States – who get up early on the morning of Saturday, April 4th will be treated to a total eclipse of the moon. No special equipment is needed to observe one of nature’s more interesting spectacles. Merely step outside and look up.
An eclipse of the moon happens when the moon moves into the shadow of the earth and grows dark. This can happen only at full moon, when the moon is opposite the sun in the sky. Usually the moon’s orbit takes the moon above or below the earth’s shadow, but if the alignment is just right the moon can move into and through the shadow, and the moon grows dark as sunlight that would fall on it is blocked by the earth.
The eclipse officially begins at 3:01 a.m. MDT on the morning of April 4th when the moon’s left edge begins to move into the outer (penumbra) part of the earths’ shadow, but in practice the moon won’t begin to darken noticeably until after 4 a.m. By 5 a.m. the darkening will be obvious to the casual observer. At 5:58 a.m. the moon moves fully into the inner (umbra) part of the earth’s shadow and totality begins. Totality lasts only 5 minutes and ends at 6:03 a.m., when the moon begins to move out of the central part of the earth’s shadow and brighten once again. By then the sky is already becoming quite bright with the approaching dawn. The moon sets while still eclipsed.
The best strategy is to set your alarm for 6 a.m., step outside, and enjoy the free show. Note that the moon is very low in the west and it is essential that you have a clear view of the western horizon.
The moon darkens when in the earth’s shadow, but it doesn’t disappear. Sunlight refracted around the edge of the earth and through the earth’s thin atmosphere, falls on the moon, and this refracted sunlight is reddened for the same reason that sunsets are often red – red wavelengths of light penetrate the atmosphere better than other wavelengths. The moon usually takes on an orange or red color that is caused by light from all the sunsets and all the sunrises of earth!
If you were on the moon at this time, you would see the earth move in front of the sun in a total eclipse of the sun. Perhaps future astronauts will see such events from their lunar bases.
No special equipment is needed to see a lunar eclipse, although binoculars or a small telescope will enhance the view. The moon will be very low in the western sky (altitude only 15 degrees), so find a place with a clear view to the west.
While watching the moon pause to notice the bright star Spica 10 degrees (the width of your fist held at arm’s length) to the left of the moon and the star Arcturus well above the moon. Farther to the left is the red star Antares and above and to the right of Antares is the planet Saturn.
The eclipse is visible simultaneously from North America roughly west of St. Louis. Adjust for the local time zone if necessary.
Because of the early hour the St. George Astronomy Group (SGAG) will not hold a public observing session to view this eclipse. View it from your own home.
The next total lunar eclipse visible from St. George will happen on Sunday, September 27, and because it will take place during the early evening hours it will be widely observed.