By Bill Pellerin

Houston Astronomical Society

GuideStar editor

If you look at the population of stars by color you will find that as you go from blue to white to yellow to orange to red the stars go from rare to plentiful. You probably know that star colors are given letters as follows OBAFGKM from blue to red. Does this make sense? No, not if star colors are your primary interest. Originally the classification of stars by letter was based on the strength of the hydrogen absorption line in the spectrum of the star. With that in mind the A star has a strong hydrogen line, a B star had a less-strong hydrogen line, and so on.

We’re stuck with this color scheme, and if you look at a HR (Hertzsprung – Russell) diagram you’ll see these designations (or the equivalent temperatures) along the horizontal axis. Color and temperature are the same thing. The hotter the star, the bluer; the cooler the star, the redder. A HR diagram plots color versus luminosity and it will surprise nobody that more massive stars are hotter and more luminous.

Anyway, only one in three million stars (.00003%) is an O star whereas 77% of the stars are M (red) stars. This means that for every O star there are 2,310,000 M stars. So, it’s a challenge to find an O star on the sky. If you want to see one, you won’t do better than Plaskett’s Star (SAO114146), a bright steely-blue star high in the northern sky, in the constellation Monoceros.

It’s the brightest star in a field of stars and shines like a diamond in the sky. Its sky coordinates are: RA 06 h 37 m 24 s, and DEC 06 deg 08 min 07 sec, and it shines at magnitude 6.1 so it’s easy to see in even the smallest of telescopes. Plaskett’s Star is estimated to be about 100 solar masses, one of the more massive stars in the sky. The star that you see is really a double-star, but they are so close together that you will not be able to separate the pair in an amateur telescope. According to stellar researcher Jim Kaler, while the system totals 100 solar masses the two components are 51 and 43 solar masses each, making the total system mass near the 100 solar mass estimate. The space between the stars is estimated to be about 50 million miles. The uncertainty in the total mass of the system and the distance between the components of the system is associated with the uncertainty of the distance to the system. It’s simply too far away to determine the distance using parallax measurements, so other, less accurate methods are used.

The end-of-life of stars is difficult to predict with certainty, but these are very high mass stars destined to become neutron stars or supernovae. What we can’t know is which one will reach its demise first and when it does what will happen with the other star. Perhaps nothing unusual will happen and we’ll end up with a binary black hole system.

It was discovered to be a spectroscopic binary star by John Stanley Plaskett in 1922 when he was working as director of the Dominion Astrophysical Observatory in British Columbia, Canada.

His interests included measuring the radial velocities of stars and other objects by measuring the red or blue shift in the spectral lines of the light from the object. In binary stars the spectral lines move in a periodic way that reveals the movement of the components of the star system. Plaskett died in 1941.

Compare this star with the white star in Albireo (you’ll have to wait until summer) – the white star here is a B star, slightly redder than Plaskett’s Star, and a lot more common. The other star in Albireo is a K star, noticeably orange and very common.

Bill Pellerin

Houston Astronomical Society

GuideStar Editor

My observing log is looking a bit empty these days. It’s accurate to say that I don’t live in a part of the world known for its clear skies (the gulf coast). I suspect that only a few of us are fortunate to live in places with a large number of clear nights.

What to do? What can we do when we are visited by cloudy nights? Quite a lot, actually. Let me suggest a few things.

Schedule an observation on a remote telescope. There are several telescope systems online on which you can purchase time. You can point them where you want, take the images you want and download those images to your personal computer. Generally, these systems are quite good, using telescopes, mounts, and filters, that are quite costly. Maybe you have a comparable system in your backyard, but I don’t. You can operate these telescopes in real-time, schedule observations, script observation runs on these telescopes and pick up the data (images) in a day or so. I’ve made numerous observations this way, and, although I’d rather use my own system, these systems allow me to pursue my amateur astronomy interest without leaving home. Want to do something fun? Take an image of a moving object over a period of time and stitch the images together to show the movement. I did this with Vesta in 2010. The downside of using these systems is that, depending on what you’re doing, they can be expensive.

Read your equipment manuals. Have you ever done this? If not, you may be missing out on features of your telescope, mount, or camera that will make your observing process easier and more fun. It’s easy for us to find ourselves doing what we’ve done before because that’s the way we’ve always done it. My mount has a capability of significantly improving its polar alignment built into its controller. It took some time for me to understand the process, but now that I do I use this capability to improve the mount’s tracking.

Plan your next observing session. The amount of time we actually get to spend under a dark, starry sky is often limited. Optimize your time by planning your observing. There are several computer programs that can help with this. This software allows you to create an observing list based on, say, an Astronomical League observing program. Some observers have created these lists and made them available for download. Then, the software will tell you which objects are available to you to observe on that night. If you don’t want to have a computer on the observing field with you, print the list before you go out.

If you’re imaging you’ll need to decide which filters you want to use for your object of interest, assuming a monochrome imager. You need to determine your exposure time for each filter and have in mind how you are going to process the images following the imaging session.

Read a book, or one of those magazines you’ve been stacking up. Make a serious effort to read through the astronomy magazines or an astronomy book that you’ve been hoarding for a while. If you don’t have a book you’re eager to read, get one – buy it or visit your local library to borrow it. My library even has e-books available for loan. It’s easy to get behind on your reading, so don’t let it happen. Make an effort to keep up.

Take an online class or view an online lecture or presentation. There is a lot of astronomy related material online these days. Some of it is in the form of podcasts, both audio and video. Many colleges are putting their class lectures online for all to see. There are college level courses available via audio (CDs or download) and video (same). There are audio books that you can listen to. Check those out. I have listened to an audio book on the history of astronomy several times. I can even quote some passages from the book. Still, it seems that I hear something new every time.

Process your imaging data. Do you have any images that you haven’t processed yet? Have you learned any new techniques for processing those images? Cloudy nights are a good time to work on these images, develop some new skills, and produce a ‘keeper’ picture for the wall.

Rationalize your equipment inventory. Admit it. You (and I) probably have too much equipment sitting around. What about that old, but still usable, telescope that’s been sitting in the closet for a few years. A friend of mine has a personal ‘policy’ that if he hasn’t used something in a year he gets rid of it. I’m planning on taking a telescope that I rarely use to a star party. I’ll use it for the event and offer it for sale at the end. I hope that someone else will take it home.

There are web sites that list equipment for sale, often at no cost to the buyer or seller. I’ve bought and sold on these sites with outstanding results. It’s a bit of work to photograph your equipment, create the listing, monitor the sale, and finally pack and ship the equipment to its new owner but it often a true win-win situation. You’re getting rid of something you are not using, you are getting a bit of cash, and the buyer is getting equipment he or she will use at a good price.

Wishing you clear skies.

What would it be like without stars at night? What is it we lose? Starry night skies have given us poetry, art, music and the wonder to explore. A bright night sky (aka light pollution) affects energy consumption, health and wildlife too. Spend a few minutes to help scientists by measuring the brightness of your night sky. Join the GLOBE at Night citizen-science campaign (www.globeatnight.org). The first campaign starts January 3 and runs through January 12.

Continue reading

The Astronomical League has added another observing program for your viewing and educational enjoyment. The Observe Stellar Evolution Program will introduce you to 100 objects in various stages of evolution. The program has an observing manual, packed full of interesting information along with selected celestial objects to enforce the evolutionary nature of the cosmos. By completing this program, you will have a better understanding of the Hertzsprung-Russell Diagram and how the 100 objects of this program fit on the diagram. For more information, visit the Observe Stellar Evolution Program’s web page.

By Bill Pellerin
Houston Astronomical Society GuideStar Editor

What skills do you need to have to become an amateur astronomer? It depends on what you want to do as an amateur astronomer. I was thinking about this question as I recently upgraded the operating system on my computer. Doing so involves performing backups of the computer, establishing a back-out plan if the upgrade fails, testing the system after the upgrade, and resolving the odd problems that remain following the upgrade.

Since my computer controls my telescope mount, my imaging camera, and my guiding camera I needed to be sure that these capabilities were still functional after the upgrade. But, I’m getting ahead of myself.

If your observational activities are limited to basic observing and to pushing an alt-az mounted telescope to objects on the sky using a set of paper star maps, there are a lot of skills involved. You will have to learn how the objects in the sky move (as Earth rotates) and how to move the telescope to track these objects, how to set up and align a finder, how to collimate your (reflector) telescope, how to read star maps, how to star-hop to your object of interest, and how to confirm that what you see in the eyepiece is indeed the object you intended to find. You need to know the neighborhood – you must be able to look at the sky and pick out some major constellations and stars. In some, more dense, parts of the sky it may take some time to confirm the observation. You’ll have to have a plan, and a list of objects that are available to observe on that night and you need to know what to expect to see for each object. Is the object large and diffuse, or small and bright? Will filters help you pick the object out of the sky? Which filters?

If your telescope mount has an on-board computer you have to learn how to set it up and use it. Every manufacturer’s mount has a different setup process, and you’ll have to become comfortable with the process for your system over time. The setup may require that you know your latitude and longitude. You need to be able to convince yourself that the process worked as expected. The mount that I now use has a setup process that seemed ‘backwards’ to me when I first tried it. Over time, though, the process made more sense and I can now easily perform the process without giving it much thought. It’s a matter of teaching yourself these techniques; it’s like learning how to drive a car – not easy at first. Once the setup is complete, you have to learn how to direct the telescope to objects of interest. You have to understand what to do if the object you want is not in the object list of the telescope’s mount.

Are you going to control your telescope with an external computer? If so, you need to have some computer skills to set up the computer, to install the software, and to understand how to use it. You have to establish communications between the computer and the telescope mount. You’ll have to understand USB ports, serial ports (maybe), Ethernet networks (perhaps), and all the settings in the software you use to make the communications work. It can be challenging, and sometimes your best efforts end in frustration.

If you plan to be an imager, someone who takes photos of objects in the sky, you have to learn about cameras, filters, and camera control software. Depending on your imaging requirements you may have to develop expertise on how to use an autoguider and its associated software. Your skill set will need to include the ability to process your images, whether you’re doing photometry (brightness measurements), astrometry (position measurements), or images to hang on the wall. Learning and using high end image processing software will be in your future if doing this work is your goal.

As your observing system gets more complex there is more opportunity for things to go wrong and so you’ll have to have some troubleshooting skills. You have to learn how to isolate the problems and fix them. If your computer is not communicating with your telescope mount, why isn’t it? Did you forget to connect a cable? Do you have a defective cable? Is the cable wired correctly? Is the software misconfigured? Is the mount misconfigured?

There’s no requirement that we as amateur astronomers develop skills beyond those of finding and admiring objects in the sky. Those of us who want to do more will have to learn how to do more. It’s rewarding, but it requires adding to our skill sets and making the effort to do so.

The Asterism Observing Program has been updated with new asterisms to observe. Today, 5 new asterisms were added to the list, making the total number of asterisms to choose from 114. You only need to observe 100 to get the Program’s Award Certificate and Pin. Troy and Michelle Stratton’s goal is to have 200 or more asterisms on the list to choose from so the list will be constantly updated. Those working this new Observing Program need to check the Program’s web page often to see the latest additions and Asterism List.

By Bill Pellerin
Houston Astronomical Society
GuideStar Editor

It’s that time of year, again. You may be the one looking for a (relatively) inexpensive gift for an astronomy enthusiast. Or, YOU may be the astronomy enthusiast, and you may be asked what you’d like to receive as a gift. Fortunately, there are lots of possibilities. I wrote a similar article for the Astronomical League web site in 2011, and there are no items on this list that were on the 2011 list, so check them both out.
Happy holidays to all and clear skies in 2013.
Memberships
Astronomical League — Membership in the Astronomical League is often associated with membership in your local astronomy club. Go to the organization web site, test.astroleague.org, click on the ‘member societies’ tab and see if your club is part of the AL. If so, being a member of your local club makes you a member of the AL.
You can also become a member of the AL as an ‘at large’ member. Click on the ‘join’ tab for more information on this option.
Your local astronomy club – Being a member of an astronomy club is great – you can discuss your observing projects with others, attend presentations and meetings, and learn about astronomy related events in your area. Clubs often do outreach programs, introducing the public to the joys of amateur astronomy. The club may offer other benefits as well – an observing site, loaner telescopes, or classes.
American Association of Variable Star Observers – if variable stars are (or could be) your thing, you’ll want a membership in this organization. The AAVSO provides a lot of information to observers, and collects their observations into a database for use by other amateurs or professionals. www.aavso.org.
Association of Lunar and Planetary Observers – an organization of astronomers who observe solar system objects including the Sun, Moon, the planets, asteroids, comets, and meteors. www.alpo-astronomy.org.
International Dark Sky Association – an organization whose mission is to preserve and enhance dark skies by promoting environmentally responsible outdoor lighting. Become an activist in your area for dark sky. www.darksky.org.

Books
Books always are a good choice for a cold, winter night. Be sure to specify the format – hardback, paperback, e-book, or audio book.
Coming of Age in the Milky Way – By Timothy Ferris is my all-time favorite astronomy history book. This one has been out for a while (published 1988) but the story is so good and so well told you won’t be able to put it down. An abridged audio book is still available, so you can listen to it read by the author while driving to and from your observing site.
Binocular Highlights, Gary Seronik — the book you want to have when you want to observe, you’re in dark skies, and you have your binocs handy. Contains 99 objects with maps showing you how to find them with your binoculars.
The Observer’s Sky Atlas, Third Edition (Springer), E. Karkoschka — a remarkably compact (and not well known) atlas guides you to unaided eye, binocular, and telescope objects. You can throw this compact guide into the glove box of your car and always be ready to find some new and interesting objects in the sky.
The Day We Found the Universe, Marcia Bartusiak — The history of scientific discovery leading to the determination that the universe is larger than the Milky Way. It tells about astronomers who were close to establishing the size of the universe but who never put the pieces together and about Edwin Hubble, who did.
Cosmic Challenge (Philip Harrington) — Challenge your observing skills with this book. For any size telescope. Can you see the Horsehead nebula with binoculars? Phil says you can.
How Old is the Universe (David A. Weintraub) — How did we come to know the age of the universe with such certainty? Available as a paperback, an e-book, or an audio book.
The Backyard Astronomer’s Guide (Terence Dickinson & Alan Dyer) — anything by either or both of these guys is going to be good.  This one’s a comprehensive look at amateur astronomy from just getting started to sophisticated astro-imaging

Video
The Inexplicible Universe: Unsolved Mysteries (The Great Courses) – DVD—Neil deGrasse Tyson—six lectures on things we don’t understand in the universe — great for a cloudy night.
The Journey to Palomar (PBS Home Video) – A very enjoyable video detailing history leading to the construction of the Palomar observatory, the largest telescope in the world at the time.

Troy and Michelle Stratton have put together a new Observing Program, looking at famous stellar asterisms. For details of this wonderful program, see the web page at http://astroleague.org/content/asterisms-observing-program

Bill Pellerin

Houston Astronomical Society

GuideStar Editor

If you get into a discussion about the ‘best’ telescope, prepare for controversy. The right answer, of course, is that there is no one best telescope. There are telescopes that are better for the kind of observing you are doing (deep sky, planetary, double star, etc.), but how about the right telescope for the observing conditions you’re likely to find.

Here’s my story. On October 12, 2012 I was part of a group of amateur astronomer volunteers who did a star party at the Camp for All site near Brenham, TX, about 80 miles northwest of Houston. Camp for All is designed to provide a summer camp experience for children and their families with special needs. For this event we were showing the sky to children who are cancer patients. All public star parties are a great experience, but this one is especially rewarding for the volunteers.

The weather conditions for that day were not the best, but there were some breaks in the clouds and we had hope that the sky would clear in time for observing, which was scheduled between 8:00 p.m. and 9:00 p.m. The sky didn’t cooperate – clouds came and went and while a few stars popped out from behind the clouds from time to time, there was no consistent clear sky for us.

Knowing that these were the conditions we would likely have to work with, what’s the best telescope / mount to bring? Last year, when conditions were excellent I had my computerized alt-az 8” SCT at the site. Turn it on, find two stars to set it up, and it’ll find whatever I want in the sky and track it. I didn’t have to keep nudging the telescope to keep the object in view.

This telescope was a great choice last year, but it was a poor choice for this year. It didn’t work well at all, and it wasn’t because anything malfunctioned, it was because observing conditions were different. We had a 50 to 75 percent cloudy sky at the site, with a few stars shining through (notably Vega). The SCT system requires a two star alignment, and on a clear night it’s easy to accomplish. On a night where clouds are coming and going, alignment is virtually impossible. The ‘scope slewed to the vicinity of Alpheratz, said ‘center Alpheratz’, Alpheratz went behind a cloud, and so on.

I never was able to get the telescope aligned. I was able to manually point the telescope to the double cluster and show this to a few campers, but it wasn’t visible for long. The double cluster went behind a cloud.

What would have been better under these circumstances is an alt-az mounted manually pointed telescope – a Dobsonian or some other manual mount. With that kind of telescope I could have pushed it to, say, Mizar, a nice triple star system. Or to Albireo, a lovely double star in Cygnus. (Ok… I could have manually pointed the SCT as well, but it doesn’t lend itself to manual pointing easily.) I would, of course, have had to nudge the manual telescope from time to time.

So… what are the characteristics of a good telescope for these circumstances? The advantage to a computerized and motorized telescope is that it finds objects for you and it tracks them for you. Less fiddling is required during the observing session. This works if the sky is clear enough for you to get a good alignment. The advantage of a manually pointed telescope is that you can point it anywhere, easily, by hand and no alignment is necessary.

My conclusion: The best public star party telescope, especially if observing conditions are iffy, is one which can be manually pointed if necessary but has some pointing assistance capability if the sky allows you to do an alignment. I have an alt-az telescope mount with encoders and a small (deck of cards sized) push-to computer. If I can do a two star alignment, the push-to computer will tell me which direction and how far I have to push the telescope to get the telescope pointed to an object in its database. If I can’t do a two star alignment I can simply push it to some object I already know. I use a small wide field refractor with a on this mount so that the number of telescope nudges is limited and the distance I have to move the telescope is limited. This setup obliges me to select objects that show well in such an instrument, but there are plenty of those. Look in books and magazines for ‘binocular objects’ – these make great wide-field instrument objects.

I could have showed the kids some bright double stars (where the clouds cooperated), perhaps the Andromeda Galaxy, a bright cluster, or a planet (had there been any in the sky on that night).

The key to public star parties is to show the public some bright objects, have a story to tell about the object (how far, what color, the evolution of the object, etc.), and wait for questions. Be prepared to show where objects are in the sky with your green laser pointer and teach the observers about the object.