LAS FAQ

Frequently Asked Questions

Many articles have been written on how to collimate a Newtonian telescope, with little explanation about what is going on during the process. The article at http://www.catseyecollimation.com/mccluney.html is a layman's examination of the Newtonian optical system, and how its components interact when properly collimated. Hopefully this 'behind the scenes' look will give telescope owners a deeper knowledge of the workings of their instruments.

Can anyone recommend a light pollution filter and nebula filter?

The h-Beta filter (broad-band) is good on only a few objects - the California Nebula, the Horsehead and 1 or 2 others. You need an OIII (Lumicon is the only manufacturer I know about) and a narrow-band filter (either Orion's Ultrablock or Lumicon's UHC). The OIII really makes the Veil prominent -it must have a lot of ionized oxygen. Telescope warehouse usually has these filters used at prices much less than new ones.

Anyone have any recommendations on a field power supply? Everything I need to power (mount, dew zapper, & autoguider) have cigarette lighter adapters.

Sears has a powerful one for $79.99. With an adapter that I use it will power your mount, a dew zapper and has an outlet for a cigarette lighter. I bought the adapter at Radio Shack for about $10.00. It also has jumper cables and 900 amps cranking power for jumping cars. - Pat

Go to Sears and get a Wheelchair battery. It is essentially a gel cell, and works great, you can actually go several full observing nights without recharging. I just bought a new one (my old one was shot after about 8 years), and it was $59 (with core exchange, 7 bucks more if you don't have an old battery to give them for a core). I keep mine in a little playmate cooler, and bought a 3 way 12V adapter to velcro on my tripod to attach all my goodies. -Jeremy

Check out www.solarsense.com, The nomad 300 is what I have minus the solar panel. I really like it because it has both 12v dc and AC power. - Henry

Can you tell me why we only see one "face" of the moon?

By the same mechanism that the Moon raises tides on Earth, the Earth raises a tidal bulge on the Moon. When the Moon was rotating faster in the past, this bulge was carried slightly forward of the line joining the centers of the two bodies. The Earth exerted a torque on this bulge. Because the bulge moved in the body of the Moon as it rotated, friction in the Moon removed energy from the spin and turned it into heat. Two changes in the Moon's rotation occurred:

The spin axis aligned with the orbital axis.
The rate of spin decreased until the tidal bulge no longer moved in the body of the Moon. In other words, the Moon always shows the same face to Earth.

A body that is tidally locked to its primary is said to be in a one to one spin orbit resonance, since the spin period and the orbital period are in a 1:1 ratio.

Is is possible to have more than 2 lunar eclipses in one calendar year?

My resources say that the maximum number of eclipses, solar and lunar, in a year can be 7 (either 5 solar and 2 lunar or 4 solar and 3 lunar), while the minimum number is 2, both solar. So, one would be pretty correct in saying that the average is 2 to 3 lunar eclipses a year (though one should also point out that some of these may be penumbral eclipses, where the Moon passes through the outer shadow of the Earth, known as the penumbra. This type is hardly noticeable to most folks compared to the light of a full Moon) with some years of no lunar eclipses.

Scott Miller

What are good books about astronomy?

A good book to begin with is "Nightwatch" by Terrence Dickinson. It's likely that the library or a larger bookstore would have it in stock.

David H. Levy's book, THE ULTIMATE UNIVERSE ("The Most Up-to-Date Guide to the Cosmos"), complete with THE UNIVERSE CD from Scientific American

The Practical Astronomer by Brian Jones is full of information that middle school aged kids will enjoy. It has some insights and information that may be useful for older types, too. It has an Appendix of astronomical objects: The Messier Catalog is given with coordinates and names of the objects where appropriate. There is also a section [including coordinates] of naked eye double stars, binocular doubles, and telescopic doubles (multiples). He also gives a list of variable stars.

Entering Space by Robert Zubrin looks and sounds like the type that would be technical and boring but it is not. Instead he approaches the subject with very down to earth ideas on why and how humans should travel to, explore and possibly even populate the moon, Mars, large asteroids and maybe even the moons of other planets in our solar system. He also postulates realistic ways that interstellar travel may become feasible (not warp drive -- thank you!).

What are good websites, books or groups to get us started in astronomy?

Check out the links on our web site. Monitor our Yahoo!Group and you will see that almost every time it is clear enough someone asks "Does anyone want to meet to
observe?" We have a dark site out in the "boonies" in IN (Curby ex 92 on I-64). A lot of people go out to Long Run Park and other places as well. There are people in this group that will spend as much time with you as you can stand helping you learn. A few suggestions of items to get..

A planisphere (can get it at hobby shop, planetarium, museum, or on-line ordering)- You hold it over your head and it can help you learn the sky.

The key to learning the sky is to learn how to find a few named bright stars. From there, you can expand to learn a few constellations around them and what objects are nearby. Your Autostar can help you learn some detail in the sky. But, you will still need to be able to find some (usually two) of the bright stars to get the autostar aligned. Some key stars in summer are Vega (look east and high up for the brightest star you see), Deneb(east lower to left of Vega), Altair(east lower to right of Vega), Arcturus (look west about half-way up for brightest yellowish star), Antares (south kinda low). As the year passes, different bright stars are added to this list and others move off it. Believe it or not, being able to find the North Star isn't that important for a beginner (IMHO).
Get the book "Turn Left at Orion" or/and "Nightwatch". Both are available at local bookstores. They are also available at the Louisville Public library.
Get the current issue of Sky and Telescope and/or Astronomy. Both are available at Walmart and have sky charts and things to see.

Most important advice, ask anything about the sky on our Yahoo!Group and expect to get help.

Randall Barbour

As to web site, I might boldly recommend that of the planetarium, which I maintain. Click on the link in my .sig file below and then go on to the planetarium's page to the Current Sky link. There you will find a summary of stuff to look for and some links to relevant sites you might find of interest.

And, you are always welcome to contact me personally about questions on scopes or other aspects of astronomy.

--
J. Scott Miller, Program Coordinator Scott.Miller@louisville.edu
Gheens Science Hall and Rauch Planetarium http://www.louisville.edu/planetarium
University of Louisville

What are good websites or books for science fair projects on astronomy?

The book 'Astronomy for all Ages' has some good ideas for projects. The ScienzFair web site also has many good ideas.

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