May 2015

Financials:

No activity during the month.

Beginning balance April 1 and ending balance April 30 $1859.67

Have 33 paid memberships; 3 of those have more than one member; member total is 36

We had 20 people this evening, including 2 guests (a father and son)

Pre-program:

We watched two interesting videos on how the speed of light was theorized and calculated. The first explored the idea that light moves through space with finite speed (comparing visibility in time of Jupiter’s moon Io to Jupiter itself) and the second focused on the math calculations done by French physicist Fizeau in 1850.

Astronomy news:

No Picture of the Month this month

But you can see plenty of neat pictures courtesy of the Hubble Telescope’s recent 25th anniversary!

Upcoming possible events for the BAS:

Dewey schools:

The club has received a request from Darcy Swanson w/Dewey school system for a star party or other event. She has asked if we do school visits. Virgil will check this out—not sure if she wants an outdoor event, or indoor presentation, or both.

Member Observing Program:

We need for someone to volunteer to head up the “Member Observing Program”. This would include star parties, school visits, etc., and would encompass both a knowledge of and way to track down what special events might be able to be seen on a particular night, and also the more earthly arrangements—trees in the way? Lights? Is the site accessible? Do we need permits? What might the weather be, etc?

If no single person is willing to take this on, an alternative was brought up that we could subdivide by event. Or possibly work in a team of two for a single event—one to handle the more heavenly logistics and one to work on the more earthly ones.

Sunfest:

Denise has registered the club for Sunfest. Sign up sheets for Friday, Saturday and Sunday. May 29-31 were passed around. Some spots still available. (Denise will send out a separate communication to the club membership on these.) Denise has the number to call for weather updates—918-333-0456—in case there is a cancellation of some Sunfest time slots due to weather.

Star party for OU Tulsa:

Rick Bryant with OU Tulsa (who did a great astrophotography workshop last Saturday night!) said that the 3 OU campuses are planning a celebration for the 400th anniversary of Galileo demonstrating that the earth circles the sun, not the other way around. There is the possibility our club could plan a star party this fall for OU Tulsa.

April Girl Scout event at Wah-Shah-She:

Denise and John Grismore (with telescope) were to have attended but this was called off due to weather. Denise will hear from Doug Napier (her Girl Scout event contact) about future events—Doug said they will plan one for late September or October when hopefully the weather should be good.

Club board meeting:

To be planned for next week (Thursday), possibly at the Lutheran church in Park Hill where the astrophotography workshop was

Club telescopes:

A good place to store these is needed

Telescopes for sale:

Don Fudge, one of our members, has 3-4 scopes to sell. He said we could see them on Cloudy Nights in the classified section. One is a 12 inch Apertura with manual setting option and another is a 10 inch Dobson Skyquest.

Daryl’s sky report:

Watch Orion in May

Eta Aquarid meteor shower is on May 5 and 6, peaks before dawn May 6, but weather will probably limit visibility

Saturn will rise early May 5, 2 degrees from the waning moon in the southwest

An occult of the moon with Moon with Aldebaran in Taurus is coming up but will probably be below the horizon (from here)

May 23 Saturn will be in opposition with rings tilted to the max. Saturn will rise after sunset.

Globular cluster Omega Centauri (largest globular cluster visible to us) is barely above the horizon to the south. Better viewing in the U.S. would be some place like Galveston.

Main program: Early history of BAS and Grinding a Telescope Mirror by Fred Frey

Fred is a founding member (or very close to founding member) of the BAS when it got started in 1958-59 with the Moon Watch program of the late 1950’s in response to Sputnik. They were a group of citizen-scientists who made their observations in a field which we think is where Food Pyramid now is.

Fred has made probably 12-15 telescope mirrors through the years. He brought a number of books with him about making telescopes.

Two of them are:

How to Make a Telescope by Jean Texerau, 2nd edition, published by William-Bell, 1984

Making Your Own Telescope by Allyn J. Thompson, published by Sky

Another he recommended is:

Standard Handbook for Telescope Making by Neale E. Howard which can be found on Amazon

His presentation was not so much a step-by-step detailed how-to presentation of grinding a mirror as a discussion of different aspects of that process.

Grinding a telescope mirror involves smoothing the surface, polishing, testing, and configuring. In the past he has gotten glass to make one from Corning Glass Works.

Telescope making has advanced through the years. If you want to make one now, don’t make it if you can buy the type you need. Only make one if it serves a specific purpose for which you can’t buy one ready-made, such as a planetary 6 inch F12 that would have a pretty wide field. Don’t check out a book from the library with the idea of making a telescope in two weeks—buy a book!

F = ratio of diameter of lens to focal length

There are several systems for grading abrasives. Microgrit is measured according to the diameter of particles in micros. There are also differences in the grinding strokes you use. Abrasive grains make cracks in the glass as you work. In the smoothing process, you want to grind a mirror to a certain depth. It helps to hold a straight edge over the mirror and fit drills under it to see how deep the curve is. You use finer and finer abrasives until the surface is as smooth as you can get. You mark the largest pit you can find made by your abrasive with masking tape and keep grinding with a finer abrasive until the earlier pit disappears. It takes about an hour to go from one level of grinding to another. In between each stage of grinding, clean your tools very carefully and put paper towels between everything. You may need to replenish abrasives every 5-10 minutes, depending on the level of grading that you are at. Daryl suggested getting a 55-gallon drum and rinsing everything in to the drum. Always then wash your hands. Your mirror should always be face down. In the final stage of smoothing, polishing grains will become lodged in pits. For a 6-inch rouge mirror it will take 4 hours to polish out the pits. You may need to get help with curve-generating. You can reach the William-Bell company at 1-800-825-STAR. You can approximate curvature if you do rough grinding and then step back, moving your light source to check curvature radius. Light will go in the opposite direction. You have to wet the mirror first to get a reflection.

For the pitching process the mirror must be wet. You have to put channels in the pitch with a soldering iron and silicon grease. Tilt the mirror so drippings will go on your paper towel below. Lay out positions of channels with masking tape. You don’t want your soldering iron to get so hot that it will burn.