Auburn Astronomical Society E-Newsletter
February, 2001

In this Issue

February Meetings January Events Astronomy Day 2001
For Sale Member News  SCT Notes


February  Meetings

This month’s meeting will be on Friday, February 2, at 8:00 PM in room 215 of the Aerospace Engineering Building.  Montgomery car-poolers should meet at my house (518 Seminole Dr.) and be ready to head for Auburn at 7:00 PM. 

This month’s star party will be on Saturday, February 24.  Location to be announced.

January Events

Following our meeting last month, Robert Rock gave us an under the stars (and plenty of artificial lighting) demo of his latest acquisition – a 60mm Meade ETX 60AT Go-To refractor.  For a complete review on this hi-tech, entry-level telescope, go to Rod Mollise’s Web Page  and scroll down to:  Skywatch Back Issues and  Download the November -December 2000 (swnov00.pdf)

The weather did not cooperate for our January star party.  Host, David DiPofi writes:

I was not a good night for a star party. It was very cold and overcast until about 8pm. One guy from Auburn showed up after dark but did not stay. Perhaps another time.

Astronomy Day 2001

Rick and I were wondering if we could count on the Auburn Astronomical Society to help out for this year's Astronomy Day Event. Astronomy Day is on April 28th this year. We plan to make it an afternoon and evening event....and I'm guessing that we'd start at 1:00 pm for those persons out in the park wanting to take peek at the Sun, etc. 

I've only attended a few Astronomy Day Events in the past, and actually haven't planned them. I'm trying to line up guest speakers from Marshall Space Flight Center and we are also toying with the idea of having an Astronaut Appearance. We are still in the early stages of planning so anything is possible and we're trying to act early. Any additional information you may be able to provide is greatly appreciated. 


Mark Brown

Astronomy Day has traditionally been our best attended event each year.  Let’s hope for a repeat this year.

For Sale

This is a 150mm compact Newtonian telescope, w/ 1000mm focal length, f/7, Standard 1¼" Accessories Include: 20mm Plössl Eyepiece (50x) and Focuser, 6x30 Finder scope, CG-4 EQ Mount, Sturdy, Adjustable Aluminum Tripod with Accessory Tray & Tripod Level built in, Weight 28lbs.Also Included: Moon Filter ($15), Orion Collimation Eyepiece ($35), Orion  2X Barlow ($40)Very Portable All $415/BEST OFFER
Contact Rick Allen  334-821-1714

For more information try:  and


LX 50 EMC - 10" SCT. I have used the scope approximately 5 times. It is like new and I have the original box. It comes with wedge and tripod. I simply do not have time for viewing.
Sid Williams

Member News

Rick Allen writes:

I met Mark Brown at the Gayle Planetarium yesterday .  I was one of the parents with the 2nd grade class from Lee-Scott.  We had a great visit to the planetarium and all enjoyed the show

Eddie Kirkland writes: 

The trip to Arizona was great.  Beautiful dark skies; so many stars I could hardly discern the constellations (really!).  My new refractor performed very good on DSO's; not planets at that time [last spring).  I got the scope vendor to replace the lens cell after the trip and this one is MUCH better.  I've been viewing Jupiter and Saturn lately and the views are very nice (my 8" Dob is still better though). 

From Phillip Hosey

 Well, I'm officially out of the hobby of astronomy now.  I sold all my gear.  It's been fun but I had to leave.  I have enjoyed the star parties and the conversations we've had.  Maybe I am a little flaky, but I think mostly it's just that I have other interests that I can focus my energy on that don't require me to wait on the weather or the moon :)  Anyway, I wish you well and hope you have plenty of clear skies in the future.  You can call or email me anytime if you ever want to chat.

SCT Corrector Plates

Our good buddy, Rod Mollise, of the Mobile Astronomical Society, who, among his other talents wrote the following in response to a query from a member of the SCT-User’s mail list on Schmidt-Cassegrain corrector plates.  Perhaps you’ve wondered the same thing:

 What is the purpose and function of the corrector plate?  What does  the corrector plate correct?  Lecture please.
 David S Smith
Rod replied:
HI David:

The primary mirrors of SCTs are spherical. Fast spheroids like these  (f/2) are relatively easy to make well in a mass production (or any other) setting. Unfortunately, you cannot leave a telescope mirror a sphere--if you do, you have the "Hubble Disease," spherical aberration. All rays of light do not come to focus at the same point, much energy is thrown into the diffraction 
rings,  the scope will never be able to be focused properly , and will not deliver the resolution that it should. 

The solution in SCTs is the corrector plate, a thin, complex lens that "corrects" for the spherical aberration. A convenient way to look at it, especially if you're, like me, not exactly a guru when it comes to optical theory, is that the corrector introduces the OPPOSITE degree of spherical aberration into the system, the corrector and the primary "cancel out", and all is well! :-)

On the same subject, wrote:

… expense of grinding a piece of glass to the complex shape of the corrector.   If this is correct, then don't the two costs offset each other, making it  equal in cost (and better optically) to create a non-spherical primary  mirror -sans- a corrector lens, and would this be an equally expensive  plain-old "Cassegrain" design?
 Rod continues:
Remember, we're talking a mass-production setting, where the goal is to eliminate as nearly as possible labor intensive activities that _have_ be carried out by humans, _such as parabolizing a mirror_. Both Meade and Celestron have developed similar methods of mass producing correctors (based on Schmidt's original method of applying a precise vacuum to a corrector plate, grinding it flat and releasing the vacuum--resulting in just the right curve). This, in effect, means they can _spit 'em out_! 

IMHO (I'm a little biased:-)), the SCT design is superior in every way for general use to all the Cassegrain designs (Classical, Dall-Kirkham, etc.), with the possible exception, for astrophotographers, of the Ritchey-Chretien.

Rod Mollise,
Moderator, sct-user, The mailing list for CAT fanciers
(MCT, SCT, and MNT fanatics!)

If you’d like to learn more about SCT’s go to .
After getting yourself a “Yahoo! I.D.”, and choosing a password, cruise on over to the “Files” section and look for “Uncle Rod's Used SCT Guide”, a comprehensive primer on all things SCT. (After reading this, if you think that Rod “wrote the book on SCT’s”, well, yes he did! Choosing and Using a Schmidt-Cassegrain Telescope : A Guide to Commercial SCTs and Maksutovs (Practical Astronomy.)  by Rod Mollise.  It’ will be out in May of this year.  Watch this space.

Hope to see everyone at the meeting,