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Wednesday, November 2, 2022
7:00 pm
Madelyn Helling Library

Making Large Minor Axis

Secondary Mirrors

by
Jeff Baldwin

 

With all the LAFFRTs (Large Aperture Fast Focal Ratio Telescopes) 30 inches and up that are now being made, the need for Large Minor Axis Secondary Mirrors (LMASMs) is growing.  Right now these mirrors are not only large in size, but very large in price.  So in addition to making LAFFRT mirrors, Jeff is converting his shop over to making precision LMASMs hopefully at a more moderate price.  Jeff will discuss the waterjet cutting, blocking, grinding stations, lapping machine, interferometer, figuring and testing and coating of these mirrors.  He will be broadcasting from his shop live on Zoom. 

Jeff Baldwin has been making telescope mirrors for about 40 years.  His shop is in Lathrop, CA.  He just retired as a math teacher and is now working full-time in his shop and is expanding from paraboloidal mirror making to include secondary mirror production. 

 

 

All are welcome! Bring a friend!

President’s Rant - November 2, 2022

Well, NASA has reported that its DART spacecraft's kinetic impact with the target asteroid, Dimorphos, successfully altered the asteroid's orbit, shortening its orbit around Didymos from 11hr55min to 11hr23min.  This was achieved by the head-on collision, which slowed Dimorphos down, resulting in a lower orbit and a decrease in its orbital period.  The ejecta debris - the tons of asteroidal rock displaced and launched into space from the impact, will be analyzed to determine how much blast recoil contributed to the orbital change.  Again, the hope is that diverting an incoming future asteroid might prevent us from going the way of the dinosaurs.  

A total lunar eclipse will occur during the morning of Tuesday, November 8.  In our neighborhood, the eclipse starts at midnight, with totality starting at 216am and lasts until 341am. Greatest eclipse occurs at 259am. Our last eclipse on May 15 was low on the eastern horizon at dusk where it was obscured by clouds, only to be seen 1-2 hours later by those who persevered.  This time it will be high in the western sky where the full moon usually is at that time of night.  After this viewing, the next total lunar eclipse will not occur until May 13, 2025.  So set your clocks to wake up around 2am or just stay up all night and forgo work the next day.  What is more important?  Well, as a backup, board member Paul Bacon, astrophotographer extraordinaire, will be setting up and taking photos of the eclipse for your later perusal.  Receiving astrophotos is another reason to sign up for our groups.io member email site.   

At our October meeting, we all enjoyed our reunion with Dave and Lorraine Buchla - they moved to Georgia some 20 months ago.  Dave was one of the founding members of our club, and played a huge role in both leadership and community outreach.  His recap of his first two lectures on Ancient Astronomy and his lively depiction of Renaissance astronomers did not disappoint. 

This month we are looking forward to hearing from Jeff Baldwin - see above - who will provide us with More Mirror Making Madness, adding to what we learned from Bill Thomas during the summer.  As before, the meeting will also be broadcast on Zoom.  If you cannot attend in person, please send us an email by clicking on the Contact tab at the top of the page, and we'll send you the Zoom instructions. 

We hope to see you soon,

Greg Ouligian


Outreach - Hilary Steinmetz

Nothing new to report.


 

NC Astronomer members continue to enjoy the beer and blather, which will now be held at the 1849 Brewing Company. The beer selection at the brewery is quite comprehensive and they also have an on-premises cafe for your culinary delight. The environment allows for in-depth conversations on deeply philosophical questions. 

Image result for astronomy on tap

Each month we discuss current topics in Astronomy and share our ignorance.

Note new meeting location

 Astronomy on Tap meets on

The third Wednesday of the month at 5pm

 

Come and join the conversation at

1849 Brewing Company - 468 Sutton Way in Grass Valley


Secretary/Treasurer - Paul Bacon

 

Our Mission is:

'Bringing' Astronomy to the Public'

a BIG Thank You

to all our members who join and make our programs possible!

Help keep our wonderful little club financially healthy!

I am still collecting membership contributions for calendar year 2022

(Please remember our fiscal year runs Jan. 1 through Dec. 31)

($20/year for member or family)

at our Monthly Meetings,

If you can't make the meeting, send your check to:

          NC Astronomers, %Paul Bacon,                    
10572 Oak St., Grass Valley, CA 95945


 


NASA Night Sky Notes for November 2022

 

Cepheus: A House Fit for a King

David Prosper

 

Sometimes constellations look like their namesake, and sometimes these starry patterns look like something else entirely. That’s the case for many stargazers upon identifying the constellation of Cepheus for the first time. These stars represent Cepheus, the King of Ethiopia, sitting on his throne. However, many present-day observers see the outline of a simple house, complete with peaked roof, instead – quite a difference! Astronomers have another association with this northern constellation; inside its borders lies the namesake of one of the most important types of stars in modern astronomy: Delta Cephei, the original Cepheid Variable.

 

Cepheus is a circumpolar constellation for most observers located in mid-northern latitudes and above, meaning it does not set, or dip below the horizon. This means Cepheus is visible all night long and can be observed to swing around the northern celestial pole, anchored by Polaris, the current North Star. Other circumpolar constellations include Cassiopeia, Ursa Major, Ursa Minor, Draco, and Camelopardalis. Its all-night position for many stargazers brings with it some interesting objects to observe. Among them: the “Garnet Star” Mu Cephei, a supergiant star with an especially deep red hue; several binary stars; several nebulae, including the notable reflection nebula NGC 7023; and the “Fireworks Galaxy” NGC 6946, known for a surprising amount of supernovae.

 

Perhaps the most famous, and certainly the most notable object in Cepheus, is the star Delta Cephei. Its variable nature was first discovered by John Goodricke, whose observations of the star began in October 1784. Slightly more than a century later, Henrietta Leavitt studied the variable stars found in the Magellanic Clouds in 1908 and discovered that the type of variable stars represented by Delta Cephei possessed very consistent relationships between their luminosity (total amount of light emitted), and their pulsation period (generally, the length of time in which the star goes through a cycle of where it dims and then brightens). Once the period for a Cepheid Variable (or Cepheid) is known, its luminosity can be calculated by using the scale originally developed by Henrietta Leavitt, now called “Leavitt’s Law”. So, if a star is found to be a Cepheid, its actual brightness can be calculated versus its observed brightness. From that difference, the Cepheid’s distance can then be estimated with a great deal of precision. This revolutionary discovery unlocked a key to measuring vast distances across the cosmos, and in 1924 observations of Cepheids by Edwin Hubble in what was then called the Andromeda Nebula proved that this “nebula” was actually another galaxy outside of our own Milky Way! You may now know this object as the “Andromeda Galaxy” or M31. Further observations of Cepheids in other galaxies gave rise to another astounding discovery: that our universe is not static, but expanding!

 

Because of their importance as a “standard candle” in measuring cosmic distances, astronomers continue to study the nature of Cepheids. Their studies revealed that there are two distinct types of Cepheids: Classical and Type II. Delta Cephei is the second closest Cepheid to Earth after Polaris, and was even studied in detail by Edwin Hubble’s namesake telescope, NASA’s Hubble Space Telescope, in 2008. These studies, along with others performed by the ESA’s Hipparcos mission and other observatories, help to further refine the accuracy of distance measurements derived from observations of Cepheids. What will further observations of Delta Cephei and other Cepheids reveal about our universe? Follow NASA’s latest observations of stars and galaxies across our universe at nasa.gov.

 

 


Officers
Click to Contact
President Greg Ouligian
Vice President John Griffin
Secretary/Treasurer Paul Bacon
Outreach Coordinator Hilary Steinmetz
At Large Greg Dolkas
   

NC Astronomers
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NC ASTRONOMERS
Meets
First Wednesday Of The Month
Madelyn Helling Library
Community Room
980 Helling Way
Nevada City 95959

NC ASTRONOMERS
10572 Oak St.
Grass Valley, CA 95945
http://ncastronomers.org


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