131008 SBAU Telescope Workshop, October 8, 2013
DmitriiZ, TomW, JerryW, ChrisU, TomT
No grinding or polishing this evening, but lots of show & tell and questions answered.
-TomT asked JerryW about his 2”
Q70 Orion eyepiece that focuses a star in the center, but outer area stars are out of focus. Jerry says this may be expected of a (cheap) wider area eyepiece in that you can focus in the center, with the wider outer areas just used for recognition of other objects nearby.
http://www.amazon.com/Orion-8828-Wide-Field-Telescope-Eyepiece/dp/B000M89H72 has positive reviews but one talks about coma at outer edge.
-TomW brought in a
Marlin Jones http://www.mpja.com/ electronic equipment catalog that he uses to get supplies for his Westmont class he is teaching. He tested us on recognizing the NOT symbol, and on determining the result for a
logic table, based on a transistor photodiode resistor sketch he made. Transistor construction was discussed by JerryW. Doping of silicon layers with other elements create holes and extra electrons
http://inventors.about.com/library/inventors/blsolar5.htm . A ruby is Al2o3 with a doping of Cr to replace the Al
http://en.wikipedia.org/wiki/Ruby .
-ChrisU showed us his progress with his
Dobsonian mount, adding a wider bearing circle and receiving circle, plus he painted the plywood with white primer. A small part of the plywood bubbled up after the paint was applied. Chris also showed the Celestron
Plossel 9mm and 15mm eyepieces that Dr. Bob Richards gave to him at the last SBAU meeting. The Explore Scientific box was a fine piece of work also.
-ChrisU talked about going to the Avocado Festival SBAU outreach and seeing a few
solar telescopes. JerryW explained the use of an Etalon along with the other optics for narrowing the light down to the Hydrogen Alpha frequency, photons caused when an electron falls from the 3rd to the 2nd energy level. Other solar views were mentioned such as using a neutral filter or looking at the Calcium (Ca II, element 20) H & K energy lines (hard to see due to dark blue lines?) see:
http://daystarfilters.com/calcium.shtml .
-ChrisU brought in the
“Turn Left at Orion” book with beginners information about telescopes to good astronomical information on which objects to view and look for at various times of the year.
-TomW and ChrisU really liked the last SBAU meeting with Dr. Doyle talking about detecting Circumbinary planets and
SETI thinking about how aliens might communicate.
http://www.flickr.com/photos/27241501@N03/sets/72157636345264736/ [TomT has a video of this presentation that could be put onto a DVD if someone is interested in hearing it again.] See a previous presentation at SETI by Dr. Doyle
http://www.seti.org/weeky-lecture/detecting-circumbinary-planets
-TomT brought information on the
EasyTester, an eyepiece that incorporates Ronchi lines for testing the quality of telescope optics.
http://schmidling.com/ez-testr.htm
-TomT brought up that Jupiter was going to show three moon transit shadows at the same time, and wondered how to predict this
http://www.universetoday.com/105293/observing-alert-rare-triple-transit-of-jupiters-moons-happens-friday-night-oct-11-12/. TomW talked about using the sun-synodic and sidereal periods to do this.
http://www.skyandtelescope.com/observing/objects/javascript/jupiter
-JerryW will be going to a Santa Clara area astroimaging conference this weekend, Oct 11-13, the
Advanced Imaging Conference “The greatest gathering of astrophotographers under one roof”:
http://www.aicccd.com/ , only $399 (+$25 Lick Obs tour Thurs.+$85 for a Stanford tour Sat. (but incl all AIC conf meals, a $275 value), vs. +$100 for Fri/Sat dinner&banquet, +$105/night Hyatt).
-JerryW volunteered to do a Member’s night
presentation, Dec. 6, 15min. topic to be determined.
-Jerry also will work on an Invitation and explanation page, to be included in the
www.sbau.org webpages, for the Telescope Workshop. He will intrigue new and old members to participate making mirrors, building telescopes, and
discussing optics with us most Tuesday evenings.
-See a few more uploaded
Flickr photos from the discussions here:
http://www.flickr.com/photos/27241501@N03/sets/72157636345341036/
EdK- Stuff happens. Was polishing his 12.5” mirror for three more hours at home with the 9” pitched tool made by TomW. However, short scratches in surface were detected and EdK’s Foucault test at home was fuzzier. TomW thinks polishing compound was either contaminated or somehow Al2O3 compound was used instead of the CeO2. TomW says to dump the contaminated pitch lap tools, because DmitriiZ is having surface problems with his mirror polishing also. Laser check of mirror surface by TomW shows most areas even less specular; the light at the outer area is very wide compared to the inner area of the mirror. TomW set up Ronchi tester for EdK to check the mirror as well. At inside R, it showed very different pattern than before. 
