Eclipses are exciting whether they be partial, total or annular. On August 21st of this year, the USA will have an awesome opportunity to see a total solar eclipse pass right across the entire country from Oregon to South Carolina. People have already got their hotel rooms reserved, rental cars spoken for, and plane tickets purchased. Wherever you choose to go, you are likely to wonder about capturing this event by camera. Here are some thoughts, in no particular order (but I will try to keep it logical).
What goes into the repair of a telescope? A lot of time and technical operations.
Our robotic observatory has a 10″ Ritchey–Chrétien optical system. The system focuses by moving the secondary mirror in and out using a very finely controlled motor assembly. After years of hard work, this little assembly got jammed up solidly. The company that made the telescope has moved onto bigger and better things, namely producing to-order optics. Contacting them resulted in contacting an original engineer (James Olson… yes…) who was willing and able to do repairs on the focuser.
The focuser was removed: an intricate couple of hours removing the secondary mirror, detaching all the electronics for the dew heater and focus motor, and then balancing the telescope, since it had lost a lot of mass from its front end. The focuser assembly was then shipped to James in Arizona.
The focuser was taken apart by James, polished, lubricated, re-assembled, and tested for days before he shipped it back to PEA. Once back at its home, the focuser had to be installed back into the spider (24 bolts), the secondary mirror installed onto the end of the focus assembly (three push bolts and three pull bolts), then the whole thing tested for proper movement. A dozen runs of the focuser later, the electronics and mechanics of the system were AOK and ready for the next phase. The next phase?
Collimation! Having removed everything out on the secondary mirror region, everything was out of alignment. All the optics have to be centered on the optical axis, and aligned perfectly both perpendicularly to the optical axis, and rotationally, as these are a matched pair of mirrors… Sigh. That was a time consuming but worthwhile task. Last night the system was star tested. Success! An image of Altair was used for final touches on collimation, and an image of SS Cygni was used to test scientific data usefulness. SS CYG is now in outburst (huzzah!) and the data are perfect! We have V magnitudes to +/- 0.004. We are back in action!#astronomy #photometry #repairs #observatory #robots#PhillipsExeterAcademy
This has been a very busy summer! Much of my time was spent traveling, so here are some blog posts of those travels for you to enjoy. The trip to Chile was possible with the kind and generous support of the National Science Foundation (NSF), the Astronomy in Chile Educator Ambassador Program (ACEAP), and Phillips Exeter Academy. If you are interested in learning more about the trip or astronomy in Chile, feel free to contact me: jblackwell AT exeter.edu
An update on the build status of the magnetometer. The board has been tested for correct voltages and other parameters. The three sensors have been wired with filter capacitors and connected for some software testing as well. They have not been placed in any permanent housing, and we are investigating best practices for that. We anticipate installation in the fall term once students are back on campus and we regroup. Some images:
The day started out as partly cloudy with a blustery wind up to about 15mph. At 6:30am, the sun was well up, and 45 minutes it both cleared the trees and was to start a morning-long experience with the little planet Mercury crossing its face. Those 45 minutes came and went, and the clouds stayed until about 10am, when things started to clear out. We even had a few strong rain showers, associated with the looming cumulonimbus clouds that were rolling by. The wind picked up, the skies cleared, and the sun came out to play!
We had two telescopes in operation. The newest, the 16″ SCT in the Kurtz Dome was operating with a newly constructed solar filter: Baader solar film and cereal boxes combined with hot melt glue and duct tape. This makes for an excellent off-aperture 6″ screen for the monster scope. The other was our Heliostat which has an inverted Byers fork mount that moves a primary flat mirror to reflect sunlight onto the secondary and then into a 6″ refractor waiting through a hole in the Chart House wall in the library. We had some excellent views and enjoyed visitors from NH and MA as well as several astronomy classes and some members of the astronomy club.
This May we have the opportunity to see the planet Mercury transit across the face of the Sun. The next time to see this event will be in 2019, so don’t miss this! As with all astronomical studies involving the Sun: DO NOT OBSERVE THE SUN WITHOUT PROPER SAFETY: you only have one pair of eyes, so take care of them. Only use approved filters for astronomical observation of the Sun and use them properly! If you are unsure, contact your local astronomy club and ask.
This transit is visible in its entirety from Exeter. Timings are approximately as follows:
|Event||Time UT||Time EDT|
Gravitational Waves Explained: What The Discovery Means for Science
Last week, scientists made headlines with the announcement that they’d detected and recorded the first gravitational wave in human history. John Blackwell, Phillips Exeter science instructor and Director of the Grainger Observatory, explains how the discovery proves the last predicted outcome of Einstein’s theory of general relativity and gives astronomers the first new way of looking at the universe since Galileo pointed his telescope at the night sky.
Over the past few weeks, the high resolution spectrograph was down due to our working on installation of a new control PC and the replacement of the imaging fiber. The spectrograph is an Echelle design, utilizing a grating design that overlaps 50+ orders of spectra before then being split out into separate rows on an CCD image. The raw spectra image looks like a series of curved lines, but the software does its magic, sorts out which row is which and then reconnects them all into one long, high resolution spectra.
The wavelength calibration is done using a Thorium Argon lamp at the observatory. This lamp generates many well-known emission lines that the spectrograph software then uses to set wavelength values to the spectra of objects being studied. The ThAr spectrum is below with the spectral orders labeled and the identified emission lines wrapped in green boxes.
Once the software has all this figured out, each row is calibrated for wavelength and intensity and is saved in a tremendous FITS file. Below is one small piece of that FITS file for our Sun, the region around 656.3nm, the Hydrogen-alpha line:
Compressed to fit the screen here is a spectrum of our sun (actually clouds above our observatory, because imaging the sun directly would be the last thing we’d want to do with this device!). The image has been saved from Shelyak Instruments EShel software and calibrated within VSpec software. Wavelengths are in ångströms. The violet side shows that we have to work on radiometric correction for the instrument…. in progress 😉