This has been an exciting couple of weeks. As we have seen our first frost of the season (no snow just yet!), we have been putting up the frame and the structure of the building. Click on images for full size.
Yesterday the concrete for the telescope’s pier was poured. What an exciting moment in this telescope’s history. The contractors used a very large Sonotube held rigidly in place with a temporary framework of wood and cables. Internally there is quite the framework of rebar to help reinforce the pier’s strength. A few conduits were also placed inside for electrical and data lines which will drive the telescope. Images (click on them to enlarge):
A view of the building’s site with the framework around the Sonotube for the pier.
This will likely be a series of posts involving some very exciting news here at the observatory: We are adding a new observatory building complete with dome and telescope! Very much exciting times! The new structure will be 16’25’ in dimension with a 16′ diameter dome on the south side. The interior will be divided into two sections: the telescope/equipment room and the control room. A wall with large glass window will separate the two so that people can work with low-level red lighting while keeping the telescope and its sensitive instrumentation in the dark and away from the heat of humans which can cause disturbing air currents.
The telescope is a PlaneWave 0.70m diameter modified Dall-Kirkham optical system with two ports. One port will hold a CCD imager with filter wheel. The other will attach to a fiber-fed echelle spectrograph. It is difficult to imagine the scale of such an instrument. The telescope alone weighs over 1500 pounds! For a comparison here I am standing besides the same model of instrument at a recent American Astronomical Society meeting.
Ground breaking started a couple of weeks ago. Concrete pouring started today for the pier footing and the footing for the building’s foundation. This will help give a sense of scale the final structure.
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
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.
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 😉
Space weather has long been an interest of mine, and of many of the students passing through my astronomy courses. The interaction of the Sun, it solar wind and our Earth’s magnetic field are just fascinating. Living in high latitudes, we sometimes are given the pleasure of seeing some aurora. In collaboration with the University of New Hampshire, we have taken on the building of a 3 axis fluxgate magnetometer. The unit is from a kit which you can check out here at the SAM-III Magnetometer page. If you are not quite so keen on soldering small components (only a few are surface mount), then you can also order a pre-built one…. but it costs more.
Here is our progress to date in photos.
The observatory took delivery of a new 16″ f/8 ACF Schmidt-Cassegrain telescope this summer. It has been installed, collimated and tested out on a recent clear night. This telescope joins the list of instruments available for swap in the Kurtz Dome. With a 16″ aperture, it has the largest light gathering power of all the instruments at the observatory and also the highest resolving power. We cannot wait until Saturn and Jupiter are in our skies! Stay tuned for information about open houses and other observing opportunities. http://www.twitter.com/PEA_Obs