SDSS BOSS Plate 6192

Thanks to the fine carpenters at the Academy, we now have our Sloan Digital Sky Survey (SDSS) plate mounted and hanging on my classroom wall. It has been encased in a wooden box filled with ornamental lights, giving it that astronomical view.

SDSS BOSS Plate 6192

The SDSS Plate in its display case. Note the markings which help astronomers identify the various targets.

Information on the plate itself is rather interesting. This is a plate for the Baryon Oscillation Spectroscopic Survey (BOSS) which has the goal of mapping baryon acoustic oscillations signatures by looking at the spectra of some 1.5 million luminous red galaxies. The survey will help astronomers to place limits on the universe’s expansion rate, and more! The plate here was used to hold optical fibers on the SDSS telescope’s focal plane so that each fiber, attached to a hole on the plate, captures light from just one galaxy. That light is then funneled down the fiber optic path to a spectrograph.




The plate has a bunch of markings on it to help astronomers with the data collection process. Fiber optic bundles are grouped together such than each bundle gets a section of the plate bounded by a black border. Blue circles around the openings correspond to the galaxies locations for which spectra are being collected. The black circles around the holes correspond to guide star locations in the field.

The SDSS plate illuminated.

The SDSS plate illuminated.


This is the SDSS field of view for this specific plate. Click on this image to go to the SDSS Navigate tool and have a look around!

SDSS BOSS Plate 6192/56269
Observed on MJD 56269 (8-December-2012)
Plate center: RA = 7.98654794692993, dec = 16.3795967102051
SDSS BOSS Plate 6192
SDSS BOSS Plate 6192’s field of view as seen by the SDSS
The SDSS then converts all the spectra to plots and measures their z (redshift) values, among other things. One spectra from the many on this plate is below



10 February 2017 Penumbral Lunar Eclipse

Students and community members joined the crowd at the observatory on Friday night (10 February) to enjoy the penumbral lunar eclipse that was gracing our skies that evening. The moon made its way above the trees in the east by 6:15pm, a lovely full moon, so bright that it looked like floodlights had illuminated the soccer fields by the observatory. It was cold!  The thermometer hovered at 11°F and the wind was calm. As people gathered, there was a pulsing of people headed into the Chart House to stay warm, along with those coming back out to view the eclipse’s progress.

This was our first almost-clear evening in quite a while. The day before was the first “snow day” that the Academy had enjoyed in a long time! The new snowfall, well over 10″ deep, had ben plowed from the paths (THANK YOU to our facilities department!), allowing access to the Chart House and Kurtz Dome housing our 16″ SCT telescope. We also had a camera with zoom lens attached, and a pair of tripod-mounted binoculars for people to enjoy.

As predicted, clouds did start rolling in by 7:30pm. With the eclipse hitting maximum at 7:44pm, we had a good view of it before all was obscured. Two good photos below: One of the moon at maximum eclipse, and one of the moonlight causing a 22° ice halo and moondog. Both taken with a D810a and 300mm lens.


Magnetometer Testing: Installation and Software Operational

The magnetometer is now installed and running in a test location at the observatory. Both raw data and a continuous plot of data are available online at:   This URL is likely to change as things become more permanent. At this time, the data correlate well with other magnetometers. We are waiting for a couple of other installations in southern NH to complete before we are able to test thoroughly and make this available for scientific use. Stand by for that!  A typical data plot is below for a quiet day. The green stripe along the bottom indicates quiet conditions. As geomagnetic activity increases, the stripe will turn yellow then red when the K index hits 6 or more.


Geomagnetic activity from our magnetometer for 2016-December-15, a rather quiet day.

Magnetometer Testing: Geomagnetic Storm Detected

The magnetometer is on a lab bench at this time and running continuously. Typical plots look like the one below from 10-October-2016. Deviations from the 00hour UT moment at the start of the plot are in nT. Time is in UT. Short vertical changes are typically automobiles moving in the area. 10-October was a geomagnetically calm day.


A small CME struck the Earth on 13 October resulting in a G1 level storm and some fabulous aurora for northern latitudes. The Kp index hit 6. The magnetometer detected this storm as can be seen by the plot below.


Getting the plots into Excel: Import the files using space and comma as the delimiters. Create three columns for delta x, y and z. Input an equation that calculates the difference between the current cell and the initial entry (format: =c1-$c$1 which creates an Excel absolute cell reference to c1). Check the data all the way down!  There are corruptions in the readout that might be from the serial to USB converter. Graphs will not plot properly unless those errors are removed. Below is what the sheet will look like when you’re ready to plot. Columns D, F, and H are the calculations of “=c2-$c$2”, “=e2-$e$2”, and “=g2-$g$2” respectively.


Focuser Assembly

Summertime: Time for Repairs and Maintenance

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

Focuser Assembly

Focuser Assembly: The secondary mirror is in the black housing inside the telescopes truss tubing.

Focuser Assembly

Focuser Assembly

Focuser Assembly

Focuser Assembly

Electronic Controller for Focuser Assembly

Electronic Controller for Focuser Assembly. This unit controls heaters, fans, focus position and more.

Altair being imaged at perfect focus

Altair being imaged at perfect focus. Success!

Milky Way seen from Cerro Tololo.

Summer Activity

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

Arrival in Santiago

Visit to AURA

Under the Stars of Cerro Tololo: Night 1

Under the Stars of Cerro Tololo: Night 2

Panoramic Chile

Cerro Pachón & Gemini South Telescope

Cerro Tololo: A Summit of Telescopes

San Pedro de Atacama and ALMA


Final Tests then a New Case

Magnetometer Build Status

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 completed main board

The completed main board

The display board

The display board

The boards and keyboard attached for testing

The boards and keyboard attached for testing

This is the first boot of the system! Success!

This is the first boot of the system! Success!

Final Tests then a New Case

Final Tests then a New Case

First time operations with all three sensors

First time operations with all three sensors

Initial testing of the logging software

Initial testing of the logging software. A lot has to be done to configure this a little better, but it is good to see it in operation.

The working end of the 16" SCT with the D7000 attached for prime focus work.

9 May 2016 Mercury Transit

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.

Mercury Transiting the Sun 9 May 2016

9 May Transit of Mercury seen through the 16″ SCT. A Nikon D7000 was used to snap this image which shows the small round dot of Mercury along with two sunspot groups.


The working end of the 16″ SCT with the D7000 attached for prime focus work.


The heliostat in use. This is also a unique selfie opportunity.

Mercury Transit 9 May 2016

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
External Ingress 11:13 07:13
Internal Ingress 11:16 07:16
Greatest Transit 14:57 10:57
Internal Egress 18:38 14:38
External Egress 18:41 14:41


Gravitational Waves!

Observatory Director, John Blackwell, explains the recent discovery of Gravitational Waves

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.