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.


Echelle Spectrograph Up and Running

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:

H Aplha

H Aplha

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 😉




Magnetometer in the Making

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.

Parts and pieces

Parts and pieces! This will be the magnetometer when it is all put together!

The keyboard

This is the primary user interface: a keyboard of 4 buttons. These are the only surface mount items to worry about.

The keyboard

This is the primary user interface: a keyboard of 4 buttons. These are the only surface mount items to worry about.


Soldering the resistors onto the board. Next will come the capacitors and other parts.


Resistors and capacitors in place.

Voltage tolerance test

Resistors and capacitors in place along with voltage regulators. Here we are ready to apply power for the first time to see if the boards voltages are within tolerances.

Lunar Eclipse Wows All!

September 27th lunar eclipse was an awesome experience from Exeter, NH. Well over 100 people came to the observatory for a visit and a look through the telescopes while the eclipse was under way.  At moonrise, I thought there was actually someone with a spotlight in the adjoining fields…. nope! That was the moon!  It was BRIGHT!  Bright enough to take this 5 second exposure of the fields and fog:

Fields and Fog with Full Moon

Fields and Fog with Full Moon

As the event ensued, we had a few cameras out there: one taking wide field shots of the event every 10 minutes or so, one taking closeup images with a 200mm telephoto, and some others roaming around. The following two images are of the event with the images stacked in PhotoShop. The moon’s dimming is very much evident here:

Eclipse series 1

Wide field series of images of the eclipse.

This image shows the eclipse with deeper exposures. The stars become evident as the moon dims. Note to the lower right the light pollution from Boston, to our south. As with all photos in this blog, click on the images for higher resolution!

Wide Field Series 2

Wide field series with deeper exposures.

This series below is from the 200mm lens and follows the eclipse from full moon (no eclipse) to totality.  Photoshop wass used to stack the images. Click for higher resolution.

Sept 27 2015 Lunar Eclipse Series

Sept 27 2015 Lunar Eclipse Series


We have been working on improving long observing runs with the robotic telescope this past month. Asteroids are an excellent target: they move constantly relative to the background stars; Their orbital parameters change often enough to warrant close scrutiny; There are hundreds of thousands of them to study; Photometric studies are as important as astrometric studies; All of this is well within the reach of Exeter students!

While we perfect our methods, the following is a two day series of asteroid #783 Nora.  Nora has a strongly elliptical orbit around the Sun with its closest approach being 1.8 AU and its most distant 2.8 AU. In this two-night series, Nora had two images taken one hour apart each night for two nights. Enjoy!

Minor Planet 783 Nora

Minor Planet 783 Nora

Planning Ahead: The September 27/28 Lunar Eclipse

There is an excellent opportunity coming up to see a total lunar eclipse this September… in just a few weeks! Plan now! This one is visible from western Europe, Africa and the Americas.  Eclipse timings here:

Lunar Eclipse Timing (all times UT) September 27-28, 2015

  • 00:10 Moon enters penumbra (not visible)
  • 01:07 Partial Eclipse Begins
  • 02:11 Totality begins
  • 02:47 Mid Eclipse
  • 03:24 Totality ends
  • 04:27 Partial eclipse ends
  • 05:24 Moon leaves penumbra

So for those in the Eastern time zone which is still in EDT (daylight savings mode), the times are here below….

Lunar Eclipse Timing (all times EDT) September 27-28, 2015 below:

  • 08:10pm Moon enters penumbra (not visible)
  • 09:07pm Partial Eclipse Begins
  • 10:11pm Totality begins
  • 10:47pm Mid Eclipse
  • 11:24pm Totality ends
  • 12:27am Partial eclipse ends
  • 01:24am Moon leaves penumbra
September 2015 Lunar Eclipse (courtesy NASA)

September 2015 Lunar Eclipse (courtesy NASA)

The Observatory’s Summer Activities

School might get out in June, but the Observatory is a buzzing place with all sorts of activities while the students are away. The primary charge for us is completing the cleaning and maintenance work that needs to be done to keep all the equipment in top working order. This year, we also received a new optical tube assembly for the Kurtz Dome, necessitating some serious lifting and alignment procedures. Here is the list of activities done this summer to date (summer is not over just yet!):

  • Dome cleanings: Just after students graduate, the first order of business is to give each dome a thorough cleaning. Observatories maintain a low level of sweeping, as this kicks up a lot of dust and makes the optics a real mess. In spring, the optics are thoroughly sealed in plastic bags, the cobwebs and pollen and dusted down from top to bottom, then the whole dome is vacuumed and wet-wiped.
  • Batteries in the various components are replaced: there are little button batteries here and there for little things like ROM backups, and bigger things like illuminated reticles for the finder scopes.
  • We installed the new 16″ ACF SCT telescope in the Kurtz Dome. The Takahashi refractor and the Celestron SCT were removed first. The mount saddle was configured for two optical tubes and was turned 90 degrees, so that required realignment. That done, the new 16″ OTA was put into place and counterbalanced. It is one heavy OTA at 75 pounds. The weights need to be in proper position to prevent too much stress on the mount’s drive systems. Once balanced, the whole system needed to be reconfigured for the larger tube using software that knows the extent to which the tube can travel without smacking into the pier. That would not be good!
  • The Robotic Observatory had a complete software upgrade. Those who know me, know one of my mottos: if it is working, DO NOT upgrade anything. I hold to this as much as possible, but there are times when things are working, but the software manufacturers have control over us. In this case, the license for our internet-accessible server/control system was expiring, and they would not allow a simple renewal without software upgrade. Alas!  Upgrading that required upgrading everything. The status now with the software is that the automated focusing software is not compatible with the other pieces. We focus by hand for now. That said, there are other gremlins in the system:
    • The electronic focuser was getting stuck. A little dismantling and some lubrication fixed that. We had a solid run last night without any focuser issues.
    • No focuser issues means that we must have had something else going on… nothing is perfect. Yes, the shutter on the CCD imager was getting stuck! After 40 flawless images, the images started to show the bright stars with vertical blooming down each column. This means that the shutter was remaining open as the CCD downloaded the images by pushing the pixel charges down to the readout registers. Sigh. The camera needs to be dismantled and diagnosed now. That is on the to-do list.
  • New tripods were ordered for the portable telescopes which have a few benefits: They allow easy polar alignment; They can be adjusted for height (not all students are very tall); They are lighter, easier to carry around; They are much more stable than the piers we used to use.
  • The spectrographic system in the Alden Dome has checked out perfectly.
  • The Heliostat has checked out perfectly, though I am beginning to think about getting the mirrors a new aluminum coating.
  • Tested a home-made grism (a diffraction grating system: grating + prism = grism) with a DSLR camera on the 16″ telescope. Results are encouraging and might be awesome to use with winter Astronomy 392 classes.