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 😉
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
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:
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 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
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.
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
The new 16″ telescope just after installation with Dr. Ward and Dr. Adams.
On the evening of the 16″ first light. We were able to enjoy nice views of M-16, M-13, M-57 and more.
It is that time again! I will be hosting another astronomy education conference starting this weekend! The weeklong meeting will allow astronomy educators from around the USA to discuss and try various methods of teaching modern astronomy and astrophysics. Topics that have been covered in detail in the past:
- CCD Imaging: photometry, color work, narrow band filters, astrometry, guiding, installation, design.
- Observatory design, construction and maintenance.
- Available software for astronomy, science, data reduction, learning and labs.
- Required topics in astronomy.
- Best practices in astronomy education, pretesting, post-testing, assessment.
- Teaching astronomy in difficult situations: limited budgets, light pollution, late nights out.
It is always a fun time, and generates a ton of communications following the event. This year, we are once again full. We even had a wait list! Stay tuned for more information as the week progresses.