This Tuesday night Dr. Stencel and I have four-hours of observing time on NASA's Infrared Telescope Facility (IRTF) during which we will be observing epsilon Aurigae in the infrared (0.8-5.0 micrometers). I thought this would be a perfect opportunity to offer you a glimpse of what a observing run is like at world-class research facility.
Over the next couple of days I'll be providing details about our observing session. I hope to cover these topics:
- Why we needed the observing time and what we hope to see.
- What goes into getting observing time at a research telescope.
- How we prepare for an observing session.
- How the observations are conducted.
- What the data actually looks like.
- How the data is reduced.
Stay tuned.Read more
During the 1983 eclipse something funny happened in the infrared spectrum. In addition to the continuum from the F-star, additional absorption lines started to appear. This doesn't seem that odd until one considers that some of the spectral lines, carbon monoxide (CO) in particular, did not appear until after mid-eclipse. The high resolution spectra obtained during the ecipse also provided some other interesting details, but I'll let you read the paper to find out those tidbits of information. (As an interesting sidenote, the integration times for these spectra were very long. One spectra i particular took 670 minutes! That's a little over 11 hours to get a single spectra!)Read more
Before I entered graduate school, I had no idea about the complexity of research proposals, especially those in astronomy/astrophysics.
All telescope time for which I have applied has been peer reviewed. This means that my proposal is read by fellow astronomers/astrophysicists and evaluated against some scoring method. It is my responsibility, as the proposer, to convince the committee that not only is my research interesting, but also doable from a technical perspective.
The basic outline of the proposal process is thus:Read more
Picking up where I left off, in this blog post I will cover two topics: how we prepare for an observing session and how we conduct the observations.
How we prepare for an observing session.
The answer is short: meetings. Lots and lots of meetings. As part of our proposal we already specified our primary target (eps Aur) and verified that the instrument is capable of observing the star. We also specified at least one A0V star to use as a calibration star for telluric (atmospheric) line removal. In our final meetings, we double-check exposure times, calibration stars, and coordinates. During this time we finalize our observing plan by deciding the order in which we will observe the stars on our list and insert flats, darks, and arcs (all required for calibration) so that we can maximize our observing time.Read more
As I have mentioned before, the instrument we used at IRTF is called SPEX. It is a medium resolution spectrograph. Specifically, it's a cross-dispersing spectrograph. What does this mean? Well, instead of dispersing light like a prism where the colors are all in one line, SPEX breaks the spectrally dispersed light into several orders that are displayed along side each other. I've included a copy of a figure I made for a previous presentation that includes SPEX data in LXD1.9 mode to give you an idea about the dispersion:
How the data is reduced.
In short, we use a program developed specifically for reducing spectra from SPEX called SPEXTOOL. It is written in a commonly used programming language for Astronomers called IDL. I'm going to skip over a lot of the details, but in SPEXTOOL there are basically two steps:
- Construct Calibration Frames (for wavelength calibration, flat-field subtraction).
- Extract the spectral orders.
I've been largely missing from the CS website for the last several weeks and thought it was worth providing an update of my activities, both related to CS and towards my dissertation.
On the CS front, the DSLR team has finished an air-mass corrected reduction spreadsheet that is mathematically sound. We think it's ready to go main-stream and hope to have it online soon. We'll have a new tutorial for using this sheet. A while back Tom Pearson and I wrote an article on DSLR photometry and submitted it to a popular astronomy magazine. It was accepted for publication, but after six months of waiting for it to progress to publication we decided to pull the article and publish in a different venue. We are in the process of adapting the content for the new target.Read more