The awesome Southern Gems team has published their first product: a version of the 10-Star Tutorial for the southern hemisphere. It's a great example of complementary team work.Read more
In just a few days I'll be departing for my last scheduled observing run for this season at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) observatory located on Mount Wilson, CA (just to the North of L.A). In a similar spirit to my series of blog posts on observing at NASA's IRTF (preparing and conducting observations, what the data looks like, and what we hope to observe) I thought I would do the same for CHARA. Planning for the observing run consists of three stages: proposing, preparatory work for planning, and finally preparing the plan.
Suddenly the leaves are off the trees and carved pumpkin symbols abound - we've reached another "quarter-cross" day, which means half way between seasons. Halloween (or more properly, All Saint's Day during late Oct and early Nov mark the time half-way between the autumn equinox and winter solstice. You know other quarter-cross days as Groundhog's Day (Feb.2), May Day (May 1) and more causally, the Dog Days of early August (connected with the heliacal rising of Sirius).Read more
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
It's a 3-day weekend for those in the USA. So here is a list of some eclipsing binary stars with expected eclipses this weekend. They are mostly bright so can be seen with the naked eye or binoculars. If you are out this weekend, look up, make a few obs and report them!
For you morning folk, our friend Algol (Beta Per - the Demon Star) will be in eclipse the evening of July 3-4. Mid eclipse is around 4:30am eastern, but it should start dimming around 12:30am or so. You don't have to stay up all night to get the whole eclipse. Just getting the start or end would be fun enough. Algol's chart is in our 10-Star Tutorial. It's brighter then epsilon Aurigae so can easily be seen from the city. Read more
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.
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:
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
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
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