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bkloppenborg's blog posts
Mark your calendars: members from the DSLR Documentation and Reduction team will be hosting a second chat on Saturday, March 19 at 11:00 AM Eastern. If you have questions about using your DSLR camera for photometry, or any portion of our tutorials please plan to attend.
Although the chat has since ended, you can read the PDF transcript here. We look forward to seeing you at our next chat!
The April Issue of Sky & Telescope prominently features the work of Citizen Sky and the DSLR Documentation and Reduction Team. Two of the members, Brian Kloppenborg and Tom Pearson authored the article entitled "Photometry for All in the Digial Age," which promotes the work of the DSLR team and shows that when used properly DSLR cameras can compete with traditional methods for bright star photometry.
My first two posts about the Seattle AAS meeting focused on the two Citizen Sky posters and a slew of posters and the special session dedicated to epsilon Aurigae. This post is fulfillment of a promise: a discussion of the interferometry poster, along with one extra bonus: a "wow" image.
About two months ago I contacted Eric Jensen at Swarthmore College, the home of the Sproul Observatory with a simple question and shortly thereafter I ended up with three folders containing a slice of astronomical history.
Before we get to the good parts, I should give a little background. Back in November 2010 I wrote a blog post that discussed one of the fundamental problems with studying epsilon Auriage, the distance estimates are all over the map. The most modern distance estimate is from Hipparcos. It puts the F-star at 625 +/- 581 pc. With such a large uncertainty, coming up with any absolute scale for the system is a futile act. There are, however, other distance estimates that have much lower uncertainties.
The late Dr. Van de Kamp provides one of these estimates from a series of astrometric observations of eps Aur using the Sproul Observatory's 24” (61cm) refractor. The data were taken on photographic plates starting in 1938 and ending in the mid 1970's and cover about 1.3 orbits of the system. Among the astrometric solution, Van de Kamp's paper also featured an apparent orbit for eps Aur on the sky (see the small inset in the center of the image below)
After working out a preliminary orbital solution for the system from interferometric observations, one thing became clear, the inclinations didn't agree:
About two months ago I set out to figure out why the two sets of observations were so dissimilar. I contacted Eric Jensen at Swarthmore College (the home of Sproul) to ask if he had any information that might help me in my quest. He dug around in the basement of Sproul in which there is a whole drawer of plates labeled “eps Aur”
along with stacks of printouts. I met up with him at the Seattle AAS meeting and he provided me with three folders that amount to a historical goldmine: three folders of notes, printouts, and charts used in the publication of Van de Kamp's paper.
Aside from raw values from the plate measuring machine, there are two items that top the cake:
A Print from a photographic plate taken in 1938 showing eps Aur (marked with the greek symbol pi) (click to enlarge).
Van de Kamp's hand-drawn orbital solution (click to enlarge). Note, North is Down, East is to the Right
So, what do I hope to gleen from this information? I noticed some of his reference stars were moving in different directions than were assumed when the orbital solution was calculated (interestingly enough the erroneous motion is mostly in declination which could explain why the inclination was so low). Furthermore Van de Kamp used a method of dependencies to solve for the position of stars on the plates. With the help of local astrometrist, Paul Hemenway, I hope to digitize all of the raw data and compute a new orbital solution. With any luck, this will be congruent with the interferometric observations, but there is still a chance that the resulting solution may not. Only by doing the experiment can we find out. Read more
Greetings from day 2 of the AAS meeting in Seattle, WA.
Today was the big day in terms of eps Aur activity. There was a dedicated poster session as well as a special session with talks dedicated to the system.
You can view information about the talks here on the AAS website and the poster abstracts here. We also recorded the talks and will post them to CSky once we increase the audio and get a copy of the presentations so you can follow along.
A few highlights from the talks / posters:Read more
Greetings from the 2011 AAS Meeting being held in Seattle, WA.
Today Rebecca and I presented two posters on behalf of the Citizen Sky project. Rebecca's poster was focused on the project as a whole, whereas my poster discussed the work the DSLR Documentation and Reduction Team has created for the CS website.
I have posted a copy of the DSLR poster to my portfolio page:
https://portfolio.du.edu/pc/port.detail?id=176986 There were several people who were interested in using DSLR as photometers and thanks to conversation I think the team has some more work to do which will make a very cool, publishable paper.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.
I would like to announce that the DSLR Documentation and Reduction Team has released the long-awaited Air Mass correcting spreadsheet in the Intermediate-level Final Reduction tutorial. If you have been doing DSLR work in the last few months and your target star has been more than 30 degrees from the zenith, we highly suggest you re-reduce your data with this spreadsheet.
There are sure to be a few bugs we didn't get worked out in the tutorial and/or spreadsheet so if you find something please let us know. If you have any questions/comments, please post them in the photometry forums.
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