The main page for Ay 20 is maintained by the professor - see Sterl's page at: http://www.its.caltech.edu/~esp/ay20/. The links on the top lead directly to various sections on his page.

On this page you might find random links and snippets relevant to the course. They will be announced by email / in class whenever they are put up here.

Problem Set 2:

• Perl code for calculating photons in a certain passband: Download | View online
• Perl code for calculating flux in a certain passband: Download | View online

Coordinate systems: Here is a old talk about coordinate systems I had presented... might be useful if you are confused about RA-Dec and stuff.

Problem Set 4:

• Perl code for calculating intensity in a certain passband: Download | View online [Similar to code in Problem Set 2, but easier to use]

Observing Proposals:
Here are the actual files submitted to the P60 observing queue.

• Comet 191P/McNaught: Submitted file | Complete Ephemeris from Minor Planet & Comet Ephemeris Service
• NGC 6819: test images (180 sec, 30 sec) for feasibility: Submitted file

Images:
The images procured by the P60 are automatically processed (flat feilding, bias subtraction etc) by the P60 pipeline, and we are obtaining these processed files. Links to those files are provided in the table below. Note: each of the fits files linked here is typically 16 MB in size.The GIF images are all <100 KB in size. Right click on the filenames and click "save as", its not fun to see 16 MB of stuff rendered into your browser. Use the gif files for previewing, they were generated using the command-line "convert" utility. GIF is a lossy image compression format, so those images are almost useless for scientific analysis.

Analysis:
For analyzing the images, a combination of ds9 and aladin is the easiest method I found. ds9 is a standard FITS viewer used by astronomers - you can download the version for your favourite operating system here. Aladin is an online application in java.

ds9 lets you view fits headers, play with image display, contrast and rendering options, zoom, read off intensity values, etc. It also lets you do more advanced things like see the coordinate system in your fits files, download catalog information from various servers (try GSC 2.2) to identify all stars in your field, etc.

On aladin, go and upload one of the fits files, and then use the "source extractor" utility to find all star-like sources in the fits file. You can save the resultant table as a tab-separated text file. This returns relative magnitudes of the stars, and with the help of a few TYCHO reference stars (from ds9), you can calibrate the fits file. These two utilities should enable you to do everything in the proposals: plot HR diagrams, plot lightcurves, extract comet positions, and look at eclipsing binaries (with their known positions).

For detailed analysis, you can use IRAF. The images here are pre-processed (hence the suffix "p" in all filenames), meaning that the P60 auto pipeline has done a lot of work for you. For those wanting to try more, contact me to get access to the raw files - you can then do bias subtraction, flat-feilding, flagging and masking known bad pixels, etc to get the processed images. You will notice that all images are taken twice. The reason for this is that in detailed analysis you can use them to flag false events, cosmic rays etc, and get better photometry.

UPDATE: 25 November
So, the sextractor in Aladin is buggy: it works only when it wants to. At other times, it will reject the same images with an error message. For example, i have run it successfully on 20071107022558p.fits to get this. But today it refuses to analyze that file.

It turns out it is based on a stand-alone program called sextractor, which can be downloaded from the sextractor homepage. Its a linux-only system, you might be able to run it on windows through cygwin or xming etc (if you dont know what that means, then you should just find a linux machine).

How to use it:
Download and extract the tar.gz file. (Red hat/fedora users can use the RPMs linked from the same site).
Install (normal steps: ./configure, make, make install) - the info is given in the file called "INSTALL"
Now, it will probably give errors when you run it. The reason is that the rather poorly documented default.conv and default.param files are missing. Download these files into your working directory.

Then just give the command:
sex filename.fits
The output will be a file called "test.cat" - where the columns are clear enough. You might want to go through the documentation on the sextractor website to learn what other parameters you can set, etc. One useful link is http://star-www.dur.ac.uk/~pdraper/extractor/Guide2source_extractor.pdf.

I just tested the software, and the entire procedure was under an hour (including finding undocumented files) - the bottomline is that it works. Happy extraction !

UPDATE: 17 December
Aha ! more disc space - so all the data is back :)