From: Al Kelly Sent: Monday, June 24, 2002 5:54 PM To: SBIG@yahoogroups.com Subject: [SBIG] Re: Solar Analog Stars Well, I guess we described the theory better than the detailed process. Here's what you do in AIP4WIN: 1. Find one of the Solar-analog stars (in the list at the end of the article) up high in the sky on a very clear, transparent night. Note the altitude of the star. 2. Image the star through each filter. a. Take 5 or more images through each filter so that you can obtain a good average star flux through each b. All exposures should be the same length, as exactly as possible, such as to the nearest one-hundredth or one-thousandth of a second. c. The exposure duration should be short enough to *assure* that no star pixel is saturated. For example, if your camera saturates at 30,000 ADU, make the exposures so short that no star pixel is higher than maybe 10,000 ADU. d. Take a dark frame of the same exposure duration to use to calibrate each star image (flats aren't necessary) e. Leave the focus very slightly "soft" and let the star drift across the field slightly between exposures, so that you aren't taking the star data with the exact same pixels of your camera in each image. 3. Dark-subtract, register, and stack (average) the images so that you end up with good average RGB stacks. 4. Bring the stacked images up in AIP4WIN and run the COLOR/COLOR CALCULATOR drop-down. Activate the G2V STAR PHOTOMETRY bar. Click on the star in the red image, centering it in the double radius photometry measurment circle, then click the RED bar in the G2V STAR PHOTOMETRY drop-down (notice that a photometric measurement of the star's flux is entered automatically in the RED field of the COLOR CALCULATOR). Do the same for the green and blue star images. 5. Enter the altitude where the star was imaged in the COLOR CALCULATOR and click on the CALCULATE WEIGHTS bar. Click on SAVE WEIGHTS if you want the program to remember your weights for use in color compositing. Find a Good Sky ! Al K.