Transitsearch.org is now operating in a trial phase with a limited number of candidate stars. We are still very much in the process of refining the observing procedures. Check back frequently for updates and more detailed information!
Here's how to capture your own transit, from start to finish.
1.1 Setup the telescope and the CCD, then connect the various signal cables. (wait until step 1.9 to attach the CCD to the telescope)
1.2 Align the telescope's finder very carefully.
1.3 Connect t
1.4 Turn on the telescope and computer, then plug in the CCD's power cord.
1.5 Start theSky software on the computer and establish the connection with the telescope.
1.6 Level the telescope, roughly align it's polar axis towards the north celestial pole.
1.7 Start the camera's control software, and set the camera temperature.
1.8 Attach the focal reducer to the telescope.
1.9 Attach the CCD to the telescope with the cables pointed up (finder side). (picture)
1.10 Focus the CCD, (you'll need a star and dark conditions), use the focus tools that come with your CCD's control software.
2.1 Take calibration frames; darks, bias and flat fields. (These will be used to reduce your data when you're done.)
Darks:
Biases:
Flat Fields:
2.2 Flat fields should have a total of 100,000 counts in each pixel or more to prevent introduction of random noise, this might require a light and screen rather than the use of twilight flats.
3.1 Align the telescope using the Polar option of the LX-200; several iterations are useful (this may require removing the CCD each time because of the interference with the mount near the tripod pole). An eyepiece with a reticle is helpful here. Try not to refocus each time you remove the CCD if possible.
3.2 Use Enif (Epsilon Pegasi) as a local reference star (star 238 in Meade list), use theSky to find Enif and slew to the calculated position of Enif. Then center it on the CCD using the telescope control paddle and use a star catalog to set the coordinates, by entering Star 238. The paddle display should say "coordinates matched" and theSky display on the computer should be centered on Enif.
4.1 Configure theSky Software
4.1.A Set the location and time
4.1.B Set FOV for CCD you have
4.1.C Set orientation to match CCD view ( here it helps to label the directions on your computer screen with arrows)
(sample screen dump)
4.1.D Now use theSky to find HD 209458 , slew to it.
4.1.E Verify finder view and in focus mode take some 2 second images, verify that screen dump below is what you see.
(picture)
4.2 Autoguider setup ( For our camera- finder telescope combination )
4.2.A To put a star onto Autoguider CCD put it above and to the right of vertical finder cross hair as sketched use HD209458 and center on this star using the Sky and slew to it. Now can calibrate autoguider using HD 209458 (or Enif?)
4.2.B Return to HD 209458 on imager chip
4.2.C Verify that a guide star is available, select it set autoguider exposure time
4.2.D Turn on autoguiding
4.2.E CCDsoft allows independent control of autoguider exposure times and imager exposure times
4.2.F Take some test images to see if there is drift
4.3 MIRA Software
4.3.A Load a few raw images to see if they are saturated, tailor exposures so that the peak value in the brightest star pixel is less than 8000 counts (to avoid non-linearity caused by antiblooming). Keep object star and at least one comparison stars far from CCD edges so that vignetting is minimized and retaiin flexibility as to background aperture sizes and locations.
6.1 MIRA6 reductions
???? - Note the image reduction utilities of CCDsoft are very easy to use and convenient, we used these to perform bias and dark corrections and to flat field.
6.1.A Calibrate images (flat field etc)
6.1.B Load a series of images
6.1.C Choose, Measure, aperture photometry
6.1.D Set image scale and CCD gain
6.1.E Set aperture to about 40, 45, 50? Minimize star aperture to avoid read noise problems
6.1.F Place apertures on the following stars in this order
(picture)
6.1.G hit track (stars) button
6.1.H examine text output look for errors if so troubleshoot
6.1.I save as a file with a descriptive name date, star, aperture sizes
6.1.J use notepad to copy and paste to spreadsheet
6.2 Using the Spreadsheet (MS Excel)
6.2.A Enter the following formulas (or download our Excel template spreadsheet)
(template excel)
Differential magnitude = -2.5 * log10 (star0/ star1+star2 etc)
Drag down to fill in
6.2.B Calculate standard deviation of measurements
6.2.C Plot results
6.2.D If there are outliers look at the images that have them to see if you can tell why. (one likely causes is image motion)
Webmaster: Justin Lacy Last Updated: 9-25-2001