Reference Materials:| Reference Materials: |
AAVSO CCD Pages
An extensive source of information regarding VSO & CCD. The AAVSO's CCD Views online periodical is very useful too. A must read for the latest developments & news!
This page gives information on filter and comparison star selection.
This page has good tips on filter and camera selection.
| Items needed for this tutorial: |
| STEPS: |
1. Get Charts
Get CCD variable star charts from AAVSO (see link to EY Cyg chart above).2. Get Images
Find and image the variables you have charts for. EY Cygni will be used in this tutorial.3. Process Images
Calibrate (at least do dark frames!) and stack your CCD images as required. The EY Cygni CCD image used in this tutorial was created by calibrating a single 30-second image using seven 30-second dark frames.4. Orient the image on screen to match your star chart (pull down the "Image" menu, choose "Flip").
Time 2001 June 26, 7:13 UT Location Oshawa, Ontario, Canada Camera MX916, binned 2x2 Exposure 1 x 30 seconds Calibration Dark frames only
TIP: Rather than using the Histogram Window, just right-click anywhere on the image, left-click on "View range", and choose "Auto".
5. Click on the Stars button.
This displays the Stars Window (shown below).
The Stars window.6. Position the cursor over a comparison star.
The cursor changes from a cross-hairto a circle
when you put it on a star. Clicking will add an entry for this star in the Star Window (you will have to click twice when adding the first star if the focus is still on the Stars window).
AstroArt will draw a green box around each star in the image that has been added to the Star List.
TIP: For close up views of where you are clicking, use the Local Zoom tool. 
The Local Zoom window. EY Cyg is in the cross-hairs.7. Position the cursor over the information for the star in the Star window and right-click to display the shortcut menu.
The Stars window shortcut menu.Choose "Edit". Enter the V magnitude from the chart in the magnitude box that contains the value "0.0".
The Edit Star window.8. Repeat step 7 for the stars that have magnitudes on the star chart.
TIP: If the star you are doing photometry on is too faint to pull into the star list by simply clicking on it, you can "force" AstroArt to select a star: simply drag a little rectangle over the star with the mouse (using the left mouse button) while keeping the SHIFT key pressed down. (Sometimes these rectangles don't appear correctly centered on the stars' centroids but this is a problem of graphical visualization only.) Thanks to Martino Nicolini for this tip!
9. Click on the variable star to add it to the list.
The Stars Window with all comp stars (+) and the variable included.10. Pull down the "Image" menu and select "Photometry" (or press Shift+Ctrl+F12). When the Photometry dialog appears, press the "Calculate" button. You can save the results of the calculation to disk by pressing the "Save" button. Now click the "Exit" button.
The Photometry Window.11. In the Stars dialog, simply read off the calculated magnitude of the variable! In this example, it is 14.67 with an error of 0.08 (see below).
The Stars Window with photometry calculations done.
(The four RA and Dec columns have been hidden in this view.)
TIP: If you click on a star listed in this box, AstroArt will highlight the corresponding star on the image! This is handy for checking the identity of the stars in the list (see graphic below). Conversely, hovering the cursor over a star with a green box will highlight that star's entry in the star list.
Clicking on a star (here on EY Cyg) in the Star List highlights the corresponding star with a crosshair in the image!
TIP: If you right click the Stars window and choose "Save" you can save your star list to disk so you can re-open it later. Similarly, if you want to remove a star on the list, right click and use the "Delete" option. 12. Report Your Results to the AAVSO!
WebObs allows you to submit your results directly to the AAVSO -- they are incorporated into the quick look file every 10 minutes. Way cool!
