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3. Quick start tutorial

This section lets you go through some of the fitsblink functions without reading the rest of the manual, just to get some overview of the available functions.

3.1 Installing and running for the first time

Apart from a working fitsblink program you also need the example images which are distributed together with both binary and source version. In the examples directory you will find the following files:


Go to the examples (/usr/doc/fitsblink3.1/examples if you installed the RPM package) directory and start fitsblink. If the $HOME/.fitsblinkrc file does not exist yet, fitsblink will complain. Just press the OK button and from the Astrometry menu choose the Settings item. Set all of the settings and save them by pressing the Save button. Next time you run fitsblink it should not complain anymore about the missing parameter file.

3.2 First blink

Now press the left Load button and choose 98kd3r5.fts file from the file selector. The image will be loaded and displayed in the blink window. Repeat this procedure with the 98kd3r6.fts file. Now you have two images in the memory and you can blink them just by pressing the Blink button. The images will be alternately displayed on the screen. You can adjust the blinking frequency with the Delay counter. You noticed that the images are not aligned perfectly. So, center a star in the left small window with the magnified image and double-click on it. Four cursor buttons will appear. Click on them until small images are aligned and then press the button with a blue circle. The images will be aligned now. If you look for moving objects, you will find one right to the center of the screen. To stop blinking, press Blink again.

3.3 Star detection

Before you can do astrometry, stars have to be detected. Open the Astrometry menu and choose Detect stars. The detected objects will be marked by red circles. You may want to change sensitivity. Choose Options, change values in the Star counting frame and run Detect stars again. After that, press the Defaults button and detect stars again.

3.4 Matching the catalog

By now you have already detected objects and you want to get the coordinates of that moving object you spotted in the blinking images. Things become a little more real now: you need either GSC 1.1 or USNO SA 1.0 catalog (ACT has for too few stars to be useful here). Typically, you will have them on a CDROM. If you haven't done so before, mount the CDROM somewhere in your file system. Choose the Catalogs item and write in the mounting point of the catalog. Also, press the check button for the catalog you have. Then choose Edit parameters and write in approximate coordinates of the image center: RA=14h50m and DEC=0d22'. Pixel sizes should be already written in: 1.92'' in both directions. Do not forget to press return or tabulator after you write values in the input fields! Now choose Match stars and see what happens. If you followed the previous steps, you should get a successful match with the default parameters regardless whether you used the GSC or USNO SA catalog.

3.5 Reading object positions

As soon you detect stars, you can also get their positions by pressing the RIGHT mouse button when you are close to one of the DETECTED objects. A window with a magnified part of the image around the object position will appear. You will get object x and ycoordinates, as well as object intensity, all in pixel units. If the WCS values are present in the image header or if you made a successful match with catalog stars, you will also see the object's celestial coordinates. For the example image 98kd3r5.fts the coordinates of the moving object are:

Catalog RA Dec.  
GSC-ACT 1.1 14:50:00.60 00:20:27.3  

Please read section 12.2.5 for the meaning of GSC-ACT.

3.6 Astrometry reports

There is another way to get object coordinates: choose the Do astrometry item. You will see the cursor change shape into a cross. Now press the LEFT mouse button on a selected object. An astrometry report window will appear and if you are happy with the measurement, type in the object name and press Accept. For more details about this, see sections 12.3 and 12.6.

3.7 Identifying stars and asteroids

After you detect objects and make a match to the catalog stars, it is possible to check the star catalog numbers. They will appear in the object field after you click on a star. Note that the star will not be identified if it does not lie within the distance from the detected object set in the Options window, which defaults to 1 arcsecond. This especially comes into account for the saturated stars which cause blooming.

For the identification of asteroids you need access to the services provided by the program asteroid_server, written by the same author as fitsblink. There are two uses. One is when you click on a detected object and a small window containing the magnified image of an object appears. Inside this window there is a button Identify. After you press it, fitsblink asks the asteroid_server to send the data for all asteroids within the given distance. It then presents a list of these asteroids together with the distances from the detected object so you can transfer the designation of the (most likely) the closest asteroid to the Object field. More about the asteroid_server in the subsection Asteroids.

3.8 Markers

Another interesting feature of fitsblink are markers. You already saw them if you detected stars and matched them with a catalog. You can find some examples of the use of markers in the file 98kd3r5-98kd3r6.inp. From the command line run
fitsblink -i 98kd3r5-98kd3r6.inp and see what happens.

This concludes the quick overview of the main fitsblink functions.

next up previous contents
Next: 4. Starting fitsblink Up: Fitsblink 3.13 user manual Previous: 2. Installation
Jure Skvarc