Light curves

WARNING: Lxnstack can currently generate lightcurves only for fixed objects like starts, galaxies,...

Abstract

Before you procede, be sure you have loaded and aligned the images you want to use.

The use of raw images is preferred because this images are linear unless the sensor reaches saturation. Infact, if we suppose that N photons hit the pixel P1 on the sensor and 2N photons hit the pixel P2 on the sensor, then in the RAW image if the value of the pixel P1 is X the the value of pixel P2 will be 2X. In 'normal' images (Jpeg, Tiff, ...) this linearity is lost due to the corrections and intepolations applied by the firmware of the camera.

Moreover the use of RAW images coming from sensors equipped with a Bayer matrix is preferred becaus they contain data acquired at the same time from three band I,V,B of visible light ( that in coputer science are called R,G,B)[5] and bolometric magnitudes[6] can be computed. If the sensor is a monochromatic one, it is still possible to generate a lightcurve however the magnitude values will be valid for a specific band of visible light.

Light curves generation

First of all, go to the 'Light curves' section and then add a star using the '+' button. A the name of the new start will appear in the 'stars' list.

After you added one or more stars, you have to place them on the image: select from the list the name of the start you want to place and then click with the right mouse button on the star in the image.

Finally you have to set the valuer for the radiuses 1,2 and 3 so that the star is fully contained in the smaller circle and in the area between the external and the middle circle must be only sky background.

If you want to make a comparative photometric analisys then one or more reference stars with a known magnitude must be set: to do this, select first the name of a star form the star list and check the box on its left side and then enter the value of the magnitude in the 'magnitude' text box.

Now click the 'Light curves' button in the 'Tools' section

and, if needed, chose the stacking method to generate the calibration images. After the end of the generation process, you can display the light curves in the 'lightcurve charts' section.

lxnstack © 2013 Maurizio D'Addona