Calibrating Science Images on MaxIM DL IP (Image Processing Software)


MaxIM DL image processing software is used to calibrate astronomical images. Astronomers often prefer to come with algorithms on different programming languages to stack a large number of images and remove noises from them. This entry will help astronomy enthusiasts to process images on their computers using the MaxIM DL over  programming languages based on two criteria: easiness and the time it takes to process images. This software requires a few simple steps to follow for creating a calibrated image. To learn more about MaxIM DL software, please click here.

Background

In order to calibrate astronomical images obtained through Charged-Couple Device (CCD) photometry, one needs to shoot three types of correction frames. They are: Bias frames, dark frames and the flat frames. Let’s remind us what the purpose is of taking images of these three different frames. Bias frames are taken to remove the readout noise and computer interference from the picture. Readout noise will give you information on the number of electrons are produced upon signal accumulation on the CCD chip.

In general, all CCD chips are manufactured in a way that already have some offset voltage in them. One needs to remove this preset voltage in order to improve the image quality. Here is a picture of the master bias frame, which was created by combining 10 bias frames of the same exposures.

A Calibrated Bias Frame                                                  A Master Bias Frame

To simply put this, dark frames remove thermal noise from images, which is caused due to temperature difference between the CCD chip and the environment.

Master Dark                                                  A Master Dark Frame

Shooting a flat frame is one of the most difficult tasks. The picture used in this post was taken by illuminating a box. A flat frame gives information on the light path obscured by the dust sitting on the chip.

Master Flat                                         A Master Flat frame taken in R filter

Easiness

Taking bias frames is a must when someone is doing astronomical observations. Bias frames are done in 0 seconds exposure with the camera shutter closed. In order to create a master image on MaxIM DL, one needs to follow these steps:

1. Click on the MaxIM DL launch icon.

2. When the MaxIM DL is open, click on the process menu.

3. Click on set calibration under the process menu.

4. Select the folder which contains bias frames.

5. Click on the auto generated clear old option.

6. Select combine type of the images be median.

In order to create a master dark frame, one can follow the same procedures (1-6). Obviously, one needs to choose the proper folder, which contains dark frames (4) in it. A master flat frame can be created using the same procedures described above, but one needs to keep in mind that color filters response to light differently. That is why we take flat frame exposures in all available filters.

After creating the master frames for three corrections, one can finally calibrate the science image. To achieve it, follow the following steps:

1. Keeping the MaxIM DL window open, click on file.

2. Open images you want to calibrate ( It is recommended to open 20 frames at a time, if your image is 3073X2048 pixels wide).

3. Under the process menu, select calibrate all.

Time

4. Wait when the images are being calibrated. You will have your calibrated science images within two minutes. After this, you are ready to analyze the reduced data. Here is a picture of a calibrated field taken in R Filter.

XX Cyg                              The red star indicates an SX Phoenicis star named  XX Cyg.

Why Choose MaxIM DL

In a nutshell, calibrating science images using MaxIM DL is painless and it reduces noise from the science images fairly quickly. On the other hand, using a freeware such as AstroImageJ performs poorly for reporting detailed information about the steps taken to reduce noises from the images. An experienced programmer will like using programming languages, but the MaxIM DL software offers various statistical tools, which are useful for data analysis.

 

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