Pre-Analyze command (Research | Analyze Folder of Images)

Adding astrometry to each individual image, one at a time, would be a tedious process. To make this process faster and easier, many of the tools available on the Research menu can also operate on all of the images in one or more folders. These folder-based tools are located on a submenu of the Research menu, at Research | Analyze Folder of Images. The available tools are:

• Pre-analyze – Add astrometric and/or WCS coordinates to one or more folders of images and/or create an inventory of objects on the images.

• Minor Planet Search – Scan three or more images (or multiple groups of three or more images) for evidence of minor planets. Optionally, generates Minor Planet Center observations reports.

• Supernova Search – Scan a folder of images for evidence of supernovas.

• Minor Planet Light Curves – Analyze a folder of images, and construct a light curve for a moving object.

• Variable Star Light Curves – Analyze a folder of images, and construct a light curve for a stationary object.

The first step for both searches and light curves is always to pre-analyze the image files. The following section explains why this is necessary, and how you do it.

The advanced research tools included in CCDSoft version 5 use astrometric and photometric information to accomplish their tasks. For example, the minor planet search identifies the right ascension and declination coordinates of the candidate object in each image, and uses that information to build a submission form, which you can send to the Minor Planet Center. The MPC uses the coordinate information to help construct an orbital profile for the object, among other things. Without the astrometric information, this would not be possible.

Folders button

Click this button to add or remove folders of FITS data to analyze.

The astrometric and/or photometric data is also used in the analysis itself. For example, when building a light curve for a variable star, the brightness of selected stars in the image is used to build the light curve.

Historically, the process of reducing the data from an imaging system involved many separate steps and painstaking attention to detail, not to mention an enormous amount of time. It could take several days to reduce a night’s worth of images to hard data. This data reduction involved many different areas of expertise and often the use of pencil and paper or calculators.

CCDSoft does away with the drudgery. CCDSoft automates many steps in the process, such as organizing images, performing astrometry, calculating magnitudes, graphing data, etc. In addition, CCDSoft organizes the data for you. When you do need to be involved, such as when using the blink comparator to locate minor planets, you can rely on CCDSoft to present the information and images to you in a logical fashion.

All of the advanced research tools operate on a folder of images. The first step in the research process is to copy the files you want to analyze into one or more folders that contain only the images you want to analyze.

Once your images are in place, begin by clicking Research | Analyze Folder of Images | Pre-analyze, which displays the Data Analysis panel with the Pre-analyze tab active. There are several options on the left side, and an Image list on the right side. The options on the left are applied to the images on the right.

A typical pre-analysis run consists of these steps:

1. Use the Folders button to select one or more folders containing the images you want to pre-analyze.

2. Optional: Click Open to verify that the images are the ones you want.

3. Set options, including the three checkboxes and the Image scale.

4. Click Start to begin pre-analysis.

There are three check boxes and a text box on the Pre-analyze tab:

Insert WCS/AutoAstromety – This option performs the same functionality as the Research | Insert WCS/AutoAstrometry command. It uses TheSky’s Image Link and CCDSoft's source extraction to generate an astrometric solution. The Use faint stars option is automatically off. When this box is checked, Pre-Analysis will add the WCS information to the header of the image files in the Image list.

Generate celestial object inventory – This option, when checked, causes a .SRC file to be created and written to disk, with the same name as the image file. This is the most computationally intensive Pre-analyze function. The .SRC file is necessary for performing minor planet searches since images are scanned for moving objects, and this function creates the list of objects. You can add WCS coordinates without creating a .SRC file, but a less rigorous algorithm is used for finding objects, and the fainter stars will be ignored. The .SRC file allows for a larger number of stars to be used in the astrometric solution because the Source Extractor function locates even the faintest of sources. See below for a sample of the contents of an .SRC file.

Overwrite existing WCS solution – When checked, images that already have an existing astrometric solution are re-analyzed, and the new solution replaces the old solution.

Image Scale (arcsecs/pixel) – This is the same as the Image Scale in the AutoAstrometry dialog box. See that section earlier in this chapter for details on how to calculate your image scale. The image scale must be within approximately 0.25 arcseconds of actual image scale to enable astrometry to succeed.

In addition, there are five buttons on the Pre-analyze tab:

Start – Begin the pre-analyze process.

Folders – Displays a dialog that allows you to choose one or more folders for pre-analysis. The folder(s) should contain only images relevant to the current analysis task. See the detailed information later in this chapter for details on what kinds of images to include for each research task.

Click Add to navigate your hard drive. Click Remove to remove the selected folder(s) from the list.

Refresh – Rescan the list of files in the current folder(s). Click this button when you add/remove/change files in the folder(s) in the Image list.

Open – Open the currently highlighted image file. If no image file is highlighted, the first image is opened. This is a convenient way to check your images visually.

Abort – Stop pre-analysis. Disabled except during a pre-analysis run.

There are two progress bars just to the left of the Abort button. They show progress on the current file and on the entire pre-analysis run.

A typical pre-analysis run starts with selecting the folder(s) where the images are located. To select one or more folders, click Folders. This opens the Folder dialog. Click Add to add a folder. You will see a list of drives/folders on your computer. Simply navigate to the folder you want to add, and then click OK to add it. The folder path appears in the Folders dialog. Repeat this process if you need to add more than one folder of images.

Source Extraction Setup dialog box