Use the Open FITS file command to open one or more FITS files and display their corresponding images in FITS windows similar to the one below. 


Phoranso supports a broad range of FITS files, accomodating pixel values of 8-bit, 16-bit, 32-bit, and 64-bit. Additionally, it supports Bayer Color FITS files, automatically converting them into greyscale images. During this conversion process, Phoranso first renames the original Bayer Color FITS file, preserving the file name while changing the extension into ".bfit". This ensures that the file will be excluded from the Phoranso photometric reduction process. Subsequently, Phoranso assigns the original Bayer Color FITS file's name to the converted greyscale image, which is then utilized throughout the photometric reduction procedure.





Image manipulation


At the bottom of a FITS window are a series of controls:


    • Zoom: choose your preferred zoom factor for displaying the FITS image. Options include 25%, 37%, 50%, 62%, 75%, 87%, 100%, 125%, 150%, 175% or 200%, accessible through the drop-down list.

    • Rotation buttons: rotate the FITS image clockwise or counterclockwise by 90, 180, or return to the default 0 degrees using the appropriate button

    • Contrast slider: adjust the contrast slider to enhance or reduce the contrast in your FITS image.

    • Negative image button: lets you toggle between displaying white stars on a black background or vice versa

    • Show FITS Header button: brings up a window that displays the Keywords, Values and Comment fields present in the FITS Header of your image. You can select multiple rows in the FITS Header window and copy them to the clipboard. This can be done by pressing Ctrl-C or by right-clicking and selecting Copy from the context menu.



    • The Solve and Load catalogs buttons are explained in the sections below.



Image Solving


Click the Solve button to utilize the selected Solver from the Settings dialog box to solve the image. Upon successful completion, the button turns green, and a Solver Results window is presented.





The Solver Results window consists of 2 sections:

    • Solver: this shows the Astrometric solver, Astrometric and Photometric catalogs that have been used in solving the image, next to the number of extracted stars (i.e. stars for which an accurate astrometric position has been found).

    • Image: displays the J2000.0 position of the image center, the image size (in arcmin), the pixel scale (in arcsec), the roll angle (in degrees) and the average FWHM of the image. 

      Note that the PinPoint solver measures the FWHM for the 20 brightest unsaturated stars in the image. Phoranso displays the average value of these 20 measurements in the Avg. FWHM field and uses it further on for photometric calculations when the user selects a Star aperture ring based on "Star FWHM" in the Photometry settings box.

      On the other hand, for all other solvers, Phoranso employs a proprietary algorithm to calculate the Avg. FWHM value. This calculation also involves a maximum of 20 unsaturated stars, but intentionally avoids selecting the brighest ones. The resulting average FWHM is then utilized for photometric calculations when the user selects a Star aperture ring based on "Star FWHM" in the Photometry settings box.


If the Blind solving option is enabled in the Astrometric Solver tab of the File Settings dialog, clicking the Solve button may trigger a blind solve when RA or Dec information is absent from the FITS header. Throughout the blind solve process, an Abort Blind Solve button highlighted in red, will be accessible at the bottom of the FITS window, allowing users to halt the blind solving process at their discretion.


Displaying Photometric catalog information


After solving an image, click the Load catalogs button to retrieve information from the selected Photometric catalog in the Catalogs tab of the File Settings box. The completion of this operation may take a while due to the involvement of multiple catalogs being queried over the internet. It results in two actions:

    • the Solver Results window is updated with information coming from the Photometric catalog displaying the amount of retrieved catalog stars (Nbr of UCAC4 catalog stars, in the example above) and the amount of extracted stars for which corresponding photometric information has been found in the Photometric catalog (Nbr of matched UCAC4 stars, in the example above).

      When using the PinPoint solver, Phoranso also displays the average residual error of the matched stars in arcseconds, in the Matched stars avg. residual field.

    • A row with new controls appears below the image, together with circles being drawn around some stars in the image. Your FITS image will be similar to the one below:




The new controls are:


    • Variable stars: Phoranso looks up all variable stars present in your image and draws a white or yellow colored label centered above the variable star (FS CMi is an example in the image above). Variable star identification is done using the AAVSO VSX catalog. Labels are marked in yellow if a corresponding ID Card exists in Phoranso. In all other cases, labels are marked in white. Click the Variable stars label to turn the labels on or off.

    • Advised compstars: Phoranso marks stars in your image with a green circle, indicating their preference as a reference/check/comparison star for photometry. This is done using the stellar color index of the star, more precisely if the B-V color is between 0.3 and 1.0, the star is considered an advised1 compstar. Click the Advised compstars label to turn the green circles on or off. Users should consider additional criteria when selecting appropriate comparison stars.


    • AAVSO compstar: Phoranso cross-references the AAVSO Variable Star Plotter (VSP) to obtain AAVSO comparison star magnitudes for variable stars in the image. If an AAVSO magnitude is available for a specific star, the value will be displayed above the variable star. Toggle the AAVSO compstar label to show or hide these labels. In the above screenshot, the toggle is off.



Displaying information about an individual star


When hoovering the mouse over a star in a solved FITS window with loaded catalog information, a callout box displays pertinent information about the star, sourced from the astrometric and photometric catalogs, as shown in the example below. If no information is available, no callout box will be shown. The displayed information in the callout box comprises the star name, the J2000.0 coordinates, and magnitudes in various bands, including the B-V color index value, as shown in the image below. 


Hoovering the mouse over a variable star (marked by a white or yellow circle), the callout box displays information about the variable star, as retrieved from the AAVSO VSX database. This comprises the variable star name, the J2000.0 coordinates, variability type, magnitude range, period, and AUID (AAVSO Unique IDentifier).


The visibility of the callout box is controlled through the Star callout section of the Variable ID Card Settings box. In this example, it is set to maximum size.


Next to the callout box, an additional line with relevant information appears immediately below the FITS image. It contains:


    • the pixel coordinates of the star (516, 544 in our example)
    • the pixel value (intensity)
    • the J2000.0 coordinates of the mouse cursor (in which case the coordinates label appears in regular font) or the J2000.0 coordinates of the indicated star (in which case the coordinates label appears in bold font). The latter requires presence of photometric information for the indicated star.
    • the V magnitude of the star
    • the B-V color index of the star
    • the SNR of the star
    • the FWHM or HFD of the star (depending on the selected solver).




Displaying a Context Menu with additional operations


A right mouse click in a FITS window raises a context menu showing additional operations:



    • Show FITS Header: this has the same effect as clicking the Show FITS Header button explained above.

    • Image statistics: displays the Image statistics box, showing the file path of the image, the minimum and maximum pixel values present in the image, as well as the Median, Mean and Standard Deviation values for all pixels in the image.

    • Copy image to clipboard: allows to copy the FITS image itself or the entire FITS window to the Windows clipboard. Use Ctl-V to paste the image in another application.

    • Remove hot pixels: hot pixels are individual pixels in a camera sensor that exhibit anomalously high values compared to their neighbors. Use this menu option to remove hot pixels from your FITS image.

    • Calibrate image: this has the same effect as the Calibrate files operation in the Image processing menu. It requires the presence of a Calibration group. It applies the Calibration Pipeline steps to the image.

    • Solve image: this has the same effect as clicking the Solve Image button explained above.

    • Blind solve image: forces a blind solve of the FITS image, irrespective of the FITS header information and whether the Blind Solving option in the Astrometric Solver tab of the File Settings dialog is enabled or not.

    • Load catalogs: this has the same effect as clicking the Load catalogs button explained above.

    • Crosshair cursor: activates a popup menu offering the choice to display a crosshair cursor in the center of the FITS image (Set at center), or at a specified J2000.0 position, which the user can enter in a separate input box (Set at position). The latter option is available only after the image has been successfully solved. Additionally, users can opt to turn off a crosshair cursor. Below is an example of a Crosshair cursor Set at center.


(1) Based on the AAVSO Sequence Selection and Revision Guidelines