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How to use Seq Plot

Click on the link below and SeqPlot should launch from the web as a Java program.

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Written by S. Beck
Based on an original program from A. Henden
latest release: April 05, 2011

SXN updated July 2, 2012


This Java application should be platform independent. It accesses a new on-line MySQL database that contains approximately 859,000 stars that have been calibrated at USNO-Flagstaff and Sonoita on at least two nights. You can plot fields using either a field name or by coordinates and field size; you can select stars for a sequence and write them to a text file in the correct format for uploading to VSD.


After downloading and starting the application, you will be presented with a dialog box requesting your AAVSO website login name (observer code) and password. Once entered, this will give you access to the calibration database.

Initially, an output file called calibData.txt will be placed in either /Documents (for Mac users) or your C-drive partition (for PC users). This file will be appended to by default as you save stars. When you start up the program a second time, it will look for the last file used, and give you the option of continuing to append to that file, or creating a new file, for the current session. We recommend creating a new file on new sessions, so that you are not tempted to upload already-existing comparison stars from previous sessions.

There is a small initialization file called seqplotDefault.ini that will be created in the default path. This file contains the current output file name, dot colors, etc. that you have selected.

Field Selection

Once initialized, the program gives you a dialog box into which you can enter either a star's name or coordinates. If you want to find a field by specifying the name of the central star, type in the name of the star, then click "Find RA and Dec for Star". The program will then search the VSX database and return the RA and Dec coordinates which you will be able to see in the boxes below.

Coordinates can be entered in decimal or sexigesimal degrees, with or without the leading plus sign. The field size is in fractional degrees. This entry will be improved at some later stage.

No matter whether you found the RA and Dec by searching on a star's name or by typing in the coordinates yourself, you must then select a "Field Size" for your display and click on "Get Plot."


If stars in the requested field are available in the database, a plot will be shown on your screen. The x axis is RA in arcseconds; the y axis is Dec in arcseconds, with north top and east left. Typically, the field will either be 11x11arcmin or about 20x20arcmin in size. In some cases, multiple positions were used with the same field name; the field will be compressed in one dimension or the other if this is the case, you can tell by the axes scales. Dot sizes reflect brightness; dot color reflects (B-V) values, with blue being (B-V) < 0.4; green 0.4 < (B-V) < 1.1; red (B-V) > 1.1. We can change those limits in the future, but for now, assume that green dots are good for sequence generation.

The whole screen crosshair can be moved by moving the mouse pointer over a star and then left-clicking. The crosshair will center on the star, and the bottom line gives you the information about that star. N is the number of calibrations for that star; Source is the source of the photometry (10 = USNO 1.0m; 18 = SRO). When you find a star that you want to keep, press the "Send to File" button in the lower right. The information for that star will be put in the current output file in VSD comma-delimited format. You can continue through the field, identifying stars, and then either quit or press "Next Star" if you want to work with another field.

While working on a particular field, you can zoom in by putting the mouse on the upper left hand corner of the area you want to select; press and drag to select a region of whatever size and shape that you want, and then release. That area will then be resized to fit the screen. You can press "Zoom Out" to return to the original display.

There is an options pulldown menu in the upper left, in which you can change the dot colors and also print or save the current plot. More options will be made later. The help menu has a copy of this document, plus the list of field names.

Use the normal sequence team guidelines for selecting stars. I suggest having another window open that has the DSS image for the field so that you can check for close companions.


Just press Quit to end the program. You can then upload the output text file to HQ; for now, that means sending it to Arne so that he can batch upload it into VSD.

Known Bugs

This program does not handle the poles gracefully. It also does not handle fields where the RA crosses over the 360-degree boundary. These problems will be fixed soon.

Enjoy, and please give us feedback!