MISAO Project

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February 7, 2001

    MISAO Project with PIXY System 2 starts    

MISAO Project Announce Mail (February 7, 2001)

Hello. I am Seiichi Yoshida working on the MISAO project.

At the beginning of the 21st century, the MISAO Project begins to operate all of the activities with the PIXY System 2.

The PIXY System 2 is still on the way of development. Many functions are not yet implemented. Some functions are implemented but no graphical user interface (GUI) is not yet provided. However, some of the MISAO Project activities, as enumerated below, which have been operated using the old PIXY System 1, are ready to run also using the PIXY System 2.

  • Examine the image and obtain the image information, such as the R.A. and Decl. of the center, the field of view, the limiting magnitude, etc.
  • Measure the R.A. and Decl., and the magnitude of all stars in the image field.
  • Compare overlapping images and discover new variable stars.

Unfortunately the database is not yet ready, we cannot operate the following activity still now using the PIXY System 2.

  • Measure the magnitude of known variable stars and report to the VSNET (Variable Star Network) and VSOLJ (Variable Star Observers' League in Japan).

Starting activities with the PIXY System 2, we examine not only the new images offered to the project after this using the new system, but also re-examine all of the past images using the PIXY System 2 which have been examined using the old PIXY System 1. There are two reasons for the decision. One is, all of the data format is changed in the PIXY System 2. Another one is, the examination result by the new system is refined better than that by the old system.

The PIXY System 2 adopts the XML (eXtensible Markup Language) as the data storage format. In the old system, the examination result is saved in the PXF format, the original format of the PIXY System. The PXF format has some disadvantages, such as lack of uniformity, no guarantee for invertibility between the data on memory and data stored in the file, and so on. The XML solves these problems and increases the availability. The data access from the GUI becomes simple and easy.

Other files in the database of the known variable stars or the database of the measured magnitude, and the batch files to operate the examination in batch mode, are also in the original format, different formats one another. But in the PIXY System 2, everything is recorded in the XML format.

The contents in the data are also reinvestigated. For example, the catalog name of the reference stars for photometry and the CCD chip name are also attached to the magnitude data, although only the filter code is attached in the old system.

The examination process of the PIXY System 2 is also refined in the following two points.

  1. Measure the true center of a luminous blooming star.
  2. Restrict the too much deblending of a star.

In the old system, the position of a blooming star is terribly shifted. Therefore all the blooming stars are listed up as "new objects" because there are no data at the measured position in the star catalogs. This problem was solved by applying the blooming cancel filter before examination.

In the old system, a star is sometimes deblended into several parts and detected as several stars, especially in case of out-of-focus images. In this case, the deblended parts are listed up as "new objects" because there are no data at the measured position in the star catalogs. The PIXY System 2 restricts to the deblending, both in case the whole image is out of focus and only part of the image is out of focus.

These two improvements enables another kind of examination for the offered images.

Many stars not recorded in the star catalogs are captured by the CCD images. So it is impossible to search new objects by only comparing to star catalogs. However, when a very bright star, about 6 mag or 7 mag star for example, is found on the image and not recorded in star catalogs, it is probably a real new object like a nova.

Using the old system, many numbers of stars are listed up as new objects by mistake, so it was impossible to pick up real bright stars not recorded in the star catalogs. But using the PIXY System 2, the number of false alarms are much reduced. So now it is possible to check all of the candidates listed up by the system.

As a result, now we can at least check whether a very bright new objects are in the offered images or not even if there are no past images of the same field. On the other hand, many of the offered images had not been checked at all when there were no other overlapping images before.

The success ratio of the image examination by the PIXY System 2 is a bit increased. For instance, when 1119 images were examined using the old PIXY System 1 in last autumn, it succeeded to examine 1082 images of them, so the ratio is 96.6%. On the other hand, when 3737 images are checked in last one month using the new system, it succeeded to examine 3699 images, so the ratio is 98.9%.

After all of the past images are re-examined, all of the magnitude data of variable stars reported to the VSNET and VSOLJ, about 50 thousand data, will be also re-measured and reported again. Now the magnitude measurement of known variable stars are not ready yet. But when it is ready, we will discard all of the old magnitude data and report the new data.

The past MISAO project announce mails are available at:


Seiichi Yoshida

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