[vsnet-chat 911] MISAO project (Re: Magnitude Estimates..., etc.)

[Seiichi Yoshida <seiichi@muraoka.info.waseda.ac.jp>]

Dear colleagues,

Let me introduce my MISAO project (Multitudinous Image-based
Sky-survey by Accumulative Observations) and automated matching and
photometry software.

The MISAO project is all-sky survey, especially all-sky rough
photometry. I guess it is like TASS project, but my approach is based
on the already taken images. Measuring all stars within people's
images will yield enormous magnitude data. Can it be regarded same as
all-sky survey? But it is based on multitudinous images, it is not
accurate at all.

Now I released the source package of the PIXY system (Practical Image
eXamination and Inner-objects Identification system), which detects
stars from your image, matches them with catalog data like GSC,
USNO-A1.0, the Tycho Catalog, etc., calculates accurate R.A. and
Decl. of the center of the image, accurate field of view, accurate
position angle of up direction, limiting magnitude, measures
astrometry and photometry of all detected stars, and lists up
candidates of new objects, errors in the catalog, variable stars,
etc., by comparing with catalog data. The package is available at:

  http://vsnet.info.waseda.ac.jp/muraoka/members/seiichi/misao/

The pacakge contains the two softwares:

  - pixy
    It detects stars from the image, matches them with a star catalog,
    and returns astrometry and photometry results of all. In addition, 
    by contrasting them with catalog data, it lists up candidates of
    new objects, errors in catalog and variable stars.
  - catalog_viewer
    It draws a chart using such data as the Tycho Catalog, the
    USNO-A1.0, the Guide Star Catalog 1.2, etc. It can also draws a
    DSS image on background and plots catalog data on it.

The PIXY system in this package is implemented in Java and C
languages. It is for UNIX system. It was developed on Linux system and 
it should run on most of UNIX system. To run it, JDK (1.0 or later) is
required. And the computer must be connected to the Internet because
this software obtains data from various WWW sites all over the world.
Please get the package, read the README file, and then try some sample 
images introduced in the README. 

The magnitude estimation way of the PIXY system is aperture
photometry, not PSF-fitting.

Unfortunately, the supernova magnitude by this system becomes fainter
than true value. That is because the supernova is on the diffused
nebula. It is a common problem on very close double stars (in case of
supernovae, the supernova and the host galaxy becomes very close). In
order to separate properly the two objects, the system makes aperture
size for the two close objects smaller, which causes the magnitude
becoming fainter. 

It has another inclination, magnitude of very faint stars also becomes
fainter than true value. That is because the aperture size of faint
stars are estimated smaller than bright ones. Especially, in case of
diffused faint objects like galaxies or comets, the magnitude become
several mag fainter. However, the positions measured by the software
is very accurate even in case of very faint objects or diffused ones.

I am already running the system to my friends' images. As Dr. Brian
Skiff introduced in [vsnet-chat 897], I could find my suspicious
objects by examing 25 CCD images refering to USNO A1.0 catalog.
The list is available at the MISAO project home page. From 25 images,
magnitude data of 3645 stars are obtained, 459 stars of them are
warned as remarkable objects (maybe variable stars).  The mean
accuracy of photometry is about +/-0.5 mag, that of astrometry is
0.5-1.0 arcsec (the resolution is 1.4 arcsec / pixel). 

How do you think of such a rough but enormous photometry project and
releasing automated matching, photometry and warning software?

Best regards,

--
Seiichi Yoshida
Muraoka Lab., Waseda University, Japan
seiichi@muraoka.info.waseda.ac.jp
http://vsnet.info.waseda.ac.jp/muraoka/members/seiichi/index.html

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