PXF File Format

Japanese version Home Page Updated on February 22, 1999

PXF File Format

Here describes the format of PXF file, created after image examination by the PIXY system. Once a PXF file is created after examination by the PIXY system, all further processes, identification, difference, etc., are executed based on the PXF file.

Descriptions

Here describes the format referring to the example PXF file, sample2.pxf, created after examination of the sample image in Tutorial. Please read this document while also reading sample2.pxf.
* sample2.pxf is a PXF file created after identification.

Input Parameters

[Input Data] image=sample.fts exposure_start=1998 Mar. 7 16:22:27 UT exposure=20.0 sec catalog=[CD-ROM] Guide Star Catalog (ver. 1.1) center=11 48 00.00 +48 00 00.0 pos_error=0.0 deg field_of_view=1.0 deg mirror=n sbig_ratio=n reject_CR=y

In the field of [Input Data], parameters the user input at running the PIXY system are recorded. One parameter for one line. The syntax is "key=value". Please read Input Parameters for meaning of each key.

Image Information

[Image Information] image=sample.fts image_size=400 x 300 exposure_start=1998 Mar. 7 16:22:27 UT exposure=20.0 sec center=11 50 00.78 +48 14 22.9 field_of_view=1.037 x 0.778 deg pixel_size=9.33" / pixel p.a.=99.98 deg limiting_mag=14.40 mag faintest_mag=15.63 mag pos_error=3.25" 2.66" mag_error=+/- 0.20 mag +/- 1.0 at 12.45 mag

In the field of [Image Information], various information about the image, calculated by the PIXY system, are recorded. One data for one line. The syntax is "key=value". The meaning of each key is as follows.

Key Contents

image Filename or URL of the image

image_size Image size (in pixel)

exposure_start Date and time when exposure started

exposure Exposure time

center R.A. and Decl. of the center

field_of_view Field of view

pixel_size Field of view of one pixel

p.a. Position angle of up (0 deg means north is up, 90 deg means east is up)

limiting_mag Limiting magnitude

faintest_mag Faintest magnitude

pos_error Errors of astrometry (Error of R.A., error of Decl.)

mag_error Error of photometry

Limiting magnitude and Faintest magnitude

The faintest magnitude is the magnitude of the faintest one of detected stars. On the other hand, the limiting magnitude means until what magnitude can be detected certainly, determined concidering the error of photometry.

Stars not recorded in star catalog (ND) and stars not detected but recorded in star catalog (NC) are output only brighter than the limiting magnitude. The ND stars fainter than the limiting manitude are not output because they can be noises. The NC stars fainter than the limiting manitude are not output because they cannot be detected naturally.

Error of photometry

The fainter, the larger the error of photometry increases. So the error is expressed in the formula style as follows.

mag_error=+/- 0.20 mag +/- 1.0 at 12.45 mag

Definitely, it consists of two types of errors, magnitude independent error and magnitude dependent error. In case of this example, +/- 0.20 mag means the magnitude independent error, and +/- 1.0 at 12.45 mag means the magnitude dependent error. The magnitude dependent error is the brightness when the error becomes 1.0 mag. This example shows that the error of 12.45 mag star becomes 0.20 + 1.0 = 1.20 mag.

Strictly speaking, these are not errors but the threshold to judge the significant variation of magnitude. Therefore, the value of this error is much larger than the actual error.

Detection Statistics

[Statistics] PS=107 RM=5 RP=2 ND=1 NC=5 NR=3

In the field of [Statistics], the number of detected stars by the PIXY system are recorded. One data for one line. The syntax is "key=value". The meaning of each key is as follows.

Key Contents

PS Stars detected as recorded in star catalog

RM Stars whose brightness differs from that recorded in star catalog

RP Stars whose position differs from that recorded in star catalog

ND Stars not recorded in star catalog

NC Stars not detected but recorded in star catalog

NR Stars not detected but recorded in identification database

Detected Stars Data

PS-00001 O=GSC3452.1353 D| 11 51 57.96 +48 05 19.2 mag= 8.90 x= 164.97 y= 16.10 C| GSC3452.1353 11 51 58.17 +48 05 19.0 8.80 RM-00004 O=GSC3452.1191 V=HT UMA S=IRAS 11455+4848 D| 11 48 14.71 +48 31 25.3 mag= 7.53 x= 288.60 y= 280.24 C| GSC3452.1191 11 48 14.69 +48 31 25.7 8.03 R| HT UMA R.A.=11 48 14.70 Decl.=+48 31 25.6 8.275 - 8.39 1 mag (Hp) Sp:M2III R| IRAS 11455+4848 R.A.=11 48 13.26 Decl.=+48 31 32.4 (33 x 3", p.a.=122) flux(12)=1.65 flux(25)=0.43 flux(60)=<0.4 0 flux(100)=<1.00 5% variable M| O-C(Mag)=-0.50 mag RM-00005 O=GSC3452.1523 N=NGC 3893 N=MCG+08-22-007 S=IRAS 11460+4859 D| 11 48 38.06 +48 42 37.7 mag=11.33 x= 363.94 y= 267.73 C| GSC3452.1523 11 48 38.20 +48 42 38.8 7.52 R| NGC 3893 (galaxy) R.A.=11h48.6m Decl.=+48o43' size=4. 4' mag=11p R| MCG+08-22-007 NGC 3893 R.A.=11 48.5 Decl.=+48 42 11.0 mag R| IRAS 11460+4859 R.A.=11 48 38.05 Decl.=+48 42 38.3 (22 x 7", p.a.=123) flux(12)=0.82 flux(25)=1.13 flux(60)=13.8 0 flux(100)=35.07 4% variable M| O-C(Mag)=+3.81 mag

* Some lines are forced to be folded here.

In the field of [Data], all data of stars detected by the PIXY system and also data of not detected stars. Each star's data are separated by an empty line.

The first line of each star data is the ID for the star. Each data of PS, RM, RP, ND, NC, NR, mentioned above, is numbered sequentially from 1.

Some aliases are recorded after the ID. The syntax of alias is "type=name". Aliases are the name in star catalog or the name of the identified variable star, etc. For details of types, please read Object types in identification database.

The line beginning with D| is data of the detected star. It contains measured R.A. and Decl., measured magnitude, detected positions, etc.

The line beginning with C| is data in star catalog. It contains the name, R.A. and Decl., magnitude, etc.

The line beginning with R| is data of identified known variable star or so.

The line beginning with M| is memo. It is used by the user when recording something in PXF file. The PIXY system also records the difference of position or magnitude in the memo field in case of RM or RP data.

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