Dec
Declination of the position
Data Entry Information:
See the section
Valid Coordinate Format
for information on valid input coordinate formats.
A cone search will be performed using the RA, Dec and Radius specified.
Exposure Time
Actual exposure time for the observation in units of 1000 seconds
Score
The suitability of an observation with respect to the search criteria
It is an attempt on our part to help the user choose which observation
may be most useful to him or her, in case there are several satisfying
the search criteria. The exposure time, instrument and off-axis angle
are used to compute
the score. The higher the score value, the more likely the observation
is to be the one the user wants, but the system is by no means perfect.
We are assuming that users prefer the instruments in the following
(descending) order:
ACIS-I, ACIS-S, HRC-I, HRC-S.
Data Entry Information:
A score of 'Top' will return only the observation with the highest
score
out of those matching the search criteria.
A score of 'All' will return all of the observations (up to 200). For
a name or position search, the results will be ordered by score. For
an observation ID search, the results will be ordered by observation
ID.
Grating
The three types of gratings are:
- NONE: Imaging observation
- LETG: Low Energy Transmission Grating (commonly used with HRC-S)
- HETG: High Energy Transmission Grating (commonly used with ACIS-S)
Instrument
The two Chandra instruments are:
- ACIS (AXAF CCD Imaging Spectrometer)
- HRC (High Resolution Camera)
Each instrument has a spectral (-S) and an imaging (-I) section.
However, the spectral sections may be used in imaging mode - with
apologies for the confusion this may cause.
Name
Name of the observed object
The user may search for matching observations either through the name
of a celestial object or by specifying a position
Data Entry Information:
The user may enter the name of a celestial object. This name will
be looked up in one of the "name resolvers" (NED or SIMBAD) to obtain
its celestial coordinates. Chandra's observation catalog will
then be searched for observations within a given radius from that
position.
Observation ID
Observation identification number
Data Entry Information: The user may ask for a specific
observation if the Observation ID is known.
Observation Type
There are two types of Chandra observations:
- imaging (no spectral grating used)
- spectroscopic (a spectral grating is used and no FITS image is
available)
RA
Right Ascension of the position
Data Entry Information:
See the section
Valid Coordinate Format
for information on valid input coordinate formats. A cone search will
be performed using the RA, Dec and Radius specified.
Radius
Radius for the cone search in arcmin
Valid Coordinate Format
Celestial coordinates may be specified in decimal degrees or in
sexagesimal format (hours/minutes/seconds)
using either colons or spaces as separators. If the user enters decimal
values for RA and Dec, they are assumed to be in decimal
degrees. To specify decimal hours, add "h" or "H" after the
number.
All coordinates are in ICRS (also popularly known as J2000).
Examples:
|
RA
|
Dec
|
System
|
Translation
|
|
20h 51m 06s
|
+30d 41' 00"
|
J2000
|
20 51 06.00 +30 41 00.00 |
|
20 51 06
|
+30 41
|
J2000
|
20 51 06.00 +30 41 00.00 |
|
20:51:06.0
|
+30:41:00.0
|
J2000
|
20 51 06.00 +30 41 00.00 |
|
23.7654
|
+0.6857
|
J2000
|
01 35 03.70 +00 41 08.52
|
|
23.7654h
|
+0.6857
|
J2000
|
23 45 55.44 +00 41 08.52
|
|
18 12.5
|
-12 8.5
|
J2000
|
18 12 30.00 -12 08 30.00
|