- A web based form that will aid you in planning observations of point sources.
This tool is the first in a series of OM web tools to aid users in proposal
Information about the OM Tool
Below is a tool to aid in planning observations of point sources using the Optical
Monitor. On submission the results will return:
- A list of observer inputs.
- The correct filter order.
- The calculated count rate of the source.
- The assumed background count rate. This is calculated from
the combination of zodiacal light, diffuse galactic light, and the average
dark count rate of the detector; and therefore depends upon the position of
- The expected signal to noise of the source.
- The exposure time available per filter once the overheads have been taken
into account, assuming that the UVW2 filter requires twice as much time as the
NOTE: If Image mode or Fast mode are chosen, there are 5 exposures per
- Maximum visual magnitude in each filter.
- Minimum visual magnitude in each filter.
- Exposure time and visual magnitude warnings, if the calculated values do not lie within the recomended limits set out in the XMM-Newton Users'
- Notes on calculations.
The input required from the observer to complete these calculations are as
- Right Assention of the source (units in hours mins, and
- Declination of the source (units in degrees, arcmins and
- The epoch for the right assention and declination coordinates. The
choices given are 2000 or 1950.
- Spectral type of source. The choices include B0, A0, G0, G2, K0, M0, and
white dwarf stars. If your source type does not appear on the list then
please use the closest source type available.
- Visual magnitude (mv) of source, in order to calculate
the expected count rate.
- The filters required for the observation. The use of the following
filters are recommended from the XMM-Newton Users'
The number of filters that can be used is dependant on the total observation
time available to the observer, therefore the number of filters may need to be
reduced from this recommended number.
- UVM2 (first choice)
- UVW1 (second choice)
- U (third choice)
- Total observation time available for the observation. Field Acquisition
(FAQ) time needs to be removed from the total observation time before
submitting the form. The FAQ = 298 seconds. All other overhead times are
taken into account in the calculations so you do not need to subtracted these
- Default mode required for observation. Your choices include:
A full account of each of these modes can be found in the XMM-Newton Users'
- Image mode
- Fast mode
- Full-frame high resolution imaging mode - WARNING due to high overheads
this mode is not recommended in the XMM-Newton Users'
- Full-frame low resolution imaging mode
- User defined mode - assumes one exposure per filter, exposure time
contraints are the same as the Image mode, and window sizes do
not exceed the limits set down in the XMM-Newton Users'
Currently this tool does not give any warnings about other bright
sources that are in close proximity to the coordinates submitted. Maximum and
minimum magnitudes are output to demonstrate the magnitude range allowed in the
Field of View of the Optical Monitor, for the
On submission of this data in the Observational Details
Form , a new web page will be open containing the calculated results.
*Right Ascension and Declination are required for sky maps of the
diffuse galactic background (Lienert, 1998) and zodiacal light background
(Levasseur-Regourd & Dumont, 1980). These maps
are combined with the average dark count rate of the instrument to produce a
total sky background count rate for the signal-to-noise calculation.
Avoiding Errors on Submitting the Form
Here is a list of possible errors that might occur, and how they can be
- If the Total Exposure time is small, a "NaN" response is produced in the
`Signal to Noise' count results. To solve this problem the Total Exposure time
must be greater than 6657 seconds.
- Entering a space (` ') anywhere in a text entry field, whether it is
before, after, or in the middle of a number, will produce a "Bad Request"
error message, so avoid using spaces.
- Comma's (,) within numbers eg. ten thousand written as `10,000', will
result in a "NaN" response in the results, so avoid using comma's.
Leinert, C. et al., 1998, Astr. & Astrophys. Suppl., 127,
Levasseur-Regourd, A. C., & Dumont, R., 1980, Astr. & Astrophys.,
Observational Details Form
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Questions about this OM tool should be addressed to email address.
Last Updated by
T. S. Poole on May 5th 2006