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The ING filter database
The ING filter database has an entry for all filters that are
interchangeble between different instruments. The database, which is
displayed under the following links, is updated every time somebody
logs a filter movement into our FILTER ORGANIZER program. This program
is consulted by members of the Support Astronomy Group and by others
that bring filters from one place to another.
For this database to be of any use, it is vital that all filter
movements are logged into the database immediately after the filter
The complete filter database
Broad band filters only (excluding Taurus/WFC filters)
Broad band filters only, sorted on wavelength (excluding Taurus/WFC filters)
Narrow band filters only (excluding Taurus/WFC filters)
Narrow band filters only, sorted on wavelength (excluding Taurus/WFC filters)
Taurus filters only
Taurus filters only, sorted on wavelength
Wide Field Camera filters only
There is also the possibility to use filters available at the
some of which are complementary to
our filters (e.g., NOT has a collection of 51-mm square redshifted
Hbeta and OIII filters, and ING has a collection of 51-mm square
redshifted Halpha filters). If your are interested in using any
filter from the NOT you will need to contact them (firstname.lastname@example.org)
for permission (in all cases priority will go to use of the filters
at the NOT itself). You should also contact the ING staff before
your observing run to see if the filter can be fitted and/or needs a
- Column 1 gives the serial number of each filter. This
number is unique to the filter, and will in the near future be written
to the FITS headers of images taken with the ING instruments. This
will provide useful information to the files, especially for
- Column 2 lists the type or category of the
filter, where 1 stands for broad band filters,
2 for narrowband filters, 3 for Taurus filters, and 4 for Wide
Field Camera filters.
- Column 3 gives the central wavelength and HWHM of the filters.
- Column 4 gives the names of the filter history files which are kept
under the quality account on lpss1. These names are unique for each
- Column 5 gives a further description of the filter.
- Column 6 lists the size of the filter in millimeters. An entry
with two numbers indicates a rectangular filter, one number indicates
the diameter of a circular filter.
- In column 7 the filter thickness is written in mm.
- In column 8 the current whereabouts of the filter is given.
- Column 9 gives the date of last access to the filter.
- Column 10 gives info on the physical state of the filters.
- Column 11 lists information on measured focus offsets
of the filters. We are currently measuring these offsets on sky.
Filter throughput plots and tables.
These can be obtained by clicking the links in columns 3 (PostScript
plot) and 4 (ASCII table). Mariet Broxterman is currently measuring
the filter throughput of our filters; for the filters that haven't
been measured yet see the plots provided by the filter document of
Note that the filter scanner uses a rectangular beam of light to
measure the throughput. In one dimension this beam has a f/9.0 focal
ratio, in the other dimension it has a f/26.1 focal ratio. For
interference filters this will affect the measured central wavelength;
please consult Appendix D of the Observers Guide for more
information regarding the central wavelength of interference filters
in an uncollimated beam.
The scanner can only measure up to about 9000 Angstroms. Around this
wavelength noise is apparent in the throughput scans. Some I and Z
band scans show local throughputs of more than 100% because of this.
AUX Port filters
As of semester 99A the AUX port filters cannot be changed anymore.
The filter setup is as follows: RGO U #202, Harris B #25, Harris V
#30, Harris R #36, Harris I #41. The sixth slot is taken up by the
focus mask with a Kitt Peak V filter (#49) attached to it: this slot
cannot be used for regular observations.
What filters fit in which instruments?
Many of the ING filters are easy to move from one instrument to
another. Often, filters that originally did not fit in an instrument,
can now be put in holders that do fit in that particular instrument.
Knowing this, please note that many filters labelled as 'TAURUS'
filters also fit in other instruments such as the UES.
When marked with an * the filters give rise to vignetting.
Note that for TAURUS it depends on where in the instrument the filters
are put whether they vignet or not. Also note that the round 25mm and
38mm filters (serial #1 and #2) are fitted in 50x50mm holders.
- Round 50mm filters: Taurus*, UES, WHT Prime focus*.
- The square 50x50mm filters: JKT imaging, WHT Aux
Port, WHT Prime Focus*
- Round 63mm filters: Taurus*, UES, WHT Prime focus*.
- Round 76mm filters: Taurus*, UES, WHT Prime focus*.
- Round 120mm filters: Taurus*.
- Round 125mm filters: Taurus*, WHT Prime focus.
- Round 139mm filters: WFC.