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The ING filter database

For this database to be of any use, it is vital that all filter movements are logged into the database immediately after the filter was accessed.

There is also the possibility to use filters available at the NOT, 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 (staff@not.iac.es) 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 special adapter.

Legend of the database.

• 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 archiving purposes.


• 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 filter.


• 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 Reynier Peletier.

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.

• 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.