Filters

For ING staff

· Filter Database User Guide
· Internal Filter Pages

Contact

Ovidiu Vaduvescu
ING Filter Manager
ovidiuv@ing.iac.es

ING Filters

ING Filters and their Properties
Filter Dimensions
Filter Throughput
AUX Port Imaging
Nordic Optical Telescope Filters

1. ING Filters and their Properties

The ING owns a large collection of broad and narrow band filters for use in a variety of instruments. The following search tool can be used to list the filters and their key properties (e.g. central wavelength, FWHM, throughput and physical dimensions).

ING Filter Database Search Tool

Instrument:

Filter Type:

Availability:

There are three options to refine the search:

Instrument: One can list only those filters that are compatible with a specific instrument. (See below for more details about which filter sizes can be mounted into which ING instruments.)

Filter Type: One can restrict the type of filter that is returned.

Availability: The default options lists only those filters that are 'Currently Available'. Users interested in the properties of withdrawn filters (for which they may have science data) can select the 'No longer available' option. The 'All filters' option will list all filters, regardless of whether or not they are available.

2. Filter Dimensions

The following table summarises the different filter sizes in use and the instruments into which they can be inserted. Sometimes a special adapter is required as an instrument has been designed for a larger filter size. For example, many of the TAURUS filters may be fitted into other instruments such as PFIP in this way.

Type	Current Instruments	Decommissioned Instruments
Round 38mm	WHT: INGRID
Round 50mm	WHT: ACAM, AUX, PFIP^*	Taurus^*, UES
Square 50×50mm	WHT: ACAM, AUX, PFIP^*	JKT imaging
Round 63mm	WHT: ACAM, PFIP^*	Taurus^*, UES
Round 76mm	WHT: ACAM, PFIP^*	Taurus^*, UES
Round 120mm	WHT: ACAM	Taurus^*
Round 125mm	WHT: ACAM, PFIP	Taurus^*
Round 139mm	INT: WFC

Notes: (1) A * next to a particular instrument indicates that the filter will give rise to vignetting; (ii) There are two round optical filters of diameter 25mm and 38mm (serial numbers #1 and #2 respectively) which are fitted in 50×50mm holders.

3. Filter Throughput

The filter throughput data can be accessed by (i) using the 'Filter Database Search Tool' above to list the filters and (ii) clicking on one of the links in the throughput column. Both ASCII tables and graphical representations (png, ps or pdf) are available. In addition, historical records can be accessed here.

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, while in the other dimension it is f/26.1. This will affect the measured central wavelength of interference filters; please consult Appendix D of the "Observers' Guide 1994" for more information regarding the central wavelength of interference filters in an uncollimated beam.

The scanner can only measure up to ~9000 Angstroms. Around this wavelength, noise is apparent in the throughput scans. As a result, some I and Z band scans show local throughputs greater than 100%.

4. AUX Port Imaging

Please note that the filters mounted in the Auxiliary Port Imager (AUX) can only be changed for scheduled AUX runs. At all other times, a set of UBVRIZ filters are mounted.

5. Nordic Optical Telescope Filters

In addition to the ING filter set, it may also be possible to borrow filters from the Nordic Optical Telescope (NOT). Some of their filters are complementary to the ING ones (e.g., the NOT has a collection of 51-mm square redshifted Hbeta and OIII filters while the ING has a set of 51-mm square redshifted Halpha filters). Should you be interested in using one of the NOT filters, please contact the local NOT staff (lstaff@not.iac.es) for permission before proposal submission. (Note that in all cases priority for the filters will go to NOT users.) At the same time, please email the ING filter contact to check whether the filter can be fitted into the required instrument and whether a special adapter is required.