Filters for VISTA

This page is for discussion about further filters for VISTA:

and is maintained by the VISTA PI Jim Emerson

Background There are spaces for 7 filter holders in VISTA's camera, each of which must hold 16 individual filters (one for each of the 16 detectors) (or be opaque). Changing a filter holder involves taking the (3 tonne) camera off the telescope, moving it down to the instrument preparation room, and warming up the complete camera, which, over the whole cycle, takes at least a few days. (Spec is to cycle within 11 days -but it might be more like 8 days made up of 1/2 day to come off telescope, 2 days to warm up, 1 day to open and exchange and pump down, 1 day for outgassing/bakeout pumping at 40C, 3 days to cool down, 1/2 day to go onto telescope). This is a major operation that I suppose ESO will not want to do often! So I expect opportuniites for filter changes to be very limited and most likely to be confined to periods when there is maintenance work which is anyway stopping observations from being made.

Public Survey Filters

The six ESO public Surveys with VISTA are expected to take 5 years to complete and use the following six filter sets.

1) Z (broadband) A filter holder filled with 16 Z filters (provided by Jim Emerson with Queen Mary University of London money) will be publically available. Filter made by REO. Filter holder by UKATC. At VISTA awaiting installation.

2) Y (broadband at 1020nm) A filter holder filled with 16 Y filters (provided by Jim Emerson with VISTA Consortium money) will be publically available. Filter made by . Filter holder by UKATC. Already installed in the camera.

3) J (broadband) A filter holder filled with 16 J filters (provided by the UK VISTA project as a required part of the VISTA Facility) will be publically available. Filter made by . Filter holder by UKATC. Already installed in the camera.

4) H (broadband) A filter holder filled with 16 H filters (provided by the UK VISTA project as a required part of the VISTA Facility) will be publically available. Filter made by . Filter holder by UKATC. Already installed in the camera.

5) Ks (broadband) A filter holder filled with 16 Ks filters (provided by the UK VISTA project as a required part of the VISTA Facility) will be publically available. Filter made by . Filter holder by UKATC. Already installed in the camera.

6) NB1.18 (narrowband) A filter holder filled with 16 NB118 filters (provided by Kim Nilson with Dark Cosmology Centre (Denmark) money). Filter made by NDC. Filter holder by UKATC. Already installed in the camera.

Other Filters for installation

7) NB in Z range A filter holder filled with 8 NBZ1 filters and 8 NBZ2 filters (provided by Hertforshire with Oxford, Edinburgh & Liverpool contact Steve Rawlings). Filter made by NDC. Filter holder by UKATC. Awaiting delivery to VISTA.

Other Filters

ESO will announce the availability of a possible slot for VISTA visitor filters in a future 'Call for Proposals'.

Any questions about use of further filters for VISTA should be directed to the Director of ESO's Paranal Observatory Andreas Kauffer

Filter being acquired by potential users.

Filter sets being acquired for VISTA of which the PI is aware are

Methane Nicolas Lodieu and Eduardo Martin at Tenerife have orered a full filter set for a deep methane survey for brown dwarfs in clusters.

Filters that have been discussed by potential users.

H2(S1) Phil Lucas, Ian Smail and others are considering an application to PPARC for a NB H2 filter for galactic plane studies and extragalactic NB hi-z studies. Arturo Manchado (IAC Tenerife) and Daniel Folha (Centro de Astrofisica de Universidade do Porto) have also expressed an interst in purchasing H2 filters.

Andrea Cimatti may be interested in narrow-band and/or medium-band filters and may start to investigate the possibility to set up a small group of Institutes in Italy (and outside Italy) interested in this possibility.

Purchasing Further Filter sets

Every individual filter in a filter holder will have to use the same integration time (DIT). This puts some limits on any mix of filters available in any filter holder. The design of the default observing blocks has been based on the assumption of all filters being the same, and for other patterns some thought would have to be given to observng strategy.

Sets of 18 (16 + 2 spares) filters have been purchased for the major filters. Each filter must be parfocal with the other filter sets. Each set also requires its own filter holder to be built (filter thicknesses vary, and individual filters should be handled as little as possible). The VISTA PI Jim Emerson can help with technical details of required specifications.

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