Introduction

The tables below list which filters are available to observers each night. The filters on the red side must be specified by the observer in the instrument configuration form. The blue side filters are always installed.

Blue Side Filters

The LRIS blue filters lie in the parallel beam directly before the blue camera lens front element. These filters are not the same size as the filters used on the red side, and hence swapping red filters into the blue is not possible. The filter carousel has a capacity of six filters, all blue filters are always available (unless out for service) and need not be specified on the LRIS run configuration form. An exception on the blue side is the private narrow-band filter which requires permission for use. Special care should be taken to match the blue side filter and the dichroic reflectance.

Broadband Imaging Filters
Name Trans Curve
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λEff1
(Å)
FWHM2
(Å)
Measured Manufacturer
u' ASCII TBD 34503 5253
B ASCII-TBD 4370 878
g TBD ASCII 4731 1082
V ASCII-TBD 5437 922
Private Narrowband Imaging Filters
Permission must be obtained from owner before requesting use.
These filters are installed in the Blue Filter Carousel
Name Contact Trans Curve λEff
(Å)
FWHM
(Å)
NB 4170 Wal Sargent-Caltech
Private Narrowband Imaging Filters
Permission must be obtained from owner before requesting use.
These filters are installed in the Grism Carousel and require special handling. If you intend to use one of these filters, please contact your support astronomer to schedule the filter swap.
Name Contact Status
NB 3425 Alice Shapley - UCLA At Keck
NB 3640 Andrew Blaine- Caltech At Keck
NB 4970 Chuck Steidel- Caltech At Keck
NB 4670 Chuck Steidel- Caltech At Keck
NB 4430 Chuck Steidel- Caltech At Keck
NB 4535 Chuck Steidel- Caltech At Keck
NB 4040 Andrew Blain- Caltech with PI
NB 4110 Andrew Blain- Caltech with PI
NB 4325 Chuck Steidel- Caltech At Keck - OUT OF SERVICE due to delamination
Notes:
1. Effective Wavelength (λEff)was computed from the filter transmission f(λ) and detector quantum efficiency s(λ) via the equation:
   λEff = x / y
   where x is the integral of
   λf(λ)s(λ)δλ
   and y is the integral of
   f(λ)s(λ)δλ
where the integrals are computed over the range in wavelength where the transmission was greater than 5% of the peak in transmission. This assumes equal energy at all wavelengths for the source, and neglects the telescope and atmospheric transmission.
2. FWHM represents the full width of the filter transmission curve (not convolved with CCD response) at half peak transmission.
3. Based on the transmission curve supplied by the manufacturer.

Red Side Filters

The LRIS red filters lie in the parallel beam directly before the red camera lens front element. The filters are located behind the dichroic and special care should be taken to match the filter and dichroic transmissions.

Broadband Imaging Filters
Name Trans Curve
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Click again to shrink down
λEff1
(Å)
FWHM2
[Å]
B5 ASCII 4377 909
V ASCII 5473 948
R ASCII 6417 1185
Rs ASCII 6809 1269
I Excel 7599 1225
(698.6-820.4)
Long-Pass Filters
Name Trans
Curve
λcut4
(Å)
FWHM2
[Å]
GG495 ASCII 4936 N/A
OG570 ASCII 5703 N/A
RG850 ASCII 8488 N/A
Private Narrowband Imaging Filters
Permission must be obtained from owner before requesting use.
Name Trans
Curve
λEff1
(Å)
FWHM2
[Å]
NB4000
James Graham (UCB)

Long wavelength leak identified Jul 2008.
ASCII 4001 343
NB53906
Len Cowie & Esther Hu (UH)
Removed From service
ASCII 5402 80
NB6741
Len Cowie & Esther Hu (UH)
ASCII 6736 77
NB8185
Len Cowie & Esther Hu (UH)
ASCII 8187 106
NB8560
Hy Spinrad (UCB)
ASCII 8560 107
NB9135
Len Cowie & Esther Hu (UH)
ASCII 9151 118
NB9148
Alan Stockton (UH)
ASCII 9150 264
NB4325
Chuck Steidel (Caltech)
ASCII 9150 264
Notes:
1. Effective Wavelength (λEff)was computed from the filter transmission f(λ) and detector quantum efficiency s(λ) via the equation:
   λEff = x / y
   where x is the integral of
   λf(λ)s(λ)δλ
   and y is the integral of
   f(λ)s(λ)δλ
where the integrals are computed over the range in wavelength comprising the main passband. This assumes equal energy at all wavelengths for the source, and neglects the telescope and atmospheric transmission.
2. FWHM represents the full width of the filter transmission curve (not convolved with CCD response) at half peak transmission.
3. Because the CCD quantum efficiency has not been measured past 10000 , the integral used to compute the effective wavelength for this filter as truncated at this point and thus is biased toward the blue.
4. Cut-off wavelength at which filter transmission is 50% of peak (neglecting detector response).
5. The B filter has an active area of only 210×210mm on a side. Throughput is diminished at some distance off axis.
6. The NB5390 filter is cracked and has been removed from service.