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.
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
Click on a thumbnail to
enlarge
Click again to shrink down |
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
λ¸f(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.
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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
Click on a thumbnail to enlarge
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
λ¸f(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 Ê,
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.
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