Stromgren Filters for the WIYN 0.9-m Telescope

Michael Richmond
June 3, 2013

We have acquired a set of filters for the WIYN 0.9-m telescope which are designed to mimic the Stromgren intermediate-band photometric system. This document presents measurements of the filters made by Flynn Haase on Jan 17, 2013, using the Lambda 9 Spectrophotometer at KPNO.

Each filter was scanned at five positions. The values in the table below were taken from the scans in position 5.

Filter	Central wavelength	FWHM	max transmission
	(Angstroms)	(Angstroms)	(percent)
u	3467	339	34
v	4117	133	65
b	4718	208	88
y	5514	227	85
H-beta narrow	4864	30	78
H-beta wide	4876	139	90
Calcium	3972	96	53

ASCII text files

Click on the links in the table below to download ASCII text files with data from the scans. The format of each file is a header with lines starting with "#", followed by two columns of data in each line: wavelength (Angstroms) and transmission (percent). An example is shown below:

#== Filter Data - Lambda 9 Spectrophotometer ==
#  Kitt Peak National Observatory - NOAO
#------------------------------------------------
#Filter: u_POS1
#Date: 01/16/13   Time: 13:50:29  Operator: FH
#cwl=  3462.33A  fwhm= 338.93A  Tmax= 34.08% at  3450.00A
#Tcutoff=  2.00 %  Slitsize =  3 A
#fwhm spans 3292.86A to 3631.79A
#90%  spans 3319.14A to 3543.95A
#bw90 is  0.663; Tmin90/Tmax is  0.800
#No data smoothing
#
#Npts=  101     Disp= 10.00A/Interval
#*****
  3000.00     0.175
  3010.00     0.295
  3020.00     0.230
  3030.00     0.135

Filter	pos1	pos2	pos3	pos4	pos5
u	u-pos1	u-pos2	u-pos3	u-pos4	u-pos5
v	v-pos1	v-pos2	v-pos3	v-pos4	v-pos5
b	b-pos1	b-pos2	b-pos3	b-pos4	b-pos5
y	y-pos1	y-pos2	y-pos3	y-pos4	y-pos5
H-beta narrow	Hb-n_pos1	Hb-n_pos2	Hb-n_pos3	Hb-n_pos4	Hb-n_pos5
H-beta wide	Hb-w_pos1	Hb-w_pos2	Hb-w_pos3	Hb-w_pos4	Hb-w_pos5
Calcium	Ca-pos1	Ca-pos2	Ca-pos3	Ca-pos4	Ca-pos5

Graphs showing transmission curves

The data labelled "Crawford" is from the paper which defines the Stromgren filter system, Standard stars for uvby photometry by Crawford, D. L., and Barnes, J. V., AJ 75, 978 (1970).

The data labelled "Andover" is based on scans of the filters provided by the supplier, Andover Optical. They sent us a PDF with graphs of the transmission curves; I digitized the graphs and extracted numbers to plot on these graphs. I've scaled some of the Andover transmission values for clarity.

Stromgren u

Stromgren v

Stromgren b

Stromgren y

Narrow H-beta

Wide H-beta

Calcium H and K