# The DAO photometric system

## Basic Reference

Hill G., Morris S.C., Walker G.A. 1971, Astron. J. 76, 246
## Abstract

Forty-nine stars uniformly distributed in right ascension and north of
declination -10 deg. have been observed over the last two years an average of
40 times each in the five-color system developed at the Dominion Astrophysical
Observatory. The colors are measured with a simultaneous, four-channel
photometer which isolates the Balmer continuum (35), the higher members of
the Balmer series (38), regions matching the B (44) and V (54) filters of
Johnson and Morgan, and two regions (42 and 56) formed by masking half of the
44 and 54 regions. The stars from an unreddened spectral sequence from O9 to
K7 and the observations have been reduced to a self-consistent system. The
standard values of the colors are presented together with the transformation
of c(44-54) to B-V. The zero points for the c(35-44), c(38-44), and c(38-42)
colors have been set at the minima in the plots of these colors against B-V
near B-V=0. The standard deviation of the adopted means for each color is
generally about 0.002. Results for cluster sequences and program stars will
be presented in later papers together with detailed discussions of the
astrophysical significance of the colors.

## Content

## Access to the data and references

## Asiago Database on Photometric System (ADPS)

## Indices and Parameters

C35-44, C38-44, C38-42, C44-54 C45-56
## Filters

**35 : **
- Wavelength limits: 3400 - 3600 Å
**38 : **
- Wavelength limits: 3700 - 3850 Å
**42 : **
- Wavelength limits: 3900 - 4400 Å
**44 : **
- Wavelength limits: 3900 - 4900 Å
**54 : **
- Wavelength limits: 5050 - 5770 Å
**56 : **
- Wavelength limits: 5410 - 5770 Å

## Photomultiplier

- EMI 6256 SA (filter 35)
- EMI 6094 SA (filter 38, 42, 44)
- EMI 9558 QA (filter 54, 56)

## Transformation

To (B-V) in the Johnson system:

Please, send your
commentsto Jean-Claude.Mermilliod@obs.unige.ch

Jean-Claude.Mermilliod@obs.unige.ch

Last update: 21 May 1996