David L. Crawford

A CATALOG OF BRIGHT UVBY BETA STANDARD STARS.

An all-sky catalog of bright standard stars is presented for the uvbyβ photometric systems.

UVBY AND BETA PHOTOMETRY FOR STARS IN THE OPEN CLUSTER NGC 1502

New uvby and Beta photoelectric photometry has been obtained for stars in NGC 1502, a young open cluster with relatively high interstellar reddening. It is shown that some of the previous published data for the cluster suffers from small systematic errors. After correction for zero-point differences, the previous data have been combined with the new data and accurate values of the interstellar reddening [E(b-y)=0.54 mag] and distance modulus [(V0-MV=9.71 mag] have been obtained. These are compared with similar values calculated from published UBV photometry and MK spectral types, which agree well with the uvby-Beta analysis. It is found that the reddening is not variable over the cluster field, contrary to previous estimates. The fact that systematic errors exist in precise photometry highlights the importance of a careful selection of standard stars in any photometry of reddened B-type stars.

Calibration Of Intermediate-Band Photometric Parameters and V Sin i Effects

Calibration of four-color and H#x03B2; photometry, in terms of intrinsic color and absolute magnitude, for the B-, A- and F-type stars is about finished, though still subject to small changes. The data for the bright stars in the northern and southern hemispheres and for a number of the brighter open clusters were used in obtaining these calibrations. Some of the data have been published; much more of it will be going to press shortly. The calibration is interesting not only for itself and its applications, but because deviations from it may be due in part to rotational velocity effects.

Four-color and H-beta photometry near SA 57

Stromgren uvby and H-beta photometry has been obtained for 37 stars in and near the region of SA 57, the Selected Area nearest the north galactic pole. These stars can serve as secondary standards for photometric work in this region. Comparisons with previous photometry shows reasonable agreement. The data are analyzed to determine interstellar reddening, metal abundances of the F-type stars, and distances. On the average, the stars are somewhat weak lined, compared to the sun. The reddening is close to zero.

Photometry: a new and important technique

This is one of the review papers celebrating the centenary of the Astronomical Society of the Pacific, see also 004.051. Photometry is a fundamental and important technique in observational astronomy. It has shown remarkable growth over the last 100 years, since the 1889 PASP paper reproduced. The future will be just as remarkable. In spite of the introduction of new detectors, new methods, and new telescopes, many aspects remain the same, such as color systems, extinction corrections, transformations, other necessary reduction techniques, the idea of information resolution, and issues of sensitivity and accuracy.

Photometry: New techniques, an introduction

In most fields of observational astronomy, the new techniques we have now and are developing offer great potentials for more and better data, and thus to increased understanding of the universe about us. Photometry, as perhaps the most fundamental of all the observational tools, is no exception. The next years will be most exciting, but we must always be aware of the potential pitfalls involved with new technology. In fact, the new technologies must be handled with great care in order to insure that our data is really first class. New generation small telescopes can be a great asset, offering great complementarity to the new large telescopes and to space astronomy.

Light pollution and space billboards - what to do?

Astronomy is faced with environmental threats to observational research, such as light pollution and space junk. Space billboards are the latest of these potential serious impacts. There are solutions to most of these issues, but we all have to work together to ensure a positive approach. The International Dark-Sky Association, a membership based non-profit organization offers a route for us all to participate. 1 Operated by AURA, Inc. under cooperative agreement with the National Science Foundation.

Statistics Of Weather Data And Telescope Usage At Kitt Peak National Observatory And Cerro Tololo Inter-American Observatory

Eighteen years of observing data for the largest telescopes at Kitt Peak National Observatory and six years of similar data at Cerro Tololo Inter-American Observatory are given in Tables 1 and 2. Precipitation data for the same period at KPNO are contained in Table 4. Some summaries of these data and a few conclusions useful for telescope design considerations are discussed.