We present photometry and spectroscopy of the soft x-ray transient Aql X-1. Optical photometry during an active state shows a strong (0.6 mag peak-to-peak) modulation at a period of 19 hours. Infrared (K-band) photometry during a quiescent state limits any ellipsoidal variations to < 0.07 mag (peak-to-peak), which implies an inclination i < 31 (90% limit). Spectroscopy in a quiescent state show...

Until recently, it was considered by many that ground-based photometry could not reach the high cadence sub-mmag regime because of the presence of the atmosphere. Indeed, high frequency atmospheric noises (mainly scintillation) limit the precision that high SNR photometry can reach within small time bins. If one is ready to damage the sampling of his photometric time-series, binning the data (o...

We calibrate the photographic photometry of the revised New Luyten TwoTenths catalog (rNLTT) by matching 3448 rNLTT stars to the Sloan Digital Sky Survey (SDSS). The correction is linear in magnitude and goes from zero at V ∼ 14 to 0.32 mag at V = 19, in the sense that rNLTT was previously too bright. The correction implies that the underlying USNO-A2.0 photometry, on which rNLTT photometry is ...

We report on near IR (J and K bands) observations of an 8 × 8 region centered on the poorly studied open cluster King 5, for which only optical photometry existed. Photometry of two nearby fields is also reported. We found that the cluster is of moderate age (1.0 Gyr old), intermediate in age between the Hyades and NGC 752. Combining optical and IR photometry we obtain estimates for the cluster...

This work started by investigating the applicability of the photopic V( ) function to predict visual task performance at mesopic light levels. Visual acuity and pedestrian visibility experiments were carried out in varied lighting and viewing conditions. The results indicated the inadequacy of photopic photometry to characterise the response of peripheral vision at low mesopic light levels. The...

We present broad band surface photometry of the radio galaxy 3C270 (NGC 4261). We find a distinct dust lane in the V −R image of the galaxy, and determine its orientation and size. We use the major axis profile of the galaxy to estimate the optical depth of the dust lane, and discuss the significance of the lane to the shape of the galaxy. Subject headings: Galaxies: active; Galaxies: radio; Ga...

The limiting factor of the accuracy of WFPC2 photometry is the CTE loss, which has increased to the level of 50% or more for faint stars at the top of the chips. I describe recent work on characterizing this effect, and provide improved equations for CTE correction. I also examine issues affecting background measurement, which if not done correctly can introduce artificial nonlinearities into p...

A guide to photometry and visible spectroradiometry

BE PIONEER WORK of Lundegardh (1) established flame photometry as an analytical technic, but widespread interest was not aroused until 1945, when Barnes et al. (2) described a simple instrument which was much faster and at least as accurate as existing chemical methods for the determination of certain metals. A dormant clinical interest in the measurement of serum sodium and potassium was there...