The Isaac Newton Telescope (INT) Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is a 1800‐deg2 CCD survey of the northern Milky Way spanning the latitude range −5° < b < + 5° and reaching down to r′≃ 20 (10σ). Representative observations and an assessment of point‐source data from IPHAS, now underway, are presented. The data obtained are Wide Field Camera images in the Hα narrow‐band, and Sloan r′ and i′ broad‐band filters. We simulate IPHAS (r′−Hα, r′−i′) point‐source colours using a spectrophotometric library of stellar spectra and available filter transmission profiles: this defines the expected colour properties of (i) solar metallicity stars, without Hα emission, and (ii) emission‐line stars. Comparisons with observations of fields in Aquila show that the simulations of normal star colours reproduce the observations well for all spectral types earlier than M. A further comparison between colours synthesized from long‐slit flux‐calibrated spectra and IPHAS photometry for six objects in a Taurus field confirms the reliability of the pipeline calibration. Spectroscopic follow‐up of a field in Cepheus shows that sources lying above the main stellar locus in the (r′− Hα, r′−i′) plane are confirmed to be emission‐line objects with very few failures. In this same field, examples of Hα deficit objects (a white dwarf and a carbon star) are shown to be readily distinguished by their IPHAS colours. The role IPHAS can play in studies of spatially resolved northern Galactic nebulae is discussed briefly and illustrated by a continuum‐subtracted mosaic image of Shajn 147 (a supernova remnant, 3° in diameter). The final catalogue of IPHAS point sources will contain photometry on about 80 million objects. Used on its own, or in combination with near‐infrared photometric catalogues, IPHAS is a major resource for the study of stellar populations making up the disc of the Milky Way. The eventual yield of new northern emission‐line objects from IPHAS is likely to be an order of magnitude increase on the number already known.

We present a catalogue of point‐source Hα emission‐line objects selected from the INT/WFC Photometric Hα Survey (IPHAS) of the northern Galactic plane. The catalogue covers the magnitude range 13 ≤r′≤ 19.5 and includes Northern hemisphere sources in the Galactic latitude range −5° < b < 5°. It is derived from ∼1500 deg2 worth of imaging data, which represents 80 per cent of the final IPHAS survey area. The electronic version of the catalogue will be updated once the full survey data become available. In total, the present catalogue contains 4853 point sources that exhibit strong photometric evidence for Hα emission. We have so far analysed spectra for ∼300 of these sources, confirming more than 95 per cent of them as genuine emission‐line stars. A wide range of stellar populations are represented in the catalogue, including early‐type emission‐line stars, active late‐type stars, interacting binaries, young stellar objects and compact nebulae. The spatial distribution of catalogue objects shows overdensities near sites of recent or current star formation, as well as possible evidence for the warp of the Galactic plane. Photometrically, the incidence of Hα emission is bimodally distributed in (r′−i′). The blue peak is made up mostly of early‐type emission‐line stars, whereas the red peak may signal an increasing contribution from other objects, such as young/active low‐mass stars. We have cross‐matched our Hα‐excess catalogue against the emission‐line star catalogue of Kohoutek & Wehmeyer, as well as against sources in SIMBAD. We find that fewer than 10 per cent of our sources can be matched to known objects of any type. Thus IPHAS is uncovering an order of magnitude more faint (r′ > 13) emission‐line objects than were previously known in the Milky Way.

The UV-Excess Survey of the Northern Galactic Plane images a 10 • ×185 • wide band, centered on the Galactic Equator using the 2.5m Isaac Newton Telescope in four bands (U, g, r, Hei5875) down to ∼21 st-22 nd magnitude (∼20 th in Hei5875). The setup and data reduction procedures are described. Simulations of the colours of main-sequence stars, giant, supergiants, DA and DB white dwarfs and AM CVn stars are made, including the effects of reddening. A first look at the data of the survey (currently 30% complete) is given.

The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey being carried out in Hα, r and i filters, with the Wide Field Camera (WFC) on the 2.5-m Isaac Newton Telescope (INT) to a depth of r = 20 (10σ ). The survey is aimed at revealing the large scale organization of the Milky Way and can be applied to identifying a range of stellar populations within it. Mapping emission line objects enables a particular focus on objects in the young and old stages of stellar evolution ranging from early T-Tauri stars to late planetary nebulae. In this paper we present the IPHAS Initial Data Release, primarily a photometric catalogue of about 200 million unique objects, coupled with associated image data covering about 1600 deg 2 in three passbands. We note how access to the primary data products has

We report on the properties of 71 known cataclysmic variables (CVs) in photometric Hα emission‐line surveys. Our study is motivated by the fact that the Isaac Newton Telescope (INT) Photometric Hα Survey of the northern galactic plane (IPHAS) will soon provide r′, i′ and narrow‐band Hα measurements down to r′≃ 20 for all northern objects between − 5° < b < +5°. IPHAS thus provides a unique resource, both for studying the emission‐line properties of known CVs and for constructing a new CV sample selected solely on the basis of Hα excess. Our goal here is to carry out the first task and prepare the way for the second. In order to achieve this, we analyse data on 19 CVs already contained in the IPHAS data base and supplement this with identical observations of 52 CVs outside the galactic plane. Our key results are as follows: (i) the recovery rate of known CVs as Hα emitters in a survey like IPHAS is ≃70 per cent; (ii) of the ≃30 per cent of CVs which were not recovered ≃75 per cent were clearly detected but did not exhibit a significant Hα excess at the time of our observations; (iii) the recovery rate depends only weakly on CV type; (iv) the recovery rate depends only weakly on orbital period; (v) short‐period dwarf novae tend to have the strongest Hα lines. These results imply that photometric emission‐line searches provide an efficient way of constructing CV samples that are not biased against detection of intrinsically faint, short‐period systems.