Background and first results from the new AAO/UKST H survey

Tech Pan film as the detector for the UKST H survey

The successful implementation of high resolution, panchromatic Tech Pan film on the UKST, coupled with its peak sensitivity at H was a prime motivation behind the new Galactic Plane survey. Details of the many advantages offered by this remarkable emulsion for general wide field photographic imaging can be found in Parker et al. (1995, 1998) whilst Malin (these proceedings) also describes its suitablity for further contrast enhancement. Generally speaking we have found that in good seeing Tech Pan UKST `R' band exposures go about 1 magnitude deeper than the equivalent standard IIIaF `R' band images with improved imaging, resolution and lower noise characteristics. Comparisons of IIIaF and Tech Pan emulsion sensitivities as a function of wavelength through a 100 Å H filter were obtained with a calibration spectrograph. The results convinced us there was no speed/sensitivity/reciprocity penalty in adopting Tech Pan for use with a narrow-band H filter c.f. IIIaF. It is an ideal wide-field photographic detector for use with an H filter. The associated paper by Masheder, Phillipps & Parker (these proceedings) details the emulsion's specific scientific advantages for undertaking the H survey.

Tech Pan's superiority can also be seen in figure 1a-d, a set of arcminute indentical sky regions from near the centre of 4 UKST exposures of standard galactic plane survey field 213. The top left image (figure 1a) is from the A-grade survey R plate taken with IIIaF emulsion and the OG590 R-band filter with 63 minutes exposure. It has a visual point source detection limit of . The top right is from the equivalent exposure taken with Tech Pan and the new H filter with 120 minutes exposure (figure 1b). The bottom left (figure 1c) is the short-red A-grade survey plate taken with 098-04 fast but coarser grained emulsion with a narrower 630 red filter (600 Å) in 10 minutes exposure. The bottom left (figure 1d) gives the A-grade `I' survey plate taken with IV-N emulsion with a 715 filter and 90 minutes exposure.

  
Figure 1: Direct UKST image comparisons between a standard R-band IIIaF exposure (top left), Tech Pan 2 hour H exposure (top right), short-red (bottom left) and I survey (bottom right)

Prior to the availability of quantitative H data from SuperCOSMOS measuring machine scans of the new films, simple visual examination of these exposures was performed. It is estimated that for point source detection the H 120 minute Tech Pan exposure goes at least 0.5 magnitudes deeper than the short-red and is about 1 magnitude less deep than the R survey but with considerably superior resolution. It is also about 0.5 magnitude deeper than the I survey. We are not yet sky-limited with the 2 hour H exposure.

© Copyright Astronomical Society of Australia 1997