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Hubble Space Telescope

S T A N / W F P C 2 - Number 10, November 1995


WFPC2 Linear Ramp Filter tool on the WWW:

by M. McMaster and J. Biretta

A new tool has been installed on the WFPC2 World-Wide-Web pages to help observers in analyzing images obtained with the WFPC2 linear ramp filters (LRF).

The LRFs act as narrow band filters (passband ~1.3%) whose central wavelength is continuously tunable from 3710 to 9762 Angstroms. The central wavelength is determined by the position of the target in the field of view. The new tool allows observers to easily relate position and wavelength.

Given the central wavelength (from phase II instructions) of an LRF observation, the program will return the target location in the WFPC2 field of view (CCD, and X,Y pixel coordinates). The program can also perform the inverse calculation -- given the location of an object in an LRF image, it will compute the effective central wavelength at that field position. This tool is intended for use during data analysis since during proposal development observers only need to specify the desired central wavelength.

Data Quality Assessment of WFPC2 Science Images:

by J. Biretta

The WFPC2 group has begun data quality checking of all science images where WFPC2 is the prime instrument. Hard copies of each image are examined by the Contact Scientist assigned to that proposal, and by Matt McMaster, a specially trained WFPC2 Data Analyst. If any anomalies or problems are found with the data, the program PI will be notified by their Contact Scientist via e-mail, typically within 2 weeks of the observation. The notification messages will include a detailed description of the anomaly, its cause, and, where possible, references for analysis procedures to correct the image. This program follows recommendations of the Data Quality Assessment Project.

Some of these "anomalies" are relatively routine artifacts (eg. "ghosts" from bright stars). In these cases we will inform observers only the first time they occur. We realize that this information may be unnecessary for many experienced users, but in the interest of uniform coverage we are including everyone in this program.

We would like to highlight one particular image anomaly: PC1 Stray light. It appears that light from a bright star which is on the PC pyramid facet, but outside the region imaged by the PC CCD (ie., in the cut-out region around the PC, where the WF1 was originally designed to be) can find its way on to the PC. In the image, this appears as one or more broad arcs of light. In some cases we have seen it as multiple arcs with a softer appearance together with a diffraction spike at the outer edges of the PC.

For further reference on WFPC2 anomalies, please refer to ISR 95-06 "A Field Guide to WFC2 Image Anomalies" .

Paper copies can be requested at

On-line Reference File Summaries Now Accessible via STARVIEW:

by S. Baggett and M. McMaster

The short descriptions for each wfpc2 reference file maintained in the WFPC2 reference file memo on WWW are now also accessible from StarView.

Note: we will continue to keep the WWW listing regularly updated for those users who may prefer to use it rather than the Starview screens.

To view, for example, the descriptions of WFPC2 dark reference files available for calibration, using StarView:

- select the 'Searches' pull-down menu
- choose the 'WFPC2' menu,  
- choose 'Dark Frames'. 

You should then see the WFPC2 Dark Reference Files screen.

Any combination of constraints, such as setting "A-to-D Gain", "Mode" or "Serials" to match those from your science observation, can be entered in the window before executing.

The "Recommended Use After Date" and the "Calib. data taken from" may also be specified. In this case, the date needs to be entered as yyyymmdd and/or wildcarded, as in: "199508*". Recommended reference files are those with "use after" dates prior to and closest in time to the date of the science observation. The "Calib. data taken from" provides the observation dates of the individual dark frames that were used to generate the reference file. Note that the window containing the description (labeled "User Comments") is normally shorter than the description itself, however, the remainder of the line may be viewed by selecting the User Comment window and using the right and left arrow keys to step through it.

New WFPC2 Reports on the WWW:

The following WFPC2 reports are now on-line.

"A Field Guide to WFPC2 Image Anomalies" WFPC2 ISR 95-06 
by J. Biretta, C. Ritchie, and K. Rudloff.

"A Demonstration Analysis Script for Performing Aperture 
Photometry" WFPC2 ISR 95-04 by B. Whitmore and I. Heyer.

"The Geometric Distortion of the WFPC2 Cameras" WFPC2 
ISR 95-02 by R. Gilmozzi, et al.

"Large Angle Scattering in WFPC2 and Horizontal `Smearing' 
Correction" WFPC2 ISR 94-01 by J. Krist and C. Burrows.

"Science with the Second Wide Field Planetary Camera" WFPC2 
ISR 92-04 by J. Trauger, et al.

"WFPC2 Science Observation and Engineering Modes" WFPC2 
ISR 92-03 by J. Trauger and D.I. Brown.

"System Level Contamination Issues for WFPC2 and COSTAR" 
WFPC2 ISR 92-02 by M. Clampin.

The following articles from the recent Calibration Workshop are also available on-line.

"WFPC2 Flat Field Calibration" by J. Biretta.

"WFPC2 Ghosts, Scatter, and PSF Field Dependence" 
by J. Krist.

"A Demonstration Analysis Script for Performing 
Aperture Photometry" by B. Whitmore and I. Heyer

Paper copies of these (or any other) documents can be requested from

Subscribing and Unsubscribing from the WFPC2 News Mailing List:

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Recent Preprints:

We draw your attention to these papers, based on WF/PC and WFPC2 data, that will appear in the next few months. This list includes all preprints received by the STScI Library not yet published in the journals. Please remember to include our Library in your preprint distribution list.

Cowie, L.L.; Hu, E.M.; Songaila, A. "Detection of massive 
forming galaxies at redshifts greater than one" Nature 

Eisenhardt, P.R.; Armus, L.; Hogg, D.W.; Soifer, B.T.; 
Neugebauer, G.; Werner, M.W. "HST observations of the luminous 
IRAS source FSC10214+4724: a gravitationally lensed infrared 
quasar"  ApJ 4-10-96

Forbes, D.A.; Phillips, A.C.; Koo, D.C.; Illingworth, G.D.
"Keck spectroscopy and HST imaging of field galaxies at 
moderate redshift" ApJ accepted

Freedman, W.L.; Madore, B.F.  "The Cepheid extragalactic 
distance scale"  Clusters, Lensing and the Future of the 

Harrington, J.P. "Observations and models of H-deficient 
planetary nebulae" Hydrogen-Deficient Stars 2

Koo, D.C. "A glimpse of field galaxies at redshifts z ~ 1 
using HST and the Keck telescope"  IAU Symp. 171

Filippenko, A.V.; Barth, A.J.; Bower, G.C.; Ho, L.C.; 
Stringfellow, G.S.; Goodrich, R.W.; Porter, A.C. "Was Fritz 
Zwicky's `type V' SN 1961V a genuine supernova?"  AJ 11-95

Schreier, E.J.; Capetti, A.; Macchetto, F.; Sparks, W.B.; 
Ford, H.C. "HST imaging and polarimetry of NGC 5128 
(= Centaurus A)"  ApJ 3-10-96

Stern, D.; Spinrad, H.; Dickinson, M. "HST observations of 
the radio galaxy MG 1136+1346 (z=1.003)"  AJ 1-96


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