ROSAT Guest Observer Facility

Frequently Asked Questions about ROSAT Data Analysis

The following questions that have been asked often, with the corresponding answers. For the user's reference, the dates of each answere is included. The answers will be updated as necessary.

If you have a question, please e-mail it to

The sources for these answers have included the following: G. Hasinger (MPE), J. Schmitt (MPE), R. Fink (GSFC), D. Burrows (PSU), the GSFC GOFers (M. Corcoran, G. Reichert, E. Schlegel, and J. Turner), and the SAO GOFers (L. David, F. Harnden, F. Seward, and B. Wilkes).

Select one of the following topics:

Source Characteristics

  1. Where can I find information about detected PSPC sources?
  2. Where can I find information about detected HRI sources?
  3. How can I calculate upper limits at a given source position?
  4. What information is available about All-Sky Survey Sources?


  1. Does the background vary in either detector (PSPC, HRI)?
  2. Are there any problems with the background maps?
  3. Where can I read more about the background?
  4. When should I care about the background?


  1. Can I obtain accurate coordinates from the software?
  2. Can I plot in detector coordinates?
  3. Under what conditions do poor aspect errors usually appear, and how good are the attitude solutions?

Data Quality

  1. How can I check the data quality?
  2. Are there specific signs of good data (or, the converse)?
  3. What photons are included in the 'good photon' file?


  1. Is the large variation in the H-V plots real?


  1. How is the source analysis list in the standard output to be interpreted?
  2. What are the count rates listed on the standard strip plots?

Spatial Analysis

  1. How does one put a contour of a second image on top of the displayed image?
  2. How does one mosaic several images?

Spectral Analysis

  1. What problems have been found with the spectral calibration?


  1. (3/31/91) Notice on bug in SASS processing software.
  2. How accurately are the UT times determined?
  3. Has the ROSAT clock lost time?
  4. Where are barycenter corrections applied?
  5. Where are the UTC and satellite information to be found?

Page Author: Michael F. Corcoran

Last modified April 28, 1999

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This file was last modified on Monday, 25-Jun-2012 15:16:20 EDT

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