Introduction
Summary of LASCO/EIT What is LASCO? What is EIT? (external link) FAQ Realtime Images RealTime Movies (SOHO Movie Theater) Download LASCO Data Data Products Image Gallery Movie Gallery Processing Levels FITS Header Keywords Data Policy Wavelet images/movies Coronal Mass Ejections Eclipse Observations LASCO Calibration LASCO C3 Planet transits (via Sungrazer) Team and Operations Resources LASCO/C1 at MPAe (Germany) LASCO at LAS (France) LASCO Handbook Technical Notes Detailed Documentation Acronyms Solwind Images and CMEs SOHO Home page SOHO and SOHO Instruments Other Solar Satellites and Observatories |
H-Compress Performance During the Nov 6, 1997 X9.4 Solar FlareI had a look at the image processing information in the image headers before and after the flare in the interest of knowing how observing schedules should be modified the next time this happens. . Here is the comparison based on averages of two pre-flare and two post flare images. The pre-flare images had the following characteristics using H-Compress: Uncompressed Compression Scale Factor Size (bytes) Size (bytes) Factor C1 32 119697 835584 6.98 C2 64 267384 1972224 7.38 C3 32 313223 1894400 6.05 Compression Time Post-Flare --------------------------- Camera Compression Time Pre-Flare C1 1.17 C2 1.21 C3 1.19 Compression Size Post-Flare --------------------------- Camera Compression Size Pre-Flare C1 1.28 C2 1.41 C3 1.34 After the flare hit SOHO, we switched to a higher scale factor to get a higher cadence of images. We used a scale factor of 192 (H8) for all images from C1, C2 and C3. this actually lead to a higher cadence than usual since the C1 and C3 had higher compression than usual. Uncompressed Compression Scale Factor Size (bytes) Size (bytes) Factor C1 192 89302 835584 9.36 C2 192 319505 1972224 6.17 C3 192 203568 1894400 9.30 Conclusion: Let's try a scale factor of 128 (H7) next time! Written: 13 Nov 1997 - DW |