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 |
Exposure Timings Reported in the LASCO/EIT Science HeaderHere are the timelines for Normal and Cal Lamp Images (CAPS are actions, small are variables).
Normal Imagesstart timeSETUP exp1 OPEN SHUTTER exp2 EXPOSE stop_time CLOSE SHUTTER exp3 CCD READOUT ro_time Differences are reported in the img header as: header exp1 = exp1 - start_time header exp2 = exp2 - exp1 header exposure_dur = stop_time - exp2 header exp3 = exp3 - stop_time header ccd_readout = ro_time - exp3 Here is the IDL code that converts the raw header into FITS keywords: exptime = h.exp_dur/32. IF (h.version GE 1) THEN exp123units = 2048. ELSE exp123units = 32. IF ((h.lp_num NE 5) AND (h.lp_num NE 7)) THEN exptime=exptime+h.exp3/exp123units ; ; 19 Mar 96: Correct for the 32 second jump in the absolute time, ; allowing for the temporary work around ; 01 Aug 96: Don't correct for obe header verison > 1 ; IF (h.version EQ 0) THEN $ IF ( abs(h.exp_dur-h.exp_cmd) GT 3 ) THEN exptime = exptime - 32. fxaddpar,fits,'EXPTIME',exptime fxaddpar,fits,'EXP0',h.exp_dur/32. fxaddpar,fits,'EXPCMD',h.exp_cmd/32. fxaddpar,fits,'EXP1',h.exp1/exp123units fxaddpar,fits,'EXP2',h.exp2/exp123units fxaddpar,fits,'EXP3',h.exp3/exp123units Cal Lamp ImagesC1 Door Lamp C2 Door and Shutter Lamp C3 Shutter Lamp EIT Shutter Lamp start time SETUP exp1 if DOOR_LAMP then OPEN SHUTTER LAMP ON exp2 EXPOSE stop_time LAMP OFF if DOOR_LAMP then CLOSE SHUTTER exp3 CCD READOUT ro_time Differences are reported in the header as: header exp1 = exp1 - start_time header exp2 = exp2 - exp1 header exposure_dur = stop_time - exp2 header exp3 = exp3 - stop_time header ccd_readout = ro_time - exp3
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