ETC Request ID: ACS.im.2252192
Exposure time (seconds) = 1,742.0000
gives: SNR = 9.7438
gives: Time to Saturation (for a single exposure) = 540,487.91 seconds
gives: Optimum SNR = 18.1418
Exposure time calculation HAD WARNINGS.
WARNING MESSAGE: Electrons per pixel due to background (19) is less than the recommended threshold of 30 electrons to avoid poor charge transfer efficiency (CTE). In rare cases, post-flash may be recommended. Please see Section 2.5 of the ACS Instrument Handbook for more information.
| Detailed Information | Count rate | Total counts | Associated noise |
| (e-/s) | (e-) | (e-) | |
| Counts (circle with radius 0.25 arcsec) | |||
| Source | 0.473 | 824.22 | 28.71 |
| Background | 1.793 | 3,123.10 | 55.88 |
| Sky | 0.367 | 639.70 | 25.29 |
| Dark Current | 1.426 | 2,483.40 | 49.83 |
| Post Flash | 0.00 | 0.00 | |
| Read Out | 56.64 | ||
| Total in selected region | 2.266 | 3,947.32 | 84.59 |
| Brightest Pixel (single exposure) | 0.143 | 124.73 | |
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| Global Count Rates | |||
| Source only | 0.550 | 958.343 | |
| Background (sky+dark) | 372,006.438 | 648,035,214.87 | |
| Post Flash | 0.00 | ||
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| Background per unit area | |||
| Sky Background (arcsec-2) | 1.870 | 3,257.965 | |
| Dark Current (arcsec-2) | 7.197 | 12,537.999 | |
| Post Flash (arcsec-2) | 0.00 | ||
| Extraction region | |||
| circle with radius 0.25 arcsec | |||
| Effective Sky Area (pixels) | 80.30 | ||
| Fraction of flux | 0.86 | ||
| Fraction of flux in brightest pixel | 0.22 | ||
| Effective Wavelength | 6584.67 Å | ||
| Instrument name: | ACS |
| Mode: | imaging |
| Detector: | WFC |
| Coronography: | off |
| Bandpass: | [F658N] H alpha (1%) |
| Gain: | 2.0 |
| # Frames: | 2 |
| Post Flash: | 0 e- |
| Target: [point source] | |
| Spectrum: | Castelli-Kurucz Models B5V 15000 4.0 |
| Extinction E(B-V): | None |
| Normalization: | Renormalized to vegamag = 23.03 in filter Johnson/V |
| Redshift: | None |
| Emission Lines: | None |
| Selected background: | |
| Sky Background: | component |
| Earth Shine: | Average |
| Zodiacal Light: | Average |
| Air Glow: | Average |
These results were computed using: ETC version 34.1
