Spectral‐Line Profiles in Daytime Skylight
Bibliographic record
Abstract
The 1.2 m telescope and coudé spectrograph at our Elginfield Observatory was used to investigate the suitability of daytime skylight as a reference spectrum for astrophysical work. We show that with sufficient care, skylight does give the flux (or disk‐integrated) spectrum of the Sun, allowing direct comparison with other stars. The line profiles in skylight become shallower with increasing angular separation from the Sun up to ≈100°, and then for larger angles they deepen slightly again. The amplitude of this variation is typically 3%–4% of the depth of the line. If the profiles are normalized to their central depths, their shapes remain unaltered. This implies that astrophysical analyses based on the shapes of spectral lines or ratios of depths of spectral lines in skylight should not be seriously affected. However, equivalent widths are not conserved; they can be reduced by up to the same 3%–4% unless care is taken to observe the sky close to the Sun or unless the angular variation is measured, as described here, and corrections applied. The skylight variations can be explained as a combination of aerosol and Rayleigh‐Brillouin scattering. There is no discernible dependence with altitude of the Sun, ruling out a significant ground‐albedo effect.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".