Verdict: the flat-calibrated run is healthy. It processed the same 14 lights with no warnings or errors, applied cached dark and flat masters correctly, preserved alignment stability, and measurably improved field and color uniformity.
Note: image measurements are made on ALS final processed PNG outputs, after autostretch/display processing. A stricter scientific validation should also use linear stack outputs.
Run Summary
| Run | Frames | Profile | Dark | Flat | Warnings / Errors | Searched ratios | Accepted ratios |
|---|---|---|---|---|---|---|---|
| No flat | 14 | 1 | yes | no | 0 / 0 | 0.1 | 0.1 |
| Flat | 14 | 1 | yes | yes | 0 / 0 | 0.1 | 0.1 |
Visual Comparison
Top-left: no-flat result. Top-right: flat-calibrated result. Bottom-left: signed flat-minus-no-flat difference map, where green means brighter after flat calibration and magenta means darker.
Timing
| Metric | Unit | No flat n | No flat median | No flat mean | No flat min | No flat max | Flat n | Flat median | Flat mean | Flat min | Flat max |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Preprocess | ms | 14 | 4767.672 | 5181.413 | 4333.368 | 6203.659 | 14 | 4912.332 | 4912.196 | 4607.177 | 5333.645 |
| Stack | ms | 14 | 8657.646 | 7958.510 | 3.362 | 9229.913 | 14 | 8773.090 | 8011.137 | 3.304 | 9115.200 |
| Full frame processing | s | 14 | 21.646 | 21.709 | 13.034 | 24.595 | 14 | 22.415 | 21.576 | 13.884 | 22.911 |
| Dark subtraction | ms | 14 | 77.614 | 78.363 | 74.320 | 86.530 | 14 | 78.226 | 79.551 | 75.180 | 90.505 |
| Flat division | ms | 0 | - | - | - | - | 14 | 210.908 | 211.777 | 196.561 | 234.252 |
Per-frame Log Comparison
| Light suffix | No flat matches | Flat matches | No flat sigma | Flat sigma | No flat pre ms | Flat pre ms | No flat stack ms | Flat stack ms | No flat full s | Flat full s |
|---|---|---|---|---|---|---|---|---|---|---|
| 222832_-9.8C_0002.fit | 4402.1 | 5333.6 | 3.4 | 3.3 | 13.034 | 13.884 | ||||
| 223333_-9.8C_0003.fit | 49 | 49 | 4333.4 | 4607.2 | 7565.6 | 7558.1 | 20.348 | 20.530 | ||
| 223634_-9.8C_0004.fit | 48 | 48 | 5832.8 | 4653.1 | 7477.1 | 7733.1 | 21.686 | 20.863 | ||
| 224004_-9.6C_0005.fit | 48 | 48 | 4134744 | 4169664 | 4349.1 | 4747.7 | 8527.7 | 8640.0 | 21.307 | 22.067 |
| 224307_-9.8C_0006.fit | 48 | 48 | 3689124 | 3676487 | 4403.0 | 4791.1 | 8549.6 | 8331.6 | 21.390 | 21.607 |
| 224648_-9.6C_0007.fit | 48 | 48 | 3606377 | 3551057 | 4543.7 | 4910.5 | 8699.1 | 8948.6 | 21.580 | 22.429 |
| 224950_-9.8C_0008.fit | 48 | 48 | 3150390 | 3125878 | 4510.0 | 4933.2 | 8616.1 | 9115.2 | 21.550 | 22.805 |
| 225330_-9.7C_0009.fit | 48 | 48 | 2260493 | 2268038 | 4807.5 | 4849.9 | 8709.8 | 8887.0 | 22.228 | 22.461 |
| 225632_-9.9C_0010.fit | 48 | 48 | 2043357 | 2047372 | 4727.9 | 4869.9 | 8459.7 | 8686.8 | 21.606 | 22.497 |
| 225949_-9.8C_0011.fit | 47 | 47 | 2076855 | 2081296 | 6150.2 | 4914.1 | 8882.0 | 8594.6 | 23.630 | 21.989 |
| 230250_-9.8C_0012.fit | 36 | 47 | 2283513 | 2033256 | 6092.0 | 4980.3 | 8902.0 | 8905.4 | 23.512 | 22.401 |
| 230600_-9.8C_0013.fit | 47 | 47 | 2045477 | 2013209 | 6100.1 | 4914.8 | 8895.7 | 8983.7 | 23.602 | 22.911 |
| 230904_-9.8C_0014.fit | 47 | 47 | 1996733 | 1996719 | 6084.5 | 5041.6 | 9229.9 | 8859.4 | 24.595 | 22.757 |
| 231212_-9.8C_0015.fit | 47 | 47 | 1769000 | 1764679 | 6203.7 | 5223.6 | 8901.5 | 8909.0 | 23.855 | 22.869 |
Final Image Luminance
| Run | Mean | Std dev | p1 | p5 | Median | p95 | p99 |
|---|---|---|---|---|---|---|---|
| No flat | 13197.8 | 5717.1 | 8126 | 8707 | 11811 | 23381 | 40085 |
| Flat | 13200.3 | 5583.7 | 8801 | 9269 | 11838 | 23051 | 39753 |
The calibrated image lifts the dark tail while keeping global brightness essentially unchanged. That is consistent with vignetting/response correction rather than simple brightening.
Field Uniformity
| Region | No flat median / center | Flat median / center | No flat median | Flat median | Flat - noflat median |
|---|---|---|---|---|---|
| center20 | 1.000 | 1.000 | 12944.3 | 12154.0 | -795.7 |
| tl20 | 0.861 | 0.972 | 11145.7 | 11814.0 | 698.0 |
| tr20 | 0.681 | 0.772 | 8815.7 | 9378.7 | 560.3 |
| bl20 | 0.904 | 1.032 | 11697.7 | 12542.7 | 891.7 |
| br20 | 0.693 | 0.803 | 8966.0 | 9760.3 | 809.7 |
| top10 | 0.839 | 0.919 | 10856.0 | 11166.3 | 163.3 |
| bottom10 | 0.857 | 0.951 | 11098.3 | 11558.0 | 536.7 |
| left10 | 0.923 | 1.046 | 11949.7 | 12716.0 | 799.7 |
| right10 | 0.687 | 0.788 | 8893.3 | 9575.0 | 600.3 |
Tile background uniformity
| Run | Mean tile background | Min | Max | Range | CV | p10 | p90 |
|---|---|---|---|---|---|---|---|
| No flat | 11486.1 | 8181.3 | 25278.7 | 17097.3 | 0.2136 | 8948.0 | 13220.4 |
| Flat | 11509.3 | 8857.0 | 24628.3 | 15771.3 | 0.1975 | 9408.7 | 12904.2 |
Color Uniformity
| Metric | No flat | Flat | No flat range | Flat range |
|---|---|---|---|---|
| R | 0.2651 | 0.2459 | 20790.0 | 19357.0 |
| G | 0.1691 | 0.1621 | 13935.0 | 13141.0 |
| B | 0.2097 | 0.1864 | 16694.0 | 14975.0 |
| R/G spatial std | 0.0809 | 0.0701 | ||
| B/G spatial std | 0.0367 | 0.0223 |
Interpretation
The flat-calibrated image darkens the brighter central field and lifts the darker outer field. The strongest measured changes are in the corners and side edges, especially the right edge and both right corners.
Alignment remains stable: all aligned frames accepted at the restored progressive ratio 0.1. Match counts are similar or better with flat calibration; one no-flat frame had only 36 matches where the flat run had 47.
Sigma clipping remains comparable between runs. The calibrated run has a slightly lower average clipped sample count, but the difference is small enough to read as stable behavior rather than a behavior shift.
Source Files
als_noflat.logals_flat.logstack_image_noflat.pngstack_image_flat.pngflat_tests_ab_compare.jpg