Astrophotography diagnosis of SH2-114: no defect detected
RawL300s25 sept. 2026
The Doc examined this image of SH2-114 (raw, L, 300s). Estimated overall technical quality: 8/10. No significant defect was found on this acquisition.
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Info
- Cible
- SH2-114
- Date
- 25 sept. 2026, 19:42
- Lune
- Nouvelle lune 0.9% (26.8° d'alt., 50° de la cible)
- Site
- Bortle 2 · rural typique (VIIRS)
- Position
- 21h22m23s · +38°39'51"
Very favorable conditions. Bortle 2 and a near-new moon (0.9% illumination, 26.8° altitude, 50° from the target) mean no significant lunar contribution, which the background map confirms (3% gradient only, R² 0.57, so noise-dominated). For SH2-114, a very faint Ha supernova remnant, this sky is exactly what you need: at Bortle 2 broadband luminance stays usable, whereas under an urban sky it would be drowned. Make the most of this window to stack time, that is the only limiting factor here.
Setup
- Type d'image
- Brut
- Télescope
- EQMod Mount
- Caméra
- ZWO ASI2600MM Air
- Filtre
- L
- Exposition
- 300s
- Phase de lune
- Pleine lune (99 %)
- FOV
- 1.61°
Coherent setup. At 836mm and 0.928"/px with the ASI2600MM you are slightly oversampled relative to the measured FWHM (3.7 px, about 3.4" of effective seeing), which is not penalizing but does allow software bin 2 if you want SNR. The 1.61° field covers SH2-114 properly, the target is fully contained. Settings are healthy: gain 100 unity, offset 50 with zero dark clipping (0%), 0.04% saturated pixels. Two points: the background to black point margin e_margin of 2.2 indicates the exposure is a bit short to be clearly sky-limited at Bortle 2 (normal under a dark sky, you can push to 600s in L if tracking allows), and sensor temperature at 0°C would benefit from dropping to around -10°C to cut dark current.
The diagnosis in detail
Nothing to correct on this sub. The aberration inspector returns a clean verdict without ambiguity: center elongation is 1.07 against a field floor of 1.03, so below the 1.12 monochrome threshold, and corners top out at 1.14 (TL) and 1.13 (TR), which stays within measurement noise. The corner/center FWHM ratio of 1.1 and the asymmetries of 0.021 horizontal and 0.05 vertical are well below the thresholds that would signal tilt or a backfocus error. Visually the panel thumbnails confirm it: cyan ellipses well fitted, round stars from center to all four corners, no radial comet shapes, no astigmatism cross.
On the tracking side, the 20.2° PA dispersion between zones reflects the absence of any preferred elongation direction: no drift, no periodic error, no guiding oscillation over 300s. That is the mark of a well tuned and properly guided mount.
The background is clean as well: a radial profile of +2% at R² 0.39 and a plane of 3% at R² 0.57, two models too weakly correlated to constitute a real gradient or vignetting. The azimuthal anisotropy of 0.01 confirms a radially symmetric, that is to say flat, background. Comparison with the DSS shows the very faint structures in the field match real signal from the region rather than artifacts. The only real lever here is integration time: SH2-114 is an extremely tenuous remnant that will demand several tens of hours, ideally complemented in Ha.
Priority actions
- Accumulate integration time: SH2-114 is very faint, aim for several tens of hours
- Add Ha exposures to bring out the remnant filaments, luminance alone will not be enough
- Lower the sensor temperature to -10°C to reduce dark current
- Consider 600s L exposures under this Bortle 2 sky to better dominate read noise
