LEARNED IT · 08/26
The Moon is an hour later every night — ask if it's up before debugging anything
Moonrise slips ~50 minutes per night. A black frame and a flat histogram look exactly like a broken rig, and the check that rules it out is free.
The Moon rises roughly 50 minutes later each night. It is the one target whose schedule moves by nearly an hour a day, so "it was bright at this time yesterday" is worthless as a prediction.
What this failure looks like from inside: a black preview and a histogram spiked hard against the left edge. That is indistinguishable from a dead camera, a cap left on, a broken Barlow, or a bad exposure setting — so you go and debug all of them, and every one checks out, which makes it worse rather than better.
Ask "is it even above the horizon?" before touching a single setting. It costs nothing and it is the only check that can rule out the whole class at once.
The cheapest source of truth is your own capture folder: last night's earliest run was 19:19, so tonight is ~20:10. No app, no ephemeris, no internet.
Two follow-ons:
- A darker site is not automatically a better site. Moving out the back to escape a streetlight is worthless if it puts the house between you and an eastern horizon for a target that rises late and stays low.
- This is the same shape as every other trap in this log: the thing that looks like a hardware fault is usually a question nobody asked. See [[usb3-or-no-max-resolution]] and [[inactive-uvc-controls-discard-writes]].