Sky transparency — night of 22–23 September 2026

Cloud arrived at 22:51 — detected by the all-sky camera, independent of N.I.N.A. Before it the sky ran at index 100 (IQR 85–127); after it 110 (IQR 6–128). 35 of 93 light frames landed before the cloud. 54 of 54 failures are attributed to cloud. Guiding ran at 0.65″ RMS before the cloud and 2.13″ after; the worst minute was 28.71″ at 04:22. The 02:37 autofocus run fitted its curve on almost no stars and should not be trusted. The 04:41 autofocus run fitted its curve on almost no stars and should not be trusted. Morning sky flats: 60 frames (H 20, O 20, S 20), 06:00–06:05, auto-exposure 2.1–5.0 s.

Index before 22:51

100 · IQR 85–127

Index after 22:51

110 · IQR 6–128

Cloud onset (all-sky)

22:51 · independent

Errors after onset

54 of 54 · solve + PHD2

Guide RMS

1.65″ · RA 1.16 · Dec 1.18

Normalised transparency index, by filter

100 = that target and filter's own clear‑sky median (this night's own pre-cloud median). Shaded columns are autofocus runs; the first target is named at the top left; ticks along the base are errors.

H α O III S II ▲ Plate solve failed ◆ PHD2 error

All‑sky background brightness

Mean luminance of the upper sky per all‑sky still — independent of anything N.I.N.A. recorded. The camera auto‑exposes, so this is an instrumental number, not photometry.

PHD2 guiding

RMS tracking error per minute from the PHD2 guide log, taken about zero rather than about each minute's mean, so slow drift counts as error. 2423 guide frames over 8.9 h of guiding in 25 sessions; the gaps are slews, dither settles and autofocus runs, when PHD2 was not guiding. PHD2 discarded 422 further frames — usually a lost star. The worst minute (28.71″ at 04:22) is clamped at the top of the plot.

RA RMS Dec RMS ◆ PHD2 error

All‑sky frames at the key moments

Times come from the still filenames, so they line up with the charts exactly.

All-sky at 19:15 — **19:15** · start of night

All-sky at 22:51 — **22:51** · cloud onset

All-sky at 22:24 — **22:24** · peak brightness 124.3

All-sky at 05:42 — **05:42** · end of night

Clear‑sky reference medians

The divisors behind the index — median detected stars per light sub before 22:51.

Target	Filter	Median stars	Frames	Source
NGC 346	H	534	11	tonight, clear frames
NGC 346	O	489	12	tonight, clear frames
NGC 346	S	584	12	tonight, clear frames

Event timeline

All observatory events with their attributed causes.

02:16:34PHD2Guiding stoppedcloud

02:19:14PHD2timed-out waiting for guider to settlecloud

02:29:20solve failedASTAP plate solve failedcloud

02:29:46solve failedASTAP plate solve failedcloud

02:32:42PHD2timed-out waiting for guider to settlecloud

02:37:45solve failedASTAP plate solve failedcloud

02:37:59solve failedASTAP plate solve failedcloud

02:45:30PHD2timed-out waiting for guider to settlecloud

02:47:31solve failedASTAP plate solve failedcloud

02:47:46solve failedASTAP plate solve failedcloud

02:49:48PHD2timed-out waiting for guider to settlecloud

02:54:51solve failedASTAP plate solve failedcloud

02:55:00solve failedASTAP plate solve failedcloud

02:59:52solve failedASTAP plate solve failedcloud

03:00:02solve failedASTAP plate solve failedcloud

03:01:57PHD2timed-out waiting for guider to settlecloud

03:07:03solve failedASTAP plate solve failedcloud

03:07:23solve failedASTAP plate solve failedcloud

03:12:03solve failedASTAP plate solve failedcloud

03:12:17solve failedASTAP plate solve failedcloud

03:19:27solve failedASTAP plate solve failedcloud

03:19:44solve failedASTAP plate solve failedcloud

03:22:31PHD2timed-out waiting for guider to settlecloud

03:27:36solve failedASTAP plate solve failedcloud

03:27:52solve failedASTAP plate solve failedcloud

03:30:18PHD2timed-out waiting for guider to settlecloud

03:35:23solve failedASTAP plate solve failedcloud

03:35:42solve failedASTAP plate solve failedcloud

03:41:25solve failedASTAP plate solve failedcloud

03:41:58solve failedASTAP plate solve failedcloud

03:47:38solve failedASTAP plate solve failedcloud

03:48:11solve failedASTAP plate solve failedcloud

03:52:40solve failedASTAP plate solve failedcloud

03:53:25solve failedASTAP plate solve failedcloud

04:07:41PHD2timed-out waiting for guider to settlecloud

04:12:45solve failedASTAP plate solve failedcloud

04:12:58solve failedASTAP plate solve failedcloud

04:16:09PHD2timed-out waiting for guider to settlecloud

04:21:13solve failedASTAP plate solve failedcloud

04:21:29solve failedASTAP plate solve failedcloud

04:23:59PHD2timed-out waiting for guider to settlecloud

04:29:03solve failedASTAP plate solve failedcloud

04:29:18solve failedASTAP plate solve failedcloud

04:32:15PHD2timed-out waiting for guider to settlecloud

04:36:27PHD2timed-out waiting for guider to settlecloud

04:41:32solve failedASTAP plate solve failedcloud

04:41:49solve failedASTAP plate solve failedcloud

04:49:07PHD2timed-out waiting for guider to settlecloud

04:51:33solve failedASTAP plate solve failedcloud

04:51:56solve failedASTAP plate solve failedcloud

04:55:00PHD2timed-out waiting for guider to settlecloud

04:59:59solve failedASTAP plate solve failedcloud

05:00:20solve failedASTAP plate solve failedcloud

05:02:29PHD2timed-out waiting for guider to settlecloud

All 187 frames (excludes the 60 sky flats — no stars to detect)

Time	Class	Target	Filter	Exp	Stars	HFR	Index
19:14:44	autofocus	NGC 346	L	5s	147	3.49	—
19:14:59	autofocus	NGC 346	L	5s	228	2.48	—
19:15:14	autofocus	NGC 346	L	5s	363	1.94	—
19:15:29	autofocus	NGC 346	L	5s	438	1.77	—
19:15:44	autofocus	NGC 346	L	5s	348	2.21	—
19:16:03	autofocus	NGC 346	L	5s	214	2.96	—
19:16:19	autofocus	NGC 346	L	5s	114	3.98	—
19:16:39	autofocus	NGC 346	L	5s	82	4.29	—
19:16:58	autofocus	NGC 346	L	5s	88	4.06	—
19:17:14	autofocus	NGC 346	L	5s	50	5.13	—
19:17:34	autofocus	NGC 346	L	5s	410	1.77	—
19:24:09	light	NGC 346	H	300s	510	3.54	96%
19:29:10	light	NGC 346	H	300s	521	3.54	98%
19:34:36	light	NGC 346	H	300s	534	3.50	100%
19:39:38	light	NGC 346	H	300s	510	3.64	96%
19:45:49	light	NGC 346	O	300s	363	3.94	74%
19:50:50	light	NGC 346	O	300s	323	4.14	66%
19:56:07	light	NGC 346	O	300s	325	4.24	66%
20:01:08	light	NGC 346	O	300s	325	4.32	66%
20:06:56	light	NGC 346	S	300s	487	4.07	83%
20:11:57	light	NGC 346	S	300s	512	4.03	88%
20:17:28	light	NGC 346	S	300s	498	4.14	85%
20:22:30	light	NGC 346	S	300s	492	4.30	84%
20:28:40	light	NGC 346	H	300s	431	4.47	81%
20:33:41	light	NGC 346	H	300s	395	4.79	74%
20:34:34	autofocus	NGC 346	L	5s	256	2.99	—
20:34:49	autofocus	NGC 346	L	5s	49	7.48	—
20:35:04	autofocus	NGC 346	L	5s	77	5.88	—
20:35:19	autofocus	NGC 346	L	5s	100	4.78	—
20:35:34	autofocus	NGC 346	L	5s	192	3.48	—
20:35:54	autofocus	NGC 346	L	5s	306	2.62	—
20:36:14	autofocus	NGC 346	L	5s	460	2.00	—
20:36:34	autofocus	NGC 346	L	5s	477	2.00	—
20:36:54	autofocus	NGC 346	L	5s	378	2.37	—
20:37:14	autofocus	NGC 346	L	5s	272	3.08	—
20:37:29	autofocus	NGC 346	L	5s	209	3.79	—
20:37:44	autofocus	NGC 346	L	5s	101	5.25	—
20:38:04	autofocus	NGC 346	L	5s	393	2.17	—
20:44:15	light	NGC 346	H	300s	594	3.48	111%
20:49:16	light	NGC 346	H	300s	580	3.55	109%
20:55:09	light	NGC 346	O	300s	492	3.78	101%
21:00:11	light	NGC 346	O	300s	480	3.83	98%
21:06:13	light	NGC 346	O	300s	489	3.83	100%
21:11:14	light	NGC 346	O	300s	462	3.91	94%
21:17:09	light	NGC 346	S	300s	584	3.82	100%
21:22:10	light	NGC 346	S	300s	584	3.87	100%
21:27:42	light	NGC 346	S	300s	575	3.88	98%
21:32:43	light	NGC 346	S	300s	569	3.97	97%
21:38:51	autofocus	NGC 346	H	300s	604	3.68	—
21:39:09	autofocus	NGC 346	L	5s	448	2.17	—
21:39:29	autofocus	NGC 346	L	5s	74	6.51	—
21:39:44	autofocus	NGC 346	L	5s	129	4.91	—
21:39:59	autofocus	NGC 346	L	5s	158	4.04	—
21:40:14	autofocus	NGC 346	L	5s	259	3.01	—
21:40:34	autofocus	NGC 346	L	5s	473	2.06	—
21:40:54	autofocus	NGC 346	L	5s	527	1.93	—
21:41:14	autofocus	NGC 346	L	5s	498	2.10	—
21:41:34	autofocus	NGC 346	L	5s	345	2.80	—
21:41:49	autofocus	NGC 346	L	5s	231	3.70	—
21:42:04	autofocus	NGC 346	L	5s	156	4.55	—
21:42:24	autofocus	NGC 346	L	5s	575	1.79	—
21:48:34	light	NGC 346	H	300s	700	3.27	131%
21:54:06	light	NGC 346	H	300s	720	3.19	135%
21:59:08	light	NGC 346	H	300s	688	3.27	129%
22:05:12	light	NGC 346	O	300s	728	3.25	149%
22:10:13	light	NGC 346	O	300s	617	3.48	126%
22:15:43	light	NGC 346	O	300s	669	3.40	137%
22:20:45	light	NGC 346	O	300s	620	3.46	127%
22:26:48	light	NGC 346	S	300s	782	3.25	134%
22:31:49	light	NGC 346	S	300s	782	3.25	134%
22:32:24	autofocus	NGC 346	L	5s	625	1.73	—
22:32:44	autofocus	NGC 346	L	5s	124	5.45	—
22:32:59	autofocus	NGC 346	L	5s	175	4.21	—
22:33:14	autofocus	NGC 346	L	5s	306	2.91	—
22:33:29	autofocus	NGC 346	L	5s	463	2.15	—
22:33:49	autofocus	NGC 346	L	5s	580	1.81	—
22:34:09	autofocus	NGC 346	L	5s	506	2.06	—
22:34:29	autofocus	NGC 346	L	5s	375	2.68	—
22:34:44	autofocus	NGC 346	L	5s	266	3.42	—
22:34:59	autofocus	NGC 346	L	5s	182	4.34	—
22:35:19	autofocus	NGC 346	L	5s	605	1.81	—
22:41:24	light	NGC 346	S	300s	747	3.30	128%
22:46:25	light	NGC 346	S	300s	740	3.31	127%
22:52:36	light	NGC 346	H	300s	651	3.41	122%
22:57:37	light	NGC 346	H	300s	666	3.35	125%
23:03:13	light	NGC 346	H	300s	710	3.30	133%
23:08:14	light	NGC 346	H	300s	693	3.33	130%
23:14:40	light	NGC 346	O	300s	624	3.46	128%
23:19:41	light	NGC 346	O	300s	696	3.32	142%
23:25:11	light	NGC 346	O	300s	679	3.36	139%
23:30:13	light	NGC 346	O	300s	712	3.34	146%
23:31:24	autofocus	NGC 346	L	5s	546	1.95	—
23:31:44	autofocus	NGC 346	L	5s	89	5.97	—
23:31:59	autofocus	NGC 346	L	5s	151	4.51	—
23:32:14	autofocus	NGC 346	L	5s	268	3.30	—
23:32:29	autofocus	NGC 346	L	5s	347	2.62	—
23:32:49	autofocus	NGC 346	L	5s	585	1.83	—
23:33:09	autofocus	NGC 346	L	5s	561	1.95	—
23:33:29	autofocus	NGC 346	L	5s	431	2.57	—
23:33:44	autofocus	NGC 346	L	5s	317	3.19	—
23:33:59	autofocus	NGC 346	L	5s	211	4.00	—
23:34:19	autofocus	NGC 346	L	5s	570	1.87	—
23:40:24	light	NGC 346	S	300s	774	3.26	133%
23:45:26	light	NGC 346	S	300s	698	3.44	120%
23:51:00	light	NGC 346	S	300s	691	3.36	118%
23:56:01	light	NGC 346	S	300s	814	3.12	139%
00:02:16	light	NGC 346	H	300s	706	3.17	132%
00:07:17	light	NGC 346	H	300s	673	3.30	126%
00:12:53	light	NGC 346	H	300s	708	3.18	133%
00:17:54	light	NGC 346	H	300s	651	3.27	122%
00:24:15	light	NGC 346	O	300s	673	3.24	138%
00:29:16	light	NGC 346	O	300s	664	3.18	136%
00:34:45	light	NGC 346	O	300s	570	3.26	117%
00:39:46	light	NGC 346	O	300s	570	3.16	117%
00:45:35	light	NGC 346	S	300s	655	3.09	112%
00:50:37	light	NGC 346	S	300s	625	3.17	107%
00:56:06	light	NGC 346	S	300s	684	3.09	117%
01:01:07	light	NGC 346	S	300s	685	3.17	117%
01:06:48	light	NGC 346	H	300s	615	3.29	115%
01:11:50	light	NGC 346	H	300s	594	3.28	111%
01:17:23	light	NGC 346	H	300s	697	3.06	131%
01:19:19	autofocus	NGC 346	L	5s	542	1.93	—
01:19:39	autofocus	NGC 346	L	5s	197	3.94	—
01:19:54	autofocus	NGC 346	L	5s	314	2.67	—
01:20:09	autofocus	NGC 346	L	5s	446	2.01	—
01:20:24	autofocus	NGC 346	L	5s	636	1.63	—
01:20:44	autofocus	NGC 346	L	5s	481	2.00	—
01:21:04	autofocus	NGC 346	L	5s	379	2.56	—
01:21:24	autofocus	NGC 346	L	5s	260	3.44	—
01:21:44	autofocus	NGC 346	L	5s	172	4.59	—
01:22:04	autofocus	NGC 346	L	5s	132	5.29	—
01:22:24	autofocus	NGC 346	L	5s	631	1.64	—
01:29:43	light	NGC 346	H	300s	871	2.77	163%
01:36:31	light	NGC 346	O	300s	690	2.73	141%
01:41:32	light	NGC 346	O	300s	496	2.82	101%
01:47:03	light	NGC 346	O	300s	572	2.78	117%
01:52:04	light	NGC 346	O	300s	532	2.81	109%
01:58:24	light	NGC 346	S	300s	553	2.82	95%
02:03:25	light	NGC 346	S	300s	610	2.69	104%
02:09:12	light	NGC 346	S	300s	610	2.74	104%
02:14:13	light	NGC 346	S	300s	563	2.87	96%
02:24:17	light	NGC 346	H	300s	54	6.69	10%
02:29:18	light	NGC 346	H	300s	34	6.14	6%
02:37:44	autofocus	NGC 346	H	300s	10	5.59	—
02:38:09	autofocus	NGC 346	L	5s	30	1.64	—
02:38:29	autofocus	NGC 346	L	5s	3	4.72	—
02:38:49	autofocus	NGC 346	L	5s	6	3.69	—
02:39:04	autofocus	NGC 346	L	5s	10	2.85	—
02:39:19	autofocus	NGC 346	L	5s	14	2.18	—
02:39:39	autofocus	NGC 346	L	5s	23	1.66	—
02:39:59	autofocus	NGC 346	L	5s	26	1.69	—
02:40:19	autofocus	NGC 346	L	5s	15	2.04	—
02:40:39	autofocus	NGC 346	L	5s	11	2.93	—
02:40:54	autofocus	NGC 346	L	5s	9	3.64	—
02:41:14	autofocus	NGC 346	L	5s	23	1.74	—
02:47:30	light	NGC 346	H	300s	37	4.44	7%
02:54:50	light	NGC 346	O	300s	0	0.00	0%
02:59:51	light	NGC 346	O	300s	0	0.00	0%
03:07:00	light	NGC 346	O	300s	0	0.00	0%
03:12:01	light	NGC 346	O	300s	0	0.00	0%
03:19:26	light	NGC 346	S	300s	2	3.94	0%
03:27:34	light	NGC 346	S	300s	12	4.84	2%
03:35:21	light	NGC 346	S	300s	18	5.78	3%
03:41:22	light	NGC 346	S	300s	40	4.23	7%
03:47:36	light	NGC 346	H	300s	52	3.83	10%
03:52:37	light	NGC 346	H	300s	89	3.34	17%
03:58:10	light	NGC 346	H	300s	111	3.28	21%
04:03:11	light	NGC 346	H	300s	127	3.15	24%
04:12:44	light	NGC 346	O	300s	14	4.70	3%
04:21:12	light	NGC 346	O	300s	4	4.83	1%
04:29:01	light	NGC 346	O	300s	1	0.00	0%
04:41:30	light	NGC 346	O	300s	5	5.24	1%
04:41:59	autofocus	NGC 346	L	5s	4	3.30	—
04:42:14	autofocus	NGC 346	L	5s	3	6.01	—
04:42:29	autofocus	NGC 346	L	5s	3	5.07	—
04:42:44	autofocus	NGC 346	L	5s	3	4.63	—
04:42:59	autofocus	NGC 346	L	5s	6	2.84	—
04:43:19	autofocus	NGC 346	L	5s	6	2.80	—
04:43:39	autofocus	NGC 346	L	5s	6	2.95	—
04:43:59	autofocus	NGC 346	L	5s	4	3.58	—
04:44:19	autofocus	NGC 346	L	5s	4	3.99	—
04:44:39	autofocus	NGC 346	L	5s	4	4.43	—
04:44:59	autofocus	NGC 346	L	5s	1	0.00	—
04:45:19	autofocus	NGC 346	L	5s	7	2.61	—
04:51:31	light	NGC 346	S	300s	6	6.27	1%
04:59:57	light	NGC 346	S	300s	6	4.89	1%
05:07:32	light	NGC 346	S	300s	0	0.00	0%

Star counts come from Hocus Focus detection on each saved sub, tagged with the filter in place at exposure start and the target then being imaged. Frames inside completed autofocus runs are excluded. Still capture times come from the AllSky filenames. All times are local.