Sky transparency — night of 27–28 September 2026

Cloud arrived at 19:33 — detected by the all-sky camera, independent of N.I.N.A. Before it the sky ran at index 100 (IQR 100–100); after it 100 (IQR 79–107). 1 of 95 light frames landed before the cloud. 3 of 3 failures are attributed to cloud. Guiding ran at 0.83″ RMS before the cloud and 0.93″ after; the worst minute was 11.09″ at 04:54. Morning sky flats: 60 frames (H 20, O 20, S 20), 05:52–06:04, auto-exposure 6.8–18.8 s.

Index before 19:33

100 · IQR 100–100

Index after 19:33

100 · IQR 79–107

Cloud onset (all-sky)

19:33 · independent

Errors after onset

3 of 3 · solve + PHD2

Guide RMS

0.93″ · RA 0.54 · Dec 0.76

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 and dashed vertical rules mark each target change; 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. 2790 guide frames over 8.7 h of guiding in 16 sessions; the gaps are slews, dither settles and autofocus runs, when PHD2 was not guiding. PHD2 discarded 30 further frames — usually a lost star. The worst minute (11.09″ at 04:54) 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 19:20 — **19:20** · start of night

All-sky at 19:33 — **19:33** · cloud onset

All-sky at 04:25 — **04:25** · peak brightness 95.8

All-sky at 05:34 — **05:34** · end of night

Clear‑sky reference medians

The divisors behind the index — median detected stars per light sub before 19:33. M 16 and NGC 2030 had no clear frames tonight and no clear history, so its divisor is its own whole-night median. Its index shows how the sky changed during that target, not how it compared with a clear sky.

Target	Filter	Median stars	Frames	Source
M 16	H	345	1	tonight, clear frames
M 16	O	458	11	whole night, cloud included
M 16	S	743	8	whole night, cloud included
NGC 2030	H	288	24	whole night, cloud included
NGC 2030	O	234	21	whole night, cloud included
NGC 2030	S	301	19	whole night, cloud included

Event timeline

All observatory events with their attributed causes.

04:49:42solve failedASTAP plate solve failedcloud

04:50:05solve failedASTAP plate solve failedcloud

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

All 177 frames (excludes the 60 sky flats — no stars to detect)

Time	Class	Target	Filter	Exp	Stars	HFR	Index
19:20:09	autofocus	M 16	L	5s	355	3.97	—
19:20:23	autofocus	M 16	L	5s	568	2.40	—
19:20:43	autofocus	M 16	L	5s	709	2.09	—
19:21:03	autofocus	M 16	L	5s	665	2.28	—
19:21:23	autofocus	M 16	L	5s	482	3.00	—
19:21:43	autofocus	M 16	L	5s	329	4.04	—
19:22:03	autofocus	M 16	L	5s	244	4.72	—
19:22:23	autofocus	M 16	L	5s	364	3.62	—
19:22:43	autofocus	M 16	L	5s	247	4.80	—
19:23:03	autofocus	M 16	L	5s	178	5.78	—
19:23:23	autofocus	M 16	L	5s	669	2.09	—
19:30:11	light	M 16	H	300s	345	3.56	100%
19:35:12	light	M 16	H	300s	285	3.64	83%
19:40:42	light	M 16	H	300s	281	3.64	81%
19:45:43	light	M 16	H	300s	336	3.62	97%
19:52:00	light	M 16	O	300s	220	3.99	48%
19:57:01	light	M 16	O	300s	273	3.94	60%
20:02:25	light	M 16	O	300s	538	4.06	117%
20:07:26	light	M 16	O	300s	359	4.20	78%
20:13:38	light	M 16	S	300s	418	4.19	56%
20:18:39	light	M 16	S	300s	392	4.58	53%
20:24:13	light	M 16	S	300s	425	4.67	57%
20:29:14	light	M 16	S	300s	480	4.88	65%
20:35:26	light	M 16	H	300s	271	4.83	79%
20:40:27	light	M 16	H	300s	261	4.94	76%
20:41:22	autofocus	M 16	L	5s	390	3.04	—
20:41:42	autofocus	M 16	L	5s	125	7.67	—
20:41:57	autofocus	M 16	L	5s	151	6.05	—
20:42:12	autofocus	M 16	L	5s	235	4.82	—
20:42:32	autofocus	M 16	L	5s	288	3.89	—
20:42:52	autofocus	M 16	L	5s	393	2.95	—
20:43:12	autofocus	M 16	L	5s	503	2.41	—
20:43:32	autofocus	M 16	L	5s	554	2.23	—
20:43:52	autofocus	M 16	L	5s	565	2.31	—
20:44:12	autofocus	M 16	L	5s	425	3.00	—
20:44:32	autofocus	M 16	L	5s	306	3.94	—
20:44:47	autofocus	M 16	L	5s	213	5.08	—
20:45:07	autofocus	M 16	L	5s	586	2.04	—
20:51:17	light	M 16	H	300s	397	3.56	115%
20:56:18	light	M 16	H	300s	347	3.81	101%
21:02:02	light	M 16	O	300s	481	4.09	105%
21:07:03	light	M 16	O	300s	473	4.08	103%
21:12:34	light	M 16	O	300s	495	3.95	108%
21:17:36	light	M 16	O	300s	511	3.90	112%
21:23:48	light	M 16	S	300s	772	3.73	104%
21:28:49	light	M 16	S	300s	768	3.75	103%
21:35:27	light	M 16	S	300s	771	3.70	104%
21:40:28	light	M 16	S	300s	743	3.75	100%
21:46:38	light	M 16	H	300s	372	3.65	108%
21:51:39	light	M 16	H	300s	355	3.76	103%
21:57:10	light	M 16	H	300s	369	3.71	107%
22:02:12	light	M 16	H	300s	366	3.72	106%
22:08:46	light	M 16	O	300s	446	3.99	97%
22:13:48	light	M 16	O	300s	407	4.08	89%
22:14:47	autofocus	M 16	L	5s	412	2.24	—
22:15:02	autofocus	M 16	L	5s	100	6.51	—
22:15:17	autofocus	M 16	L	5s	147	5.07	—
22:15:32	autofocus	M 16	L	5s	207	3.85	—
22:15:47	autofocus	M 16	L	5s	282	2.97	—
22:16:07	autofocus	M 16	L	5s	401	2.25	—
22:16:27	autofocus	M 16	L	5s	439	2.10	—
22:16:47	autofocus	M 16	L	5s	396	2.36	—
22:17:07	autofocus	M 16	L	5s	352	2.91	—
22:17:22	autofocus	M 16	L	5s	229	4.07	—
22:17:37	autofocus	M 16	L	5s	166	4.97	—
22:17:57	autofocus	M 16	L	5s	440	2.06	—
22:24:03	light	M 16	O	300s	458	3.77	100%
22:47:42	autofocus	NGC 2030	L	5s	164	2.19	—
22:47:57	autofocus	NGC 2030	L	5s	61	4.60	—
22:48:12	autofocus	NGC 2030	L	5s	96	3.18	—
22:48:27	autofocus	NGC 2030	L	5s	143	2.42	—
22:48:42	autofocus	NGC 2030	L	5s	191	2.01	—
22:49:02	autofocus	NGC 2030	L	5s	168	2.21	—
22:49:22	autofocus	NGC 2030	L	5s	146	2.63	—
22:49:42	autofocus	NGC 2030	L	5s	106	3.58	—
22:50:02	autofocus	NGC 2030	L	5s	73	4.49	—
22:50:22	autofocus	NGC 2030	L	5s	39	5.89	—
22:50:42	autofocus	NGC 2030	L	5s	173	2.14	—
22:57:48	light	NGC 2030	H	300s	213	3.89	74%
23:03:22	light	NGC 2030	H	300s	197	4.00	68%
23:08:23	light	NGC 2030	H	300s	210	3.97	73%
23:13:51	light	NGC 2030	H	300s	224	3.90	78%
23:19:03	light	NGC 2030	O	300s	189	3.97	81%
23:24:26	light	NGC 2030	O	300s	197	4.00	84%
23:29:27	light	NGC 2030	O	300s	181	4.12	77%
23:34:46	light	NGC 2030	O	300s	179	4.14	76%
23:39:58	light	NGC 2030	S	300s	228	4.09	76%
23:45:33	light	NGC 2030	S	300s	237	3.99	79%
23:50:34	light	NGC 2030	S	300s	233	4.06	77%
23:56:10	light	NGC 2030	S	300s	230	4.17	76%
00:02:24	light	NGC 2030	H	300s	223	4.03	77%
00:07:54	light	NGC 2030	H	300s	223	4.08	77%
00:12:55	light	NGC 2030	H	300s	227	4.04	79%
00:18:24	light	NGC 2030	H	300s	225	4.03	78%
00:23:38	light	NGC 2030	O	300s	200	4.14	85%
00:29:05	light	NGC 2030	O	300s	198	4.22	85%
00:34:06	light	NGC 2030	O	300s	196	4.19	84%
00:39:32	light	NGC 2030	O	300s	185	4.37	79%
00:44:43	light	NGC 2030	S	300s	231	4.17	77%
00:50:15	autofocus	NGC 2030	S	300s	236	4.13	—
00:50:32	autofocus	NGC 2030	L	5s	232	2.17	—
00:50:47	autofocus	NGC 2030	L	5s	44	6.70	—
00:51:02	autofocus	NGC 2030	L	5s	65	4.96	—
00:51:17	autofocus	NGC 2030	L	5s	90	3.91	—
00:51:32	autofocus	NGC 2030	L	5s	155	2.81	—
00:51:52	autofocus	NGC 2030	L	5s	232	2.15	—
00:52:12	autofocus	NGC 2030	L	5s	254	2.02	—
00:52:32	autofocus	NGC 2030	L	5s	223	2.29	—
00:52:52	autofocus	NGC 2030	L	5s	161	2.94	—
00:53:07	autofocus	NGC 2030	L	5s	104	4.01	—
00:53:22	autofocus	NGC 2030	L	5s	75	4.90	—
00:53:42	autofocus	NGC 2030	L	5s	228	2.13	—
00:59:48	light	NGC 2030	S	300s	274	3.79	91%
01:05:14	light	NGC 2030	S	300s	286	3.74	95%
01:10:24	light	NGC 2030	H	300s	294	3.59	102%
01:15:58	light	NGC 2030	H	300s	299	3.54	104%
01:20:59	light	NGC 2030	H	300s	288	3.63	100%
01:26:29	light	NGC 2030	H	300s	304	3.54	106%
01:31:44	light	NGC 2030	O	300s	254	3.83	109%
01:37:15	light	NGC 2030	O	300s	276	3.69	118%
01:42:16	light	NGC 2030	O	300s	281	3.66	120%
01:47:51	light	NGC 2030	O	300s	288	3.62	123%
01:53:04	light	NGC 2030	S	300s	324	3.61	108%
01:53:57	autofocus	NGC 2030	L	5s	264	2.07	—
01:54:12	autofocus	NGC 2030	L	5s	69	5.26	—
01:54:27	autofocus	NGC 2030	L	5s	102	4.00	—
01:54:42	autofocus	NGC 2030	L	5s	159	2.93	—
01:54:57	autofocus	NGC 2030	L	5s	239	2.21	—
01:55:17	autofocus	NGC 2030	L	5s	267	2.01	—
01:55:37	autofocus	NGC 2030	L	5s	258	2.16	—
01:55:57	autofocus	NGC 2030	L	5s	193	2.78	—
01:56:12	autofocus	NGC 2030	L	5s	135	3.68	—
01:56:27	autofocus	NGC 2030	L	5s	89	4.71	—
01:56:47	autofocus	NGC 2030	L	5s	273	2.00	—
02:02:53	light	NGC 2030	S	300s	301	3.71	100%
02:07:54	light	NGC 2030	S	300s	320	3.58	106%
02:13:25	light	NGC 2030	S	300s	331	3.53	110%
02:19:38	light	NGC 2030	H	300s	319	3.49	111%
02:25:12	light	NGC 2030	H	300s	309	3.45	107%
02:30:13	light	NGC 2030	H	300s	294	3.48	102%
02:35:49	light	NGC 2030	H	300s	270	3.57	94%
02:41:04	light	NGC 2030	O	300s	232	3.67	99%
02:46:39	light	NGC 2030	O	300s	234	3.65	100%
02:51:40	light	NGC 2030	O	300s	238	3.53	102%
02:57:09	light	NGC 2030	O	300s	280	3.57	120%
03:02:19	light	NGC 2030	S	300s	320	3.59	106%
03:07:48	light	NGC 2030	S	300s	317	3.54	105%
03:12:49	light	NGC 2030	S	300s	301	3.69	100%
03:18:22	light	NGC 2030	S	300s	320	3.63	106%
03:24:33	light	NGC 2030	H	300s	275	3.71	95%
03:30:07	light	NGC 2030	H	300s	310	3.44	108%
03:35:08	light	NGC 2030	H	300s	355	3.27	123%
03:36:02	autofocus	NGC 2030	L	5s	299	1.85	—
03:36:17	autofocus	NGC 2030	L	5s	76	5.58	—
03:36:32	autofocus	NGC 2030	L	5s	112	4.02	—
03:36:47	autofocus	NGC 2030	L	5s	161	3.03	—
03:37:02	autofocus	NGC 2030	L	5s	233	2.27	—
03:37:22	autofocus	NGC 2030	L	5s	300	1.84	—
03:37:42	autofocus	NGC 2030	L	5s	278	2.07	—
03:38:02	autofocus	NGC 2030	L	5s	191	2.76	—
03:38:17	autofocus	NGC 2030	L	5s	140	3.57	—
03:38:32	autofocus	NGC 2030	L	5s	92	4.49	—
03:38:52	autofocus	NGC 2030	L	5s	252	1.88	—
03:45:02	light	NGC 2030	H	300s	307	3.28	107%
03:50:13	light	NGC 2030	O	300s	298	3.31	127%
03:55:45	light	NGC 2030	O	300s	318	3.31	136%
04:00:46	light	NGC 2030	O	300s	328	3.20	140%
04:06:24	light	NGC 2030	O	300s	336	3.22	144%
04:11:34	light	NGC 2030	S	300s	414	3.03	138%
04:17:08	light	NGC 2030	S	300s	336	3.18	112%
04:22:09	light	NGC 2030	S	300s	368	3.15	122%
04:27:25	light	NGC 2030	S	300s	249	3.34	83%
04:33:37	light	NGC 2030	H	300s	289	3.25	100%
04:39:10	light	NGC 2030	H	300s	288	3.31	100%
04:44:11	light	NGC 2030	H	300s	294	3.33	102%
04:49:40	light	NGC 2030	H	300s	23	3.29	8%
05:00:03	light	NGC 2030	O	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.