Sky transparency — night of 23–24 September 2026

Cloud arrived at 20:56 — detected by the all-sky camera, independent of N.I.N.A. Before it the sky ran at index 100 (IQR 90–106); after it 25 (IQR 3–77). 16 of 88 light frames landed before the cloud. 73 of 73 failures are attributed to cloud. Guiding ran at 0.76″ RMS before the cloud and 1.36″ after; the worst minute was 10.43″ at 04:38. The 01:59 autofocus run fitted its curve on almost no stars and should not be trusted. The 03:58 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), 05:58–06:04, auto-exposure 1.6–4.5 s.

Index before 20:56

100 · IQR 90–106

Index after 20:56

25 · IQR 3–77

Cloud onset (all-sky)

20:56 · independent

Errors after onset

73 of 73 · solve + PHD2

Guide RMS

1.25″ · RA 0.86 · Dec 0.91

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. 2000 guide frames over 8.5 h of guiding in 27 sessions; the gaps are slews, dither settles and autofocus runs, when PHD2 was not guiding. PHD2 discarded 653 further frames — usually a lost star. The worst minute (10.43″ at 04:38) 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 20:56 — **20:56** · cloud onset

All-sky at 23:03 — **23:03** · peak brightness 149.4

All-sky at 05:41 — **05:41** · end of night

Clear‑sky reference medians

The divisors behind the index — median detected stars per light sub before 20:56.

Target	Filter	Median stars	Frames	Source
NGC 602	H	119	8	tonight, clear frames
NGC 602	O	117	4	tonight, clear frames
NGC 602	S	100	4	tonight, clear frames

Event timeline

All observatory events with their attributed causes.

21:14:51PHD2timed-out waiting for guider to settlecloud

22:29:33solve failedASTAP plate solve failedcloud

22:30:13solve failedASTAP plate solve failedcloud

22:34:36PHD2timed-out waiting for guider to settlecloud

00:19:38PHD2timed-out waiting for guider to settlecloud

00:23:30PHD2timed-out waiting for guider to settlecloud

00:28:36solve failedASTAP plate solve failedcloud

00:28:56solve failedASTAP plate solve failedcloud

00:32:16PHD2timed-out waiting for guider to settlecloud

00:37:22solve failedASTAP plate solve failedcloud

00:37:42solve failedASTAP plate solve failedcloud

01:17:48solve failedASTAP plate solve failedcloud

01:18:05solve failedASTAP plate solve failedcloud

01:33:39solve failedASTAP plate solve failedcloud

01:33:59solve failedASTAP plate solve failedcloud

01:39:18solve failedASTAP plate solve failedcloud

01:39:39solve failedASTAP plate solve failedcloud

01:44:19solve failedASTAP plate solve failedcloud

01:44:34solve failedASTAP plate solve failedcloud

01:49:32AF failedautofocus run started 01:46:00 did not completecloud

02:25:37solve failedASTAP plate solve failedcloud

02:26:04solve failedASTAP plate solve failedcloud

02:30:40solve failedASTAP plate solve failedcloud

02:31:07solve failedASTAP plate solve failedcloud

02:36:54solve failedASTAP plate solve failedcloud

02:37:21solve failedASTAP plate solve failedcloud

02:43:45solve failedASTAP plate solve failedcloud

02:44:05solve failedASTAP plate solve failedcloud

02:46:39PHD2timed-out waiting for guider to settlecloud

02:51:45solve failedASTAP plate solve failedcloud

02:52:09solve failedASTAP plate solve failedcloud

02:56:47solve failedASTAP plate solve failedcloud

02:57:09solve failedASTAP plate solve failedcloud

03:01:51PHD2timed-out waiting for guider to settlecloud

03:06:57solve failedASTAP plate solve failedcloud

03:07:25solve failedASTAP plate solve failedcloud

03:09:47PHD2timed-out waiting for guider to settlecloud

03:18:51solve failedASTAP plate solve failedcloud

03:19:24solve failedASTAP plate solve failedcloud

03:25:35solve failedASTAP plate solve failedcloud

03:26:01solve failedASTAP plate solve failedcloud

03:28:21PHD2timed-out waiting for guider to settlecloud

03:33:27solve failedASTAP plate solve failedcloud

03:33:49solve failedASTAP plate solve failedcloud

03:35:31PHD2timed-out waiting for guider to settlecloud

03:38:27PHD2timed-out waiting for guider to settlecloud

03:43:33solve failedASTAP plate solve failedcloud

03:44:00solve failedASTAP plate solve failedcloud

03:48:34solve failedASTAP plate solve failedcloud

03:48:56solve failedASTAP plate solve failedcloud

03:52:17AF failedautofocus run started 03:48:42 did not completecloud

03:56:08PHD2timed-out waiting for guider to settlecloud

03:58:44solve failedASTAP plate solve failedcloud

03:59:17solve failedASTAP plate solve failedcloud

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

04:10:02solve failedASTAP plate solve failedcloud

04:10:29solve failedASTAP plate solve failedcloud

04:19:01solve failedASTAP plate solve failedcloud

04:19:18solve failedASTAP plate solve failedcloud

04:24:04solve failedASTAP plate solve failedcloud

04:24:25solve failedASTAP plate solve failedcloud

04:26:59PHD2timed-out waiting for guider to settlecloud

04:32:04solve failedASTAP plate solve failedcloud

04:32:20solve failedASTAP plate solve failedcloud

04:37:08solve failedASTAP plate solve failedcloud

04:37:27solve failedASTAP plate solve failedcloud

04:39:44PHD2timed-out waiting for guider to settlecloud

04:44:50solve failedASTAP plate solve failedcloud

04:45:11solve failedASTAP plate solve failedcloud

04:49:51solve failedASTAP plate solve failedcloud

04:50:11solve failedASTAP plate solve failedcloud

04:52:07PHD2timed-out waiting for guider to settlecloud

04:57:13solve failedASTAP plate solve failedcloud

04:57:34solve failedASTAP plate solve failedcloud

05:00:08PHD2timed-out waiting for guider to settlecloud

All 191 frames (excludes the 60 sky flats — no stars to detect)

Time	Class	Target	Filter	Exp	Stars	HFR	Index
19:15:55	autofocus	NGC 602	L	5s	40	3.79	—
19:16:13	autofocus	NGC 602	L	5s	42	2.97	—
19:16:29	autofocus	NGC 602	L	5s	87	1.87	—
19:16:48	autofocus	NGC 602	L	5s	90	1.97	—
19:17:03	autofocus	NGC 602	L	5s	73	2.60	—
19:17:23	autofocus	NGC 602	L	5s	53	3.38	—
19:17:43	autofocus	NGC 602	L	5s	36	4.32	—
19:18:03	autofocus	NGC 602	L	5s	24	5.73	—
19:18:23	autofocus	NGC 602	L	5s	40	3.81	—
19:18:38	autofocus	NGC 602	L	5s	30	4.73	—
19:18:58	autofocus	NGC 602	L	5s	18	6.34	—
19:19:18	autofocus	NGC 602	L	5s	93	1.95	—
19:26:11	light	NGC 602	H	300s	140	3.61	118%
19:31:12	light	NGC 602	H	300s	112	4.04	94%
19:36:51	light	NGC 602	H	300s	117	3.94	98%
19:41:53	light	NGC 602	H	300s	134	3.79	113%
19:47:41	light	NGC 602	O	300s	117	3.75	100%
19:52:43	light	NGC 602	O	300s	101	3.82	86%
19:58:01	light	NGC 602	O	300s	116	3.72	99%
20:03:02	light	NGC 602	O	300s	125	3.66	107%
20:04:08	autofocus	NGC 602	L	5s	86	1.95	—
20:04:28	autofocus	NGC 602	L	5s	21	6.56	—
20:04:43	autofocus	NGC 602	L	5s	33	4.95	—
20:04:58	autofocus	NGC 602	L	5s	45	3.71	—
20:05:13	autofocus	NGC 602	L	5s	57	2.74	—
20:05:33	autofocus	NGC 602	L	5s	82	2.00	—
20:05:53	autofocus	NGC 602	L	5s	79	1.87	—
20:06:13	autofocus	NGC 602	L	5s	79	2.12	—
20:06:33	autofocus	NGC 602	L	5s	61	3.00	—
20:06:53	autofocus	NGC 602	L	5s	41	4.02	—
20:07:08	autofocus	NGC 602	L	5s	25	5.26	—
20:07:28	autofocus	NGC 602	L	5s	73	1.91	—
20:13:37	light	NGC 602	S	300s	119	3.23	119%
20:18:38	light	NGC 602	S	300s	92	3.41	92%
20:24:12	light	NGC 602	S	300s	82	3.29	82%
20:29:14	light	NGC 602	S	300s	100	3.26	100%
20:35:00	light	NGC 602	H	300s	107	3.59	90%
20:40:02	light	NGC 602	H	300s	119	3.65	100%
20:45:38	light	NGC 602	H	300s	125	3.59	105%
20:50:40	light	NGC 602	H	300s	89	3.89	75%
20:51:34	autofocus	NGC 602	L	5s	53	2.09	—
20:51:54	autofocus	NGC 602	L	5s	16	6.91	—
20:52:14	autofocus	NGC 602	L	5s	17	5.14	—
20:52:34	autofocus	NGC 602	L	5s	22	4.09	—
20:52:54	autofocus	NGC 602	L	5s	46	2.75	—
20:53:14	autofocus	NGC 602	L	5s	59	2.05	—
20:53:34	autofocus	NGC 602	L	5s	71	1.86	—
20:53:54	autofocus	NGC 602	L	5s	56	2.34	—
20:54:14	autofocus	NGC 602	L	5s	41	2.99	—
20:54:34	autofocus	NGC 602	L	5s	26	4.10	—
20:54:54	autofocus	NGC 602	L	5s	21	5.26	—
20:55:14	autofocus	NGC 602	L	5s	66	1.88	—
21:01:27	light	NGC 602	O	300s	76	3.26	65%
21:06:29	light	NGC 602	O	300s	33	3.68	28%
21:12:11	light	NGC 602	O	300s	19	3.82	16%
21:19:56	light	NGC 602	O	300s	24	3.70	21%
21:25:50	light	NGC 602	S	300s	24	3.73	24%
21:30:55	light	NGC 602	S	300s	26	3.77	26%
21:36:29	light	NGC 602	S	300s	66	3.51	66%
21:41:31	light	NGC 602	S	300s	51	3.61	51%
21:47:49	light	NGC 602	H	300s	117	3.52	98%
21:52:52	light	NGC 602	H	300s	167	3.70	140%
21:58:19	light	NGC 602	H	300s	174	3.63	146%
22:03:23	light	NGC 602	H	300s	192	3.51	161%
22:04:14	autofocus	NGC 602	L	5s	148	1.96	—
22:04:34	autofocus	NGC 602	L	5s	38	6.22	—
22:04:54	autofocus	NGC 602	L	5s	51	4.50	—
22:05:14	autofocus	NGC 602	L	5s	81	3.34	—
22:05:34	autofocus	NGC 602	L	5s	116	2.48	—
22:05:54	autofocus	NGC 602	L	5s	157	1.90	—
22:06:14	autofocus	NGC 602	L	5s	156	1.85	—
22:06:34	autofocus	NGC 602	L	5s	121	2.51	—
22:06:54	autofocus	NGC 602	L	5s	93	3.23	—
22:07:14	autofocus	NGC 602	L	5s	67	4.29	—
22:07:34	autofocus	NGC 602	L	5s	51	5.19	—
22:07:54	autofocus	NGC 602	L	5s	159	1.88	—
22:14:06	light	NGC 602	O	300s	190	3.41	162%
22:19:07	light	NGC 602	O	300s	180	3.50	154%
22:24:25	light	NGC 602	O	300s	133	3.44	114%
22:29:31	light	NGC 602	O	300s	16	3.67	14%
22:39:41	light	NGC 602	S	300s	54	3.68	54%
22:44:42	light	NGC 602	S	300s	106	3.71	106%
22:50:15	light	NGC 602	S	300s	91	3.72	91%
22:55:17	light	NGC 602	S	300s	18	4.01	18%
23:01:42	light	NGC 602	H	300s	47	3.81	39%
23:06:43	light	NGC 602	H	300s	49	3.79	41%
23:12:14	light	NGC 602	H	300s	116	3.82	97%
23:17:15	light	NGC 602	H	300s	74	3.93	62%
23:23:34	light	NGC 602	O	300s	138	4.06	118%
23:28:36	light	NGC 602	O	300s	92	3.90	79%
23:29:24	autofocus	NGC 602	L	5s	116	2.14	—
23:29:44	autofocus	NGC 602	L	5s	28	6.73	—
23:30:04	autofocus	NGC 602	L	5s	46	4.97	—
23:30:24	autofocus	NGC 602	L	5s	49	3.78	—
23:30:44	autofocus	NGC 602	L	5s	72	2.64	—
23:31:04	autofocus	NGC 602	L	5s	137	2.00	—
23:31:24	autofocus	NGC 602	L	5s	164	1.89	—
23:31:44	autofocus	NGC 602	L	5s	123	2.31	—
23:32:04	autofocus	NGC 602	L	5s	100	3.03	—
23:32:24	autofocus	NGC 602	L	5s	61	4.02	—
23:32:44	autofocus	NGC 602	L	5s	43	5.20	—
23:33:04	autofocus	NGC 602	L	5s	80	1.88	—
23:39:17	light	NGC 602	O	300s	161	3.56	138%
23:44:20	light	NGC 602	O	300s	155	3.64	132%
23:50:04	light	NGC 602	S	300s	196	3.47	196%
23:55:06	light	NGC 602	S	300s	144	3.35	144%
00:00:49	light	NGC 602	S	300s	100	3.39	100%
00:05:51	light	NGC 602	S	300s	174	3.36	174%
00:11:56	light	NGC 602	H	300s	87	3.40	73%
00:17:39	light	NGC 602	H	300s	4	3.51	3%
00:28:35	light	NGC 602	H	300s	0	0.00	0%
00:37:21	light	NGC 602	H	300s	0	0.00	0%
00:44:28	light	NGC 602	O	300s	41	3.30	35%
00:49:30	light	NGC 602	O	300s	68	3.38	58%
00:55:05	light	NGC 602	O	300s	62	3.12	53%
01:00:06	light	NGC 602	O	300s	42	3.28	36%
01:06:18	light	NGC 602	S	300s	74	3.21	74%
01:11:21	light	NGC 602	S	300s	52	3.17	52%
01:17:47	light	NGC 602	S	300s	14	3.29	14%
01:22:49	light	NGC 602	S	300s	21	3.19	21%
01:28:36	light	NGC 602	H	300s	28	3.13	24%
01:33:38	light	NGC 602	H	300s	23	3.49	19%
01:39:17	light	NGC 602	H	300s	11	3.50	9%
01:44:19	light	NGC 602	H	300s	4	3.72	3%
01:46:19	centering	NGC 602	L	5s	0	0.00	—
01:46:39	centering	NGC 602	L	5s	0	0.00	—
01:46:59	centering	NGC 602	L	5s	0	0.00	—
01:47:19	centering	NGC 602	L	5s	0	0.00	—
01:47:39	centering	NGC 602	L	5s	1	0.00	—
01:48:09	centering	NGC 602	L	5s	1	0.00	—
01:48:29	centering	NGC 602	L	5s	0	0.00	—
01:48:49	centering	NGC 602	L	5s	0	0.00	—
01:49:09	centering	NGC 602	L	5s	0	0.00	—
01:59:07	autofocus	NGC 602	O	300s	77	4.01	—
01:59:30	autofocus	NGC 602	L	5s	25	2.50	—
01:59:49	autofocus	NGC 602	L	5s	18	3.37	—
02:00:09	autofocus	NGC 602	L	5s	22	2.27	—
02:00:29	autofocus	NGC 602	L	5s	24	1.85	—
02:00:49	autofocus	NGC 602	L	5s	26	1.73	—
02:01:10	autofocus	NGC 602	L	5s	13	2.57	—
02:01:29	autofocus	NGC 602	L	5s	9	3.56	—
02:01:49	autofocus	NGC 602	L	5s	6	4.61	—
02:02:09	autofocus	NGC 602	L	5s	3	5.35	—
02:02:29	autofocus	NGC 602	L	5s	9	4.37	—
02:02:49	autofocus	NGC 602	L	5s	21	1.84	—
02:09:04	light	NGC 602	O	300s	27	3.08	23%
02:14:35	light	NGC 602	O	300s	20	3.30	17%
02:19:37	light	NGC 602	O	300s	15	3.09	13%
02:25:36	light	NGC 602	S	300s	28	3.13	28%
02:30:38	light	NGC 602	S	300s	43	3.22	43%
02:36:53	light	NGC 602	S	300s	20	3.48	20%
02:43:44	light	NGC 602	S	300s	2	4.50	2%
02:51:44	light	NGC 602	H	300s	3	3.99	3%
02:56:46	light	NGC 602	H	300s	0	0.00	0%
03:06:55	light	NGC 602	H	300s	0	0.00	0%
03:18:49	light	NGC 602	H	300s	0	0.00	0%
03:25:33	light	NGC 602	O	300s	0	0.00	0%
03:33:26	light	NGC 602	O	300s	0	0.00	0%
03:43:31	light	NGC 602	O	300s	0	0.00	0%
03:48:33	light	NGC 602	O	300s	0	0.00	0%
03:49:05	centering	NGC 602	L	5s	0	0.00	—
03:49:25	centering	NGC 602	L	5s	0	0.00	—
03:49:45	centering	NGC 602	L	5s	0	0.00	—
03:50:05	centering	NGC 602	L	5s	0	0.00	—
03:50:24	centering	NGC 602	L	5s	0	0.00	—
03:50:55	centering	NGC 602	L	5s	0	0.00	—
03:51:14	centering	NGC 602	L	5s	0	0.00	—
03:51:34	centering	NGC 602	L	5s	0	0.00	—
03:51:54	centering	NGC 602	L	5s	0	0.00	—
03:58:42	autofocus	NGC 602	S	300s	7	5.45	—
03:59:00	autofocus	NGC 602	L	5s	5	3.12	—
03:59:20	autofocus	NGC 602	L	5s	3	6.01	—
03:59:40	autofocus	NGC 602	L	5s	4	4.81	—
04:00:00	autofocus	NGC 602	L	5s	4	3.92	—
04:00:19	autofocus	NGC 602	L	5s	6	3.42	—
04:00:40	autofocus	NGC 602	L	5s	7	3.09	—
04:00:59	autofocus	NGC 602	L	5s	9	2.74	—
04:01:19	autofocus	NGC 602	L	5s	9	2.59	—
04:01:39	autofocus	NGC 602	L	5s	8	3.37	—
04:02:00	autofocus	NGC 602	L	5s	7	4.25	—
04:02:19	autofocus	NGC 602	L	5s	5	5.05	—
04:02:40	autofocus	NGC 602	L	5s	7	2.65	—
04:10:01	light	NGC 602	S	300s	15	4.42	15%
04:19:00	light	NGC 602	S	300s	3	4.28	3%
04:24:03	light	NGC 602	S	300s	0	0.00	0%
04:32:03	light	NGC 602	H	300s	0	0.00	0%
04:37:06	light	NGC 602	H	300s	0	0.00	0%
04:44:49	light	NGC 602	H	300s	0	0.00	0%
04:49:51	light	NGC 602	H	300s	0	0.00	0%
04:57:12	light	NGC 602	O	300s	0	0.00	0%
05:05:12	light	NGC 602	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.