Note: numbers for 25B will change slightly when the last megacam run of 25B is included, and we will expand the details on selection of images (last updated Feb 26,2026)

We have compiled statistics on the image quality of megacam from 2016A until 2025B (25Bm05 not included yet). There are a few cuts of the data:

• exposures with invalid/missing metadata - these are excluded
• exposures with non-sidereal tracking - these are excluded
• exposures with invalid filter names or iq ranges (ie; improperly set) - these are excluded

The histograms and statistics provided are heavily affected by the following factors:

• There is a ~0.25 arcsec difference between the IQ measured in u and that measured in r. If we measure 1" with the r filter, u observations will have an IQ of 1.25 arcsec.
• There is a ~0.1 arcsec difference between the IQ measured in g and that measured in r.
• Some filters have fewer exposures than others, resulting in statistics with less precision. The number of exposures is provided in the tables below.
• The exposures were taken under sky conditions that met each program's constraints. If the IQ is "high" in one filter, especially if there are few exposures, this could simply reflect the fact that the program(s) could be carried under "high" IQ and were observed when the IQ was higher than the typical IQ.

Statistics are generated for each semester "year" (aka, 24A+24B), in chunks of 3 years (23A-25B), and in chunks of 5 years (21A-25B), for most of the filters (u g r i z gri Ha CaHK). A few filters are used infrequently and are excluded (HaOFF, CaHKOFF, OIIIOFF). Histograms are generated as well, with bin sizes of .05 in IQ. You can select which histogram to view by changing the date range and/or the filters. A subset of the statistics are listed to the right of the histogram, and are copies of the statistics listened in the large table below.

Select Time Range: 5 years: 21A-25B 5 years: 16A-20B 3 years: 23A-25B 3 years: 20A-22B 3 years: 17A-19B 25A+25B 24A+24B 23A+23B 22A+22B 21A+21B 20A+20B 19A+19B 18A+18B 17A+17B

Select Filter: all filters u band g band r band i band z band gri band Ha band CaHK band

Time Range	u band			g band			r band			i band			z band			gri band			Ha band			CaHK band
	mean	median	# exp	mean	median	# exp	mean	median	# exp	mean	median	# exp	mean	median	# exp	mean	median	# exp	mean	median	# exp	mean	median	# exp
16A+16B	0.88	0.85	6232	0.91	0.81	1946	0.77	0.70	1562	0.79	0.70	1203	0.69	0.63	244	0.74	0.70	1320	0.59	0.56	200	1.04	0.88	1274
17A+17B	0.94	0.86	5710	1.01	0.87	1292	0.72	0.66	6199	0.74	0.68	1146	0.71	0.66	17	0.81	0.78	691	0.76	0.70	518	1.19	1.12	2506
18A+18B	0.94	0.91	4994	0.89	0.82	483	0.75	0.71	3985	0.91	0.82	1658	0.55	0.56	13	0.91	0.82	181	0.73	0.68	201	1.19	1.12	2136
19A+19B	0.91	0.89	2887	0.89	0.81	269	0.77	0.72	1971	0.78	0.74	1036	0.59	0.54	123	0.90	0.86	709	0.89	0.82	178	1.06	0.97	2609
20A+20B	0.95	0.87	2059	1.03	0.89	305	0.75	0.70	3263	0.83	0.73	943	1.00	1.04	59	0.81	0.73	804	0.80	0.73	234	1.32	1.22	1180
21A+21B	1.05	1.01	4820	1.13	1.03	609	0.80	0.76	3570	0.86	0.78	900	0.83	0.81	99	0.76	0.73	562	0.77	0.70	529	1.25	1.17	895
22A+22B	1.07	1.06	2873	1.19	1.18	634	0.75	0.73	4863	0.81	0.74	2314	0.80	0.76	278	0.75	0.70	1055	0.79	0.70	248	1.00	0.89	816
23A+23B	1.15	1.06	955	1.02	1.00	342	0.81	0.75	2567	0.77	0.70	339	0.74	0.70	25	0.81	0.79	1878	1.10	1.04	227	1.09	0.99	362
24A+24B	1.07	1.01	2472	1.02	0.94	375	0.85	0.78	1145	0.97	0.85	172	0.91	0.81	70	0.88	0.83	2381	0.99	0.90	102	1.11	1.00	2039
25A+25B	1.03	1.00	6059	0.89	0.85	1054	0.71	0.67	2396	0.86	0.74	377	0.75	0.68	185	0.76	0.73	738	0.73	0.69	426	0.98	0.90	3013
17A-19B	0.93	0.89	13591	0.96	0.85	2044	0.74	0.69	12155	0.82	0.76	3840	0.60	0.55	153	0.86	0.83	1581	0.78	0.71	897	1.15	1.05	7251
20A-22B	1.03	1.00	9752	1.13	1.07	1548	0.77	0.73	11696	0.83	0.75	4157	0.83	0.79	436	0.77	0.72	2421	0.78	0.70	1011	1.21	1.13	2891
23A-25B	1.06	1.01	9486	0.94	0.89	1771	0.78	0.72	6108	0.85	0.73	888	0.79	0.70	280	0.83	0.80	4997	0.88	0.80	755	1.04	0.94	5414
16A-20B	0.92	0.88	21882	0.95	0.84	4295	0.74	0.69	16980	0.82	0.74	5986	0.70	0.61	456	0.81	0.77	3705	0.76	0.68	1331	1.15	1.05	9705
21A-25B	1.06	1.02	17179	1.03	0.95	3014	0.78	0.73	14541	0.83	0.74	4102	0.80	0.75	657	0.81	0.78	6614	0.83	0.75	1532	1.06	0.95	7125