Queen City Astronomy Club
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Queen City Astronomy Club clear sky chart from 2005-11-06 to 2026-07-31.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	11% 6% 3 6% 5% 5% 5% 4 6% 8% 42%	138301
	Night	12% 7% 2 6% 4 4 4 4 5% 7% 44%	134516
Transparency	Day	39% 6% 11% 20% 19% 6%	142071
	Night	38% 5% 10% 19% 20% 8%	138810
Seeing	Day	15% 9% 22% 25% 20% 9%	17112
	Night	15% 8% 23% 30% 21% 4	26503

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 10% 5% 7% 3 3 3 3 4 4 42%	5264
	11th to 20th	Day	9% 5% 3 5% 3 3 3 3 5% 7% 54%	5802
	21st to end	Day	23% 11% 3 6% 4 3 3 2 3 4 37%	6436
February	1st to 10th	Day	16% 9% 3 6% 4 4 4 3 4 6% 40%	2100
	11th to 20th	Day	19% 9% 3 5% 4 4 3 3 4 5% 40%	2048
	21st to end	Day	15% 8% 3 8% 4 4 4 3 5% 5% 41%	1730
March	1st to 10th	Day	18% 9% 3 8% 5% 5% 5% 3 5% 6% 34%	4580
	11th to 20th	Day	11% 6% 2 5% 4 5% 4 3 6% 7% 45%	4869
	21st to end	Day	15% 8% 3 7% 5% 4 4 3 5% 5% 41%	6094
April	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 6% 6% 45%	2520
	11th to 20th	Day	13% 6% 2 6% 5% 3 4 3 5% 7% 47%	2494
	21st to end	Day	8% 5% 2 5% 5% 4 5% 4 6% 8% 48%	2520
May	1st to 10th	Day	16% 8% 3 7% 5% 4 4 4 6% 7% 37%	7021
	11th to 20th	Day	9% 6% 2 7% 5% 6% 5% 5% 7% 9% 39%	7443
	21st to end	Day	11% 7% 3 8% 6% 5% 6% 5% 7% 9% 33%	8391
June	1st to 10th	Day	10% 6% 2 6% 5% 6% 6% 5% 6% 10% 38%	2730
	11th to 20th	Day	6% 4 3 6% 6% 5% 7% 5% 9% 10% 40%	2834
	21st to end	Day	6% 5% 2 6% 6% 7% 6% 6% 8% 11% 38%	2940
July	1st to 10th	Day	4 5% 2 8% 7% 6% 7% 7% 9% 12% 33%	6500
	11th to 20th	Day	6% 4 2 5% 6% 6% 6% 6% 10% 12% 36%	5857
	21st to end	Day	6% 6% 3 9% 7% 7% 7% 6% 9% 11% 29%	6042
August	1st to 10th	Day	3 3 1 4 3 3 4 4 7% 9% 58%	3905
	11th to 20th	Day	5% 3 2 6% 5% 5% 6% 5% 6% 10% 47%	3849
	21st to end	Day	7% 3 2 6% 5% 5% 5% 4 7% 9% 45%	4312
September	1st to 10th	Day	10% 5% 2 8% 6% 5% 5% 5% 6% 7% 41%	2400
	11th to 20th	Day	13% 7% 2 6% 5% 5% 4 4 5% 7% 43%	2255
	21st to end	Day	11% 5% 2 5% 4 4 3 4 4 8% 51%	2200
October	1st to 10th	Day	8% 5% 2 6% 3 4 3 3 4 6% 57%	2200
	11th to 20th	Day	9% 4 2 5% 3 3 3 3 4 7% 58%	2055
	21st to end	Day	12% 5% 2 4 4 3 3 2 4 6% 56%	2200
November	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 4 5% 55%	1882
	11th to 20th	Day	11% 6% 2 5% 3 4 3 3 4 5% 54%	1890
	21st to end	Day	15% 6% 2 6% 4 4 3 3 4 5% 48%	1890
December	1st to 10th	Day	15% 9% 3 6% 4 3 3 2 5% 6% 44%	3020
	11th to 20th	Day	12% 9% 3 8% 5% 4 4 3 4 5% 44%	3463
	21st to end	Day	16% 8% 2 5% 3 3 3 3 4 5% 46%	4565
January	1st to 10th	Night	18% 11% 3 6% 3 3 3 2 3 4 42%	7493
	11th to 20th	Night	15% 7% 3 5% 3 3 3 2 4 5% 49%	7080
	21st to end	Night	22% 10% 3 7% 4 3 3 2 3 4 39%	7745
February	1st to 10th	Night	15% 7% 3 5% 4 3 4 3 5% 6% 44%	2520
	11th to 20th	Night	20% 9% 2 5% 4 3 3 2 4 4 43%	2458
	21st to end	Night	17% 8% 2 7% 4 4 5% 3 5% 5% 41%	2076
March	1st to 10th	Night	20% 10% 3 6% 3 4 4 3 5% 6% 37%	5493
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 49%	5340
	21st to end	Night	16% 6% 2 6% 4 4 4 3 5% 6% 44%	5076
April	1st to 10th	Night	11% 6% 2 6% 5% 4 5% 4 6% 6% 47%	2100
	11th to 20th	Night	11% 6% 2 4 3 3 4 4 5% 7% 50%	2075
	21st to end	Night	8% 5% 2 4 3 4 4 3 6% 10% 51%	2100
May	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 5% 8% 38%	5832
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 5% 6% 9% 37%	5414
	21st to end	Night	10% 8% 3 9% 6% 6% 6% 5% 8% 9% 32%	5761
June	1st to 10th	Night	6% 5% 2 6% 5% 4 6% 8% 8% 10% 40%	1890
	11th to 20th	Night	4 5% 2 6% 4 4 5% 5% 9% 10% 46%	1776
	21st to end	Night	5% 4 2 5% 4 6% 5% 4 9% 13% 43%	1680
July	1st to 10th	Night	5% 4 2 7% 7% 6% 6% 6% 9% 12% 37%	3698
	11th to 20th	Night	5% 4 2 7% 5% 6% 6% 6% 10% 15% 35%	4286
	21st to end	Night	5% 6% 3 8% 7% 6% 7% 7% 9% 13% 28%	5029
August	1st to 10th	Night	2 2 1 4 3 3 4 4 7% 11% 57%	3244
	11th to 20th	Night	4 2 1 5% 4 5% 6% 5% 7% 12% 50%	3200
	21st to end	Night	6% 4 2 6% 4 6% 6% 5% 7% 10% 45%	3586
September	1st to 10th	Night	9% 6% 1 7% 5% 5% 5% 5% 6% 8% 43%	2000
	11th to 20th	Night	10% 7% 2 5% 5% 4 4 3 5% 8% 47%	2125
	21st to end	Night	7% 5% 2 6% 4 3 4 4 6% 7% 52%	2200
October	1st to 10th	Night	8% 4 1 5% 3 3 4 3 5% 6% 58%	2200
	11th to 20th	Night	9% 5% 1 4 3 3 4 3 4 6% 59%	2340
	21st to end	Night	13% 6% 2 5% 3 3 2 2 3 4 57%	2640
November	1st to 10th	Night	10% 4 2 5% 3 3 3 3 3 6% 58%	2634
	11th to 20th	Night	13% 5% 2 4 3 3 3 2 4 6% 55%	2730
	21st to end	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2730
December	1st to 10th	Night	17% 7% 2 6% 3 3 3 3 5% 5% 46%	4380
	11th to 20th	Night	14% 9% 3 7% 4 4 3 2 3 5% 45%	4952
	21st to end	Night	17% 8% 3 6% 3 3 2 3 4 6% 46%	6633

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	47% 3 6% 25% 17% 3	5265
	11th to 20th	Day	31% 2 6% 21% 31% 8%	5802
	21st to end	Day	53% 2 5% 12% 17% 12%	6436
February	1st to 10th	Day	46% 4 7% 16% 20% 8%	2100
	11th to 20th	Day	47% 3 5% 18% 20% 7%	2058
	21st to end	Day	45% 5% 7% 16% 17% 11%	1730
March	1st to 10th	Day	50% 4 7% 13% 20% 6%	4580
	11th to 20th	Day	37% 4 7% 16% 19% 17%	4869
	21st to end	Day	45% 4 8% 16% 20% 7%	6096
April	1st to 10th	Day	38% 5% 9% 20% 20% 7%	2520
	11th to 20th	Day	38% 4 7% 20% 25% 7%	2494
	21st to end	Day	33% 7% 10% 23% 23% 4	2520
May	1st to 10th	Day	46% 5% 10% 20% 15% 3	7056
	11th to 20th	Day	39% 7% 16% 20% 15% 2	7447
	21st to end	Day	44% 9% 13% 20% 13% 1	8405
June	1st to 10th	Day	40% 7% 14% 23% 14% 2	2730
	11th to 20th	Day	36% 8% 19% 21% 14% 2	2834
	21st to end	Day	36% 9% 16% 24% 12% 3	2940
July	1st to 10th	Day	38% 11% 19% 22% 8% 1	6431
	11th to 20th	Day	34% 12% 29% 22% 3 1	5786
	21st to end	Day	43% 12% 18% 23% 4	5872
August	1st to 10th	Day	21% 6% 13% 31% 27% 1	3893
	11th to 20th	Day	31% 8% 17% 29% 14% 2	3885
	21st to end	Day	33% 9% 15% 22% 19% 3	4311
September	1st to 10th	Day	41% 7% 13% 18% 16% 6%	2400
	11th to 20th	Day	39% 6% 10% 18% 21% 5%	2255
	21st to end	Day	32% 4 9% 25% 21% 8%	2200
October	1st to 10th	Day	23% 3 5% 14% 30% 25%	3590
	11th to 20th	Day	18% 2 4 15% 31% 30%	3321
	21st to end	Day	23% 2 4 17% 38% 17%	3538
November	1st to 10th	Day	33% 3 7% 18% 27% 12%	1882
	11th to 20th	Day	33% 3 7% 16% 27% 13%	1890
	21st to end	Day	38% 4 7% 18% 24% 9%	1890
December	1st to 10th	Day	42% 3 6% 18% 27% 4	3020
	11th to 20th	Day	43% 3 8% 18% 21% 7%	3460
	21st to end	Day	41% 3 6% 23% 26% 2	4565
January	1st to 10th	Night	47% 2 6% 19% 22% 3	7494
	11th to 20th	Night	40% 2 5% 16% 28% 10%	7080
	21st to end	Night	52% 2 3 15% 20% 9%	7745
February	1st to 10th	Night	42% 3 7% 17% 22% 9%	2520
	11th to 20th	Night	47% 3 6% 16% 19% 10%	2459
	21st to end	Night	45% 5% 6% 16% 16% 12%	2076
March	1st to 10th	Night	48% 3 7% 14% 18% 10%	5493
	11th to 20th	Night	36% 4 8% 16% 20% 16%	5340
	21st to end	Night	41% 4 8% 20% 18% 8%	5076
April	1st to 10th	Night	37% 5% 11% 18% 19% 10%	2100
	11th to 20th	Night	33% 4 9% 20% 24% 11%	2075
	21st to end	Night	29% 5% 11% 25% 24% 6%	2100
May	1st to 10th	Night	44% 6% 13% 18% 16% 4	5862
	11th to 20th	Night	43% 6% 14% 21% 15% 1	5415
	21st to end	Night	45% 9% 13% 18% 13% 2	5771
June	1st to 10th	Night	34% 11% 14% 23% 16% 2	1890
	11th to 20th	Night	28% 10% 18% 26% 14% 4	1776
	21st to end	Night	30% 10% 20% 22% 15% 3	1680
July	1st to 10th	Night	35% 12% 23% 21% 7% 1	3660
	11th to 20th	Night	33% 14% 32% 18% 3	4237
	21st to end	Night	43% 13% 19% 21% 4 1	4885
August	1st to 10th	Night	19% 7% 17% 32% 24% 1	3232
	11th to 20th	Night	25% 9% 20% 29% 14% 2	3230
	21st to end	Night	34% 9% 14% 20% 18% 5%	3586
September	1st to 10th	Night	37% 8% 14% 18% 17% 6%	2000
	11th to 20th	Night	35% 6% 14% 18% 20% 7%	2125
	21st to end	Night	30% 5% 10% 24% 23% 9%	2200
October	1st to 10th	Night	22% 3 7% 12% 26% 29%	3590
	11th to 20th	Night	18% 2 3 16% 27% 34%	3800
	21st to end	Night	22% 2 5% 15% 36% 20%	4252
November	1st to 10th	Night	29% 4 8% 17% 28% 15%	2634
	11th to 20th	Night	31% 3 7% 17% 29% 13%	2730
	21st to end	Night	35% 4 7% 22% 19% 12%	2730
December	1st to 10th	Night	40% 3 7% 19% 25% 6%	4380
	11th to 20th	Night	44% 3 6% 17% 25% 5%	4954
	21st to end	Night	41% 3 6% 19% 29% 2	6633

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	27% 23% 33% 13% 3 1	330
	11th to 20th	Day	22% 22% 34% 15% 5% 1	330
	21st to end	Day	28% 23% 34% 12% 3 1	363
February	1st to 10th	Day	23% 18% 40% 13% 5%	330
	11th to 20th	Day	33% 21% 34% 9% 3	330
	21st to end	Day	26% 23% 38% 11% 1	273
March	1st to 10th	Day	24% 20% 37% 14% 5% 1	330
	11th to 20th	Day	25% 21% 34% 16% 3	330
	21st to end	Day	22% 14% 34% 24% 6%	589
April	1st to 10th	Day	18% 15% 34% 21% 10% 1	540
	11th to 20th	Day	22% 12% 30% 24% 10% 2	532
	21st to end	Day	12% 12% 29% 31% 15% 2	540
May	1st to 10th	Day	17% 10% 27% 27% 16% 3	543
	11th to 20th	Day	10% 6% 25% 32% 17% 10%	567
	21st to end	Day	10% 4 22% 33% 20% 11%	617
June	1st to 10th	Day	13% 3 14% 33% 27% 10%	570
	11th to 20th	Day	8% 3 15% 30% 31% 13%	674
	21st to end	Day	7% 2 13% 29% 32% 16%	780
July	1st to 10th	Day	6% 1 7% 32% 38% 16%	771
	11th to 20th	Day	9% 2 4 23% 39% 23%	648
	21st to end	Day	7% 1 7% 28% 38% 19%	616
August	1st to 10th	Day	6% 2 8% 26% 34% 25%	526
	11th to 20th	Day	6% 1 5% 26% 36% 25%	519
	21st to end	Day	15% 2 8% 25% 31% 19%	583
September	1st to 10th	Day	9% 3 11% 34% 28% 15%	530
	11th to 20th	Day	13% 2 12% 23% 35% 15%	530
	21st to end	Day	13% 3 15% 29% 28% 11%	530
October	1st to 10th	Day	9% 5% 24% 31% 23% 8%	530
	11th to 20th	Day	9% 7% 27% 35% 19% 3	385
	21st to end	Day	19% 9% 26% 29% 13% 4	363
November	1st to 10th	Day	20% 11% 30% 25% 10% 4	330
	11th to 20th	Day	16% 10% 38% 25% 10%	330
	21st to end	Day	15% 16% 38% 18% 11% 2	330
December	1st to 10th	Day	25% 16% 36% 17% 6%	330
	11th to 20th	Day	20% 13% 39% 20% 6% 1	330
	21st to end	Day	27% 13% 32% 21% 7%	363
January	1st to 10th	Night	23% 14% 36% 22% 6%	920
	11th to 20th	Night	22% 14% 31% 26% 6%	840
	21st to end	Night	23% 14% 35% 25% 3	924
February	1st to 10th	Night	22% 12% 32% 29% 5%	840
	11th to 20th	Night	27% 16% 30% 23% 4	823
	21st to end	Night	22% 17% 37% 21% 2	692
March	1st to 10th	Night	19% 14% 31% 28% 7%	840
	11th to 20th	Night	17% 12% 37% 27% 6% 1	750
	21st to end	Night	15% 13% 34% 27% 11%	693
April	1st to 10th	Night	16% 12% 34% 27% 11%	630
	11th to 20th	Night	13% 10% 34% 29% 12% 1	623
	21st to end	Night	9% 8% 31% 35% 16% 1	630
May	1st to 10th	Night	12% 4 29% 35% 18% 2	630
	11th to 20th	Night	12% 3 23% 38% 22% 2	621
	21st to end	Night	11% 2 17% 32% 31% 7%	683
June	1st to 10th	Night	8% 1 13% 38% 34% 6%	630
	11th to 20th	Night	5% 2 13% 29% 42% 9%	630
	21st to end	Night	6% 1 10% 30% 40% 12%	630
July	1st to 10th	Night	6% 1 7% 27% 46% 13%	615
	11th to 20th	Night	6% 1 4 26% 45% 18%	612
	21st to end	Night	3 2 6% 32% 43% 14%	687
August	1st to 10th	Night	5% 3 25% 48% 18%	597
	11th to 20th	Night	6% 1 3 27% 46% 16%	594
	21st to end	Night	10% 2 7% 23% 43% 15%	660
September	1st to 10th	Night	10% 3 8% 28% 41% 10%	600
	11th to 20th	Night	13% 2 9% 30% 41% 6%	725
	21st to end	Night	10% 3 11% 34% 37% 5%	800
October	1st to 10th	Night	9% 2 22% 32% 30% 5%	800
	11th to 20th	Night	12% 6% 20% 36% 24% 3	800
	21st to end	Night	16% 7% 21% 34% 20% 2	880
November	1st to 10th	Night	13% 5% 22% 35% 22% 3	820
	11th to 20th	Night	15% 7% 29% 35% 12% 2	840
	21st to end	Night	15% 10% 27% 32% 14% 2	840
December	1st to 10th	Night	21% 10% 28% 31% 9%	840
	11th to 20th	Night	21% 10% 31% 28% 10%	840
	21st to end	Night	24% 12% 30% 29% 5%	924

Page generated at 2026-07-28 02:25:26. Version ac07

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