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 2025-03-27.

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% 2 6% 5% 4 4 4 6% 7% 43%	109764
	Night	12% 7% 2 6% 4 4 4 3 5% 7% 46%	109446
Transparency	Day	38% 6% 10% 20% 20% 7%	113570
	Night	36% 5% 10% 19% 21% 8%	113766
Seeing	Day	15% 9% 22% 25% 20% 9%	15248
	Night	15% 7% 23% 30% 21% 4	24846

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	16% 8% 5% 6% 3 3 3 2 4 4 47%	4056
	11th to 20th	Day	10% 6% 3 6% 3 4 3 3 5% 6% 51%	4455
	21st to end	Day	21% 11% 3 6% 3 3 3 2 3 5% 40%	4972
February	1st to 10th	Day	16% 9% 3 6% 5% 4 4 3 4 7% 39%	2000
	11th to 20th	Day	19% 9% 3 5% 4 4 3 3 4 5% 41%	1948
	21st to end	Day	16% 8% 3 8% 4 4 4 3 5% 5% 40%	1650
March	1st to 10th	Day	21% 9% 3 7% 5% 5% 4 3 5% 6% 31%	3220
	11th to 20th	Day	14% 7% 2 5% 4 5% 4 3 7% 8% 39%	3439
	21st to end	Day	16% 7% 2 7% 5% 5% 4 4 5% 5% 41%	4232
April	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 5% 6% 46%	2280
	11th to 20th	Day	14% 7% 2 6% 5% 3 4 3 5% 7% 45%	2254
	21st to end	Day	8% 5% 2 4 5% 4 5% 4 6% 8% 50%	2280
May	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 4 7% 9% 45%	3765
	11th to 20th	Day	12% 6% 2 7% 5% 5% 4 4 5% 7% 41%	3980
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 44%	4476
June	1st to 10th	Day	10% 6% 2 6% 5% 6% 6% 6% 6% 10% 37%	2470
	11th to 20th	Day	5% 4 3 6% 6% 5% 7% 4 9% 9% 42%	2564
	21st to end	Day	6% 5% 2 6% 6% 7% 6% 6% 8% 11% 38%	2660
July	1st to 10th	Day	6% 6% 2 9% 8% 7% 8% 7% 9% 11% 28%	4440
	11th to 20th	Day	8% 5% 3 6% 6% 7% 6% 6% 9% 11% 32%	4007
	21st to end	Day	9% 8% 4 10% 8% 8% 6% 6% 8% 9% 24%	4118
August	1st to 10th	Day	3 3 1 4 3 3 4 4 6% 9% 59%	3785
	11th to 20th	Day	5% 3 2 6% 5% 5% 6% 5% 6% 10% 47%	3729
	21st to end	Day	7% 3 2 6% 5% 5% 5% 4 7% 9% 45%	4180
September	1st to 10th	Day	11% 5% 2 8% 6% 5% 5% 5% 6% 7% 40%	2280
	11th to 20th	Day	13% 7% 2 6% 5% 5% 4 4 5% 7% 42%	2142
	21st to end	Day	11% 5% 2 5% 4 4 3 4 4 7% 51%	2090
October	1st to 10th	Day	8% 5% 2 6% 3 4 3 3 4 5% 58%	2090
	11th to 20th	Day	9% 5% 2 5% 3 3 3 3 5% 7% 56%	1952
	21st to end	Day	11% 4 2 4 4 2 3 2 4 6% 57%	2090
November	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 4 5% 54%	1791
	11th to 20th	Day	12% 6% 2 5% 4 4 3 3 4 5% 53%	1800
	21st to end	Day	14% 6% 2 6% 4 4 3 3 5% 5% 49%	1800
December	1st to 10th	Day	15% 8% 3 6% 4 3 3 2 5% 6% 45%	2930
	11th to 20th	Day	12% 9% 3 8% 5% 4 4 3 4 5% 44%	3373
	21st to end	Day	16% 8% 2 5% 3 3 3 3 4 5% 46%	4466
January	1st to 10th	Night	17% 10% 3 5% 2 3 3 2 3 4 48%	5789
	11th to 20th	Night	15% 8% 4 6% 3 3 3 2 4 5% 47%	5440
	21st to end	Night	21% 11% 2 5% 4 3 3 2 3 4 42%	5984
February	1st to 10th	Night	16% 8% 3 6% 4 4 4 3 5% 6% 43%	2400
	11th to 20th	Night	20% 8% 2 6% 4 3 3 2 4 4 43%	2338
	21st to end	Night	17% 8% 2 7% 4 4 4 3 5% 5% 41%	1980
March	1st to 10th	Night	22% 12% 3 6% 3 4 3 2 4 6% 34%	3853
	11th to 20th	Night	11% 7% 2 7% 5% 4 4 3 5% 7% 44%	3769
	21st to end	Night	16% 7% 2 7% 4 4 4 3 5% 6% 42%	3536
April	1st to 10th	Night	11% 5% 2 5% 5% 4 4 4 6% 6% 48%	1900
	11th to 20th	Night	12% 7% 2 4 3 4 4 4 5% 7% 48%	1875
	21st to end	Night	8% 4 1 4 3 4 4 3 6% 9% 53%	1900
May	1st to 10th	Night	8% 6% 2 6% 5% 4 4 4 6% 9% 46%	3130
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 5% 8% 42%	2910
	21st to end	Night	6% 4 2 6% 4 5% 5% 5% 8% 11% 44%	3079
June	1st to 10th	Night	6% 5% 2 6% 5% 5% 7% 8% 7% 10% 40%	1710
	11th to 20th	Night	3 5% 2 6% 4 4 5% 4 9% 10% 48%	1607
	21st to end	Night	5% 4 2 5% 4 6% 5% 4 8% 13% 43%	1520
July	1st to 10th	Night	6% 5% 3 8% 7% 6% 6% 6% 8% 12% 34%	2530
	11th to 20th	Night	6% 5% 2 7% 5% 6% 7% 6% 10% 13% 32%	2944
	21st to end	Night	7% 8% 4 10% 7% 6% 7% 6% 8% 11% 27%	3435
August	1st to 10th	Night	2 2 1 3 3 3 4 4 7% 12% 57%	3144
	11th to 20th	Night	4 2 1 5% 4 5% 6% 5% 7% 12% 50%	3100
	21st to end	Night	5% 3 2 6% 5% 6% 6% 5% 7% 10% 46%	3476
September	1st to 10th	Night	9% 6% 1 6% 5% 6% 5% 5% 6% 7% 43%	1900
	11th to 20th	Night	10% 7% 2 5% 5% 4 4 3 5% 8% 46%	2019
	21st to end	Night	7% 5% 2 6% 4 3 4 4 6% 7% 53%	2090
October	1st to 10th	Night	8% 4 1 5% 3 3 4 3 5% 6% 59%	2090
	11th to 20th	Night	10% 5% 1 4 3 3 4 3 4 6% 57%	2223
	21st to end	Night	13% 5% 2 5% 3 3 2 2 3 4 58%	2508
November	1st to 10th	Night	10% 4 2 5% 3 3 4 3 3 6% 57%	2505
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 6% 54%	2600
	21st to end	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2600
December	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 5% 5% 47%	4250
	11th to 20th	Night	14% 9% 3 7% 4 4 3 2 4 5% 45%	4822
	21st to end	Night	17% 8% 3 6% 3 3 2 2 4 6% 45%	6490

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	42% 2 4 27% 21% 4	4057
	11th to 20th	Day	34% 3 6% 20% 29% 8%	4455
	21st to end	Day	49% 2 6% 14% 16% 13%	4972
February	1st to 10th	Day	47% 4 7% 16% 18% 8%	2000
	11th to 20th	Day	47% 3 5% 17% 20% 8%	1958
	21st to end	Day	45% 5% 7% 16% 17% 10%	1650
March	1st to 10th	Day	52% 5% 8% 11% 17% 6%	3220
	11th to 20th	Day	41% 5% 8% 19% 18% 8%	3439
	21st to end	Day	44% 5% 7% 16% 21% 7%	4232
April	1st to 10th	Day	38% 5% 9% 20% 20% 8%	2280
	11th to 20th	Day	39% 4 7% 19% 23% 7%	2254
	21st to end	Day	31% 6% 10% 24% 25% 5%	2280
May	1st to 10th	Day	34% 7% 13% 28% 17% 3	3800
	11th to 20th	Day	40% 7% 13% 23% 17% 1	3984
	21st to end	Day	33% 8% 14% 30% 14% 1	4489
June	1st to 10th	Day	41% 7% 14% 22% 13% 2	2470
	11th to 20th	Day	34% 8% 17% 22% 15% 2	2564
	21st to end	Day	36% 9% 16% 23% 13% 3	2660
July	1st to 10th	Day	43% 11% 19% 20% 6% 1	4371
	11th to 20th	Day	39% 11% 25% 21% 4 1	3936
	21st to end	Day	52% 11% 12% 18% 6% 1	3987
August	1st to 10th	Day	21% 6% 13% 31% 28% 1	3773
	11th to 20th	Day	31% 8% 16% 29% 14% 2	3765
	21st to end	Day	33% 9% 14% 21% 19% 3	4179
September	1st to 10th	Day	41% 7% 13% 16% 16% 6%	2280
	11th to 20th	Day	41% 7% 11% 16% 21% 5%	2142
	21st to end	Day	33% 4 9% 25% 21% 8%	2090
October	1st to 10th	Day	23% 3 5% 14% 30% 26%	3480
	11th to 20th	Day	18% 2 4 15% 31% 30%	3218
	21st to end	Day	22% 2 3 17% 38% 17%	3428
November	1st to 10th	Day	34% 3 7% 18% 27% 11%	1791
	11th to 20th	Day	34% 3 7% 15% 28% 14%	1800
	21st to end	Day	38% 4 7% 18% 24% 10%	1800
December	1st to 10th	Day	41% 3 6% 18% 27% 4	2930
	11th to 20th	Day	44% 3 8% 18% 20% 7%	3370
	21st to end	Day	41% 3 6% 23% 26% 2	4466
January	1st to 10th	Night	43% 2 4 21% 26% 4	5789
	11th to 20th	Night	41% 3 5% 16% 26% 10%	5440
	21st to end	Night	49% 2 3 14% 23% 9%	5984
February	1st to 10th	Night	43% 3 7% 16% 21% 10%	2400
	11th to 20th	Night	46% 3 6% 15% 19% 11%	2339
	21st to end	Night	45% 5% 6% 16% 16% 12%	1980
March	1st to 10th	Night	51% 4 8% 14% 16% 8%	3853
	11th to 20th	Night	39% 5% 10% 18% 19% 10%	3769
	21st to end	Night	42% 5% 9% 18% 20% 6%	3536
April	1st to 10th	Night	36% 5% 11% 18% 19% 10%	1900
	11th to 20th	Night	35% 4 9% 19% 22% 11%	1875
	21st to end	Night	27% 5% 10% 25% 26% 7%	1900
May	1st to 10th	Night	33% 8% 12% 25% 19% 4	3160
	11th to 20th	Night	39% 6% 12% 24% 17% 1	2911
	21st to end	Night	30% 9% 15% 24% 19% 3	3087
June	1st to 10th	Night	34% 11% 15% 22% 15% 2	1710
	11th to 20th	Night	27% 10% 17% 28% 15% 4	1607
	21st to end	Night	30% 10% 20% 21% 16% 3	1520
July	1st to 10th	Night	38% 13% 24% 18% 5% 2	2490
	11th to 20th	Night	37% 12% 27% 19% 4 1	2892
	21st to end	Night	47% 12% 18% 17% 5% 1	3325
August	1st to 10th	Night	19% 7% 17% 32% 24% 1	3132
	11th to 20th	Night	25% 9% 20% 29% 14% 2	3130
	21st to end	Night	33% 9% 14% 20% 18% 5%	3476
September	1st to 10th	Night	38% 8% 14% 18% 17% 6%	1900
	11th to 20th	Night	36% 6% 14% 17% 20% 8%	2019
	21st to end	Night	30% 5% 9% 25% 23% 9%	2090
October	1st to 10th	Night	21% 3 7% 12% 26% 30%	3480
	11th to 20th	Night	18% 3 3 16% 27% 33%	3683
	21st to end	Night	21% 2 5% 15% 36% 21%	4120
November	1st to 10th	Night	30% 4 7% 17% 27% 14%	2505
	11th to 20th	Night	32% 3 6% 16% 29% 14%	2600
	21st to end	Night	36% 4 6% 22% 19% 13%	2600
December	1st to 10th	Night	40% 3 7% 19% 25% 6%	4250
	11th to 20th	Night	44% 3 6% 17% 25% 5%	4824
	21st to end	Night	41% 3 6% 19% 29% 2	6490

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	26% 24% 35% 12% 3 1	300
	11th to 20th	Day	22% 22% 35% 14% 6% 1	300
	21st to end	Day	26% 23% 34% 12% 3 1	330
February	1st to 10th	Day	25% 17% 38% 14% 6%	300
	11th to 20th	Day	34% 20% 34% 10% 3	300
	21st to end	Day	25% 24% 39% 10% 2	249
March	1st to 10th	Day	26% 21% 35% 13% 5%	300
	11th to 20th	Day	26% 21% 34% 16% 3	300
	21st to end	Day	24% 14% 34% 22% 7%	525
April	1st to 10th	Day	18% 15% 33% 20% 11% 2	460
	11th to 20th	Day	25% 12% 27% 23% 10% 2	452
	21st to end	Day	11% 13% 30% 31% 14% 2	460
May	1st to 10th	Day	15% 8% 26% 29% 17% 4	463
	11th to 20th	Day	9% 5% 23% 33% 18% 11%	487
	21st to end	Day	8% 4 23% 32% 21% 13%	529
June	1st to 10th	Day	13% 3 13% 33% 27% 11%	490
	11th to 20th	Day	6% 3 14% 30% 32% 15%	584
	21st to end	Day	7% 2 13% 30% 32% 15%	680
July	1st to 10th	Day	7% 1 8% 31% 37% 17%	671
	11th to 20th	Day	9% 2 4 23% 37% 25%	560
	21st to end	Day	7% 2 7% 26% 37% 21%	532
August	1st to 10th	Day	6% 2 7% 26% 34% 26%	486
	11th to 20th	Day	7% 1 6% 26% 37% 24%	479
	21st to end	Day	15% 1 7% 24% 32% 21%	539
September	1st to 10th	Day	10% 3 10% 33% 29% 16%	490
	11th to 20th	Day	14% 2 13% 23% 33% 15%	490
	21st to end	Day	14% 3 14% 29% 29% 11%	490
October	1st to 10th	Day	9% 4 23% 30% 24% 8%	490
	11th to 20th	Day	10% 7% 26% 36% 18% 3	352
	21st to end	Day	17% 10% 25% 30% 14% 5%	330
November	1st to 10th	Day	21% 10% 30% 26% 10% 4	300
	11th to 20th	Day	18% 11% 37% 23% 10%	300
	21st to end	Day	14% 15% 39% 19% 11% 2	300
December	1st to 10th	Day	24% 15% 37% 18% 7%	300
	11th to 20th	Day	21% 14% 38% 19% 6% 1	300
	21st to end	Day	28% 13% 33% 21% 6%	330
January	1st to 10th	Night	23% 14% 36% 22% 6%	877
	11th to 20th	Night	22% 14% 31% 26% 6%	800
	21st to end	Night	23% 14% 35% 25% 3	880
February	1st to 10th	Night	22% 12% 31% 30% 5%	800
	11th to 20th	Night	27% 15% 31% 22% 5%	783
	21st to end	Night	22% 17% 38% 22% 2	660
March	1st to 10th	Night	20% 15% 31% 27% 7%	800
	11th to 20th	Night	17% 12% 37% 27% 6% 1	714
	21st to end	Night	15% 13% 34% 26% 11%	647
April	1st to 10th	Night	16% 11% 34% 28% 11%	570
	11th to 20th	Night	14% 11% 33% 29% 12% 1	563
	21st to end	Night	8% 8% 33% 35% 15% 1	570
May	1st to 10th	Night	9% 4 30% 35% 19% 2	570
	11th to 20th	Night	11% 2 22% 39% 24% 2	561
	21st to end	Night	9% 2 16% 31% 34% 8%	617
June	1st to 10th	Night	8% 1 13% 37% 35% 6%	570
	11th to 20th	Night	4 1 12% 29% 44% 10%	570
	21st to end	Night	6% 1 10% 31% 39% 13%	570
July	1st to 10th	Night	6% 1 7% 27% 45% 14%	555
	11th to 20th	Night	5% 1 4 26% 45% 18%	552
	21st to end	Night	3 2 6% 31% 43% 14%	624
August	1st to 10th	Night	4 3 26% 48% 19%	567
	11th to 20th	Night	7% 1 3 28% 46% 15%	564
	21st to end	Night	10% 2 7% 22% 43% 16%	627
September	1st to 10th	Night	11% 3 7% 26% 42% 11%	570
	11th to 20th	Night	13% 2 9% 30% 40% 6%	689
	21st to end	Night	10% 3 11% 33% 38% 5%	760
October	1st to 10th	Night	9% 1 21% 32% 31% 6%	760
	11th to 20th	Night	12% 6% 20% 35% 23% 3	760
	21st to end	Night	16% 6% 21% 34% 21% 2	836
November	1st to 10th	Night	13% 6% 22% 35% 22% 3	780
	11th to 20th	Night	16% 8% 28% 35% 12% 2	800
	21st to end	Night	16% 10% 26% 32% 14% 2	800
December	1st to 10th	Night	20% 11% 28% 32% 10%	800
	11th to 20th	Night	21% 9% 32% 28% 10%	800
	21st to end	Night	24% 12% 30% 28% 5%	880

Page generated at 2025-03-24 08:04:28. Version ac07

Copyright © 2025 Attilla Danko.