Quincy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quincy clear sky chart from 2005-11-06 to 2026-02-01.

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	10% 6% 2 7% 5% 5% 6% 5% 7% 9% 40%	127377
	Night	10% 6% 2 6% 4 4 4 4 6% 9% 45%	124649
Transparency	Day	37% 9% 13% 17% 16% 8%	131215
	Night	35% 8% 13% 18% 18% 9%	128880
Seeing	Day	11% 9% 23% 26% 20% 11%	16580
	Night	11% 7% 22% 31% 23% 5%	26618

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	10% 7% 2 6% 4 3 4 2 4 5% 54%	4146
	11th to 20th	Day	15% 7% 2 5% 4 3 4 3 5% 7% 45%	4221
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 9% 42%	5082
February	1st to 10th	Day	14% 8% 3 6% 4 4 4 3 5% 6% 42%	2000
	11th to 20th	Day	16% 7% 2 6% 3 3 4 3 5% 6% 46%	1948
	21st to end	Day	14% 8% 2 5% 5% 4 3 4 5% 7% 45%	1650
March	1st to 10th	Day	20% 7% 2 6% 3 4 3 3 6% 7% 39%	4635
	11th to 20th	Day	7% 4 2 5% 4 4 5% 3 6% 8% 52%	4980
	21st to end	Day	13% 6% 2 5% 3 4 4 4 5% 6% 48%	5465
April	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 5% 7% 46%	2215
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 5% 6% 48%	2374
	21st to end	Day	5% 4 2 5% 5% 4 5% 4 5% 7% 52%	2447
May	1st to 10th	Day	9% 6% 2 8% 5% 5% 5% 4 6% 8% 41%	5862
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 7% 10% 42%	5861
	21st to end	Day	4 3 2 6% 5% 6% 7% 5% 8% 12% 43%	6433
June	1st to 10th	Day	9% 7% 3 9% 7% 8% 8% 5% 8% 9% 27%	2600
	11th to 20th	Day	5% 4 2 8% 8% 8% 8% 7% 10% 11% 29%	2600
	21st to end	Day	7% 6% 3 8% 8% 7% 9% 6% 8% 9% 27%	2600
July	1st to 10th	Day	6% 7% 4 11% 9% 10% 10% 7% 10% 11% 16%	5900
	11th to 20th	Day	5% 3 2 7% 7% 7% 8% 6% 9% 13% 34%	5900
	21st to end	Day	4 5% 2 9% 8% 8% 9% 8% 10% 13% 23%	6424
August	1st to 10th	Day	8% 5% 3 8% 7% 8% 8% 7% 9% 10% 27%	3951
	11th to 20th	Day	7% 4 2 6% 5% 6% 6% 6% 8% 11% 39%	3849
	21st to end	Day	7% 6% 3 9% 6% 7% 8% 6% 8% 11% 28%	4279
September	1st to 10th	Day	9% 7% 4 8% 7% 6% 7% 5% 9% 11% 29%	2200
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 5% 6% 9% 34%	2200
	21st to end	Day	12% 4 2 5% 5% 4 5% 4 5% 8% 46%	2200
October	1st to 10th	Day	10% 6% 3 7% 5% 4 5% 3 4 6% 47%	2200
	11th to 20th	Day	7% 3 1 3 4 3 4 3 4 6% 61%	2165
	21st to end	Day	8% 4 2 6% 4 4 4 3 5% 7% 54%	2200
November	1st to 10th	Day	9% 5% 1 4 3 3 4 3 5% 6% 57%	1962
	11th to 20th	Day	10% 5% 2 4 3 3 3 3 5% 7% 55%	1890
	21st to end	Day	10% 6% 2 6% 4 4 4 4 5% 7% 48%	1890
December	1st to 10th	Day	12% 6% 2 6% 4 3 4 2 4 6% 51%	3020
	11th to 20th	Day	12% 7% 2 6% 4 3 4 3 4 6% 48%	3463
	21st to end	Day	17% 8% 2 6% 4 3 3 3 4 6% 44%	4565
January	1st to 10th	Night	11% 5% 2 6% 4 3 3 3 6% 6% 50%	6019
	11th to 20th	Night	14% 8% 3 7% 4 5% 4 4 5% 6% 41%	5956
	21st to end	Night	17% 8% 2 5% 3 4 4 3 5% 7% 41%	6116
February	1st to 10th	Night	14% 8% 2 6% 4 4 4 3 5% 6% 44%	2401
	11th to 20th	Night	15% 7% 3 5% 4 4 3 3 4 6% 47%	2338
	21st to end	Night	13% 6% 2 6% 4 3 4 4 4 6% 47%	1980
March	1st to 10th	Night	19% 10% 3 6% 4 3 3 3 4 7% 38%	5217
	11th to 20th	Night	10% 5% 2 4 3 3 4 4 6% 9% 51%	4980
	21st to end	Night	14% 6% 2 5% 3 3 3 3 5% 7% 49%	5467
April	1st to 10th	Night	9% 6% 2 5% 4 4 4 4 6% 8% 49%	2200
	11th to 20th	Night	9% 4 2 6% 4 4 4 3 5% 7% 51%	1975
	21st to end	Night	5% 3 2 5% 4 4 4 4 5% 7% 58%	1950
May	1st to 10th	Night	8% 6% 3 6% 5% 4 4 3 5% 10% 47%	4033
	11th to 20th	Night	12% 7% 3 5% 4 4 4 3 6% 9% 43%	4032
	21st to end	Night	4 3 1 5% 4 4 4 4 7% 11% 51%	4421
June	1st to 10th	Night	5% 5% 3 6% 5% 5% 7% 5% 8% 13% 37%	1800
	11th to 20th	Night	4 4 2 5% 7% 6% 5% 6% 9% 13% 40%	1800
	21st to end	Night	5% 5% 2 7% 6% 6% 6% 7% 8% 12% 36%	1800
July	1st to 10th	Night	5% 7% 3 10% 7% 8% 9% 7% 11% 12% 21%	4058
	11th to 20th	Night	2 3 2 5% 5% 5% 7% 6% 9% 15% 40%	4057
	21st to end	Night	4 4 2 8% 6% 7% 8% 7% 11% 14% 30%	4427
August	1st to 10th	Night	8% 5% 2 6% 4 4 6% 5% 9% 13% 36%	3192
	11th to 20th	Night	3 4 2 5% 5% 5% 7% 5% 9% 13% 42%	3200
	21st to end	Night	7% 6% 3 8% 6% 6% 7% 6% 9% 12% 30%	3586
September	1st to 10th	Night	9% 7% 2 8% 6% 5% 6% 5% 8% 12% 31%	2197
	11th to 20th	Night	9% 7% 3 8% 5% 5% 6% 5% 7% 9% 37%	2200
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 6% 8% 47%	2200
October	1st to 10th	Night	6% 5% 3 6% 4 5% 4 3 5% 8% 51%	2200
	11th to 20th	Night	7% 4 2 4 3 2 3 2 4 6% 63%	2232
	21st to end	Night	8% 5% 2 6% 3 4 4 3 5% 5% 56%	2640
November	1st to 10th	Night	8% 5% 2 5% 3 4 3 3 5% 6% 54%	2550
	11th to 20th	Night	10% 6% 2 5% 4 3 3 3 5% 6% 55%	2730
	21st to end	Night	11% 6% 2 5% 3 3 3 4 5% 7% 50%	2730
December	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 4 5% 55%	4380
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 4 6% 53%	4952
	21st to end	Night	16% 7% 2 6% 4 3 3 3 4 6% 45%	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	33% 4 6% 15% 31% 11%	4147
	11th to 20th	Day	37% 5% 7% 14% 24% 14%	4221
	21st to end	Day	38% 5% 9% 17% 19% 12%	5082
February	1st to 10th	Day	42% 4 8% 16% 21% 9%	2000
	11th to 20th	Day	38% 5% 6% 14% 23% 13%	1958
	21st to end	Day	38% 5% 10% 15% 20% 12%	1650
March	1st to 10th	Day	42% 6% 9% 15% 17% 11%	4635
	11th to 20th	Day	28% 6% 9% 14% 21% 22%	4980
	21st to end	Day	35% 7% 9% 22% 16% 12%	5465
April	1st to 10th	Day	37% 6% 10% 17% 17% 14%	2215
	11th to 20th	Day	36% 6% 7% 19% 20% 13%	2374
	21st to end	Day	29% 7% 10% 21% 21% 11%	2447
May	1st to 10th	Day	38% 10% 13% 18% 17% 5%	5897
	11th to 20th	Day	35% 8% 14% 28% 13% 2	5865
	21st to end	Day	29% 10% 17% 22% 20% 3	6447
June	1st to 10th	Day	47% 12% 15% 17% 7% 1	2600
	11th to 20th	Day	41% 15% 19% 15% 8% 1	2600
	21st to end	Day	46% 15% 18% 14% 6% 2	2600
July	1st to 10th	Day	52% 18% 22% 7% 1	5835
	11th to 20th	Day	36% 15% 32% 15% 2	5831
	21st to end	Day	43% 19% 21% 16% 1	6240
August	1st to 10th	Day	45% 13% 18% 15% 8% 1	3938
	11th to 20th	Day	34% 12% 18% 23% 13% 1	3885
	21st to end	Day	44% 12% 20% 18% 6% 1	4279
September	1st to 10th	Day	45% 12% 17% 16% 8% 2	2200
	11th to 20th	Day	44% 10% 14% 17% 12% 3	2200
	21st to end	Day	35% 7% 13% 21% 17% 8%	2200
October	1st to 10th	Day	43% 5% 7% 10% 17% 18%	3590
	11th to 20th	Day	16% 3 5% 18% 25% 32%	3509
	21st to end	Day	21% 3 5% 15% 38% 18%	3538
November	1st to 10th	Day	28% 5% 9% 19% 24% 16%	1962
	11th to 20th	Day	29% 5% 8% 16% 27% 16%	1890
	21st to end	Day	34% 6% 8% 19% 23% 10%	1890
December	1st to 10th	Day	35% 4 7% 16% 26% 11%	3020
	11th to 20th	Day	36% 5% 7% 21% 22% 9%	3460
	21st to end	Day	43% 4 5% 18% 25% 5%	4565
January	1st to 10th	Night	33% 4 7% 13% 29% 14%	6019
	11th to 20th	Night	43% 4 5% 14% 25% 9%	5956
	21st to end	Night	42% 4 8% 18% 20% 8%	6116
February	1st to 10th	Night	40% 6% 8% 15% 20% 12%	2401
	11th to 20th	Night	40% 5% 7% 13% 19% 15%	2339
	21st to end	Night	37% 7% 8% 15% 18% 15%	1980
March	1st to 10th	Night	46% 6% 8% 13% 19% 9%	5217
	11th to 20th	Night	27% 6% 10% 18% 20% 19%	4980
	21st to end	Night	35% 6% 8% 20% 18% 13%	5467
April	1st to 10th	Night	32% 7% 12% 18% 19% 13%	2200
	11th to 20th	Night	31% 6% 10% 17% 24% 12%	1975
	21st to end	Night	24% 7% 10% 27% 22% 10%	1950
May	1st to 10th	Night	31% 10% 18% 23% 13% 5%	4060
	11th to 20th	Night	35% 8% 16% 26% 13% 2	4033
	21st to end	Night	23% 9% 19% 33% 14% 3	4429
June	1st to 10th	Night	34% 13% 21% 20% 10% 2	1800
	11th to 20th	Night	29% 14% 25% 20% 9% 2	1800
	21st to end	Night	35% 15% 22% 18% 8% 1	1800
July	1st to 10th	Night	50% 17% 24% 8% 1	4015
	11th to 20th	Night	28% 17% 39% 14% 2	4006
	21st to end	Night	38% 17% 27% 16% 1	4297
August	1st to 10th	Night	34% 12% 25% 20% 8%	3181
	11th to 20th	Night	29% 13% 25% 24% 8% 1	3230
	21st to end	Night	40% 14% 23% 16% 5% 1	3586
September	1st to 10th	Night	41% 13% 20% 15% 8% 2	2197
	11th to 20th	Night	41% 13% 14% 16% 14% 2	2200
	21st to end	Night	32% 9% 17% 18% 17% 7%	2200
October	1st to 10th	Night	39% 6% 10% 12% 19% 16%	3590
	11th to 20th	Night	15% 3 5% 17% 31% 29%	3627
	21st to end	Night	20% 3 5% 14% 39% 18%	4252
November	1st to 10th	Night	30% 5% 7% 19% 22% 17%	2550
	11th to 20th	Night	31% 5% 6% 16% 27% 16%	2730
	21st to end	Night	33% 5% 11% 18% 20% 13%	2730
December	1st to 10th	Night	33% 4 8% 17% 24% 15%	4380
	11th to 20th	Night	34% 5% 8% 20% 22% 11%	4954
	21st to end	Night	41% 5% 7% 17% 26% 5%	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	16% 18% 45% 18% 4	330
	11th to 20th	Day	15% 19% 37% 21% 6% 2	330
	21st to end	Day	22% 24% 40% 11% 3	363
February	1st to 10th	Day	18% 18% 38% 20% 6%	300
	11th to 20th	Day	28% 15% 38% 16% 3	300
	21st to end	Day	15% 21% 41% 18% 4	249
March	1st to 10th	Day	14% 22% 37% 21% 6%	364
	11th to 20th	Day	16% 17% 34% 23% 10% 1	500
	21st to end	Day	14% 18% 32% 24% 11% 1	550
April	1st to 10th	Day	14% 15% 31% 26% 12% 1	500
	11th to 20th	Day	11% 14% 33% 29% 12% 2	492
	21st to end	Day	7% 11% 26% 35% 17% 4	500
May	1st to 10th	Day	8% 9% 27% 32% 17% 7%	503
	11th to 20th	Day	10% 4 24% 31% 20% 10%	527
	21st to end	Day	9% 1 19% 32% 24% 15%	573
June	1st to 10th	Day	12% 3 15% 29% 26% 15%	530
	11th to 20th	Day	5% 3 13% 25% 30% 22%	530
	21st to end	Day	7% 3 8% 28% 29% 24%	530
July	1st to 10th	Day	6% 3 7% 19% 30% 35%	525
	11th to 20th	Day	6% 2 5% 19% 35% 34%	524
	21st to end	Day	5% 1 6% 23% 36% 29%	576
August	1st to 10th	Day	10% 2 7% 19% 34% 28%	526
	11th to 20th	Day	8% 2 4 19% 37% 29%	519
	21st to end	Day	9% 3 9% 27% 30% 21%	583
September	1st to 10th	Day	12% 4 11% 24% 28% 20%	530
	11th to 20th	Day	13% 3 11% 31% 29% 13%	530
	21st to end	Day	12% 3 11% 27% 33% 14%	530
October	1st to 10th	Day	11% 7% 27% 35% 16% 5%	530
	11th to 20th	Day	7% 5% 21% 35% 25% 6%	530
	21st to end	Day	11% 9% 26% 36% 18% 2	583
November	1st to 10th	Day	14% 5% 27% 31% 20% 4	440
	11th to 20th	Day	9% 14% 41% 24% 9% 3	330
	21st to end	Day	12% 14% 39% 26% 7% 2	330
December	1st to 10th	Day	17% 20% 30% 22% 10% 1	330
	11th to 20th	Day	18% 14% 37% 24% 6% 1	330
	21st to end	Day	20% 10% 33% 27% 8%	363
January	1st to 10th	Night	17% 14% 35% 26% 7% 1	840
	11th to 20th	Night	15% 13% 29% 32% 10% 1	840
	21st to end	Night	21% 13% 34% 26% 6%	924
February	1st to 10th	Night	18% 12% 29% 34% 8%	801
	11th to 20th	Night	19% 13% 31% 30% 7%	783
	21st to end	Night	14% 13% 37% 31% 4	660
March	1st to 10th	Night	16% 12% 29% 34% 9%	800
	11th to 20th	Night	13% 10% 33% 32% 12% 1	800
	21st to end	Night	11% 13% 33% 33% 10%	880
April	1st to 10th	Night	12% 9% 32% 35% 12%	800
	11th to 20th	Night	12% 7% 28% 36% 16% 1	593
	21st to end	Night	5% 5% 29% 39% 21% 1	600
May	1st to 10th	Night	6% 6% 22% 40% 24% 2	600
	11th to 20th	Night	7% 4 22% 35% 27% 5%	591
	21st to end	Night	6% 2 12% 38% 36% 6%	650
June	1st to 10th	Night	7% 2 11% 36% 38% 7%	600
	11th to 20th	Night	4 2 8% 31% 42% 14%	600
	21st to end	Night	6% 1 9% 30% 41% 14%	600
July	1st to 10th	Night	6% 2 6% 19% 50% 17%	585
	11th to 20th	Night	5% 1 4 18% 48% 24%	582
	21st to end	Night	3 1 5% 21% 52% 18%	657
August	1st to 10th	Night	7% 2 5% 20% 47% 20%	597
	11th to 20th	Night	6% 1 4 17% 54% 19%	594
	21st to end	Night	10% 2 8% 24% 39% 18%	660
September	1st to 10th	Night	11% 2 11% 26% 37% 13%	797
	11th to 20th	Night	11% 3 10% 37% 33% 7%	800
	21st to end	Night	10% 1 16% 31% 36% 6%	800
October	1st to 10th	Night	8% 2 26% 33% 27% 3	800
	11th to 20th	Night	9% 6% 21% 36% 26% 3	800
	21st to end	Night	9% 7% 23% 39% 21% 2	880
November	1st to 10th	Night	10% 6% 26% 37% 20% 2	820
	11th to 20th	Night	12% 9% 28% 35% 15% 1	840
	21st to end	Night	14% 8% 30% 33% 14% 1	840
December	1st to 10th	Night	16% 9% 30% 29% 15% 1	840
	11th to 20th	Night	14% 10% 30% 32% 13% 1	840
	21st to end	Night	20% 11% 26% 30% 11%	924

Page generated at 2026-01-29 01:21:44. Version ac07

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