Cranberry Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cranberry Corner clear sky chart from 2005-11-06 to 2026-07-16.

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	14% 10% 4 9% 5% 5% 5% 4 5% 6% 33%	138517
	Night	13% 11% 4 11% 6% 5% 4 4 5% 6% 31%	134515
Transparency	Day	50% 5% 12% 21% 11% 1	141946
	Night	53% 5% 11% 19% 10% 1	139172
Seeing	Day	20% 17% 34% 20% 8% 2	18427
	Night	19% 14% 34% 24% 8% 1	28293

By Month

Percentage Cloud Cover NE (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	8% 14% 6% 20% 13% 8% 4 3 4 4 15%	4691
	11th to 20th	Day	6% 18% 7% 16% 9% 9% 10% 6% 5% 4 9%	4679
	21st to end	Day	6% 11% 9% 16% 6% 7% 8% 4 6% 7% 20%	5156
February	1st to 10th	Day	8% 14% 5% 12% 6% 7% 7% 5% 6% 6% 24%	1886
	11th to 20th	Day	8% 12% 5% 15% 8% 4 6% 5% 6% 5% 27%	1886
	21st to end	Day	11% 13% 7% 13% 8% 7% 4 3 4 6% 22%	1730
March	1st to 10th	Day	14% 9% 3 10% 5% 5% 4 3 4 6% 38%	4578
	11th to 20th	Day	11% 12% 5% 12% 7% 5% 4 4 5% 7% 28%	4944
	21st to end	Day	22% 13% 5% 11% 4 4 3 3 3 4 27%	6001
April	1st to 10th	Day	15% 15% 6% 9% 6% 4 5% 4 4 5% 27%	2520
	11th to 20th	Day	18% 13% 6% 9% 5% 4 3 3 5% 4 29%	2494
	21st to end	Day	18% 12% 4 7% 6% 4 4 3 5% 5% 31%	2679
May	1st to 10th	Day	13% 8% 3 6% 4 4 4 3 5% 6% 45%	8241
	11th to 20th	Day	15% 9% 2 7% 4 4 4 4 5% 6% 40%	8222
	21st to end	Day	13% 8% 3 7% 4 4 4 3 5% 7% 41%	9061
June	1st to 10th	Day	16% 6% 2 6% 4 4 4 4 6% 8% 39%	2940
	11th to 20th	Day	16% 7% 3 6% 5% 5% 5% 4 5% 7% 36%	2940
	21st to end	Day	15% 6% 2 7% 4 5% 5% 4 6% 9% 36%	2940
July	1st to 10th	Day	13% 4 2 5% 4 4 5% 4 6% 8% 44%	6499
	11th to 20th	Day	12% 4 2 5% 4 3 4 3 5% 9% 50%	6431
	21st to end	Day	11% 5% 2 6% 5% 4 4 4 6% 8% 46%	6926
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 7% 38%	4563
	11th to 20th	Day	15% 5% 2 4 4 4 4 4 5% 7% 47%	4178
	21st to end	Day	15% 7% 2 7% 5% 4 5% 3 5% 8% 38%	4312
September	1st to 10th	Day	16% 7% 2 6% 4 4 4 4 5% 8% 41%	2400
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 5% 8% 40%	2360
	21st to end	Day	19% 9% 3 7% 4 4 4 3 5% 7% 36%	2191
October	1st to 10th	Day	18% 11% 2 6% 4 4 4 4 6% 6% 36%	2000
	11th to 20th	Day	20% 17% 4 7% 5% 4 5% 4 5% 6% 24%	1996
	21st to end	Day	21% 17% 4 8% 5% 4 3 4 5% 6% 26%	1980
November	1st to 10th	Day	16% 16% 4 8% 5% 4 4 4 5% 5% 28%	1852
	11th to 20th	Day	15% 18% 6% 12% 7% 5% 4 3 4 4 21%	1717
	21st to end	Day	14% 16% 8% 18% 8% 4 4 3 5% 4 16%	1680
December	1st to 10th	Day	8% 18% 9% 30% 8% 5% 4 3 3 3 10%	2690
	11th to 20th	Day	9% 20% 8% 17% 11% 5% 5% 2 4 4 16%	3084
	21st to end	Day	18% 23% 7% 14% 6% 5% 3 3 3 3 14%	4070
January	1st to 10th	Night	9% 14% 6% 22% 12% 8% 5% 2 3 4 15%	8233
	11th to 20th	Night	7% 17% 7% 17% 10% 8% 7% 7% 5% 5% 10%	8236
	21st to end	Night	6% 12% 7% 17% 7% 7% 6% 4 6% 7% 22%	9058
February	1st to 10th	Night	8% 13% 7% 12% 7% 6% 6% 4 7% 6% 23%	2730
	11th to 20th	Night	9% 10% 5% 12% 9% 7% 6% 4 6% 7% 25%	2620
	21st to end	Night	10% 17% 5% 10% 7% 5% 5% 4 6% 5% 25%	2076
March	1st to 10th	Night	11% 7% 3 9% 5% 4 4 4 6% 7% 40%	5482
	11th to 20th	Night	10% 13% 5% 14% 6% 5% 4 4 5% 6% 27%	5279
	21st to end	Night	20% 12% 5% 10% 6% 4 4 3 4 5% 27%	5171
April	1st to 10th	Night	19% 13% 4 9% 4 3 4 3 6% 5% 29%	2100
	11th to 20th	Night	22% 11% 4 7% 4 3 3 3 5% 5% 34%	2075
	21st to end	Night	19% 10% 4 6% 5% 3 4 4 5% 5% 36%	1937
May	1st to 10th	Night	11% 8% 3 6% 4 3 5% 3 5% 7% 47%	4688
	11th to 20th	Night	16% 9% 4 7% 4 3 4 3 4 4 42%	4670
	21st to end	Night	13% 7% 3 6% 4 3 4 3 5% 7% 45%	5148
June	1st to 10th	Night	12% 7% 2 7% 5% 4 4 3 5% 7% 44%	1680
	11th to 20th	Night	14% 7% 3 6% 5% 5% 5% 4 6% 6% 39%	1680
	21st to end	Night	15% 6% 2 5% 5% 4 4 3 6% 8% 42%	1680
July	1st to 10th	Night	12% 5% 2 4 4 3 4 4 6% 8% 48%	3700
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 7% 53%	3660
	21st to end	Night	11% 5% 1 5% 4 4 4 3 6% 7% 50%	3948
August	1st to 10th	Night	12% 6% 2 5% 5% 4 4 4 7% 7% 43%	2597
	11th to 20th	Night	14% 6% 2 4 3 2 3 3 4 6% 53%	2875
	21st to end	Night	17% 8% 2 6% 4 3 3 2 4 6% 45%	3586
September	1st to 10th	Night	14% 5% 3 4 3 4 4 4 5% 8% 48%	2000
	11th to 20th	Night	13% 6% 2 5% 4 3 5% 4 5% 8% 46%	2019
	21st to end	Night	16% 8% 3 6% 5% 4 4 3 5% 7% 39%	2205
October	1st to 10th	Night	17% 8% 2 5% 4 4 4 4 5% 7% 42%	2400
	11th to 20th	Night	18% 13% 5% 6% 4 5% 5% 3 5% 6% 31%	2403
	21st to end	Night	20% 15% 4 8% 5% 5% 4 3 5% 5% 27%	2860
November	1st to 10th	Night	16% 14% 5% 7% 4 4 4 3 5% 6% 32%	2666
	11th to 20th	Night	15% 18% 7% 12% 5% 4 3 3 3 5% 24%	2900
	21st to end	Night	14% 16% 6% 14% 7% 5% 5% 3 5% 6% 19%	2940
December	1st to 10th	Night	11% 14% 8% 22% 10% 5% 4 3 4 4 13%	4720
	11th to 20th	Night	9% 18% 8% 17% 8% 5% 5% 4 4 4 17%	5343
	21st to end	Night	21% 19% 5% 13% 8% 5% 3 3 3 4 15%	7150

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	72% 4 8% 12% 4	4692
	11th to 20th	Day	75% 4 7% 9% 4	4710
	21st to end	Day	62% 4 8% 16% 9%	5156
February	1st to 10th	Day	57% 5% 12% 16% 9%	1886
	11th to 20th	Day	57% 6% 10% 20% 7%	1895
	21st to end	Day	63% 5% 9% 14% 9% 1	1730
March	1st to 10th	Day	47% 4 16% 18% 14% 2	4580
	11th to 20th	Day	54% 6% 14% 16% 10% 1	4944
	21st to end	Day	62% 4 10% 13% 11%	6001
April	1st to 10th	Day	59% 5% 10% 16% 9% 1	2520
	11th to 20th	Day	58% 5% 10% 19% 8% 1	2494
	21st to end	Day	53% 6% 10% 18% 11% 1	2679
May	1st to 10th	Day	39% 6% 9% 27% 17% 2	8250
	11th to 20th	Day	43% 7% 10% 24% 14% 2	8226
	21st to end	Day	41% 5% 10% 23% 20% 2	9061
June	1st to 10th	Day	40% 7% 14% 26% 12% 1	2940
	11th to 20th	Day	46% 7% 13% 21% 13% 1	2940
	21st to end	Day	43% 9% 16% 23% 8% 1	2940
July	1st to 10th	Day	35% 7% 17% 33% 8% 1	6431
	11th to 20th	Day	31% 6% 18% 32% 11% 1	6356
	21st to end	Day	36% 6% 14% 29% 15%	6728
August	1st to 10th	Day	43% 7% 16% 22% 11% 1	4548
	11th to 20th	Day	37% 6% 16% 29% 11%	4219
	21st to end	Day	44% 6% 16% 23% 10% 1	4311
September	1st to 10th	Day	41% 6% 15% 27% 11%	2400
	11th to 20th	Day	42% 7% 19% 25% 7%	2360
	21st to end	Day	48% 6% 12% 25% 9%	2191
October	1st to 10th	Day	37% 4 15% 28% 15%	3260
	11th to 20th	Day	55% 4 9% 19% 13%	3224
	21st to end	Day	53% 5% 17% 19% 5%	3180
November	1st to 10th	Day	56% 6% 11% 18% 8% 1	1852
	11th to 20th	Day	67% 4 10% 12% 6%	1717
	21st to end	Day	70% 6% 11% 10% 3	1680
December	1st to 10th	Day	80% 4 7% 8% 2	2690
	11th to 20th	Day	73% 4 7% 9% 7%	3085
	21st to end	Day	76% 4 4 11% 5%	4070
January	1st to 10th	Night	73% 4 7% 11% 3	8233
	11th to 20th	Night	73% 5% 9% 9% 4	8280
	21st to end	Night	61% 4 8% 17% 10%	9058
February	1st to 10th	Night	59% 4 10% 17% 9% 1	2730
	11th to 20th	Night	54% 7% 11% 19% 8% 1	2621
	21st to end	Night	58% 5% 11% 16% 8% 1	2076
March	1st to 10th	Night	40% 6% 18% 19% 15% 2	5493
	11th to 20th	Night	55% 6% 12% 19% 7% 1	5280
	21st to end	Night	60% 5% 10% 14% 11%	5171
April	1st to 10th	Night	55% 5% 9% 17% 12% 1	2100
	11th to 20th	Night	51% 4 10% 21% 11% 2	2075
	21st to end	Night	49% 5% 11% 19% 14% 1	1937
May	1st to 10th	Night	36% 5% 13% 28% 16% 2	4695
	11th to 20th	Night	44% 7% 10% 20% 17% 2	4671
	21st to end	Night	39% 5% 12% 22% 19% 2	5149
June	1st to 10th	Night	37% 8% 15% 26% 13%	1680
	11th to 20th	Night	44% 7% 12% 21% 15% 1	1680
	21st to end	Night	39% 8% 14% 27% 10% 1	1680
July	1st to 10th	Night	33% 6% 19% 31% 9% 2	3660
	11th to 20th	Night	31% 5% 18% 34% 11% 1	3612
	21st to end	Night	32% 7% 15% 27% 17% 2	3832
August	1st to 10th	Night	38% 7% 15% 24% 15% 1	2588
	11th to 20th	Night	33% 7% 16% 31% 12% 1	2900
	21st to end	Night	41% 6% 14% 25% 12% 1	3586
September	1st to 10th	Night	35% 7% 14% 31% 12% 1	2000
	11th to 20th	Night	36% 6% 17% 33% 8%	2019
	21st to end	Night	44% 6% 14% 25% 10% 1	2205
October	1st to 10th	Night	33% 5% 9% 33% 19% 1	3920
	11th to 20th	Night	44% 5% 11% 27% 12%	3914
	21st to end	Night	57% 5% 11% 19% 7%	4610
November	1st to 10th	Night	52% 5% 14% 20% 9%	2666
	11th to 20th	Night	63% 4 12% 13% 7% 1	2900
	21st to end	Night	65% 6% 11% 13% 4 1	2940
December	1st to 10th	Night	74% 5% 9% 10% 2	4720
	11th to 20th	Night	69% 5% 9% 11% 6%	5341
	21st to end	Night	73% 4 6% 11% 6%	7150

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	18% 18% 37% 21% 5% 2	330
	11th to 20th	Day	24% 16% 35% 23% 2	330
	21st to end	Day	17% 18% 44% 18% 3	363
February	1st to 10th	Day	21% 22% 41% 12% 3 1	330
	11th to 20th	Day	15% 28% 40% 14% 3 1	330
	21st to end	Day	20% 27% 45% 7%	273
March	1st to 10th	Day	20% 26% 35% 16% 2	330
	11th to 20th	Day	22% 21% 39% 13% 5%	330
	21st to end	Day	25% 20% 34% 14% 4 2	546
April	1st to 10th	Day	26% 19% 36% 14% 5%	540
	11th to 20th	Day	31% 16% 28% 18% 6% 1	532
	21st to end	Day	24% 19% 31% 18% 6% 2	571
May	1st to 10th	Day	21% 21% 32% 17% 6% 2	753
	11th to 20th	Day	21% 18% 33% 18% 7% 2	775
	21st to end	Day	21% 14% 34% 19% 9% 2	844
June	1st to 10th	Day	17% 15% 33% 24% 8% 2	780
	11th to 20th	Day	21% 14% 38% 17% 8% 1	780
	21st to end	Day	15% 18% 33% 20% 10% 3	780
July	1st to 10th	Day	9% 9% 34% 29% 14% 5%	771
	11th to 20th	Day	14% 10% 35% 24% 13% 4	744
	21st to end	Day	9% 9% 38% 25% 13% 7%	794
August	1st to 10th	Day	14% 10% 29% 28% 15% 4	726
	11th to 20th	Day	16% 9% 24% 31% 16% 4	675
	21st to end	Day	18% 11% 27% 25% 15% 3	583
September	1st to 10th	Day	19% 15% 24% 26% 12% 4	530
	11th to 20th	Day	17% 8% 33% 29% 11% 2	530
	21st to end	Day	23% 16% 24% 24% 10% 3	521
October	1st to 10th	Day	21% 21% 30% 18% 8% 2	330
	11th to 20th	Day	25% 28% 29% 13% 4	330
	21st to end	Day	31% 22% 33% 12% 1 1	363
November	1st to 10th	Day	27% 18% 37% 14% 5%	330
	11th to 20th	Day	26% 25% 37% 9% 2 1	330
	21st to end	Day	22% 23% 41% 10% 3	330
December	1st to 10th	Day	17% 20% 44% 15% 4	330
	11th to 20th	Day	24% 25% 35% 15% 2	330
	21st to end	Day	24% 26% 36% 12% 2 1	363
January	1st to 10th	Night	16% 18% 42% 19% 4 1	1050
	11th to 20th	Night	18% 17% 42% 16% 5% 1	1050
	21st to end	Night	18% 14% 41% 21% 5%	1155
February	1st to 10th	Night	17% 17% 39% 20% 6%	1050
	11th to 20th	Night	15% 20% 38% 21% 5% 1	986
	21st to end	Night	19% 16% 41% 21% 3	692
March	1st to 10th	Night	17% 17% 36% 24% 6% 1	840
	11th to 20th	Night	20% 16% 38% 20% 6%	716
	21st to end	Night	20% 15% 31% 25% 9% 1	693
April	1st to 10th	Night	24% 13% 36% 21% 6%	630
	11th to 20th	Night	27% 11% 28% 26% 7%	623
	21st to end	Night	24% 11% 32% 24% 8% 1	630
May	1st to 10th	Night	19% 14% 33% 27% 7% 1	630
	11th to 20th	Night	19% 10% 35% 28% 7% 1	621
	21st to end	Night	16% 11% 31% 33% 10%	683
June	1st to 10th	Night	15% 8% 33% 32% 11%	630
	11th to 20th	Night	19% 8% 33% 32% 8%	630
	21st to end	Night	17% 8% 28% 33% 13% 1	630
July	1st to 10th	Night	9% 5% 27% 38% 21% 1	615
	11th to 20th	Night	13% 6% 33% 30% 17% 1	597
	21st to end	Night	10% 3 27% 40% 17% 3	657
August	1st to 10th	Night	12% 5% 26% 36% 20% 1	597
	11th to 20th	Night	15% 6% 21% 35% 22% 2	594
	21st to end	Night	16% 6% 27% 29% 21% 1	660
September	1st to 10th	Night	16% 7% 26% 32% 17% 3	600
	11th to 20th	Night	15% 7% 31% 31% 15% 1	619
	21st to end	Night	20% 11% 29% 29% 11% 1	800
October	1st to 10th	Night	22% 12% 29% 24% 12% 1	800
	11th to 20th	Night	25% 16% 32% 21% 5%	800
	21st to end	Night	28% 12% 30% 22% 7%	880
November	1st to 10th	Night	25% 14% 37% 19% 4 1	820
	11th to 20th	Night	23% 22% 34% 16% 4	1010
	21st to end	Night	23% 23% 35% 16% 3	1050
December	1st to 10th	Night	19% 22% 37% 17% 5%	1050
	11th to 20th	Night	19% 22% 36% 18% 4 1	1050
	21st to end	Night	26% 18% 36% 15% 4	1155

Page generated at 2026-07-13 02:14:50. Version ac07

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