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 2025-03-12.

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% 11% 4 10% 6% 5% 5% 4 5% 6% 31%	108951
	Night	13% 12% 5% 11% 6% 5% 4 4 5% 6% 30%	110263
Transparency	Day	52% 6% 12% 20% 10% 1	112428
	Night	53% 6% 12% 20% 9% 1	114948
Seeing	Day	19% 17% 34% 20% 8% 2	16458
	Night	19% 14% 34% 24% 8% 1	26546

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% 13% 6% 20% 14% 9% 5% 3 3 4 14%	3617
	11th to 20th	Day	6% 16% 7% 15% 9% 12% 11% 6% 5% 4 10%	3589
	21st to end	Day	8% 14% 11% 18% 5% 5% 5% 3 5% 5% 19%	3982
February	1st to 10th	Day	9% 14% 5% 12% 6% 7% 7% 5% 6% 6% 24%	1796
	11th to 20th	Day	8% 12% 5% 15% 8% 4 6% 5% 6% 5% 25%	1794
	21st to end	Day	12% 13% 7% 12% 8% 7% 4 4 4 6% 23%	1650
March	1st to 10th	Day	12% 10% 3 12% 5% 5% 4 2 3 5% 37%	3218
	11th to 20th	Day	8% 13% 5% 12% 8% 5% 4 4 5% 6% 29%	3389
	21st to end	Day	19% 14% 5% 13% 5% 4 4 3 3 5% 25%	4095
April	1st to 10th	Day	15% 15% 5% 9% 6% 4 5% 4 4 5% 27%	2280
	11th to 20th	Day	19% 13% 6% 9% 5% 4 3 3 4 4 30%	2254
	21st to end	Day	18% 12% 4 7% 6% 4 4 4 5% 5% 32%	2424
May	1st to 10th	Day	18% 10% 3 6% 4 4 4 3 4 5% 39%	4428
	11th to 20th	Day	16% 8% 2 6% 4 4 4 4 6% 6% 38%	4399
	21st to end	Day	17% 9% 3 8% 5% 4 4 3 5% 6% 35%	4837
June	1st to 10th	Day	16% 6% 2 6% 4 4 4 5% 5% 8% 39%	2660
	11th to 20th	Day	15% 6% 3 7% 5% 6% 5% 4 5% 7% 37%	2660
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	2660
July	1st to 10th	Day	14% 4 2 6% 4 5% 5% 5% 6% 9% 41%	4440
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 6% 9% 50%	4440
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 8% 47%	4814
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 7% 38%	4423
	11th to 20th	Day	15% 6% 2 4 4 4 4 3 5% 7% 48%	4048
	21st to end	Day	16% 7% 2 7% 5% 4 5% 4 5% 8% 38%	4180
September	1st to 10th	Day	15% 7% 2 6% 3 4 4 4 5% 8% 42%	2280
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 5% 8% 40%	2242
	21st to end	Day	20% 9% 3 7% 4 4 4 3 5% 7% 35%	2082
October	1st to 10th	Day	19% 11% 2 6% 4 4 3 4 6% 6% 34%	1900
	11th to 20th	Day	21% 17% 4 7% 5% 4 5% 3 5% 6% 24%	1896
	21st to end	Day	21% 17% 4 8% 5% 4 3 3 4 5% 25%	1881
November	1st to 10th	Day	16% 16% 4 7% 5% 3 4 4 5% 6% 29%	1762
	11th to 20th	Day	15% 19% 6% 13% 7% 5% 4 4 5% 4 19%	1635
	21st to end	Day	14% 16% 8% 17% 8% 4 4 3 5% 5% 16%	1600
December	1st to 10th	Day	8% 18% 9% 30% 8% 5% 4 3 3 3 10%	2610
	11th to 20th	Day	9% 21% 8% 17% 10% 5% 4 2 3 3 16%	3004
	21st to end	Day	18% 23% 7% 14% 6% 5% 3 3 3 3 14%	3982
January	1st to 10th	Night	8% 14% 6% 22% 11% 7% 4 2 3 4 17%	6348
	11th to 20th	Night	7% 15% 7% 15% 9% 9% 8% 6% 6% 6% 12%	6316
	21st to end	Night	8% 16% 9% 19% 5% 6% 4 3 4 5% 21%	6996
February	1st to 10th	Night	8% 13% 7% 13% 7% 6% 6% 5% 7% 6% 24%	2600
	11th to 20th	Night	9% 10% 5% 11% 9% 7% 7% 4 6% 7% 25%	2492
	21st to end	Night	11% 17% 5% 10% 6% 5% 5% 4 6% 5% 25%	1980
March	1st to 10th	Night	10% 7% 3 9% 5% 4 5% 4 6% 8% 39%	3842
	11th to 20th	Night	8% 11% 5% 15% 6% 4 4 3 5% 5% 33%	3628
	21st to end	Night	18% 14% 5% 10% 6% 4 4 4 4 5% 27%	3535
April	1st to 10th	Night	19% 13% 3 9% 4 3 4 4 6% 6% 30%	1900
	11th to 20th	Night	22% 10% 4 7% 4 3 3 3 5% 6% 33%	1875
	21st to end	Night	18% 10% 4 6% 5% 3 4 4 5% 5% 35%	1753
May	1st to 10th	Night	18% 9% 3 6% 4 4 4 3 5% 7% 37%	2523
	11th to 20th	Night	14% 8% 3 6% 4 4 4 3 4 5% 45%	2506
	21st to end	Night	16% 8% 3 7% 4 3 4 3 5% 8% 37%	2750
June	1st to 10th	Night	12% 7% 2 6% 5% 4 4 3 5% 7% 45%	1520
	11th to 20th	Night	13% 7% 3 6% 5% 5% 5% 4 6% 7% 40%	1520
	21st to end	Night	14% 6% 2 5% 5% 4 4 3 6% 8% 43%	1520
July	1st to 10th	Night	14% 5% 2 4 3 3 3 3 6% 8% 48%	2530
	11th to 20th	Night	8% 4 2 4 3 3 4 4 5% 8% 55%	2530
	21st to end	Night	10% 5% 1 4 4 3 3 3 6% 6% 54%	2750
August	1st to 10th	Night	12% 6% 2 5% 5% 4 4 5% 7% 7% 43%	2517
	11th to 20th	Night	14% 6% 2 4 3 2 3 3 4 6% 53%	2786
	21st to end	Night	18% 8% 3 6% 4 3 2 2 4 6% 45%	3476
September	1st to 10th	Night	13% 4 2 5% 3 4 4 4 5% 8% 49%	1900
	11th to 20th	Night	13% 5% 2 5% 4 4 5% 4 5% 8% 46%	1918
	21st to end	Night	16% 7% 3 6% 5% 4 4 3 5% 7% 39%	2095
October	1st to 10th	Night	18% 8% 2 5% 4 4 3 4 5% 7% 42%	2280
	11th to 20th	Night	18% 13% 5% 6% 4 5% 5% 3 5% 6% 31%	2283
	21st to end	Night	20% 15% 4 8% 5% 5% 4 3 5% 6% 26%	2717
November	1st to 10th	Night	16% 14% 4 7% 4 4 4 3 5% 6% 32%	2536
	11th to 20th	Night	15% 17% 8% 12% 6% 4 4 3 3 5% 22%	2762
	21st to end	Night	14% 16% 6% 14% 7% 5% 5% 3 5% 6% 20%	2800
December	1st to 10th	Night	11% 15% 8% 22% 10% 5% 4 3 4 5% 13%	4580
	11th to 20th	Night	9% 18% 8% 17% 8% 5% 5% 4 4 4 17%	5203
	21st to end	Night	21% 20% 5% 13% 8% 5% 3 3 3 4 15%	6996

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	73% 4 6% 12% 4	3618
	11th to 20th	Day	74% 5% 8% 8% 4	3620
	21st to end	Day	66% 4 9% 14% 6%	3982
February	1st to 10th	Day	57% 5% 11% 16% 10%	1796
	11th to 20th	Day	57% 7% 10% 19% 7%	1803
	21st to end	Day	62% 5% 9% 14% 9% 1	1650
March	1st to 10th	Day	49% 5% 14% 17% 14% 1	3220
	11th to 20th	Day	53% 6% 14% 17% 8% 1	3389
	21st to end	Day	62% 5% 10% 16% 6%	4095
April	1st to 10th	Day	58% 6% 10% 16% 9% 1	2280
	11th to 20th	Day	57% 5% 10% 19% 9% 1	2254
	21st to end	Day	53% 7% 10% 18% 12% 1	2424
May	1st to 10th	Day	45% 7% 10% 23% 13% 1	4440
	11th to 20th	Day	42% 9% 13% 25% 10% 1	4403
	21st to end	Day	49% 6% 11% 18% 15% 1	4837
June	1st to 10th	Day	40% 8% 14% 26% 11% 1	2660
	11th to 20th	Day	45% 8% 12% 21% 14% 1	2660
	21st to end	Day	42% 9% 16% 23% 9% 1	2660
July	1st to 10th	Day	37% 7% 17% 27% 11% 1	4371
	11th to 20th	Day	29% 7% 17% 32% 13% 2	4365
	21st to end	Day	34% 7% 14% 30% 16%	4662
August	1st to 10th	Day	43% 7% 15% 22% 11% 1	4408
	11th to 20th	Day	36% 6% 16% 30% 11%	4089
	21st to end	Day	44% 6% 16% 22% 11% 1	4179
September	1st to 10th	Day	40% 6% 15% 27% 11%	2280
	11th to 20th	Day	42% 7% 19% 25% 8%	2242
	21st to end	Day	49% 6% 12% 24% 8%	2082
October	1st to 10th	Day	37% 4 15% 28% 15%	3160
	11th to 20th	Day	55% 5% 9% 19% 13%	3124
	21st to end	Day	54% 5% 17% 19% 5%	3081
November	1st to 10th	Day	56% 6% 12% 19% 8% 1	1762
	11th to 20th	Day	68% 5% 10% 11% 6%	1635
	21st to end	Day	70% 7% 11% 10% 3 1	1600
December	1st to 10th	Day	80% 4 7% 7% 2	2610
	11th to 20th	Day	74% 4 6% 9% 7%	3005
	21st to end	Day	76% 4 5% 11% 5%	3982
January	1st to 10th	Night	71% 4 8% 13% 4	6348
	11th to 20th	Night	69% 5% 10% 10% 5%	6360
	21st to end	Night	64% 5% 9% 16% 6%	6996
February	1st to 10th	Night	58% 4 10% 17% 10% 1	2600
	11th to 20th	Night	55% 7% 11% 19% 7% 1	2493
	21st to end	Night	58% 6% 11% 16% 8% 1	1980
March	1st to 10th	Night	39% 7% 18% 22% 13% 1	3853
	11th to 20th	Night	50% 7% 11% 24% 8% 1	3629
	21st to end	Night	59% 6% 10% 16% 8% 1	3535
April	1st to 10th	Night	54% 6% 9% 18% 12% 1	1900
	11th to 20th	Night	51% 4 10% 21% 11% 2	1875
	21st to end	Night	49% 5% 11% 19% 14% 1	1753
May	1st to 10th	Night	45% 7% 15% 20% 12% 1	2530
	11th to 20th	Night	40% 7% 11% 24% 15% 3	2507
	21st to end	Night	45% 7% 16% 17% 14% 1	2751
June	1st to 10th	Night	37% 8% 16% 27% 12%	1520
	11th to 20th	Night	42% 7% 13% 21% 16% 1	1520
	21st to end	Night	38% 9% 15% 27% 10% 1	1520
July	1st to 10th	Night	34% 7% 18% 27% 12% 3	2490
	11th to 20th	Night	26% 6% 17% 37% 13% 1	2482
	21st to end	Night	29% 8% 13% 30% 18% 2	2662
August	1st to 10th	Night	38% 7% 15% 24% 15% 1	2508
	11th to 20th	Night	33% 7% 16% 31% 13% 1	2811
	21st to end	Night	42% 5% 14% 24% 12% 2	3476
September	1st to 10th	Night	33% 7% 14% 32% 13% 1	1900
	11th to 20th	Night	35% 7% 17% 33% 8%	1918
	21st to end	Night	44% 6% 14% 25% 9% 1	2095
October	1st to 10th	Night	33% 5% 8% 33% 19% 1	3800
	11th to 20th	Night	44% 5% 12% 27% 12%	3794
	21st to end	Night	57% 5% 11% 19% 7%	4467
November	1st to 10th	Night	52% 5% 14% 20% 9%	2536
	11th to 20th	Night	64% 5% 12% 12% 7% 1	2762
	21st to end	Night	65% 6% 12% 13% 3 1	2800
December	1st to 10th	Night	74% 5% 10% 10% 2	4580
	11th to 20th	Night	69% 5% 9% 11% 6%	5201
	21st to end	Night	73% 4 6% 11% 6%	6996

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	17% 18% 36% 21% 6% 2	300
	11th to 20th	Day	25% 15% 35% 24% 2	300
	21st to end	Day	18% 18% 42% 19% 2	330
February	1st to 10th	Day	20% 23% 41% 11% 4 1	300
	11th to 20th	Day	14% 30% 40% 13% 3 1	300
	21st to end	Day	20% 28% 44% 7%	249
March	1st to 10th	Day	19% 26% 37% 16% 2	300
	11th to 20th	Day	19% 21% 40% 16% 5%	273
	21st to end	Day	23% 19% 35% 16% 5% 2	462
April	1st to 10th	Day	24% 18% 37% 15% 5%	460
	11th to 20th	Day	31% 17% 28% 18% 6% 1	452
	21st to end	Day	23% 19% 31% 19% 6% 2	488
May	1st to 10th	Day	21% 22% 34% 16% 5% 2	653
	11th to 20th	Day	21% 17% 33% 20% 6% 3	675
	21st to end	Day	22% 13% 34% 19% 9% 2	734
June	1st to 10th	Day	16% 17% 33% 23% 9% 3	680
	11th to 20th	Day	19% 14% 38% 18% 9% 1	680
	21st to end	Day	15% 18% 34% 20% 11% 3	680
July	1st to 10th	Day	9% 10% 34% 28% 13% 6%	671
	11th to 20th	Day	13% 10% 34% 24% 14% 5%	668
	21st to end	Day	9% 9% 37% 24% 14% 7%	739
August	1st to 10th	Day	14% 10% 29% 29% 15% 3	676
	11th to 20th	Day	15% 9% 23% 31% 16% 4	627
	21st to end	Day	19% 11% 27% 24% 15% 4	539
September	1st to 10th	Day	18% 15% 24% 26% 12% 4	490
	11th to 20th	Day	16% 9% 34% 28% 11% 2	490
	21st to end	Day	24% 17% 25% 22% 9% 4	482
October	1st to 10th	Day	23% 20% 29% 19% 8% 1	300
	11th to 20th	Day	25% 29% 30% 13% 4	300
	21st to end	Day	33% 24% 33% 9% 1	330
November	1st to 10th	Day	26% 18% 37% 14% 5%	300
	11th to 20th	Day	25% 26% 37% 9% 2 1	300
	21st to end	Day	21% 24% 42% 10% 4	300
December	1st to 10th	Day	18% 19% 43% 15% 5%	300
	11th to 20th	Day	23% 25% 35% 15% 2	300
	21st to end	Day	23% 26% 36% 12% 2 1	330
January	1st to 10th	Night	16% 18% 42% 19% 5% 1	1000
	11th to 20th	Night	18% 17% 42% 17% 6% 1	1000
	21st to end	Night	19% 14% 40% 21% 5%	1100
February	1st to 10th	Night	17% 17% 40% 21% 6%	1000
	11th to 20th	Night	15% 20% 39% 20% 5% 1	938
	21st to end	Night	20% 16% 40% 21% 3	660
March	1st to 10th	Night	17% 16% 37% 24% 6% 1	800
	11th to 20th	Night	19% 15% 39% 20% 6%	655
	21st to end	Night	20% 14% 30% 26% 9% 1	627
April	1st to 10th	Night	23% 12% 38% 21% 6%	570
	11th to 20th	Night	27% 12% 29% 26% 7%	563
	21st to end	Night	24% 12% 31% 24% 8% 1	570
May	1st to 10th	Night	21% 14% 32% 26% 6% 1	570
	11th to 20th	Night	19% 9% 35% 28% 7% 2	561
	21st to end	Night	16% 12% 30% 32% 10%	617
June	1st to 10th	Night	16% 8% 33% 31% 11% 1	570
	11th to 20th	Night	17% 9% 33% 32% 8%	570
	21st to end	Night	16% 8% 28% 33% 14% 1	570
July	1st to 10th	Night	9% 5% 27% 37% 21% 1	555
	11th to 20th	Night	13% 7% 32% 31% 17% 1	552
	21st to end	Night	10% 3 27% 40% 17% 3	624
August	1st to 10th	Night	12% 5% 27% 37% 19% 1	567
	11th to 20th	Night	16% 6% 20% 35% 22% 2	564
	21st to end	Night	16% 6% 28% 28% 20% 1	627
September	1st to 10th	Night	14% 7% 26% 33% 16% 3	570
	11th to 20th	Night	14% 8% 32% 30% 15% 1	588
	21st to end	Night	21% 11% 29% 28% 11% 1	760
October	1st to 10th	Night	23% 12% 28% 24% 12% 1	760
	11th to 20th	Night	25% 17% 32% 21% 5%	760
	21st to end	Night	29% 13% 30% 22% 6%	836
November	1st to 10th	Night	25% 14% 38% 18% 5% 1	780
	11th to 20th	Night	24% 22% 35% 16% 4 1	962
	21st to end	Night	23% 23% 35% 16% 3	1000
December	1st to 10th	Night	19% 22% 36% 17% 5% 1	1000
	11th to 20th	Night	19% 21% 37% 19% 5% 1	1000
	21st to end	Night	26% 18% 36% 15% 4	1100

Page generated at 2025-03-09 07:08:42. Version ac07

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