Carp Library / Diefenbunker
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carp Library / Diefenbunker clear sky chart from 2005-11-06 to 2025-10-04.

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	16% 10% 3 8% 5% 5% 5% 4 5% 7% 32%	126868
	Night	16% 11% 4 9% 5% 5% 4 4 5% 6% 30%	122509
Transparency	Day	51% 4 11% 22% 10% 1	130346
	Night	54% 4 11% 20% 10% 1	127118
Seeing	Day	23% 13% 30% 21% 10% 3	15617
	Night	23% 11% 28% 28% 10% 1	24663

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	14% 16% 5% 14% 8% 6% 5% 3 4 5% 20%	3597
	11th to 20th	Day	12% 15% 6% 14% 7% 6% 5% 4 5% 6% 21%	3570
	21st to end	Day	10% 17% 7% 14% 7% 6% 5% 3 5% 5% 20%	4167
February	1st to 10th	Day	14% 15% 4 12% 7% 6% 4 4 6% 5% 24%	1800
	11th to 20th	Day	12% 14% 5% 10% 6% 5% 4 4 5% 5% 28%	1753
	21st to end	Day	18% 12% 4 9% 6% 4 6% 4 5% 5% 26%	1644
March	1st to 10th	Day	19% 13% 4 11% 7% 5% 4 3 4 5% 25%	4514
	11th to 20th	Day	11% 12% 4 9% 6% 6% 5% 4 6% 8% 29%	4980
	21st to end	Day	17% 12% 3 8% 5% 4 4 3 4 4 38%	5740
April	1st to 10th	Day	22% 11% 3 7% 5% 4 4 3 4 5% 33%	2400
	11th to 20th	Day	22% 9% 2 7% 5% 4 3 3 4 4 36%	2374
	21st to end	Day	22% 10% 3 7% 5% 3 5% 4 4 5% 32%	2540
May	1st to 10th	Day	23% 10% 3 8% 5% 4 5% 4 5% 6% 27%	6346
	11th to 20th	Day	15% 10% 3 8% 6% 5% 5% 4 6% 7% 31%	6318
	21st to end	Day	20% 8% 3 7% 5% 4 4 4 5% 6% 34%	6949
June	1st to 10th	Day	19% 9% 3 7% 5% 5% 5% 4 5% 7% 31%	2800
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 5% 6% 8% 40%	2800
	21st to end	Day	17% 7% 3 6% 5% 5% 5% 5% 6% 7% 33%	2800
July	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 5% 7% 9% 34%	6360
	11th to 20th	Day	10% 5% 2 7% 4 4 5% 4 7% 8% 44%	6360
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 46%	6926
August	1st to 10th	Day	14% 6% 3 7% 5% 5% 6% 4 6% 8% 38%	4467
	11th to 20th	Day	16% 6% 2 7% 4 4 5% 4 6% 8% 38%	4143
	21st to end	Day	12% 6% 2 6% 4 5% 5% 4 7% 10% 40%	4312
September	1st to 10th	Day	12% 6% 3 6% 5% 4 5% 4 5% 8% 43%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 4 3 6% 8% 47%	2400
	21st to end	Day	16% 7% 2 6% 4 5% 4 4 6% 7% 39%	2128
October	1st to 10th	Day	19% 7% 3 7% 4 5% 4 3 6% 7% 35%	1930
	11th to 20th	Day	21% 8% 3 7% 5% 5% 5% 3 5% 7% 30%	1900
	21st to end	Day	24% 10% 3 7% 5% 4 5% 3 4 7% 28%	1948
November	1st to 10th	Day	15% 8% 3 7% 6% 6% 5% 5% 6% 7% 33%	1756
	11th to 20th	Day	18% 12% 3 8% 5% 6% 5% 4 5% 6% 28%	1600
	21st to end	Day	21% 13% 4 10% 6% 6% 6% 4 5% 5% 20%	1600
December	1st to 10th	Day	20% 21% 5% 11% 6% 5% 5% 4 5% 5% 14%	2600
	11th to 20th	Day	17% 15% 5% 12% 6% 5% 5% 4 4 5% 23%	2986
	21st to end	Day	22% 15% 6% 13% 6% 4 5% 3 3 4 20%	3960
January	1st to 10th	Night	13% 19% 8% 16% 6% 4 4 3 3 5% 19%	6349
	11th to 20th	Night	11% 14% 6% 14% 8% 7% 5% 4 5% 5% 21%	6315
	21st to end	Night	13% 18% 7% 11% 7% 6% 5% 3 5% 5% 21%	6786
February	1st to 10th	Night	13% 15% 4 12% 8% 5% 6% 4 5% 6% 23%	2600
	11th to 20th	Night	13% 13% 5% 12% 8% 5% 3 4 4 5% 29%	2533
	21st to end	Night	16% 12% 4 9% 6% 5% 5% 3 6% 6% 28%	1985
March	1st to 10th	Night	21% 14% 4 10% 5% 4 4 3 3 4 28%	5323
	11th to 20th	Night	12% 12% 4 9% 5% 5% 5% 4 6% 8% 30%	4979
	21st to end	Night	18% 9% 3 9% 5% 4 4 3 5% 6% 34%	5192
April	1st to 10th	Night	20% 10% 3 8% 5% 4 4 3 4 6% 32%	2000
	11th to 20th	Night	19% 10% 2 8% 4 3 4 3 5% 6% 35%	1975
	21st to end	Night	20% 9% 3 8% 5% 5% 3 3 4 6% 34%	1874
May	1st to 10th	Night	23% 8% 3 7% 5% 5% 5% 5% 6% 7% 25%	3594
	11th to 20th	Night	15% 7% 3 7% 4 5% 4 4 5% 7% 39%	3575
	21st to end	Night	17% 8% 3 8% 4 5% 5% 4 6% 7% 32%	3926
June	1st to 10th	Night	14% 7% 2 8% 6% 5% 5% 5% 7% 8% 34%	1600
	11th to 20th	Night	14% 6% 2 7% 4 4 4 3 6% 8% 43%	1600
	21st to end	Night	18% 8% 2 5% 5% 4 4 4 6% 7% 37%	1600
July	1st to 10th	Night	13% 7% 3 8% 5% 6% 5% 4 6% 9% 33%	3600
	11th to 20th	Night	12% 5% 2 6% 5% 4 5% 4 6% 8% 43%	3600
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 6% 8% 46%	3926
August	1st to 10th	Night	10% 6% 3 8% 4 5% 5% 4 6% 9% 40%	2679
	11th to 20th	Night	12% 7% 3 7% 4 4 5% 4 6% 8% 42%	2875
	21st to end	Night	12% 6% 3 7% 5% 4 5% 4 6% 8% 40%	3583
September	1st to 10th	Night	10% 5% 2 6% 5% 4 5% 4 5% 6% 48%	2000
	11th to 20th	Night	13% 4 2 5% 3 4 4 3 5% 7% 50%	2000
	21st to end	Night	17% 6% 2 6% 5% 3 3 4 5% 6% 43%	2269
October	1st to 10th	Night	16% 7% 3 6% 5% 4 5% 3 6% 6% 38%	2317
	11th to 20th	Night	20% 9% 4 7% 5% 5% 5% 3 5% 6% 31%	2280
	21st to end	Night	22% 10% 3 7% 4 5% 5% 4 4 6% 28%	2649
November	1st to 10th	Night	19% 11% 3 7% 5% 4 4 3 5% 6% 34%	2541
	11th to 20th	Night	18% 11% 3 8% 5% 5% 5% 4 5% 6% 30%	2800
	21st to end	Night	21% 13% 4 10% 5% 5% 5% 3 5% 7% 22%	2800
December	1st to 10th	Night	19% 17% 4 12% 7% 6% 5% 4 5% 6% 15%	4580
	11th to 20th	Night	22% 14% 4 10% 6% 5% 4 3 4 5% 24%	5208
	21st to end	Night	26% 17% 3 10% 4 4 4 3 4 4 20%	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	68% 2 10% 14% 5% 1	3598
	11th to 20th	Day	65% 3 10% 14% 8%	3600
	21st to end	Day	66% 3 10% 13% 8% 1	4167
February	1st to 10th	Day	61% 3 9% 20% 5% 2	1800
	11th to 20th	Day	58% 3 11% 18% 9% 1	1762
	21st to end	Day	60% 3 10% 15% 11% 1	1644
March	1st to 10th	Day	61% 3 8% 14% 12% 2	4517
	11th to 20th	Day	53% 4 15% 16% 10% 1	4980
	21st to end	Day	51% 2 5% 20% 19% 3	5740
April	1st to 10th	Day	54% 2 6% 21% 14% 3	2400
	11th to 20th	Day	53% 2 6% 22% 17% 2	2374
	21st to end	Day	56% 2 7% 16% 15% 4	2540
May	1st to 10th	Day	57% 3 7% 21% 10% 2	6357
	11th to 20th	Day	53% 4 11% 20% 11% 1	6322
	21st to end	Day	52% 3 11% 22% 12% 1	6949
June	1st to 10th	Day	53% 3 9% 21% 13% 1	2800
	11th to 20th	Day	41% 4 12% 27% 13% 2	2800
	21st to end	Day	49% 4 13% 23% 11% 1	2800
July	1st to 10th	Day	43% 7% 14% 27% 10%	6290
	11th to 20th	Day	35% 6% 13% 32% 14%	6285
	21st to end	Day	32% 5% 15% 37% 11%	6728
August	1st to 10th	Day	44% 5% 17% 25% 10%	4453
	11th to 20th	Day	42% 5% 14% 29% 9%	4182
	21st to end	Day	39% 5% 15% 28% 12% 1	4312
September	1st to 10th	Day	40% 3 14% 31% 11%	2400
	11th to 20th	Day	35% 4 13% 34% 13% 1	2400
	21st to end	Day	44% 4 14% 27% 11%	2128
October	1st to 10th	Day	46% 5% 12% 29% 7% 1	3190
	11th to 20th	Day	46% 5% 14% 26% 9%	3140
	21st to end	Day	49% 5% 18% 21% 7%	3186
November	1st to 10th	Day	49% 3 14% 26% 7% 1	1756
	11th to 20th	Day	57% 4 12% 17% 9% 1	1600
	21st to end	Day	66% 4 12% 11% 7% 1	1600
December	1st to 10th	Day	71% 5% 11% 10% 2	2600
	11th to 20th	Day	64% 4 10% 15% 8%	2986
	21st to end	Day	69% 3 8% 17% 4	3960
January	1st to 10th	Night	70% 2 11% 13% 4	6349
	11th to 20th	Night	66% 3 10% 15% 6%	6360
	21st to end	Night	66% 3 8% 11% 10% 1	6786
February	1st to 10th	Night	62% 3 9% 18% 7% 1	2600
	11th to 20th	Night	59% 2 10% 20% 8% 1	2535
	21st to end	Night	57% 3 9% 21% 10% 1	1985
March	1st to 10th	Night	62% 1 6% 16% 12% 2	5333
	11th to 20th	Night	52% 4 16% 17% 8% 3	4980
	21st to end	Night	52% 3 7% 21% 14% 3	5192
April	1st to 10th	Night	54% 3 7% 19% 15% 2	2000
	11th to 20th	Night	51% 3 6% 22% 17% 1	1975
	21st to end	Night	53% 3 7% 17% 16% 3	1874
May	1st to 10th	Night	58% 3 8% 21% 8% 3	3600
	11th to 20th	Night	46% 3 13% 22% 15% 1	3576
	21st to end	Night	51% 4 12% 18% 14% 1	3927
June	1st to 10th	Night	47% 4 12% 25% 11% 2	1600
	11th to 20th	Night	40% 3 11% 26% 17% 2	1600
	21st to end	Night	45% 5% 12% 23% 14% 1	1600
July	1st to 10th	Night	45% 7% 15% 20% 12% 1	3560
	11th to 20th	Night	37% 7% 13% 32% 12%	3552
	21st to end	Night	35% 6% 12% 32% 15%	3809
August	1st to 10th	Night	41% 6% 15% 26% 12% 1	2669
	11th to 20th	Night	39% 5% 17% 30% 9%	2902
	21st to end	Night	39% 6% 14% 26% 12% 2	3583
September	1st to 10th	Night	37% 4 12% 32% 15% 1	2000
	11th to 20th	Night	34% 3 13% 37% 11% 1	2000
	21st to end	Night	42% 3 11% 31% 13%	2269
October	1st to 10th	Night	40% 5% 12% 31% 12%	3837
	11th to 20th	Night	47% 4 15% 25% 9%	3779
	21st to end	Night	49% 5% 17% 20% 8%	4361
November	1st to 10th	Night	52% 3 13% 22% 9% 1	2541
	11th to 20th	Night	56% 3 10% 20% 10% 1	2800
	21st to end	Night	61% 4 12% 16% 6%	2800
December	1st to 10th	Night	69% 5% 12% 12% 3	4580
	11th to 20th	Night	64% 3 7% 15% 10% 1	5208
	21st to end	Night	69% 2 6% 13% 9%	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	22% 21% 37% 16% 4 1	200
	11th to 20th	Day	28% 15% 35% 19% 3 1	200
	21st to end	Day	18% 18% 38% 21% 4	265
February	1st to 10th	Day	30% 20% 33% 14% 3	300
	11th to 20th	Day	29% 26% 36% 8% 1	300
	21st to end	Day	32% 19% 32% 14% 2	408
March	1st to 10th	Day	28% 17% 32% 19% 3 1	500
	11th to 20th	Day	27% 18% 33% 18% 3 1	500
	21st to end	Day	33% 17% 28% 15% 6% 1	550
April	1st to 10th	Day	34% 18% 27% 15% 5% 1	500
	11th to 20th	Day	35% 14% 25% 13% 10% 2	492
	21st to end	Day	31% 17% 31% 13% 6% 1	500
May	1st to 10th	Day	25% 14% 33% 19% 7% 2	503
	11th to 20th	Day	19% 15% 32% 22% 9% 3	527
	21st to end	Day	21% 13% 31% 22% 12% 1	573
June	1st to 10th	Day	25% 10% 31% 23% 9% 2	530
	11th to 20th	Day	15% 13% 32% 25% 12% 3	530
	21st to end	Day	22% 11% 31% 24% 10% 3	530
July	1st to 10th	Day	13% 6% 29% 33% 16% 3	525
	11th to 20th	Day	12% 7% 32% 30% 15% 5%	524
	21st to end	Day	13% 7% 32% 29% 15% 4	576
August	1st to 10th	Day	13% 5% 25% 33% 18% 5%	526
	11th to 20th	Day	15% 4 24% 30% 18% 8%	519
	21st to end	Day	17% 9% 27% 24% 15% 8%	583
September	1st to 10th	Day	16% 10% 27% 21% 17% 9%	530
	11th to 20th	Day	12% 6% 23% 25% 22% 13%	530
	21st to end	Day	18% 10% 31% 22% 15% 5%	530
October	1st to 10th	Day	23% 12% 25% 22% 14% 5%	502
	11th to 20th	Day	28% 16% 27% 19% 8% 2	490
	21st to end	Day	31% 14% 26% 22% 6%	464
November	1st to 10th	Day	28% 14% 30% 19% 8% 1	390
	11th to 20th	Day	29% 19% 32% 14% 6% 2	200
	21st to end	Day	31% 18% 35% 11% 5% 1	200
December	1st to 10th	Day	33% 13% 36% 16% 4	200
	11th to 20th	Day	33% 22% 33% 9% 4	200
	21st to end	Day	27% 20% 35% 13% 4 1	220
January	1st to 10th	Night	27% 13% 35% 20% 5%	800
	11th to 20th	Night	28% 16% 27% 22% 7% 1	800
	21st to end	Night	20% 11% 36% 27% 6%	880
February	1st to 10th	Night	22% 15% 35% 24% 4	800
	11th to 20th	Night	22% 16% 38% 21% 4	783
	21st to end	Night	26% 16% 28% 26% 4	660
March	1st to 10th	Night	25% 13% 33% 26% 4	800
	11th to 20th	Night	24% 16% 32% 22% 6%	800
	21st to end	Night	25% 15% 27% 25% 7%	880
April	1st to 10th	Night	27% 13% 29% 25% 6%	800
	11th to 20th	Night	26% 15% 28% 23% 8%	791
	21st to end	Night	26% 10% 30% 26% 8%	674
May	1st to 10th	Night	24% 7% 26% 33% 10% 1	400
	11th to 20th	Night	22% 8% 30% 31% 9% 1	394
	21st to end	Night	16% 5% 36% 29% 13%	433
June	1st to 10th	Night	17% 4 31% 37% 11%	400
	11th to 20th	Night	17% 6% 26% 36% 14% 1	400
	21st to end	Night	21% 4 27% 34% 13% 1	400
July	1st to 10th	Night	10% 4 28% 41% 16% 1	390
	11th to 20th	Night	13% 3 22% 46% 14% 1	388
	21st to end	Night	11% 4 23% 45% 16% 2	438
August	1st to 10th	Night	11% 3 19% 44% 22%	452
	11th to 20th	Night	12% 3 16% 40% 27% 3	594
	21st to end	Night	13% 5% 23% 38% 19% 2	877
September	1st to 10th	Night	14% 5% 28% 32% 20% 2	800
	11th to 20th	Night	16% 4 20% 33% 23% 5%	800
	21st to end	Night	20% 6% 24% 29% 20% 2	800
October	1st to 10th	Night	22% 8% 23% 29% 16% 2	773
	11th to 20th	Night	27% 10% 27% 27% 8% 1	760
	21st to end	Night	28% 12% 27% 26% 6%	836
November	1st to 10th	Night	27% 12% 25% 27% 8% 1	780
	11th to 20th	Night	25% 14% 33% 18% 9% 1	800
	21st to end	Night	31% 14% 26% 23% 7%	800
December	1st to 10th	Night	30% 13% 30% 22% 5%	800
	11th to 20th	Night	28% 15% 28% 23% 5% 1	800
	21st to end	Night	35% 13% 28% 20% 5%	880

Page generated at 2025-10-01 01:39:02. Version ac07

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