Caledonia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caledonia clear sky chart from 2005-11-06 to 2024-01-16.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 37%	74821
	Night	14% 9% 4 6% 5% 3 4 4 5% 7% 39%	75015
Transparency	Day	46% 7% 13% 22% 12% 1	74522
	Night	45% 6% 12% 22% 14% 2	74835
Seeing	Day	16% 10% 29% 25% 14% 5%	14690
	Night	18% 9% 31% 30% 12% 1	24679

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	13% 11% 6% 9% 7% 4 5% 5% 6% 6% 28%	1517
	11th to 20th	Day	13% 14% 8% 12% 6% 3 4 6% 5% 6% 23%	1485
	21st to end	Day	14% 15% 6% 13% 7% 3 5% 5% 5% 5% 22%	1656
February	1st to 10th	Day	13% 13% 6% 8% 6% 4 6% 5% 5% 6% 27%	1620
	11th to 20th	Day	15% 10% 3 7% 8% 4 4 4 5% 6% 35%	1727
	21st to end	Day	14% 13% 5% 10% 6% 3 4 4 5% 6% 31%	1480
March	1st to 10th	Day	14% 11% 5% 7% 7% 3 4 5% 4 6% 33%	1800
	11th to 20th	Day	13% 8% 4 6% 6% 3 4 4 5% 8% 39%	1880
	21st to end	Day	20% 11% 4 7% 7% 4 5% 5% 5% 6% 26%	2366
April	1st to 10th	Day	18% 10% 5% 8% 6% 4 4 5% 4 6% 31%	2160
	11th to 20th	Day	16% 10% 4 5% 6% 3 5% 6% 5% 7% 33%	2134
	21st to end	Day	19% 9% 3 7% 6% 3 4 4 5% 7% 32%	2228
May	1st to 10th	Day	17% 9% 4 8% 6% 3 5% 5% 6% 7% 30%	2357
	11th to 20th	Day	19% 9% 3 5% 5% 3 5% 5% 6% 6% 35%	2479
	21st to end	Day	14% 7% 3 6% 6% 3 5% 6% 6% 7% 37%	2725
June	1st to 10th	Day	10% 5% 2 5% 6% 3 4 5% 5% 9% 44%	2520
	11th to 20th	Day	10% 6% 2 4 4 3 5% 5% 7% 10% 44%	2520
	21st to end	Day	12% 6% 2 6% 5% 3 5% 6% 7% 10% 37%	2520
July	1st to 10th	Day	8% 5% 2 5% 5% 3 5% 5% 7% 10% 46%	2520
	11th to 20th	Day	9% 4 2 5% 4 4 5% 5% 7% 11% 44%	2520
	21st to end	Day	7% 6% 2 5% 6% 3 5% 6% 6% 10% 45%	2743
August	1st to 10th	Day	8% 5% 2 4 5% 3 5% 6% 8% 10% 43%	2483
	11th to 20th	Day	10% 5% 3 5% 6% 3 5% 5% 7% 8% 44%	2134
	21st to end	Day	10% 5% 2 4 5% 3 4 5% 6% 7% 49%	2376
September	1st to 10th	Day	13% 6% 2 5% 5% 3 4 4 5% 9% 46%	2160
	11th to 20th	Day	14% 4 2 4 4 3 4 4 5% 7% 51%	2080
	21st to end	Day	12% 6% 3 6% 5% 3 4 4 6% 7% 43%	1980
October	1st to 10th	Day	14% 7% 3 4 5% 3 4 4 5% 6% 46%	1877
	11th to 20th	Day	21% 9% 4 6% 5% 3 4 5% 5% 7% 34%	1800
	21st to end	Day	20% 10% 4 5% 5% 3 4 3 4 5% 37%	1800
November	1st to 10th	Day	13% 7% 4 6% 4 3 4 5% 4 6% 45%	1672
	11th to 20th	Day	15% 11% 5% 8% 7% 3 4 5% 5% 6% 32%	1710
	21st to end	Day	17% 12% 4 7% 6% 2 3 3 4 5% 36%	1571
December	1st to 10th	Day	15% 13% 4 8% 7% 3 5% 5% 4 5% 30%	1520
	11th to 20th	Day	13% 12% 6% 9% 7% 3 5% 5% 5% 6% 28%	1918
	21st to end	Day	20% 19% 10% 12% 7% 3 4 3 3 3 15%	2783
January	1st to 10th	Night	13% 12% 5% 8% 7% 3 4 3 4 5% 35%	2648
	11th to 20th	Night	15% 15% 6% 11% 7% 3 4 4 5% 5% 26%	2603
	21st to end	Night	14% 12% 6% 11% 7% 3 5% 5% 5% 7% 25%	2696
February	1st to 10th	Night	14% 15% 5% 7% 7% 4 4 3 4 5% 31%	2340
	11th to 20th	Night	14% 10% 5% 6% 6% 4 5% 4 5% 6% 37%	2117
	21st to end	Night	17% 12% 5% 7% 4 3 3 4 5% 6% 34%	1776
March	1st to 10th	Night	17% 9% 4 6% 5% 3 4 5% 5% 7% 35%	2160
	11th to 20th	Night	12% 8% 3 5% 5% 3 6% 4 5% 7% 41%	2094
	21st to end	Night	21% 10% 5% 6% 6% 3 4 4 3 7% 32%	1990
April	1st to 10th	Night	17% 10% 4 5% 5% 3 5% 5% 4 6% 38%	1800
	11th to 20th	Night	19% 9% 4 5% 6% 3 4 3 4 5% 39%	1775
	21st to end	Night	18% 8% 3 5% 5% 4 4 4 6% 7% 37%	1730
May	1st to 10th	Night	15% 7% 3 6% 5% 4 5% 6% 5% 8% 36%	1600
	11th to 20th	Night	16% 6% 4 6% 4 4 4 5% 5% 8% 38%	1416
	21st to end	Night	12% 7% 2 6% 5% 3 4 4 8% 9% 40%	1551
June	1st to 10th	Night	8% 4 2 4 6% 3 7% 6% 5% 8% 48%	1440
	11th to 20th	Night	10% 6% 2 4 4 3 5% 5% 5% 10% 46%	1440
	21st to end	Night	8% 6% 4 5% 6% 4 4 5% 5% 9% 46%	1440
July	1st to 10th	Night	6% 4 2 5% 3 3 5% 6% 6% 10% 51%	1440
	11th to 20th	Night	7% 4 2 3 4 2 4 5% 6% 8% 53%	1440
	21st to end	Night	6% 4 2 3 4 3 5% 6% 7% 8% 51%	1575
August	1st to 10th	Night	4 4 2 4 5% 4 5% 5% 6% 11% 51%	1453
	11th to 20th	Night	8% 4 2 4 4 3 4 4 6% 8% 55%	1766
	21st to end	Night	8% 4 2 4 4 3 4 4 6% 8% 53%	1980
September	1st to 10th	Night	9% 6% 2 6% 4 2 3 3 5% 5% 54%	1800
	11th to 20th	Night	12% 4 1 4 4 3 4 3 5% 6% 54%	1862
	21st to end	Night	11% 5% 2 5% 5% 2 4 4 5% 6% 49%	1980
October	1st to 10th	Night	12% 6% 2 6% 4 3 4 4 4 6% 50%	2081
	11th to 20th	Night	18% 7% 3 6% 4 2 4 3 4 7% 43%	2160
	21st to end	Night	20% 8% 3 5% 4 3 4 4 4 6% 38%	2556
November	1st to 10th	Night	12% 7% 3 6% 4 2 4 3 5% 6% 49%	2406
	11th to 20th	Night	15% 10% 4 7% 6% 3 4 5% 5% 6% 36%	2470
	21st to end	Night	18% 10% 4 6% 6% 2 4 4 4 5% 38%	2607
December	1st to 10th	Night	15% 12% 4 9% 6% 3 5% 5% 5% 7% 30%	2660
	11th to 20th	Night	15% 13% 4 8% 6% 4 4 4 5% 6% 31%	3279
	21st to end	Night	22% 16% 7% 9% 5% 3 5% 5% 5% 5% 17%	4884

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	55% 7% 13% 16% 9%	1518
	11th to 20th	Day	62% 6% 12% 15% 6%	1485
	21st to end	Day	62% 6% 11% 13% 8%	1656
February	1st to 10th	Day	57% 6% 13% 15% 8% 1	1620
	11th to 20th	Day	51% 5% 11% 22% 10% 1	1737
	21st to end	Day	56% 6% 8% 20% 10% 1	1480
March	1st to 10th	Day	51% 7% 14% 20% 8% 1	1800
	11th to 20th	Day	46% 5% 13% 23% 12% 1	1880
	21st to end	Day	58% 7% 11% 17% 6% 1	2366
April	1st to 10th	Day	54% 6% 11% 20% 9%	2160
	11th to 20th	Day	49% 7% 10% 21% 11% 2	2134
	21st to end	Day	52% 7% 12% 17% 12% 1	2228
May	1st to 10th	Day	52% 7% 13% 21% 6%	2357
	11th to 20th	Day	48% 8% 12% 21% 11%	2483
	21st to end	Day	45% 8% 12% 19% 14% 2	2725
June	1st to 10th	Day	36% 8% 13% 27% 15% 1	2520
	11th to 20th	Day	34% 8% 13% 24% 19% 2	2520
	21st to end	Day	39% 9% 15% 22% 13% 2	2520
July	1st to 10th	Day	31% 8% 15% 30% 13% 3	2451
	11th to 20th	Day	32% 8% 17% 25% 16% 2	2445
	21st to end	Day	33% 8% 16% 25% 15% 3	2591
August	1st to 10th	Day	32% 10% 17% 28% 11% 1	2468
	11th to 20th	Day	35% 8% 15% 27% 13% 1	2134
	21st to end	Day	32% 8% 12% 26% 19% 3	2376
September	1st to 10th	Day	36% 8% 10% 26% 18% 2	2160
	11th to 20th	Day	32% 5% 12% 31% 17% 2	2080
	21st to end	Day	39% 5% 10% 29% 16% 1	1980
October	1st to 10th	Day	39% 6% 11% 28% 16% 1	1877
	11th to 20th	Day	50% 5% 12% 20% 12% 1	1800
	21st to end	Day	50% 5% 10% 22% 11% 2	1800
November	1st to 10th	Day	40% 6% 14% 23% 15% 1	1672
	11th to 20th	Day	53% 5% 12% 20% 9% 1	1710
	21st to end	Day	51% 4 14% 22% 8%	1571
December	1st to 10th	Day	56% 6% 14% 16% 8% 1	1520
	11th to 20th	Day	56% 5% 15% 16% 7% 2	1915
	21st to end	Day	75% 5% 7% 8% 4	2783
January	1st to 10th	Night	52% 5% 10% 20% 11% 1	2648
	11th to 20th	Night	60% 6% 11% 13% 9%	2603
	21st to end	Night	59% 6% 11% 14% 9% 1	2696
February	1st to 10th	Night	56% 4 10% 17% 11% 1	2340
	11th to 20th	Night	49% 5% 12% 21% 13% 1	2118
	21st to end	Night	51% 5% 10% 19% 11% 4	1776
March	1st to 10th	Night	49% 6% 14% 20% 9% 2	2160
	11th to 20th	Night	42% 6% 12% 21% 16% 2	2094
	21st to end	Night	54% 6% 9% 18% 11% 1	1990
April	1st to 10th	Night	47% 6% 11% 21% 14% 2	1800
	11th to 20th	Night	48% 5% 5% 21% 17% 4	1775
	21st to end	Night	45% 7% 12% 22% 12% 2	1730
May	1st to 10th	Night	45% 9% 12% 22% 12%	1600
	11th to 20th	Night	43% 8% 12% 22% 14% 2	1417
	21st to end	Night	39% 8% 14% 21% 16% 2	1552
June	1st to 10th	Night	31% 9% 14% 25% 19% 2	1440
	11th to 20th	Night	34% 7% 10% 23% 23% 3	1440
	21st to end	Night	36% 7% 14% 22% 18% 2	1440
July	1st to 10th	Night	28% 8% 15% 29% 17% 4	1400
	11th to 20th	Night	28% 6% 15% 29% 20% 2	1392
	21st to end	Night	26% 9% 16% 27% 18% 5%	1487
August	1st to 10th	Night	27% 9% 16% 30% 15% 3	1444
	11th to 20th	Night	26% 8% 15% 30% 20% 1	1766
	21st to end	Night	28% 7% 12% 27% 21% 4	1980
September	1st to 10th	Night	32% 6% 11% 25% 23% 3	1800
	11th to 20th	Night	31% 6% 10% 31% 20% 2	1862
	21st to end	Night	35% 7% 10% 30% 17% 2	1980
October	1st to 10th	Night	36% 6% 9% 27% 20% 2	2081
	11th to 20th	Night	42% 4 12% 23% 17% 1	2160
	21st to end	Night	47% 5% 11% 24% 11% 1	2556
November	1st to 10th	Night	37% 6% 9% 27% 18% 3	2406
	11th to 20th	Night	48% 5% 14% 21% 12% 1	2470
	21st to end	Night	49% 5% 11% 23% 11% 1	2607
December	1st to 10th	Night	55% 5% 11% 20% 8% 1	2660
	11th to 20th	Night	54% 6% 13% 19% 8% 1	3281
	21st to end	Night	67% 7% 10% 12% 4	4884

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	19% 14% 33% 25% 9%	270
	11th to 20th	Day	21% 14% 37% 23% 3 2	257
	21st to end	Day	20% 12% 38% 25% 4 1	264
February	1st to 10th	Day	19% 18% 42% 16% 5%	240
	11th to 20th	Day	20% 22% 30% 24% 5%	240
	21st to end	Day	24% 19% 40% 14% 3	198
March	1st to 10th	Day	17% 21% 40% 16% 6%	240
	11th to 20th	Day	22% 17% 34% 16% 9% 2	240
	21st to end	Day	28% 14% 30% 19% 7% 2	452
April	1st to 10th	Day	25% 12% 35% 22% 6%	420
	11th to 20th	Day	22% 19% 27% 19% 9% 3	412
	21st to end	Day	23% 14% 29% 22% 10% 1	420
May	1st to 10th	Day	19% 17% 30% 23% 9% 2	440
	11th to 20th	Day	23% 10% 30% 23% 12% 2	625
	21st to end	Day	17% 9% 27% 24% 16% 7%	679
June	1st to 10th	Day	9% 7% 31% 30% 19% 5%	630
	11th to 20th	Day	14% 5% 32% 29% 16% 5%	630
	21st to end	Day	12% 7% 27% 33% 16% 4	630
July	1st to 10th	Day	9% 3 18% 31% 26% 14%	621
	11th to 20th	Day	9% 4 26% 31% 21% 9%	618
	21st to end	Day	7% 3 25% 37% 21% 7%	684
August	1st to 10th	Day	9% 3 18% 32% 26% 12%	626
	11th to 20th	Day	10% 5% 17% 27% 24% 17%	448
	21st to end	Day	11% 5% 17% 31% 26% 10%	495
September	1st to 10th	Day	15% 7% 22% 27% 23% 7%	450
	11th to 20th	Day	12% 3 21% 30% 22% 12%	450
	21st to end	Day	14% 10% 27% 24% 17% 7%	450
October	1st to 10th	Day	16% 8% 30% 25% 17% 4	347
	11th to 20th	Day	24% 20% 31% 18% 7%	270
	21st to end	Day	31% 14% 28% 21% 5%	297
November	1st to 10th	Day	15% 16% 36% 21% 9% 3	270
	11th to 20th	Day	20% 16% 41% 16% 7% 1	270
	21st to end	Day	25% 12% 39% 18% 6%	270
December	1st to 10th	Day	17% 17% 43% 16% 6% 1	270
	11th to 20th	Day	18% 13% 37% 24% 8%	270
	21st to end	Day	26% 18% 38% 16% 2	297
January	1st to 10th	Night	19% 13% 37% 26% 6%	950
	11th to 20th	Night	22% 12% 37% 23% 5% 1	930
	21st to end	Night	19% 11% 36% 27% 6%	990
February	1st to 10th	Night	23% 9% 40% 23% 5%	900
	11th to 20th	Night	19% 14% 37% 25% 5%	722
	21st to end	Night	24% 13% 37% 22% 4	592
March	1st to 10th	Night	21% 11% 35% 26% 6%	720
	11th to 20th	Night	16% 11% 35% 31% 7%	654
	21st to end	Night	24% 11% 30% 27% 7% 1	594
April	1st to 10th	Night	22% 12% 36% 25% 5%	540
	11th to 20th	Night	24% 12% 31% 27% 7%	533
	21st to end	Night	21% 8% 35% 27% 8% 1	540
May	1st to 10th	Night	18% 9% 35% 30% 7% 1	540
	11th to 20th	Night	18% 6% 33% 32% 11%	531
	21st to end	Night	15% 4 30% 34% 17%	584
June	1st to 10th	Night	8% 4 28% 45% 15% 1	540
	11th to 20th	Night	13% 4 30% 40% 12% 1	540
	21st to end	Night	9% 4 29% 39% 18% 1	540
July	1st to 10th	Night	7% 2 16% 42% 29% 4	525
	11th to 20th	Night	7% 4 21% 43% 24% 1	522
	21st to end	Night	7% 2 20% 45% 24% 1	591
August	1st to 10th	Night	6% 1 15% 46% 28% 4	537
	11th to 20th	Night	8% 3 13% 40% 32% 5%	534
	21st to end	Night	10% 2 16% 40% 29% 4	594
September	1st to 10th	Night	10% 4 21% 36% 24% 4	540
	11th to 20th	Night	13% 4 21% 33% 26% 4	602
	21st to end	Night	13% 8% 26% 30% 21% 2	720
October	1st to 10th	Night	14% 5% 31% 31% 16% 2	720
	11th to 20th	Night	22% 11% 31% 25% 10%	720
	21st to end	Night	24% 11% 33% 25% 7%	792
November	1st to 10th	Night	17% 10% 38% 24% 10% 1	740
	11th to 20th	Night	20% 15% 35% 24% 6%	760
	21st to end	Night	22% 11% 36% 25% 6%	897
December	1st to 10th	Night	22% 11% 39% 22% 6%	950
	11th to 20th	Night	23% 11% 35% 26% 5% 1	950
	21st to end	Night	29% 13% 34% 22% 2	1045

Page generated at 2024-01-13 18:28:33. Version ac07

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