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 2026-04-02.

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	13% 9% 4 8% 5% 4 5% 4 6% 7% 37%	131419
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 38%	130686
Transparency	Day	44% 7% 12% 23% 13% 1	134926
	Night	45% 6% 11% 22% 14% 2	135254
Seeing	Day	16% 11% 30% 25% 14% 5%	17702
	Night	17% 10% 32% 30% 11% 1	27706

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% 13% 7% 14% 6% 5% 5% 4 5% 6% 23%	4691
	11th to 20th	Day	7% 10% 7% 13% 5% 4 5% 6% 6% 6% 31%	4710
	21st to end	Day	10% 12% 6% 10% 5% 5% 4 3 5% 6% 33%	5396
February	1st to 10th	Day	11% 13% 5% 10% 6% 6% 6% 4 5% 6% 27%	1890
	11th to 20th	Day	13% 10% 4 8% 6% 5% 4 3 5% 6% 37%	2024
	21st to end	Day	13% 13% 4 11% 5% 4 4 3 6% 6% 32%	1730
March	1st to 10th	Day	15% 9% 3 6% 4 3 4 3 4 5% 44%	4580
	11th to 20th	Day	11% 6% 3 7% 5% 4 4 3 6% 8% 42%	4844
	21st to end	Day	21% 12% 6% 11% 6% 5% 4 4 4 5% 23%	6088
April	1st to 10th	Day	18% 12% 3 9% 5% 5% 4 4 4 6% 30%	2412
	11th to 20th	Day	16% 10% 3 7% 5% 4 5% 5% 5% 6% 34%	2374
	21st to end	Day	18% 9% 3 8% 5% 5% 4 4 5% 6% 32%	2476
May	1st to 10th	Day	15% 8% 2 7% 4 5% 5% 4 5% 7% 37%	5907
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 4 6% 8% 41%	6319
	21st to end	Day	14% 6% 3 6% 5% 4 5% 4 6% 9% 37%	6935
June	1st to 10th	Day	10% 5% 2 6% 5% 5% 4 5% 5% 9% 44%	2800
	11th to 20th	Day	10% 6% 2 5% 4 4 5% 4 7% 9% 44%	2800
	21st to end	Day	11% 6% 2 7% 4 4 5% 4 7% 10% 38%	2800
July	1st to 10th	Day	10% 7% 2 8% 5% 5% 5% 4 8% 9% 37%	6360
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 4 6% 9% 44%	6360
	21st to end	Day	9% 7% 3 7% 5% 5% 5% 4 6% 9% 39%	6924
August	1st to 10th	Day	9% 6% 2 5% 5% 4 5% 5% 7% 10% 42%	4509
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 7% 9% 45%	3858
	21st to end	Day	9% 5% 2 5% 4 4 5% 3 6% 8% 48%	4312
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 5% 8% 48%	2400
	11th to 20th	Day	12% 4 2 4 3 3 4 3 5% 8% 52%	2310
	21st to end	Day	11% 7% 2 7% 4 4 4 3 6% 7% 45%	2200
October	1st to 10th	Day	13% 7% 3 5% 4 4 3 3 5% 6% 48%	2085
	11th to 20th	Day	19% 9% 3 6% 4 4 4 4 5% 7% 35%	2000
	21st to end	Day	18% 10% 3 6% 5% 4 3 2 4 5% 38%	2000
November	1st to 10th	Day	13% 8% 3 6% 4 3 4 3 5% 6% 44%	1852
	11th to 20th	Day	14% 13% 4 9% 5% 4 5% 3 5% 6% 31%	1890
	21st to end	Day	16% 14% 5% 9% 5% 3 2 3 4 5% 34%	1735
December	1st to 10th	Day	8% 9% 4 8% 6% 5% 5% 3 5% 7% 40%	2690
	11th to 20th	Day	12% 15% 5% 12% 6% 5% 5% 4 5% 6% 24%	3088
	21st to end	Day	20% 22% 9% 13% 6% 4 4 2 4 5% 12%	4070
January	1st to 10th	Night	10% 13% 7% 14% 6% 4 4 2 4 4 31%	8232
	11th to 20th	Night	9% 13% 6% 15% 7% 7% 6% 5% 6% 5% 22%	8280
	21st to end	Night	11% 13% 6% 9% 5% 5% 4 4 5% 6% 32%	8800
February	1st to 10th	Night	13% 15% 4 9% 6% 5% 4 3 5% 5% 33%	2730
	11th to 20th	Night	13% 11% 4 7% 5% 5% 4 3 5% 6% 38%	2480
	21st to end	Night	16% 12% 4 9% 4 3 3 3 5% 6% 36%	2076
March	1st to 10th	Night	16% 9% 3 7% 4 4 3 3 4 5% 43%	5493
	11th to 20th	Night	9% 7% 3 6% 4 5% 4 3 5% 8% 47%	5378
	21st to end	Night	21% 12% 5% 9% 5% 4 4 3 4 5% 28%	5083
April	1st to 10th	Night	17% 10% 3 6% 4 4 4 3 4 6% 38%	2010
	11th to 20th	Night	18% 10% 3 7% 5% 4 3 3 4 6% 39%	1975
	21st to end	Night	17% 9% 3 6% 4 4 4 3 6% 7% 37%	1922
May	1st to 10th	Night	18% 7% 2 6% 4 5% 4 4 5% 7% 38%	3974
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 44%	3596
	21st to end	Night	14% 8% 3 7% 5% 4 4 3 6% 7% 39%	3942
June	1st to 10th	Night	8% 4 1 5% 5% 5% 5% 5% 6% 7% 48%	1600
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 4 5% 10% 45%	1600
	21st to end	Night	9% 7% 3 6% 5% 4 4 4 4 9% 45%	1600
July	1st to 10th	Night	12% 6% 2 7% 5% 4 5% 3 6% 7% 42%	3618
	11th to 20th	Night	6% 6% 2 6% 4 4 4 4 6% 8% 51%	3617
	21st to end	Night	8% 7% 3 6% 4 4 5% 4 6% 8% 45%	3947
August	1st to 10th	Night	6% 5% 2 5% 4 4 4 4 6% 9% 52%	2647
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 4 6% 7% 49%	3190
	21st to end	Night	8% 5% 1 4 3 4 4 4 5% 9% 52%	3586
September	1st to 10th	Night	8% 6% 2 7% 3 3 3 2 6% 6% 55%	2000
	11th to 20th	Night	11% 4 1 4 4 4 4 2 5% 7% 54%	2070
	21st to end	Night	10% 6% 2 6% 4 4 4 4 5% 6% 49%	2200
October	1st to 10th	Night	11% 6% 2 6% 3 4 3 3 4 6% 51%	2313
	11th to 20th	Night	17% 7% 2 7% 4 4 3 3 4 6% 44%	2400
	21st to end	Night	19% 9% 3 6% 4 4 4 3 5% 6% 38%	2840
November	1st to 10th	Night	13% 7% 3 6% 3 3 3 2 5% 6% 47%	2666
	11th to 20th	Night	14% 11% 3 8% 5% 4 4 3 5% 6% 37%	2730
	21st to end	Night	17% 12% 4 8% 5% 3 3 2 4 5% 36%	2882
December	1st to 10th	Night	10% 10% 3 8% 5% 5% 5% 4 5% 7% 41%	4720
	11th to 20th	Night	16% 17% 4 9% 5% 4 4 3 5% 5% 29%	5339
	21st to end	Night	21% 19% 7% 11% 5% 4 5% 3 5% 4 16%	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	61% 5% 14% 15% 5%	4692
	11th to 20th	Day	50% 6% 10% 17% 15% 2	4710
	21st to end	Day	52% 4 14% 22% 9%	5396
February	1st to 10th	Day	56% 6% 13% 15% 9% 1	1890
	11th to 20th	Day	49% 5% 11% 24% 10% 2	2034
	21st to end	Day	53% 6% 9% 21% 10% 2	1730
March	1st to 10th	Day	42% 6% 11% 27% 11% 4	4580
	11th to 20th	Day	39% 6% 12% 31% 11% 1	4844
	21st to end	Day	61% 8% 10% 13% 7% 1	6090
April	1st to 10th	Day	54% 6% 10% 21% 9%	2412
	11th to 20th	Day	49% 7% 10% 22% 11% 2	2374
	21st to end	Day	51% 6% 12% 17% 12% 1	2476
May	1st to 10th	Day	44% 7% 11% 21% 17% 1	5942
	11th to 20th	Day	39% 8% 10% 26% 16% 1	6323
	21st to end	Day	40% 8% 12% 25% 12% 3	6949
June	1st to 10th	Day	35% 8% 13% 27% 16% 1	2800
	11th to 20th	Day	34% 8% 13% 24% 18% 2	2800
	21st to end	Day	38% 9% 14% 23% 14% 2	2800
July	1st to 10th	Day	39% 7% 15% 26% 12% 1	6291
	11th to 20th	Day	34% 7% 15% 27% 16% 1	6285
	21st to end	Day	38% 9% 15% 20% 16% 2	6728
August	1st to 10th	Day	35% 9% 15% 28% 12% 1	4494
	11th to 20th	Day	33% 8% 14% 32% 13% 1	3894
	21st to end	Day	33% 7% 13% 29% 16% 1	4311
September	1st to 10th	Day	34% 8% 11% 28% 18% 2	2400
	11th to 20th	Day	30% 5% 12% 32% 19% 2	2310
	21st to end	Day	38% 5% 9% 29% 18% 1	2200
October	1st to 10th	Day	24% 4 7% 37% 27% 1	3397
	11th to 20th	Day	34% 5% 11% 26% 23% 1	3240
	21st to end	Day	43% 4 8% 28% 14% 3	3212
November	1st to 10th	Day	40% 5% 14% 24% 15% 1	1852
	11th to 20th	Day	54% 4 12% 20% 9% 1	1890
	21st to end	Day	53% 4 13% 22% 7%	1735
December	1st to 10th	Day	43% 5% 20% 25% 7% 1	2690
	11th to 20th	Day	58% 6% 12% 17% 6% 1	3085
	21st to end	Day	76% 4 7% 9% 5%	4070
January	1st to 10th	Night	56% 5% 11% 19% 9%	8233
	11th to 20th	Night	62% 5% 9% 10% 12% 1	8280
	21st to end	Night	53% 5% 12% 20% 10%	8800
February	1st to 10th	Night	54% 4 11% 18% 12% 1	2730
	11th to 20th	Night	48% 4 11% 23% 13% 1	2481
	21st to end	Night	49% 5% 11% 20% 11% 4	2076
March	1st to 10th	Night	44% 5% 12% 22% 11% 6%	5493
	11th to 20th	Night	35% 5% 11% 32% 13% 3	5378
	21st to end	Night	58% 6% 9% 17% 10% 1	5083
April	1st to 10th	Night	46% 6% 11% 21% 14% 1	2010
	11th to 20th	Night	47% 5% 6% 21% 18% 3	1975
	21st to end	Night	45% 6% 12% 23% 12% 2	1922
May	1st to 10th	Night	44% 8% 12% 18% 18% 2	4001
	11th to 20th	Night	35% 10% 14% 23% 15% 4	3597
	21st to end	Night	41% 9% 11% 21% 15% 3	3950
June	1st to 10th	Night	31% 9% 14% 25% 19% 2	1600
	11th to 20th	Night	34% 8% 11% 23% 23% 3	1600
	21st to end	Night	37% 7% 14% 21% 19% 2	1600
July	1st to 10th	Night	39% 7% 13% 25% 13% 2	3580
	11th to 20th	Night	29% 7% 15% 29% 19% 1	3572
	21st to end	Night	34% 8% 14% 24% 18% 2	3832
August	1st to 10th	Night	28% 7% 14% 29% 19% 2	2638
	11th to 20th	Night	31% 8% 14% 30% 17%	3220
	21st to end	Night	29% 7% 13% 31% 18% 3	3586
September	1st to 10th	Night	30% 6% 11% 27% 23% 3	2000
	11th to 20th	Night	29% 6% 10% 32% 21% 3	2070
	21st to end	Night	35% 6% 10% 29% 19% 1	2200
October	1st to 10th	Night	24% 4 7% 35% 28% 1	3781
	11th to 20th	Night	35% 4 9% 25% 24% 3	3899
	21st to end	Night	42% 5% 9% 25% 16% 3	4578
November	1st to 10th	Night	38% 5% 9% 27% 18% 2	2666
	11th to 20th	Night	48% 5% 13% 22% 11% 1	2730
	21st to end	Night	52% 5% 11% 22% 10% 1	2882
December	1st to 10th	Night	43% 5% 14% 26% 9% 2	4720
	11th to 20th	Night	58% 5% 11% 16% 10% 1	5341
	21st to end	Night	69% 6% 9% 11% 5%	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% 15% 34% 26% 8%	330
	11th to 20th	Day	17% 18% 40% 21% 3 1	330
	21st to end	Day	20% 14% 39% 23% 3 1	363
February	1st to 10th	Day	17% 18% 40% 18% 6%	330
	11th to 20th	Day	18% 21% 35% 22% 4	330
	21st to end	Day	22% 18% 42% 15% 3	273
March	1st to 10th	Day	18% 20% 41% 16% 5%	330
	11th to 20th	Day	24% 18% 35% 15% 6% 1	330
	21st to end	Day	26% 16% 33% 19% 6% 1	583
April	1st to 10th	Day	26% 15% 33% 22% 5%	504
	11th to 20th	Day	23% 21% 26% 19% 9% 2	492
	21st to end	Day	23% 15% 31% 22% 9% 1	500
May	1st to 10th	Day	18% 16% 31% 23% 10% 2	522
	11th to 20th	Day	22% 11% 29% 23% 13% 3	725
	21st to end	Day	17% 10% 28% 25% 15% 6%	789
June	1st to 10th	Day	9% 8% 32% 29% 17% 4	730
	11th to 20th	Day	13% 5% 33% 29% 15% 5%	730
	21st to end	Day	11% 8% 28% 33% 15% 4	730
July	1st to 10th	Day	9% 3 19% 31% 25% 12%	721
	11th to 20th	Day	9% 5% 26% 31% 21% 9%	718
	21st to end	Day	7% 4 24% 37% 21% 7%	794
August	1st to 10th	Day	9% 4 18% 33% 25% 11%	726
	11th to 20th	Day	12% 6% 18% 27% 23% 15%	528
	21st to end	Day	10% 5% 16% 30% 28% 10%	583
September	1st to 10th	Day	13% 7% 22% 27% 23% 8%	530
	11th to 20th	Day	11% 2 20% 29% 24% 14%	530
	21st to end	Day	14% 9% 27% 24% 18% 8%	530
October	1st to 10th	Day	14% 9% 29% 26% 19% 4	415
	11th to 20th	Day	22% 18% 32% 20% 8% 1	330
	21st to end	Day	28% 15% 29% 22% 6%	363
November	1st to 10th	Day	16% 18% 36% 19% 8% 2	330
	11th to 20th	Day	20% 19% 37% 16% 7% 1	330
	21st to end	Day	25% 13% 40% 17% 5%	330
December	1st to 10th	Day	15% 18% 43% 17% 6% 1	330
	11th to 20th	Day	18% 14% 39% 22% 7%	330
	21st to end	Day	27% 18% 37% 16% 3	363
January	1st to 10th	Night	18% 13% 37% 26% 6%	1050
	11th to 20th	Night	20% 14% 39% 22% 5% 1	1050
	21st to end	Night	18% 13% 37% 26% 5%	1155
February	1st to 10th	Night	21% 10% 40% 23% 5%	1050
	11th to 20th	Night	18% 14% 37% 27% 4	845
	21st to end	Night	22% 13% 40% 22% 3	692
March	1st to 10th	Night	20% 12% 38% 24% 6%	840
	11th to 20th	Night	17% 13% 36% 28% 7%	762
	21st to end	Night	23% 13% 31% 26% 6% 1	693
April	1st to 10th	Night	22% 13% 36% 25% 4	603
	11th to 20th	Night	23% 13% 31% 26% 7%	593
	21st to end	Night	21% 9% 35% 27% 8% 1	600
May	1st to 10th	Night	18% 9% 34% 31% 7% 1	600
	11th to 20th	Night	17% 6% 33% 33% 11%	591
	21st to end	Night	16% 5% 29% 35% 16%	650
June	1st to 10th	Night	8% 5% 29% 45% 14% 1	600
	11th to 20th	Night	12% 5% 31% 41% 11% 1	600
	21st to end	Night	9% 4 30% 39% 17% 1	600
July	1st to 10th	Night	8% 2 17% 41% 28% 3	585
	11th to 20th	Night	7% 4 21% 43% 24% 1	582
	21st to end	Night	7% 2 20% 46% 24% 2	657
August	1st to 10th	Night	6% 2 16% 46% 28% 3	597
	11th to 20th	Night	8% 4 12% 40% 31% 4	594
	21st to end	Night	9% 2 16% 42% 28% 3	660
September	1st to 10th	Night	9% 4 21% 37% 25% 4	600
	11th to 20th	Night	12% 4 19% 34% 28% 4	670
	21st to end	Night	11% 8% 26% 32% 21% 2	800
October	1st to 10th	Night	14% 5% 31% 33% 16% 1	800
	11th to 20th	Night	22% 11% 31% 27% 10%	800
	21st to end	Night	23% 11% 33% 26% 7%	880
November	1st to 10th	Night	17% 11% 38% 24% 9%	820
	11th to 20th	Night	19% 16% 35% 23% 6%	840
	21st to end	Night	22% 14% 35% 24% 6%	992
December	1st to 10th	Night	21% 12% 40% 22% 6%	1050
	11th to 20th	Night	22% 12% 36% 25% 5% 1	1050
	21st to end	Night	29% 13% 34% 22% 2	1155

Page generated at 2026-03-30 01:18:43. Version ac07

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