Coldfoot
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coldfoot clear sky chart from 2005-11-06 to 2026-01-17.

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
Transparency	Day	56% 9% 14% 15% 6% 1	133520
	Night	53% 7% 11% 15% 13% 2	129980
Seeing	Day	18% 5% 16% 25% 25% 11%	21004
	Night	12% 5% 17% 29% 27% 9%	24074

By Month

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	60% 2 7% 11% 10% 10%	308
	11th to 20th	Day	53% 6% 10% 17% 12% 3	1098
	21st to end	Day	44% 4 7% 18% 27% 1	2003
February	1st to 10th	Day	37% 8% 12% 20% 16% 7%	1105
	11th to 20th	Day	54% 8% 11% 14% 12% 2	1325
	21st to end	Day	56% 10% 10% 14% 9% 1	1320
March	1st to 10th	Day	47% 6% 10% 18% 19%	4200
	11th to 20th	Day	41% 6% 7% 13% 28% 5%	4672
	21st to end	Day	54% 9% 10% 13% 12% 1	5940
April	1st to 10th	Day	64% 6% 11% 11% 6% 1	2646
	11th to 20th	Day	52% 7% 14% 18% 8% 1	2786
	21st to end	Day	48% 10% 18% 17% 7%	3200
May	1st to 10th	Day	59% 11% 10% 16% 4	7785
	11th to 20th	Day	37% 11% 17% 23% 12% 1	8302
	21st to end	Day	53% 12% 18% 15% 2	10042
June	1st to 10th	Day	51% 12% 18% 16% 2	4644
	11th to 20th	Day	47% 11% 18% 21% 3	4800
	21st to end	Day	52% 11% 17% 17% 3	4800
July	1st to 10th	Day	51% 8% 14% 19% 7%	10494
	11th to 20th	Day	58% 11% 18% 12%	9142
	21st to end	Day	62% 9% 19% 10%	8963
August	1st to 10th	Day	70% 9% 14% 6% 1	5620
	11th to 20th	Day	80% 7% 9% 4	5176
	21st to end	Day	69% 8% 11% 11%	5137
September	1st to 10th	Day	65% 8% 13% 11% 2	2666
	11th to 20th	Day	69% 8% 12% 10% 1	2400
	21st to end	Day	62% 9% 12% 15% 1 1	2118
October	1st to 10th	Day	59% 8% 12% 17% 4	3136
	11th to 20th	Day	63% 7% 11% 17% 1	2647
	21st to end	Day	58% 7% 13% 18% 4	2403
November	1st to 10th	Day	58% 8% 13% 16% 4 1	1123
	11th to 20th	Day	46% 8% 19% 19% 6% 1	822
	21st to end	Day	61% 7% 7% 16% 9% 1	501
December	1st to 10th	Day	47% 6% 6% 9% 22% 9%	196
	January	1st to 10th	Night	44% 5% 10% 13% 20% 8%	9862
11th to 20th		Night	52% 6% 10% 18% 12% 3	9046
21st to end		Night	47% 3 6% 13% 30% 1	8978
February	1st to 10th	Night	40% 6% 11% 20% 17% 6%	3295
	11th to 20th	Night	54% 6% 12% 14% 12% 2	2972
	21st to end	Night	52% 9% 10% 19% 10% 1	2310
March	1st to 10th	Night	47% 7% 11% 18% 17% 1	5652
	11th to 20th	Night	41% 7% 8% 15% 23% 6%	5285
	21st to end	Night	57% 8% 7% 13% 14% 1	4991
April	1st to 10th	Night	61% 8% 13% 10% 6% 2	1751
	11th to 20th	Night	52% 9% 16% 16% 6% 2	1562
	21st to end	Night	45% 8% 20% 20% 8%	1200
May	1st to 10th	Night	54% 9% 12% 18% 7%	2186
	11th to 20th	Night	35% 9% 18% 20% 16% 1	1603
	21st to end	Night	52% 11% 19% 17% 1	853
July	11th to 20th	Night	59% 10% 20% 11%	708
	21st to end	Night	64% 7% 19% 10%	1594
August	1st to 10th	Night	66% 11% 16% 7% 1	1515
	11th to 20th	Night	78% 6% 11% 4	1948
	21st to end	Night	64% 10% 13% 13% 1	2771
September	1st to 10th	Night	65% 8% 14% 11% 2	1732
	11th to 20th	Night	71% 8% 13% 8% 1	2000
	21st to end	Night	64% 9% 10% 14% 3	2279
October	1st to 10th	Night	58% 7% 13% 18% 5%	4048
	11th to 20th	Night	65% 6% 11% 18% 1	4486
	21st to end	Night	57% 9% 12% 16% 6%	5395
November	1st to 10th	Night	59% 9% 11% 17% 5% 1	3396
	11th to 20th	Night	46% 10% 17% 19% 8% 1	3775
	21st to end	Night	59% 6% 10% 18% 7% 1	4116
December	1st to 10th	Night	59% 5% 7% 12% 10% 6%	7244
	11th to 20th	Night	44% 6% 14% 16% 20% 1	9195
	21st to end	Night	53% 5% 10% 13% 15% 4	12232

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	14% 23% 36% 23% 5%	22
	11th to 20th	Day	4 5% 29% 35% 22% 6%	106
	21st to end	Day	6% 3 19% 30% 31% 10%	135
February	1st to 10th	Day	4 4 17% 27% 30% 19%	300
	11th to 20th	Day	7% 8% 22% 29% 20% 14%	300
	21st to end	Day	5% 6% 16% 38% 26% 9%	331
March	1st to 10th	Day	5% 4 17% 31% 29% 15%	400
	11th to 20th	Day	6% 6% 20% 28% 26% 15%	461
	21st to end	Day	7% 6% 22% 31% 24% 11%	660
April	1st to 10th	Day	8% 5% 25% 28% 23% 10%	656
	11th to 20th	Day	12% 7% 18% 29% 25% 9%	690
	21st to end	Day	8% 3 14% 28% 29% 18%	700
May	1st to 10th	Day	14% 4 17% 27% 25% 13%	801
	11th to 20th	Day	13% 3 16% 27% 29% 13%	976
	21st to end	Day	14% 3 12% 27% 33% 11%	1222
June	1st to 10th	Day	16% 4 16% 24% 24% 14%	1251
	11th to 20th	Day	13% 4 15% 25% 33% 10%	1330
	21st to end	Day	14% 4 15% 28% 30% 8%	1330
July	1st to 10th	Day	18% 5% 13% 27% 27% 10%	1251
	11th to 20th	Day	27% 5% 13% 21% 23% 11%	1106
	21st to end	Day	29% 7% 13% 22% 22% 7%	1060
August	1st to 10th	Day	33% 6% 14% 23% 18% 6%	896
	11th to 20th	Day	38% 6% 16% 17% 16% 7%	715
	21st to end	Day	41% 9% 14% 14% 17% 5%	803
September	1st to 10th	Day	31% 8% 15% 19% 18% 9%	694
	11th to 20th	Day	33% 6% 16% 21% 17% 7%	620
	21st to end	Day	22% 4 15% 20% 27% 12%	447
October	1st to 10th	Day	21% 6% 21% 24% 18% 10%	420
	11th to 20th	Day	14% 4 14% 31% 22% 15%	420
	21st to end	Day	15% 4 19% 23% 24% 16%	426
November	1st to 10th	Day	10% 6% 18% 26% 27% 12%	203
	11th to 20th	Day	3 3 13% 30% 33% 19%	110
	21st to end	Day	12% 5% 15% 33% 19% 16%	110
December	1st to 10th	Day	13% 6% 21% 27% 27% 6%	52
	January	1st to 10th	Night	6% 5% 24% 31% 23% 11%	1270
11th to 20th		Night	7% 4 20% 32% 27% 9%	1186
21st to end		Night	7% 5% 17% 33% 30% 9%	1100
February	1st to 10th	Night	4 3 20% 31% 29% 12%	947
	11th to 20th	Night	10% 6% 20% 35% 23% 6%	884
	21st to end	Night	7% 4 17% 39% 27% 6%	743
March	1st to 10th	Night	5% 3 16% 41% 27% 9%	700
	11th to 20th	Night	7% 3 16% 37% 28% 9%	700
	21st to end	Night	7% 4 20% 33% 27% 9%	667
April	1st to 10th	Night	8% 3 18% 31% 32% 8%	600
	11th to 20th	Night	9% 3 16% 34% 29% 9%	587
	21st to end	Night	9% 3 11% 27% 35% 16%	400
May	1st to 10th	Night	14% 3 12% 20% 38% 13%	271
	11th to 20th	Night	15% 4 9% 31% 33% 9%	197
	21st to end	Night	14% 2 11% 26% 41% 6%	192
July	11th to 20th	Night	32% 6% 9% 15% 32% 7%	126
	21st to end	Night	26% 5% 8% 26% 30% 5%	219
August	1st to 10th	Night	29% 5% 7% 23% 28% 7%	294
	11th to 20th	Night	37% 5% 11% 15% 27% 5%	396
	21st to end	Night	38% 6% 9% 14% 24% 9%	601
September	1st to 10th	Night	30% 4 11% 18% 27% 10%	600
	11th to 20th	Night	29% 5% 12% 23% 27% 5%	600
	21st to end	Night	21% 4 14% 30% 22% 8%	659
October	1st to 10th	Night	20% 7% 18% 27% 19% 8%	786
	11th to 20th	Night	19% 5% 16% 26% 25% 9%	910
	21st to end	Night	15% 6% 13% 26% 30% 11%	1001
November	1st to 10th	Night	13% 7% 20% 30% 22% 8%	930
	11th to 20th	Night	6% 5% 14% 30% 27% 18%	1067
	21st to end	Night	11% 4 21% 28% 25% 11%	1270
December	1st to 10th	Night	12% 7% 20% 29% 24% 8%	1273
	11th to 20th	Night	8% 9% 21% 26% 27% 10%	1380
	21st to end	Night	6% 6% 21% 31% 28% 8%	1518

Page generated at 2026-01-13 21:14:27. Version ac07

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