Old Crow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Crow clear sky chart from 2005-11-06 to 2024-12-09.

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	9% 11% 4 11% 7% 6% 6% 5% 7% 8% 25%	109564
	Night	6% 13% 6% 14% 8% 7% 7% 5% 8% 9% 18%	102209
Transparency	Day	53% 9% 18% 16% 4	109165
	Night	58% 9% 13% 14% 6% 1	102244
Seeing	Day	13% 6% 16% 29% 25% 11%	19371
	Night	12% 4 13% 32% 29% 10%	22982

By Month

Percentage Cloud Cover NW (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	1 8% 3 7% 6% 2 3 8% 7% 22% 32%	138
	11th to 20th	Day	5% 12% 6% 10% 8% 8% 9% 7% 9% 11% 16%	676
	21st to end	Day	6% 13% 5% 13% 9% 7% 7% 6% 8% 12% 13%	1336
February	1st to 10th	Day	2 7% 3 13% 10% 12% 7% 8% 9% 12% 17%	969
	11th to 20th	Day	2 6% 4 12% 10% 9% 10% 6% 15% 11% 14%	1295
	21st to end	Day	2 6% 5% 13% 9% 8% 10% 8% 10% 14% 15%	1256
March	1st to 10th	Day	1 8% 6% 24% 11% 7% 7% 5% 7% 11% 13%	2810
	11th to 20th	Day	2 11% 6% 18% 11% 9% 7% 7% 9% 7% 13%	3421
	21st to end	Day	3 12% 8% 17% 8% 7% 6% 5% 8% 8% 18%	4080
April	1st to 10th	Day	4 16% 5% 13% 9% 6% 6% 4 6% 6% 24%	2493
	11th to 20th	Day	4 12% 4 9% 6% 6% 6% 5% 6% 9% 33%	2732
	21st to end	Day	3 9% 3 8% 7% 5% 6% 5% 8% 9% 37%	2985
May	1st to 10th	Day	12% 22% 7% 12% 6% 5% 4 3 4 5% 19%	5476
	11th to 20th	Day	5% 9% 4 9% 7% 6% 7% 6% 8% 8% 31%	5875
	21st to end	Day	11% 12% 4 8% 5% 5% 5% 5% 7% 8% 30%	7136
June	1st to 10th	Day	9% 8% 3 7% 6% 6% 6% 6% 7% 8% 35%	4527
	11th to 20th	Day	11% 6% 3 7% 6% 5% 6% 6% 7% 9% 35%	4560
	21st to end	Day	11% 7% 3 7% 6% 6% 6% 5% 8% 9% 31%	4560
July	1st to 10th	Day	13% 11% 4 11% 7% 7% 7% 6% 7% 8% 21%	7600
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 5% 7% 9% 32%	6668
	21st to end	Day	12% 7% 3 9% 6% 6% 6% 4 7% 8% 31%	6535
August	1st to 10th	Day	12% 8% 3 8% 6% 5% 5% 5% 7% 8% 33%	5401
	11th to 20th	Day	14% 8% 4 9% 6% 7% 7% 5% 8% 9% 24%	4948
	21st to end	Day	14% 10% 4 12% 7% 7% 6% 5% 7% 6% 22%	5113
September	1st to 10th	Day	15% 11% 3 9% 6% 6% 5% 5% 7% 6% 25%	2504
	11th to 20th	Day	14% 13% 4 9% 7% 5% 5% 4 6% 8% 25%	2291
	21st to end	Day	16% 20% 9% 12% 7% 4 5% 4 4 3 16%	2012
October	1st to 10th	Day	9% 18% 7% 12% 5% 5% 4 4 6% 8% 22%	3052
	11th to 20th	Day	8% 20% 9% 20% 9% 7% 6% 4 4 4 10%	2535
	21st to end	Day	9% 13% 4 15% 11% 8% 9% 5% 7% 9% 11%	2293
November	1st to 10th	Day	6% 19% 9% 14% 7% 7% 8% 6% 7% 7% 8%	1043
	11th to 20th	Day	3 11% 6% 18% 13% 9% 9% 6% 9% 6% 9%	780
	21st to end	Day	8% 14% 5% 12% 11% 9% 8% 6% 12% 7% 8%	414
December	1st to 10th	Day	2 20% 4 14% 6% 8% 2 10% 12% 14% 8%	50
	January	1st to 10th	Night	2 8% 3 10% 6% 7% 7% 5% 9% 14% 28%	7112
11th to 20th		Night	3 10% 5% 13% 8% 7% 7% 4 7% 11% 24%	6218
21st to end		Night	4 12% 6% 13% 7% 7% 8% 6% 9% 14% 15%	6359
February	1st to 10th	Night	2 9% 5% 12% 9% 10% 9% 6% 11% 13% 16%	3211
	11th to 20th	Night	3 8% 5% 13% 10% 7% 6% 7% 10% 13% 18%	2772
	21st to end	Night	2 7% 4 14% 9% 9% 8% 7% 9% 10% 22%	2197
March	1st to 10th	Night	1 8% 5% 24% 11% 6% 8% 5% 7% 8% 16%	4054
	11th to 20th	Night	3 10% 6% 18% 10% 7% 6% 5% 7% 8% 19%	3538
	21st to end	Night	2 12% 8% 16% 7% 6% 7% 6% 6% 7% 24%	3556
April	1st to 10th	Night	5% 13% 7% 13% 8% 6% 6% 5% 5% 6% 26%	1687
	11th to 20th	Night	4 12% 3 10% 7% 6% 6% 4 7% 8% 33%	1396
	21st to end	Night	2 10% 3 9% 5% 4 6% 5% 6% 9% 41%	1195
May	1st to 10th	Night	15% 25% 7% 9% 5% 3 3 3 3 4 22%	1484
	11th to 20th	Night	6% 9% 2 6% 6% 6% 6% 5% 8% 10% 34%	1027
	21st to end	Night	10% 14% 5% 8% 3 5% 7% 5% 6% 7% 29%	450
July	11th to 20th	Night	12% 6% 3 10% 4 5% 4 4 7% 9% 37%	326
	21st to end	Night	12% 9% 3 8% 6% 5% 6% 5% 6% 9% 31%	1028
August	1st to 10th	Night	11% 7% 3 9% 6% 6% 7% 5% 7% 7% 33%	1528
	11th to 20th	Night	12% 7% 3 10% 8% 7% 8% 5% 7% 8% 24%	1884
	21st to end	Night	16% 12% 5% 9% 6% 6% 6% 5% 7% 7% 22%	2554
September	1st to 10th	Night	18% 10% 4 8% 6% 5% 5% 4 6% 6% 27%	1674
	11th to 20th	Night	18% 11% 3 9% 5% 5% 4 4 6% 7% 27%	1889
	21st to end	Night	19% 20% 6% 11% 4 5% 5% 4 4 5% 17%	2168
October	1st to 10th	Night	9% 17% 6% 10% 6% 4 5% 4 5% 9% 25%	3918
	11th to 20th	Night	8% 18% 9% 16% 7% 6% 6% 4 6% 7% 14%	4393
	21st to end	Night	7% 17% 6% 16% 9% 9% 8% 5% 7% 7% 11%	5258
November	1st to 10th	Night	6% 19% 7% 16% 9% 7% 7% 5% 7% 7% 10%	3233
	11th to 20th	Night	4 12% 6% 18% 12% 9% 8% 5% 8% 9% 8%	3620
	21st to end	Night	6% 15% 6% 15% 10% 9% 7% 5% 10% 8% 9%	3986
December	1st to 10th	Night	5% 14% 6% 13% 9% 8% 6% 6% 10% 11% 13%	4459
	11th to 20th	Night	4 14% 7% 17% 10% 8% 7% 6% 9% 8% 9%	5675
	21st to end	Night	3 15% 6% 14% 9% 7% 7% 7% 10% 10% 11%	8360

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	33% 4 13% 14% 36%	138
	11th to 20th	Day	58% 10% 8% 11% 11% 2	684
	21st to end	Day	59% 9% 7% 13% 13%	1336
February	1st to 10th	Day	54% 9% 11% 17% 7% 2	969
	11th to 20th	Day	52% 13% 13% 17% 5%	1302
	21st to end	Day	53% 12% 16% 11% 8%	1256
March	1st to 10th	Day	61% 9% 12% 15% 2	2810
	11th to 20th	Day	62% 10% 14% 11% 3	3421
	21st to end	Day	58% 8% 19% 11% 3	4080
April	1st to 10th	Day	59% 9% 14% 13% 6%	2493
	11th to 20th	Day	44% 13% 21% 17% 5%	2732
	21st to end	Day	39% 11% 23% 20% 7%	2985
May	1st to 10th	Day	65% 7% 12% 13% 2	5476
	11th to 20th	Day	44% 12% 21% 21% 2	5879
	21st to end	Day	47% 10% 19% 17% 6%	7137
June	1st to 10th	Day	42% 11% 17% 20% 10%	4527
	11th to 20th	Day	42% 9% 15% 25% 8%	4560
	21st to end	Day	45% 12% 16% 22% 5%	4560
July	1st to 10th	Day	58% 7% 20% 13% 2	7481
	11th to 20th	Day	46% 7% 21% 23% 2	6547
	21st to end	Day	49% 8% 19% 22% 2	6328
August	1st to 10th	Day	46% 8% 24% 20% 2	5380
	11th to 20th	Day	55% 8% 24% 13%	4998
	21st to end	Day	60% 7% 19% 14%	5112
September	1st to 10th	Day	54% 12% 21% 11% 2	2504
	11th to 20th	Day	55% 11% 21% 12% 1	2291
	21st to end	Day	70% 7% 12% 10% 1	2012
October	1st to 10th	Day	62% 5% 16% 17% 1	3052
	11th to 20th	Day	78% 5% 9% 7%	2535
	21st to end	Day	69% 6% 11% 14%	2293
November	1st to 10th	Day	70% 10% 13% 6% 1	1043
	11th to 20th	Day	68% 12% 11% 7% 2	780
	21st to end	Day	66% 11% 9% 9% 3 1	414
December	1st to 10th	Day	60% 16% 16% 2 6%	50
	January	1st to 10th	Night	41% 11% 10% 17% 21%	7112
11th to 20th		Night	52% 9% 9% 12% 11% 7%	6271
21st to end		Night	54% 9% 8% 12% 16%	6359
February	1st to 10th	Night	52% 10% 13% 15% 9% 1	3211
	11th to 20th	Night	52% 10% 13% 19% 7%	2776
	21st to end	Night	52% 12% 15% 14% 8%	2197
March	1st to 10th	Night	61% 8% 10% 17% 3	4054
	11th to 20th	Night	58% 10% 15% 13% 4	3540
	21st to end	Night	56% 10% 15% 14% 5%	3556
April	1st to 10th	Night	57% 10% 15% 12% 6% 1	1687
	11th to 20th	Night	46% 11% 20% 19% 5%	1396
	21st to end	Night	37% 9% 22% 25% 6%	1195
May	1st to 10th	Night	66% 5% 13% 13% 3	1484
	11th to 20th	Night	39% 13% 23% 22% 3	1027
	21st to end	Night	48% 11% 15% 19% 8%	450
July	11th to 20th	Night	44% 7% 16% 29% 4	322
	21st to end	Night	48% 7% 19% 24% 2	996
August	1st to 10th	Night	48% 10% 18% 22% 2	1524
	11th to 20th	Night	55% 7% 24% 13%	1900
	21st to end	Night	59% 6% 23% 12%	2554
September	1st to 10th	Night	54% 12% 20% 12% 2	1674
	11th to 20th	Night	53% 10% 22% 13% 1	1889
	21st to end	Night	68% 8% 12% 11% 1	2168
October	1st to 10th	Night	57% 5% 16% 21% 1	3918
	11th to 20th	Night	70% 5% 14% 10% 1	4393
	21st to end	Night	71% 7% 11% 10% 1	5258
November	1st to 10th	Night	70% 9% 13% 7% 1	3233
	11th to 20th	Night	69% 10% 12% 7% 1	3620
	21st to end	Night	68% 8% 9% 11% 3 1	3986
December	1st to 10th	Night	62% 9% 12% 14% 3	4459
	11th to 20th	Night	66% 9% 11% 11% 4	5675
	21st to end	Night	60% 10% 10% 13% 6% 1	8360

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	2 2 10% 41% 29% 15%	41
	11th to 20th	Day	8% 3 13% 31% 33% 11%	90
	21st to end	Day	7% 5% 17% 28% 27% 15%	99
February	1st to 10th	Day	2 2 12% 44% 27% 14%	109
	11th to 20th	Day	5% 1 11% 35% 31% 17%	365
	21st to end	Day	3 4 15% 30% 31% 16%	307
March	1st to 10th	Day	6% 2 13% 29% 32% 19%	370
	11th to 20th	Day	8% 5% 11% 36% 27% 13%	370
	21st to end	Day	7% 5% 15% 27% 25% 20%	502
April	1st to 10th	Day	8% 6% 13% 32% 33% 9%	650
	11th to 20th	Day	8% 5% 14% 32% 30% 11%	640
	21st to end	Day	4 4 15% 30% 30% 17%	650
May	1st to 10th	Day	14% 7% 17% 31% 23% 8%	710
	11th to 20th	Day	10% 6% 16% 30% 28% 9%	981
	21st to end	Day	11% 8% 20% 32% 23% 6%	1145
June	1st to 10th	Day	11% 6% 19% 33% 24% 6%	1234
	11th to 20th	Day	12% 7% 18% 32% 24% 8%	1250
	21st to end	Day	14% 4 14% 32% 28% 9%	1250
July	1st to 10th	Day	14% 7% 16% 27% 25% 11%	1226
	11th to 20th	Day	14% 4 19% 26% 24% 12%	1047
	21st to end	Day	13% 5% 17% 27% 27% 12%	1155
August	1st to 10th	Day	15% 7% 19% 27% 20% 12%	709
	11th to 20th	Day	18% 8% 21% 26% 20% 7%	665
	21st to end	Day	25% 5% 15% 22% 24% 9%	748
September	1st to 10th	Day	19% 7% 16% 22% 22% 14%	680
	11th to 20th	Day	20% 5% 16% 26% 23% 10%	508
	21st to end	Day	24% 6% 16% 23% 20% 11%	390
October	1st to 10th	Day	18% 9% 18% 26% 19% 8%	390
	11th to 20th	Day	17% 4 17% 26% 23% 13%	390
	21st to end	Day	21% 6% 15% 24% 24% 10%	315
November	1st to 10th	Day	11% 6% 13% 30% 27% 14%	160
	11th to 20th	Day	3 2 9% 31% 33% 22%	100
	21st to end	Day	11% 4 9% 25% 34% 17%	100
December	1st to 10th	Day	12% 12% 8% 28% 20% 20%	25
	January	1st to 10th	Night	9% 3 12% 33% 27% 16%	1171
11th to 20th		Night	8% 4 11% 36% 30% 11%	1130
21st to end		Night	7% 5% 13% 32% 31% 11%	1125
February	1st to 10th	Night	5% 3 11% 35% 33% 13%	850
	11th to 20th	Night	7% 3 10% 39% 31% 10%	834
	21st to end	Night	6% 3 12% 37% 31% 11%	703
March	1st to 10th	Night	4 2 11% 41% 32% 10%	850
	11th to 20th	Night	6% 2 9% 39% 37% 7%	609
	21st to end	Night	4 4 14% 35% 33% 10%	627
April	1st to 10th	Night	10% 3 14% 36% 29% 8%	570
	11th to 20th	Night	8% 2 13% 37% 33% 7%	563
	21st to end	Night	5% 2 16% 40% 33% 4	435
May	1st to 10th	Night	15% 7% 13% 34% 28% 2	190
	11th to 20th	Night	9% 2 14% 40% 35%	187
	21st to end	Night	10% 9% 20% 38% 23% 1	182
July	11th to 20th	Night	15% 4 22% 33% 24% 3	157
	21st to end	Night	18% 4 21% 32% 22% 3	208
August	1st to 10th	Night	19% 6% 15% 33% 26% 2	189
	11th to 20th	Night	21% 5% 19% 29% 24% 2	375
	21st to end	Night	22% 4 13% 24% 32% 5%	627
September	1st to 10th	Night	24% 4 11% 25% 28% 8%	570
	11th to 20th	Night	22% 4 17% 28% 24% 6%	570
	21st to end	Night	25% 5% 17% 27% 19% 7%	648
October	1st to 10th	Night	19% 7% 17% 29% 22% 6%	795
	11th to 20th	Night	21% 4 16% 21% 29% 9%	860
	21st to end	Night	20% 5% 13% 25% 25% 12%	946
November	1st to 10th	Night	14% 4 14% 30% 29% 9%	915
	11th to 20th	Night	8% 4 13% 25% 32% 19%	1110
	21st to end	Night	12% 4 10% 27% 30% 17%	1200
December	1st to 10th	Night	12% 3 13% 36% 27% 9%	1224
	11th to 20th	Night	10% 4 10% 32% 33% 11%	1220
	21st to end	Night	7% 3 11% 33% 31% 14%	1342

Page generated at 2024-12-06 00:54:49. Version ac07

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