Cape Race
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cape Race clear sky chart from 2005-11-06 to 2024-02-10.

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	24% 13% 5% 9% 7% 4 5% 4 5% 6% 19%	77868
	Night	24% 13% 6% 9% 7% 3 5% 4 5% 6% 19%	81131
Transparency	Day	63% 9% 11% 12% 5% 1	77560
	Night	64% 8% 10% 12% 6% 1	80974
Seeing	Day	29% 13% 27% 22% 8% 1	17022
	Night	30% 13% 29% 21% 7% 1	23771

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	19% 11% 7% 10% 7% 4 5% 5% 3 4 23%	2247
	11th to 20th	Day	25% 13% 5% 12% 9% 4 5% 4 4 4 15%	2530
	21st to end	Day	19% 13% 8% 13% 8% 4 4 5% 4 5% 17%	2783
February	1st to 10th	Day	22% 11% 8% 12% 10% 6% 6% 5% 5% 5% 11%	1686
	11th to 20th	Day	23% 15% 6% 12% 8% 4 4 4 4 6% 14%	1591
	21st to end	Day	15% 12% 7% 14% 10% 5% 6% 5% 5% 5% 18%	1480
March	1st to 10th	Day	18% 13% 7% 13% 8% 5% 6% 4 4 5% 18%	1821
	11th to 20th	Day	19% 11% 5% 11% 9% 4 6% 5% 6% 6% 19%	1980
	21st to end	Day	23% 14% 6% 11% 8% 3 5% 4 4 6% 15%	2178
April	1st to 10th	Day	26% 13% 6% 10% 7% 4 4 4 4 4 18%	2150
	11th to 20th	Day	24% 12% 5% 8% 7% 4 4 4 4 5% 21%	2311
	21st to end	Day	26% 13% 5% 10% 6% 4 4 4 4 5% 21%	2340
May	1st to 10th	Day	22% 15% 6% 10% 7% 3 4 4 5% 6% 19%	2340
	11th to 20th	Day	23% 12% 5% 7% 6% 3 4 4 4 6% 24%	2405
	21st to end	Day	24% 15% 5% 9% 6% 3 5% 4 4 6% 21%	2918
June	1st to 10th	Day	35% 15% 4 7% 5% 3 4 3 4 6% 14%	2700
	11th to 20th	Day	28% 14% 4 8% 6% 3 4 4 5% 6% 18%	2700
	21st to end	Day	31% 14% 5% 7% 7% 3 5% 4 4 6% 14%	2700
July	1st to 10th	Day	28% 12% 5% 9% 5% 3 4 4 5% 6% 19%	2700
	11th to 20th	Day	32% 14% 5% 8% 5% 3 4 3 4 5% 16%	2642
	21st to end	Day	30% 12% 5% 8% 6% 4 5% 5% 5% 5% 16%	2745
August	1st to 10th	Day	28% 12% 4 7% 6% 3 3 5% 5% 7% 19%	2334
	11th to 20th	Day	24% 12% 5% 10% 8% 3 5% 4 4 5% 19%	2305
	21st to end	Day	23% 10% 4 8% 6% 5% 5% 5% 6% 7% 23%	2574
September	1st to 10th	Day	23% 10% 4 7% 5% 3 4 5% 6% 7% 26%	2135
	11th to 20th	Day	24% 9% 3 7% 7% 3 4 4 5% 6% 26%	1980
	21st to end	Day	21% 8% 3 5% 6% 4 4 5% 6% 6% 32%	1980
October	1st to 10th	Day	22% 10% 3 8% 6% 5% 5% 4 5% 8% 25%	1888
	11th to 20th	Day	25% 11% 4 9% 8% 3 5% 4 4 6% 21%	1786
	21st to end	Day	25% 12% 4 7% 6% 3 4 4 5% 7% 21%	1782
November	1st to 10th	Day	24% 11% 4 9% 6% 3 4 5% 4 6% 24%	1669
	11th to 20th	Day	24% 11% 5% 9% 7% 5% 4 4 5% 7% 19%	1520
	21st to end	Day	26% 13% 4 8% 7% 3 4 5% 5% 6% 19%	1520
December	1st to 10th	Day	27% 15% 3 9% 5% 4 4 6% 5% 6% 15%	1338
	11th to 20th	Day	18% 15% 6% 10% 8% 4 5% 4 6% 8% 17%	1668
	21st to end	Day	20% 20% 7% 10% 6% 4 5% 5% 4 5% 15%	2442
January	1st to 10th	Night	18% 13% 8% 10% 7% 4 6% 4 5% 6% 21%	4706
	11th to 20th	Night	21% 12% 8% 14% 8% 4 5% 4 4 5% 14%	4440
	21st to end	Night	17% 13% 9% 14% 8% 4 5% 4 4 5% 16%	4884
February	1st to 10th	Night	23% 13% 7% 11% 9% 4 6% 5% 4 5% 14%	2477
	11th to 20th	Night	25% 13% 6% 11% 7% 4 4 4 4 5% 16%	2251
	21st to end	Night	17% 10% 7% 12% 9% 4 6% 5% 4 6% 20%	1776
March	1st to 10th	Night	20% 14% 7% 11% 7% 4 4 4 5% 6% 19%	2126
	11th to 20th	Night	18% 11% 5% 9% 9% 3 5% 5% 6% 7% 23%	1979
	21st to end	Night	25% 14% 6% 10% 7% 3 4 4 6% 5% 17%	2178
April	1st to 10th	Night	28% 16% 5% 8% 5% 3 4 3 3 5% 21%	1805
	11th to 20th	Night	27% 12% 5% 8% 6% 3 3 4 5% 5% 23%	1598
	21st to end	Night	28% 18% 5% 7% 5% 3 4 3 2 4 20%	1620
May	1st to 10th	Night	25% 13% 5% 8% 6% 3 4 5% 4 6% 21%	1620
	11th to 20th	Night	26% 11% 4 7% 6% 3 4 5% 4 8% 21%	1484
	21st to end	Night	28% 12% 6% 9% 5% 3 4 4 4 5% 19%	1356
June	1st to 10th	Night	37% 16% 5% 6% 5% 2 3 3 4 5% 15%	1260
	11th to 20th	Night	30% 15% 6% 8% 5% 3 4 4 4 5% 17%	1260
	21st to end	Night	33% 15% 5% 8% 7% 3 4 4 3 4 14%	1260
July	1st to 10th	Night	34% 15% 5% 7% 5% 3 4 4 4 5% 14%	1260
	11th to 20th	Night	35% 15% 5% 9% 7% 3 3 3 3 4 14%	1315
	21st to end	Night	33% 14% 4 7% 7% 3 3 5% 3 4 17%	1573
August	1st to 10th	Night	29% 17% 5% 7% 6% 2 4 4 4 4 17%	1603
	11th to 20th	Night	31% 16% 5% 7% 4 2 3 3 3 5% 20%	1595
	21st to end	Night	26% 9% 3 7% 5% 3 4 4 6% 7% 24%	1782
September	1st to 10th	Night	25% 11% 3 7% 5% 3 4 4 5% 7% 27%	1822
	11th to 20th	Night	28% 10% 4 6% 6% 4 4 4 5% 4 25%	1980
	21st to end	Night	23% 6% 4 6% 5% 3 4 5% 6% 6% 32%	1980
October	1st to 10th	Night	23% 10% 3 7% 5% 3 5% 5% 5% 7% 28%	2071
	11th to 20th	Night	24% 11% 5% 7% 6% 3 4 5% 5% 6% 22%	2172
	21st to end	Night	25% 13% 5% 8% 7% 3 4 4 5% 5% 20%	2574
November	1st to 10th	Night	26% 12% 4 7% 5% 3 4 4 5% 6% 23%	2408
	11th to 20th	Night	23% 12% 5% 7% 5% 3 5% 5% 5% 6% 22%	2660
	21st to end	Night	23% 11% 3 8% 6% 4 5% 6% 5% 7% 21%	2660
December	1st to 10th	Night	24% 15% 6% 9% 6% 3 5% 4 5% 6% 16%	2840
	11th to 20th	Night	23% 15% 6% 10% 8% 4 5% 5% 5% 5% 15%	3531
	21st to end	Night	22% 15% 6% 9% 7% 3 5% 4 5% 6% 20%	5225

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	58% 11% 10% 12% 8% 1	2248
	11th to 20th	Day	68% 7% 10% 7% 7% 1	2530
	21st to end	Day	66% 7% 8% 13% 6%	2783
February	1st to 10th	Day	71% 10% 8% 6% 4 1	1686
	11th to 20th	Day	67% 8% 12% 10% 3 1	1598
	21st to end	Day	65% 8% 10% 8% 8% 2	1480
March	1st to 10th	Day	64% 8% 10% 10% 7% 1	1826
	11th to 20th	Day	60% 8% 14% 12% 6% 1	1980
	21st to end	Day	66% 7% 10% 10% 5% 2	2178
April	1st to 10th	Day	63% 6% 12% 12% 6% 1	2150
	11th to 20th	Day	61% 8% 11% 10% 8% 1	2311
	21st to end	Day	65% 7% 8% 11% 8% 1	2340
May	1st to 10th	Day	64% 8% 10% 13% 6%	2340
	11th to 20th	Day	59% 9% 11% 14% 6%	2409
	21st to end	Day	62% 9% 11% 14% 5%	2918
June	1st to 10th	Day	73% 6% 8% 9% 3	2700
	11th to 20th	Day	66% 9% 10% 11% 4	2700
	21st to end	Day	68% 11% 7% 11% 2	2700
July	1st to 10th	Day	64% 9% 9% 12% 5%	2625
	11th to 20th	Day	67% 11% 8% 10% 4	2560
	21st to end	Day	66% 12% 8% 11% 3	2592
August	1st to 10th	Day	60% 13% 11% 12% 4	2320
	11th to 20th	Day	62% 11% 10% 11% 5% 1	2305
	21st to end	Day	54% 13% 14% 16% 3	2574
September	1st to 10th	Day	53% 9% 13% 19% 7%	2135
	11th to 20th	Day	55% 8% 11% 16% 10%	1980
	21st to end	Day	49% 8% 15% 19% 8% 1	1980
October	1st to 10th	Day	55% 9% 13% 16% 6% 1	1888
	11th to 20th	Day	62% 7% 10% 15% 5%	1786
	21st to end	Day	59% 8% 12% 14% 5% 1	1782
November	1st to 10th	Day	57% 8% 16% 13% 5%	1669
	11th to 20th	Day	61% 8% 12% 13% 6% 1	1520
	21st to end	Day	64% 8% 12% 12% 5%	1520
December	1st to 10th	Day	65% 11% 9% 10% 6%	1338
	11th to 20th	Day	61% 8% 15% 11% 4 1	1667
	21st to end	Day	70% 8% 8% 11% 3	2442
January	1st to 10th	Night	60% 10% 9% 10% 7% 4	4706
	11th to 20th	Night	69% 8% 10% 8% 5%	4440
	21st to end	Night	67% 7% 12% 9% 5% 1	4884
February	1st to 10th	Night	71% 8% 8% 8% 4 1	2477
	11th to 20th	Night	67% 10% 10% 9% 4	2255
	21st to end	Night	63% 9% 11% 11% 6% 1	1776
March	1st to 10th	Night	66% 7% 9% 10% 7%	2134
	11th to 20th	Night	58% 9% 12% 13% 7%	1980
	21st to end	Night	67% 6% 9% 11% 6% 1	2178
April	1st to 10th	Night	65% 6% 8% 13% 8% 1	1805
	11th to 20th	Night	62% 6% 9% 13% 10% 1	1598
	21st to end	Night	69% 4 7% 11% 8% 1	1620
May	1st to 10th	Night	62% 8% 10% 12% 7%	1620
	11th to 20th	Night	60% 7% 10% 16% 7% 1	1485
	21st to end	Night	66% 6% 11% 13% 3	1357
June	1st to 10th	Night	74% 5% 7% 10% 3	1260
	11th to 20th	Night	69% 7% 8% 11% 4	1260
	21st to end	Night	72% 9% 8% 7% 3 1	1260
July	1st to 10th	Night	69% 9% 9% 9% 4	1226
	11th to 20th	Night	72% 8% 7% 9% 4	1273
	21st to end	Night	68% 9% 8% 11% 3	1486
August	1st to 10th	Night	67% 7% 9% 12% 4	1592
	11th to 20th	Night	66% 8% 8% 11% 5% 1	1595
	21st to end	Night	56% 8% 13% 18% 4	1782
September	1st to 10th	Night	55% 10% 10% 18% 6% 1	1822
	11th to 20th	Night	59% 8% 10% 13% 9% 1	1980
	21st to end	Night	50% 8% 14% 19% 8%	1980
October	1st to 10th	Night	55% 8% 11% 19% 7%	2071
	11th to 20th	Night	60% 9% 11% 14% 6%	2172
	21st to end	Night	63% 8% 11% 11% 6% 1	2574
November	1st to 10th	Night	60% 7% 14% 13% 5% 1	2408
	11th to 20th	Night	61% 8% 12% 13% 4 1	2660
	21st to end	Night	59% 8% 14% 12% 6% 1	2660
December	1st to 10th	Night	68% 9% 9% 10% 4	2840
	11th to 20th	Night	66% 10% 11% 8% 5%	3533
	21st to end	Night	63% 8% 12% 13% 4	5225

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	28% 18% 35% 14% 5%	370
	11th to 20th	Day	28% 18% 34% 16% 5% 1	370
	21st to end	Day	30% 16% 31% 20% 3	407
February	1st to 10th	Day	32% 17% 30% 17% 4	367
	11th to 20th	Day	29% 21% 36% 12% 3	336
	21st to end	Day	22% 19% 31% 23% 5%	280
March	1st to 10th	Day	21% 27% 34% 15% 4	340
	11th to 20th	Day	23% 15% 32% 22% 7% 1	340
	21st to end	Day	28% 18% 30% 17% 6% 1	374
April	1st to 10th	Day	31% 16% 30% 19% 4 1	433
	11th to 20th	Day	30% 15% 28% 19% 7% 1	589
	21st to end	Day	29% 14% 30% 20% 7% 1	600
May	1st to 10th	Day	29% 12% 30% 20% 7% 2	603
	11th to 20th	Day	27% 9% 29% 25% 8% 1	624
	21st to end	Day	29% 12% 26% 25% 8%	680
June	1st to 10th	Day	42% 9% 21% 20% 7% 1	630
	11th to 20th	Day	35% 7% 26% 26% 7% 1	630
	21st to end	Day	32% 9% 24% 24% 10% 1	630
July	1st to 10th	Day	32% 9% 26% 24% 8% 1	620
	11th to 20th	Day	33% 8% 19% 28% 11% 1	618
	21st to end	Day	33% 8% 23% 25% 10% 1	685
August	1st to 10th	Day	30% 7% 22% 29% 10% 1	625
	11th to 20th	Day	31% 7% 19% 27% 16%	617
	21st to end	Day	25% 6% 25% 28% 15% 1	693
September	1st to 10th	Day	25% 8% 23% 26% 16% 1	473
	11th to 20th	Day	29% 11% 26% 24% 9% 1	360
	21st to end	Day	24% 9% 30% 25% 11% 1	360
October	1st to 10th	Day	23% 12% 32% 26% 8%	360
	11th to 20th	Day	29% 8% 32% 19% 10% 2	360
	21st to end	Day	29% 18% 27% 20% 5% 1	396
November	1st to 10th	Day	24% 20% 27% 21% 7%	365
	11th to 20th	Day	30% 17% 29% 18% 6% 1	370
	21st to end	Day	32% 16% 29% 15% 6% 1	370
December	1st to 10th	Day	30% 18% 29% 15% 7%	370
	11th to 20th	Day	28% 25% 29% 14% 3	370
	21st to end	Day	26% 18% 32% 19% 5%	407
January	1st to 10th	Night	28% 21% 35% 13% 3	850
	11th to 20th	Night	32% 17% 30% 16% 4	850
	21st to end	Night	27% 19% 30% 20% 3	935
February	1st to 10th	Night	27% 22% 35% 14% 2	848
	11th to 20th	Night	31% 17% 37% 12% 3	773
	21st to end	Night	21% 16% 36% 21% 6%	592
March	1st to 10th	Night	28% 18% 34% 16% 3	694
	11th to 20th	Night	23% 14% 31% 22% 10% 1	540
	21st to end	Night	33% 14% 27% 20% 4 1	594
April	1st to 10th	Night	34% 14% 28% 16% 7% 1	540
	11th to 20th	Night	35% 13% 24% 21% 7%	534
	21st to end	Night	35% 11% 26% 19% 8% 1	540
May	1st to 10th	Night	33% 9% 24% 24% 9% 1	540
	11th to 20th	Night	32% 5% 26% 25% 10% 2	532
	21st to end	Night	32% 9% 26% 26% 7% 1	583
June	1st to 10th	Night	42% 6% 21% 24% 6% 1	540
	11th to 20th	Night	37% 8% 24% 20% 10% 1	540
	21st to end	Night	37% 7% 23% 23% 9% 1	540
July	1st to 10th	Night	34% 8% 22% 26% 8% 1	526
	11th to 20th	Night	33% 8% 23% 27% 9%	522
	21st to end	Night	36% 7% 21% 26% 9%	590
August	1st to 10th	Night	33% 5% 22% 27% 11% 2	538
	11th to 20th	Night	35% 4 20% 29% 13%	532
	21st to end	Night	28% 5% 23% 31% 12%	594
September	1st to 10th	Night	26% 6% 27% 28% 12% 1	540
	11th to 20th	Night	31% 7% 28% 25% 9% 1	540
	21st to end	Night	25% 7% 29% 27% 11% 1	540
October	1st to 10th	Night	26% 10% 30% 26% 8% 1	586
	11th to 20th	Night	29% 9% 33% 19% 8% 1	642
	21st to end	Night	31% 15% 28% 20% 6% 1	891
November	1st to 10th	Night	30% 15% 29% 19% 6%	830
	11th to 20th	Night	28% 15% 31% 19% 7% 1	850
	21st to end	Night	30% 17% 33% 16% 4	850
December	1st to 10th	Night	31% 17% 29% 18% 5%	850
	11th to 20th	Night	31% 25% 28% 13% 3	850
	21st to end	Night	24% 17% 33% 20% 6%	935

Page generated at 2024-02-07 07:11:56. Version ac07

Copyright 2024 Attilla Danko