Bay Roberts
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bay Roberts clear sky chart from 2005-11-06 to 2024-01-13.

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	22% 15% 6% 9% 6% 4 5% 4 4 6% 21%	74617
	Night	22% 15% 6% 9% 7% 3 5% 4 4 5% 20%	75130
Transparency	Day	63% 7% 10% 13% 6%	74309
	Night	64% 7% 11% 12% 5%	74973
Seeing	Day	27% 17% 29% 19% 7% 1	16961
	Night	28% 17% 31% 19% 5%	23676

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	20% 18% 8% 14% 8% 4 5% 3 3 4 12%	1326
	11th to 20th	Day	20% 19% 6% 12% 7% 3 6% 4 3 4 16%	1442
	21st to end	Day	20% 15% 8% 13% 8% 4 6% 4 4 4 14%	1584
February	1st to 10th	Day	20% 14% 7% 10% 10% 5% 7% 4 5% 4 15%	1562
	11th to 20th	Day	21% 16% 7% 12% 8% 4 5% 5% 4 5% 14%	1584
	21st to end	Day	13% 17% 9% 13% 9% 5% 5% 5% 4 4 16%	1480
March	1st to 10th	Day	17% 18% 8% 13% 8% 5% 4 4 3 4 15%	1808
	11th to 20th	Day	18% 15% 9% 12% 8% 3 4 4 4 5% 18%	1980
	21st to end	Day	23% 21% 7% 10% 7% 3 3 4 3 3 15%	2178
April	1st to 10th	Day	20% 18% 8% 11% 6% 4 4 2 5% 4 17%	2173
	11th to 20th	Day	24% 19% 6% 7% 5% 3 4 3 4 4 21%	2311
	21st to end	Day	25% 18% 5% 7% 6% 3 4 3 4 5% 20%	2340
May	1st to 10th	Day	22% 19% 6% 8% 5% 3 4 4 5% 6% 19%	2340
	11th to 20th	Day	21% 18% 5% 9% 6% 3 4 3 4 6% 23%	2492
	21st to end	Day	20% 15% 4 9% 5% 4 5% 4 5% 6% 22%	2918
June	1st to 10th	Day	31% 16% 5% 7% 6% 3 4 3 3 5% 16%	2700
	11th to 20th	Day	26% 13% 3 6% 6% 3 5% 4 4 6% 23%	2700
	21st to end	Day	23% 13% 5% 8% 6% 3 4 4 5% 7% 23%	2700
July	1st to 10th	Day	20% 12% 5% 7% 5% 3 4 4 5% 7% 27%	2700
	11th to 20th	Day	19% 12% 5% 8% 7% 3 5% 5% 5% 7% 24%	2685
	21st to end	Day	22% 11% 5% 8% 6% 4 5% 5% 5% 6% 23%	2745
August	1st to 10th	Day	25% 10% 5% 6% 6% 4 5% 4 4 7% 24%	2380
	11th to 20th	Day	22% 11% 5% 7% 7% 4 5% 5% 5% 6% 24%	2305
	21st to end	Day	20% 10% 4 8% 7% 4 5% 5% 5% 7% 25%	2574
September	1st to 10th	Day	19% 11% 3 6% 6% 3 5% 5% 5% 7% 30%	2153
	11th to 20th	Day	23% 9% 4 7% 5% 4 4 5% 4 6% 29%	1980
	21st to end	Day	18% 8% 3 6% 6% 3 5% 4 5% 8% 34%	1980
October	1st to 10th	Day	20% 12% 4 8% 5% 3 4 4 5% 8% 28%	1890
	11th to 20th	Day	24% 15% 4 8% 7% 3 5% 4 5% 4 22%	1758
	21st to end	Day	25% 16% 4 7% 7% 4 5% 4 4 5% 18%	1782
November	1st to 10th	Day	21% 14% 5% 9% 6% 3 5% 3 5% 5% 23%	1644
	11th to 20th	Day	22% 16% 6% 9% 6% 3 5% 3 4 7% 18%	1520
	21st to end	Day	23% 19% 6% 9% 7% 3 5% 3 3 5% 17%	1463
December	1st to 10th	Day	22% 18% 7% 12% 6% 3 4 4 3 5% 15%	1330
	11th to 20th	Day	24% 18% 7% 10% 6% 3 5% 4 3 4 15%	1668
	21st to end	Day	19% 20% 8% 11% 7% 4 4 4 5% 4 13%	2442
January	1st to 10th	Night	19% 17% 9% 11% 9% 4 5% 4 5% 4 14%	2839
	11th to 20th	Night	21% 17% 6% 11% 8% 4 5% 4 4 5% 14%	2578
	21st to end	Night	19% 15% 8% 11% 9% 3 5% 5% 5% 4 16%	2772
February	1st to 10th	Night	19% 15% 7% 13% 10% 4 5% 4 4 5% 14%	2397
	11th to 20th	Night	22% 13% 7% 11% 10% 4 6% 4 4 4 15%	2259
	21st to end	Night	14% 16% 8% 12% 8% 4 5% 4 5% 5% 18%	1776
March	1st to 10th	Night	17% 14% 8% 13% 8% 4 4 5% 4 5% 18%	2139
	11th to 20th	Night	14% 14% 6% 12% 8% 4 6% 4 5% 6% 20%	1979
	21st to end	Night	25% 18% 8% 10% 7% 2 4 3 4 3 15%	2178
April	1st to 10th	Night	22% 18% 6% 9% 7% 2 4 3 4 4 19%	1783
	11th to 20th	Night	24% 14% 5% 8% 7% 3 4 3 4 4 24%	1598
	21st to end	Night	27% 20% 5% 8% 5% 3 3 3 3 4 21%	1620
May	1st to 10th	Night	25% 15% 6% 7% 6% 3 5% 5% 4 6% 17%	1620
	11th to 20th	Night	25% 14% 3 7% 5% 3 5% 4 5% 6% 23%	1398
	21st to end	Night	25% 12% 4 8% 7% 4 6% 4 5% 6% 19%	1356
June	1st to 10th	Night	27% 15% 5% 7% 6% 3 5% 4 4 4 18%	1260
	11th to 20th	Night	25% 13% 4 7% 6% 3 4 5% 5% 7% 21%	1260
	21st to end	Night	24% 13% 4 8% 6% 3 5% 4 4 5% 22%	1260
July	1st to 10th	Night	20% 10% 5% 10% 7% 4 5% 4 5% 7% 22%	1260
	11th to 20th	Night	21% 14% 6% 8% 6% 4 6% 5% 5% 5% 22%	1272
	21st to end	Night	23% 14% 5% 8% 6% 4 5% 5% 4 6% 22%	1573
August	1st to 10th	Night	23% 10% 4 8% 5% 4 4 5% 5% 7% 24%	1558
	11th to 20th	Night	24% 10% 5% 8% 6% 4 4 4 4 6% 24%	1595
	21st to end	Night	23% 9% 3 7% 5% 3 4 4 7% 8% 27%	1782
September	1st to 10th	Night	19% 11% 5% 6% 5% 4 4 5% 5% 6% 30%	1803
	11th to 20th	Night	24% 11% 3 8% 5% 3 4 4 4 6% 28%	1980
	21st to end	Night	20% 11% 3 7% 5% 3 4 4 4 7% 32%	1980
October	1st to 10th	Night	21% 11% 4 9% 6% 3 4 5% 4 7% 26%	2070
	11th to 20th	Night	25% 15% 3 6% 6% 3 5% 4 5% 7% 23%	2200
	21st to end	Night	24% 17% 5% 8% 5% 3 5% 4 3 5% 20%	2574
November	1st to 10th	Night	22% 14% 5% 8% 7% 3 5% 4 4 6% 23%	2432
	11th to 20th	Night	22% 15% 6% 9% 6% 4 4 4 4 6% 20%	2660
	21st to end	Night	19% 17% 5% 10% 7% 3 5% 5% 5% 5% 20%	2713
December	1st to 10th	Night	20% 19% 6% 10% 7% 4 4 4 4 5% 17%	2850
	11th to 20th	Night	29% 17% 6% 12% 7% 3 4 4 3 4 12%	3531
	21st to end	Night	21% 17% 7% 11% 6% 3 5% 4 4 4 19%	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	74% 7% 8% 8% 4	1327
	11th to 20th	Day	69% 8% 10% 8% 4 1	1442
	21st to end	Day	72% 6% 7% 8% 6% 1	1584
February	1st to 10th	Day	70% 8% 8% 7% 6% 1	1562
	11th to 20th	Day	70% 7% 9% 9% 4 1	1591
	21st to end	Day	70% 6% 9% 7% 6% 2	1480
March	1st to 10th	Day	70% 6% 9% 10% 5% 1	1813
	11th to 20th	Day	67% 7% 9% 12% 5%	1980
	21st to end	Day	73% 5% 7% 10% 4 1	2178
April	1st to 10th	Day	68% 6% 8% 12% 5% 1	2173
	11th to 20th	Day	66% 6% 7% 12% 9% 1	2311
	21st to end	Day	67% 5% 8% 11% 8% 1	2340
May	1st to 10th	Day	65% 6% 9% 12% 7% 1	2340
	11th to 20th	Day	62% 8% 11% 13% 6%	2496
	21st to end	Day	59% 8% 10% 16% 6%	2918
June	1st to 10th	Day	71% 5% 7% 12% 4 1	2700
	11th to 20th	Day	61% 8% 13% 12% 6%	2700
	21st to end	Day	61% 8% 11% 15% 6%	2700
July	1st to 10th	Day	53% 8% 14% 18% 7%	2625
	11th to 20th	Day	56% 10% 12% 15% 6%	2603
	21st to end	Day	58% 10% 14% 13% 4	2592
August	1st to 10th	Day	59% 7% 11% 17% 5%	2366
	11th to 20th	Day	58% 8% 11% 16% 6%	2305
	21st to end	Day	55% 9% 15% 17% 4	2574
September	1st to 10th	Day	52% 7% 12% 20% 8%	2153
	11th to 20th	Day	53% 6% 12% 18% 10%	1980
	21st to end	Day	48% 8% 16% 21% 8%	1980
October	1st to 10th	Day	55% 6% 13% 16% 9% 1	1890
	11th to 20th	Day	65% 6% 10% 14% 5%	1758
	21st to end	Day	67% 7% 7% 13% 5% 1	1782
November	1st to 10th	Day	62% 6% 14% 12% 5%	1644
	11th to 20th	Day	65% 8% 10% 12% 5%	1520
	21st to end	Day	68% 5% 12% 9% 5%	1463
December	1st to 10th	Day	70% 7% 10% 10% 4	1330
	11th to 20th	Day	70% 7% 9% 9% 4	1667
	21st to end	Day	73% 6% 9% 10% 2	2442
January	1st to 10th	Night	72% 8% 7% 8% 5% 1	2839
	11th to 20th	Night	70% 9% 9% 8% 4	2578
	21st to end	Night	68% 8% 9% 10% 4	2772
February	1st to 10th	Night	71% 7% 9% 8% 5% 1	2397
	11th to 20th	Night	69% 8% 9% 10% 3	2263
	21st to end	Night	69% 6% 9% 9% 6%	1776
March	1st to 10th	Night	66% 7% 9% 11% 6% 1	2147
	11th to 20th	Night	61% 7% 12% 14% 6% 1	1980
	21st to end	Night	73% 5% 7% 9% 5% 1	2178
April	1st to 10th	Night	65% 6% 8% 12% 7% 1	1783
	11th to 20th	Night	63% 6% 8% 13% 8% 1	1598
	21st to end	Night	66% 6% 8% 12% 8%	1620
May	1st to 10th	Night	66% 7% 10% 11% 6%	1620
	11th to 20th	Night	60% 7% 10% 17% 7%	1399
	21st to end	Night	63% 8% 11% 13% 5%	1357
June	1st to 10th	Night	68% 6% 8% 12% 5%	1260
	11th to 20th	Night	61% 8% 13% 13% 5%	1260
	21st to end	Night	59% 8% 14% 14% 4	1260
July	1st to 10th	Night	56% 10% 14% 15% 5%	1226
	11th to 20th	Night	58% 11% 12% 14% 4	1230
	21st to end	Night	60% 9% 10% 16% 4	1486
August	1st to 10th	Night	56% 8% 16% 14% 5%	1547
	11th to 20th	Night	58% 8% 14% 15% 6%	1595
	21st to end	Night	52% 10% 14% 20% 4	1782
September	1st to 10th	Night	51% 9% 12% 20% 7% 1	1803
	11th to 20th	Night	56% 6% 13% 14% 9%	1980
	21st to end	Night	52% 7% 14% 19% 8%	1980
October	1st to 10th	Night	57% 8% 11% 18% 6% 1	2070
	11th to 20th	Night	61% 7% 13% 13% 6%	2200
	21st to end	Night	65% 6% 11% 11% 6% 1	2574
November	1st to 10th	Night	61% 7% 13% 12% 5%	2432
	11th to 20th	Night	64% 8% 11% 12% 3 1	2660
	21st to end	Night	63% 7% 14% 11% 5% 1	2713
December	1st to 10th	Night	69% 7% 8% 11% 4	2850
	11th to 20th	Night	75% 6% 8% 6% 4	3533
	21st to end	Night	66% 7% 11% 13% 2	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	29% 23% 32% 12% 3 1	370
	11th to 20th	Day	27% 26% 31% 13% 3 1	349
	21st to end	Day	27% 25% 33% 13% 2	374
February	1st to 10th	Day	27% 25% 30% 15% 3	340
	11th to 20th	Day	27% 31% 30% 10% 2	336
	21st to end	Day	21% 30% 31% 15% 3	280
March	1st to 10th	Day	28% 28% 31% 9% 4 1	340
	11th to 20th	Day	22% 24% 31% 17% 3 3	340
	21st to end	Day	30% 23% 28% 13% 5% 1	374
April	1st to 10th	Day	30% 21% 29% 14% 4	443
	11th to 20th	Day	32% 19% 27% 15% 6% 1	589
	21st to end	Day	32% 17% 30% 17% 5%	600
May	1st to 10th	Day	29% 20% 26% 17% 6% 2	603
	11th to 20th	Day	24% 15% 31% 20% 7% 2	624
	21st to end	Day	26% 18% 31% 19% 5% 1	680
June	1st to 10th	Day	40% 10% 24% 18% 6% 1	630
	11th to 20th	Day	33% 10% 27% 21% 7% 1	630
	21st to end	Day	26% 9% 29% 25% 8% 3	630
July	1st to 10th	Day	26% 8% 34% 21% 9% 2	620
	11th to 20th	Day	24% 7% 32% 25% 10% 1	618
	21st to end	Day	25% 10% 29% 25% 10% 1	685
August	1st to 10th	Day	25% 8% 28% 25% 10% 3	625
	11th to 20th	Day	23% 9% 29% 27% 11% 1	617
	21st to end	Day	22% 11% 25% 27% 13% 1	693
September	1st to 10th	Day	21% 10% 27% 29% 11% 2	483
	11th to 20th	Day	28% 14% 28% 23% 7% 1	360
	21st to end	Day	20% 17% 33% 20% 9% 1	360
October	1st to 10th	Day	24% 13% 33% 23% 6% 1	360
	11th to 20th	Day	30% 16% 26% 17% 10% 1	360
	21st to end	Day	30% 23% 25% 16% 5% 2	396
November	1st to 10th	Day	27% 23% 28% 18% 4 1	365
	11th to 20th	Day	29% 22% 28% 16% 6% 1	370
	21st to end	Day	31% 29% 26% 10% 4	370
December	1st to 10th	Day	27% 23% 28% 17% 5%	370
	11th to 20th	Day	32% 26% 28% 10% 2	370
	21st to end	Day	27% 21% 33% 15% 4 1	407
January	1st to 10th	Night	28% 21% 34% 13% 4	850
	11th to 20th	Night	28% 21% 34% 12% 4	814
	21st to end	Night	26% 22% 33% 16% 2	880
February	1st to 10th	Night	26% 27% 33% 12% 1	800
	11th to 20th	Night	31% 23% 33% 11% 2	777
	21st to end	Night	23% 23% 31% 19% 4	592
March	1st to 10th	Night	23% 25% 34% 14% 4	707
	11th to 20th	Night	23% 18% 30% 23% 6%	540
	21st to end	Night	34% 18% 28% 17% 3	594
April	1st to 10th	Night	27% 19% 31% 15% 7% 1	540
	11th to 20th	Night	30% 17% 29% 19% 4	534
	21st to end	Night	34% 13% 31% 17% 4 1	540
May	1st to 10th	Night	31% 12% 29% 21% 6% 1	540
	11th to 20th	Night	30% 10% 31% 20% 8% 1	532
	21st to end	Night	29% 13% 32% 22% 4 1	583
June	1st to 10th	Night	34% 10% 27% 22% 6%	540
	11th to 20th	Night	31% 9% 26% 26% 7% 1	540
	21st to end	Night	27% 9% 33% 22% 7% 1	540
July	1st to 10th	Night	24% 7% 38% 25% 6% 1	526
	11th to 20th	Night	25% 6% 37% 26% 6%	522
	21st to end	Night	25% 8% 34% 26% 7%	590
August	1st to 10th	Night	29% 5% 28% 29% 9%	538
	11th to 20th	Night	26% 6% 29% 32% 7%	532
	21st to end	Night	24% 10% 29% 29% 8%	594
September	1st to 10th	Night	22% 10% 31% 29% 8% 1	540
	11th to 20th	Night	29% 10% 30% 25% 5% 1	540
	21st to end	Night	25% 13% 29% 25% 7%	540
October	1st to 10th	Night	25% 14% 33% 22% 6%	585
	11th to 20th	Night	31% 14% 27% 21% 8%	670
	21st to end	Night	32% 19% 25% 19% 5%	891
November	1st to 10th	Night	28% 21% 30% 17% 4	830
	11th to 20th	Night	29% 18% 29% 19% 5%	850
	21st to end	Night	26% 24% 32% 13% 4	850
December	1st to 10th	Night	27% 23% 28% 16% 5%	850
	11th to 20th	Night	34% 25% 28% 11% 2	850
	21st to end	Night	27% 21% 30% 18% 3 1	935

Page generated at 2024-01-10 21:35:25. Version ac07

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