Gull Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gull Bay clear sky chart from 2005-11-06 to 2024-02-05.

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	15% 11% 4 8% 7% 4 5% 5% 5% 7% 29%	78319
	Night	14% 12% 5% 9% 8% 4 6% 5% 5% 6% 27%	80570
Transparency	Day	53% 8% 12% 18% 8% 1	78020
	Night	57% 8% 12% 17% 7% 1	80403
Seeing	Day	18% 10% 30% 28% 12% 3	14777
	Night	19% 8% 29% 31% 11% 1	24541

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	8% 12% 6% 12% 12% 8% 7% 7% 7% 6% 14%	2527
	11th to 20th	Day	5% 11% 7% 12% 12% 9% 9% 7% 5% 5% 18%	2530
	21st to end	Day	12% 18% 10% 13% 8% 4 6% 5% 6% 5% 13%	2783
February	1st to 10th	Day	7% 11% 5% 11% 8% 6% 8% 7% 6% 6% 25%	1508
	11th to 20th	Day	7% 12% 6% 9% 8% 4 6% 6% 7% 7% 28%	1574
	21st to end	Day	5% 10% 6% 13% 8% 5% 6% 5% 6% 6% 30%	1480
March	1st to 10th	Day	10% 11% 5% 11% 8% 5% 5% 4 5% 5% 31%	1798
	11th to 20th	Day	12% 11% 7% 9% 6% 3 5% 4 5% 6% 32%	1876
	21st to end	Day	14% 10% 4 9% 7% 3 4 4 4 6% 34%	2362
April	1st to 10th	Day	12% 12% 6% 9% 7% 4 3 4 5% 5% 33%	2160
	11th to 20th	Day	18% 11% 4 7% 5% 3 4 4 4 7% 32%	2164
	21st to end	Day	16% 11% 3 7% 5% 3 4 4 6% 6% 35%	2438
May	1st to 10th	Day	20% 12% 4 7% 6% 4 5% 4 5% 6% 28%	2520
	11th to 20th	Day	18% 11% 4 6% 5% 3 5% 5% 6% 6% 32%	2479
	21st to end	Day	21% 6% 3 5% 5% 3 4 5% 6% 8% 36%	2773
June	1st to 10th	Day	20% 7% 3 6% 7% 3 4 4 5% 7% 34%	2700
	11th to 20th	Day	15% 6% 3 6% 5% 4 6% 4 6% 9% 37%	2838
	21st to end	Day	16% 6% 2 6% 6% 3 5% 5% 7% 7% 36%	2880
July	1st to 10th	Day	14% 6% 3 5% 5% 4 5% 5% 6% 8% 40%	2756
	11th to 20th	Day	13% 5% 2 6% 6% 4 4 6% 6% 9% 38%	2520
	21st to end	Day	13% 5% 2 6% 5% 4 6% 7% 7% 8% 37%	2743
August	1st to 10th	Day	10% 6% 2 5% 7% 5% 6% 6% 7% 9% 37%	2507
	11th to 20th	Day	12% 6% 2 5% 4 3 5% 5% 6% 7% 44%	2479
	21st to end	Day	15% 7% 3 6% 6% 3 5% 4 5% 7% 38%	2405
September	1st to 10th	Day	16% 6% 2 6% 6% 3 6% 5% 6% 7% 38%	2160
	11th to 20th	Day	23% 8% 3 5% 4 2 5% 5% 6% 7% 31%	2110
	21st to end	Day	21% 9% 3 7% 5% 3 4 3 4 6% 33%	1980
October	1st to 10th	Day	20% 16% 5% 6% 6% 2 4 3 4 6% 27%	1808
	11th to 20th	Day	20% 18% 4 7% 6% 3 4 5% 4 6% 22%	1715
	21st to end	Day	19% 18% 4 10% 7% 5% 4 4 4 5% 19%	1782
November	1st to 10th	Day	16% 15% 6% 11% 8% 5% 4 5% 5% 5% 20%	1608
	11th to 20th	Day	18% 17% 8% 11% 11% 4 5% 4 4 5% 13%	1520
	21st to end	Day	17% 16% 7% 15% 9% 4 5% 4 4 4 16%	1372
December	1st to 10th	Day	10% 14% 7% 13% 8% 5% 5% 7% 7% 6% 19%	1330
	11th to 20th	Day	12% 14% 7% 9% 8% 6% 7% 7% 6% 6% 17%	1671
	21st to end	Day	19% 20% 7% 8% 9% 4 5% 4 5% 4 15%	2463
January	1st to 10th	Night	8% 16% 6% 13% 9% 6% 7% 6% 6% 7% 16%	4428
	11th to 20th	Night	7% 10% 7% 14% 14% 8% 9% 7% 5% 5% 13%	4440
	21st to end	Night	10% 17% 8% 12% 10% 5% 6% 6% 6% 6% 15%	4884
February	1st to 10th	Night	7% 11% 6% 9% 7% 5% 10% 7% 6% 7% 25%	2546
	11th to 20th	Night	8% 12% 5% 8% 8% 4 10% 6% 6% 7% 26%	2273
	21st to end	Night	5% 14% 6% 10% 8% 5% 7% 7% 5% 5% 27%	1776
March	1st to 10th	Night	8% 9% 4 10% 9% 5% 9% 6% 6% 6% 28%	2149
	11th to 20th	Night	11% 13% 4 9% 7% 4 6% 4 4 5% 33%	2101
	21st to end	Night	14% 10% 4 7% 6% 3 5% 4 4 6% 36%	1993
April	1st to 10th	Night	14% 12% 5% 9% 7% 4 5% 4 4 6% 31%	1800
	11th to 20th	Night	18% 12% 4 7% 6% 3 5% 4 5% 6% 31%	1744
	21st to end	Night	15% 9% 4 5% 5% 3 5% 3 6% 6% 38%	1518
May	1st to 10th	Night	17% 11% 4 7% 6% 3 3 5% 5% 5% 33%	1440
	11th to 20th	Night	18% 8% 3 5% 4 3 3 5% 5% 7% 40%	1416
	21st to end	Night	21% 7% 4 5% 5% 4 5% 5% 5% 6% 34%	1502
June	1st to 10th	Night	19% 6% 2 6% 5% 4 5% 4 6% 6% 36%	1260
	11th to 20th	Night	14% 6% 3 5% 5% 4 5% 4 4 7% 42%	1116
	21st to end	Night	17% 6% 3 4 4 3 5% 6% 5% 8% 40%	1080
July	1st to 10th	Night	10% 5% 2 5% 6% 3 4 5% 6% 8% 46%	1196
	11th to 20th	Night	12% 5% 2 5% 5% 3 5% 4 6% 9% 45%	1440
	21st to end	Night	9% 4 2 4 6% 3 5% 4 6% 9% 47%	1575
August	1st to 10th	Night	10% 5% 3 5% 6% 3 5% 4 6% 8% 43%	1432
	11th to 20th	Night	14% 5% 2 4 5% 4 3 4 6% 7% 46%	1422
	21st to end	Night	13% 5% 2 5% 5% 3 4 4 5% 9% 44%	1948
September	1st to 10th	Night	15% 5% 2 4 4 3 4 5% 6% 8% 46%	1800
	11th to 20th	Night	20% 6% 3 4 5% 4 4 5% 5% 6% 39%	1832
	21st to end	Night	24% 7% 3 5% 5% 2 3 4 5% 7% 34%	1980
October	1st to 10th	Night	21% 10% 4 5% 5% 3 4 5% 5% 6% 32%	2150
	11th to 20th	Night	19% 15% 4 7% 6% 4 5% 5% 5% 6% 25%	2245
	21st to end	Night	20% 17% 4 8% 6% 3 4 5% 5% 6% 21%	2574
November	1st to 10th	Night	20% 15% 6% 10% 6% 3 5% 4 4 5% 21%	2467
	11th to 20th	Night	18% 16% 6% 13% 8% 3 6% 5% 4 6% 16%	2660
	21st to end	Night	16% 17% 6% 14% 8% 4 5% 5% 4 5% 16%	2807
December	1st to 10th	Night	10% 15% 7% 13% 11% 5% 6% 5% 6% 6% 17%	2850
	11th to 20th	Night	12% 14% 6% 12% 9% 5% 6% 6% 7% 5% 18%	3526
	21st to end	Night	17% 20% 6% 12% 10% 3 5% 5% 4 4 14%	5200

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	67% 9% 8% 12% 3	2528
	11th to 20th	Day	67% 6% 9% 15% 3	2530
	21st to end	Day	70% 7% 9% 8% 5%	2783
February	1st to 10th	Day	57% 7% 11% 17% 7% 2	1508
	11th to 20th	Day	53% 6% 11% 20% 9%	1583
	21st to end	Day	53% 4 11% 17% 13% 1	1480
March	1st to 10th	Day	53% 6% 10% 18% 11% 2	1800
	11th to 20th	Day	51% 7% 10% 19% 11% 2	1876
	21st to end	Day	53% 4 10% 18% 13% 2	2362
April	1st to 10th	Day	52% 5% 10% 19% 11% 2	2160
	11th to 20th	Day	52% 5% 10% 20% 12% 1	2164
	21st to end	Day	48% 7% 10% 18% 15% 2	2438
May	1st to 10th	Day	56% 6% 10% 19% 8% 1	2520
	11th to 20th	Day	49% 8% 12% 20% 10% 1	2483
	21st to end	Day	45% 8% 12% 20% 13% 2	2773
June	1st to 10th	Day	49% 7% 12% 18% 14% 1	2700
	11th to 20th	Day	43% 8% 11% 23% 13% 2	2838
	21st to end	Day	43% 9% 15% 23% 9%	2880
July	1st to 10th	Day	39% 8% 13% 27% 12% 1	2683
	11th to 20th	Day	40% 9% 14% 28% 10%	2445
	21st to end	Day	41% 11% 13% 26% 9% 1	2591
August	1st to 10th	Day	39% 12% 17% 25% 6% 1	2492
	11th to 20th	Day	37% 9% 18% 26% 10%	2479
	21st to end	Day	42% 9% 16% 23% 10% 1	2405
September	1st to 10th	Day	44% 8% 13% 25% 10% 1	2160
	11th to 20th	Day	50% 9% 16% 20% 5%	2110
	21st to end	Day	52% 7% 14% 22% 5%	1980
October	1st to 10th	Day	59% 6% 11% 20% 4	1808
	11th to 20th	Day	64% 7% 11% 15% 2	1715
	21st to end	Day	67% 6% 11% 12% 3	1782
November	1st to 10th	Day	66% 7% 11% 11% 4	1608
	11th to 20th	Day	74% 7% 10% 6% 3	1520
	21st to end	Day	71% 9% 12% 4 4	1372
December	1st to 10th	Day	64% 11% 13% 9% 2	1330
	11th to 20th	Day	62% 10% 11% 10% 5% 1	1671
	21st to end	Day	72% 6% 8% 10% 3	2463
January	1st to 10th	Night	65% 9% 10% 12% 3	4428
	11th to 20th	Night	71% 7% 10% 10% 2	4440
	21st to end	Night	68% 9% 10% 9% 4	4884
February	1st to 10th	Night	56% 7% 11% 18% 8%	2546
	11th to 20th	Night	56% 6% 11% 19% 8%	2274
	21st to end	Night	56% 6% 11% 17% 10% 1	1776
March	1st to 10th	Night	54% 6% 12% 18% 10% 1	2160
	11th to 20th	Night	53% 6% 10% 19% 11% 2	2102
	21st to end	Night	49% 5% 9% 20% 15% 2	1993
April	1st to 10th	Night	53% 7% 8% 19% 11% 2	1800
	11th to 20th	Night	54% 5% 9% 19% 11% 2	1744
	21st to end	Night	47% 5% 10% 20% 14% 4	1518
May	1st to 10th	Night	52% 6% 11% 20% 10% 1	1440
	11th to 20th	Night	45% 6% 12% 23% 12% 2	1417
	21st to end	Night	49% 8% 10% 17% 13% 2	1503
June	1st to 10th	Night	46% 7% 13% 21% 11% 2	1260
	11th to 20th	Night	41% 7% 9% 27% 15% 1	1116
	21st to end	Night	41% 9% 15% 23% 11% 1	1080
July	1st to 10th	Night	33% 9% 14% 28% 15% 1	1160
	11th to 20th	Night	34% 9% 12% 33% 12%	1392
	21st to end	Night	34% 9% 17% 30% 10% 1	1487
August	1st to 10th	Night	37% 9% 16% 30% 7% 1	1423
	11th to 20th	Night	37% 8% 14% 29% 12%	1422
	21st to end	Night	37% 8% 19% 26% 9% 1	1948
September	1st to 10th	Night	36% 9% 15% 29% 11% 1	1800
	11th to 20th	Night	44% 9% 17% 25% 4	1832
	21st to end	Night	49% 7% 14% 24% 6%	1980
October	1st to 10th	Night	53% 7% 15% 19% 6%	2150
	11th to 20th	Night	60% 9% 13% 15% 3 1	2245
	21st to end	Night	63% 9% 12% 14% 2	2574
November	1st to 10th	Night	65% 8% 11% 12% 3	2467
	11th to 20th	Night	70% 7% 11% 9% 2	2660
	21st to end	Night	71% 9% 11% 7% 3	2807
December	1st to 10th	Night	66% 10% 12% 9% 3	2850
	11th to 20th	Night	63% 10% 12% 11% 4	3525
	21st to end	Night	72% 7% 7% 11% 2	5200

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	15% 10% 34% 31% 9% 1	270
	11th to 20th	Day	11% 8% 38% 30% 11% 2	270
	21st to end	Day	14% 6% 38% 29% 10% 3	297
February	1st to 10th	Day	10% 13% 35% 33% 8% 1	252
	11th to 20th	Day	12% 13% 41% 25% 7% 3	240
	21st to end	Day	6% 15% 46% 26% 6% 1	198
March	1st to 10th	Day	13% 13% 33% 30% 9% 3	240
	11th to 20th	Day	15% 19% 32% 23% 10% 1	240
	21st to end	Day	16% 10% 28% 32% 11% 3	448
April	1st to 10th	Day	17% 10% 32% 28% 12% 1	420
	11th to 20th	Day	25% 12% 23% 25% 15% 2	412
	21st to end	Day	19% 8% 31% 28% 11% 3	518
May	1st to 10th	Day	25% 8% 29% 25% 12% 2	603
	11th to 20th	Day	19% 8% 35% 24% 12% 2	625
	21st to end	Day	23% 7% 30% 30% 8% 2	679
June	1st to 10th	Day	20% 6% 33% 28% 11% 2	630
	11th to 20th	Day	16% 8% 32% 28% 13% 3	630
	21st to end	Day	17% 6% 30% 30% 13% 4	630
July	1st to 10th	Day	14% 7% 28% 34% 14% 3	621
	11th to 20th	Day	12% 6% 31% 29% 18% 4	618
	21st to end	Day	12% 8% 24% 34% 18% 6%	684
August	1st to 10th	Day	12% 8% 26% 35% 15% 4	626
	11th to 20th	Day	15% 6% 22% 31% 21% 4	615
	21st to end	Day	19% 10% 25% 27% 17% 3	509
September	1st to 10th	Day	18% 8% 30% 26% 16% 3	450
	11th to 20th	Day	27% 10% 21% 27% 14% 1	450
	21st to end	Day	25% 11% 24% 29% 9% 2	450
October	1st to 10th	Day	26% 13% 27% 22% 11% 2	278
	11th to 20th	Day	21% 14% 36% 18% 10% 1	270
	21st to end	Day	31% 17% 34% 14% 4	297
November	1st to 10th	Day	21% 17% 30% 22% 10%	270
	11th to 20th	Day	28% 19% 32% 19% 2 1	270
	21st to end	Day	22% 20% 33% 19% 6% 1	200
December	1st to 10th	Day	19% 12% 34% 27% 5% 3	180
	11th to 20th	Day	21% 13% 37% 21% 9%	180
	21st to end	Day	20% 14% 30% 23% 11% 2	207
January	1st to 10th	Night	15% 8% 37% 31% 8%	950
	11th to 20th	Night	18% 7% 31% 31% 11% 2	950
	21st to end	Night	16% 6% 32% 33% 12% 2	1045
February	1st to 10th	Night	13% 6% 33% 36% 11% 1	923
	11th to 20th	Night	15% 7% 33% 29% 15% 1	879
	21st to end	Night	11% 7% 34% 34% 12% 1	592
March	1st to 10th	Night	12% 8% 35% 31% 12% 2	720
	11th to 20th	Night	18% 10% 32% 31% 9% 1	662
	21st to end	Night	19% 9% 26% 31% 12% 4	594
April	1st to 10th	Night	19% 9% 26% 34% 11% 1	540
	11th to 20th	Night	25% 8% 26% 30% 11%	533
	21st to end	Night	17% 7% 27% 33% 14% 2	540
May	1st to 10th	Night	21% 5% 27% 35% 10% 1	540
	11th to 20th	Night	21% 6% 29% 31% 11% 2	531
	21st to end	Night	23% 8% 22% 38% 9%	535
June	1st to 10th	Night	21% 4 26% 35% 13% 1	360
	11th to 20th	Night	17% 6% 26% 37% 14%	360
	21st to end	Night	18% 5% 25% 35% 15% 1	360
July	1st to 10th	Night	13% 3 28% 41% 13% 2	439
	11th to 20th	Night	11% 6% 26% 39% 16% 2	522
	21st to end	Night	10% 3 25% 39% 21% 2	591
August	1st to 10th	Night	14% 4 25% 39% 16% 1	537
	11th to 20th	Night	14% 6% 21% 35% 22% 3	534
	21st to end	Night	14% 5% 30% 31% 17% 2	594
September	1st to 10th	Night	16% 5% 23% 36% 18% 1	540
	11th to 20th	Night	22% 7% 31% 27% 13%	572
	21st to end	Night	28% 7% 23% 32% 10% 2	720
October	1st to 10th	Night	26% 10% 27% 26% 10% 1	720
	11th to 20th	Night	27% 11% 29% 24% 9%	720
	21st to end	Night	28% 10% 29% 24% 9% 1	792
November	1st to 10th	Night	27% 12% 28% 24% 8% 1	801
	11th to 20th	Night	25% 12% 29% 24% 8% 2	950
	21st to end	Night	25% 16% 31% 23% 5%	950
December	1st to 10th	Night	17% 13% 38% 21% 10% 2	950
	11th to 20th	Night	20% 11% 34% 25% 8% 1	950
	21st to end	Night	25% 8% 28% 27% 9% 2	1045

Page generated at 2024-02-02 05:20:33. Version ac07

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