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 2026-07-01.

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	13% 11% 4 9% 5% 5% 5% 4 5% 7% 32%	138784
	Night	12% 12% 4 11% 6% 6% 5% 4 5% 6% 28%	133865
Transparency	Day	50% 7% 12% 21% 10% 1	142158
	Night	55% 6% 11% 18% 8% 1	138577
Seeing	Day	18% 11% 31% 26% 11% 2	18124
	Night	19% 9% 30% 30% 11% 1	27689

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	6% 14% 7% 18% 8% 9% 7% 5% 6% 6% 16%	4691
	11th to 20th	Day	5% 15% 8% 14% 9% 10% 9% 8% 7% 4 11%	4679
	21st to end	Day	7% 12% 7% 14% 8% 8% 7% 5% 8% 6% 18%	5156
February	1st to 10th	Day	7% 14% 5% 13% 6% 8% 7% 6% 6% 6% 22%	1722
	11th to 20th	Day	7% 13% 5% 12% 7% 7% 5% 5% 7% 6% 27%	1844
	21st to end	Day	6% 12% 5% 14% 7% 7% 5% 4 6% 6% 28%	1730
March	1st to 10th	Day	14% 14% 5% 11% 5% 5% 4 3 4 5% 30%	4578
	11th to 20th	Day	9% 15% 7% 12% 6% 7% 5% 3 4 5% 28%	4826
	21st to end	Day	15% 17% 4 9% 6% 5% 4 3 4 5% 29%	6086
April	1st to 10th	Day	12% 13% 5% 10% 6% 4 3 3 5% 5% 34%	2520
	11th to 20th	Day	18% 12% 4 8% 5% 4 4 3 5% 7% 31%	2530
	21st to end	Day	17% 13% 3 7% 4 4 4 3 5% 6% 33%	2845
May	1st to 10th	Day	14% 12% 4 8% 5% 4 5% 3 5% 6% 33%	8241
	11th to 20th	Day	19% 9% 3 6% 4 4 4 3 5% 6% 37%	8222
	21st to end	Day	13% 7% 2 5% 4 4 4 3 5% 8% 45%	9235
June	1st to 10th	Day	18% 8% 3 8% 6% 4 4 3 5% 7% 35%	3150
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 8% 35%	3312
	21st to end	Day	16% 6% 2 7% 5% 5% 5% 4 7% 8% 35%	3360
July	1st to 10th	Day	13% 5% 2 6% 5% 4 4 4 6% 8% 43%	6916
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	6360
	21st to end	Day	10% 7% 2 7% 5% 5% 6% 5% 7% 9% 36%	6926
August	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 4 5% 8% 36%	4563
	11th to 20th	Day	11% 5% 1 4 4 4 5% 4 6% 7% 49%	4496
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 3 6% 9% 42%	4342
September	1st to 10th	Day	16% 6% 2 7% 5% 4 6% 4 6% 6% 38%	2400
	11th to 20th	Day	21% 9% 3 6% 4 3 5% 4 6% 8% 32%	2344
	21st to end	Day	19% 9% 3 7% 4 4 3 3 5% 6% 36%	2200
October	1st to 10th	Day	18% 15% 4 8% 5% 4 4 3 4 6% 28%	2008
	11th to 20th	Day	18% 18% 4 9% 5% 4 5% 3 4 6% 22%	1905
	21st to end	Day	18% 18% 4 10% 6% 6% 4 3 4 6% 21%	1980
November	1st to 10th	Day	15% 16% 5% 12% 7% 6% 4 4 5% 6% 21%	1780
	11th to 20th	Day	18% 19% 7% 13% 8% 6% 4 3 5% 5% 14%	1680
	21st to end	Day	16% 18% 7% 17% 7% 5% 4 3 4 5% 15%	1516
December	1st to 10th	Day	10% 18% 8% 17% 10% 7% 4 4 5% 4 14%	2350
	11th to 20th	Day	10% 13% 5% 14% 7% 9% 7% 5% 6% 6% 17%	2691
	21st to end	Day	14% 21% 6% 13% 6% 6% 5% 3 4 5% 15%	3600
January	1st to 10th	Night	6% 15% 6% 16% 8% 9% 7% 4 5% 5% 20%	8233
	11th to 20th	Night	6% 15% 8% 17% 9% 9% 8% 6% 8% 4 12%	8236
	21st to end	Night	5% 11% 5% 14% 9% 9% 8% 6% 9% 7% 16%	9058
February	1st to 10th	Night	8% 12% 6% 11% 6% 8% 9% 5% 6% 6% 23%	2896
	11th to 20th	Night	7% 12% 5% 10% 8% 7% 8% 5% 6% 6% 24%	2663
	21st to end	Night	6% 14% 5% 11% 7% 7% 8% 5% 5% 5% 25%	2076
March	1st to 10th	Night	11% 12% 3 11% 6% 5% 6% 4 6% 6% 31%	5482
	11th to 20th	Night	10% 16% 6% 12% 7% 6% 5% 3 4 6% 24%	5386
	21st to end	Night	13% 17% 5% 10% 6% 6% 5% 4 5% 5% 24%	5086
April	1st to 10th	Night	14% 14% 4 9% 6% 4 4 3 4 6% 31%	2100
	11th to 20th	Night	18% 12% 4 9% 4 4 4 3 5% 5% 31%	2038
	21st to end	Night	16% 10% 4 6% 5% 4 4 3 5% 6% 36%	1770
May	1st to 10th	Night	13% 10% 3 7% 4 4 4 4 5% 6% 40%	4688
	11th to 20th	Night	20% 8% 2 6% 4 4 4 4 5% 6% 37%	4670
	21st to end	Night	16% 6% 2 5% 4 3 4 4 5% 6% 46%	4973
June	1st to 10th	Night	18% 7% 1 6% 5% 6% 4 4 6% 7% 37%	1470
	11th to 20th	Night	14% 7% 3 6% 4 5% 4 4 5% 7% 42%	1302
	21st to end	Night	16% 7% 3 5% 3 4 5% 4 6% 7% 39%	1260
July	1st to 10th	Night	9% 7% 2 8% 5% 5% 5% 4 5% 8% 42%	3056
	11th to 20th	Night	12% 7% 2 7% 4 4 3 3 6% 8% 43%	3620
	21st to end	Night	11% 6% 3 7% 5% 5% 4 3 6% 9% 42%	3948
August	1st to 10th	Night	16% 5% 2 5% 4 4 3 3 5% 7% 45%	2597
	11th to 20th	Night	12% 4 1 5% 4 4 4 4 7% 10% 43%	2563
	21st to end	Night	14% 6% 2 5% 3 4 3 3 5% 8% 47%	3538
September	1st to 10th	Night	15% 6% 2 5% 3 4 4 3 6% 7% 45%	2000
	11th to 20th	Night	18% 7% 2 6% 4 4 4 4 6% 6% 39%	2036
	21st to end	Night	22% 7% 3 6% 4 3 3 3 5% 7% 37%	2200
October	1st to 10th	Night	19% 10% 3 6% 4 4 5% 4 5% 6% 34%	2390
	11th to 20th	Night	19% 16% 3 8% 5% 5% 5% 3 4 6% 26%	2495
	21st to end	Night	20% 17% 4 9% 5% 4 5% 4 6% 6% 22%	2860
November	1st to 10th	Night	18% 16% 6% 10% 5% 5% 4 4 5% 5% 22%	2734
	11th to 20th	Night	18% 17% 5% 14% 6% 5% 5% 4 4 6% 16%	2940
	21st to end	Night	15% 18% 7% 15% 7% 5% 5% 3 4 4 15%	3103
December	1st to 10th	Night	10% 24% 8% 16% 9% 6% 4 3 4 4 11%	5060
	11th to 20th	Night	10% 13% 6% 16% 9% 7% 6% 4 6% 5% 18%	5736
	21st to end	Night	15% 20% 6% 16% 7% 4 4 4 4 4 15%	7602

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% 6% 8% 14% 5% 1	4692
	11th to 20th	Day	73% 5% 7% 13% 2	4710
	21st to end	Day	62% 6% 9% 13% 9%	5156
February	1st to 10th	Day	59% 6% 10% 16% 7% 1	1722
	11th to 20th	Day	54% 6% 11% 21% 8%	1853
	21st to end	Day	54% 5% 10% 16% 13% 1	1730
March	1st to 10th	Day	56% 5% 7% 16% 14% 3	4580
	11th to 20th	Day	57% 6% 7% 18% 12% 1	4826
	21st to end	Day	56% 5% 8% 19% 11% 1	6086
April	1st to 10th	Day	52% 5% 10% 20% 12% 2	2520
	11th to 20th	Day	52% 6% 10% 20% 11% 1	2530
	21st to end	Day	49% 7% 10% 18% 14% 2	2845
May	1st to 10th	Day	47% 7% 10% 21% 15% 1	8250
	11th to 20th	Day	44% 7% 9% 21% 16% 2	8226
	21st to end	Day	36% 7% 12% 25% 17% 3	9235
June	1st to 10th	Day	48% 7% 11% 19% 14% 1	3150
	11th to 20th	Day	44% 8% 11% 23% 12% 1	3312
	21st to end	Day	43% 9% 15% 24% 9% 1	3360
July	1st to 10th	Day	37% 7% 14% 31% 10% 1	6844
	11th to 20th	Day	37% 7% 18% 31% 7%	6285
	21st to end	Day	41% 8% 15% 29% 7%	6728
August	1st to 10th	Day	43% 9% 14% 27% 7%	4548
	11th to 20th	Day	32% 7% 22% 29% 10%	4538
	21st to end	Day	37% 7% 15% 31% 9% 1	4341
September	1st to 10th	Day	44% 8% 13% 25% 9%	2400
	11th to 20th	Day	48% 8% 17% 21% 5%	2344
	21st to end	Day	49% 7% 15% 23% 6% 1	2200
October	1st to 10th	Day	49% 6% 15% 19% 10%	3268
	11th to 20th	Day	55% 6% 15% 21% 3	3082
	21st to end	Day	60% 6% 16% 16% 2	3180
November	1st to 10th	Day	64% 7% 11% 13% 4 1	1780
	11th to 20th	Day	73% 7% 10% 7% 3	1680
	21st to end	Day	72% 8% 12% 5% 4	1516
December	1st to 10th	Day	73% 7% 12% 6% 2	2350
	11th to 20th	Day	64% 8% 9% 12% 7%	2691
	21st to end	Day	71% 5% 7% 13% 3	3600
January	1st to 10th	Night	65% 6% 9% 12% 7% 2	8233
	11th to 20th	Night	71% 5% 7% 12% 4	8280
	21st to end	Night	62% 7% 9% 16% 5%	9058
February	1st to 10th	Night	57% 7% 10% 18% 8%	2896
	11th to 20th	Night	57% 5% 11% 19% 7%	2664
	21st to end	Night	57% 6% 11% 16% 9% 1	2076
March	1st to 10th	Night	51% 5% 9% 14% 18% 3	5493
	11th to 20th	Night	60% 6% 9% 17% 8% 1	5387
	21st to end	Night	59% 6% 7% 17% 10% 1	5086
April	1st to 10th	Night	53% 7% 8% 19% 12% 1	2100
	11th to 20th	Night	54% 5% 10% 19% 11% 2	2038
	21st to end	Night	49% 4 10% 21% 12% 4	1770
May	1st to 10th	Night	43% 6% 10% 25% 14% 2	4695
	11th to 20th	Night	47% 6% 11% 21% 13% 3	4671
	21st to end	Night	37% 7% 10% 27% 18% 1	4974
June	1st to 10th	Night	45% 7% 13% 21% 13% 2	1470
	11th to 20th	Night	40% 7% 10% 28% 14% 1	1302
	21st to end	Night	42% 8% 14% 24% 11% 1	1260
July	1st to 10th	Night	38% 8% 15% 27% 12%	3020
	11th to 20th	Night	37% 7% 19% 29% 7% 1	3572
	21st to end	Night	38% 7% 15% 31% 9%	3832
August	1st to 10th	Night	38% 7% 15% 32% 8% 1	2588
	11th to 20th	Night	34% 7% 20% 31% 9%	2587
	21st to end	Night	36% 6% 20% 27% 11%	3538
September	1st to 10th	Night	37% 9% 15% 29% 9% 1	2000
	11th to 20th	Night	44% 9% 18% 25% 4	2036
	21st to end	Night	46% 7% 15% 25% 6%	2200
October	1st to 10th	Night	41% 5% 17% 24% 13%	3910
	11th to 20th	Night	55% 6% 12% 18% 7%	4057
	21st to end	Night	59% 7% 16% 15% 2	4610
November	1st to 10th	Night	63% 8% 11% 13% 4	2734
	11th to 20th	Night	69% 7% 12% 10% 2	2940
	21st to end	Night	72% 8% 10% 7% 3	3103
December	1st to 10th	Night	76% 7% 10% 6% 2	5060
	11th to 20th	Night	66% 7% 12% 11% 4	5735
	21st to end	Night	71% 6% 7% 13% 3	7602

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% 12% 35% 29% 8% 1	330
	11th to 20th	Day	12% 9% 38% 29% 9% 2	330
	21st to end	Day	12% 7% 40% 29% 9% 2	363
February	1st to 10th	Day	13% 17% 33% 27% 8% 2	330
	11th to 20th	Day	11% 14% 40% 27% 7% 2	330
	21st to end	Day	9% 19% 43% 23% 6%	273
March	1st to 10th	Day	18% 15% 35% 24% 7% 2	330
	11th to 20th	Day	15% 19% 36% 20% 8% 1	330
	21st to end	Day	17% 13% 30% 27% 10% 2	579
April	1st to 10th	Day	16% 13% 32% 27% 12% 1	540
	11th to 20th	Day	24% 13% 25% 23% 13% 2	532
	21st to end	Day	22% 8% 30% 25% 12% 3	655
May	1st to 10th	Day	24% 9% 30% 25% 11% 2	753
	11th to 20th	Day	20% 10% 35% 23% 10% 2	775
	21st to end	Day	21% 9% 31% 29% 9% 2	844
June	1st to 10th	Day	19% 7% 34% 26% 11% 2	780
	11th to 20th	Day	16% 12% 32% 27% 11% 2	780
	21st to end	Day	18% 8% 31% 27% 11% 4	780
July	1st to 10th	Day	14% 8% 27% 33% 14% 4	722
	11th to 20th	Day	13% 7% 32% 29% 16% 4	718
	21st to end	Day	11% 8% 26% 32% 18% 5%	794
August	1st to 10th	Day	13% 9% 27% 34% 14% 4	726
	11th to 20th	Day	15% 6% 24% 31% 21% 4	715
	21st to end	Day	17% 10% 27% 27% 16% 3	597
September	1st to 10th	Day	18% 9% 28% 26% 16% 2	530
	11th to 20th	Day	25% 9% 22% 28% 15% 1	530
	21st to end	Day	23% 11% 26% 29% 9% 3	530
October	1st to 10th	Day	27% 14% 28% 20% 9% 2	338
	11th to 20th	Day	20% 14% 39% 18% 8% 1	330
	21st to end	Day	29% 18% 35% 13% 5% 1	363
November	1st to 10th	Day	22% 17% 31% 20% 8% 1	330
	11th to 20th	Day	28% 20% 31% 17% 2 1	330
	21st to end	Day	23% 20% 34% 17% 5%	244
December	1st to 10th	Day	19% 11% 36% 27% 5% 2	220
	11th to 20th	Day	19% 14% 39% 21% 8%	220
	21st to end	Day	21% 13% 32% 23% 10% 2	253
January	1st to 10th	Night	15% 9% 37% 31% 7%	1050
	11th to 20th	Night	18% 8% 32% 31% 10% 2	1050
	21st to end	Night	15% 7% 33% 33% 11% 2	1155
February	1st to 10th	Night	15% 8% 32% 34% 10% 1	1050
	11th to 20th	Night	14% 8% 34% 30% 14% 1	1029
	21st to end	Night	13% 8% 34% 33% 11% 1	692
March	1st to 10th	Night	14% 9% 35% 30% 10% 1	840
	11th to 20th	Night	17% 11% 33% 30% 8% 1	771
	21st to end	Night	19% 10% 27% 29% 11% 3	693
April	1st to 10th	Night	19% 9% 27% 34% 11% 1	630
	11th to 20th	Night	24% 9% 27% 29% 11%	623
	21st to end	Night	20% 7% 27% 32% 13% 2	630
May	1st to 10th	Night	20% 6% 28% 36% 10%	630
	11th to 20th	Night	21% 7% 30% 30% 10% 2	621
	21st to end	Night	22% 7% 24% 36% 10%	625
June	1st to 10th	Night	19% 6% 27% 35% 12% 1	420
	11th to 20th	Night	16% 7% 28% 36% 13%	420
	21st to end	Night	17% 7% 25% 34% 15% 1	420
July	1st to 10th	Night	12% 4 27% 41% 14% 2	491
	11th to 20th	Night	11% 7% 26% 38% 16% 2	582
	21st to end	Night	10% 4 25% 39% 21% 2	657
August	1st to 10th	Night	14% 4 27% 39% 15% 1	597
	11th to 20th	Night	14% 6% 22% 34% 22% 3	594
	21st to end	Night	15% 5% 30% 32% 17% 2	660
September	1st to 10th	Night	17% 6% 23% 36% 17% 1	600
	11th to 20th	Night	21% 7% 31% 27% 14%	636
	21st to end	Night	26% 8% 22% 33% 10% 2	800
October	1st to 10th	Night	25% 11% 28% 26% 9% 1	800
	11th to 20th	Night	27% 11% 29% 24% 9%	800
	21st to end	Night	27% 10% 31% 23% 8% 1	880
November	1st to 10th	Night	26% 13% 29% 24% 7% 1	888
	11th to 20th	Night	26% 13% 28% 23% 7% 2	1050
	21st to end	Night	24% 16% 32% 23% 5%	1050
December	1st to 10th	Night	17% 14% 38% 21% 9% 2	1050
	11th to 20th	Night	20% 12% 35% 24% 8% 1	1050
	21st to end	Night	24% 9% 29% 27% 8% 2	1155

Page generated at 2026-06-28 02:10:47. Version ac07

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