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 2024-09-29.

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	14% 11% 4 9% 5% 5% 5% 4 5% 7% 32%	101910
	Night	14% 12% 4 10% 6% 5% 5% 4 5% 6% 28%	96454
Transparency	Day	50% 8% 12% 21% 9% 1	101664
	Night	54% 8% 12% 18% 7% 1	96318
Seeing	Day	18% 10% 30% 27% 12% 3	15799
	Night	19% 8% 29% 31% 11% 1	25283

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% 13% 6% 15% 10% 10% 7% 5% 7% 6% 14%	2527
	11th to 20th	Day	5% 12% 6% 14% 11% 11% 9% 5% 5% 5% 18%	2530
	21st to end	Day	12% 18% 10% 14% 7% 6% 5% 4 6% 5% 13%	2783
February	1st to 10th	Day	7% 13% 5% 13% 6% 8% 7% 6% 6% 6% 24%	1558
	11th to 20th	Day	7% 13% 5% 12% 7% 7% 5% 5% 6% 6% 27%	1664
	21st to end	Day	5% 12% 5% 14% 7% 7% 5% 4 6% 6% 30%	1570
March	1st to 10th	Day	13% 10% 4 11% 5% 5% 4 3 4 5% 36%	3118
	11th to 20th	Day	8% 16% 7% 11% 5% 7% 5% 2 4 5% 29%	3306
	21st to end	Day	15% 17% 4 9% 5% 4 4 3 4 5% 30%	4151
April	1st to 10th	Day	12% 13% 5% 10% 6% 4 4 3 5% 5% 33%	2280
	11th to 20th	Day	18% 12% 4 8% 4 3 4 3 5% 7% 32%	2286
	21st to end	Day	16% 12% 3 7% 5% 4 4 3 6% 6% 35%	2574
May	1st to 10th	Day	18% 11% 4 7% 5% 4 4 3 5% 7% 32%	4428
	11th to 20th	Day	15% 10% 3 7% 5% 5% 5% 4 6% 6% 34%	4399
	21st to end	Day	20% 8% 3 5% 4 4 4 3 5% 7% 37%	4927
June	1st to 10th	Day	20% 8% 3 8% 6% 4 4 3 5% 6% 33%	2850
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 4 6% 8% 36%	2996
	21st to end	Day	16% 7% 2 7% 5% 5% 5% 4 7% 7% 35%	3040
July	1st to 10th	Day	13% 6% 2 6% 6% 5% 5% 4 7% 8% 39%	4836
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 5% 6% 8% 44%	4440
	21st to end	Day	12% 7% 2 7% 4 5% 5% 5% 7% 8% 38%	4814
August	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 8% 36%	4423
	11th to 20th	Day	11% 5% 1 4 3 4 5% 4 6% 8% 49%	4356
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 3 6% 9% 42%	4209
September	1st to 10th	Day	16% 5% 2 7% 5% 4 6% 4 6% 7% 38%	2280
	11th to 20th	Day	22% 9% 3 6% 4 3 5% 4 6% 7% 31%	2227
	21st to end	Day	20% 10% 3 8% 4 5% 4 3 5% 6% 34%	2069
October	1st to 10th	Day	20% 16% 4 8% 5% 3 4 2 4 6% 27%	1808
	11th to 20th	Day	19% 19% 3 9% 5% 4 5% 3 4 6% 22%	1715
	21st to end	Day	19% 19% 4 10% 6% 6% 4 3 4 6% 19%	1782
November	1st to 10th	Day	16% 17% 5% 12% 7% 6% 4 4 5% 5% 19%	1608
	11th to 20th	Day	18% 19% 6% 13% 9% 5% 4 3 4 5% 13%	1520
	21st to end	Day	16% 17% 6% 17% 7% 5% 4 3 4 4 15%	1372
December	1st to 10th	Day	10% 16% 6% 14% 6% 6% 5% 5% 7% 5% 19%	1330
	11th to 20th	Day	11% 16% 6% 11% 7% 8% 6% 6% 6% 6% 17%	1671
	21st to end	Day	19% 21% 7% 10% 7% 6% 4 3 5% 4 15%	2463
January	1st to 10th	Night	8% 17% 6% 14% 8% 8% 6% 5% 6% 7% 16%	4428
	11th to 20th	Night	7% 11% 6% 17% 11% 10% 8% 5% 6% 5% 13%	4440
	21st to end	Night	10% 18% 7% 14% 8% 6% 6% 5% 6% 6% 14%	4884
February	1st to 10th	Night	8% 12% 6% 10% 6% 8% 9% 5% 6% 7% 24%	2621
	11th to 20th	Night	8% 12% 5% 10% 8% 7% 8% 5% 6% 6% 25%	2403
	21st to end	Night	6% 14% 5% 11% 7% 6% 8% 5% 5% 5% 27%	1884
March	1st to 10th	Night	12% 10% 3 12% 6% 6% 6% 4 6% 6% 31%	3722
	11th to 20th	Night	9% 17% 6% 11% 6% 5% 5% 3 4 5% 27%	3685
	21st to end	Night	14% 16% 4 8% 5% 6% 5% 3 4 5% 28%	3479
April	1st to 10th	Night	14% 14% 4 9% 6% 4 4 3 4 6% 31%	1900
	11th to 20th	Night	18% 12% 4 9% 5% 4 4 4 6% 5% 31%	1842
	21st to end	Night	16% 10% 4 6% 5% 4 3 3 5% 6% 38%	1602
May	1st to 10th	Night	15% 10% 3 7% 4 4 3 4 5% 6% 38%	2523
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 5% 7% 7% 38%	2506
	21st to end	Night	23% 7% 2 5% 4 4 4 4 4 5% 37%	2659
June	1st to 10th	Night	19% 7% 1 6% 5% 6% 4 4 6% 7% 35%	1330
	11th to 20th	Night	13% 7% 3 6% 4 5% 4 4 4 7% 42%	1178
	21st to end	Night	17% 7% 2 5% 3 4 5% 4 6% 7% 39%	1140
July	1st to 10th	Night	8% 6% 2 8% 6% 6% 6% 5% 6% 8% 39%	2126
	11th to 20th	Night	10% 5% 2 6% 4 4 4 3 6% 8% 48%	2530
	21st to end	Night	10% 5% 2 6% 4 4 4 3 7% 9% 46%	2750
August	1st to 10th	Night	17% 5% 2 5% 4 4 3 3 5% 7% 44%	2517
	11th to 20th	Night	12% 4 1 5% 4 4 4 4 7% 10% 44%	2483
	21st to end	Night	14% 6% 2 5% 3 4 3 3 5% 8% 48%	3430
September	1st to 10th	Night	14% 5% 2 5% 3 4 4 4 6% 7% 47%	1900
	11th to 20th	Night	19% 6% 2 6% 4 4 4 4 5% 6% 38%	1934
	21st to end	Night	23% 7% 3 6% 4 3 3 3 6% 7% 36%	2079
October	1st to 10th	Night	21% 11% 4 6% 4 4 4 4 5% 6% 32%	2150
	11th to 20th	Night	19% 16% 3 8% 5% 5% 6% 4 5% 6% 25%	2245
	21st to end	Night	20% 17% 4 9% 5% 4 5% 4 6% 6% 21%	2574
November	1st to 10th	Night	19% 17% 6% 10% 5% 4 4 3 5% 5% 21%	2467
	11th to 20th	Night	17% 17% 5% 14% 7% 5% 5% 4 4 6% 16%	2660
	21st to end	Night	16% 18% 6% 15% 7% 5% 5% 3 4 4 16%	2807
December	1st to 10th	Night	9% 16% 6% 14% 9% 7% 5% 4 6% 6% 17%	2850
	11th to 20th	Night	11% 15% 6% 14% 7% 6% 6% 5% 7% 5% 18%	3526
	21st to end	Night	17% 21% 5% 14% 8% 4 5% 4 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	58% 6% 11% 17% 7% 2	1558
	11th to 20th	Day	54% 6% 11% 20% 9%	1673
	21st to end	Day	53% 5% 11% 17% 14% 1	1570
March	1st to 10th	Day	48% 6% 9% 21% 13% 2	3120
	11th to 20th	Day	56% 7% 8% 20% 9% 1	3306
	21st to end	Day	55% 5% 8% 17% 14% 1	4151
April	1st to 10th	Day	52% 5% 10% 19% 12% 2	2280
	11th to 20th	Day	51% 6% 10% 21% 11% 1	2286
	21st to end	Day	47% 7% 10% 18% 15% 2	2574
May	1st to 10th	Day	48% 7% 10% 21% 13% 1	4440
	11th to 20th	Day	44% 10% 11% 21% 11% 3	4403
	21st to end	Day	43% 10% 12% 19% 14% 2	4927
June	1st to 10th	Day	49% 7% 11% 18% 14% 1	2850
	11th to 20th	Day	44% 8% 11% 23% 13% 1	2996
	21st to end	Day	43% 9% 15% 24% 9%	3040
July	1st to 10th	Day	40% 9% 16% 25% 10% 1	4763
	11th to 20th	Day	34% 8% 18% 32% 8% 1	4365
	21st to end	Day	41% 8% 13% 31% 7%	4662
August	1st to 10th	Day	43% 9% 14% 27% 7%	4408
	11th to 20th	Day	31% 8% 22% 29% 11%	4398
	21st to end	Day	37% 7% 15% 31% 9% 1	4208
September	1st to 10th	Day	43% 8% 13% 26% 9%	2280
	11th to 20th	Day	49% 9% 17% 20% 5%	2227
	21st to end	Day	51% 7% 14% 22% 6%	2069
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%	2621
	11th to 20th	Night	57% 6% 11% 18% 8%	2404
	21st to end	Night	56% 6% 11% 16% 10% 1	1884
March	1st to 10th	Night	52% 5% 11% 17% 14% 1	3733
	11th to 20th	Night	57% 7% 9% 19% 7% 1	3686
	21st to end	Night	55% 6% 8% 17% 12% 1	3479
April	1st to 10th	Night	53% 7% 8% 19% 12% 1	1900
	11th to 20th	Night	54% 5% 9% 19% 11% 2	1842
	21st to end	Night	47% 4 10% 21% 13% 4	1602
May	1st to 10th	Night	44% 7% 11% 24% 13% 1	2530
	11th to 20th	Night	42% 9% 12% 25% 9% 2	2507
	21st to end	Night	46% 9% 11% 18% 15% 2	2660
June	1st to 10th	Night	46% 8% 13% 21% 11% 2	1330
	11th to 20th	Night	40% 7% 10% 27% 15% 1	1178
	21st to end	Night	42% 8% 14% 24% 11% 1	1140
July	1st to 10th	Night	39% 10% 17% 21% 12%	2090
	11th to 20th	Night	32% 7% 18% 32% 10% 2	2482
	21st to end	Night	34% 8% 15% 36% 7%	2662
August	1st to 10th	Night	39% 7% 15% 31% 8% 1	2508
	11th to 20th	Night	34% 7% 19% 31% 9%	2507
	21st to end	Night	36% 6% 20% 27% 11%	3430
September	1st to 10th	Night	35% 8% 15% 31% 10% 1	1900
	11th to 20th	Night	44% 9% 18% 25% 4	1934
	21st to end	Night	48% 7% 15% 24% 6%	2079
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	11% 14% 33% 30% 9% 2	270
	11th to 20th	Day	11% 14% 40% 26% 7% 2	270
	21st to end	Day	8% 17% 45% 24% 6%	225
March	1st to 10th	Day	14% 13% 35% 29% 8% 2	270
	11th to 20th	Day	15% 18% 34% 23% 9% 1	270
	21st to end	Day	16% 10% 29% 30% 11% 3	492
April	1st to 10th	Day	16% 10% 32% 28% 13% 1	460
	11th to 20th	Day	23% 13% 24% 25% 13% 2	452
	21st to end	Day	20% 8% 31% 27% 11% 3	564
May	1st to 10th	Day	24% 8% 30% 25% 11% 2	653
	11th to 20th	Day	19% 9% 35% 24% 11% 2	675
	21st to end	Day	22% 8% 30% 30% 8% 2	734
June	1st to 10th	Day	20% 6% 33% 27% 11% 2	680
	11th to 20th	Day	17% 10% 32% 26% 13% 2	680
	21st to end	Day	18% 7% 31% 29% 12% 4	680
July	1st to 10th	Day	14% 7% 27% 33% 14% 4	671
	11th to 20th	Day	12% 6% 31% 30% 17% 4	668
	21st to end	Day	11% 8% 24% 33% 18% 5%	739
August	1st to 10th	Day	13% 9% 26% 34% 15% 4	676
	11th to 20th	Day	15% 6% 22% 31% 22% 4	665
	21st to end	Day	18% 10% 26% 27% 16% 3	553
September	1st to 10th	Day	17% 9% 29% 27% 16% 3	490
	11th to 20th	Day	26% 10% 22% 27% 14% 1	490
	21st to end	Day	24% 11% 26% 29% 9% 2	483
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	14% 7% 33% 36% 11% 1	950
	11th to 20th	Night	15% 7% 33% 30% 15% 1	929
	21st to end	Night	12% 8% 34% 33% 12% 1	628
March	1st to 10th	Night	13% 9% 35% 30% 11% 2	760
	11th to 20th	Night	18% 10% 33% 30% 9% 1	698
	21st to end	Night	19% 9% 27% 30% 12% 4	627
April	1st to 10th	Night	19% 9% 26% 34% 11% 1	570
	11th to 20th	Night	24% 9% 26% 29% 11%	563
	21st to end	Night	19% 7% 27% 32% 13% 2	570
May	1st to 10th	Night	21% 6% 28% 35% 9% 1	570
	11th to 20th	Night	20% 6% 30% 31% 11% 2	561
	21st to end	Night	23% 7% 23% 37% 9%	565
June	1st to 10th	Night	20% 6% 27% 34% 12% 1	380
	11th to 20th	Night	16% 7% 28% 36% 14%	380
	21st to end	Night	18% 6% 25% 35% 15% 1	380
July	1st to 10th	Night	12% 4 26% 41% 14% 2	465
	11th to 20th	Night	11% 6% 26% 39% 17% 2	552
	21st to end	Night	10% 3 24% 38% 22% 2	624
August	1st to 10th	Night	14% 4 26% 39% 16% 1	567
	11th to 20th	Night	14% 5% 21% 35% 23% 3	564
	21st to end	Night	15% 5% 30% 32% 17% 2	627
September	1st to 10th	Night	16% 5% 23% 37% 17% 1	570
	11th to 20th	Night	22% 7% 32% 27% 13%	604
	21st to end	Night	27% 7% 22% 33% 10% 2	756
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 2024-09-26 09:52:22. Version ac07

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