Big Bay Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Bay Point clear sky chart from 2005-11-06 to 2024-11-10.

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	13% 10% 4 10% 6% 5% 5% 4 5% 7% 32%	101327
	Night	13% 13% 5% 11% 6% 5% 4 3 5% 6% 28%	97883
Transparency	Day	50% 7% 12% 21% 9% 1	104773
	Night	56% 6% 11% 18% 8% 1	102524
Seeing	Day	17% 8% 25% 30% 16% 3	15943
	Night	20% 10% 27% 28% 13% 2	25878

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	10% 19% 11% 19% 8% 7% 5% 3 4 5% 9%	2527
	11th to 20th	Day	9% 16% 8% 20% 15% 7% 3 4 5% 4 8%	2530
	21st to end	Day	9% 17% 8% 17% 11% 7% 6% 4 5% 5% 11%	2783
February	1st to 10th	Day	8% 13% 6% 14% 13% 9% 7% 5% 5% 4 17%	1577
	11th to 20th	Day	7% 12% 5% 15% 11% 9% 7% 5% 4 5% 20%	1781
	21st to end	Day	11% 14% 6% 13% 10% 6% 7% 5% 6% 6% 18%	1570
March	1st to 10th	Day	9% 12% 6% 12% 6% 6% 5% 3 4 6% 33%	3118
	11th to 20th	Day	7% 12% 7% 17% 10% 5% 4 3 4 5% 26%	3260
	21st to end	Day	16% 12% 6% 16% 8% 6% 5% 4 5% 5% 17%	4165
April	1st to 10th	Day	14% 14% 4 8% 5% 5% 5% 4 6% 7% 29%	2280
	11th to 20th	Day	19% 11% 4 8% 5% 4 4 4 5% 6% 29%	2289
	21st to end	Day	15% 10% 3 7% 5% 4 4 4 5% 7% 35%	2470
May	1st to 10th	Day	14% 8% 2 6% 4 4 4 3 5% 7% 42%	4319
	11th to 20th	Day	11% 7% 3 7% 5% 4 5% 4 6% 7% 41%	4399
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 5% 5% 7% 39%	4837
June	1st to 10th	Day	11% 6% 2 6% 6% 4 5% 3 5% 8% 42%	2660
	11th to 20th	Day	13% 5% 2 5% 5% 4 5% 5% 7% 8% 40%	2715
	21st to end	Day	15% 6% 3 6% 4 4 4 4 6% 7% 40%	2660
July	1st to 10th	Day	12% 5% 2 7% 4 5% 6% 4 6% 8% 42%	4440
	11th to 20th	Day	7% 4 2 5% 3 3 4 4 7% 10% 51%	4440
	21st to end	Day	9% 3 2 4 3 4 4 4 7% 8% 52%	4814
August	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 4 6% 9% 44%	4423
	11th to 20th	Day	14% 5% 2 4 3 4 3 3 5% 6% 50%	4149
	21st to end	Day	14% 6% 2 5% 3 3 4 3 5% 7% 47%	4193
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 3 6% 7% 41%	2280
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	2163
	21st to end	Day	18% 8% 3 7% 5% 4 5% 4 6% 6% 33%	2090
October	1st to 10th	Day	18% 10% 3 7% 5% 4 4 4 6% 8% 31%	2009
	11th to 20th	Day	22% 14% 4 11% 7% 4 5% 4 6% 6% 18%	1795
	21st to end	Day	21% 21% 5% 10% 6% 5% 4 3 4 4 17%	1881
November	1st to 10th	Day	17% 18% 5% 10% 4 4 4 4 7% 6% 22%	1753
	11th to 20th	Day	17% 19% 8% 14% 7% 5% 5% 3 4 5% 14%	1636
	21st to end	Day	15% 21% 9% 18% 6% 5% 4 4 4 3 13%	1520
December	1st to 10th	Day	10% 18% 10% 17% 8% 7% 6% 3 5% 5% 12%	1337
	11th to 20th	Day	16% 20% 8% 19% 5% 5% 5% 3 4 5% 10%	1681
	21st to end	Day	19% 22% 11% 16% 8% 5% 5% 3 3 3 5%	2783
January	1st to 10th	Night	12% 20% 9% 21% 6% 6% 3 2 3 3 14%	4428
	11th to 20th	Night	9% 19% 7% 22% 14% 9% 5% 3 3 3 8%	4440
	21st to end	Night	10% 16% 10% 16% 9% 7% 6% 4 4 4 14%	4884
February	1st to 10th	Night	8% 15% 6% 14% 11% 8% 8% 4 5% 5% 17%	2602
	11th to 20th	Night	10% 11% 5% 13% 12% 8% 6% 5% 5% 6% 19%	2285
	21st to end	Night	12% 16% 5% 14% 8% 6% 5% 3 5% 6% 21%	1884
March	1st to 10th	Night	8% 10% 5% 9% 5% 5% 6% 4 6% 8% 32%	3722
	11th to 20th	Night	8% 14% 8% 13% 5% 4 5% 4 5% 6% 29%	3720
	21st to end	Night	16% 11% 7% 14% 8% 5% 4 4 4 6% 21%	3474
April	1st to 10th	Night	16% 14% 4 8% 6% 5% 4 4 6% 6% 27%	1900
	11th to 20th	Night	20% 10% 3 6% 5% 3 4 4 5% 8% 31%	1838
	21st to end	Night	16% 11% 3 7% 5% 5% 4 3 5% 7% 35%	1710
May	1st to 10th	Night	16% 8% 3 6% 4 4 4 4 5% 6% 41%	2626
	11th to 20th	Night	11% 9% 3 7% 5% 5% 5% 4 6% 6% 40%	2506
	21st to end	Night	16% 8% 3 8% 5% 5% 5% 4 5% 6% 35%	2750
June	1st to 10th	Night	13% 6% 2 7% 5% 5% 5% 3 5% 7% 40%	1520
	11th to 20th	Night	12% 6% 3 8% 6% 6% 7% 4 7% 8% 35%	1402
	21st to end	Night	16% 6% 2 6% 4 4 4 4 6% 8% 38%	1520
July	1st to 10th	Night	9% 7% 3 8% 5% 5% 5% 4 4 7% 42%	2530
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 6% 7% 52%	2530
	21st to end	Night	10% 4 1 5% 3 3 3 3 6% 9% 53%	2750
August	1st to 10th	Night	11% 6% 2 7% 4 4 4 4 5% 8% 44%	2517
	11th to 20th	Night	15% 6% 1 5% 2 3 3 3 4 7% 50%	2681
	21st to end	Night	14% 7% 3 6% 3 4 4 2 4 5% 47%	3461
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 4 7% 47%	1900
	11th to 20th	Night	14% 7% 2 6% 6% 5% 4 4 5% 7% 40%	1997
	21st to end	Night	19% 7% 2 7% 6% 5% 4 3 5% 6% 35%	2090
October	1st to 10th	Night	19% 9% 2 6% 5% 4 4 4 6% 6% 35%	2170
	11th to 20th	Night	19% 14% 3 8% 5% 4 5% 3 5% 7% 26%	2384
	21st to end	Night	21% 18% 4 9% 6% 5% 4 4 4 4 20%	2717
November	1st to 10th	Night	17% 19% 4 9% 5% 4 4 4 4 6% 24%	2530
	11th to 20th	Night	16% 21% 7% 14% 6% 5% 3 3 4 4 17%	2541
	21st to end	Night	15% 19% 9% 17% 7% 4 3 3 4 4 14%	2660
December	1st to 10th	Night	12% 19% 9% 16% 8% 7% 4 4 4 5% 12%	2836
	11th to 20th	Night	13% 17% 8% 19% 8% 6% 5% 3 4 5% 13%	3494
	21st to end	Night	18% 22% 11% 15% 7% 5% 4 3 3 3 7%	4884

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	77% 6% 7% 8% 1	2528
	11th to 20th	Day	80% 5% 6% 9%	2530
	21st to end	Day	72% 10% 12% 5% 2	2783
February	1st to 10th	Day	68% 6% 10% 11% 4	1577
	11th to 20th	Day	65% 7% 11% 13% 5%	1790
	21st to end	Day	63% 8% 10% 12% 6% 1	1570
March	1st to 10th	Day	52% 6% 13% 20% 9%	3120
	11th to 20th	Day	59% 6% 13% 15% 6% 1	3260
	21st to end	Day	65% 6% 11% 12% 5%	4165
April	1st to 10th	Day	52% 7% 11% 21% 8% 1	2280
	11th to 20th	Day	54% 6% 9% 21% 9% 2	2289
	21st to end	Day	47% 7% 10% 20% 13% 3	2470
May	1st to 10th	Day	41% 6% 11% 25% 17% 1	4331
	11th to 20th	Day	40% 9% 12% 28% 11% 1	4403
	21st to end	Day	41% 8% 14% 18% 17% 1	4837
June	1st to 10th	Day	38% 7% 14% 25% 13% 2	2660
	11th to 20th	Day	39% 8% 14% 24% 14% 1	2715
	21st to end	Day	41% 7% 14% 25% 12% 1	2660
July	1st to 10th	Day	38% 7% 16% 24% 13% 1	4371
	11th to 20th	Day	27% 7% 15% 35% 14% 2	4365
	21st to end	Day	28% 7% 12% 34% 17% 1	4662
August	1st to 10th	Day	35% 8% 17% 29% 10% 1	4408
	11th to 20th	Day	34% 6% 17% 33% 10%	4190
	21st to end	Day	35% 7% 17% 27% 13% 1	4192
September	1st to 10th	Day	41% 8% 11% 30% 10%	2280
	11th to 20th	Day	40% 10% 19% 24% 6%	2163
	21st to end	Day	49% 8% 15% 22% 7%	2090
October	1st to 10th	Day	38% 7% 13% 31% 11%	3334
	11th to 20th	Day	60% 5% 10% 15% 10%	2959
	21st to end	Day	64% 6% 12% 14% 4	3081
November	1st to 10th	Day	62% 6% 11% 15% 6%	1753
	11th to 20th	Day	73% 6% 9% 9% 4	1636
	21st to end	Day	76% 7% 8% 7% 2	1520
December	1st to 10th	Day	75% 6% 9% 8% 2	1337
	11th to 20th	Day	78% 7% 7% 7% 2	1681
	21st to end	Day	83% 7% 6% 4 1	2783
January	1st to 10th	Night	76% 4 8% 11% 1	4428
	11th to 20th	Night	82% 5% 6% 6% 1	4440
	21st to end	Night	72% 8% 13% 5% 1	4884
February	1st to 10th	Night	68% 6% 9% 12% 4	2602
	11th to 20th	Night	65% 6% 11% 14% 4	2286
	21st to end	Night	64% 6% 11% 14% 6%	1884
March	1st to 10th	Night	46% 8% 20% 19% 6%	3733
	11th to 20th	Night	54% 5% 11% 22% 8%	3721
	21st to end	Night	64% 6% 9% 15% 6% 1	3474
April	1st to 10th	Night	57% 5% 11% 16% 10% 1	1900
	11th to 20th	Night	51% 6% 9% 20% 11% 2	1838
	21st to end	Night	48% 6% 10% 20% 14% 2	1710
May	1st to 10th	Night	44% 5% 11% 24% 14% 2	2633
	11th to 20th	Night	41% 8% 9% 28% 12% 1	2507
	21st to end	Night	47% 8% 10% 17% 15% 3	2751
June	1st to 10th	Night	42% 6% 11% 26% 13% 1	1520
	11th to 20th	Night	45% 9% 10% 21% 13% 1	1402
	21st to end	Night	41% 8% 14% 23% 13% 1	1520
July	1st to 10th	Night	41% 7% 15% 22% 12% 2	2490
	11th to 20th	Night	28% 7% 13% 38% 13% 1	2482
	21st to end	Night	28% 6% 12% 29% 24% 1	2662
August	1st to 10th	Night	38% 6% 12% 30% 12% 2	2508
	11th to 20th	Night	35% 5% 15% 33% 11% 1	2706
	21st to end	Night	40% 6% 12% 25% 14% 2	3461
September	1st to 10th	Night	37% 6% 14% 29% 13% 1	1900
	11th to 20th	Night	42% 9% 14% 28% 6% 1	1997
	21st to end	Night	49% 7% 14% 22% 8% 1	2090
October	1st to 10th	Night	38% 5% 12% 31% 13% 1	3625
	11th to 20th	Night	50% 5% 12% 21% 12%	3959
	21st to end	Night	60% 7% 13% 16% 4	4467
November	1st to 10th	Night	62% 5% 11% 14% 6%	2530
	11th to 20th	Night	72% 5% 9% 8% 5%	2541
	21st to end	Night	74% 6% 10% 8% 2	2660
December	1st to 10th	Night	75% 7% 8% 8% 1	2836
	11th to 20th	Night	74% 6% 10% 7% 3	3493
	21st to end	Night	80% 7% 5% 6% 1	4884

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	19% 16% 29% 29% 8% 1	270
	11th to 20th	Day	20% 14% 33% 25% 5% 3	270
	21st to end	Day	21% 8% 36% 31% 3 1	297
February	1st to 10th	Day	13% 17% 38% 25% 6% 1	270
	11th to 20th	Day	11% 17% 43% 24% 5%	270
	21st to end	Day	17% 20% 35% 24% 4	225
March	1st to 10th	Day	13% 13% 38% 28% 7% 1	270
	11th to 20th	Day	15% 15% 30% 30% 10% 1	309
	21st to end	Day	20% 12% 34% 22% 10% 1	506
April	1st to 10th	Day	20% 11% 31% 30% 7% 1	460
	11th to 20th	Day	25% 12% 25% 25% 10% 2	452
	21st to end	Day	22% 9% 27% 27% 14% 3	460
May	1st to 10th	Day	17% 7% 30% 31% 14% 2	583
	11th to 20th	Day	16% 5% 24% 36% 15% 4	675
	21st to end	Day	14% 6% 21% 36% 20% 3	734
June	1st to 10th	Day	11% 7% 23% 38% 18% 4	680
	11th to 20th	Day	16% 4 18% 40% 19% 3	680
	21st to end	Day	17% 3 17% 37% 21% 5%	680
July	1st to 10th	Day	8% 2 16% 39% 28% 6%	671
	11th to 20th	Day	12% 3 17% 35% 27% 5%	668
	21st to end	Day	10% 2 17% 38% 27% 7%	739
August	1st to 10th	Day	11% 4 18% 38% 26% 4	676
	11th to 20th	Day	16% 4 12% 30% 30% 8%	548
	21st to end	Day	19% 7% 17% 31% 22% 5%	539
September	1st to 10th	Day	19% 6% 23% 26% 20% 6%	490
	11th to 20th	Day	13% 5% 25% 28% 22% 6%	490
	21st to end	Day	20% 8% 22% 24% 21% 4	490
October	1st to 10th	Day	24% 7% 29% 22% 14% 4	409
	11th to 20th	Day	28% 15% 24% 25% 8%	300
	21st to end	Day	34% 15% 27% 20% 4	330
November	1st to 10th	Day	21% 14% 27% 29% 7% 2	297
	11th to 20th	Day	23% 19% 39% 14% 4 1	270
	21st to end	Day	22% 22% 31% 20% 4	270
December	1st to 10th	Day	21% 14% 35% 19% 10% 1	183
	11th to 20th	Day	27% 21% 37% 9% 4 2	185
	21st to end	Day	26% 21% 30% 18% 6%	297
January	1st to 10th	Night	18% 18% 36% 23% 5% 1	950
	11th to 20th	Night	21% 15% 37% 20% 7%	950
	21st to end	Night	19% 14% 35% 26% 5% 1	1045
February	1st to 10th	Night	16% 17% 33% 25% 8% 1	950
	11th to 20th	Night	15% 13% 37% 24% 10% 1	810
	21st to end	Night	20% 10% 34% 29% 7%	628
March	1st to 10th	Night	13% 11% 32% 30% 12% 1	760
	11th to 20th	Night	17% 13% 32% 28% 10% 1	760
	21st to end	Night	20% 9% 26% 31% 11% 2	635
April	1st to 10th	Night	23% 6% 28% 34% 8% 1	570
	11th to 20th	Night	24% 8% 24% 31% 11% 2	563
	21st to end	Night	21% 6% 25% 31% 14% 3	570
May	1st to 10th	Night	19% 4 24% 33% 17% 4	570
	11th to 20th	Night	17% 4 23% 36% 16% 4	561
	21st to end	Night	14% 4 18% 38% 24% 3	617
June	1st to 10th	Night	15% 4 16% 38% 24% 3	570
	11th to 20th	Night	15% 3 17% 38% 24% 2	452
	21st to end	Night	19% 3 14% 35% 23% 5%	570
July	1st to 10th	Night	11% 3 14% 37% 31% 5%	555
	11th to 20th	Night	14% 2 18% 35% 27% 6%	552
	21st to end	Night	11% 1 17% 37% 28% 6%	624
August	1st to 10th	Night	14% 2 16% 37% 28% 3	567
	11th to 20th	Night	13% 2 16% 29% 32% 8%	564
	21st to end	Night	16% 4 19% 37% 22% 2	627
September	1st to 10th	Night	15% 5% 18% 33% 23% 6%	570
	11th to 20th	Night	17% 5% 22% 33% 20% 3	667
	21st to end	Night	23% 5% 21% 29% 19% 3	760
October	1st to 10th	Night	25% 7% 28% 24% 14% 2	760
	11th to 20th	Night	25% 11% 30% 26% 8%	760
	21st to end	Night	32% 13% 24% 23% 6% 1	836
November	1st to 10th	Night	28% 12% 29% 25% 6%	779
	11th to 20th	Night	27% 16% 34% 16% 7%	831
	21st to end	Night	25% 18% 31% 20% 6%	950
December	1st to 10th	Night	22% 19% 36% 17% 5% 1	950
	11th to 20th	Night	22% 17% 35% 20% 5% 2	950
	21st to end	Night	29% 15% 35% 17% 4	1045

Page generated at 2024-11-07 06:55:44. Version ac07

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