Lunenburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lunenburg clear sky chart from 2005-11-06 to 2024-12-09.

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	19% 9% 3 8% 5% 5% 5% 4 6% 7% 31%	102197
	Night	20% 9% 3 8% 5% 4 5% 4 5% 7% 30%	97639
Transparency	Day	51% 8% 12% 18% 10% 1	105799
	Night	53% 7% 12% 18% 10% 1	102128
Seeing	Day	24% 14% 32% 23% 7% 1	17393
	Night	25% 13% 31% 23% 7% 1	24963

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	17% 9% 3 10% 6% 5% 6% 5% 5% 7% 27%	2526
	11th to 20th	Day	16% 11% 4 10% 7% 7% 6% 6% 7% 7% 19%	2689
	21st to end	Day	20% 9% 4 9% 5% 5% 5% 4 6% 7% 26%	3124
February	1st to 10th	Day	20% 13% 5% 9% 5% 6% 5% 5% 5% 6% 22%	1710
	11th to 20th	Day	17% 9% 4 10% 7% 7% 6% 4 6% 6% 24%	1663
	21st to end	Day	13% 11% 4 7% 7% 5% 4 3 6% 8% 32%	1448
March	1st to 10th	Day	25% 13% 3 7% 5% 5% 4 3 4 5% 26%	3430
	11th to 20th	Day	15% 11% 4 8% 6% 6% 4 3 6% 7% 29%	3480
	21st to end	Day	30% 9% 4 11% 6% 4 4 3 4 4 22%	3816
April	1st to 10th	Day	24% 11% 4 9% 5% 5% 4 3 4 5% 28%	2253
	11th to 20th	Day	19% 9% 3 7% 4 3 4 4 6% 6% 35%	2331
	21st to end	Day	21% 8% 2 7% 5% 4 4 3 5% 7% 33%	2470
May	1st to 10th	Day	22% 9% 4 8% 6% 4 5% 4 5% 7% 25%	4136
	11th to 20th	Day	23% 11% 3 7% 5% 4 4 3 5% 5% 30%	4398
	21st to end	Day	18% 9% 2 6% 4 4 5% 4 6% 9% 33%	4836
June	1st to 10th	Day	24% 9% 3 7% 5% 5% 5% 3 5% 8% 26%	2660
	11th to 20th	Day	20% 9% 3 7% 5% 4 4 3 5% 6% 36%	2728
	21st to end	Day	24% 10% 3 8% 5% 5% 4 4 6% 7% 25%	2850
July	1st to 10th	Day	18% 8% 3 8% 5% 5% 4 5% 6% 9% 28%	4600
	11th to 20th	Day	10% 8% 3 11% 6% 6% 6% 4 6% 9% 32%	4440
	21st to end	Day	18% 9% 3 7% 4 4 4 4 6% 8% 33%	4579
August	1st to 10th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 8% 28%	4105
	11th to 20th	Day	13% 9% 4 7% 4 4 5% 4 6% 9% 35%	4045
	21st to end	Day	8% 5% 2 5% 4 4 5% 5% 6% 9% 49%	4356
September	1st to 10th	Day	14% 6% 2 5% 3 4 4 4 5% 7% 45%	2280
	11th to 20th	Day	17% 6% 2 7% 3 4 5% 3 5% 5% 45%	2183
	21st to end	Day	17% 7% 2 6% 4 4 5% 4 3 6% 42%	2043
October	1st to 10th	Day	18% 6% 2 6% 4 4 5% 4 6% 7% 39%	1900
	11th to 20th	Day	18% 7% 2 6% 4 3 5% 4 7% 8% 36%	1900
	21st to end	Day	20% 8% 3 6% 5% 4 5% 3 5% 6% 33%	2090
November	1st to 10th	Day	19% 10% 3 9% 5% 4 4 3 5% 6% 32%	1655
	11th to 20th	Day	22% 9% 3 7% 5% 5% 5% 5% 6% 7% 27%	1600
	21st to end	Day	20% 10% 4 9% 6% 5% 5% 3 5% 6% 27%	1600
December	1st to 10th	Day	24% 12% 3 9% 6% 5% 5% 5% 6% 6% 20%	1584
	11th to 20th	Day	31% 11% 2 6% 5% 4 6% 5% 7% 7% 18%	1906
	21st to end	Day	23% 9% 4 8% 5% 4 4 3 5% 8% 25%	2783
January	1st to 10th	Night	15% 10% 4 9% 6% 6% 6% 5% 7% 7% 25%	4429
	11th to 20th	Night	17% 10% 4 11% 8% 7% 6% 5% 6% 7% 20%	4271
	21st to end	Night	18% 13% 4 9% 6% 5% 5% 5% 6% 8% 22%	4532
February	1st to 10th	Night	20% 12% 4 8% 6% 5% 6% 5% 6% 6% 22%	2470
	11th to 20th	Night	16% 9% 3 10% 6% 6% 5% 5% 7% 8% 24%	2403
	21st to end	Night	13% 11% 3 9% 7% 5% 5% 4 7% 6% 31%	2003
March	1st to 10th	Night	24% 12% 3 7% 5% 5% 4 3 4 6% 27%	3410
	11th to 20th	Night	17% 10% 4 10% 6% 5% 5% 4 6% 6% 25%	3479
	21st to end	Night	32% 10% 4 10% 4 2 3 2 3 4 25%	3816
April	1st to 10th	Night	24% 12% 3 6% 4 5% 4 3 5% 6% 28%	1926
	11th to 20th	Night	23% 8% 2 7% 4 4 5% 3 4 7% 33%	1797
	21st to end	Night	25% 9% 3 6% 5% 3 4 4 5% 5% 32%	1710
May	1st to 10th	Night	20% 13% 4 9% 5% 4 4 3 5% 6% 27%	2803
	11th to 20th	Night	28% 10% 3 6% 5% 5% 4 3 4 6% 28%	2506
	21st to end	Night	19% 12% 4 7% 5% 4 4 4 4 6% 31%	2749
June	1st to 10th	Night	26% 8% 2 7% 5% 4 4 3 5% 7% 28%	1520
	11th to 20th	Night	21% 8% 3 6% 3 4 4 4 5% 8% 34%	1462
	21st to end	Night	27% 11% 4 6% 4 5% 5% 3 5% 5% 26%	1330
July	1st to 10th	Night	17% 10% 4 8% 5% 5% 5% 5% 6% 8% 26%	2330
	11th to 20th	Night	13% 8% 3 11% 6% 5% 5% 4 7% 9% 28%	2530
	21st to end	Night	18% 8% 3 7% 4 4 5% 4 5% 7% 36%	2962
August	1st to 10th	Night	17% 8% 3 8% 6% 5% 4 4 5% 7% 34%	2825
	11th to 20th	Night	14% 9% 4 7% 4 4 4 3 6% 7% 37%	2782
	21st to end	Night	9% 5% 2 5% 3 4 4 4 5% 8% 52%	3298
September	1st to 10th	Night	13% 6% 2 6% 4 3 4 3 5% 7% 45%	1900
	11th to 20th	Night	16% 9% 2 5% 3 3 3 3 4 6% 45%	1995
	21st to end	Night	19% 9% 2 6% 4 4 4 3 4 7% 38%	2136
October	1st to 10th	Night	18% 6% 2 6% 5% 3 4 3 5% 7% 41%	2280
	11th to 20th	Night	19% 5% 2 6% 3 4 4 4 6% 8% 40%	2280
	21st to end	Night	22% 8% 2 5% 4 4 4 4 5% 6% 36%	2508
November	1st to 10th	Night	18% 7% 3 7% 5% 4 4 3 5% 7% 35%	2641
	11th to 20th	Night	19% 9% 4 7% 5% 5% 5% 4 6% 7% 29%	2800
	21st to end	Night	22% 8% 3 6% 5% 5% 5% 4 6% 7% 28%	2800
December	1st to 10th	Night	22% 12% 3 8% 6% 5% 5% 3 6% 7% 22%	2779
	11th to 20th	Night	30% 11% 3 7% 4 4 4 3 5% 6% 22%	3293
	21st to end	Night	24% 9% 3 8% 5% 4 4 4 6% 6% 27%	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	56% 7% 18% 14% 5%	2527
	11th to 20th	Day	58% 11% 12% 15% 4	2689
	21st to end	Day	55% 7% 11% 17% 9%	3124
February	1st to 10th	Day	61% 6% 13% 13% 7% 1	1710
	11th to 20th	Day	58% 8% 11% 16% 7% 1	1671
	21st to end	Day	49% 8% 13% 18% 9% 3	1448
March	1st to 10th	Day	60% 5% 9% 16% 8% 2	3434
	11th to 20th	Day	48% 12% 13% 17% 9% 1	3480
	21st to end	Day	63% 5% 8% 12% 10% 2	3816
April	1st to 10th	Day	57% 6% 9% 14% 12% 2	2253
	11th to 20th	Day	47% 8% 10% 21% 13% 1	2331
	21st to end	Day	48% 7% 11% 17% 13% 3	2470
May	1st to 10th	Day	57% 10% 12% 15% 6% 1	4150
	11th to 20th	Day	55% 9% 10% 18% 8% 1	4402
	21st to end	Day	47% 9% 16% 17% 10% 1	4836
June	1st to 10th	Day	56% 8% 10% 17% 8%	2660
	11th to 20th	Day	48% 9% 11% 18% 12% 2	2728
	21st to end	Day	59% 8% 9% 14% 9% 1	2850
July	1st to 10th	Day	54% 10% 11% 12% 12% 2	4530
	11th to 20th	Day	48% 11% 13% 20% 8%	4364
	21st to end	Day	49% 10% 12% 18% 10% 1	4433
August	1st to 10th	Day	55% 9% 11% 16% 8% 1	4092
	11th to 20th	Day	45% 9% 16% 22% 8%	4084
	21st to end	Day	29% 9% 13% 29% 19% 1	4356
September	1st to 10th	Day	38% 8% 13% 23% 16% 2	2280
	11th to 20th	Day	42% 7% 9% 24% 17% 2	2183
	21st to end	Day	42% 7% 9% 24% 17% 1	2043
October	1st to 10th	Day	42% 8% 11% 26% 12% 1	3160
	11th to 20th	Day	36% 6% 11% 25% 22%	3140
	21st to end	Day	43% 6% 15% 21% 12% 3	3428
November	1st to 10th	Day	51% 7% 11% 20% 9% 1	1655
	11th to 20th	Day	55% 7% 13% 16% 7% 1	1600
	21st to end	Day	58% 6% 14% 16% 6%	1600
December	1st to 10th	Day	62% 7% 11% 14% 4 1	1584
	11th to 20th	Day	63% 8% 11% 12% 7%	1905
	21st to end	Day	57% 6% 20% 12% 4 1	2783
January	1st to 10th	Night	58% 7% 14% 18% 3	4429
	11th to 20th	Night	59% 10% 14% 11% 5%	4271
	21st to end	Night	59% 8% 13% 14% 7%	4532
February	1st to 10th	Night	61% 8% 11% 11% 8% 1	2470
	11th to 20th	Night	58% 7% 12% 15% 7% 1	2406
	21st to end	Night	52% 7% 15% 17% 8% 1	2003
March	1st to 10th	Night	60% 5% 9% 15% 10% 1	3419
	11th to 20th	Night	55% 9% 12% 15% 8% 1	3480
	21st to end	Night	63% 4 8% 14% 9% 2	3816
April	1st to 10th	Night	56% 6% 8% 15% 12% 3	1926
	11th to 20th	Night	51% 5% 9% 19% 14% 2	1797
	21st to end	Night	53% 6% 9% 18% 12% 3	1710
May	1st to 10th	Night	57% 8% 11% 16% 7%	2809
	11th to 20th	Night	57% 7% 8% 20% 7% 1	2507
	21st to end	Night	53% 8% 11% 20% 7% 1	2750
June	1st to 10th	Night	55% 6% 11% 19% 8%	1520
	11th to 20th	Night	50% 6% 11% 20% 11% 1	1462
	21st to end	Night	61% 6% 10% 13% 9% 1	1330
July	1st to 10th	Night	57% 8% 12% 13% 9% 1	2292
	11th to 20th	Night	55% 12% 9% 14% 9% 1	2482
	21st to end	Night	49% 8% 12% 18% 12% 1	2869
August	1st to 10th	Night	52% 6% 13% 20% 9%	2813
	11th to 20th	Night	46% 8% 16% 22% 8%	2809
	21st to end	Night	30% 5% 15% 28% 21%	3297
September	1st to 10th	Night	39% 8% 9% 26% 16% 2	1900
	11th to 20th	Night	40% 5% 8% 28% 17% 1	1995
	21st to end	Night	48% 4 8% 24% 14% 1	2136
October	1st to 10th	Night	45% 6% 11% 25% 12% 1	3800
	11th to 20th	Night	33% 6% 12% 28% 21%	3779
	21st to end	Night	40% 5% 12% 24% 17% 1	4120
November	1st to 10th	Night	49% 7% 13% 19% 11% 1	2641
	11th to 20th	Night	53% 7% 14% 17% 8%	2800
	21st to end	Night	55% 7% 17% 16% 5%	2800
December	1st to 10th	Night	61% 7% 13% 15% 3	2779
	11th to 20th	Night	65% 5% 11% 14% 5%	3295
	21st to end	Night	57% 6% 14% 17% 5%	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	27% 23% 34% 13% 3	370
	11th to 20th	Day	28% 21% 33% 14% 4	370
	21st to end	Day	21% 21% 35% 21% 2	407
February	1st to 10th	Day	26% 23% 33% 15% 2	370
	11th to 20th	Day	25% 28% 31% 15% 2	366
	21st to end	Day	19% 22% 36% 20% 3 1	316
March	1st to 10th	Day	25% 22% 34% 16% 2	460
	11th to 20th	Day	20% 24% 36% 15% 4 1	460
	21st to end	Day	28% 20% 32% 14% 6%	506
April	1st to 10th	Day	31% 22% 31% 13% 4	460
	11th to 20th	Day	23% 13% 44% 16% 3	452
	21st to end	Day	22% 16% 34% 19% 8%	460
May	1st to 10th	Day	28% 14% 35% 18% 4 1	480
	11th to 20th	Day	21% 12% 33% 27% 7% 1	674
	21st to end	Day	26% 8% 35% 25% 5% 1	735
June	1st to 10th	Day	28% 8% 31% 26% 7%	680
	11th to 20th	Day	23% 7% 31% 30% 8% 1	680
	21st to end	Day	33% 5% 27% 25% 8% 1	680
July	1st to 10th	Day	24% 4 29% 31% 11%	670
	11th to 20th	Day	22% 4 28% 32% 13% 1	668
	21st to end	Day	22% 6% 28% 32% 11% 1	605
August	1st to 10th	Day	16% 7% 27% 36% 12% 2	486
	11th to 20th	Day	19% 7% 30% 25% 18% 2	479
	21st to end	Day	16% 6% 28% 31% 15% 4	539
September	1st to 10th	Day	17% 6% 32% 33% 11% 2	490
	11th to 20th	Day	21% 10% 27% 25% 12% 4	490
	21st to end	Day	22% 5% 35% 24% 12% 2	465
October	1st to 10th	Day	21% 8% 31% 26% 11% 3	390
	11th to 20th	Day	19% 16% 31% 23% 9% 2	390
	21st to end	Day	24% 16% 34% 19% 7% 1	429
November	1st to 10th	Day	21% 16% 34% 20% 7% 1	395
	11th to 20th	Day	28% 24% 29% 14% 6%	400
	21st to end	Day	28% 20% 35% 14% 4 1	400
December	1st to 10th	Day	32% 19% 28% 18% 4	394
	11th to 20th	Day	31% 28% 27% 13% 1	370
	21st to end	Day	29% 24% 29% 14% 3	407
January	1st to 10th	Night	27% 21% 34% 16% 3	850
	11th to 20th	Night	27% 20% 31% 18% 3	801
	21st to end	Night	23% 21% 35% 17% 4	836
February	1st to 10th	Night	28% 18% 33% 18% 2	760
	11th to 20th	Night	23% 24% 35% 15% 2	743
	21st to end	Night	19% 17% 39% 20% 5%	628
March	1st to 10th	Night	25% 17% 37% 17% 3	760
	11th to 20th	Night	23% 16% 31% 23% 6%	760
	21st to end	Night	24% 19% 32% 20% 6%	836
April	1st to 10th	Night	32% 14% 30% 21% 4	596
	11th to 20th	Night	26% 10% 40% 18% 5%	564
	21st to end	Night	30% 10% 29% 23% 7% 1	570
May	1st to 10th	Night	29% 9% 30% 25% 5% 1	570
	11th to 20th	Night	29% 6% 29% 26% 9% 1	562
	21st to end	Night	22% 7% 33% 28% 8% 1	616
June	1st to 10th	Night	31% 5% 28% 28% 8%	570
	11th to 20th	Night	24% 6% 28% 33% 8% 1	512
	21st to end	Night	33% 5% 18% 32% 11% 1	380
July	1st to 10th	Night	21% 5% 26% 35% 12% 1	435
	11th to 20th	Night	21% 4 25% 34% 15% 1	552
	21st to end	Night	22% 4 22% 39% 14%	623
August	1st to 10th	Night	17% 3 22% 36% 19% 2	568
	11th to 20th	Night	19% 5% 23% 32% 19% 2	562
	21st to end	Night	17% 5% 24% 34% 18% 2	627
September	1st to 10th	Night	16% 6% 28% 35% 13% 1	570
	11th to 20th	Night	21% 7% 26% 27% 16% 2	665
	21st to end	Night	24% 9% 28% 26% 11% 2	760
October	1st to 10th	Night	22% 8% 30% 29% 10% 1	760
	11th to 20th	Night	20% 13% 34% 22% 10% 2	760
	21st to end	Night	27% 14% 31% 22% 6%	836
November	1st to 10th	Night	23% 14% 32% 24% 5% 2	853
	11th to 20th	Night	26% 21% 27% 20% 5%	900
	21st to end	Night	27% 19% 31% 18% 5%	900
December	1st to 10th	Night	29% 17% 34% 15% 5%	893
	11th to 20th	Night	29% 23% 33% 13% 3	850
	21st to end	Night	29% 18% 33% 17% 3	935

Page generated at 2024-12-06 04:54:52. Version ac07

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