Massena
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Massena clear sky chart from 2005-11-06 to 2024-08-30.

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	17% 10% 3 8% 5% 5% 4 4 5% 6% 32%	95860
	Night	19% 12% 4 9% 5% 4 4 3 5% 6% 29%	93188
Transparency	Day	52% 6% 12% 20% 9% 1	95579
	Night	56% 6% 12% 18% 8% 1	93023
Seeing	Day	25% 17% 29% 19% 8% 2	14311
	Night	26% 14% 29% 23% 8% 1	23328

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% 19% 5% 12% 6% 5% 5% 3 4 5% 18%	2517
	11th to 20th	Day	14% 16% 7% 14% 7% 5% 5% 3 5% 6% 19%	2520
	21st to end	Day	15% 22% 6% 11% 7% 6% 5% 3 5% 6% 15%	2836
February	1st to 10th	Day	15% 17% 4 12% 7% 5% 4 3 5% 5% 22%	1710
	11th to 20th	Day	16% 15% 4 12% 7% 5% 4 3 5% 4 25%	1720
	21st to end	Day	20% 16% 4 9% 6% 5% 3 3 4 5% 23%	1570
March	1st to 10th	Day	21% 14% 4 8% 6% 4 3 3 4 5% 28%	3116
	11th to 20th	Day	15% 15% 5% 11% 6% 5% 4 3 5% 5% 27%	3402
	21st to end	Day	16% 8% 3 9% 5% 3 4 3 4 6% 39%	4090
April	1st to 10th	Day	22% 13% 3 6% 5% 4 4 3 4 5% 33%	2280
	11th to 20th	Day	22% 9% 3 7% 5% 4 4 2 4 6% 36%	2254
	21st to end	Day	23% 10% 3 6% 5% 4 4 3 5% 6% 32%	2376
May	1st to 10th	Day	20% 8% 3 9% 5% 4 5% 3 5% 6% 31%	4426
	11th to 20th	Day	17% 8% 3 8% 6% 4 5% 4 4 6% 34%	4398
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 6% 8% 37%	4837
June	1st to 10th	Day	22% 8% 3 6% 6% 5% 4 4 6% 7% 30%	2660
	11th to 20th	Day	15% 5% 2 7% 6% 4 4 5% 6% 8% 37%	2660
	21st to end	Day	21% 7% 3 6% 5% 4 5% 3 6% 8% 32%	2660
July	1st to 10th	Day	12% 6% 3 7% 5% 4 5% 4 7% 9% 37%	4440
	11th to 20th	Day	13% 6% 2 6% 5% 5% 6% 4 7% 8% 39%	4440
	21st to end	Day	12% 5% 2 6% 4 4 4 5% 7% 9% 42%	4814
August	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 4 7% 8% 37%	2646
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 5% 6% 8% 40%	2356
	21st to end	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 40%	2486
September	1st to 10th	Day	15% 5% 2 6% 4 5% 4 4 5% 7% 43%	2160
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 7% 47%	2126
	21st to end	Day	17% 6% 2 6% 4 4 5% 4 5% 7% 39%	1976
October	1st to 10th	Day	22% 7% 2 7% 5% 5% 5% 4 5% 6% 33%	1800
	11th to 20th	Day	20% 11% 4 9% 5% 5% 5% 4 5% 5% 28%	1800
	21st to end	Day	27% 12% 3 8% 4 4 4 3 4 4 27%	1802
November	1st to 10th	Day	16% 11% 4 8% 6% 6% 5% 3 5% 6% 30%	1671
	11th to 20th	Day	17% 13% 3 8% 5% 5% 5% 4 4 6% 29%	1593
	21st to end	Day	21% 15% 4 11% 6% 7% 4 3 5% 4 20%	1520
December	1st to 10th	Day	24% 18% 6% 10% 6% 5% 4 3 5% 5% 15%	1520
	11th to 20th	Day	22% 18% 5% 9% 5% 3 3 3 4 5% 21%	1906
	21st to end	Day	26% 19% 4 10% 5% 5% 3 2 4 3 19%	2772
January	1st to 10th	Night	19% 19% 6% 12% 6% 4 4 3 4 5% 19%	4429
	11th to 20th	Night	13% 17% 7% 15% 8% 6% 6% 4 5% 4 15%	4440
	21st to end	Night	19% 21% 7% 10% 7% 5% 3 2 3 5% 18%	4816
February	1st to 10th	Night	16% 17% 6% 13% 6% 5% 4 3 4 5% 19%	2470
	11th to 20th	Night	15% 14% 5% 12% 6% 5% 4 3 5% 5% 26%	2346
	21st to end	Night	17% 16% 4 10% 6% 3 4 3 4 4 29%	1884
March	1st to 10th	Night	22% 12% 3 7% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	20% 19% 4 9% 5% 3 3 2 4 5% 27%	3555
	21st to end	Night	16% 12% 3 8% 4 4 4 3 4 4 39%	3541
April	1st to 10th	Night	22% 11% 3 8% 5% 4 4 2 4 5% 31%	1900
	11th to 20th	Night	21% 10% 3 7% 4 4 4 3 5% 5% 33%	1875
	21st to end	Night	22% 10% 3 7% 4 4 3 3 5% 5% 34%	1815
May	1st to 10th	Night	22% 9% 3 8% 4 5% 5% 4 6% 7% 27%	2519
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 5% 6% 34%	2495
	21st to end	Night	15% 7% 2 6% 5% 4 4 3 7% 9% 39%	2738
June	1st to 10th	Night	19% 6% 2 7% 5% 5% 5% 5% 7% 8% 29%	1520
	11th to 20th	Night	16% 7% 2 6% 4 5% 4 3 6% 8% 39%	1520
	21st to end	Night	18% 8% 3 6% 5% 4 4 4 6% 8% 33%	1520
July	1st to 10th	Night	14% 7% 3 7% 6% 5% 5% 4 7% 8% 35%	2520
	11th to 20th	Night	15% 6% 2 6% 4 3 4 4 6% 8% 42%	2520
	21st to end	Night	12% 7% 2 7% 4 5% 5% 5% 6% 7% 40%	2739
August	1st to 10th	Night	13% 7% 2 6% 4 4 5% 4 6% 9% 41%	1512
	11th to 20th	Night	14% 6% 3 8% 5% 4 4 3 4 7% 42%	1741
	21st to end	Night	15% 6% 3 6% 4 4 4 4 6% 7% 42%	2080
September	1st to 10th	Night	15% 5% 3 7% 5% 4 4 4 5% 6% 42%	1800
	11th to 20th	Night	16% 5% 2 4 4 3 3 3 6% 7% 47%	1833
	21st to end	Night	17% 6% 2 7% 4 4 4 5% 5% 6% 41%	1981
October	1st to 10th	Night	22% 7% 2 6% 4 4 5% 5% 5% 6% 33%	2160
	11th to 20th	Night	20% 10% 3 7% 5% 5% 4 4 5% 5% 32%	2160
	21st to end	Night	26% 10% 3 7% 5% 5% 3 3 5% 6% 27%	2552
November	1st to 10th	Night	20% 11% 4 7% 5% 4 4 3 5% 6% 32%	2407
	11th to 20th	Night	18% 12% 4 9% 5% 4 5% 3 5% 6% 31%	2584
	21st to end	Night	23% 14% 4 9% 5% 5% 4 3 4 6% 23%	2660
December	1st to 10th	Night	23% 19% 5% 11% 6% 4 4 4 5% 4 16%	2660
	11th to 20th	Night	24% 17% 4 10% 5% 4 3 3 3 4 23%	3288
	21st to end	Night	31% 17% 5% 10% 4 4 3 2 3 4 17%	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	71% 5% 12% 9% 3	2518
	11th to 20th	Day	69% 5% 13% 8% 4 1	2520
	21st to end	Day	73% 5% 11% 7% 3 1	2836
February	1st to 10th	Day	66% 4 9% 16% 3 1	1710
	11th to 20th	Day	63% 4 12% 14% 6% 1	1729
	21st to end	Day	64% 5% 10% 13% 7% 1	1570
March	1st to 10th	Day	59% 5% 11% 18% 6% 1	3119
	11th to 20th	Day	59% 6% 12% 14% 7% 1	3402
	21st to end	Day	46% 4 10% 22% 15% 3	4090
April	1st to 10th	Day	56% 4 7% 20% 10% 2	2280
	11th to 20th	Day	52% 4 8% 19% 15% 2	2254
	21st to end	Day	54% 4 10% 16% 13% 3	2376
May	1st to 10th	Day	53% 6% 10% 20% 9% 1	4440
	11th to 20th	Day	51% 7% 13% 19% 9% 1	4402
	21st to end	Day	42% 7% 13% 24% 13% 1	4837
June	1st to 10th	Day	52% 7% 12% 18% 11% 1	2660
	11th to 20th	Day	44% 7% 11% 26% 10% 2	2660
	21st to end	Day	50% 8% 11% 20% 10% 1	2660
July	1st to 10th	Day	41% 6% 15% 28% 10% 1	4370
	11th to 20th	Day	40% 7% 16% 30% 7%	4365
	21st to end	Day	37% 8% 15% 32% 9%	4661
August	1st to 10th	Day	43% 9% 16% 23% 9%	2632
	11th to 20th	Day	39% 8% 19% 25% 9%	2356
	21st to end	Day	41% 7% 15% 26% 11%	2486
September	1st to 10th	Day	40% 6% 14% 27% 13%	2160
	11th to 20th	Day	38% 5% 12% 32% 12% 1	2126
	21st to end	Day	43% 7% 14% 26% 9%	1976
October	1st to 10th	Day	51% 5% 13% 21% 10%	1800
	11th to 20th	Day	58% 7% 15% 15% 6% 1	1800
	21st to end	Day	61% 5% 11% 15% 7%	1802
November	1st to 10th	Day	52% 6% 14% 21% 6% 1	1671
	11th to 20th	Day	57% 5% 13% 16% 8% 2	1593
	21st to end	Day	67% 6% 14% 10% 4	1520
December	1st to 10th	Day	72% 6% 12% 8% 2	1520
	11th to 20th	Day	67% 5% 12% 13% 3	1906
	21st to end	Day	72% 5% 7% 14% 2	2772
January	1st to 10th	Night	69% 6% 13% 9% 3	4429
	11th to 20th	Night	73% 5% 11% 8% 3	4440
	21st to end	Night	72% 5% 10% 9% 4 1	4816
February	1st to 10th	Night	68% 5% 9% 12% 5%	2470
	11th to 20th	Night	62% 5% 10% 18% 6%	2348
	21st to end	Night	60% 5% 10% 16% 9% 1	1884
March	1st to 10th	Night	55% 6% 9% 22% 8% 1	3734
	11th to 20th	Night	61% 5% 14% 13% 6% 1	3556
	21st to end	Night	50% 4 7% 24% 13% 3	3541
April	1st to 10th	Night	56% 4 8% 19% 11% 1	1900
	11th to 20th	Night	53% 4 9% 19% 13% 1	1875
	21st to end	Night	52% 4 9% 18% 14% 4	1815
May	1st to 10th	Night	54% 7% 11% 17% 9% 2	2525
	11th to 20th	Night	50% 7% 11% 20% 10% 1	2496
	21st to end	Night	41% 7% 13% 21% 17% 1	2739
June	1st to 10th	Night	50% 8% 13% 17% 11% 1	1520
	11th to 20th	Night	43% 6% 13% 22% 16% 1	1520
	21st to end	Night	49% 8% 13% 19% 12%	1520
July	1st to 10th	Night	45% 6% 14% 21% 14% 1	2480
	11th to 20th	Night	39% 6% 16% 31% 8%	2472
	21st to end	Night	42% 7% 16% 23% 12%	2651
August	1st to 10th	Night	40% 8% 17% 24% 11%	1502
	11th to 20th	Night	44% 5% 14% 24% 12% 1	1741
	21st to end	Night	39% 7% 16% 27% 10% 1	2080
September	1st to 10th	Night	41% 7% 11% 26% 13% 1	1800
	11th to 20th	Night	36% 5% 15% 33% 11% 1	1833
	21st to end	Night	43% 7% 11% 27% 12% 1	1981
October	1st to 10th	Night	50% 6% 11% 22% 10% 1	2160
	11th to 20th	Night	53% 5% 14% 19% 8%	2160
	21st to end	Night	59% 6% 14% 14% 6% 1	2552
November	1st to 10th	Night	53% 6% 14% 19% 8% 1	2407
	11th to 20th	Night	54% 7% 12% 18% 7% 2	2584
	21st to end	Night	64% 6% 13% 13% 5%	2660
December	1st to 10th	Night	72% 5% 11% 10% 2	2660
	11th to 20th	Night	67% 3 10% 15% 4	3288
	21st to end	Night	73% 5% 8% 12% 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	36% 16% 26% 19% 3	180
	11th to 20th	Day	34% 23% 31% 7% 4 1	180
	21st to end	Day	24% 22% 32% 18% 3	216
February	1st to 10th	Day	42% 23% 27% 7% 1	270
	11th to 20th	Day	31% 26% 35% 7%	327
	21st to end	Day	35% 21% 30% 13% 1	382
March	1st to 10th	Day	30% 23% 29% 14% 4	460
	11th to 20th	Day	31% 22% 32% 12% 2 1	460
	21st to end	Day	35% 22% 23% 13% 6% 1	506
April	1st to 10th	Day	37% 18% 26% 16% 3 1	460
	11th to 20th	Day	35% 20% 25% 13% 5% 2	452
	21st to end	Day	33% 20% 28% 10% 7% 1	460
May	1st to 10th	Day	27% 19% 32% 15% 7% 1	463
	11th to 20th	Day	19% 20% 32% 17% 11% 1	487
	21st to end	Day	21% 18% 30% 22% 9% 1	529
June	1st to 10th	Day	26% 17% 28% 21% 6% 2	490
	11th to 20th	Day	17% 15% 32% 26% 8% 2	490
	21st to end	Day	25% 16% 31% 18% 9% 1	490
July	1st to 10th	Day	13% 11% 31% 29% 13% 2	485
	11th to 20th	Day	15% 10% 33% 29% 10% 2	484
	21st to end	Day	16% 7% 36% 29% 10% 2	532
August	1st to 10th	Day	17% 10% 25% 31% 13% 3	486
	11th to 20th	Day	16% 7% 30% 27% 15% 6%	479
	21st to end	Day	14% 13% 31% 25% 11% 6%	532
September	1st to 10th	Day	15% 13% 29% 23% 13% 6%	450
	11th to 20th	Day	15% 12% 25% 24% 16% 8%	450
	21st to end	Day	19% 14% 31% 21% 12% 4	450
October	1st to 10th	Day	26% 14% 26% 17% 13% 4	450
	11th to 20th	Day	26% 22% 29% 15% 6% 2	450
	21st to end	Day	36% 17% 26% 17% 5%	405
November	1st to 10th	Day	28% 18% 28% 17% 8%	365
	11th to 20th	Day	30% 23% 30% 11% 4 1	253
	21st to end	Day	33% 21% 31% 10% 4 1	180
December	1st to 10th	Day	33% 21% 24% 17% 4 1	180
	11th to 20th	Day	34% 31% 24% 10% 1 1	180
	21st to end	Day	39% 24% 22% 12% 3	198
January	1st to 10th	Night	33% 20% 29% 16% 3	760
	11th to 20th	Night	31% 20% 27% 18% 4	760
	21st to end	Night	24% 18% 32% 22% 4	836
February	1st to 10th	Night	27% 21% 31% 19% 2	760
	11th to 20th	Night	25% 21% 34% 18% 2	743
	21st to end	Night	29% 18% 30% 22% 2	628
March	1st to 10th	Night	29% 18% 29% 20% 4	760
	11th to 20th	Night	31% 19% 30% 17% 3	760
	21st to end	Night	27% 17% 27% 23% 6%	836
April	1st to 10th	Night	31% 15% 30% 22% 3	760
	11th to 20th	Night	30% 17% 29% 19% 6%	751
	21st to end	Night	29% 15% 29% 20% 7%	675
May	1st to 10th	Night	28% 11% 31% 22% 7% 1	385
	11th to 20th	Night	22% 11% 33% 27% 6%	374
	21st to end	Night	16% 9% 40% 25% 10%	411
June	1st to 10th	Night	19% 8% 32% 33% 6% 1	380
	11th to 20th	Night	19% 11% 27% 31% 12% 1	380
	21st to end	Night	20% 9% 30% 29% 11% 1	380
July	1st to 10th	Night	11% 6% 30% 41% 12% 1	370
	11th to 20th	Night	14% 5% 29% 37% 15%	368
	21st to end	Night	14% 6% 32% 38% 10% 1	416
August	1st to 10th	Night	13% 6% 24% 40% 16% 1	378
	11th to 20th	Night	17% 5% 23% 36% 18% 1	617
	21st to end	Night	16% 6% 29% 30% 16% 2	832
September	1st to 10th	Night	16% 9% 29% 30% 15% 1	720
	11th to 20th	Night	19% 7% 23% 30% 18% 3	720
	21st to end	Night	20% 11% 27% 23% 18% 2	720
October	1st to 10th	Night	25% 11% 27% 22% 14% 1	720
	11th to 20th	Night	27% 12% 32% 21% 9%	720
	21st to end	Night	33% 14% 28% 21% 4	792
November	1st to 10th	Night	29% 17% 27% 19% 7% 1	740
	11th to 20th	Night	26% 20% 28% 18% 7% 1	760
	21st to end	Night	32% 18% 25% 19% 5%	760
December	1st to 10th	Night	35% 19% 27% 16% 3	760
	11th to 20th	Night	34% 19% 29% 13% 4 1	760
	21st to end	Night	38% 16% 28% 14% 3	836

Page generated at 2024-08-27 09:49:40. Version ac07

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