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 2025-02-06.

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% 11% 4 8% 5% 5% 4 4 5% 6% 31%	108530
	Night	18% 13% 4 9% 5% 4 4 3 5% 5% 28%	109711
Transparency	Day	52% 6% 13% 20% 8% 1	112030
	Night	57% 5% 11% 18% 8% 1	114375
Seeing	Day	25% 17% 29% 19% 8% 2	14767
	Night	26% 14% 29% 23% 8% 1	23965

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	16% 22% 7% 14% 6% 5% 4 2 4 4 17%	3597
	11th to 20th	Day	12% 17% 8% 16% 7% 5% 5% 3 4 5% 18%	3570
	21st to end	Day	13% 20% 7% 12% 6% 6% 4 3 5% 6% 18%	4066
February	1st to 10th	Day	15% 17% 4 12% 7% 5% 4 3 4 4 22%	1755
	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	16% 8% 3 7% 4 5% 5% 4 6% 8% 34%	4423
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 6% 8% 40%	3902
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 6% 8% 38%	4180
September	1st to 10th	Day	15% 5% 2 6% 4 5% 4 4 5% 7% 43%	2280
	11th to 20th	Day	14% 6% 2 5% 4 3 5% 3 4 6% 47%	2244
	21st to end	Day	18% 6% 2 6% 4 4 5% 4 5% 7% 39%	2085
October	1st to 10th	Day	21% 8% 2 6% 4 4 4 4 5% 6% 33%	1900
	11th to 20th	Day	19% 11% 3 9% 5% 5% 5% 3 5% 4 29%	1900
	21st to end	Day	26% 12% 3 8% 4 4 4 3 4 4 28%	1902
November	1st to 10th	Day	16% 11% 4 8% 5% 6% 5% 3 6% 7% 30%	1761
	11th to 20th	Day	17% 13% 3 8% 5% 5% 4 4 4 6% 30%	1676
	21st to end	Day	21% 16% 4 10% 6% 7% 4 3 5% 5% 20%	1600
December	1st to 10th	Day	20% 21% 8% 11% 6% 5% 4 4 5% 5% 13%	2600
	11th to 20th	Day	19% 17% 5% 11% 5% 4 4 4 5% 5% 21%	2986
	21st to end	Day	22% 16% 4 10% 6% 5% 4 3 5% 4 20%	3960
January	1st to 10th	Night	15% 23% 8% 14% 5% 4 3 2 3 4 17%	6349
	11th to 20th	Night	11% 20% 8% 16% 8% 6% 5% 4 4 4 14%	6315
	21st to end	Night	16% 19% 7% 11% 7% 6% 4 3 4 5% 18%	6886
February	1st to 10th	Night	16% 18% 6% 14% 6% 5% 4 3 4 4 20%	2536
	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	16% 9% 2 7% 4 4 4 3 5% 8% 37%	2506
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 3 5% 7% 38%	2890
	21st to end	Night	15% 6% 3 7% 4 4 4 4 6% 7% 40%	3476
September	1st to 10th	Night	15% 5% 3 7% 5% 4 4 4 5% 6% 42%	1900
	11th to 20th	Night	15% 5% 1 4 4 4 3 3 6% 7% 49%	1935
	21st to end	Night	17% 6% 2 7% 4 4 4 4 5% 6% 41%	2092
October	1st to 10th	Night	22% 7% 2 6% 4 5% 4 5% 5% 6% 34%	2280
	11th to 20th	Night	20% 10% 3 7% 5% 5% 4 4 5% 5% 33%	2280
	21st to end	Night	26% 10% 3 7% 5% 5% 4 3 5% 6% 27%	2694
November	1st to 10th	Night	20% 11% 4 7% 5% 4 4 3 5% 6% 32%	2537
	11th to 20th	Night	18% 12% 4 9% 5% 4 5% 3 5% 6% 31%	2720
	21st to end	Night	22% 15% 4 9% 5% 5% 4 3 4 6% 22%	2800
December	1st to 10th	Night	20% 22% 6% 12% 6% 5% 4 4 4 4 14%	4580
	11th to 20th	Night	24% 16% 4 10% 5% 4 4 2 4 4 21%	5208
	21st to end	Night	26% 17% 5% 11% 4 4 4 4 5% 4 17%	6996

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	73% 5% 9% 11% 2	3598
	11th to 20th	Day	71% 4 11% 8% 6%	3600
	21st to end	Day	69% 4 10% 9% 7% 1	4066
February	1st to 10th	Day	66% 4 9% 17% 4 1	1755
	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	47% 7% 16% 21% 9%	4409
	11th to 20th	Day	42% 6% 18% 28% 6%	3941
	21st to end	Day	42% 6% 18% 23% 10%	4180
September	1st to 10th	Day	39% 6% 14% 28% 12%	2280
	11th to 20th	Day	37% 5% 12% 32% 13% 1	2244
	21st to end	Day	43% 7% 15% 26% 9%	2085
October	1st to 10th	Day	46% 5% 13% 27% 9%	3160
	11th to 20th	Day	49% 5% 16% 24% 6%	3140
	21st to end	Day	49% 5% 17% 23% 6%	3114
November	1st to 10th	Day	53% 6% 13% 21% 6% 1	1761
	11th to 20th	Day	56% 5% 13% 16% 9% 1	1676
	21st to end	Day	67% 6% 13% 11% 3	1600
December	1st to 10th	Day	74% 5% 12% 8% 1	2600
	11th to 20th	Day	66% 5% 10% 14% 6%	2986
	21st to end	Day	68% 5% 8% 16% 4	3960
January	1st to 10th	Night	73% 5% 11% 9% 2	6349
	11th to 20th	Night	75% 5% 9% 8% 3	6360
	21st to end	Night	71% 4 8% 8% 8% 1	6886
February	1st to 10th	Night	68% 5% 9% 13% 5%	2536
	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	46% 6% 15% 25% 8%	2496
	11th to 20th	Night	46% 6% 16% 24% 8%	2917
	21st to end	Night	41% 6% 16% 24% 11% 1	3476
September	1st to 10th	Night	41% 7% 11% 27% 13% 1	1900
	11th to 20th	Night	34% 4 16% 33% 12% 1	1935
	21st to end	Night	43% 7% 11% 26% 12% 1	2092
October	1st to 10th	Night	45% 6% 13% 27% 8%	3800
	11th to 20th	Night	47% 4 16% 24% 9%	3779
	21st to end	Night	50% 5% 18% 19% 7%	4432
November	1st to 10th	Night	53% 6% 14% 19% 8% 1	2537
	11th to 20th	Night	54% 6% 12% 18% 8% 2	2720
	21st to end	Night	63% 6% 13% 13% 5%	2800
December	1st to 10th	Night	75% 5% 11% 8% 1	4580
	11th to 20th	Night	67% 3 8% 14% 7%	5208
	21st to end	Night	69% 4 7% 13% 7%	6996

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	34% 17% 30% 17% 3	200
	11th to 20th	Day	34% 22% 33% 7% 4 1	200
	21st to end	Day	23% 23% 34% 17% 3	241
February	1st to 10th	Day	41% 23% 28% 7% 1	285
	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	15% 13% 31% 24% 11% 6%	539
September	1st to 10th	Day	16% 12% 29% 23% 14% 6%	490
	11th to 20th	Day	13% 11% 24% 23% 19% 10%	490
	21st to end	Day	19% 13% 30% 21% 13% 4	490
October	1st to 10th	Day	26% 13% 27% 18% 12% 4	490
	11th to 20th	Day	25% 22% 29% 15% 7% 2	490
	21st to end	Day	34% 17% 27% 17% 5%	439
November	1st to 10th	Day	29% 18% 28% 17% 7%	395
	11th to 20th	Day	29% 24% 30% 13% 4 1	276
	21st to end	Day	35% 22% 31% 9% 4 1	200
December	1st to 10th	Day	33% 20% 24% 19% 5% 1	200
	11th to 20th	Day	34% 30% 24% 10% 2 1	200
	21st to end	Day	36% 22% 23% 14% 5%	220
January	1st to 10th	Night	32% 19% 30% 15% 3	800
	11th to 20th	Night	31% 20% 27% 18% 4	800
	21st to end	Night	23% 18% 33% 22% 4	880
February	1st to 10th	Night	27% 20% 32% 19% 2	781
	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% 7% 29% 30% 16% 2	836
September	1st to 10th	Night	15% 9% 29% 31% 15% 1	760
	11th to 20th	Night	18% 7% 22% 29% 20% 4	760
	21st to end	Night	19% 10% 26% 24% 18% 2	760
October	1st to 10th	Night	24% 11% 26% 23% 15% 1	760
	11th to 20th	Night	27% 11% 31% 21% 9%	760
	21st to end	Night	32% 14% 28% 21% 4	836
November	1st to 10th	Night	29% 18% 27% 19% 7% 1	780
	11th to 20th	Night	26% 19% 28% 19% 7% 1	800
	21st to end	Night	32% 19% 25% 19% 5%	800
December	1st to 10th	Night	35% 18% 28% 17% 3	800
	11th to 20th	Night	34% 19% 29% 14% 4 1	800
	21st to end	Night	37% 16% 28% 15% 4	880

Page generated at 2025-02-03 03:05:50. Version ac07

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