Leominster
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leominster clear sky chart from 2005-11-06 to 2024-11-05.

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	16% 7% 2 6% 4 4 5% 4 6% 7% 38%	101264
	Night	17% 8% 2 6% 4 4 4 3 5% 7% 40%	97781
Transparency	Day	43% 7% 12% 22% 14% 2	104802
	Night	43% 6% 12% 22% 15% 2	102332
Seeing	Day	23% 17% 32% 19% 8% 2	15000
	Night	22% 15% 34% 23% 6%	23913

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	12% 7% 3 7% 5% 4 4 3 5% 6% 44%	2517
	11th to 20th	Day	16% 7% 3 8% 4 4 5% 4 5% 5% 39%	2520
	21st to end	Day	20% 11% 3 6% 4 4 4 3 4 5% 34%	2772
February	1st to 10th	Day	17% 7% 2 6% 5% 4 6% 3 6% 7% 36%	1759
	11th to 20th	Day	12% 8% 3 7% 4 4 6% 4 6% 7% 39%	1848
	21st to end	Day	18% 11% 2 6% 5% 4 4 3 6% 4 37%	1570
March	1st to 10th	Day	22% 14% 2 7% 4 4 4 3 4 5% 31%	3116
	11th to 20th	Day	12% 8% 2 4 4 4 5% 5% 6% 8% 41%	3306
	21st to end	Day	20% 9% 3 6% 4 4 4 3 6% 7% 35%	4070
April	1st to 10th	Day	17% 10% 2 6% 6% 4 4 3 4 6% 36%	2280
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 5% 7% 39%	2254
	21st to end	Day	20% 7% 2 7% 5% 4 5% 3 5% 6% 36%	2465
May	1st to 10th	Day	23% 11% 3 8% 5% 5% 4 4 5% 6% 27%	4106
	11th to 20th	Day	23% 8% 3 8% 4 4 4 3 4 6% 33%	4222
	21st to end	Day	14% 5% 2 5% 4 4 4 4 6% 9% 44%	4837
June	1st to 10th	Day	19% 5% 2 6% 5% 4 5% 4 7% 8% 35%	2660
	11th to 20th	Day	16% 5% 2 5% 5% 5% 4 5% 7% 9% 37%	2660
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	2660
July	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 9% 37%	4440
	11th to 20th	Day	11% 5% 1 6% 4 5% 6% 4 7% 10% 40%	4440
	21st to end	Day	17% 7% 3 7% 4 5% 5% 4 5% 8% 35%	4814
August	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 5% 7% 9% 34%	4206
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 5% 8% 37%	3950
	21st to end	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 45%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 5% 3 6% 7% 46%	2280
	11th to 20th	Day	16% 5% 2 5% 3 3 4 2 5% 6% 50%	2104
	21st to end	Day	16% 6% 2 6% 4 5% 4 2 5% 7% 43%	2090
October	1st to 10th	Day	23% 6% 1 6% 4 4 4 3 4 6% 39%	2090
	11th to 20th	Day	13% 6% 3 5% 4 3 4 3 6% 8% 46%	1845
	21st to end	Day	21% 6% 3 6% 4 3 4 3 4 6% 40%	1881
November	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 4 4 49%	1708
	11th to 20th	Day	18% 7% 2 4 4 4 3 3 4 5% 47%	1710
	21st to end	Day	17% 7% 2 5% 5% 4 4 3 5% 5% 43%	1706
December	1st to 10th	Day	17% 8% 2 7% 4 4 5% 4 6% 5% 37%	1520
	11th to 20th	Day	22% 7% 2 3 3 3 3 3 5% 5% 45%	1906
	21st to end	Day	20% 11% 3 7% 4 3 4 3 5% 7% 33%	2772
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 5% 6% 46%	4429
	11th to 20th	Night	13% 9% 3 9% 5% 4 4 3 4 6% 39%	4440
	21st to end	Night	21% 12% 4 8% 5% 4 4 3 4 5% 30%	4884
February	1st to 10th	Night	15% 9% 3 6% 4 4 4 4 6% 6% 39%	2417
	11th to 20th	Night	12% 8% 3 6% 4 4 5% 4 5% 7% 41%	2218
	21st to end	Night	15% 10% 3 6% 4 3 4 3 5% 6% 40%	1884
March	1st to 10th	Night	25% 11% 2 5% 4 4 3 3 4 6% 33%	3724
	11th to 20th	Night	11% 9% 3 6% 5% 5% 5% 4 6% 7% 39%	3652
	21st to end	Night	22% 8% 2 5% 3 3 4 4 6% 6% 35%	3544
April	1st to 10th	Night	17% 8% 2 6% 6% 4 4 3 5% 7% 36%	1900
	11th to 20th	Night	19% 5% 2 6% 4 3 4 4 5% 7% 39%	1875
	21st to end	Night	20% 7% 2 7% 4 4 3 2 5% 6% 40%	1715
May	1st to 10th	Night	25% 11% 3 7% 4 4 3 3 5% 7% 27%	2834
	11th to 20th	Night	21% 9% 3 7% 5% 4 5% 4 6% 6% 28%	2700
	21st to end	Night	16% 6% 2 5% 4 4 4 4 5% 7% 42%	2738
June	1st to 10th	Night	19% 8% 3 6% 4 4 3 3 6% 7% 38%	1520
	11th to 20th	Night	19% 7% 2 6% 5% 4 4 3 6% 8% 38%	1520
	21st to end	Night	15% 6% 2 6% 4 4 5% 3 7% 8% 41%	1520
July	1st to 10th	Night	11% 5% 2 7% 5% 5% 6% 4 7% 9% 37%	2520
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 4 6% 8% 43%	2520
	21st to end	Night	16% 7% 2 6% 4 5% 5% 4 4 7% 39%	2739
August	1st to 10th	Night	19% 6% 2 7% 4 4 6% 4 6% 8% 34%	2692
	11th to 20th	Night	13% 6% 3 7% 5% 6% 6% 4 6% 7% 37%	2873
	21st to end	Night	10% 4 1 5% 3 3 3 3 5% 7% 58%	3476
September	1st to 10th	Night	14% 6% 2 4 4 4 4 3 6% 7% 49%	1900
	11th to 20th	Night	13% 6% 2 4 3 4 3 2 5% 6% 53%	2076
	21st to end	Night	16% 5% 2 6% 3 3 4 3 5% 6% 45%	2090
October	1st to 10th	Night	21% 6% 2 5% 3 3 4 3 5% 5% 43%	2090
	11th to 20th	Night	15% 5% 1 5% 4 3 4 3 5% 7% 47%	2332
	21st to end	Night	22% 6% 2 5% 4 4 3 3 5% 7% 39%	2717
November	1st to 10th	Night	14% 6% 1 6% 4 4 3 4 4 5% 49%	2470
	11th to 20th	Night	17% 7% 2 4 4 4 4 3 4 5% 46%	2470
	21st to end	Night	15% 7% 2 5% 4 4 3 4 5% 7% 45%	2470
December	1st to 10th	Night	17% 8% 2 5% 4 4 4 4 5% 6% 39%	2660
	11th to 20th	Night	19% 6% 2 5% 3 4 4 3 6% 6% 41%	3288
	21st to end	Night	20% 9% 3 6% 4 4 3 3 5% 6% 36%	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	40% 6% 9% 33% 10% 2	2518
	11th to 20th	Day	46% 6% 9% 25% 12% 2	2520
	21st to end	Day	51% 6% 10% 21% 10% 2	2772
February	1st to 10th	Day	46% 7% 13% 20% 12% 2	1759
	11th to 20th	Day	44% 6% 11% 21% 15% 3	1857
	21st to end	Day	49% 5% 9% 20% 14% 3	1570
March	1st to 10th	Day	56% 4 12% 13% 12% 2	3119
	11th to 20th	Day	36% 8% 16% 24% 13% 3	3306
	21st to end	Day	48% 4 6% 18% 17% 6%	4070
April	1st to 10th	Day	48% 5% 9% 19% 15% 3	2280
	11th to 20th	Day	42% 7% 11% 20% 17% 3	2254
	21st to end	Day	49% 5% 9% 17% 17% 3	2465
May	1st to 10th	Day	55% 8% 12% 14% 10% 1	4120
	11th to 20th	Day	51% 6% 14% 17% 10% 1	4226
	21st to end	Day	35% 7% 13% 24% 18% 2	4837
June	1st to 10th	Day	44% 8% 14% 23% 11% 1	2660
	11th to 20th	Day	41% 9% 13% 20% 14% 2	2660
	21st to end	Day	46% 8% 12% 21% 12% 1	2660
July	1st to 10th	Day	42% 9% 12% 21% 15% 1	4370
	11th to 20th	Day	37% 8% 16% 26% 12% 1	4365
	21st to end	Day	46% 6% 13% 20% 13% 2	4661
August	1st to 10th	Day	44% 9% 16% 21% 9% 1	4192
	11th to 20th	Day	42% 8% 15% 25% 9% 1	3989
	21st to end	Day	31% 8% 13% 31% 16% 1	4180
September	1st to 10th	Day	37% 7% 11% 24% 19% 2	2280
	11th to 20th	Day	36% 4 9% 26% 22% 3	2104
	21st to end	Day	41% 4 9% 22% 21% 2	2090
October	1st to 10th	Day	40% 7% 10% 21% 19% 3	3480
	11th to 20th	Day	30% 4 9% 28% 25% 4	3035
	21st to end	Day	33% 5% 11% 30% 18% 3	3081
November	1st to 10th	Day	39% 4 13% 25% 17% 2	1708
	11th to 20th	Day	39% 5% 10% 22% 20% 2	1710
	21st to end	Day	42% 6% 15% 23% 12% 2	1706
December	1st to 10th	Day	46% 7% 14% 17% 16% 1	1520
	11th to 20th	Day	43% 4 14% 18% 18% 3	1906
	21st to end	Day	51% 6% 12% 20% 11% 1	2772
January	1st to 10th	Night	39% 4 13% 29% 12% 3	4429
	11th to 20th	Night	46% 5% 12% 22% 12% 3	4440
	21st to end	Night	56% 5% 9% 17% 11% 2	4884
February	1st to 10th	Night	45% 6% 15% 20% 13% 2	2417
	11th to 20th	Night	43% 6% 11% 20% 17% 3	2220
	21st to end	Night	45% 5% 9% 24% 14% 4	1884
March	1st to 10th	Night	53% 5% 10% 20% 10% 2	3734
	11th to 20th	Night	41% 8% 15% 19% 15% 2	3653
	21st to end	Night	49% 5% 7% 14% 20% 7%	3544
April	1st to 10th	Night	47% 6% 10% 19% 15% 3	1900
	11th to 20th	Night	44% 6% 10% 20% 19% 2	1875
	21st to end	Night	45% 6% 10% 20% 15% 5%	1715
May	1st to 10th	Night	55% 8% 12% 16% 8% 2	2840
	11th to 20th	Night	53% 9% 14% 14% 9% 2	2701
	21st to end	Night	40% 7% 15% 22% 16% 1	2739
June	1st to 10th	Night	46% 7% 12% 22% 12% 1	1520
	11th to 20th	Night	45% 7% 13% 20% 13% 1	1520
	21st to end	Night	38% 10% 14% 23% 14% 1	1520
July	1st to 10th	Night	41% 9% 14% 21% 15% 1	2480
	11th to 20th	Night	39% 8% 16% 22% 14%	2472
	21st to end	Night	44% 7% 12% 20% 14% 1	2651
August	1st to 10th	Night	48% 9% 12% 19% 10% 1	2682
	11th to 20th	Night	43% 9% 15% 24% 10%	2900
	21st to end	Night	25% 7% 15% 32% 20% 1	3476
September	1st to 10th	Night	36% 6% 13% 25% 19% 1	1900
	11th to 20th	Night	33% 6% 10% 24% 26% 2	2076
	21st to end	Night	40% 6% 8% 25% 18% 3	2090
October	1st to 10th	Night	37% 6% 16% 23% 16% 2	3480
	11th to 20th	Night	26% 4 11% 26% 28% 4	3881
	21st to end	Night	34% 4 12% 32% 16% 2	4467
November	1st to 10th	Night	38% 6% 11% 21% 20% 4	2470
	11th to 20th	Night	41% 4 12% 21% 19% 3	2470
	21st to end	Night	40% 6% 14% 26% 14% 1	2470
December	1st to 10th	Night	46% 5% 13% 23% 13% 1	2660
	11th to 20th	Night	42% 6% 15% 18% 17% 2	3288
	21st to end	Night	49% 6% 11% 23% 11% 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	28% 25% 28% 16% 3	180
	11th to 20th	Day	33% 24% 31% 9% 3	180
	21st to end	Day	26% 24% 34% 12% 4	198
February	1st to 10th	Day	32% 24% 31% 12% 1	347
	11th to 20th	Day	28% 30% 31% 10% 1	456
	21st to end	Day	33% 18% 34% 11% 3 1	382
March	1st to 10th	Day	30% 21% 35% 11% 3	460
	11th to 20th	Day	29% 26% 29% 12% 3 1	460
	21st to end	Day	30% 20% 33% 10% 5% 1	506
April	1st to 10th	Day	32% 22% 29% 12% 5% 1	460
	11th to 20th	Day	29% 22% 32% 10% 6%	452
	21st to end	Day	29% 19% 32% 15% 3 2	460
May	1st to 10th	Day	30% 22% 28% 15% 4 1	463
	11th to 20th	Day	22% 16% 40% 16% 4 1	487
	21st to end	Day	17% 14% 36% 22% 9% 1	529
June	1st to 10th	Day	18% 14% 37% 20% 8% 2	490
	11th to 20th	Day	17% 14% 36% 23% 8% 1	490
	21st to end	Day	19% 14% 37% 20% 7% 3	490
July	1st to 10th	Day	17% 10% 28% 29% 13% 3	485
	11th to 20th	Day	14% 7% 33% 31% 12% 3	484
	21st to end	Day	13% 9% 37% 30% 10% 2	532
August	1st to 10th	Day	11% 10% 33% 30% 14% 2	486
	11th to 20th	Day	18% 8% 30% 28% 15% 3	479
	21st to end	Day	11% 10% 33% 28% 14% 5%	539
September	1st to 10th	Day	17% 12% 29% 23% 13% 6%	490
	11th to 20th	Day	18% 10% 28% 21% 15% 9%	490
	21st to end	Day	19% 13% 31% 23% 9% 6%	490
October	1st to 10th	Day	27% 14% 23% 21% 12% 3	490
	11th to 20th	Day	19% 18% 29% 23% 8% 2	444
	21st to end	Day	28% 14% 32% 18% 7% 1	429
November	1st to 10th	Day	22% 18% 30% 19% 10% 1	378
	11th to 20th	Day	30% 21% 26% 18% 4 1	370
	21st to end	Day	29% 19% 31% 15% 6%	366
December	1st to 10th	Day	23% 30% 28% 14% 4	180
	11th to 20th	Day	36% 24% 31% 6% 2	180
	21st to end	Day	31% 22% 34% 9% 4 1	198
January	1st to 10th	Night	23% 19% 40% 16% 1	760
	11th to 20th	Night	27% 20% 35% 16% 2	760
	21st to end	Night	21% 21% 38% 18% 3	836
February	1st to 10th	Night	23% 20% 38% 17% 1	760
	11th to 20th	Night	22% 23% 40% 14% 1	743
	21st to end	Night	27% 22% 33% 15% 2	628
March	1st to 10th	Night	26% 20% 35% 17% 2	760
	11th to 20th	Night	22% 23% 36% 16% 3	760
	21st to end	Night	25% 20% 33% 18% 4	836
April	1st to 10th	Night	25% 20% 33% 19% 3	760
	11th to 20th	Night	23% 21% 33% 18% 5%	751
	21st to end	Night	25% 21% 32% 20% 3	575
May	1st to 10th	Night	29% 15% 33% 21% 2	570
	11th to 20th	Night	20% 18% 38% 21% 4	501
	21st to end	Night	20% 9% 37% 29% 6%	411
June	1st to 10th	Night	20% 7% 37% 27% 7%	380
	11th to 20th	Night	20% 10% 34% 31% 5% 1	380
	21st to end	Night	15% 3 42% 34% 5%	380
July	1st to 10th	Night	15% 5% 32% 38% 10% 1	370
	11th to 20th	Night	12% 5% 31% 41% 11% 1	368
	21st to end	Night	13% 4 32% 41% 9%	416
August	1st to 10th	Night	12% 4 32% 40% 11%	486
	11th to 20th	Night	14% 5% 31% 36% 14% 1	614
	21st to end	Night	16% 4 25% 38% 16% 1	836
September	1st to 10th	Night	16% 6% 32% 32% 13% 1	760
	11th to 20th	Night	16% 8% 27% 28% 18% 2	760
	21st to end	Night	19% 10% 29% 28% 12% 2	760
October	1st to 10th	Night	24% 12% 27% 25% 11% 2	760
	11th to 20th	Night	19% 14% 32% 23% 11% 1	760
	21st to end	Night	27% 15% 32% 20% 6%	836
November	1st to 10th	Night	19% 14% 34% 24% 8% 1	760
	11th to 20th	Night	24% 19% 32% 18% 6% 1	760
	21st to end	Night	23% 20% 36% 17% 4 1	760
December	1st to 10th	Night	26% 20% 34% 16% 4	760
	11th to 20th	Night	25% 20% 34% 18% 2	760
	21st to end	Night	27% 18% 36% 16% 2	836

Page generated at 2024-11-03 02:11:18. Version ac07

Copyright © 2024 Attilla Danko.