Northampton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northampton clear sky chart from 2005-11-06 to 2024-03-28.

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% 6% 3 5% 5% 3 5% 5% 5% 7% 39%	78609
	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 40%	81381
Transparency	Day	43% 8% 13% 21% 13% 2	78314
	Night	43% 7% 13% 22% 13% 2	81210
Seeing	Day	22% 17% 30% 20% 9% 3	14080
	Night	21% 14% 31% 26% 7% 1	23236

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	14% 6% 3 6% 5% 3 4 5% 6% 6% 42%	2517
	11th to 20th	Day	16% 8% 5% 8% 7% 3 4 5% 5% 5% 34%	2520
	21st to end	Day	20% 10% 4 7% 6% 3 5% 4 4 6% 31%	2776
February	1st to 10th	Day	17% 7% 3 6% 5% 4 6% 7% 6% 7% 34%	1763
	11th to 20th	Day	13% 8% 4 7% 5% 3 4 4 5% 7% 40%	1848
	21st to end	Day	20% 8% 3 6% 5% 4 5% 5% 4 6% 35%	1570
March	1st to 10th	Day	17% 7% 3 7% 5% 3 4 4 5% 7% 39%	1897
	11th to 20th	Day	16% 7% 3 5% 6% 3 5% 6% 6% 6% 38%	1946
	21st to end	Day	19% 7% 3 6% 5% 3 4 4 5% 5% 40%	2460
April	1st to 10th	Day	18% 6% 3 6% 5% 3 4 4 5% 8% 38%	2160
	11th to 20th	Day	17% 6% 2 5% 5% 3 5% 5% 5% 7% 40%	2134
	21st to end	Day	20% 7% 3 5% 5% 3 5% 4 5% 6% 37%	2288
May	1st to 10th	Day	24% 7% 3 6% 5% 3 5% 5% 5% 6% 33%	2340
	11th to 20th	Day	18% 6% 3 4 5% 3 4 4 5% 7% 41%	2424
	21st to end	Day	14% 6% 2 6% 5% 3 5% 5% 5% 8% 41%	2725
June	1st to 10th	Day	16% 6% 3 5% 6% 3 5% 5% 6% 9% 35%	2520
	11th to 20th	Day	17% 5% 3 5% 5% 3 5% 5% 5% 10% 37%	2520
	21st to end	Day	16% 6% 2 6% 5% 3 6% 5% 6% 9% 36%	2520
July	1st to 10th	Day	13% 4 2 6% 6% 4 6% 4 6% 9% 40%	2520
	11th to 20th	Day	12% 5% 2 4 5% 4 5% 6% 7% 9% 40%	2520
	21st to end	Day	13% 5% 2 6% 5% 4 5% 6% 7% 9% 39%	2744
August	1st to 10th	Day	10% 5% 2 5% 7% 5% 6% 5% 7% 10% 40%	2431
	11th to 20th	Day	13% 5% 2 4 6% 4 6% 6% 6% 8% 40%	2184
	21st to end	Day	12% 5% 2 5% 4 3 5% 5% 6% 9% 44%	2376
September	1st to 10th	Day	14% 5% 2 5% 6% 3 5% 5% 5% 6% 44%	2160
	11th to 20th	Day	15% 6% 2 4 4 2 3 3 4 7% 50%	2030
	21st to end	Day	18% 5% 2 4 4 3 4 5% 5% 8% 43%	1980
October	1st to 10th	Day	23% 6% 2 5% 4 3 4 4 5% 5% 38%	1958
	11th to 20th	Day	14% 6% 2 4 5% 3 5% 4 5% 8% 44%	1761
	21st to end	Day	22% 7% 2 5% 5% 3 5% 4 4 6% 37%	1782
November	1st to 10th	Day	13% 7% 2 5% 4 3 4 4 4 6% 48%	1671
	11th to 20th	Day	19% 6% 2 4 3 3 3 4 5% 7% 44%	1710
	21st to end	Day	19% 6% 2 5% 5% 3 4 4 5% 6% 42%	1656
December	1st to 10th	Day	20% 7% 4 5% 5% 3 5% 5% 5% 6% 35%	1520
	11th to 20th	Day	23% 6% 3 4 4 2 3 3 3 7% 42%	1906
	21st to end	Day	21% 11% 4 6% 5% 3 4 4 3 6% 32%	2772
January	1st to 10th	Night	17% 8% 2 4 4 2 4 4 5% 6% 44%	4429
	11th to 20th	Night	15% 8% 4 8% 7% 3 4 4 5% 6% 36%	4440
	21st to end	Night	21% 13% 4 7% 5% 3 4 4 5% 5% 30%	4876
February	1st to 10th	Night	15% 10% 4 5% 4 3 5% 5% 5% 6% 38%	2415
	11th to 20th	Night	13% 7% 4 7% 5% 4 5% 5% 5% 6% 40%	2218
	21st to end	Night	18% 8% 3 6% 5% 2 4 5% 5% 6% 38%	1884
March	1st to 10th	Night	16% 7% 3 5% 5% 2 4 4 6% 7% 40%	2270
	11th to 20th	Night	16% 7% 2 5% 5% 3 5% 5% 5% 6% 40%	2231
	21st to end	Night	16% 7% 3 6% 4 2 4 4 6% 6% 42%	2051
April	1st to 10th	Night	19% 8% 2 5% 5% 3 4 4 5% 6% 38%	1800
	11th to 20th	Night	19% 6% 3 5% 5% 4 5% 4 4 6% 40%	1775
	21st to end	Night	23% 6% 3 6% 4 2 3 3 5% 6% 39%	1670
May	1st to 10th	Night	23% 8% 3 6% 5% 3 5% 4 5% 6% 33%	1620
	11th to 20th	Night	19% 5% 3 5% 4 3 5% 6% 6% 7% 38%	1483
	21st to end	Night	16% 5% 3 5% 5% 3 4 3 6% 8% 41%	1550
June	1st to 10th	Night	17% 6% 3 5% 6% 3 4 4 4 7% 40%	1440
	11th to 20th	Night	19% 5% 2 5% 5% 3 5% 5% 6% 7% 39%	1440
	21st to end	Night	15% 5% 2 5% 4 3 5% 5% 5% 9% 43%	1440
July	1st to 10th	Night	14% 5% 2 4 4 3 6% 5% 6% 8% 44%	1440
	11th to 20th	Night	15% 5% 2 5% 5% 3 5% 6% 7% 9% 39%	1440
	21st to end	Night	10% 4 3 5% 4 3 5% 5% 7% 10% 45%	1574
August	1st to 10th	Night	10% 6% 2 5% 5% 3 5% 5% 5% 8% 46%	1490
	11th to 20th	Night	12% 4 2 5% 6% 4 5% 5% 7% 8% 40%	1712
	21st to end	Night	15% 5% 2 4 4 2 4 5% 5% 8% 47%	1980
September	1st to 10th	Night	15% 5% 2 5% 5% 2 5% 4 5% 6% 46%	1800
	11th to 20th	Night	14% 6% 3 3 3 2 3 3 3 6% 52%	1930
	21st to end	Night	17% 6% 2 5% 5% 2 4 4 4 6% 46%	1980
October	1st to 10th	Night	23% 6% 2 5% 4 3 4 3 4 7% 41%	2000
	11th to 20th	Night	16% 5% 2 5% 4 2 4 5% 6% 6% 45%	2198
	21st to end	Night	23% 7% 2 4 5% 3 3 4 4 5% 38%	2574
November	1st to 10th	Night	15% 6% 2 4 4 2 4 4 5% 6% 49%	2407
	11th to 20th	Night	20% 4 3 4 4 2 4 3 4 5% 45%	2470
	21st to end	Night	16% 7% 2 4 5% 3 4 4 5% 6% 44%	2522
December	1st to 10th	Night	20% 7% 3 5% 6% 3 4 4 5% 6% 37%	2660
	11th to 20th	Night	21% 6% 3 4 4 2 4 4 6% 6% 39%	3288
	21st to end	Night	22% 11% 4 6% 5% 3 4 4 5% 6% 32%	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	38% 7% 14% 32% 8% 1	2518
	11th to 20th	Day	49% 9% 12% 21% 8% 1	2520
	21st to end	Day	55% 7% 10% 19% 8% 1	2776
February	1st to 10th	Day	47% 9% 13% 19% 11% 1	1763
	11th to 20th	Day	45% 7% 10% 22% 14% 3	1857
	21st to end	Day	49% 6% 11% 19% 13% 2	1570
March	1st to 10th	Day	44% 6% 14% 20% 12% 3	1900
	11th to 20th	Day	44% 7% 13% 20% 13% 3	1946
	21st to end	Day	47% 5% 8% 17% 17% 5%	2460
April	1st to 10th	Day	46% 6% 10% 22% 14% 3	2160
	11th to 20th	Day	41% 8% 12% 20% 17% 3	2134
	21st to end	Day	47% 7% 9% 19% 15% 3	2288
May	1st to 10th	Day	52% 7% 8% 18% 13% 1	2340
	11th to 20th	Day	42% 7% 11% 21% 17% 2	2428
	21st to end	Day	40% 9% 15% 21% 13% 2	2725
June	1st to 10th	Day	44% 9% 14% 20% 11% 1	2520
	11th to 20th	Day	42% 9% 15% 20% 13% 1	2520
	21st to end	Day	43% 10% 14% 20% 12% 1	2520
July	1st to 10th	Day	40% 8% 12% 22% 15% 2	2450
	11th to 20th	Day	37% 10% 17% 24% 12% 1	2445
	21st to end	Day	39% 10% 15% 20% 15% 2	2591
August	1st to 10th	Day	38% 10% 16% 23% 12% 1	2417
	11th to 20th	Day	39% 10% 15% 24% 11% 1	2184
	21st to end	Day	35% 10% 12% 25% 16% 2	2376
September	1st to 10th	Day	38% 9% 13% 24% 15% 1	2160
	11th to 20th	Day	36% 6% 10% 24% 22% 2	2030
	21st to end	Day	38% 7% 12% 22% 18% 3	1980
October	1st to 10th	Day	47% 7% 10% 19% 13% 4	1958
	11th to 20th	Day	37% 8% 14% 26% 13% 2	1761
	21st to end	Day	48% 7% 12% 18% 12% 3	1782
November	1st to 10th	Day	38% 7% 14% 25% 14% 2	1671
	11th to 20th	Day	39% 7% 13% 22% 17% 2	1710
	21st to end	Day	44% 5% 15% 24% 11% 2	1656
December	1st to 10th	Day	49% 9% 14% 15% 12% 2	1520
	11th to 20th	Day	43% 6% 16% 19% 15% 1	1906
	21st to end	Day	52% 7% 13% 18% 10%	2772
January	1st to 10th	Night	40% 6% 14% 26% 11% 3	4429
	11th to 20th	Night	46% 7% 14% 20% 11% 2	4440
	21st to end	Night	55% 7% 10% 18% 9% 1	4876
February	1st to 10th	Night	45% 7% 14% 21% 11% 2	2415
	11th to 20th	Night	43% 7% 12% 20% 15% 3	2220
	21st to end	Night	44% 8% 11% 22% 11% 4	1884
March	1st to 10th	Night	43% 7% 12% 22% 13% 3	2280
	11th to 20th	Night	42% 8% 14% 20% 13% 3	2232
	21st to end	Night	42% 7% 10% 17% 19% 5%	2051
April	1st to 10th	Night	47% 5% 11% 19% 15% 3	1800
	11th to 20th	Night	46% 6% 10% 19% 18% 1	1775
	21st to end	Night	45% 7% 9% 20% 13% 5%	1670
May	1st to 10th	Night	51% 8% 11% 16% 12% 3	1620
	11th to 20th	Night	43% 8% 12% 20% 15% 3	1484
	21st to end	Night	41% 9% 16% 21% 12% 1	1551
June	1st to 10th	Night	44% 7% 12% 24% 12% 1	1440
	11th to 20th	Night	43% 9% 14% 22% 11% 1	1440
	21st to end	Night	37% 10% 15% 24% 13% 1	1440
July	1st to 10th	Night	35% 10% 16% 23% 14% 1	1400
	11th to 20th	Night	39% 10% 16% 25% 10%	1392
	21st to end	Night	33% 9% 18% 24% 15% 2	1486
August	1st to 10th	Night	34% 11% 15% 25% 14% 1	1480
	11th to 20th	Night	39% 10% 16% 22% 12%	1712
	21st to end	Night	34% 8% 11% 26% 18% 1	1980
September	1st to 10th	Night	39% 8% 12% 25% 17% 1	1800
	11th to 20th	Night	35% 5% 11% 24% 24% 2	1930
	21st to end	Night	39% 6% 9% 24% 19% 3	1980
October	1st to 10th	Night	44% 6% 14% 21% 12% 3	2000
	11th to 20th	Night	38% 7% 14% 27% 13% 1	2198
	21st to end	Night	48% 6% 13% 20% 12% 1	2574
November	1st to 10th	Night	37% 7% 13% 22% 19% 3	2407
	11th to 20th	Night	42% 6% 13% 21% 16% 3	2470
	21st to end	Night	40% 6% 17% 26% 11% 1	2522
December	1st to 10th	Night	47% 7% 15% 20% 12%	2660
	11th to 20th	Night	43% 8% 16% 17% 14% 2	3288
	21st to end	Night	51% 7% 12% 21% 8% 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	23% 27% 27% 18% 4	180
	11th to 20th	Day	27% 29% 31% 8% 4	180
	21st to end	Day	19% 28% 36% 13% 4 1	200
February	1st to 10th	Day	28% 29% 32% 10% 1	323
	11th to 20th	Day	28% 25% 33% 13% 2	456
	21st to end	Day	30% 19% 33% 16% 2	382
March	1st to 10th	Day	26% 23% 35% 13% 3	460
	11th to 20th	Day	29% 24% 30% 12% 4	460
	21st to end	Day	27% 25% 31% 10% 6% 2	490
April	1st to 10th	Day	30% 21% 29% 12% 7% 1	420
	11th to 20th	Day	27% 22% 28% 15% 7% 1	412
	21st to end	Day	30% 20% 29% 15% 5% 1	420
May	1st to 10th	Day	34% 20% 26% 12% 7% 1	423
	11th to 20th	Day	21% 17% 38% 17% 5% 2	447
	21st to end	Day	19% 13% 31% 22% 13% 3	485
June	1st to 10th	Day	17% 16% 33% 22% 10% 3	450
	11th to 20th	Day	18% 16% 33% 23% 8% 2	450
	21st to end	Day	14% 17% 33% 22% 11% 4	450
July	1st to 10th	Day	15% 8% 33% 27% 15% 3	445
	11th to 20th	Day	13% 7% 30% 30% 16% 3	444
	21st to end	Day	13% 8% 35% 27% 15% 2	488
August	1st to 10th	Day	10% 9% 27% 34% 15% 5%	446
	11th to 20th	Day	13% 8% 32% 25% 16% 6%	439
	21st to end	Day	12% 12% 27% 27% 16% 6%	495
September	1st to 10th	Day	20% 8% 23% 26% 15% 8%	450
	11th to 20th	Day	18% 12% 26% 21% 14% 10%	450
	21st to end	Day	20% 11% 29% 22% 11% 6%	450
October	1st to 10th	Day	28% 12% 22% 20% 12% 5%	450
	11th to 20th	Day	17% 19% 27% 25% 11% 2	430
	21st to end	Day	30% 14% 26% 22% 8% 1	396
November	1st to 10th	Day	21% 15% 28% 24% 10% 2	365
	11th to 20th	Day	28% 19% 29% 17% 5% 1	370
	21st to end	Day	26% 18% 29% 21% 6% 1	316
December	1st to 10th	Day	23% 25% 33% 14% 4	180
	11th to 20th	Day	34% 20% 33% 10% 2	180
	21st to end	Day	25% 25% 31% 16% 3 2	198
January	1st to 10th	Night	21% 16% 39% 22% 3	760
	11th to 20th	Night	25% 18% 33% 22% 2	760
	21st to end	Night	18% 17% 39% 23% 3	836
February	1st to 10th	Night	22% 18% 37% 22% 1	760
	11th to 20th	Night	20% 23% 41% 15% 1	743
	21st to end	Night	25% 20% 32% 20% 3	628
March	1st to 10th	Night	23% 18% 37% 19% 2	760
	11th to 20th	Night	22% 23% 34% 19% 3	760
	21st to end	Night	23% 18% 35% 19% 5%	821
April	1st to 10th	Night	23% 20% 33% 20% 4	720
	11th to 20th	Night	23% 18% 32% 22% 6%	711
	21st to end	Night	26% 18% 31% 22% 3	590
May	1st to 10th	Night	27% 14% 32% 22% 4	540
	11th to 20th	Night	20% 14% 37% 23% 6%	422
	21st to end	Night	18% 10% 28% 35% 9% 1	389
June	1st to 10th	Night	20% 6% 29% 35% 9%	360
	11th to 20th	Night	19% 8% 29% 35% 9%	360
	21st to end	Night	16% 4 29% 40% 11% 1	360
July	1st to 10th	Night	15% 3 25% 41% 15% 1	350
	11th to 20th	Night	15% 3 23% 42% 16% 1	348
	21st to end	Night	10% 4 25% 47% 14% 1	394
August	1st to 10th	Night	11% 3 27% 46% 13% 1	416
	11th to 20th	Night	13% 5% 24% 40% 17% 2	648
	21st to end	Night	15% 6% 20% 38% 19% 1	792
September	1st to 10th	Night	17% 5% 27% 35% 14% 2	720
	11th to 20th	Night	15% 7% 25% 30% 19% 3	720
	21st to end	Night	18% 8% 26% 33% 14% 2	720
October	1st to 10th	Night	26% 9% 23% 28% 12% 2	720
	11th to 20th	Night	19% 11% 32% 30% 8%	720
	21st to end	Night	27% 13% 31% 24% 5%	792
November	1st to 10th	Night	17% 14% 31% 28% 8% 1	740
	11th to 20th	Night	23% 15% 32% 22% 7% 1	760
	21st to end	Night	21% 16% 30% 27% 5% 1	760
December	1st to 10th	Night	24% 16% 37% 18% 5%	760
	11th to 20th	Night	25% 17% 32% 24% 3	760
	21st to end	Night	25% 17% 36% 20% 2	836

Page generated at 2024-03-24 23:37:00. Version ac07

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