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 2024-11-04.

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% 7% 2 6% 5% 4 4 4 6% 7% 38%	101268
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	97751
Transparency	Day	43% 7% 13% 21% 14% 2	104793
	Night	43% 7% 13% 22% 14% 2	102315
Seeing	Day	22% 17% 30% 20% 9% 3	14947
	Night	21% 14% 31% 27% 7% 1	23924

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 7% 4 4 4 4 6% 6% 42%	2517
	11th to 20th	Day	16% 9% 4 10% 5% 4 4 4 5% 5% 34%	2520
	21st to end	Day	20% 11% 4 9% 5% 4 4 3 4 5% 31%	2776
February	1st to 10th	Day	17% 8% 3 6% 5% 6% 5% 5% 6% 6% 34%	1763
	11th to 20th	Day	13% 8% 3 8% 5% 4 4 3 6% 7% 40%	1848
	21st to end	Day	19% 9% 3 7% 4 5% 4 4 4 6% 35%	1570
March	1st to 10th	Day	24% 12% 3 8% 5% 3 3 3 3 5% 32%	3116
	11th to 20th	Day	12% 7% 3 7% 6% 4 5% 5% 6% 8% 38%	3258
	21st to end	Day	21% 7% 2 7% 4 3 4 3 5% 5% 38%	4166
April	1st to 10th	Day	19% 8% 2 7% 5% 4 4 3 5% 7% 37%	2280
	11th to 20th	Day	17% 7% 2 5% 4 4 5% 4 6% 6% 39%	2254
	21st to end	Day	19% 7% 3 6% 5% 4 5% 3 5% 6% 38%	2416
May	1st to 10th	Day	25% 8% 3 7% 5% 4 5% 4 6% 6% 29%	4106
	11th to 20th	Day	21% 8% 3 7% 5% 4 3 3 5% 7% 35%	4302
	21st to end	Day	13% 5% 1 5% 4 4 5% 4 7% 9% 43%	4837
June	1st to 10th	Day	16% 7% 2 6% 5% 4 5% 4 7% 9% 35%	2660
	11th to 20th	Day	16% 6% 2 5% 5% 4 5% 4 6% 10% 37%	2660
	21st to end	Day	15% 7% 2 7% 4 4 5% 5% 6% 8% 35%	2660
July	1st to 10th	Day	11% 5% 2 7% 6% 6% 5% 5% 7% 9% 37%	4440
	11th to 20th	Day	12% 5% 2 5% 5% 5% 5% 5% 8% 10% 38%	4440
	21st to end	Day	17% 7% 2 7% 5% 5% 4 4 6% 7% 36%	4814
August	1st to 10th	Day	16% 6% 3 7% 5% 6% 5% 4 6% 9% 33%	4279
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 4 6% 8% 39%	3827
	21st to end	Day	9% 4 2 6% 4 5% 6% 5% 7% 10% 43%	4180
September	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 4 5% 6% 45%	2280
	11th to 20th	Day	15% 6% 2 5% 4 3 3 2 4 7% 50%	2142
	21st to end	Day	18% 5% 2 5% 4 5% 4 4 5% 7% 41%	2090
October	1st to 10th	Day	22% 6% 2 6% 3 4 4 3 5% 5% 39%	2066
	11th to 20th	Day	14% 6% 2 4 4 4 5% 3 5% 8% 45%	1858
	21st to end	Day	21% 7% 3 6% 4 4 4 3 5% 6% 38%	1881
November	1st to 10th	Day	13% 7% 2 6% 3 4 3 3 4 6% 48%	1698
	11th to 20th	Day	19% 7% 2 4 2 3 3 4 5% 7% 44%	1710
	21st to end	Day	18% 6% 2 6% 4 4 4 3 6% 6% 41%	1656
December	1st to 10th	Day	20% 9% 3 6% 4 4 5% 4 5% 6% 35%	1520
	11th to 20th	Day	23% 6% 3 5% 3 3 3 3 4 6% 42%	1906
	21st to end	Day	21% 11% 3 7% 4 4 4 3 3 6% 32%	2772
January	1st to 10th	Night	17% 8% 2 5% 3 3 4 3 5% 6% 44%	4429
	11th to 20th	Night	15% 9% 4 10% 5% 4 4 3 5% 6% 36%	4440
	21st to end	Night	21% 14% 3 7% 4 4 4 3 5% 5% 29%	4876
February	1st to 10th	Night	15% 10% 3 5% 4 4 5% 4 6% 5% 38%	2415
	11th to 20th	Night	13% 7% 3 7% 4 5% 4 4 5% 6% 40%	2218
	21st to end	Night	18% 9% 3 6% 5% 4 3 4 5% 6% 38%	1884
March	1st to 10th	Night	27% 8% 3 5% 4 4 4 3 5% 5% 31%	3724
	11th to 20th	Night	12% 9% 2 6% 5% 4 5% 4 5% 7% 40%	3699
	21st to end	Night	21% 9% 2 6% 3 3 4 3 6% 5% 37%	3466
April	1st to 10th	Night	19% 8% 2 7% 4 4 4 3 5% 6% 37%	1900
	11th to 20th	Night	20% 7% 3 5% 4 5% 4 3 4 6% 39%	1875
	21st to end	Night	22% 7% 2 6% 3 3 3 2 5% 6% 40%	1762
May	1st to 10th	Night	25% 9% 3 6% 4 4 4 4 5% 6% 29%	2834
	11th to 20th	Night	19% 9% 4 8% 5% 6% 5% 4 5% 7% 28%	2605
	21st to end	Night	16% 5% 3 5% 3 4 3 3 6% 9% 42%	2738
June	1st to 10th	Night	16% 7% 2 6% 5% 5% 3 4 4 7% 40%	1520
	11th to 20th	Night	18% 6% 2 6% 4 5% 4 3 6% 7% 40%	1520
	21st to end	Night	16% 6% 2 6% 3 4 5% 4 5% 9% 41%	1520
July	1st to 10th	Night	12% 5% 2 6% 5% 5% 5% 5% 7% 9% 39%	2520
	11th to 20th	Night	14% 6% 2 7% 4 4 5% 4 6% 8% 40%	2520
	21st to end	Night	16% 7% 3 7% 3 5% 4 4 6% 7% 39%	2739
August	1st to 10th	Night	22% 6% 2 7% 5% 5% 5% 4 5% 6% 33%	2620
	11th to 20th	Night	14% 7% 3 6% 5% 5% 5% 4 6% 7% 39%	2996
	21st to end	Night	10% 4 2 4 3 4 4 4 5% 8% 53%	3476
September	1st to 10th	Night	15% 5% 2 5% 4 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	13% 6% 3 4 3 3 3 3 4 7% 52%	2038
	21st to end	Night	17% 7% 1 6% 4 4 4 3 4 6% 44%	2090
October	1st to 10th	Night	21% 6% 2 6% 3 4 3 3 4 7% 41%	2112
	11th to 20th	Night	16% 6% 2 6% 3 3 4 4 6% 6% 47%	2321
	21st to end	Night	23% 7% 2 5% 5% 4 3 3 5% 5% 39%	2717
November	1st to 10th	Night	14% 6% 2 5% 3 4 3 3 5% 6% 49%	2453
	11th to 20th	Night	20% 5% 2 5% 3 4 3 3 4 5% 45%	2470
	21st to end	Night	16% 8% 2 4 5% 3 4 3 5% 6% 44%	2522
December	1st to 10th	Night	20% 8% 2 6% 5% 4 4 3 5% 6% 37%	2660
	11th to 20th	Night	21% 7% 2 5% 4 3 4 4 6% 6% 39%	3288
	21st to end	Night	22% 11% 4 7% 4 3 4 3 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	55% 6% 12% 15% 11% 2	3119
	11th to 20th	Day	37% 12% 18% 22% 10% 2	3258
	21st to end	Day	47% 5% 7% 17% 19% 5%	4166
April	1st to 10th	Day	47% 6% 10% 21% 13% 3	2280
	11th to 20th	Day	42% 8% 12% 19% 17% 2	2254
	21st to end	Day	46% 8% 9% 19% 15% 3	2416
May	1st to 10th	Day	53% 10% 11% 14% 11% 1	4120
	11th to 20th	Day	48% 8% 15% 18% 10% 1	4306
	21st to end	Day	34% 9% 15% 24% 16% 2	4837
June	1st to 10th	Day	43% 9% 14% 21% 12% 1	2660
	11th to 20th	Day	41% 8% 15% 20% 13% 1	2660
	21st to end	Day	43% 9% 14% 20% 13% 1	2660
July	1st to 10th	Day	42% 7% 13% 21% 16% 1	4370
	11th to 20th	Day	39% 8% 17% 23% 12% 2	4365
	21st to end	Day	46% 7% 13% 19% 14% 1	4661
August	1st to 10th	Day	47% 7% 17% 20% 9% 1	4265
	11th to 20th	Day	41% 7% 14% 28% 9% 1	3866
	21st to end	Day	35% 8% 14% 28% 15% 1	4180
September	1st to 10th	Day	37% 8% 12% 25% 16% 1	2280
	11th to 20th	Day	35% 6% 9% 25% 22% 2	2142
	21st to end	Day	40% 7% 12% 22% 17% 3	2090
October	1st to 10th	Day	41% 5% 8% 22% 21% 3	3430
	11th to 20th	Day	32% 5% 8% 28% 25% 2	3061
	21st to end	Day	35% 5% 13% 28% 16% 4	3081
November	1st to 10th	Day	37% 7% 14% 26% 14% 2	1698
	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	52% 7% 12% 17% 10% 2	3734
	11th to 20th	Night	39% 10% 16% 22% 12% 2	3700
	21st to end	Night	45% 7% 8% 13% 21% 5%	3466
April	1st to 10th	Night	47% 6% 11% 19% 15% 2	1900
	11th to 20th	Night	46% 6% 9% 18% 18% 1	1875
	21st to end	Night	44% 7% 9% 20% 14% 5%	1762
May	1st to 10th	Night	52% 10% 13% 14% 10% 2	2840
	11th to 20th	Night	51% 12% 12% 15% 8% 2	2606
	21st to end	Night	37% 9% 16% 22% 14% 1	2739
June	1st to 10th	Night	43% 7% 12% 24% 13% 1	1520
	11th to 20th	Night	41% 9% 15% 23% 11% 1	1520
	21st to end	Night	39% 10% 15% 23% 13% 1	1520
July	1st to 10th	Night	39% 9% 17% 20% 15% 1	2480
	11th to 20th	Night	41% 7% 15% 24% 13%	2472
	21st to end	Night	44% 7% 13% 19% 16% 1	2651
August	1st to 10th	Night	51% 9% 12% 19% 9% 1	2610
	11th to 20th	Night	43% 7% 15% 24% 9%	3023
	21st to end	Night	29% 7% 15% 33% 16% 1	3476
September	1st to 10th	Night	38% 7% 11% 25% 18% 1	1900
	11th to 20th	Night	34% 5% 11% 24% 24% 2	2038
	21st to end	Night	41% 6% 9% 23% 18% 3	2090
October	1st to 10th	Night	39% 5% 14% 23% 17% 2	3528
	11th to 20th	Night	28% 4 11% 28% 28% 1	3857
	21st to end	Night	35% 4 13% 32% 15% 1	4467
November	1st to 10th	Night	36% 7% 12% 23% 19% 3	2453
	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	28% 25% 30% 10% 5% 2	506
April	1st to 10th	Day	30% 22% 29% 12% 7% 1	460
	11th to 20th	Day	29% 23% 28% 14% 6% 1	452
	21st to end	Day	28% 21% 29% 15% 5% 2	460
May	1st to 10th	Day	32% 20% 27% 13% 6% 1	463
	11th to 20th	Day	21% 17% 37% 17% 6% 1	487
	21st to end	Day	19% 13% 31% 23% 12% 2	529
June	1st to 10th	Day	16% 16% 33% 23% 10% 3	490
	11th to 20th	Day	17% 16% 32% 23% 9% 2	490
	21st to end	Day	15% 16% 35% 21% 10% 3	490
July	1st to 10th	Day	15% 8% 33% 26% 15% 2	485
	11th to 20th	Day	13% 7% 31% 30% 17% 3	484
	21st to end	Day	15% 8% 34% 26% 15% 2	532
August	1st to 10th	Day	11% 9% 26% 34% 15% 5%	486
	11th to 20th	Day	14% 8% 32% 24% 16% 6%	479
	21st to end	Day	11% 11% 27% 28% 16% 6%	539
September	1st to 10th	Day	19% 8% 24% 26% 15% 8%	490
	11th to 20th	Day	17% 11% 24% 22% 16% 11%	490
	21st to end	Day	20% 11% 29% 23% 11% 6%	490
October	1st to 10th	Day	26% 12% 22% 21% 13% 5%	490
	11th to 20th	Day	17% 18% 27% 25% 10% 3	467
	21st to end	Day	28% 14% 26% 23% 8% 1	429
November	1st to 10th	Day	21% 15% 28% 24% 9% 2	374
	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%	836
April	1st to 10th	Night	23% 20% 34% 20% 4	760
	11th to 20th	Night	23% 19% 31% 21% 6%	751
	21st to end	Night	25% 19% 31% 22% 4	622
May	1st to 10th	Night	26% 15% 32% 22% 4	570
	11th to 20th	Night	19% 14% 38% 24% 6%	445
	21st to end	Night	18% 9% 29% 35% 9%	411
June	1st to 10th	Night	19% 7% 31% 34% 9%	380
	11th to 20th	Night	18% 8% 30% 34% 9%	380
	21st to end	Night	18% 5% 29% 38% 10% 1	380
July	1st to 10th	Night	14% 3 26% 41% 15% 1	370
	11th to 20th	Night	15% 3 24% 41% 16% 1	368
	21st to end	Night	11% 4 25% 45% 14%	416
August	1st to 10th	Night	12% 3 26% 45% 13% 1	440
	11th to 20th	Night	13% 5% 24% 39% 18% 2	685
	21st to end	Night	14% 6% 20% 39% 19% 2	836
September	1st to 10th	Night	17% 5% 27% 35% 15% 2	760
	11th to 20th	Night	15% 7% 24% 31% 21% 3	760
	21st to end	Night	18% 8% 25% 33% 14% 2	760
October	1st to 10th	Night	25% 8% 24% 29% 13% 2	760
	11th to 20th	Night	18% 11% 32% 30% 9%	760
	21st to end	Night	26% 12% 31% 25% 6%	836
November	1st to 10th	Night	17% 15% 31% 28% 8% 1	755
	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 2024-11-01 22:47:47. Version ac07

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