East Hartford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Hartford clear sky chart from 2005-11-06 to 2024-11-12.

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% 4 4 4 4 5% 7% 38%	101304
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 39%	97881
Transparency	Day	44% 5% 11% 23% 15% 2	104854
	Night	44% 4 12% 23% 15% 2	102420
Seeing	Day	24% 16% 31% 20% 8% 2	15036
	Night	23% 13% 32% 25% 7% 1	24034

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	15% 7% 2 6% 4 4 4 3 5% 5% 45%	2517
	11th to 20th	Day	17% 7% 3 8% 5% 4 4 4 6% 5% 36%	2520
	21st to end	Day	23% 11% 3 7% 4 3 4 3 4 5% 33%	2806
February	1st to 10th	Day	18% 7% 3 6% 4 5% 5% 5% 6% 6% 36%	1783
	11th to 20th	Day	14% 7% 3 7% 4 5% 5% 3 5% 7% 40%	1848
	21st to end	Day	21% 9% 2 5% 4 4 4 4 5% 6% 37%	1570
March	1st to 10th	Day	25% 11% 3 7% 4 3 3 2 3 4 33%	3116
	11th to 20th	Day	12% 7% 2 7% 5% 6% 5% 4 6% 7% 40%	3244
	21st to end	Day	21% 6% 3 6% 4 4 4 3 5% 6% 37%	4166
April	1st to 10th	Day	19% 8% 3 7% 4 4 4 4 5% 7% 36%	2280
	11th to 20th	Day	19% 6% 2 6% 4 4 4 4 5% 6% 41%	2254
	21st to end	Day	21% 6% 3 5% 5% 4 4 3 5% 6% 39%	2405
May	1st to 10th	Day	27% 8% 3 7% 4 4 4 3 5% 8% 28%	4106
	11th to 20th	Day	23% 8% 3 7% 4 3 4 3 5% 7% 33%	4260
	21st to end	Day	14% 5% 2 5% 4 4 4 3 6% 8% 45%	4837
June	1st to 10th	Day	17% 6% 2 6% 4 5% 5% 4 6% 9% 36%	2660
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 4 6% 9% 37%	2660
	21st to end	Day	13% 7% 3 7% 5% 5% 4 4 6% 9% 37%	2660
July	1st to 10th	Day	11% 7% 2 7% 6% 6% 5% 5% 6% 9% 35%	4440
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 5% 6% 10% 38%	4440
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 6% 6% 34%	4814
August	1st to 10th	Day	17% 8% 3 8% 6% 5% 4 4 7% 9% 29%	4243
	11th to 20th	Day	10% 6% 3 8% 5% 4 5% 4 6% 8% 41%	3799
	21st to end	Day	8% 6% 2 7% 4 5% 5% 4 6% 9% 43%	4180
September	1st to 10th	Day	14% 6% 2 7% 4 4 4 3 6% 6% 45%	2280
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 4 6% 51%	2138
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 6% 42%	2090
October	1st to 10th	Day	21% 7% 3 5% 4 4 4 3 5% 5% 40%	2076
	11th to 20th	Day	14% 6% 2 5% 3 4 3 3 5% 7% 46%	1866
	21st to end	Day	20% 7% 2 6% 4 4 3 4 5% 6% 40%	1881
November	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 4 6% 48%	1761
	11th to 20th	Day	20% 6% 2 4 3 3 3 3 5% 6% 45%	1719
	21st to end	Day	17% 7% 2 6% 5% 4 4 3 4 6% 43%	1687
December	1st to 10th	Day	19% 7% 3 6% 5% 3 4 4 5% 6% 37%	1520
	11th to 20th	Day	23% 6% 2 4 3 2 4 3 4 5% 44%	1906
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 5% 5% 32%	2772
January	1st to 10th	Night	17% 6% 2 5% 4 4 3 3 5% 6% 45%	4429
	11th to 20th	Night	16% 9% 3 8% 4 3 3 3 4 4 41%	4440
	21st to end	Night	25% 12% 3 7% 4 3 3 3 4 4 31%	4848
February	1st to 10th	Night	17% 9% 3 6% 4 3 4 3 5% 5% 39%	2395
	11th to 20th	Night	15% 8% 2 6% 5% 5% 4 4 5% 6% 39%	2218
	21st to end	Night	20% 9% 2 6% 5% 4 3 3 4 5% 40%	1884
March	1st to 10th	Night	28% 10% 2 6% 4 3 3 3 5% 5% 32%	3724
	11th to 20th	Night	12% 9% 3 6% 4 4 5% 4 6% 6% 41%	3697
	21st to end	Night	23% 8% 2 6% 3 4 3 3 5% 5% 38%	3466
April	1st to 10th	Night	20% 7% 2 6% 5% 4 5% 3 6% 6% 36%	1900
	11th to 20th	Night	20% 7% 3 6% 5% 4 4 4 5% 5% 39%	1875
	21st to end	Night	23% 7% 3 6% 4 3 4 3 4 5% 40%	1773
May	1st to 10th	Night	25% 9% 3 7% 5% 4 3 3 5% 7% 29%	2834
	11th to 20th	Night	21% 10% 3 8% 5% 4 4 3 6% 6% 30%	2663
	21st to end	Night	17% 6% 3 5% 2 4 4 4 6% 8% 41%	2738
June	1st to 10th	Night	17% 7% 2 5% 4 3 4 4 6% 8% 39%	1520
	11th to 20th	Night	17% 6% 2 6% 4 4 4 4 6% 7% 39%	1520
	21st to end	Night	13% 5% 2 6% 5% 4 3 4 6% 9% 41%	1520
July	1st to 10th	Night	13% 6% 2 8% 5% 5% 4 5% 7% 10% 35%	2520
	11th to 20th	Night	15% 6% 2 6% 5% 4 5% 4 6% 9% 38%	2520
	21st to end	Night	16% 10% 3 8% 4 5% 5% 4 6% 7% 33%	2739
August	1st to 10th	Night	22% 6% 2 7% 5% 5% 5% 4 7% 7% 30%	2653
	11th to 20th	Night	12% 8% 3 8% 4 4 5% 4 6% 7% 38%	3025
	21st to end	Night	9% 4 1 5% 4 3 4 3 6% 9% 51%	3476
September	1st to 10th	Night	14% 6% 3 7% 5% 4 4 3 5% 6% 44%	1900
	11th to 20th	Night	13% 6% 1 5% 3 3 3 3 4 6% 52%	2042
	21st to end	Night	17% 6% 2 7% 4 3 4 3 5% 6% 43%	2090
October	1st to 10th	Night	20% 7% 2 5% 4 3 3 3 5% 6% 40%	2100
	11th to 20th	Night	16% 5% 1 6% 3 4 4 4 4 5% 47%	2313
	21st to end	Night	23% 6% 2 5% 4 3 3 4 5% 5% 39%	2717
November	1st to 10th	Night	14% 6% 2 5% 4 4 3 3 5% 6% 49%	2537
	11th to 20th	Night	20% 7% 2 6% 3 3 3 3 5% 5% 44%	2484
	21st to end	Night	17% 7% 2 6% 4 3 4 3 5% 7% 44%	2489
December	1st to 10th	Night	21% 8% 3 6% 4 4 3 3 5% 6% 39%	2660
	11th to 20th	Night	21% 7% 2 5% 4 4 4 3 4 5% 41%	3288
	21st to end	Night	23% 11% 2 6% 4 4 4 2 4 5% 35%	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	41% 4 9% 33% 11% 2	2518
	11th to 20th	Day	49% 4 10% 26% 10% 1	2520
	21st to end	Day	55% 3 9% 22% 10% 2	2806
February	1st to 10th	Day	48% 4 13% 21% 13% 2	1783
	11th to 20th	Day	44% 4 9% 24% 16% 3	1857
	21st to end	Day	49% 3 10% 22% 13% 3	1570
March	1st to 10th	Day	56% 3 11% 17% 11% 2	3119
	11th to 20th	Day	40% 7% 10% 29% 12% 2	3244
	21st to end	Day	47% 5% 5% 18% 20% 5%	4166
April	1st to 10th	Day	47% 5% 9% 22% 15% 3	2280
	11th to 20th	Day	44% 4 10% 21% 19% 3	2254
	21st to end	Day	47% 4 9% 21% 16% 4	2405
May	1st to 10th	Day	55% 4 14% 15% 11% 1	4120
	11th to 20th	Day	52% 3 14% 19% 10% 2	4264
	21st to end	Day	37% 6% 12% 26% 18% 2	4837
June	1st to 10th	Day	45% 5% 12% 25% 12% 1	2660
	11th to 20th	Day	44% 5% 14% 22% 13% 2	2660
	21st to end	Day	44% 6% 13% 22% 15% 1	2660
July	1st to 10th	Day	45% 7% 11% 20% 16% 1	4370
	11th to 20th	Day	40% 6% 16% 23% 13% 1	4365
	21st to end	Day	49% 6% 11% 18% 15% 2	4661
August	1st to 10th	Day	51% 6% 15% 20% 8%	4229
	11th to 20th	Day	39% 6% 14% 30% 10%	3837
	21st to end	Day	35% 7% 11% 29% 16% 2	4180
September	1st to 10th	Day	40% 4 11% 23% 20% 2	2280
	11th to 20th	Day	35% 4 10% 24% 24% 3	2138
	21st to end	Day	44% 4 8% 22% 20% 3	2090
October	1st to 10th	Day	39% 5% 9% 20% 23% 4	3453
	11th to 20th	Day	29% 3 8% 26% 30% 4	3082
	21st to end	Day	33% 4 13% 27% 21% 3	3081
November	1st to 10th	Day	39% 3 12% 23% 20% 2	1761
	11th to 20th	Day	41% 3 10% 24% 19% 3	1719
	21st to end	Day	43% 4 12% 26% 12% 3	1687
December	1st to 10th	Day	48% 3 13% 19% 16% 1	1520
	11th to 20th	Day	44% 3 14% 19% 18% 2	1906
	21st to end	Day	54% 3 11% 21% 10% 1	2772
January	1st to 10th	Night	41% 2 11% 32% 11% 3	4429
	11th to 20th	Night	47% 3 11% 24% 12% 3	4440
	21st to end	Night	57% 3 9% 19% 11% 1	4848
February	1st to 10th	Night	46% 4 13% 23% 12% 2	2395
	11th to 20th	Night	45% 4 9% 21% 17% 4	2220
	21st to end	Night	47% 4 8% 23% 14% 4	1884
March	1st to 10th	Night	55% 3 9% 20% 11% 2	3734
	11th to 20th	Night	42% 4 14% 24% 14% 2	3698
	21st to end	Night	49% 3 6% 14% 23% 5%	3466
April	1st to 10th	Night	49% 4 8% 20% 15% 3	1900
	11th to 20th	Night	46% 4 9% 20% 19% 1	1875
	21st to end	Night	46% 4 9% 23% 13% 5%	1773
May	1st to 10th	Night	56% 4 14% 15% 9% 2	2840
	11th to 20th	Night	56% 5% 14% 16% 9% 2	2664
	21st to end	Night	40% 6% 15% 25% 13% 1	2739
June	1st to 10th	Night	44% 6% 11% 22% 15% 1	1520
	11th to 20th	Night	44% 4 15% 26% 11% 1	1520
	21st to end	Night	39% 7% 14% 26% 14% 1	1520
July	1st to 10th	Night	43% 7% 16% 20% 13% 1	2480
	11th to 20th	Night	43% 5% 17% 25% 9% 1	2472
	21st to end	Night	50% 5% 12% 15% 16% 1	2651
August	1st to 10th	Night	53% 7% 13% 17% 9% 1	2643
	11th to 20th	Night	43% 6% 14% 29% 8% 1	3053
	21st to end	Night	27% 6% 17% 33% 16% 1	3476
September	1st to 10th	Night	40% 5% 10% 26% 18% 1	1900
	11th to 20th	Night	34% 3 11% 24% 26% 2	2042
	21st to end	Night	43% 6% 7% 22% 20% 2	2090
October	1st to 10th	Night	40% 5% 13% 23% 18% 2	3503
	11th to 20th	Night	28% 3 9% 27% 31% 2	3836
	21st to end	Night	33% 3 13% 29% 20% 2	4467
November	1st to 10th	Night	37% 4 12% 24% 20% 4	2537
	11th to 20th	Night	43% 4 9% 22% 19% 3	2484
	21st to end	Night	41% 3 13% 29% 12% 1	2489
December	1st to 10th	Night	47% 4 12% 22% 14% 1	2660
	11th to 20th	Night	45% 4 13% 18% 18% 2	3288
	21st to end	Night	53% 3 9% 23% 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	29% 23% 29% 16% 3	180
	11th to 20th	Day	31% 27% 27% 11% 4	180
	21st to end	Day	26% 27% 31% 9% 5% 1	209
February	1st to 10th	Day	33% 24% 27% 15% 1	343
	11th to 20th	Day	31% 25% 33% 9% 1	456
	21st to end	Day	32% 20% 32% 12% 4	382
March	1st to 10th	Day	28% 22% 32% 15% 3	460
	11th to 20th	Day	31% 23% 32% 12% 3	460
	21st to end	Day	32% 21% 30% 10% 5% 2	506
April	1st to 10th	Day	32% 23% 27% 12% 4 1	460
	11th to 20th	Day	31% 19% 29% 15% 5%	452
	21st to end	Day	30% 18% 33% 13% 5% 2	460
May	1st to 10th	Day	35% 16% 28% 12% 7% 1	463
	11th to 20th	Day	26% 15% 36% 15% 7% 1	487
	21st to end	Day	21% 14% 32% 23% 9% 2	529
June	1st to 10th	Day	20% 14% 30% 23% 10% 3	490
	11th to 20th	Day	16% 15% 39% 21% 8% 1	490
	21st to end	Day	17% 18% 31% 23% 9% 2	490
July	1st to 10th	Day	19% 8% 28% 29% 13% 3	485
	11th to 20th	Day	15% 6% 32% 32% 12% 3	484
	21st to end	Day	17% 9% 35% 29% 9% 2	532
August	1st to 10th	Day	15% 7% 32% 33% 9% 4	486
	11th to 20th	Day	14% 9% 32% 26% 15% 5%	479
	21st to end	Day	14% 10% 30% 26% 14% 7%	539
September	1st to 10th	Day	19% 11% 24% 25% 16% 4	490
	11th to 20th	Day	16% 11% 27% 24% 11% 11%	490
	21st to end	Day	21% 11% 35% 19% 9% 5%	490
October	1st to 10th	Day	30% 8% 25% 21% 11% 5%	490
	11th to 20th	Day	18% 17% 30% 25% 7% 3	472
	21st to end	Day	28% 13% 31% 19% 7% 2	429
November	1st to 10th	Day	21% 15% 31% 21% 10% 2	395
	11th to 20th	Day	31% 18% 28% 16% 8% 1	373
	21st to end	Day	26% 17% 31% 19% 6% 1	347
December	1st to 10th	Day	23% 25% 31% 16% 5%	180
	11th to 20th	Day	36% 22% 32% 9% 1	180
	21st to end	Day	28% 23% 29% 15% 3 2	198
January	1st to 10th	Night	22% 19% 39% 17% 3	760
	11th to 20th	Night	30% 19% 30% 19% 2	760
	21st to end	Night	23% 21% 34% 19% 3	836
February	1st to 10th	Night	23% 19% 34% 22% 2	760
	11th to 20th	Night	24% 22% 38% 14% 1	743
	21st to end	Night	29% 19% 34% 16% 2	628
March	1st to 10th	Night	26% 19% 34% 17% 3	760
	11th to 20th	Night	23% 20% 37% 17% 3	760
	21st to end	Night	27% 18% 35% 17% 3	836
April	1st to 10th	Night	25% 18% 34% 19% 3	760
	11th to 20th	Night	24% 18% 34% 19% 4	751
	21st to end	Night	25% 17% 34% 19% 4	633
May	1st to 10th	Night	29% 15% 30% 21% 5%	570
	11th to 20th	Night	23% 14% 37% 21% 4	477
	21st to end	Night	22% 7% 33% 31% 7% 1	411
June	1st to 10th	Night	21% 6% 32% 33% 8%	380
	11th to 20th	Night	20% 7% 30% 33% 9%	380
	21st to end	Night	17% 4 35% 36% 7% 1	380
July	1st to 10th	Night	14% 4 29% 39% 14%	370
	11th to 20th	Night	16% 2 25% 41% 14% 1	368
	21st to end	Night	13% 7% 31% 39% 10%	416
August	1st to 10th	Night	12% 6% 28% 42% 12% 1	460
	11th to 20th	Night	15% 4 25% 37% 18% 1	702
	21st to end	Night	15% 5% 25% 36% 17% 2	836
September	1st to 10th	Night	17% 5% 30% 34% 12% 1	760
	11th to 20th	Night	17% 7% 24% 32% 18% 2	760
	21st to end	Night	20% 7% 28% 29% 14% 2	760
October	1st to 10th	Night	25% 9% 27% 25% 12% 2	760
	11th to 20th	Night	21% 12% 30% 28% 9% 1	760
	21st to end	Night	28% 13% 30% 23% 6%	836
November	1st to 10th	Night	19% 12% 34% 26% 9% 1	780
	11th to 20th	Night	25% 14% 33% 21% 6% 1	765
	21st to end	Night	23% 17% 32% 22% 5%	760
December	1st to 10th	Night	28% 14% 33% 19% 5% 1	760
	11th to 20th	Night	25% 19% 31% 23% 2	760
	21st to end	Night	29% 15% 35% 19% 2	836

Page generated at 2024-11-08 22:45:35. Version ac07

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