Connecticut Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Connecticut Star Party clear sky chart from 2005-11-06 to 2024-12-02.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	101547
	Night	17% 8% 3 6% 4 4 4 4 5% 6% 38%	98101
Transparency	Day	46% 5% 11% 23% 14% 2	105068
	Night	45% 4 12% 23% 14% 2	102656
Seeing	Day	24% 19% 30% 18% 7% 2	15030
	Night	23% 18% 30% 22% 7% 1	24097

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	13% 9% 3 5% 5% 5% 4 3 5% 6% 42%	2517
	11th to 20th	Day	15% 10% 4 10% 6% 5% 5% 3 4 6% 32%	2520
	21st to end	Day	22% 13% 6% 8% 4 4 4 3 4 5% 29%	2868
February	1st to 10th	Day	16% 10% 3 7% 7% 5% 5% 4 5% 6% 33%	1739
	11th to 20th	Day	13% 8% 3 7% 6% 5% 4 4 5% 6% 38%	1848
	21st to end	Day	18% 12% 3 7% 4 5% 3 3 4 6% 35%	1570
March	1st to 10th	Day	24% 13% 3 7% 4 4 3 2 4 4 31%	3116
	11th to 20th	Day	11% 8% 3 7% 7% 6% 6% 4 6% 7% 35%	3271
	21st to end	Day	20% 8% 3 7% 4 4 4 3 5% 7% 35%	4166
April	1st to 10th	Day	18% 10% 3 7% 4 5% 5% 4 5% 6% 35%	2280
	11th to 20th	Day	17% 8% 2 7% 4 5% 5% 3 5% 6% 39%	2254
	21st to end	Day	19% 8% 3 7% 4 4 4 4 5% 6% 37%	2374
May	1st to 10th	Day	27% 10% 2 6% 4 3 4 3 4 7% 28%	4106
	11th to 20th	Day	22% 8% 3 7% 5% 4 4 3 6% 7% 32%	4352
	21st to end	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 42%	4837
June	1st to 10th	Day	17% 7% 2 6% 5% 5% 6% 5% 6% 8% 33%	2660
	11th to 20th	Day	16% 7% 2 6% 6% 5% 5% 4 7% 9% 34%	2660
	21st to end	Day	14% 7% 3 8% 5% 5% 5% 4 6% 9% 34%	2660
July	1st to 10th	Day	10% 7% 2 8% 6% 6% 6% 5% 6% 8% 36%	4440
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 10% 38%	4440
	21st to end	Day	15% 9% 3 9% 5% 5% 6% 4 6% 7% 31%	4814
August	1st to 10th	Day	20% 8% 2 7% 5% 5% 5% 4 6% 8% 29%	4311
	11th to 20th	Day	13% 6% 3 7% 4 5% 5% 5% 7% 9% 37%	3731
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 9% 41%	4180
September	1st to 10th	Day	13% 7% 3 6% 4 4 5% 4 6% 6% 42%	2280
	11th to 20th	Day	12% 6% 3 5% 3 3 4 3 5% 7% 49%	2166
	21st to end	Day	17% 7% 2 6% 4 4 4 4 6% 7% 39%	2090
October	1st to 10th	Day	21% 7% 2 6% 4 4 5% 3 5% 5% 39%	2029
	11th to 20th	Day	13% 7% 2 7% 3 3 4 4 5% 7% 43%	1895
	21st to end	Day	22% 7% 2 6% 4 4 4 4 6% 5% 36%	1881
November	1st to 10th	Day	13% 7% 3 6% 3 3 3 3 5% 7% 46%	1761
	11th to 20th	Day	18% 7% 2 4 3 3 4 4 5% 6% 43%	1800
	21st to end	Day	18% 9% 3 6% 4 4 4 3 5% 6% 40%	1725
December	1st to 10th	Day	18% 8% 4 8% 4 4 5% 4 6% 6% 33%	1528
	11th to 20th	Day	21% 8% 3 6% 3 3 3 4 5% 6% 38%	1906
	21st to end	Day	18% 12% 4 9% 6% 5% 4 4 5% 7% 26%	2772
January	1st to 10th	Night	15% 8% 2 5% 4 4 4 4 6% 6% 42%	4429
	11th to 20th	Night	15% 9% 4 8% 6% 5% 4 3 4 5% 37%	4440
	21st to end	Night	22% 14% 4 7% 5% 4 4 3 5% 4 29%	4785
February	1st to 10th	Night	16% 10% 3 6% 4 4 5% 4 5% 6% 36%	2439
	11th to 20th	Night	14% 9% 3 7% 5% 5% 5% 4 6% 6% 36%	2218
	21st to end	Night	18% 8% 3 7% 4 4 3 4 5% 6% 37%	1884
March	1st to 10th	Night	23% 12% 3 6% 4 4 4 3 4 5% 32%	3724
	11th to 20th	Night	11% 8% 3 7% 5% 5% 5% 4 6% 7% 39%	3682
	21st to end	Night	19% 10% 3 7% 4 4 3 3 5% 5% 37%	3466
April	1st to 10th	Night	17% 10% 4 7% 5% 4 6% 5% 5% 6% 32%	1900
	11th to 20th	Night	18% 8% 2 6% 6% 4 4 3 5% 6% 38%	1875
	21st to end	Night	19% 9% 3 6% 4 4 3 4 4 6% 39%	1805
May	1st to 10th	Night	26% 10% 3 7% 4 4 4 3 5% 7% 28%	2834
	11th to 20th	Night	20% 10% 3 8% 4 5% 4 3 5% 7% 31%	2570
	21st to end	Night	16% 6% 3 6% 4 4 4 4 5% 8% 42%	2738
June	1st to 10th	Night	17% 8% 2 6% 4 3 4 3 5% 6% 42%	1520
	11th to 20th	Night	14% 7% 2 6% 5% 4 4 4 8% 9% 36%	1520
	21st to end	Night	14% 6% 2 6% 4 3 5% 3 6% 9% 42%	1520
July	1st to 10th	Night	12% 6% 2 5% 4 4 6% 5% 7% 9% 39%	2520
	11th to 20th	Night	14% 8% 3 6% 4 4 4 4 6% 9% 39%	2520
	21st to end	Night	16% 10% 2 7% 6% 3 4 4 5% 6% 37%	2739
August	1st to 10th	Night	22% 7% 3 7% 5% 4 4 4 6% 7% 32%	2586
	11th to 20th	Night	15% 7% 2 6% 5% 5% 4 4 6% 7% 40%	3092
	21st to end	Night	10% 5% 2 5% 4 4 4 4 5% 7% 51%	3476
September	1st to 10th	Night	14% 6% 3 5% 5% 4 3 3 5% 7% 45%	1900
	11th to 20th	Night	12% 6% 3 5% 2 3 4 2 4 6% 54%	2014
	21st to end	Night	18% 7% 2 5% 3 3 4 4 4 6% 44%	2090
October	1st to 10th	Night	19% 7% 2 7% 4 3 4 2 4 6% 41%	2147
	11th to 20th	Night	14% 7% 2 6% 3 4 4 3 5% 6% 45%	2283
	21st to end	Night	21% 8% 2 6% 4 3 4 3 5% 6% 38%	2717
November	1st to 10th	Night	14% 6% 2 5% 3 4 3 4 5% 6% 47%	2537
	11th to 20th	Night	17% 8% 2 6% 3 4 3 4 5% 6% 42%	2600
	21st to end	Night	14% 8% 2 6% 5% 5% 4 3 6% 6% 41%	2673
December	1st to 10th	Night	19% 8% 3 7% 5% 4 4 4 5% 6% 34%	2686
	11th to 20th	Night	19% 8% 2 6% 4 5% 4 4 5% 6% 35%	3288
	21st to end	Night	21% 11% 3 7% 4 4 4 4 5% 6% 31%	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	43% 4 9% 34% 8% 2	2518
	11th to 20th	Day	53% 4 10% 24% 8% 1	2520
	21st to end	Day	59% 3 7% 21% 9% 1	2868
February	1st to 10th	Day	51% 4 12% 19% 12% 1	1739
	11th to 20th	Day	45% 5% 8% 23% 15% 2	1857
	21st to end	Day	51% 4 10% 20% 12% 3	1570
March	1st to 10th	Day	57% 2 10% 17% 12% 2	3119
	11th to 20th	Day	45% 5% 10% 29% 10% 2	3271
	21st to end	Day	50% 3 5% 16% 21% 5%	4166
April	1st to 10th	Day	49% 5% 8% 20% 14% 3	2280
	11th to 20th	Day	46% 4 9% 22% 16% 2	2254
	21st to end	Day	47% 4 9% 20% 16% 4	2374
May	1st to 10th	Day	56% 4 12% 16% 11% 1	4120
	11th to 20th	Day	52% 3 14% 21% 9% 1	4356
	21st to end	Day	39% 4 11% 28% 16% 1	4837
June	1st to 10th	Day	46% 6% 13% 23% 12% 1	2660
	11th to 20th	Day	44% 5% 14% 25% 11% 1	2660
	21st to end	Day	45% 6% 13% 23% 12% 1	2660
July	1st to 10th	Day	44% 7% 12% 21% 15% 1	4370
	11th to 20th	Day	40% 6% 16% 25% 12% 1	4365
	21st to end	Day	51% 5% 12% 18% 13% 1	4661
August	1st to 10th	Day	52% 6% 13% 20% 8%	4297
	11th to 20th	Day	41% 6% 15% 29% 8%	3767
	21st to end	Day	36% 6% 13% 31% 13% 1	4180
September	1st to 10th	Day	42% 5% 10% 25% 17% 1	2280
	11th to 20th	Day	35% 4 10% 25% 24% 2	2166
	21st to end	Day	43% 5% 10% 22% 17% 3	2090
October	1st to 10th	Day	41% 5% 8% 19% 24% 3	3367
	11th to 20th	Day	32% 4 8% 26% 26% 4	3123
	21st to end	Day	34% 4 14% 26% 19% 3	3081
November	1st to 10th	Day	36% 4 13% 26% 18% 3	1761
	11th to 20th	Day	41% 4 10% 23% 19% 3	1800
	21st to end	Day	45% 3 13% 25% 12% 2	1725
December	1st to 10th	Day	50% 4 14% 18% 13% 1	1528
	11th to 20th	Day	46% 5% 14% 21% 12% 2	1906
	21st to end	Day	57% 3 9% 20% 11%	2772
January	1st to 10th	Night	42% 3 11% 30% 11% 3	4429
	11th to 20th	Night	48% 4 11% 23% 11% 3	4440
	21st to end	Night	58% 3 8% 19% 10% 1	4785
February	1st to 10th	Night	48% 4 12% 22% 12% 2	2439
	11th to 20th	Night	46% 5% 9% 19% 18% 3	2220
	21st to end	Night	48% 4 8% 23% 13% 5%	1884
March	1st to 10th	Night	56% 3 8% 20% 11% 2	3734
	11th to 20th	Night	43% 4 15% 23% 14% 2	3683
	21st to end	Night	49% 3 6% 15% 22% 5%	3466
April	1st to 10th	Night	49% 4 9% 21% 14% 2	1900
	11th to 20th	Night	48% 4 9% 20% 18% 1	1875
	21st to end	Night	46% 3 9% 23% 16% 4	1805
May	1st to 10th	Night	57% 3 12% 16% 9% 2	2840
	11th to 20th	Night	55% 4 13% 18% 9% 2	2571
	21st to end	Night	42% 4 16% 24% 14% 1	2739
June	1st to 10th	Night	44% 4 10% 26% 14% 1	1520
	11th to 20th	Night	42% 4 17% 26% 10% 1	1520
	21st to end	Night	39% 6% 14% 27% 14% 1	1520
July	1st to 10th	Night	39% 7% 16% 21% 15% 1	2480
	11th to 20th	Night	42% 5% 14% 27% 11%	2472
	21st to end	Night	47% 5% 14% 16% 17% 2	2651
August	1st to 10th	Night	52% 6% 14% 19% 9% 1	2576
	11th to 20th	Night	42% 6% 14% 30% 8%	3122
	21st to end	Night	31% 6% 13% 36% 14%	3476
September	1st to 10th	Night	40% 5% 10% 27% 17% 1	1900
	11th to 20th	Night	33% 3 11% 26% 25% 1	2014
	21st to end	Night	42% 4 8% 24% 19% 2	2090
October	1st to 10th	Night	40% 5% 13% 22% 19% 1	3576
	11th to 20th	Night	30% 4 10% 26% 26% 4	3794
	21st to end	Night	35% 4 14% 29% 16% 2	4467
November	1st to 10th	Night	38% 4 11% 23% 21% 3	2537
	11th to 20th	Night	43% 3 10% 21% 19% 3	2600
	21st to end	Night	42% 4 14% 29% 11% 1	2673
December	1st to 10th	Night	49% 5% 11% 22% 12% 1	2686
	11th to 20th	Night	48% 5% 13% 18% 15% 2	3288
	21st to end	Night	54% 3 9% 22% 12%	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	31% 28% 26% 13% 2	180
	11th to 20th	Day	33% 30% 26% 9% 1	180
	21st to end	Day	21% 35% 31% 10% 3 1	225
February	1st to 10th	Day	35% 31% 25% 7% 1	299
	11th to 20th	Day	30% 30% 31% 8% 1	456
	21st to end	Day	35% 24% 29% 10% 3	382
March	1st to 10th	Day	29% 24% 34% 11% 2	460
	11th to 20th	Day	30% 28% 30% 10% 2 1	460
	21st to end	Day	34% 23% 30% 8% 5% 1	506
April	1st to 10th	Day	30% 25% 28% 9% 6% 1	460
	11th to 20th	Day	31% 26% 26% 12% 4 1	452
	21st to end	Day	30% 18% 35% 12% 3 1	460
May	1st to 10th	Day	35% 21% 25% 13% 5% 2	463
	11th to 20th	Day	23% 21% 31% 20% 5% 1	487
	21st to end	Day	23% 12% 31% 22% 9% 2	529
June	1st to 10th	Day	22% 14% 33% 19% 10% 2	490
	11th to 20th	Day	19% 13% 33% 24% 9% 1	490
	21st to end	Day	17% 16% 32% 25% 8% 1	490
July	1st to 10th	Day	15% 12% 33% 26% 12% 2	485
	11th to 20th	Day	14% 7% 33% 31% 11% 3	484
	21st to end	Day	15% 11% 36% 25% 11% 2	532
August	1st to 10th	Day	15% 9% 31% 28% 11% 5%	486
	11th to 20th	Day	15% 11% 30% 27% 11% 6%	479
	21st to end	Day	13% 13% 29% 26% 12% 6%	539
September	1st to 10th	Day	21% 12% 26% 20% 15% 6%	490
	11th to 20th	Day	15% 12% 27% 24% 13% 9%	490
	21st to end	Day	21% 13% 33% 20% 9% 4	490
October	1st to 10th	Day	29% 12% 27% 17% 11% 4	490
	11th to 20th	Day	21% 21% 28% 21% 7% 2	487
	21st to end	Day	29% 18% 27% 18% 6% 1	429
November	1st to 10th	Day	25% 19% 26% 20% 9% 1	395
	11th to 20th	Day	33% 23% 27% 14% 4 1	400
	21st to end	Day	30% 26% 26% 14% 4	325
December	1st to 10th	Day	27% 30% 28% 9% 5%	182
	11th to 20th	Day	38% 25% 27% 8% 2	180
	21st to end	Day	29% 29% 27% 13% 3	198
January	1st to 10th	Night	23% 26% 34% 14% 3	760
	11th to 20th	Night	29% 24% 31% 14% 2	760
	21st to end	Night	23% 25% 34% 15% 2	836
February	1st to 10th	Night	27% 24% 31% 17% 2	760
	11th to 20th	Night	25% 28% 35% 11% 1	743
	21st to end	Night	31% 25% 27% 15% 3	628
March	1st to 10th	Night	25% 24% 33% 15% 2	760
	11th to 20th	Night	23% 27% 31% 16% 3	760
	21st to end	Night	26% 25% 29% 15% 4	836
April	1st to 10th	Night	26% 21% 32% 18% 3	760
	11th to 20th	Night	25% 21% 32% 15% 6%	751
	21st to end	Night	25% 21% 32% 17% 5%	665
May	1st to 10th	Night	30% 16% 29% 19% 6% 1	570
	11th to 20th	Night	22% 16% 37% 20% 4	423
	21st to end	Night	20% 9% 29% 32% 9% 1	411
June	1st to 10th	Night	21% 9% 30% 30% 9% 1	380
	11th to 20th	Night	20% 8% 30% 29% 12% 1	380
	21st to end	Night	19% 6% 28% 34% 12% 1	380
July	1st to 10th	Night	18% 6% 22% 36% 17%	370
	11th to 20th	Night	15% 6% 24% 39% 15% 1	368
	21st to end	Night	13% 6% 27% 38% 16%	416
August	1st to 10th	Night	13% 4 27% 40% 15% 1	419
	11th to 20th	Night	17% 5% 23% 36% 19% 2	745
	21st to end	Night	17% 6% 24% 33% 18% 2	836
September	1st to 10th	Night	18% 8% 29% 30% 13% 3	760
	11th to 20th	Night	16% 7% 25% 30% 18% 4	760
	21st to end	Night	23% 9% 26% 26% 13% 2	760
October	1st to 10th	Night	23% 15% 24% 25% 11% 2	760
	11th to 20th	Night	19% 18% 30% 23% 9% 1	760
	21st to end	Night	29% 16% 30% 19% 6%	836
November	1st to 10th	Night	20% 19% 31% 21% 8% 1	780
	11th to 20th	Night	24% 22% 30% 17% 7% 1	800
	21st to end	Night	23% 22% 31% 20% 5% 1	800
December	1st to 10th	Night	28% 22% 30% 16% 4 1	768
	11th to 20th	Night	25% 27% 28% 18% 3	760
	21st to end	Night	29% 23% 32% 13% 2	836

Page generated at 2024-11-29 10:43:09. Version ac07

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