Hanover College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hanover College 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	14% 8% 3 7% 4 4 4 4 5% 7% 39%	101112
	Night	14% 9% 3 7% 4 4 4 3 5% 7% 39%	97930
Transparency	Day	23% 47% 6% 14% 9% 1	104796
	Night	24% 47% 6% 13% 10% 1	102385
Seeing	Day	18% 14% 27% 23% 13% 5%	15395
	Night	18% 11% 27% 28% 14% 2	25148

By Month

Percentage Cloud Cover SE (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% 17% 6% 8% 4 4 4 4 5% 6% 29%	2527
	11th to 20th	Day	18% 11% 5% 12% 5% 6% 4 2 4 4 28%	2564
	21st to end	Day	28% 15% 7% 7% 4 3 3 3 4 5% 22%	3124
February	1st to 10th	Day	17% 13% 4 10% 4 3 3 2 5% 5% 33%	1891
	11th to 20th	Day	17% 10% 3 8% 5% 5% 4 3 4 6% 35%	1848
	21st to end	Day	17% 15% 4 8% 4 3 3 4 4 6% 31%	1570
March	1st to 10th	Day	25% 13% 3 7% 4 3 3 2 4 5% 31%	3120
	11th to 20th	Day	14% 7% 3 6% 5% 4 4 3 5% 7% 43%	3432
	21st to end	Day	15% 8% 3 8% 5% 4 4 5% 6% 7% 36%	3875
April	1st to 10th	Day	15% 9% 2 6% 4 5% 4 4 6% 7% 37%	2280
	11th to 20th	Day	17% 8% 3 6% 4 5% 4 3 5% 6% 40%	2254
	21st to end	Day	18% 7% 3 6% 4 4 4 4 6% 8% 37%	2458
May	1st to 10th	Day	20% 9% 3 7% 4 5% 5% 4 6% 8% 29%	4082
	11th to 20th	Day	19% 8% 2 6% 4 3 4 3 5% 7% 38%	4081
	21st to end	Day	12% 6% 2 7% 6% 5% 6% 5% 7% 9% 36%	4476
June	1st to 10th	Day	10% 5% 2 6% 6% 5% 5% 4 5% 8% 43%	2552
	11th to 20th	Day	8% 5% 2 5% 5% 5% 5% 4 7% 8% 46%	2660
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 4 6% 10% 43%	2660
July	1st to 10th	Day	13% 6% 2 6% 5% 4 5% 4 6% 9% 39%	4440
	11th to 20th	Day	7% 4 2 6% 4 4 5% 4 6% 10% 48%	4418
	21st to end	Day	11% 7% 3 10% 6% 6% 7% 5% 8% 9% 29%	4466
August	1st to 10th	Day	7% 5% 2 5% 4 4 5% 4 7% 10% 47%	4104
	11th to 20th	Day	8% 5% 2 6% 4 5% 5% 5% 8% 10% 42%	3896
	21st to end	Day	5% 4 2 5% 3 4 4 3 6% 8% 56%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 3 5% 7% 47%	2208
	11th to 20th	Day	9% 4 2 6% 4 5% 5% 4 5% 8% 48%	2090
	21st to end	Day	14% 5% 2 5% 5% 4 3 3 5% 6% 48%	2090
October	1st to 10th	Day	10% 4 2 5% 4 4 4 3 4 5% 54%	2090
	11th to 20th	Day	12% 6% 2 6% 4 3 4 3 5% 7% 47%	1990
	21st to end	Day	18% 9% 2 6% 4 4 4 3 5% 5% 40%	1885
November	1st to 10th	Day	10% 6% 2 5% 3 3 3 3 4 5% 56%	1708
	11th to 20th	Day	16% 11% 3 6% 4 4 3 3 6% 6% 40%	1710
	21st to end	Day	19% 8% 3 6% 4 3 3 3 4 6% 41%	1710
December	1st to 10th	Day	22% 11% 4 8% 5% 4 4 2 4 5% 31%	1710
	11th to 20th	Day	15% 16% 4 9% 5% 4 4 3 3 5% 31%	2153
	21st to end	Day	20% 20% 5% 8% 5% 4 4 3 4 5% 22%	2810
January	1st to 10th	Night	18% 17% 4 9% 4 4 5% 3 5% 6% 25%	4428
	11th to 20th	Night	16% 16% 5% 13% 7% 4 3 2 3 4 25%	4400
	21st to end	Night	25% 17% 5% 8% 4 2 3 2 4 5% 25%	4532
February	1st to 10th	Night	21% 13% 3 8% 5% 4 4 4 5% 5% 29%	2285
	11th to 20th	Night	17% 12% 3 9% 5% 4 4 4 4 5% 34%	2218
	21st to end	Night	21% 13% 4 8% 4 4 4 3 4 5% 31%	1884
March	1st to 10th	Night	23% 12% 3 7% 4 3 3 3 4 5% 33%	3733
	11th to 20th	Night	14% 7% 2 5% 3 4 4 3 6% 6% 47%	3527
	21st to end	Night	16% 8% 3 7% 5% 4 4 3 5% 6% 39%	3771
April	1st to 10th	Night	13% 7% 2 7% 4 4 5% 3 7% 6% 41%	1900
	11th to 20th	Night	16% 9% 3 5% 4 4 4 3 5% 5% 41%	1875
	21st to end	Night	17% 8% 3 5% 4 5% 4 3 5% 7% 38%	1720
May	1st to 10th	Night	17% 10% 4 10% 5% 5% 5% 4 5% 7% 28%	2813
	11th to 20th	Night	17% 6% 2 6% 5% 4 4 3 6% 8% 41%	2812
	21st to end	Night	9% 6% 2 6% 5% 5% 4 5% 7% 9% 43%	3079
June	1st to 10th	Night	10% 6% 2 5% 3 4 4 3 6% 9% 48%	1623
	11th to 20th	Night	5% 4 2 6% 4 4 5% 4 7% 9% 49%	1520
	21st to end	Night	5% 3 2 5% 4 4 4 5% 8% 12% 48%	1520
July	1st to 10th	Night	9% 5% 2 6% 5% 3 4 4 5% 9% 47%	2530
	11th to 20th	Night	5% 3 2 5% 4 4 4 4 7% 9% 54%	2547
	21st to end	Night	11% 7% 3 7% 6% 6% 6% 5% 8% 9% 33%	3087
August	1st to 10th	Night	7% 5% 2 6% 4 3 4 3 6% 10% 51%	2825
	11th to 20th	Night	6% 5% 2 6% 5% 5% 5% 3 6% 9% 47%	2930
	21st to end	Night	4 3 1 4 3 3 4 3 5% 10% 61%	3476
September	1st to 10th	Night	12% 5% 1 5% 4 3 3 3 5% 8% 52%	1952
	11th to 20th	Night	9% 5% 2 4 4 3 3 3 6% 8% 54%	2090
	21st to end	Night	13% 4 1 6% 4 4 3 3 4 6% 51%	2090
October	1st to 10th	Night	7% 5% 2 5% 3 4 4 3 4 6% 58%	2090
	11th to 20th	Night	14% 6% 2 5% 4 4 3 4 5% 6% 47%	2190
	21st to end	Night	17% 7% 3 6% 4 4 3 3 5% 6% 42%	2710
November	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 5% 5% 50%	2470
	11th to 20th	Night	15% 8% 3 6% 4 4 3 3 5% 7% 43%	2470
	21st to end	Night	18% 10% 3 6% 5% 4 3 3 4 6% 38%	2470
December	1st to 10th	Night	19% 12% 4 7% 4 4 4 4 5% 6% 32%	2470
	11th to 20th	Night	20% 10% 4 9% 4 4 3 3 5% 6% 33%	3042
	21st to end	Night	20% 19% 5% 10% 6% 5% 5% 3 4 4 19%	4851

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	37% 38% 8% 10% 7%	2528
	11th to 20th	Day	40% 37% 6% 12% 4 1	2564
	21st to end	Day	45% 40% 3 10% 2	3124
February	1st to 10th	Day	19% 65% 4 6% 5% 1	1891
	11th to 20th	Day	19% 64% 3 8% 6%	1858
	21st to end	Day	17% 64% 3 9% 5% 1	1570
March	1st to 10th	Day	40% 40% 2 9% 4 4	3120
	11th to 20th	Day	21% 40% 6% 21% 12% 1	3432
	21st to end	Day	25% 42% 9% 14% 10%	3875
April	1st to 10th	Day	19% 66% 4 8% 3	2280
	11th to 20th	Day	16% 66% 4 8% 5% 1	2254
	21st to end	Day	15% 66% 4 10% 5% 1	2458
May	1st to 10th	Day	31% 43% 10% 11% 4	4120
	11th to 20th	Day	28% 41% 7% 17% 7%	4085
	21st to end	Day	26% 43% 8% 10% 12% 1	4489
June	1st to 10th	Day	15% 66% 4 8% 6% 1	2552
	11th to 20th	Day	14% 67% 4 8% 7%	2660
	21st to end	Day	15% 66% 6% 7% 6% 1	2660
July	1st to 10th	Day	27% 38% 7% 14% 13% 1	4371
	11th to 20th	Day	17% 38% 7% 24% 13%	4343
	21st to end	Day	35% 39% 8% 8% 9% 1	4324
August	1st to 10th	Day	18% 41% 10% 25% 6%	4091
	11th to 20th	Day	21% 40% 8% 22% 8% 1	3935
	21st to end	Day	14% 39% 9% 25% 12% 1	4179
September	1st to 10th	Day	12% 61% 4 11% 10% 2	2208
	11th to 20th	Day	12% 61% 7% 10% 9% 1	2090
	21st to end	Day	16% 60% 4 11% 8%	2090
October	1st to 10th	Day	11% 37% 3 22% 26% 1	3480
	11th to 20th	Day	15% 38% 6% 18% 22% 1	3282
	21st to end	Day	19% 37% 5% 17% 19% 2	3085
November	1st to 10th	Day	16% 58% 5% 13% 7% 1	1708
	11th to 20th	Day	18% 59% 2 10% 9% 2	1710
	21st to end	Day	20% 60% 5% 10% 4	1710
December	1st to 10th	Day	25% 59% 4 6% 5% 1	1710
	11th to 20th	Day	28% 48% 3 12% 8% 1	2150
	21st to end	Day	44% 37% 5% 8% 6% 1	2810
January	1st to 10th	Night	40% 39% 6% 8% 7%	4428
	11th to 20th	Night	43% 36% 5% 10% 5% 1	4400
	21st to end	Night	41% 40% 4 9% 6%	4532
February	1st to 10th	Night	20% 65% 3 7% 4 1	2285
	11th to 20th	Night	19% 64% 4 7% 6%	2219
	21st to end	Night	20% 64% 3 7% 5% 1	1884
March	1st to 10th	Night	38% 41% 4 13% 4 1	3733
	11th to 20th	Night	17% 42% 7% 18% 15% 1	3527
	21st to end	Night	24% 41% 6% 18% 10% 1	3771
April	1st to 10th	Night	18% 66% 4 7% 4 1	1900
	11th to 20th	Night	16% 66% 4 7% 6% 1	1875
	21st to end	Night	16% 65% 4 9% 4 2	1720
May	1st to 10th	Night	35% 44% 6% 11% 3 1	2840
	11th to 20th	Night	24% 42% 11% 20% 3	2813
	21st to end	Night	21% 43% 9% 16% 10% 1	3087
June	1st to 10th	Night	12% 65% 4 10% 7% 2	1623
	11th to 20th	Night	11% 67% 5% 8% 8% 2	1520
	21st to end	Night	11% 65% 7% 9% 8% 1	1520
July	1st to 10th	Night	23% 39% 6% 18% 12% 3	2490
	11th to 20th	Night	15% 38% 9% 25% 13% 1	2499
	21st to end	Night	30% 38% 10% 13% 6% 2	2988
August	1st to 10th	Night	19% 40% 9% 26% 6%	2814
	11th to 20th	Night	22% 39% 9% 20% 10%	2957
	21st to end	Night	11% 38% 10% 25% 16% 1	3476
September	1st to 10th	Night	10% 61% 6% 11% 10% 2	1952
	11th to 20th	Night	10% 60% 5% 11% 11% 2	2090
	21st to end	Night	14% 60% 5% 11% 9% 1	2090
October	1st to 10th	Night	11% 37% 4 14% 33% 1	3480
	11th to 20th	Night	12% 37% 6% 15% 29% 2	3637
	21st to end	Night	18% 37% 5% 15% 21% 5%	4460
November	1st to 10th	Night	20% 58% 4 9% 7% 1	2470
	11th to 20th	Night	17% 60% 3 9% 9% 2	2470
	21st to end	Night	22% 59% 4 10% 4	2470
December	1st to 10th	Night	22% 61% 5% 7% 5% 1	2470
	11th to 20th	Night	25% 49% 5% 11% 9% 1	3044
	21st to end	Night	47% 38% 6% 6% 3 1	4851

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	27% 22% 33% 15% 3	270
	11th to 20th	Day	31% 29% 27% 12% 1	270
	21st to end	Day	32% 27% 29% 9% 2	297
February	1st to 10th	Day	29% 29% 27% 13% 1 1	270
	11th to 20th	Day	29% 29% 32% 9% 1 1	270
	21st to end	Day	31% 21% 38% 8% 2	225
March	1st to 10th	Day	26% 31% 33% 9% 1	270
	11th to 20th	Day	27% 23% 33% 12% 5%	425
	21st to end	Day	32% 20% 29% 15% 4 1	506
April	1st to 10th	Day	26% 20% 30% 17% 7% 1	460
	11th to 20th	Day	22% 20% 27% 20% 9% 2	452
	21st to end	Day	24% 19% 35% 15% 6% 1	460
May	1st to 10th	Day	23% 16% 34% 16% 7% 4	463
	11th to 20th	Day	19% 13% 29% 23% 10% 5%	487
	21st to end	Day	14% 10% 26% 25% 17% 8%	529
June	1st to 10th	Day	12% 9% 28% 28% 18% 6%	572
	11th to 20th	Day	11% 6% 22% 34% 20% 7%	680
	21st to end	Day	10% 9% 27% 27% 20% 7%	680
July	1st to 10th	Day	15% 5% 18% 26% 22% 15%	671
	11th to 20th	Day	8% 5% 25% 29% 22% 11%	659
	21st to end	Day	12% 4 23% 31% 21% 10%	532
August	1st to 10th	Day	8% 6% 18% 30% 24% 13%	486
	11th to 20th	Day	13% 6% 21% 30% 21% 9%	479
	21st to end	Day	9% 3 17% 28% 29% 13%	539
September	1st to 10th	Day	11% 5% 19% 33% 25% 7%	490
	11th to 20th	Day	8% 4 19% 33% 25% 11%	490
	21st to end	Day	17% 10% 20% 29% 19% 6%	490
October	1st to 10th	Day	10% 8% 25% 33% 19% 5%	490
	11th to 20th	Day	15% 19% 31% 20% 12% 3	490
	21st to end	Day	26% 15% 37% 19% 3	334
November	1st to 10th	Day	12% 20% 35% 23% 8% 2	282
	11th to 20th	Day	26% 18% 29% 23% 3 1	270
	21st to end	Day	29% 16% 31% 20% 3	270
December	1st to 10th	Day	26% 23% 33% 15% 3 1	270
	11th to 20th	Day	24% 20% 38% 13% 6%	270
	21st to end	Day	30% 27% 30% 10% 3	297
January	1st to 10th	Night	23% 20% 33% 20% 4	950
	11th to 20th	Night	29% 18% 33% 16% 3	923
	21st to end	Night	25% 18% 33% 21% 2	836
February	1st to 10th	Night	27% 15% 34% 22% 2	760
	11th to 20th	Night	23% 20% 37% 19% 1	743
	21st to end	Night	29% 17% 37% 16% 1	628
March	1st to 10th	Night	23% 18% 34% 21% 4	760
	11th to 20th	Night	23% 15% 35% 19% 6% 1	760
	21st to end	Night	23% 14% 31% 26% 6%	815
April	1st to 10th	Night	17% 13% 36% 27% 7%	570
	11th to 20th	Night	20% 12% 32% 25% 10% 1	563
	21st to end	Night	23% 8% 34% 28% 7% 1	570
May	1st to 10th	Night	16% 11% 34% 26% 11% 1	570
	11th to 20th	Night	16% 7% 26% 31% 18% 2	561
	21st to end	Night	9% 3 24% 35% 25% 4	617
June	1st to 10th	Night	12% 3 20% 42% 21% 2	570
	11th to 20th	Night	7% 4 19% 45% 22% 3	570
	21st to end	Night	7% 2 24% 38% 27% 2	570
July	1st to 10th	Night	11% 3 13% 32% 31% 10%	555
	11th to 20th	Night	5% 3 16% 39% 33% 5%	552
	21st to end	Night	10% 3 13% 40% 29% 5%	624
August	1st to 10th	Night	9% 2 10% 35% 38% 5%	567
	11th to 20th	Night	7% 2 13% 42% 31% 5%	564
	21st to end	Night	7% 2 13% 32% 40% 6%	627
September	1st to 10th	Night	11% 4 14% 35% 32% 4	622
	11th to 20th	Night	10% 2 16% 33% 34% 5%	760
	21st to end	Night	15% 6% 22% 31% 23% 3	760
October	1st to 10th	Night	10% 6% 24% 32% 24% 4	760
	11th to 20th	Night	17% 9% 28% 31% 13% 2	760
	21st to end	Night	21% 11% 33% 23% 11% 1	836
November	1st to 10th	Night	14% 10% 32% 28% 14% 1	760
	11th to 20th	Night	19% 16% 29% 25% 9% 1	760
	21st to end	Night	25% 12% 25% 30% 7%	760
December	1st to 10th	Night	25% 15% 32% 23% 5%	760
	11th to 20th	Night	25% 14% 33% 21% 6% 1	760
	21st to end	Night	29% 18% 31% 19% 3	1025

Page generated at 2024-11-03 02:11:24. Version ac07

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