Hiram College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hiram College clear sky chart from 2005-11-06 to 2025-02-06.

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% 12% 4 10% 5% 5% 5% 4 5% 7% 29%	108497
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 29%	109761
Transparency	Day	53% 5% 11% 19% 10% 1	112173
	Night	54% 5% 11% 19% 10% 1	114224
Seeing	Day	22% 15% 28% 20% 11% 4	14843
	Night	21% 13% 27% 25% 12% 1	24723

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	14% 20% 8% 26% 4 3 3 2 3 4 12%	4056
	11th to 20th	Day	11% 21% 8% 21% 8% 7% 4 2 3 4 10%	4060
	21st to end	Day	21% 19% 9% 14% 7% 5% 4 2 3 3 12%	4466
February	1st to 10th	Day	16% 19% 6% 12% 8% 6% 3 3 4 5% 20%	1755
	11th to 20th	Day	14% 16% 6% 15% 8% 5% 4 2 5% 5% 19%	1690
	21st to end	Day	17% 17% 4 13% 5% 4 4 4 4 5% 22%	1570
March	1st to 10th	Day	22% 12% 7% 9% 5% 4 4 3 4 6% 25%	3391
	11th to 20th	Day	13% 13% 5% 10% 6% 5% 3 3 4 5% 32%	3480
	21st to end	Day	20% 12% 5% 9% 5% 4 4 3 4 5% 29%	3815
April	1st to 10th	Day	15% 14% 3 8% 5% 3 4 3 5% 6% 31%	2147
	11th to 20th	Day	18% 12% 3 7% 5% 4 4 3 4 6% 33%	2384
	21st to end	Day	20% 12% 3 8% 4 4 4 2 4 6% 33%	2470
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 5% 4 5% 6% 29%	4082
	11th to 20th	Day	20% 10% 3 7% 4 4 4 3 5% 7% 32%	4081
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 5% 6% 8% 40%	4628
June	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 5% 6% 8% 36%	2660
	11th to 20th	Day	12% 8% 3 7% 5% 4 4 4 6% 8% 38%	2660
	21st to end	Day	12% 5% 2 6% 5% 5% 4 5% 7% 10% 39%	2660
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 5% 6% 10% 39%	4197
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 5% 6% 10% 42%	4120
	21st to end	Day	11% 6% 3 8% 5% 5% 6% 5% 6% 8% 38%	4466
August	1st to 10th	Day	15% 7% 3 6% 5% 5% 5% 4 7% 9% 33%	4104
	11th to 20th	Day	13% 6% 3 7% 4 5% 6% 5% 8% 9% 34%	4044
	21st to end	Day	10% 5% 2 7% 5% 5% 6% 4 6% 9% 40%	4418
September	1st to 10th	Day	15% 6% 3 6% 4 5% 5% 3 6% 7% 41%	2211
	11th to 20th	Day	11% 6% 2 7% 4 4 4 4 7% 9% 42%	2090
	21st to end	Day	20% 9% 2 7% 3 4 4 3 4 7% 37%	2090
October	1st to 10th	Day	15% 6% 3 8% 4 5% 5% 3 6% 7% 38%	1944
	11th to 20th	Day	22% 11% 3 7% 5% 4 4 3 4 5% 33%	1900
	21st to end	Day	22% 12% 3 8% 5% 4 4 4 5% 6% 27%	2090
November	1st to 10th	Day	12% 10% 4 7% 5% 4 4 5% 6% 6% 36%	1781
	11th to 20th	Day	18% 17% 4 8% 5% 4 4 4 4 6% 26%	1727
	21st to end	Day	18% 19% 6% 10% 5% 5% 5% 4 4 6% 18%	1600
December	1st to 10th	Day	17% 18% 9% 15% 5% 5% 4 4 4 4 16%	2600
	11th to 20th	Day	23% 22% 7% 11% 6% 3 3 3 4 4 15%	2990
	21st to end	Day	25% 23% 7% 14% 6% 4 3 2 3 3 9%	4070
January	1st to 10th	Night	14% 18% 10% 26% 5% 3 3 3 4 4 11%	5889
	11th to 20th	Night	12% 19% 10% 19% 9% 6% 6% 4 3 3 10%	5900
	21st to end	Night	20% 18% 8% 14% 7% 4 5% 3 3 4 15%	6490
February	1st to 10th	Night	19% 16% 5% 13% 7% 5% 4 3 4 5% 19%	2536
	11th to 20th	Night	15% 15% 6% 14% 7% 5% 5% 3 4 5% 20%	2374
	21st to end	Night	21% 13% 4 13% 5% 5% 4 3 4 5% 23%	1884
March	1st to 10th	Night	22% 15% 4 7% 4 4 3 2 3 5% 32%	3462
	11th to 20th	Night	15% 12% 6% 8% 5% 4 5% 4 5% 5% 32%	3480
	21st to end	Night	18% 12% 4 9% 4 4 4 4 4 4 33%	3817
April	1st to 10th	Night	17% 14% 3 8% 5% 3 5% 3 5% 5% 31%	2033
	11th to 20th	Night	15% 11% 3 7% 5% 4 5% 4 7% 6% 34%	1761
	21st to end	Night	15% 9% 3 7% 5% 5% 4 4 6% 6% 35%	1710
May	1st to 10th	Night	25% 10% 2 7% 4 4 4 3 6% 6% 29%	2813
	11th to 20th	Night	17% 9% 3 5% 4 4 4 4 5% 8% 37%	2812
	21st to end	Night	11% 5% 2 4 4 4 4 4 7% 11% 45%	2925
June	1st to 10th	Night	10% 7% 3 5% 5% 5% 6% 5% 7% 7% 41%	1520
	11th to 20th	Night	10% 6% 2 7% 4 5% 5% 4 7% 8% 42%	1520
	21st to end	Night	12% 4 2 6% 4 4 6% 4 8% 10% 41%	1520
July	1st to 10th	Night	10% 6% 3 6% 5% 4 4 3 5% 9% 46%	2758
	11th to 20th	Night	10% 4 2 5% 4 4 4 4 6% 8% 48%	2840
	21st to end	Night	8% 5% 2 7% 5% 4 5% 4 6% 8% 45%	3087
August	1st to 10th	Night	14% 8% 2 7% 4 4 4 5% 5% 7% 40%	2825
	11th to 20th	Night	14% 7% 3 7% 4 4 4 3 4 6% 44%	2785
	21st to end	Night	9% 5% 2 7% 5% 5% 5% 4 6% 8% 45%	3204
September	1st to 10th	Night	13% 6% 2 5% 3 4 5% 4 5% 7% 47%	1966
	11th to 20th	Night	10% 5% 2 4 4 4 4 4 4 7% 52%	2090
	21st to end	Night	17% 7% 3 7% 6% 4 3 4 5% 6% 39%	2090
October	1st to 10th	Night	14% 7% 2 5% 4 4 4 4 6% 7% 43%	2234
	11th to 20th	Night	18% 8% 3 8% 5% 4 4 4 5% 6% 34%	2280
	21st to end	Night	23% 10% 3 6% 4 4 4 3 6% 6% 31%	2508
November	1st to 10th	Night	13% 10% 2 6% 4 4 4 4 5% 7% 39%	2512
	11th to 20th	Night	17% 16% 5% 8% 5% 4 5% 3 5% 6% 27%	2670
	21st to end	Night	19% 17% 5% 9% 6% 4 4 4 5% 5% 22%	2800
December	1st to 10th	Night	14% 18% 8% 13% 5% 6% 5% 3 5% 5% 17%	4580
	11th to 20th	Night	19% 22% 9% 11% 5% 4 3 3 3 4 17%	5205
	21st to end	Night	24% 21% 7% 11% 5% 4 4 3 4 5% 12%	6881

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	78% 3 8% 8% 3	4057
	11th to 20th	Day	80% 3 7% 7% 3	4060
	21st to end	Day	78% 3 7% 9% 3	4466
February	1st to 10th	Day	68% 3 9% 14% 6%	1755
	11th to 20th	Day	67% 4 7% 15% 7%	1699
	21st to end	Day	63% 3 10% 15% 6% 2	1570
March	1st to 10th	Day	60% 4 10% 21% 5%	3391
	11th to 20th	Day	53% 5% 13% 21% 7% 1	3480
	21st to end	Day	57% 4 9% 18% 12% 1	3815
April	1st to 10th	Day	53% 4 12% 17% 13% 1	2147
	11th to 20th	Day	52% 4 11% 17% 13% 2	2384
	21st to end	Day	52% 4 10% 21% 10% 2	2470
May	1st to 10th	Day	54% 5% 9% 22% 9% 1	4120
	11th to 20th	Day	51% 5% 11% 22% 9% 1	4085
	21st to end	Day	40% 6% 12% 21% 15% 5%	4642
June	1st to 10th	Day	45% 6% 11% 25% 12% 1	2660
	11th to 20th	Day	43% 5% 14% 22% 15% 2	2660
	21st to end	Day	39% 7% 13% 24% 15% 2	2660
July	1st to 10th	Day	39% 7% 12% 23% 15% 3	4132
	11th to 20th	Day	35% 6% 13% 26% 18% 1	4051
	21st to end	Day	41% 8% 13% 18% 19% 1	4324
August	1st to 10th	Day	45% 7% 15% 23% 11%	4091
	11th to 20th	Day	41% 8% 13% 29% 9% 1	4083
	21st to end	Day	38% 7% 14% 29% 11% 2	4418
September	1st to 10th	Day	41% 5% 13% 22% 16% 3	2211
	11th to 20th	Day	37% 5% 14% 25% 17% 1	2090
	21st to end	Day	48% 4 9% 24% 13% 1	2090
October	1st to 10th	Day	34% 6% 13% 27% 19% 1	3230
	11th to 20th	Day	48% 5% 10% 20% 13% 4	3140
	21st to end	Day	42% 4 14% 24% 14% 1	3428
November	1st to 10th	Day	46% 5% 11% 23% 14% 1	1781
	11th to 20th	Day	57% 5% 10% 17% 8% 3	1727
	21st to end	Day	67% 4 9% 13% 6%	1600
December	1st to 10th	Day	70% 6% 11% 10% 2	2600
	11th to 20th	Day	73% 4 8% 13% 2	2986
	21st to end	Day	81% 3 7% 7% 2	4070
January	1st to 10th	Night	77% 4 7% 9% 4	5889
	11th to 20th	Night	77% 5% 8% 8% 2	5900
	21st to end	Night	74% 3 9% 10% 4 1	6490
February	1st to 10th	Night	67% 4 10% 14% 5%	2536
	11th to 20th	Night	66% 4 8% 16% 6%	2376
	21st to end	Night	64% 4 8% 15% 8% 1	1884
March	1st to 10th	Night	56% 4 10% 21% 9%	3462
	11th to 20th	Night	51% 7% 16% 17% 9% 1	3480
	21st to end	Night	50% 6% 8% 22% 12% 1	3817
April	1st to 10th	Night	53% 5% 10% 17% 13% 2	2033
	11th to 20th	Night	48% 5% 13% 18% 14% 2	1761
	21st to end	Night	46% 5% 11% 21% 14% 3	1710
May	1st to 10th	Night	56% 4 9% 19% 10% 2	2840
	11th to 20th	Night	45% 6% 12% 24% 11% 2	2813
	21st to end	Night	31% 6% 15% 27% 18% 3	2932
June	1st to 10th	Night	40% 6% 11% 25% 15% 2	1520
	11th to 20th	Night	38% 6% 14% 23% 18% 2	1520
	21st to end	Night	37% 6% 14% 25% 17% 1	1520
July	1st to 10th	Night	38% 5% 12% 24% 18% 3	2713
	11th to 20th	Night	32% 6% 13% 29% 18% 2	2786
	21st to end	Night	35% 7% 14% 18% 24% 2	2988
August	1st to 10th	Night	43% 6% 12% 24% 14% 1	2814
	11th to 20th	Night	41% 6% 12% 29% 11% 1	2812
	21st to end	Night	35% 6% 13% 29% 14% 2	3204
September	1st to 10th	Night	36% 5% 12% 27% 17% 3	1966
	11th to 20th	Night	31% 4 14% 27% 22% 2	2090
	21st to end	Night	45% 4 11% 22% 17% 1	2090
October	1st to 10th	Night	33% 5% 10% 28% 22% 1	3728
	11th to 20th	Night	42% 5% 11% 22% 16% 3	3779
	21st to end	Night	38% 4 13% 28% 15% 1	4120
November	1st to 10th	Night	42% 5% 12% 24% 14% 3	2512
	11th to 20th	Night	58% 4 9% 17% 8% 3	2670
	21st to end	Night	63% 3 12% 17% 5%	2800
December	1st to 10th	Night	67% 5% 13% 11% 3	4580
	11th to 20th	Night	71% 3 9% 14% 2	5208
	21st to end	Night	74% 5% 10% 10% 1	6881

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	33% 28% 27% 9% 3	300
	11th to 20th	Day	33% 27% 30% 7% 2	300
	21st to end	Day	31% 32% 27% 8% 2 1	330
February	1st to 10th	Day	32% 27% 33% 8% 1	285
	11th to 20th	Day	31% 33% 30% 5% 1	270
	21st to end	Day	34% 30% 31% 5%	225
March	1st to 10th	Day	26% 24% 32% 13% 6%	427
	11th to 20th	Day	28% 21% 33% 11% 5% 1	460
	21st to end	Day	33% 22% 26% 15% 4	506
April	1st to 10th	Day	25% 22% 30% 14% 7% 1	460
	11th to 20th	Day	30% 16% 29% 15% 8% 3	452
	21st to end	Day	28% 18% 30% 18% 5% 2	460
May	1st to 10th	Day	29% 17% 28% 17% 6% 3	463
	11th to 20th	Day	25% 12% 30% 21% 9% 4	487
	21st to end	Day	15% 10% 29% 24% 16% 5%	529
June	1st to 10th	Day	16% 12% 35% 24% 12% 2	490
	11th to 20th	Day	18% 10% 27% 26% 15% 4	490
	21st to end	Day	15% 10% 34% 23% 14% 4	490
July	1st to 10th	Day	13% 5% 25% 28% 20% 9%	485
	11th to 20th	Day	14% 5% 27% 28% 17% 9%	484
	21st to end	Day	11% 6% 28% 30% 16% 8%	532
August	1st to 10th	Day	14% 6% 21% 31% 19% 10%	486
	11th to 20th	Day	15% 7% 26% 25% 17% 9%	479
	21st to end	Day	11% 5% 23% 30% 23% 8%	539
September	1st to 10th	Day	14% 9% 21% 28% 19% 9%	490
	11th to 20th	Day	12% 4 19% 31% 23% 12%	490
	21st to end	Day	24% 10% 25% 20% 15% 5%	490
October	1st to 10th	Day	14% 13% 30% 21% 19% 4	490
	11th to 20th	Day	26% 17% 30% 18% 7% 3	490
	21st to end	Day	30% 17% 29% 19% 5%	539
November	1st to 10th	Day	21% 23% 30% 14% 10% 2	319
	11th to 20th	Day	30% 20% 30% 14% 5%	263
	21st to end	Day	30% 21% 38% 11% 1	200
December	1st to 10th	Day	31% 26% 28% 12% 3 2	200
	11th to 20th	Day	29% 27% 32% 11% 3	200
	21st to end	Day	34% 24% 30% 10% 2	243
January	1st to 10th	Night	27% 23% 34% 12% 3	800
	11th to 20th	Night	30% 24% 29% 15% 3	800
	21st to end	Night	26% 24% 30% 18% 3	880
February	1st to 10th	Night	30% 20% 29% 19% 2	781
	11th to 20th	Night	26% 22% 35% 16% 2	743
	21st to end	Night	30% 20% 31% 16% 3	628
March	1st to 10th	Night	25% 19% 32% 21% 4	760
	11th to 20th	Night	24% 20% 29% 21% 6% 1	760
	21st to end	Night	26% 15% 32% 21% 6%	836
April	1st to 10th	Night	24% 16% 32% 22% 5%	760
	11th to 20th	Night	22% 14% 35% 20% 8% 1	637
	21st to end	Night	18% 10% 37% 28% 6%	570
May	1st to 10th	Night	22% 9% 26% 33% 9% 1	570
	11th to 20th	Night	18% 7% 26% 34% 12% 2	561
	21st to end	Night	12% 3 26% 35% 22% 2	527
June	1st to 10th	Night	11% 3 34% 37% 13% 1	380
	11th to 20th	Night	12% 5% 23% 43% 16% 1	380
	21st to end	Night	12% 6% 29% 32% 20% 1	380
July	1st to 10th	Night	8% 3 17% 40% 28% 5%	499
	11th to 20th	Night	10% 3 20% 37% 27% 4	552
	21st to end	Night	10% 3 17% 41% 28% 2	624
August	1st to 10th	Night	9% 4 16% 40% 27% 4	567
	11th to 20th	Night	12% 4 15% 37% 29% 4	564
	21st to end	Night	10% 3 19% 34% 28% 5%	668
September	1st to 10th	Night	15% 6% 18% 31% 26% 4	760
	11th to 20th	Night	11% 4 15% 37% 28% 5%	760
	21st to end	Night	19% 8% 23% 28% 19% 4	760
October	1st to 10th	Night	19% 7% 26% 25% 20% 3	760
	11th to 20th	Night	22% 13% 30% 25% 10% 1	760
	21st to end	Night	28% 12% 29% 24% 6%	836
November	1st to 10th	Night	19% 14% 28% 28% 10% 1	780
	11th to 20th	Night	25% 21% 30% 18% 6% 1	800
	21st to end	Night	29% 19% 32% 15% 5%	800
December	1st to 10th	Night	32% 20% 28% 16% 5%	800
	11th to 20th	Night	28% 23% 28% 17% 4	800
	21st to end	Night	31% 19% 30% 19% 2	880

Page generated at 2025-02-03 03:05:51. Version ac07

Copyright © 2025 Attilla Danko.