Mahoning Valley Cortese Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mahoning Valley Cortese Observatory 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% 11% 4 9% 5% 5% 5% 4 5% 7% 29%	108511
	Night	16% 12% 5% 10% 5% 4 4 3 5% 6% 29%	109744
Transparency	Day	53% 6% 11% 19% 10% 1	112187
	Night	53% 5% 11% 19% 10% 1	114207
Seeing	Day	22% 15% 28% 20% 11% 4	14853
	Night	21% 13% 28% 25% 12% 1	24714

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	16% 21% 8% 24% 4 4 3 2 3 4 13%	4056
	11th to 20th	Day	12% 23% 8% 18% 8% 6% 4 2 3 3 11%	4060
	21st to end	Day	21% 21% 8% 13% 6% 5% 4 3 4 3 12%	4466
February	1st to 10th	Day	18% 19% 5% 13% 8% 4 4 2 3 4 21%	1755
	11th to 20th	Day	15% 15% 6% 14% 8% 5% 4 3 4 5% 20%	1682
	21st to end	Day	18% 17% 4 12% 4 4 4 4 4 5% 23%	1570
March	1st to 10th	Day	22% 12% 5% 9% 5% 3 4 3 4 6% 26%	3399
	11th to 20th	Day	12% 12% 5% 10% 5% 5% 5% 3 4 6% 33%	3480
	21st to end	Day	20% 12% 4 9% 5% 3 3 3 5% 6% 30%	3815
April	1st to 10th	Day	15% 14% 4 7% 5% 5% 4 4 5% 7% 31%	2153
	11th to 20th	Day	18% 11% 3 7% 5% 5% 5% 3 5% 6% 33%	2371
	21st to end	Day	20% 10% 3 8% 4 4 4 3 4 6% 34%	2470
May	1st to 10th	Day	20% 9% 4 8% 5% 5% 5% 4 5% 6% 29%	4082
	11th to 20th	Day	20% 9% 3 8% 4 4 5% 4 5% 7% 31%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	4657
June	1st to 10th	Day	14% 7% 3 7% 5% 6% 5% 5% 6% 7% 35%	2660
	11th to 20th	Day	13% 7% 3 7% 6% 5% 4 3 6% 9% 38%	2660
	21st to end	Day	12% 6% 2 6% 4 5% 6% 5% 7% 9% 39%	2660
July	1st to 10th	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 10% 39%	4226
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 10% 40%	4120
	21st to end	Day	10% 7% 3 7% 6% 6% 5% 5% 7% 8% 38%	4466
August	1st to 10th	Day	14% 7% 3 7% 5% 5% 6% 5% 7% 9% 32%	4104
	11th to 20th	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 10% 33%	4044
	21st to end	Day	8% 5% 3 7% 6% 6% 6% 4 6% 10% 39%	4411
September	1st to 10th	Day	14% 6% 3 6% 4 4 4 3 5% 8% 43%	2223
	11th to 20th	Day	11% 5% 3 6% 5% 4 4 3 6% 8% 43%	2090
	21st to end	Day	19% 9% 3 7% 4 3 5% 4 4 6% 37%	2090
October	1st to 10th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 7% 37%	1938
	11th to 20th	Day	22% 10% 3 7% 5% 4 4 3 5% 6% 32%	1900
	21st to end	Day	22% 10% 4 8% 4 5% 5% 3 6% 6% 27%	2090
November	1st to 10th	Day	12% 9% 3 8% 5% 4 5% 4 5% 6% 38%	1795
	11th to 20th	Day	18% 16% 4 7% 6% 4 4 3 5% 5% 27%	1715
	21st to end	Day	18% 17% 6% 11% 6% 5% 5% 3 6% 5% 19%	1600
December	1st to 10th	Day	19% 17% 8% 11% 6% 5% 5% 4 4 4 16%	2600
	11th to 20th	Day	24% 20% 6% 10% 6% 3 3 3 4 4 17%	2990
	21st to end	Day	26% 22% 6% 14% 6% 5% 3 3 3 3 9%	4032
January	1st to 10th	Night	15% 18% 10% 24% 5% 4 3 3 4 4 12%	5889
	11th to 20th	Night	12% 20% 10% 18% 9% 5% 6% 3 4 4 11%	5900
	21st to end	Night	22% 18% 8% 14% 6% 4 5% 2 3 4 15%	6490
February	1st to 10th	Night	20% 16% 4 11% 7% 4 4 3 5% 5% 20%	2536
	11th to 20th	Night	16% 14% 6% 12% 7% 5% 5% 3 4 5% 21%	2383
	21st to end	Night	21% 14% 4 12% 5% 4 4 3 4 5% 24%	1884
March	1st to 10th	Night	23% 14% 3 7% 4 4 3 3 4 5% 31%	3453
	11th to 20th	Night	17% 13% 4 8% 4 4 4 4 5% 6% 31%	3480
	21st to end	Night	19% 11% 3 8% 4 4 4 3 4 5% 34%	3817
April	1st to 10th	Night	16% 13% 4 8% 4 4 5% 3 6% 6% 31%	2026
	11th to 20th	Night	16% 10% 3 7% 4 4 5% 4 5% 7% 34%	1774
	21st to end	Night	15% 9% 2 6% 5% 5% 5% 4 6% 8% 36%	1710
May	1st to 10th	Night	25% 9% 3 7% 5% 4 5% 3 5% 6% 29%	2813
	11th to 20th	Night	16% 10% 3 6% 4 3 4 4 5% 8% 37%	2812
	21st to end	Night	10% 4 2 5% 4 4 4 4 7% 12% 45%	2898
June	1st to 10th	Night	9% 6% 2 7% 6% 4 5% 4 7% 7% 41%	1520
	11th to 20th	Night	9% 5% 2 7% 5% 4 4 4 6% 9% 43%	1520
	21st to end	Night	10% 6% 2 6% 4 5% 5% 5% 7% 9% 42%	1520
July	1st to 10th	Night	9% 6% 3 8% 5% 4 4 3 6% 8% 44%	2730
	11th to 20th	Night	9% 4 2 5% 4 4 5% 4 6% 9% 47%	2840
	21st to end	Night	8% 6% 2 7% 5% 5% 5% 4 6% 8% 45%	3087
August	1st to 10th	Night	11% 9% 4 7% 5% 4 4 3 6% 7% 39%	2825
	11th to 20th	Night	13% 8% 3 7% 4 5% 4 3 5% 6% 42%	2785
	21st to end	Night	8% 5% 2 6% 5% 5% 6% 5% 6% 8% 44%	3211
September	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 5% 8% 47%	1954
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 51%	2090
	21st to end	Night	16% 7% 3 6% 5% 5% 4 3 5% 6% 39%	2090
October	1st to 10th	Night	15% 5% 2 6% 4 3 4 5% 5% 8% 44%	2242
	11th to 20th	Night	19% 7% 2 8% 5% 4 5% 4 5% 7% 36%	2280
	21st to end	Night	22% 9% 3 7% 4 4 3 4 5% 6% 32%	2508
November	1st to 10th	Night	14% 9% 3 6% 5% 4 5% 4 5% 8% 39%	2503
	11th to 20th	Night	17% 16% 4 8% 5% 5% 4 3 4 6% 28%	2683
	21st to end	Night	19% 17% 4 8% 5% 5% 4 3 5% 6% 24%	2800
December	1st to 10th	Night	16% 19% 8% 12% 6% 5% 4 3 4 5% 17%	4580
	11th to 20th	Night	19% 21% 8% 11% 5% 4 3 2 4 4 18%	5205
	21st to end	Night	25% 19% 6% 11% 5% 4 4 3 4 5% 13%	6906

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	77% 4 8% 8% 3	4057
	11th to 20th	Day	79% 3 7% 8% 3	4060
	21st to end	Day	77% 3 6% 10% 3	4466
February	1st to 10th	Day	68% 4 9% 14% 6%	1755
	11th to 20th	Day	67% 4 7% 14% 7%	1691
	21st to end	Day	62% 5% 10% 16% 6% 2	1570
March	1st to 10th	Day	60% 5% 10% 21% 4	3399
	11th to 20th	Day	52% 6% 13% 21% 6% 1	3480
	21st to end	Day	55% 6% 9% 18% 12% 1	3815
April	1st to 10th	Day	52% 4 12% 17% 13% 1	2153
	11th to 20th	Day	52% 5% 11% 18% 13% 2	2371
	21st to end	Day	52% 5% 10% 21% 10% 2	2470
May	1st to 10th	Day	54% 6% 9% 22% 8% 1	4120
	11th to 20th	Day	50% 7% 11% 22% 9% 1	4085
	21st to end	Day	40% 7% 13% 21% 15% 5%	4671
June	1st to 10th	Day	45% 6% 12% 25% 12% 1	2660
	11th to 20th	Day	43% 5% 14% 22% 15% 1	2660
	21st to end	Day	40% 7% 13% 25% 15% 2	2660
July	1st to 10th	Day	39% 7% 12% 23% 15% 3	4161
	11th to 20th	Day	35% 6% 13% 26% 18% 1	4051
	21st to end	Day	41% 7% 13% 19% 18% 1	4324
August	1st to 10th	Day	46% 7% 14% 23% 11%	4091
	11th to 20th	Day	42% 7% 13% 29% 9% 1	4083
	21st to end	Day	37% 8% 13% 29% 11% 2	4411
September	1st to 10th	Day	40% 5% 13% 23% 16% 3	2223
	11th to 20th	Day	37% 6% 13% 25% 17% 1	2090
	21st to end	Day	48% 5% 10% 24% 12% 1	2090
October	1st to 10th	Day	34% 6% 13% 28% 19% 1	3224
	11th to 20th	Day	47% 6% 9% 21% 13% 4	3140
	21st to end	Day	42% 5% 13% 25% 14% 1	3428
November	1st to 10th	Day	45% 6% 12% 22% 14% 1	1795
	11th to 20th	Day	57% 6% 10% 18% 7% 3	1715
	21st to end	Day	65% 7% 9% 14% 6%	1600
December	1st to 10th	Day	69% 6% 11% 11% 2	2600
	11th to 20th	Day	72% 4 8% 13% 3	2986
	21st to end	Day	81% 3 8% 7% 2	4032
January	1st to 10th	Night	76% 5% 6% 9% 4	5889
	11th to 20th	Night	76% 5% 8% 8% 3	5900
	21st to end	Night	73% 3 8% 10% 5% 1	6490
February	1st to 10th	Night	66% 5% 9% 14% 5%	2536
	11th to 20th	Night	65% 5% 8% 16% 6%	2385
	21st to end	Night	63% 5% 8% 15% 9% 1	1884
March	1st to 10th	Night	55% 4 11% 21% 9%	3453
	11th to 20th	Night	50% 8% 16% 17% 8% 1	3480
	21st to end	Night	50% 7% 8% 22% 12% 1	3817
April	1st to 10th	Night	52% 7% 10% 17% 12% 2	2026
	11th to 20th	Night	48% 5% 13% 18% 14% 2	1774
	21st to end	Night	45% 6% 12% 21% 14% 3	1710
May	1st to 10th	Night	55% 5% 9% 20% 9% 2	2840
	11th to 20th	Night	44% 7% 12% 24% 11% 2	2813
	21st to end	Night	31% 7% 15% 27% 17% 3	2905
June	1st to 10th	Night	40% 7% 10% 25% 15% 2	1520
	11th to 20th	Night	37% 7% 14% 23% 17% 3	1520
	21st to end	Night	36% 7% 13% 25% 17% 1	1520
July	1st to 10th	Night	38% 5% 12% 23% 18% 3	2685
	11th to 20th	Night	32% 7% 12% 29% 18% 1	2786
	21st to end	Night	36% 7% 14% 18% 24% 2	2988
August	1st to 10th	Night	44% 6% 12% 24% 14% 1	2814
	11th to 20th	Night	41% 6% 11% 29% 12% 1	2812
	21st to end	Night	35% 8% 13% 28% 15% 2	3211
September	1st to 10th	Night	36% 5% 12% 27% 17% 4	1954
	11th to 20th	Night	31% 6% 13% 27% 22% 2	2090
	21st to end	Night	44% 5% 12% 22% 17% 1	2090
October	1st to 10th	Night	34% 5% 9% 28% 23% 1	3736
	11th to 20th	Night	42% 6% 11% 23% 16% 3	3779
	21st to end	Night	38% 4 12% 29% 16% 1	4120
November	1st to 10th	Night	42% 6% 11% 24% 14% 3	2503
	11th to 20th	Night	57% 4 9% 18% 8% 3	2683
	21st to end	Night	61% 5% 11% 17% 5% 1	2800
December	1st to 10th	Night	67% 5% 13% 11% 3	4580
	11th to 20th	Night	70% 4 10% 14% 2	5208
	21st to end	Night	74% 5% 10% 10% 1	6906

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% 27% 28% 9% 4	300
	11th to 20th	Day	34% 27% 29% 8% 2	300
	21st to end	Day	31% 31% 28% 8% 2	330
February	1st to 10th	Day	32% 24% 34% 8% 1	285
	11th to 20th	Day	31% 33% 30% 5% 1	270
	21st to end	Day	33% 31% 30% 6%	225
March	1st to 10th	Day	26% 23% 33% 13% 6%	435
	11th to 20th	Day	27% 21% 34% 12% 6% 1	460
	21st to end	Day	34% 20% 27% 15% 4	506
April	1st to 10th	Day	25% 23% 29% 15% 7% 1	460
	11th to 20th	Day	29% 16% 29% 15% 9% 2	452
	21st to end	Day	27% 18% 30% 18% 4 2	460
May	1st to 10th	Day	30% 17% 27% 17% 6% 3	463
	11th to 20th	Day	24% 12% 31% 20% 8% 5%	487
	21st to end	Day	16% 10% 29% 24% 16% 5%	529
June	1st to 10th	Day	17% 11% 34% 24% 11% 3	490
	11th to 20th	Day	18% 10% 26% 27% 14% 5%	490
	21st to end	Day	16% 9% 33% 24% 14% 4	490
July	1st to 10th	Day	12% 6% 23% 28% 21% 9%	485
	11th to 20th	Day	14% 5% 27% 28% 17% 9%	484
	21st to end	Day	12% 6% 27% 29% 17% 8%	532
August	1st to 10th	Day	13% 8% 21% 29% 19% 10%	486
	11th to 20th	Day	16% 7% 25% 24% 18% 9%	479
	21st to end	Day	10% 6% 22% 30% 23% 9%	539
September	1st to 10th	Day	13% 10% 22% 27% 20% 9%	490
	11th to 20th	Day	12% 4 19% 31% 23% 11%	490
	21st to end	Day	25% 10% 25% 20% 14% 6%	490
October	1st to 10th	Day	14% 11% 29% 22% 19% 4	490
	11th to 20th	Day	25% 17% 30% 17% 8% 3	490
	21st to end	Day	29% 18% 28% 19% 6%	539
November	1st to 10th	Day	20% 23% 29% 16% 10% 2	333
	11th to 20th	Day	32% 19% 29% 15% 5%	257
	21st to end	Day	31% 19% 40% 10% 1	200
December	1st to 10th	Day	31% 25% 29% 12% 3 2	200
	11th to 20th	Day	29% 27% 33% 10% 2	200
	21st to end	Day	33% 24% 31% 10% 2	237
January	1st to 10th	Night	27% 22% 36% 12% 4	800
	11th to 20th	Night	30% 22% 31% 14% 3	800
	21st to end	Night	25% 23% 30% 18% 3	880
February	1st to 10th	Night	30% 19% 29% 20% 2	781
	11th to 20th	Night	26% 19% 36% 16% 2	743
	21st to end	Night	30% 17% 34% 16% 3	628
March	1st to 10th	Night	24% 17% 33% 22% 4	760
	11th to 20th	Night	25% 18% 29% 22% 6% 1	760
	21st to end	Night	25% 14% 32% 22% 6% 1	836
April	1st to 10th	Night	25% 14% 33% 22% 6%	760
	11th to 20th	Night	22% 13% 35% 22% 8% 1	650
	21st to end	Night	18% 10% 38% 28% 7%	570
May	1st to 10th	Night	21% 9% 27% 34% 9% 1	570
	11th to 20th	Night	17% 7% 27% 33% 13% 2	561
	21st to end	Night	12% 4 26% 34% 22% 3	513
June	1st to 10th	Night	10% 4 34% 38% 13% 1	380
	11th to 20th	Night	12% 5% 23% 43% 16% 1	380
	21st to end	Night	12% 6% 27% 34% 20% 1	380
July	1st to 10th	Night	8% 2 17% 40% 27% 5%	484
	11th to 20th	Night	9% 3 21% 37% 27% 3	552
	21st to end	Night	10% 3 17% 41% 27% 2	624
August	1st to 10th	Night	10% 3 16% 41% 27% 3	567
	11th to 20th	Night	13% 4 14% 36% 28% 4	564
	21st to end	Night	12% 2 19% 34% 30% 4	675
September	1st to 10th	Night	15% 5% 19% 31% 26% 4	760
	11th to 20th	Night	11% 4 15% 38% 28% 5%	760
	21st to end	Night	19% 8% 22% 28% 19% 4	760
October	1st to 10th	Night	19% 8% 25% 26% 20% 3	760
	11th to 20th	Night	22% 12% 31% 24% 10% 2	760
	21st to end	Night	29% 12% 28% 24% 7%	836
November	1st to 10th	Night	19% 13% 28% 27% 11% 1	780
	11th to 20th	Night	26% 19% 30% 18% 6% 1	800
	21st to end	Night	29% 19% 31% 17% 5%	800
December	1st to 10th	Night	31% 19% 30% 16% 5%	800
	11th to 20th	Night	27% 23% 28% 18% 4	800
	21st to end	Night	30% 17% 31% 20% 2	880

Page generated at 2025-02-03 03:05:52. Version ac07

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