Morgan County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morgan County Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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% 7% 2 6% 5% 5% 5% 4 6% 8% 39%	101376
	Night	14% 7% 2 6% 4 4 4 4 6% 7% 40%	98054
Transparency	Day	22% 47% 7% 14% 8% 1	105018
	Night	22% 47% 7% 14% 9% 1	102551
Seeing	Day	22% 13% 25% 21% 13% 5%	14946
	Night	20% 12% 25% 30% 13% 1	24534

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% 7% 2 7% 5% 5% 4 4 5% 6% 38%	2681
	11th to 20th	Day	12% 11% 4 10% 6% 6% 5% 4 6% 6% 31%	2840
	21st to end	Day	16% 9% 4 9% 6% 5% 4 3 5% 6% 32%	3124
February	1st to 10th	Day	14% 10% 4 8% 5% 4 4 3 5% 6% 36%	1710
	11th to 20th	Day	14% 9% 2 6% 7% 5% 4 4 5% 6% 37%	1663
	21st to end	Day	15% 9% 4 8% 5% 4 4 3 5% 5% 37%	1581
March	1st to 10th	Day	20% 10% 3 7% 4 4 5% 4 4 7% 33%	3435
	11th to 20th	Day	10% 7% 2 6% 4 5% 4 4 5% 8% 45%	3480
	21st to end	Day	16% 9% 3 6% 5% 4 4 4 6% 6% 38%	3815
April	1st to 10th	Day	12% 9% 2 7% 6% 5% 5% 3 6% 8% 37%	2270
	11th to 20th	Day	13% 7% 2 5% 5% 4 5% 4 5% 7% 42%	2254
	21st to end	Day	19% 6% 2 6% 4 4 5% 3 5% 5% 39%	2333
May	1st to 10th	Day	22% 8% 3 8% 5% 4 4 4 5% 7% 29%	4082
	11th to 20th	Day	24% 7% 2 6% 5% 4 5% 4 5% 7% 31%	4176
	21st to end	Day	10% 5% 2 6% 4 5% 5% 4 6% 10% 42%	4823
June	1st to 10th	Day	13% 6% 1 5% 4 4 5% 5% 7% 10% 41%	2660
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 4 7% 10% 38%	2660
	21st to end	Day	10% 4 2 5% 5% 5% 5% 4 7% 11% 42%	2660
July	1st to 10th	Day	5% 4 1 6% 5% 5% 6% 5% 8% 10% 44%	4440
	11th to 20th	Day	8% 4 2 6% 5% 5% 5% 4 8% 11% 42%	4187
	21st to end	Day	11% 8% 3 7% 5% 5% 5% 4 6% 8% 38%	4466
August	1st to 10th	Day	17% 5% 2 6% 5% 5% 6% 5% 7% 9% 34%	4104
	11th to 20th	Day	9% 5% 2 7% 4 5% 6% 5% 8% 9% 42%	3986
	21st to end	Day	12% 4 2 5% 4 4 5% 4 6% 7% 48%	4180
September	1st to 10th	Day	16% 6% 2 5% 3 4 4 4 5% 7% 45%	2280
	11th to 20th	Day	12% 5% 2 6% 4 3 4 3 5% 8% 47%	2235
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 6% 38%	2007
October	1st to 10th	Day	16% 6% 2 5% 3 4 4 3 5% 7% 46%	1900
	11th to 20th	Day	16% 5% 1 5% 3 4 4 4 5% 7% 45%	1900
	21st to end	Day	14% 6% 2 5% 4 4 3 4 5% 6% 47%	2090
November	1st to 10th	Day	11% 6% 2 4 4 3 4 3 5% 7% 52%	1915
	11th to 20th	Day	15% 6% 2 5% 4 3 4 4 6% 7% 44%	1685
	21st to end	Day	16% 6% 2 5% 5% 5% 4 4 6% 8% 40%	1552
December	1st to 10th	Day	17% 8% 2 7% 5% 4 5% 5% 7% 6% 32%	1520
	11th to 20th	Day	15% 6% 2 8% 5% 6% 4 4 6% 6% 38%	1910
	21st to end	Day	17% 6% 2 7% 6% 6% 6% 5% 8% 7% 29%	2772
January	1st to 10th	Night	11% 8% 3 7% 5% 5% 5% 4 6% 8% 38%	4263
	11th to 20th	Night	16% 9% 3 7% 4 4 4 4 5% 6% 38%	4120
	21st to end	Night	17% 10% 4 8% 5% 4 4 4 5% 6% 33%	4532
February	1st to 10th	Night	14% 8% 3 6% 5% 4 4 3 6% 7% 39%	2470
	11th to 20th	Night	15% 9% 3 6% 5% 5% 5% 4 6% 6% 36%	2403
	21st to end	Night	16% 10% 3 7% 5% 4 5% 3 5% 7% 36%	1871
March	1st to 10th	Night	20% 9% 2 6% 4 4 4 3 4 5% 38%	3418
	11th to 20th	Night	10% 5% 2 6% 5% 5% 4 4 6% 6% 46%	3480
	21st to end	Night	12% 8% 3 6% 4 4 4 3 5% 6% 47%	3817
April	1st to 10th	Night	16% 8% 3 5% 5% 5% 4 5% 5% 6% 38%	1910
	11th to 20th	Night	13% 6% 3 6% 5% 3 4 4 6% 8% 42%	1875
	21st to end	Night	17% 5% 2 5% 3 4 4 3 6% 7% 42%	1862
May	1st to 10th	Night	24% 7% 3 7% 5% 4 5% 4 5% 8% 29%	2813
	11th to 20th	Night	25% 8% 2 5% 4 4 4 3 4 6% 33%	2717
	21st to end	Night	11% 5% 2 6% 4 4 5% 5% 7% 10% 41%	2732
June	1st to 10th	Night	11% 4 2 5% 3 5% 4 5% 7% 8% 46%	1520
	11th to 20th	Night	11% 5% 3 6% 5% 4 6% 4 6% 10% 41%	1520
	21st to end	Night	9% 4 2 5% 4 4 4 5% 7% 12% 43%	1520
July	1st to 10th	Night	7% 4 2 6% 5% 6% 6% 5% 7% 10% 43%	2520
	11th to 20th	Night	6% 4 2 8% 5% 6% 5% 6% 8% 10% 40%	2768
	21st to end	Night	10% 6% 2 6% 5% 6% 6% 5% 7% 8% 38%	3087
August	1st to 10th	Night	16% 5% 2 7% 5% 5% 6% 4 7% 9% 34%	2825
	11th to 20th	Night	10% 5% 2 6% 4 5% 4 5% 7% 8% 44%	2809
	21st to end	Night	14% 4 1 4 4 4 4 4 6% 8% 46%	3476
September	1st to 10th	Night	15% 5% 2 5% 4 4 4 4 5% 7% 46%	1900
	11th to 20th	Night	11% 7% 3 6% 3 4 2 3 4 8% 51%	1942
	21st to end	Night	22% 5% 2 5% 4 5% 4 3 4 6% 41%	2172
October	1st to 10th	Night	19% 6% 2 4 3 3 3 3 4 6% 45%	2280
	11th to 20th	Night	14% 4 1 5% 3 4 4 3 5% 6% 50%	2280
	21st to end	Night	15% 4 2 4 3 3 3 3 5% 6% 50%	2508
November	1st to 10th	Night	10% 6% 1 5% 4 3 4 3 5% 6% 52%	2381
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 4 7% 45%	2711
	21st to end	Night	13% 6% 2 6% 5% 4 5% 4 6% 7% 42%	2723
December	1st to 10th	Night	16% 7% 3 7% 5% 5% 4 4 5% 7% 37%	2660
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 4 6% 7% 39%	3285
	21st to end	Night	17% 7% 2 6% 5% 6% 6% 4 7% 9% 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	30% 37% 7% 16% 7% 3	2682
	11th to 20th	Day	35% 38% 6% 9% 10% 3	2840
	21st to end	Day	34% 41% 5% 14% 5% 1	3124
February	1st to 10th	Day	19% 65% 5% 7% 4 1	1710
	11th to 20th	Day	16% 64% 4 8% 6% 1	1672
	21st to end	Day	18% 65% 4 8% 5% 1	1581
March	1st to 10th	Day	37% 42% 5% 10% 5% 1	3435
	11th to 20th	Day	18% 42% 5% 21% 13% 1	3480
	21st to end	Day	26% 42% 8% 13% 9% 2	3815
April	1st to 10th	Day	19% 65% 4 5% 6% 1	2270
	11th to 20th	Day	13% 66% 4 10% 6% 1	2254
	21st to end	Day	17% 65% 4 9% 5%	2333
May	1st to 10th	Day	35% 42% 5% 13% 5%	4120
	11th to 20th	Day	32% 43% 6% 16% 2	4180
	21st to end	Day	19% 43% 9% 16% 11% 2	4837
June	1st to 10th	Day	15% 66% 4 10% 6%	2660
	11th to 20th	Day	13% 67% 4 9% 6%	2660
	21st to end	Day	13% 65% 6% 10% 6%	2660
July	1st to 10th	Day	21% 40% 11% 18% 7% 3	4370
	11th to 20th	Day	22% 39% 11% 21% 8%	4115
	21st to end	Day	29% 37% 6% 16% 12% 1	4324
August	1st to 10th	Day	31% 40% 9% 16% 4	4091
	11th to 20th	Day	22% 40% 9% 21% 9%	4025
	21st to end	Day	21% 39% 9% 19% 12%	4180
September	1st to 10th	Day	15% 61% 6% 9% 8% 1	2280
	11th to 20th	Day	14% 60% 4 12% 9% 1	2235
	21st to end	Day	21% 60% 5% 8% 5%	2007
October	1st to 10th	Day	22% 37% 5% 14% 19% 3	3160
	11th to 20th	Day	14% 38% 8% 19% 14% 7%	3140
	21st to end	Day	12% 36% 9% 21% 20% 2	3428
November	1st to 10th	Day	17% 56% 6% 10% 9% 2	1915
	11th to 20th	Day	13% 56% 6% 11% 12% 1	1685
	21st to end	Day	17% 59% 6% 13% 4 1	1552
December	1st to 10th	Day	22% 60% 7% 6% 5%	1520
	11th to 20th	Day	22% 48% 6% 17% 4 2	1906
	21st to end	Day	31% 42% 10% 10% 6%	2772
January	1st to 10th	Night	28% 38% 7% 17% 9% 2	4263
	11th to 20th	Night	28% 38% 9% 16% 8% 2	4120
	21st to end	Night	33% 41% 6% 14% 5% 1	4532
February	1st to 10th	Night	15% 65% 6% 10% 3 1	2470
	11th to 20th	Night	17% 63% 3 8% 7% 1	2405
	21st to end	Night	17% 65% 5% 7% 4 3	1871
March	1st to 10th	Night	34% 43% 5% 15% 3	3418
	11th to 20th	Night	19% 41% 7% 23% 9% 1	3480
	21st to end	Night	22% 41% 6% 16% 14% 2	3817
April	1st to 10th	Night	16% 65% 5% 9% 5%	1910
	11th to 20th	Night	14% 66% 5% 9% 5% 1	1875
	21st to end	Night	14% 66% 4 10% 5% 1	1862
May	1st to 10th	Night	37% 41% 5% 9% 7% 1	2840
	11th to 20th	Night	33% 43% 6% 14% 3	2718
	21st to end	Night	22% 44% 10% 17% 5% 2	2739
June	1st to 10th	Night	14% 66% 4 9% 7%	1520
	11th to 20th	Night	14% 66% 4 11% 5%	1520
	21st to end	Night	12% 65% 6% 10% 7%	1520
July	1st to 10th	Night	23% 39% 15% 11% 8% 4	2480
	11th to 20th	Night	25% 39% 11% 16% 9%	2717
	21st to end	Night	30% 37% 7% 13% 11% 1	2988
August	1st to 10th	Night	32% 40% 11% 13% 3	2814
	11th to 20th	Night	23% 40% 8% 19% 10%	2836
	21st to end	Night	21% 38% 9% 22% 10%	3476
September	1st to 10th	Night	15% 61% 6% 10% 7% 1	1900
	11th to 20th	Night	15% 59% 4 12% 9% 1	1942
	21st to end	Night	22% 60% 3 10% 5%	2172
October	1st to 10th	Night	23% 37% 6% 16% 16% 2	3800
	11th to 20th	Night	13% 37% 7% 15% 22% 6%	3779
	21st to end	Night	12% 36% 8% 22% 18% 4	4120
November	1st to 10th	Night	16% 56% 7% 11% 8% 2	2381
	11th to 20th	Night	16% 56% 3 11% 11% 3	2711
	21st to end	Night	16% 59% 6% 11% 7% 1	2723
December	1st to 10th	Night	20% 60% 6% 9% 4	2660
	11th to 20th	Night	22% 49% 6% 13% 9% 2	3288
	21st to end	Night	30% 41% 11% 11% 7%	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	40% 21% 26% 9% 4	227
	11th to 20th	Day	36% 22% 27% 13% 2	270
	21st to end	Day	32% 28% 25% 11% 4	297
February	1st to 10th	Day	33% 23% 30% 11% 3	270
	11th to 20th	Day	41% 23% 29% 6%	270
	21st to end	Day	35% 19% 26% 17% 3	367
March	1st to 10th	Day	32% 21% 24% 18% 4	460
	11th to 20th	Day	30% 24% 25% 15% 5% 2	460
	21st to end	Day	28% 21% 29% 15% 5% 2	506
April	1st to 10th	Day	27% 23% 24% 18% 7% 1	460
	11th to 20th	Day	21% 18% 29% 17% 10% 5%	452
	21st to end	Day	33% 14% 26% 17% 8% 2	460
May	1st to 10th	Day	28% 14% 29% 15% 10% 4	463
	11th to 20th	Day	25% 15% 26% 17% 12% 4	487
	21st to end	Day	18% 10% 24% 22% 17% 8%	529
June	1st to 10th	Day	17% 10% 30% 20% 18% 6%	490
	11th to 20th	Day	14% 9% 30% 25% 17% 5%	490
	21st to end	Day	13% 10% 28% 28% 15% 7%	490
July	1st to 10th	Day	13% 5% 21% 29% 21% 12%	485
	11th to 20th	Day	6% 4 25% 29% 24% 12%	484
	21st to end	Day	16% 5% 19% 33% 19% 8%	532
August	1st to 10th	Day	16% 5% 20% 25% 22% 12%	486
	11th to 20th	Day	13% 3 22% 30% 22% 10%	479
	21st to end	Day	11% 4 22% 27% 25% 12%	539
September	1st to 10th	Day	19% 8% 18% 22% 22% 11%	490
	11th to 20th	Day	16% 4 17% 28% 25% 9%	490
	21st to end	Day	29% 9% 22% 21% 16% 4	490
October	1st to 10th	Day	23% 6% 20% 29% 18% 5%	490
	11th to 20th	Day	21% 13% 24% 25% 15% 3	490
	21st to end	Day	20% 14% 30% 22% 12% 2	539
November	1st to 10th	Day	20% 11% 29% 24% 13% 4	473
	11th to 20th	Day	24% 16% 29% 21% 8% 1	285
	21st to end	Day	27% 19% 29% 17% 7% 1	188
December	1st to 10th	Day	32% 20% 28% 15% 5% 1	180
	11th to 20th	Day	29% 21% 24% 21% 5%	180
	21st to end	Day	27% 18% 28% 17% 10%	198
January	1st to 10th	Night	21% 21% 33% 22% 4	760
	11th to 20th	Night	26% 15% 30% 26% 3	760
	21st to end	Night	23% 22% 31% 23% 2	836
February	1st to 10th	Night	22% 19% 29% 27% 3	760
	11th to 20th	Night	27% 25% 29% 17% 2	743
	21st to end	Night	29% 18% 31% 20% 3	628
March	1st to 10th	Night	24% 17% 33% 22% 4	760
	11th to 20th	Night	27% 19% 26% 21% 5%	760
	21st to end	Night	21% 16% 35% 21% 5% 1	836
April	1st to 10th	Night	25% 18% 30% 21% 6%	760
	11th to 20th	Night	19% 13% 32% 27% 9% 1	751
	21st to end	Night	22% 13% 26% 32% 7%	722
May	1st to 10th	Night	24% 6% 23% 31% 14% 2	570
	11th to 20th	Night	23% 7% 24% 32% 13%	505
	21st to end	Night	16% 5% 20% 36% 21% 2	411
June	1st to 10th	Night	11% 4 26% 33% 26%	380
	11th to 20th	Night	12% 6% 19% 40% 22% 2	380
	21st to end	Night	9% 2 24% 43% 21% 1	380
July	1st to 10th	Night	12% 4 14% 36% 31% 3	370
	11th to 20th	Night	7% 3 10% 41% 34% 5%	509
	21st to end	Night	11% 1 16% 39% 30% 3	624
August	1st to 10th	Night	12% 2 13% 40% 29% 3	567
	11th to 20th	Night	11% 2 11% 40% 30% 5%	575
	21st to end	Night	14% 3 14% 37% 30% 4	836
September	1st to 10th	Night	18% 3 15% 33% 27% 4	760
	11th to 20th	Night	14% 4 16% 33% 28% 4	760
	21st to end	Night	23% 6% 18% 31% 20% 3	760
October	1st to 10th	Night	23% 7% 18% 30% 21% 3	760
	11th to 20th	Night	17% 11% 24% 34% 13% 1	760
	21st to end	Night	20% 12% 26% 31% 11%	836
November	1st to 10th	Night	15% 10% 30% 33% 12% 1	780
	11th to 20th	Night	21% 17% 24% 29% 8% 1	800
	21st to end	Night	20% 16% 27% 30% 6%	779
December	1st to 10th	Night	23% 17% 29% 24% 7%	760
	11th to 20th	Night	22% 14% 31% 30% 4	760
	21st to end	Night	20% 17% 26% 34% 3	836

Page generated at 2024-11-22 08:02:26. Version ac07

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