Michowka Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Michowka Observatory clear sky chart from 2005-11-06 to 2025-12-03.

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	13% 8% 3 8% 5% 4 4 4 5% 7% 38%	127464
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 37%	123495
Transparency	Day	44% 6% 12% 25% 12% 1	130937
	Night	45% 6% 12% 23% 13% 1	128095
Seeing	Day	16% 12% 29% 25% 13% 4	17457
	Night	17% 10% 31% 30% 10% 1	27320

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	7% 13% 7% 18% 7% 6% 4 3 4 5% 28%	3617
	11th to 20th	Day	7% 12% 7% 11% 5% 5% 8% 8% 6% 7% 23%	3620
	21st to end	Day	11% 15% 6% 11% 5% 4 4 3 4 5% 34%	4181
February	1st to 10th	Day	9% 13% 5% 10% 5% 5% 5% 4 5% 8% 31%	1800
	11th to 20th	Day	11% 11% 4 7% 6% 5% 5% 5% 5% 6% 36%	1816
	21st to end	Day	12% 12% 4 10% 6% 5% 4 4 5% 7% 31%	1650
March	1st to 10th	Day	13% 8% 2 5% 3 3 3 3 4 6% 48%	4480
	11th to 20th	Day	11% 7% 3 7% 4 4 4 4 6% 7% 43%	4906
	21st to end	Day	23% 11% 4 9% 4 4 4 3 4 6% 29%	5825
April	1st to 10th	Day	17% 12% 4 8% 5% 5% 5% 3 5% 5% 31%	2400
	11th to 20th	Day	21% 10% 3 9% 5% 4 3 3 4 5% 33%	2374
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 5% 5% 32%	2460
May	1st to 10th	Day	14% 7% 2 6% 4 4 4 3 5% 6% 45%	6291
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 6% 7% 42%	6319
	21st to end	Day	18% 7% 2 6% 4 5% 5% 4 5% 6% 38%	6935
June	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 6% 8% 43%	2800
	11th to 20th	Day	15% 6% 2 6% 5% 5% 5% 4 6% 7% 40%	2800
	21st to end	Day	14% 5% 2 6% 4 4 4 5% 7% 8% 39%	2800
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	6360
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 8% 9% 49%	6360
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 4 7% 8% 42%	6924
August	1st to 10th	Day	11% 5% 3 7% 5% 5% 5% 5% 6% 8% 40%	4484
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 5% 8% 46%	4049
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 5% 8% 43%	4312
September	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 5% 7% 45%	2400
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 3 5% 8% 46%	2370
	21st to end	Day	14% 6% 2 6% 5% 4 4 4 5% 8% 42%	2182
October	1st to 10th	Day	14% 7% 1 6% 4 4 4 4 5% 6% 45%	2000
	11th to 20th	Day	19% 10% 3 7% 4 4 4 4 5% 7% 34%	2000
	21st to end	Day	18% 10% 3 8% 4 4 3 2 4 6% 38%	2027
November	1st to 10th	Day	14% 8% 3 6% 5% 4 4 4 5% 6% 41%	1852
	11th to 20th	Day	14% 12% 4 11% 6% 4 5% 3 5% 6% 30%	1774
	21st to end	Day	15% 11% 3 7% 6% 4 5% 3 4 6% 35%	1680
December	1st to 10th	Day	8% 9% 7% 12% 7% 7% 6% 4 5% 6% 27%	2626
	11th to 20th	Day	12% 18% 6% 10% 7% 4 3 3 4 5% 28%	3008
	21st to end	Day	21% 19% 7% 14% 5% 4 4 3 3 4 15%	3982
January	1st to 10th	Night	8% 12% 7% 13% 8% 4 3 3 4 5% 34%	6348
	11th to 20th	Night	9% 13% 6% 13% 6% 6% 8% 5% 6% 5% 22%	6360
	21st to end	Night	10% 15% 8% 12% 6% 4 4 3 5% 6% 28%	6794
February	1st to 10th	Night	9% 14% 5% 10% 6% 5% 5% 3 5% 5% 34%	2600
	11th to 20th	Night	10% 10% 4 8% 5% 5% 4 4 6% 6% 40%	2469
	21st to end	Night	15% 12% 3 7% 6% 5% 4 4 5% 6% 34%	1980
March	1st to 10th	Night	12% 8% 2 7% 4 4 4 3 5% 6% 45%	5373
	11th to 20th	Night	10% 8% 3 8% 5% 5% 5% 4 5% 8% 40%	5085
	21st to end	Night	23% 12% 3 9% 5% 3 3 2 4 5% 30%	5103
April	1st to 10th	Night	19% 11% 3 7% 4 4 4 3 5% 6% 34%	2000
	11th to 20th	Night	21% 9% 3 6% 5% 3 3 3 5% 5% 36%	1975
	21st to end	Night	18% 9% 2 6% 5% 4 3 3 6% 8% 37%	1940
May	1st to 10th	Night	15% 7% 3 7% 4 4 4 3 5% 6% 42%	3609
	11th to 20th	Night	11% 5% 2 6% 4 3 4 3 6% 7% 49%	3596
	21st to end	Night	16% 8% 3 7% 4 4 4 3 5% 7% 37%	3942
June	1st to 10th	Night	11% 4 2 7% 4 4 4 3 6% 8% 46%	1600
	11th to 20th	Night	13% 6% 2 7% 5% 5% 4 3 5% 9% 41%	1600
	21st to end	Night	10% 5% 2 5% 5% 4 4 4 6% 8% 47%	1600
July	1st to 10th	Night	12% 5% 2 5% 4 4 5% 4 6% 8% 43%	3618
	11th to 20th	Night	8% 4 2 5% 4 3 3 4 5% 8% 53%	3617
	21st to end	Night	6% 5% 2 6% 5% 4 5% 4 6% 9% 49%	3947
August	1st to 10th	Night	10% 5% 2 6% 4 5% 4 4 5% 8% 47%	2660
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 46%	3005
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 5% 7% 49%	3586
September	1st to 10th	Night	11% 5% 1 5% 4 4 4 3 6% 6% 51%	2000
	11th to 20th	Night	12% 4 2 5% 4 3 3 3 5% 8% 51%	2010
	21st to end	Night	13% 5% 2 5% 3 4 4 3 5% 6% 50%	2215
October	1st to 10th	Night	12% 6% 2 6% 4 4 3 3 4 7% 50%	2400
	11th to 20th	Night	17% 7% 2 6% 4 4 4 4 6% 7% 40%	2400
	21st to end	Night	17% 10% 2 8% 4 4 5% 4 5% 6% 35%	2811
November	1st to 10th	Night	15% 10% 3 6% 4 3 3 3 5% 7% 41%	2666
	11th to 20th	Night	13% 12% 5% 9% 6% 4 5% 3 5% 5% 33%	2842
	21st to end	Night	16% 11% 3 9% 5% 4 4 3 4 6% 35%	2940
December	1st to 10th	Night	8% 9% 4 9% 6% 5% 5% 4 7% 8% 34%	4609
	11th to 20th	Night	14% 18% 7% 12% 6% 4 4 3 4 4 24%	5199
	21st to end	Night	21% 17% 6% 12% 5% 3 3 3 4 5% 20%	6996

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	60% 4 11% 18% 7%	3618
	11th to 20th	Day	56% 7% 9% 15% 13%	3620
	21st to end	Day	54% 5% 13% 19% 10%	4181
February	1st to 10th	Day	51% 6% 13% 18% 10% 1	1800
	11th to 20th	Day	47% 6% 13% 24% 9% 2	1825
	21st to end	Day	53% 5% 11% 20% 9% 2	1650
March	1st to 10th	Day	38% 3 12% 27% 16% 5%	4480
	11th to 20th	Day	39% 5% 15% 25% 14% 2	4906
	21st to end	Day	57% 5% 9% 16% 12% 1	5827
April	1st to 10th	Day	53% 6% 10% 19% 11% 1	2400
	11th to 20th	Day	52% 5% 8% 21% 12% 2	2374
	21st to end	Day	52% 7% 11% 19% 11% 1	2460
May	1st to 10th	Day	38% 6% 11% 28% 16% 2	6329
	11th to 20th	Day	39% 7% 12% 26% 15% 1	6323
	21st to end	Day	44% 6% 10% 25% 13% 1	6949
June	1st to 10th	Day	37% 7% 13% 27% 15% 1	2800
	11th to 20th	Day	42% 6% 13% 24% 14% 1	2800
	21st to end	Day	40% 8% 15% 24% 12% 2	2800
July	1st to 10th	Day	34% 8% 16% 34% 6% 1	6291
	11th to 20th	Day	28% 8% 15% 34% 14% 1	6285
	21st to end	Day	37% 8% 13% 24% 17% 1	6728
August	1st to 10th	Day	39% 8% 14% 26% 13% 1	4469
	11th to 20th	Day	36% 6% 12% 33% 13%	4088
	21st to end	Day	37% 6% 14% 29% 12% 1	4311
September	1st to 10th	Day	37% 6% 13% 28% 15%	2400
	11th to 20th	Day	35% 7% 15% 33% 9% 1	2370
	21st to end	Day	39% 6% 13% 28% 13% 1	2182
October	1st to 10th	Day	25% 5% 7% 41% 22% 1	3260
	11th to 20th	Day	40% 5% 11% 26% 16% 2	3240
	21st to end	Day	43% 3 13% 30% 10%	3252
November	1st to 10th	Day	42% 7% 13% 22% 15% 1	1852
	11th to 20th	Day	55% 4 12% 20% 9% 1	1774
	21st to end	Day	50% 5% 16% 21% 7% 1	1680
December	1st to 10th	Day	56% 8% 13% 18% 6%	2626
	11th to 20th	Day	59% 3 11% 17% 8% 1	3005
	21st to end	Day	73% 4 7% 10% 5%	3982
January	1st to 10th	Night	53% 4 9% 22% 10%	6348
	11th to 20th	Night	61% 5% 9% 11% 14%	6360
	21st to end	Night	57% 5% 11% 16% 11%	6794
February	1st to 10th	Night	52% 5% 11% 21% 10% 2	2600
	11th to 20th	Night	44% 5% 12% 27% 10% 2	2470
	21st to end	Night	51% 5% 13% 20% 10% 2	1980
March	1st to 10th	Night	40% 5% 14% 25% 11% 6%	5373
	11th to 20th	Night	42% 5% 14% 24% 13% 3	5085
	21st to end	Night	57% 4 10% 17% 11% 1	5103
April	1st to 10th	Night	51% 5% 9% 17% 16% 2	2000
	11th to 20th	Night	48% 5% 9% 20% 14% 3	1975
	21st to end	Night	44% 7% 12% 21% 14% 2	1940
May	1st to 10th	Night	42% 6% 11% 19% 19% 3	3633
	11th to 20th	Night	33% 8% 13% 24% 19% 2	3597
	21st to end	Night	45% 7% 10% 24% 13% 1	3950
June	1st to 10th	Night	33% 8% 14% 27% 17% 1	1600
	11th to 20th	Night	40% 7% 13% 22% 17% 2	1600
	21st to end	Night	34% 8% 13% 29% 13% 4	1600
July	1st to 10th	Night	36% 7% 16% 30% 10% 2	3580
	11th to 20th	Night	28% 7% 14% 34% 15% 1	3572
	21st to end	Night	31% 7% 15% 26% 19% 2	3832
August	1st to 10th	Night	35% 7% 13% 26% 17% 2	2651
	11th to 20th	Night	34% 8% 14% 29% 14% 1	3032
	21st to end	Night	33% 7% 14% 26% 18% 2	3586
September	1st to 10th	Night	31% 6% 13% 29% 20% 1	2000
	11th to 20th	Night	32% 6% 14% 33% 15%	2010
	21st to end	Night	35% 6% 10% 31% 17% 1	2215
October	1st to 10th	Night	27% 4 6% 36% 25% 3	3920
	11th to 20th	Night	32% 5% 12% 31% 20% 1	3899
	21st to end	Night	46% 6% 10% 23% 15% 1	4536
November	1st to 10th	Night	43% 5% 12% 25% 13% 2	2666
	11th to 20th	Night	52% 6% 13% 18% 11% 2	2842
	21st to end	Night	51% 5% 14% 23% 7% 1	2940
December	1st to 10th	Night	45% 8% 18% 22% 5% 2	4609
	11th to 20th	Night	63% 4 10% 14% 8% 1	5201
	21st to end	Night	67% 4 8% 14% 7%	6996

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	15% 15% 33% 25% 10% 2	300
	11th to 20th	Day	21% 17% 34% 22% 5% 1	300
	21st to end	Day	18% 15% 38% 23% 6%	330
February	1st to 10th	Day	15% 19% 42% 17% 5% 2	300
	11th to 20th	Day	15% 24% 36% 19% 6%	300
	21st to end	Day	18% 19% 42% 18% 2	249
March	1st to 10th	Day	16% 17% 40% 21% 5%	300
	11th to 20th	Day	21% 17% 33% 19% 8% 3	300
	21st to end	Day	26% 13% 32% 20% 8% 1	486
April	1st to 10th	Day	24% 18% 35% 19% 4	500
	11th to 20th	Day	27% 17% 27% 19% 8% 1	492
	21st to end	Day	23% 16% 29% 22% 9% 2	500
May	1st to 10th	Day	20% 13% 32% 27% 6% 2	688
	11th to 20th	Day	19% 14% 28% 22% 13% 3	725
	21st to end	Day	19% 10% 27% 25% 13% 5%	789
June	1st to 10th	Day	12% 9% 29% 28% 17% 4	730
	11th to 20th	Day	16% 9% 32% 27% 13% 4	730
	21st to end	Day	16% 8% 28% 29% 13% 5%	730
July	1st to 10th	Day	8% 3 22% 30% 28% 9%	721
	11th to 20th	Day	8% 7% 25% 32% 18% 8%	718
	21st to end	Day	8% 4 26% 32% 23% 7%	794
August	1st to 10th	Day	9% 6% 20% 31% 25% 8%	726
	11th to 20th	Day	13% 6% 21% 27% 25% 9%	645
	21st to end	Day	13% 8% 22% 29% 22% 7%	583
September	1st to 10th	Day	16% 8% 24% 26% 18% 8%	530
	11th to 20th	Day	12% 7% 21% 33% 23% 5%	530
	21st to end	Day	15% 12% 22% 29% 17% 4	512
October	1st to 10th	Day	16% 13% 25% 28% 14% 4	330
	11th to 20th	Day	21% 21% 35% 16% 7% 1	330
	21st to end	Day	22% 14% 38% 19% 6% 2	363
November	1st to 10th	Day	17% 18% 35% 23% 7% 1	330
	11th to 20th	Day	19% 22% 34% 20% 4 1	330
	21st to end	Day	23% 15% 40% 16% 6%	330
December	1st to 10th	Day	16% 17% 40% 21% 7%	306
	11th to 20th	Day	19% 18% 40% 17% 5% 1	300
	21st to end	Day	25% 18% 36% 18% 3 1	330
January	1st to 10th	Night	15% 13% 36% 27% 8% 1	1000
	11th to 20th	Night	19% 13% 35% 27% 5% 1	1000
	21st to end	Night	19% 10% 37% 27% 7%	1100
February	1st to 10th	Night	16% 13% 37% 28% 6% 1	1000
	11th to 20th	Night	14% 14% 41% 24% 6%	915
	21st to end	Night	21% 15% 36% 24% 4	660
March	1st to 10th	Night	18% 13% 34% 28% 7% 1	800
	11th to 20th	Night	17% 12% 36% 27% 7% 1	653
	21st to end	Night	22% 11% 29% 28% 8% 2	660
April	1st to 10th	Night	23% 14% 36% 23% 4	600
	11th to 20th	Night	23% 12% 31% 27% 6%	593
	21st to end	Night	21% 10% 33% 28% 8%	600
May	1st to 10th	Night	23% 10% 32% 30% 6%	600
	11th to 20th	Night	18% 8% 32% 32% 9% 1	591
	21st to end	Night	13% 6% 28% 39% 14% 1	650
June	1st to 10th	Night	12% 6% 29% 41% 11%	600
	11th to 20th	Night	15% 6% 30% 38% 11%	600
	21st to end	Night	10% 5% 27% 43% 14% 1	600
July	1st to 10th	Night	8% 3 19% 41% 27% 2	585
	11th to 20th	Night	10% 4 20% 41% 22% 3	582
	21st to end	Night	6% 2 20% 47% 23% 2	657
August	1st to 10th	Night	8% 1 17% 48% 24% 2	597
	11th to 20th	Night	11% 3 18% 38% 26% 4	594
	21st to end	Night	13% 4 20% 42% 19% 2	660
September	1st to 10th	Night	11% 6% 23% 38% 17% 5%	600
	11th to 20th	Night	12% 4 25% 34% 22% 3	610
	21st to end	Night	15% 8% 26% 34% 17% 1	800
October	1st to 10th	Night	14% 8% 30% 30% 17% 1	800
	11th to 20th	Night	21% 12% 32% 27% 8%	800
	21st to end	Night	22% 10% 31% 30% 7%	880
November	1st to 10th	Night	21% 10% 35% 25% 9% 1	820
	11th to 20th	Night	18% 17% 38% 22% 5%	952
	21st to end	Night	21% 15% 34% 23% 6%	1050
December	1st to 10th	Night	18% 13% 40% 24% 5% 1	1011
	11th to 20th	Night	23% 13% 34% 24% 6% 1	1000
	21st to end	Night	27% 13% 30% 25% 4	1100

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