Flint Ridge Observatory
Clear Sky Chart
History

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

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	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	126617
	Night	13% 6% 2 6% 4 4 5% 4 6% 7% 43%	123400
Transparency	Day	39% 7% 12% 23% 16% 3	130216
	Night	38% 7% 12% 23% 16% 3	127870
Seeing	Day	18% 12% 25% 24% 16% 6%	16217
	Night	17% 10% 28% 31% 13% 1	25784

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	13% 6% 2 6% 4 5% 5% 4 5% 5% 45%	3872
	11th to 20th	Day	11% 9% 2 7% 4 4 4 3 5% 7% 43%	4060
	21st to end	Day	13% 7% 3 7% 4 4 5% 4 6% 6% 42%	4466
February	1st to 10th	Day	13% 10% 2 8% 6% 4 5% 3 5% 6% 39%	1800
	11th to 20th	Day	17% 7% 2 7% 6% 5% 5% 3 4 7% 38%	1753
	21st to end	Day	16% 8% 3 6% 4 4 4 4 4 6% 40%	1670
March	1st to 10th	Day	17% 8% 2 6% 5% 4 4 3 5% 6% 41%	4935
	11th to 20th	Day	10% 6% 2 5% 3 4 4 3 6% 8% 49%	4980
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 6% 6% 39%	5465
April	1st to 10th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 8% 38%	2388
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 3 5% 7% 45%	2374
	21st to end	Day	17% 6% 3 6% 4 4 5% 4 5% 6% 40%	2446
May	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 5% 7% 8% 30%	5862
	11th to 20th	Day	23% 7% 2 6% 4 4 5% 4 7% 9% 31%	5970
	21st to end	Day	16% 5% 2 6% 4 5% 5% 5% 7% 9% 37%	6934
June	1st to 10th	Day	12% 5% 2 5% 4 4 5% 5% 6% 9% 43%	2800
	11th to 20th	Day	10% 5% 3 6% 5% 5% 6% 5% 8% 10% 38%	2800
	21st to end	Day	9% 4 2 5% 4 4 6% 5% 6% 10% 45%	2800
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 7% 10% 46%	6360
	11th to 20th	Day	9% 5% 2 7% 5% 6% 6% 6% 8% 11% 35%	5950
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 41%	6424
August	1st to 10th	Day	17% 4 2 6% 5% 5% 6% 5% 7% 8% 35%	4234
	11th to 20th	Day	9% 4 2 7% 5% 6% 6% 5% 7% 9% 42%	4108
	21st to end	Day	11% 4 2 5% 4 4 4 4 6% 7% 49%	4312
September	1st to 10th	Day	14% 6% 1 6% 4 3 4 4 5% 7% 46%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 7% 47%	2352
	21st to end	Day	21% 6% 2 6% 5% 4 4 3 6% 6% 37%	2111
October	1st to 10th	Day	16% 5% 2 5% 4 3 3 2 6% 7% 48%	2000
	11th to 20th	Day	15% 5% 2 5% 3 4 4 4 5% 6% 48%	2000
	21st to end	Day	14% 5% 2 5% 4 4 4 3 5% 6% 49%	2200
November	1st to 10th	Day	10% 5% 2 4 4 4 4 3 5% 6% 52%	1946
	11th to 20th	Day	15% 7% 2 5% 3 4 4 3 5% 6% 46%	1695
	21st to end	Day	14% 6% 2 5% 5% 4 5% 3 5% 7% 44%	1600
December	1st to 10th	Day	12% 6% 2 4 4 4 4 4 6% 7% 48%	2600
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 4 7% 39%	2990
	21st to end	Day	17% 7% 2 6% 5% 5% 6% 5% 7% 9% 31%	3960
January	1st to 10th	Night	10% 7% 2 6% 4 4 5% 4 5% 8% 46%	6057
	11th to 20th	Night	13% 7% 2 5% 3 3 4 4 5% 5% 48%	5900
	21st to end	Night	14% 7% 2 6% 4 4 4 4 5% 5% 46%	6490
February	1st to 10th	Night	13% 8% 2 7% 4 4 4 4 6% 7% 41%	2600
	11th to 20th	Night	15% 9% 2 6% 4 5% 5% 4 6% 5% 39%	2533
	21st to end	Night	14% 10% 3 6% 5% 4 5% 4 5% 7% 39%	1954
March	1st to 10th	Night	15% 6% 2 5% 4 3 4 3 5% 5% 47%	4918
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 6% 8% 49%	4980
	21st to end	Night	10% 6% 2 7% 4 5% 5% 4 5% 6% 47%	5467
April	1st to 10th	Night	16% 7% 2 7% 6% 4 4 4 5% 6% 38%	2011
	11th to 20th	Night	13% 5% 2 7% 5% 4 4 4 7% 8% 41%	1975
	21st to end	Night	16% 5% 1 5% 4 4 4 4 5% 7% 44%	1970
May	1st to 10th	Night	21% 7% 3 8% 5% 5% 4 4 5% 8% 30%	4033
	11th to 20th	Night	24% 7% 2 6% 4 4 5% 4 5% 7% 32%	3908
	21st to end	Night	17% 6% 2 6% 4 4 5% 4 7% 8% 35%	3920
June	1st to 10th	Night	10% 5% 1 5% 5% 4 5% 4 7% 9% 45%	1600
	11th to 20th	Night	12% 6% 1 5% 4 5% 5% 5% 7% 9% 42%	1600
	21st to end	Night	8% 4 2 5% 4 5% 6% 5% 7% 11% 43%	1600
July	1st to 10th	Night	7% 5% 2 7% 5% 5% 6% 5% 6% 10% 42%	3598
	11th to 20th	Night	9% 6% 3 9% 7% 7% 7% 5% 8% 9% 31%	4002
	21st to end	Night	8% 6% 2 6% 4 6% 5% 5% 8% 10% 40%	4427
August	1st to 10th	Night	16% 6% 2 6% 5% 5% 5% 4 7% 7% 35%	2915
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 7% 8% 44%	2908
	21st to end	Night	14% 4 1 4 4 4 4 3 6% 8% 47%	3586
September	1st to 10th	Night	15% 5% 2 6% 3 4 4 4 6% 6% 46%	2000
	11th to 20th	Night	12% 6% 2 6% 4 3 3 3 4 6% 51%	2044
	21st to end	Night	21% 6% 2 6% 4 3 4 3 4 7% 41%	2287
October	1st to 10th	Night	19% 5% 2 4 3 3 3 3 5% 6% 48%	2400
	11th to 20th	Night	14% 5% 2 5% 3 2 3 3 5% 6% 52%	2400
	21st to end	Night	14% 5% 2 5% 2 3 4 3 5% 6% 51%	2640
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 5% 6% 53%	2396
	11th to 20th	Night	14% 7% 2 5% 3 3 4 4 6% 6% 46%	2700
	21st to end	Night	13% 5% 2 6% 5% 4 5% 4 5% 8% 44%	2800
December	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 7% 51%	4580
	11th to 20th	Night	17% 8% 2 6% 5% 5% 5% 4 5% 6% 38%	5205
	21st to end	Night	15% 7% 3 6% 5% 5% 6% 5% 7% 9% 32%	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	38% 5% 10% 26% 16% 5%	3873
	11th to 20th	Day	40% 5% 10% 20% 18% 7%	4060
	21st to end	Day	42% 6% 11% 24% 13% 3	4466
February	1st to 10th	Day	46% 6% 13% 22% 11% 2	1800
	11th to 20th	Day	46% 6% 10% 21% 15% 2	1762
	21st to end	Day	44% 6% 11% 21% 15% 4	1670
March	1st to 10th	Day	42% 5% 10% 21% 15% 7%	4935
	11th to 20th	Day	32% 6% 11% 27% 19% 5%	4980
	21st to end	Day	43% 7% 10% 18% 17% 5%	5465
April	1st to 10th	Day	41% 7% 13% 17% 17% 4	2388
	11th to 20th	Day	39% 5% 11% 21% 19% 5%	2374
	21st to end	Day	43% 7% 9% 23% 15% 3	2446
May	1st to 10th	Day	46% 9% 14% 19% 9% 2	5897
	11th to 20th	Day	48% 8% 10% 25% 8% 1	5974
	21st to end	Day	39% 10% 14% 21% 15% 2	6949
June	1st to 10th	Day	36% 9% 13% 25% 16% 1	2800
	11th to 20th	Day	38% 11% 15% 21% 13% 2	2800
	21st to end	Day	32% 10% 16% 25% 16% 2	2800
July	1st to 10th	Day	32% 10% 15% 24% 15% 4	6290
	11th to 20th	Day	38% 11% 18% 24% 8% 1	5879
	21st to end	Day	36% 8% 11% 23% 21% 1	6240
August	1st to 10th	Day	43% 9% 15% 25% 8%	4221
	11th to 20th	Day	35% 9% 14% 27% 14% 1	4147
	21st to end	Day	32% 8% 15% 26% 17% 2	4312
September	1st to 10th	Day	38% 7% 11% 19% 21% 4	2400
	11th to 20th	Day	35% 7% 10% 26% 20% 3	2352
	21st to end	Day	47% 6% 11% 18% 17% 2	2111
October	1st to 10th	Day	33% 5% 9% 21% 27% 5%	3260
	11th to 20th	Day	25% 6% 9% 30% 23% 7%	3240
	21st to end	Day	25% 4 11% 29% 27% 4	3538
November	1st to 10th	Day	32% 6% 12% 24% 22% 4	1946
	11th to 20th	Day	38% 4 12% 20% 22% 4	1695
	21st to end	Day	39% 6% 12% 27% 15% 1	1600
December	1st to 10th	Day	34% 7% 15% 27% 12% 4	2600
	11th to 20th	Day	46% 4 14% 24% 10% 2	2986
	21st to end	Day	45% 9% 17% 16% 13% 1	3960
January	1st to 10th	Night	34% 7% 10% 26% 20% 3	6057
	11th to 20th	Night	36% 5% 11% 24% 18% 6%	5900
	21st to end	Night	39% 5% 10% 28% 16% 2	6490
February	1st to 10th	Night	41% 7% 13% 24% 13% 1	2600
	11th to 20th	Night	45% 5% 11% 21% 15% 4	2535
	21st to end	Night	44% 6% 12% 20% 13% 5%	1954
March	1st to 10th	Night	37% 6% 10% 26% 14% 7%	4918
	11th to 20th	Night	31% 7% 13% 28% 16% 5%	4980
	21st to end	Night	37% 6% 12% 23% 18% 4	5467
April	1st to 10th	Night	44% 7% 10% 19% 17% 3	2011
	11th to 20th	Night	39% 7% 12% 21% 16% 5%	1975
	21st to end	Night	38% 7% 12% 25% 14% 4	1970
May	1st to 10th	Night	52% 8% 12% 16% 9% 4	4060
	11th to 20th	Night	49% 8% 12% 22% 9% 1	3909
	21st to end	Night	43% 10% 14% 24% 7% 2	3927
June	1st to 10th	Night	34% 9% 11% 26% 17% 3	1600
	11th to 20th	Night	36% 11% 13% 24% 14% 2	1600
	21st to end	Night	32% 9% 15% 24% 18% 2	1600
July	1st to 10th	Night	36% 12% 17% 18% 14% 4	3560
	11th to 20th	Night	46% 12% 16% 16% 9% 1	3953
	21st to end	Night	34% 10% 14% 23% 18% 1	4297
August	1st to 10th	Night	44% 9% 15% 22% 9% 1	2904
	11th to 20th	Night	35% 9% 13% 26% 16% 1	2935
	21st to end	Night	34% 7% 14% 28% 15% 2	3586
September	1st to 10th	Night	37% 8% 11% 20% 20% 4	2000
	11th to 20th	Night	34% 5% 10% 27% 22% 2	2044
	21st to end	Night	44% 7% 11% 19% 17% 2	2287
October	1st to 10th	Night	36% 6% 11% 23% 22% 3	3920
	11th to 20th	Night	23% 5% 11% 23% 31% 6%	3899
	21st to end	Night	23% 5% 11% 31% 26% 5%	4252
November	1st to 10th	Night	31% 5% 13% 25% 21% 5%	2396
	11th to 20th	Night	37% 5% 9% 24% 20% 6%	2700
	21st to end	Night	38% 6% 12% 23% 18% 3	2800
December	1st to 10th	Night	33% 6% 14% 30% 17% 1	4580
	11th to 20th	Night	46% 5% 13% 19% 14% 3	5208
	21st to end	Night	43% 10% 15% 18% 13%	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	25% 30% 26% 13% 5% 1	260
	11th to 20th	Day	26% 25% 32% 14% 3	300
	21st to end	Day	22% 23% 35% 15% 5% 1	330
February	1st to 10th	Day	26% 22% 34% 12% 6%	300
	11th to 20th	Day	34% 27% 31% 8% 1	300
	21st to end	Day	26% 20% 33% 19% 2	404
March	1st to 10th	Day	22% 24% 24% 26% 3 1	500
	11th to 20th	Day	20% 23% 31% 17% 6% 2	500
	21st to end	Day	20% 18% 33% 21% 6% 1	550
April	1st to 10th	Day	24% 19% 26% 21% 8% 1	500
	11th to 20th	Day	15% 17% 29% 21% 12% 5%	492
	21st to end	Day	23% 14% 27% 23% 11% 2	500
May	1st to 10th	Day	20% 15% 28% 20% 13% 4	503
	11th to 20th	Day	22% 13% 25% 20% 15% 5%	527
	21st to end	Day	20% 7% 22% 23% 20% 8%	573
June	1st to 10th	Day	15% 7% 26% 24% 20% 8%	530
	11th to 20th	Day	14% 7% 23% 30% 18% 8%	530
	21st to end	Day	12% 4 24% 30% 22% 9%	530
July	1st to 10th	Day	10% 4 17% 27% 27% 15%	525
	11th to 20th	Day	6% 3 15% 31% 31% 13%	524
	21st to end	Day	10% 4 16% 32% 27% 11%	576
August	1st to 10th	Day	12% 3 17% 27% 26% 14%	526
	11th to 20th	Day	11% 4 16% 28% 28% 13%	519
	21st to end	Day	9% 4 18% 25% 28% 16%	583
September	1st to 10th	Day	17% 5% 19% 22% 25% 12%	530
	11th to 20th	Day	15% 3 14% 27% 28% 13%	530
	21st to end	Day	28% 8% 18% 27% 15% 5%	530
October	1st to 10th	Day	18% 6% 18% 29% 20% 9%	530
	11th to 20th	Day	16% 12% 27% 26% 15% 4	530
	21st to end	Day	16% 13% 30% 26% 12% 3	583
November	1st to 10th	Day	15% 13% 27% 29% 15% 3	487
	11th to 20th	Day	20% 12% 32% 24% 12%	295
	21st to end	Day	19% 20% 34% 22% 6% 1	200
December	1st to 10th	Day	18% 22% 32% 22% 5% 2	200
	11th to 20th	Day	21% 18% 31% 24% 7%	200
	21st to end	Day	19% 15% 33% 24% 10%	220
January	1st to 10th	Night	18% 18% 39% 21% 3	800
	11th to 20th	Night	22% 16% 32% 27% 4	800
	21st to end	Night	18% 14% 44% 22% 2	880
February	1st to 10th	Night	17% 18% 36% 28% 2	800
	11th to 20th	Night	22% 21% 36% 19% 2	783
	21st to end	Night	22% 17% 39% 20% 3	660
March	1st to 10th	Night	18% 16% 39% 24% 4	800
	11th to 20th	Night	20% 19% 32% 23% 5% 1	800
	21st to end	Night	16% 14% 42% 22% 5% 1	880
April	1st to 10th	Night	21% 18% 32% 25% 4	800
	11th to 20th	Night	17% 12% 33% 29% 8% 1	791
	21st to end	Night	18% 10% 31% 34% 7% 1	770
May	1st to 10th	Night	22% 6% 27% 31% 14% 1	600
	11th to 20th	Night	21% 4 26% 35% 13% 1	545
	21st to end	Night	14% 3 21% 39% 21% 1	433
June	1st to 10th	Night	11% 4 24% 38% 24% 1	400
	11th to 20th	Night	13% 4 18% 43% 20% 2	400
	21st to end	Night	7% 2 21% 49% 22% 1	400
July	1st to 10th	Night	10% 4 14% 39% 28% 4	390
	11th to 20th	Night	5% 2 12% 39% 37% 5%	555
	21st to end	Night	9% 2 11% 45% 30% 3	657
August	1st to 10th	Night	11% 2 11% 43% 31% 3	597
	11th to 20th	Night	11% 2 12% 37% 33% 3	614
	21st to end	Night	13% 2 14% 40% 28% 4	880
September	1st to 10th	Night	16% 2 14% 36% 28% 4	800
	11th to 20th	Night	13% 3 16% 34% 30% 3	800
	21st to end	Night	22% 3 21% 32% 21% 1	800
October	1st to 10th	Night	20% 5% 21% 29% 23% 3	800
	11th to 20th	Night	16% 8% 26% 36% 13% 1	800
	21st to end	Night	16% 9% 31% 33% 11%	880
November	1st to 10th	Night	13% 8% 32% 35% 11% 1	789
	11th to 20th	Night	18% 14% 29% 31% 7% 1	800
	21st to end	Night	16% 15% 32% 30% 7%	800
December	1st to 10th	Night	18% 14% 34% 28% 6%	800
	11th to 20th	Night	18% 10% 38% 30% 4	800
	21st to end	Night	18% 11% 34% 35% 3	880

Page generated at 2025-10-31 02:02:40. Version ac07

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