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 2024-11-06.

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	14% 6% 2 6% 5% 4 5% 4 6% 8% 41%	101204
	Night	14% 6% 2 6% 4 4 4 4 6% 7% 42%	97808
Transparency	Day	39% 8% 12% 24% 15% 3	104847
	Night	38% 7% 12% 24% 16% 3	102304
Seeing	Day	17% 12% 24% 24% 16% 6%	14925
	Night	17% 10% 28% 31% 13% 1	24507

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% 6% 2 6% 4 5% 5% 4 5% 5% 42%	2708
	11th to 20th	Day	12% 10% 3 8% 5% 5% 5% 4 5% 6% 36%	2840
	21st to end	Day	15% 9% 4 8% 5% 4 5% 4 6% 6% 35%	3124
February	1st to 10th	Day	13% 10% 2 8% 6% 4 5% 3 5% 6% 39%	1710
	11th to 20th	Day	16% 7% 2 7% 6% 4 5% 3 4 7% 39%	1663
	21st to end	Day	16% 9% 3 7% 5% 4 4 4 4 6% 39%	1588
March	1st to 10th	Day	20% 9% 2 6% 5% 4 4 3 5% 6% 34%	3435
	11th to 20th	Day	9% 6% 2 5% 4 4 4 4 6% 7% 49%	3480
	21st to end	Day	17% 8% 3 7% 4 4 4 4 5% 6% 39%	3815
April	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 7% 9% 39%	2268
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 3 5% 7% 45%	2254
	21st to end	Day	17% 6% 3 6% 4 4 5% 4 5% 5% 39%	2323
May	1st to 10th	Day	21% 7% 2 8% 5% 5% 4 5% 6% 7% 29%	4082
	11th to 20th	Day	24% 7% 2 6% 4 3 4 3 6% 8% 32%	4162
	21st to end	Day	11% 4 2 5% 4 5% 5% 5% 7% 10% 42%	4823
June	1st to 10th	Day	12% 5% 2 5% 4 5% 5% 5% 6% 9% 42%	2660
	11th to 20th	Day	10% 5% 3 6% 5% 5% 6% 5% 8% 10% 38%	2660
	21st to end	Day	9% 4 2 5% 5% 4 6% 5% 6% 10% 44%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 44%	4440
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	4156
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 4 6% 8% 39%	4466
August	1st to 10th	Day	17% 4 2 6% 5% 5% 6% 5% 7% 8% 35%	4104
	11th to 20th	Day	9% 4 2 7% 5% 6% 5% 5% 7% 9% 42%	3980
	21st to end	Day	11% 4 2 5% 4 4 4 4 6% 7% 49%	4180
September	1st to 10th	Day	15% 6% 1 6% 4 3 4 3 5% 7% 45%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 7% 46%	2235
	21st to end	Day	21% 6% 2 5% 5% 4 4 3 6% 6% 38%	2006
October	1st to 10th	Day	16% 5% 2 5% 4 3 3 2 6% 7% 46%	1900
	11th to 20th	Day	15% 5% 2 5% 3 4 4 4 5% 6% 48%	1900
	21st to end	Day	14% 5% 2 5% 4 4 4 3 5% 6% 49%	2090
November	1st to 10th	Day	10% 5% 3 4 4 4 4 3 5% 7% 52%	1879
	11th to 20th	Day	15% 7% 2 5% 3 4 4 3 5% 6% 46%	1611
	21st to end	Day	15% 5% 2 5% 4 3 5% 3 5% 7% 45%	1520
December	1st to 10th	Day	16% 9% 3 6% 4 4 5% 5% 7% 7% 35%	1520
	11th to 20th	Day	16% 5% 3 6% 4 5% 5% 4 5% 8% 40%	1910
	21st to end	Day	17% 5% 2 6% 5% 5% 7% 6% 6% 9% 31%	2772
January	1st to 10th	Night	11% 8% 2 6% 5% 4 5% 4 5% 7% 42%	4235
	11th to 20th	Night	16% 8% 2 6% 4 3 4 4 6% 6% 43%	4120
	21st to end	Night	17% 8% 3 7% 4 4 4 4 5% 6% 38%	4532
February	1st to 10th	Night	13% 8% 2 7% 4 4 4 4 6% 7% 41%	2470
	11th to 20th	Night	15% 9% 2 6% 4 4 5% 4 6% 5% 39%	2403
	21st to end	Night	14% 10% 3 6% 5% 4 4 4 5% 7% 38%	1860
March	1st to 10th	Night	19% 8% 3 6% 5% 4 4 4 5% 5% 38%	3418
	11th to 20th	Night	10% 5% 2 6% 4 4 4 3 6% 7% 48%	3480
	21st to end	Night	12% 7% 2 6% 4 4 3 3 4 5% 49%	3817
April	1st to 10th	Night	15% 7% 2 7% 6% 4 4 4 6% 6% 39%	1911
	11th to 20th	Night	12% 5% 2 7% 5% 4 4 4 7% 8% 42%	1875
	21st to end	Night	17% 5% 1 5% 4 4 4 4 5% 7% 43%	1872
May	1st to 10th	Night	23% 7% 3 7% 5% 5% 4 4 5% 8% 30%	2813
	11th to 20th	Night	23% 8% 3 7% 4 4 4 3 5% 5% 34%	2730
	21st to end	Night	11% 4 2 5% 4 4 5% 5% 8% 9% 42%	2732
June	1st to 10th	Night	10% 4 1 5% 5% 4 5% 4 7% 9% 46%	1520
	11th to 20th	Night	11% 6% 1 5% 4 4 5% 5% 7% 9% 43%	1520
	21st to end	Night	9% 4 2 5% 4 5% 5% 5% 7% 11% 43%	1520
July	1st to 10th	Night	7% 3 2 7% 5% 5% 6% 5% 7% 10% 42%	2520
	11th to 20th	Night	7% 5% 3 7% 6% 6% 6% 4 7% 9% 40%	2799
	21st to end	Night	10% 7% 3 6% 4 6% 5% 5% 8% 8% 38%	3087
August	1st to 10th	Night	16% 6% 2 6% 5% 5% 5% 5% 7% 7% 35%	2825
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 7% 8% 44%	2817
	21st to end	Night	14% 4 1 4 4 4 4 3 5% 8% 47%	3476
September	1st to 10th	Night	15% 5% 2 6% 3 4 4 4 6% 6% 45%	1900
	11th to 20th	Night	12% 6% 2 6% 4 3 3 3 4 6% 51%	1942
	21st to end	Night	20% 5% 2 6% 4 3 4 3 3 7% 42%	2172
October	1st to 10th	Night	19% 5% 2 4 3 3 3 3 5% 6% 46%	2280
	11th to 20th	Night	13% 5% 2 5% 3 2 3 3 5% 6% 52%	2280
	21st to end	Night	14% 5% 2 5% 3 3 4 4 5% 6% 51%	2508
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 5% 6% 53%	2320
	11th to 20th	Night	13% 7% 2 5% 3 3 4 3 6% 6% 47%	2565
	21st to end	Night	13% 5% 2 6% 5% 4 5% 4 5% 8% 44%	2660
December	1st to 10th	Night	15% 7% 3 7% 4 4 4 4 6% 6% 40%	2660
	11th to 20th	Night	16% 6% 2 5% 5% 4 5% 5% 5% 7% 40%	3285
	21st to end	Night	16% 6% 3 6% 5% 5% 6% 5% 7% 9% 32%	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	41% 5% 11% 28% 13% 3	2709
	11th to 20th	Day	47% 6% 11% 19% 14% 4	2840
	21st to end	Day	48% 6% 12% 21% 11% 2	3124
February	1st to 10th	Day	46% 6% 13% 21% 11% 2	1710
	11th to 20th	Day	44% 6% 10% 22% 15% 2	1672
	21st to end	Day	46% 6% 11% 20% 14% 3	1588
March	1st to 10th	Day	48% 6% 12% 20% 12% 2	3435
	11th to 20th	Day	32% 6% 10% 29% 20% 3	3480
	21st to end	Day	44% 7% 12% 20% 14% 3	3815
April	1st to 10th	Day	40% 8% 14% 17% 17% 4	2268
	11th to 20th	Day	39% 5% 11% 21% 19% 5%	2254
	21st to end	Day	44% 7% 9% 22% 14% 4	2323
May	1st to 10th	Day	50% 8% 10% 20% 10% 1	4120
	11th to 20th	Day	49% 9% 10% 23% 8% 1	4166
	21st to end	Day	32% 11% 14% 24% 16% 2	4837
June	1st to 10th	Day	36% 9% 13% 25% 16% 1	2660
	11th to 20th	Day	37% 11% 15% 21% 13% 2	2660
	21st to end	Day	32% 10% 16% 25% 15% 2	2660
July	1st to 10th	Day	32% 10% 17% 25% 11% 5%	4370
	11th to 20th	Day	33% 9% 16% 30% 11% 1	4085
	21st to end	Day	41% 8% 9% 22% 18% 1	4324
August	1st to 10th	Day	43% 9% 15% 24% 8%	4091
	11th to 20th	Day	35% 9% 14% 27% 15% 1	4019
	21st to end	Day	32% 8% 15% 26% 17% 2	4180
September	1st to 10th	Day	39% 7% 11% 18% 21% 4	2280
	11th to 20th	Day	35% 7% 10% 26% 20% 3	2235
	21st to end	Day	46% 6% 11% 19% 17% 2	2006
October	1st to 10th	Day	34% 5% 9% 21% 27% 5%	3160
	11th to 20th	Day	25% 6% 9% 29% 23% 7%	3140
	21st to end	Day	25% 4 11% 29% 27% 4	3428
November	1st to 10th	Day	32% 6% 12% 24% 22% 4	1879
	11th to 20th	Day	38% 4 12% 21% 21% 4	1611
	21st to end	Day	39% 5% 12% 27% 15% 1	1520
December	1st to 10th	Day	46% 7% 14% 22% 10% 1	1520
	11th to 20th	Day	41% 6% 12% 29% 9% 3	1906
	21st to end	Day	44% 9% 17% 20% 9% 1	2772
January	1st to 10th	Night	38% 7% 12% 26% 14% 3	4235
	11th to 20th	Night	40% 6% 13% 24% 13% 3	4120
	21st to end	Night	47% 6% 11% 24% 11% 1	4532
February	1st to 10th	Night	41% 7% 13% 25% 13% 1	2470
	11th to 20th	Night	45% 5% 11% 21% 15% 4	2405
	21st to end	Night	45% 6% 12% 20% 12% 5%	1860
March	1st to 10th	Night	46% 7% 10% 26% 10% 1	3418
	11th to 20th	Night	33% 7% 11% 31% 16% 2	3480
	21st to end	Night	37% 6% 11% 24% 18% 4	3817
April	1st to 10th	Night	43% 7% 10% 19% 17% 3	1911
	11th to 20th	Night	38% 7% 12% 21% 17% 5%	1875
	21st to end	Night	38% 7% 13% 25% 13% 4	1872
May	1st to 10th	Night	52% 8% 10% 18% 11% 2	2840
	11th to 20th	Night	49% 9% 11% 21% 9% 1	2731
	21st to end	Night	33% 12% 16% 26% 10% 3	2739
June	1st to 10th	Night	33% 10% 11% 27% 17% 3	1520
	11th to 20th	Night	35% 12% 13% 25% 14% 2	1520
	21st to end	Night	32% 9% 16% 25% 17% 2	1520
July	1st to 10th	Night	35% 11% 20% 18% 12% 5%	2480
	11th to 20th	Night	38% 11% 16% 21% 13% 2	2747
	21st to end	Night	38% 11% 15% 19% 16% 1	2988
August	1st to 10th	Night	45% 9% 15% 22% 8% 1	2814
	11th to 20th	Night	35% 9% 13% 25% 16% 1	2844
	21st to end	Night	34% 7% 14% 28% 15% 2	3476
September	1st to 10th	Night	37% 8% 11% 20% 19% 4	1900
	11th to 20th	Night	34% 5% 9% 27% 22% 2	1942
	21st to end	Night	42% 7% 10% 20% 18% 2	2172
October	1st to 10th	Night	37% 6% 11% 23% 21% 3	3800
	11th to 20th	Night	23% 5% 12% 23% 31% 6%	3779
	21st to end	Night	23% 5% 11% 31% 26% 5%	4120
November	1st to 10th	Night	32% 5% 12% 26% 21% 5%	2320
	11th to 20th	Night	37% 5% 9% 24% 20% 5%	2565
	21st to end	Night	38% 6% 12% 24% 18% 3	2660
December	1st to 10th	Night	44% 7% 11% 26% 12% 1	2660
	11th to 20th	Night	42% 5% 11% 23% 16% 2	3288
	21st to end	Night	42% 11% 16% 19% 11% 1	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	22% 30% 27% 15% 5% 1	234
	11th to 20th	Day	26% 24% 32% 15% 4	270
	21st to end	Day	22% 25% 33% 14% 5% 1	297
February	1st to 10th	Day	25% 21% 34% 13% 7%	270
	11th to 20th	Day	30% 27% 33% 9% 1	270
	21st to end	Day	27% 20% 31% 19% 3	372
March	1st to 10th	Day	21% 24% 25% 26% 3 1	460
	11th to 20th	Day	20% 23% 32% 17% 6% 2	460
	21st to end	Day	19% 18% 34% 22% 7% 1	506
April	1st to 10th	Day	21% 19% 27% 22% 9% 1	460
	11th to 20th	Day	14% 17% 29% 22% 12% 6%	452
	21st to end	Day	24% 14% 26% 23% 11% 2	460
May	1st to 10th	Day	21% 16% 25% 21% 13% 4	463
	11th to 20th	Day	22% 11% 25% 21% 16% 5%	487
	21st to end	Day	18% 5% 22% 25% 21% 9%	529
June	1st to 10th	Day	15% 7% 26% 25% 20% 8%	490
	11th to 20th	Day	12% 7% 23% 29% 19% 9%	490
	21st to end	Day	12% 4 25% 30% 21% 8%	490
July	1st to 10th	Day	10% 4 17% 27% 26% 16%	485
	11th to 20th	Day	6% 3 15% 32% 31% 13%	484
	21st to end	Day	11% 4 17% 31% 27% 10%	532
August	1st to 10th	Day	12% 3 17% 26% 27% 14%	486
	11th to 20th	Day	11% 4 17% 28% 28% 13%	479
	21st to end	Day	8% 4 18% 25% 29% 17%	539
September	1st to 10th	Day	18% 5% 18% 21% 25% 12%	490
	11th to 20th	Day	15% 3 15% 28% 26% 13%	490
	21st to end	Day	28% 8% 17% 27% 15% 6%	490
October	1st to 10th	Day	20% 6% 18% 29% 20% 7%	490
	11th to 20th	Day	16% 12% 27% 27% 15% 4	490
	21st to end	Day	16% 12% 30% 26% 13% 4	539
November	1st to 10th	Day	15% 12% 26% 29% 16% 3	462
	11th to 20th	Day	21% 13% 29% 25% 12%	271
	21st to end	Day	16% 21% 33% 22% 7% 1	180
December	1st to 10th	Day	18% 23% 30% 22% 6% 2	180
	11th to 20th	Day	21% 18% 31% 23% 7%	180
	21st to end	Day	20% 14% 32% 24% 11%	198
January	1st to 10th	Night	18% 16% 40% 22% 4	760
	11th to 20th	Night	22% 15% 31% 28% 4	760
	21st to end	Night	19% 14% 42% 23% 2	836
February	1st to 10th	Night	16% 18% 35% 29% 2	760
	11th to 20th	Night	22% 21% 37% 19% 2	743
	21st to end	Night	22% 17% 38% 20% 3	628
March	1st to 10th	Night	18% 15% 39% 24% 4	760
	11th to 20th	Night	21% 19% 32% 22% 5% 1	760
	21st to end	Night	17% 14% 41% 23% 5% 1	836
April	1st to 10th	Night	20% 18% 32% 25% 4	760
	11th to 20th	Night	16% 11% 34% 30% 9% 1	751
	21st to end	Night	18% 10% 31% 33% 7% 1	732
May	1st to 10th	Night	22% 6% 27% 31% 14% 1	570
	11th to 20th	Night	20% 4 26% 36% 14% 1	518
	21st to end	Night	13% 3 20% 40% 22% 1	411
June	1st to 10th	Night	11% 4 23% 37% 25% 1	380
	11th to 20th	Night	12% 3 18% 43% 21% 2	380
	21st to end	Night	7% 2 21% 50% 20% 1	380
July	1st to 10th	Night	10% 4 14% 41% 27% 4	370
	11th to 20th	Night	6% 2 12% 40% 37% 4	526
	21st to end	Night	9% 2 12% 44% 30% 3	624
August	1st to 10th	Night	11% 1 11% 43% 31% 3	567
	11th to 20th	Night	11% 2 13% 37% 33% 4	583
	21st to end	Night	13% 2 14% 39% 28% 4	836
September	1st to 10th	Night	17% 2 13% 36% 28% 4	760
	11th to 20th	Night	13% 3 17% 33% 31% 4	760
	21st to end	Night	21% 3 22% 31% 22% 1	760
October	1st to 10th	Night	21% 5% 21% 29% 22% 3	760
	11th to 20th	Night	16% 8% 26% 37% 13% 1	760
	21st to end	Night	16% 9% 31% 32% 11%	836
November	1st to 10th	Night	13% 8% 31% 34% 12% 1	764
	11th to 20th	Night	17% 15% 28% 31% 8% 1	760
	21st to end	Night	16% 14% 31% 31% 8%	760
December	1st to 10th	Night	19% 14% 34% 27% 6%	760
	11th to 20th	Night	18% 9% 39% 30% 4	760
	21st to end	Night	18% 11% 33% 35% 3	836

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