Richville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Richville clear sky chart from 2005-11-06 to 2025-12-18.

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	12% 8% 3 8% 5% 5% 5% 4 6% 7% 37%	127453
	Night	10% 9% 4 9% 6% 5% 5% 4 6% 7% 35%	123839
Transparency	Day	44% 6% 13% 25% 10% 1	130975
	Night	47% 6% 12% 23% 11% 1	128398
Seeing	Day	15% 9% 30% 28% 15% 3	17627
	Night	15% 9% 33% 32% 11% 1	27564

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	6% 12% 4 12% 11% 9% 9% 6% 6% 6% 19%	3178
	11th to 20th	Day	6% 9% 4 15% 6% 7% 13% 9% 9% 8% 14%	3364
	21st to end	Day	4 10% 9% 18% 9% 8% 5% 4 5% 6% 22%	4382
February	1st to 10th	Day	7% 14% 5% 12% 7% 6% 7% 5% 8% 6% 23%	1800
	11th to 20th	Day	7% 11% 4 9% 8% 8% 6% 5% 6% 8% 28%	1754
	21st to end	Day	8% 11% 4 11% 9% 7% 7% 5% 6% 6% 26%	1545
March	1st to 10th	Day	10% 9% 3 8% 5% 4 4 3 6% 7% 40%	4804
	11th to 20th	Day	9% 10% 3 8% 6% 4 5% 4 6% 10% 35%	4980
	21st to end	Day	19% 12% 5% 10% 7% 5% 5% 3 5% 6% 24%	5462
April	1st to 10th	Day	16% 10% 5% 7% 5% 4 5% 3 5% 6% 34%	2335
	11th to 20th	Day	16% 13% 3 9% 4 4 4 3 6% 6% 32%	2564
	21st to end	Day	21% 10% 3 7% 5% 4 4 3 5% 6% 33%	2600
May	1st to 10th	Day	13% 7% 2 5% 4 4 3 3 5% 7% 49%	5944
	11th to 20th	Day	17% 8% 2 5% 3 3 4 3 5% 7% 42%	6319
	21st to end	Day	15% 6% 3 6% 5% 4 4 4 5% 8% 42%	7057
June	1st to 10th	Day	11% 6% 2 5% 4 5% 5% 5% 6% 8% 42%	3000
	11th to 20th	Day	14% 7% 2 7% 5% 4 5% 4 6% 7% 39%	3000
	21st to end	Day	10% 6% 2 5% 5% 5% 5% 5% 8% 9% 41%	3000
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 7% 10% 47%	6800
	11th to 20th	Day	11% 4 2 5% 3 3 4 4 6% 8% 50%	6800
	21st to end	Day	9% 4 2 6% 4 4 5% 4 7% 10% 46%	6812
August	1st to 10th	Day	12% 4 2 5% 3 3 4 4 6% 10% 46%	4234
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 6% 9% 43%	4171
	21st to end	Day	13% 5% 2 6% 4 3 4 3 5% 7% 48%	4675
September	1st to 10th	Day	11% 5% 2 4 3 4 4 3 6% 8% 49%	2405
	11th to 20th	Day	12% 6% 2 7% 4 5% 4 4 6% 6% 44%	2228
	21st to end	Day	13% 6% 2 5% 4 4 4 3 6% 8% 44%	2195
October	1st to 10th	Day	15% 9% 3 5% 4 5% 4 4 6% 6% 40%	2000
	11th to 20th	Day	17% 12% 3 7% 3 4 3 3 4 6% 38%	2000
	21st to end	Day	19% 12% 3 8% 4 3 3 4 5% 6% 32%	2100
November	1st to 10th	Day	14% 14% 5% 11% 4 3 4 3 4 5% 32%	1705
	11th to 20th	Day	11% 17% 5% 14% 6% 5% 4 4 5% 4 27%	1680
	21st to end	Day	11% 11% 6% 14% 7% 6% 5% 4 5% 6% 26%	1680
December	1st to 10th	Day	9% 12% 5% 13% 11% 11% 8% 5% 6% 6% 15%	2690
	11th to 20th	Day	7% 16% 9% 11% 6% 6% 5% 4 6% 6% 23%	2692
	21st to end	Day	15% 17% 6% 17% 8% 5% 3 3 4 5% 18%	3498
January	1st to 10th	Night	4 9% 5% 16% 11% 9% 8% 5% 6% 7% 20%	6787
	11th to 20th	Night	5% 12% 5% 10% 8% 9% 11% 9% 9% 7% 15%	6600
	21st to end	Night	5% 14% 11% 13% 7% 6% 7% 4 6% 7% 22%	6582
February	1st to 10th	Night	7% 11% 5% 11% 6% 7% 6% 5% 8% 8% 28%	2600
	11th to 20th	Night	5% 10% 4 9% 7% 5% 6% 5% 7% 8% 34%	2533
	21st to end	Night	10% 10% 4 9% 8% 6% 6% 5% 7% 7% 29%	2102
March	1st to 10th	Night	9% 7% 2 7% 5% 4 4 4 6% 8% 44%	5055
	11th to 20th	Night	9% 9% 3 10% 9% 5% 6% 4 6% 7% 33%	4980
	21st to end	Night	19% 13% 4 11% 5% 4 3 3 4 5% 29%	5467
April	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 6% 7% 38%	2064
	11th to 20th	Night	17% 11% 4 8% 3 3 3 3 4 6% 37%	1784
	21st to end	Night	18% 10% 3 7% 5% 4 5% 3 4 5% 37%	1800
May	1st to 10th	Night	13% 8% 2 5% 3 3 4 3 4 5% 51%	3971
	11th to 20th	Night	17% 8% 2 4 3 3 3 3 5% 6% 46%	3596
	21st to end	Night	15% 8% 2 6% 4 5% 4 4 5% 6% 40%	3815
June	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 6% 9% 50%	1400
	11th to 20th	Night	12% 7% 2 5% 4 3 4 4 6% 8% 45%	1400
	21st to end	Night	8% 5% 1 6% 4 3 4 4 6% 9% 51%	1400
July	1st to 10th	Night	9% 3 1 5% 4 5% 5% 4 6% 9% 49%	3178
	11th to 20th	Night	7% 3 2 3 3 2 4 3 6% 9% 58%	3177
	21st to end	Night	9% 4 2 6% 4 5% 6% 4 6% 9% 47%	4056
August	1st to 10th	Night	10% 4 2 4 4 4 5% 3 5% 6% 53%	2926
	11th to 20th	Night	13% 4 2 5% 3 3 4 3 5% 9% 51%	2888
	21st to end	Night	11% 4 2 5% 3 3 3 3 4 8% 51%	3234
September	1st to 10th	Night	9% 4 1 4 3 4 4 3 5% 7% 55%	1994
	11th to 20th	Night	9% 5% 2 5% 4 3 4 4 6% 8% 51%	2170
	21st to end	Night	12% 5% 2 5% 4 3 3 3 5% 6% 52%	2200
October	1st to 10th	Night	13% 7% 3 6% 3 4 4 4 6% 7% 44%	2384
	11th to 20th	Night	15% 10% 3 6% 4 4 4 3 4 7% 40%	2400
	21st to end	Night	17% 11% 3 8% 4 4 4 3 5% 6% 35%	2736
November	1st to 10th	Night	10% 13% 4 9% 5% 5% 4 3 6% 7% 35%	2813
	11th to 20th	Night	11% 13% 5% 14% 6% 4 4 3 5% 6% 29%	2940
	21st to end	Night	11% 11% 4 11% 7% 5% 5% 4 5% 6% 30%	2940
December	1st to 10th	Night	5% 9% 6% 13% 13% 10% 7% 5% 6% 7% 20%	4720
	11th to 20th	Night	9% 14% 5% 16% 8% 6% 5% 3 5% 6% 22%	5667
	21st to end	Night	16% 17% 6% 16% 8% 5% 5% 3 5% 5% 14%	7480

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	64% 5% 7% 15% 7%	3179
	11th to 20th	Day	61% 6% 7% 20% 4	3364
	21st to end	Day	63% 5% 11% 15% 6%	4382
February	1st to 10th	Day	57% 5% 10% 19% 9%	1800
	11th to 20th	Day	52% 6% 14% 21% 7% 1	1763
	21st to end	Day	55% 8% 11% 18% 9%	1545
March	1st to 10th	Day	43% 5% 17% 25% 9% 1	4804
	11th to 20th	Day	44% 5% 14% 29% 8%	4980
	21st to end	Day	61% 6% 12% 17% 5%	5464
April	1st to 10th	Day	50% 6% 9% 21% 12% 1	2335
	11th to 20th	Day	51% 6% 14% 17% 11% 1	2564
	21st to end	Day	52% 5% 10% 23% 8% 1	2600
May	1st to 10th	Day	34% 5% 13% 28% 18% 1	5982
	11th to 20th	Day	41% 6% 10% 23% 14% 6%	6323
	21st to end	Day	39% 6% 11% 31% 12% 1	7071
June	1st to 10th	Day	37% 8% 16% 30% 9% 1	3000
	11th to 20th	Day	43% 8% 14% 22% 12% 1	3000
	21st to end	Day	36% 9% 18% 26% 11%	3000
July	1st to 10th	Day	30% 8% 21% 31% 10%	6726
	11th to 20th	Day	31% 6% 17% 35% 10% 1	6719
	21st to end	Day	31% 8% 19% 31% 10% 1	6619
August	1st to 10th	Day	33% 6% 15% 31% 12% 2	4220
	11th to 20th	Day	37% 7% 15% 32% 8% 1	4210
	21st to end	Day	35% 6% 17% 30% 11% 1	4674
September	1st to 10th	Day	32% 7% 16% 34% 11% 1	2405
	11th to 20th	Day	38% 7% 16% 29% 9%	2228
	21st to end	Day	36% 6% 13% 34% 9% 1	2195
October	1st to 10th	Day	33% 4 10% 34% 18% 1	3260
	11th to 20th	Day	42% 4 9% 24% 20% 1	3240
	21st to end	Day	51% 4 14% 24% 7%	3381
November	1st to 10th	Day	54% 6% 10% 20% 9% 1	1705
	11th to 20th	Day	60% 5% 12% 15% 8%	1680
	21st to end	Day	57% 6% 14% 15% 6% 1	1680
December	1st to 10th	Day	68% 7% 12% 10% 3 1	2690
	11th to 20th	Day	60% 5% 12% 16% 8%	2689
	21st to end	Day	70% 5% 7% 13% 5%	3498
January	1st to 10th	Night	63% 6% 8% 15% 8%	6787
	11th to 20th	Night	61% 8% 9% 12% 9% 1	6600
	21st to end	Night	59% 5% 14% 17% 4	6582
February	1st to 10th	Night	50% 6% 12% 20% 10% 1	2600
	11th to 20th	Night	46% 6% 12% 22% 13% 1	2534
	21st to end	Night	51% 6% 12% 20% 10% 1	2102
March	1st to 10th	Night	37% 6% 17% 26% 13% 2	5055
	11th to 20th	Night	49% 6% 11% 23% 11%	4980
	21st to end	Night	59% 4 10% 19% 8% 1	5467
April	1st to 10th	Night	46% 6% 11% 23% 13% 2	2064
	11th to 20th	Night	49% 4 8% 23% 14% 2	1784
	21st to end	Night	49% 5% 11% 23% 11% 2	1800
May	1st to 10th	Night	35% 5% 12% 26% 20% 2	3998
	11th to 20th	Night	39% 6% 8% 23% 20% 5%	3597
	21st to end	Night	43% 7% 10% 25% 15% 1	3823
June	1st to 10th	Night	31% 7% 16% 33% 11% 2	1400
	11th to 20th	Night	35% 7% 15% 25% 14% 3	1400
	21st to end	Night	29% 7% 19% 29% 14% 2	1400
July	1st to 10th	Night	30% 8% 19% 30% 12%	3145
	11th to 20th	Night	21% 6% 20% 39% 12% 2	3138
	21st to end	Night	33% 8% 17% 31% 11% 1	3938
August	1st to 10th	Night	30% 6% 14% 31% 16% 2	2916
	11th to 20th	Night	31% 7% 16% 34% 11% 1	2915
	21st to end	Night	31% 7% 17% 31% 13% 1	3234
September	1st to 10th	Night	28% 6% 15% 35% 14% 1	1994
	11th to 20th	Night	31% 8% 18% 31% 13%	2170
	21st to end	Night	32% 5% 12% 34% 16%	2200
October	1st to 10th	Night	28% 4 9% 35% 20% 5%	3904
	11th to 20th	Night	39% 5% 9% 28% 18% 1	3899
	21st to end	Night	46% 5% 13% 25% 11%	4410
November	1st to 10th	Night	47% 7% 11% 23% 10% 2	2813
	11th to 20th	Night	56% 5% 13% 17% 9% 1	2940
	21st to end	Night	53% 7% 15% 19% 5% 1	2940
December	1st to 10th	Night	61% 6% 15% 13% 4	4720
	11th to 20th	Night	63% 5% 10% 17% 5%	5669
	21st to end	Night	71% 5% 8% 11% 4	7480

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	14% 12% 30% 29% 11% 3	300
	11th to 20th	Day	13% 10% 30% 36% 10%	300
	21st to end	Day	12% 8% 43% 20% 15% 3	330
February	1st to 10th	Day	16% 14% 39% 25% 6% 1	300
	11th to 20th	Day	14% 12% 41% 23% 10% 1	300
	21st to end	Day	10% 8% 43% 33% 5%	249
March	1st to 10th	Day	16% 13% 35% 27% 9% 1	300
	11th to 20th	Day	15% 11% 32% 28% 11% 3	300
	21st to end	Day	20% 10% 29% 26% 12% 3	330
April	1st to 10th	Day	21% 14% 31% 25% 9%	435
	11th to 20th	Day	23% 12% 31% 22% 11% 1	682
	21st to end	Day	23% 9% 31% 21% 15% 1	700
May	1st to 10th	Day	19% 11% 30% 25% 13% 2	703
	11th to 20th	Day	18% 10% 29% 27% 14% 2	725
	21st to end	Day	18% 6% 28% 30% 15% 3	789
June	1st to 10th	Day	12% 8% 26% 31% 20% 4	730
	11th to 20th	Day	15% 10% 36% 26% 12% 2	730
	21st to end	Day	12% 8% 29% 31% 17% 3	730
July	1st to 10th	Day	7% 4 22% 33% 29% 6%	721
	11th to 20th	Day	10% 7% 26% 29% 21% 7%	718
	21st to end	Day	7% 4 25% 34% 26% 5%	794
August	1st to 10th	Day	10% 4 22% 36% 23% 5%	726
	11th to 20th	Day	14% 5% 20% 32% 22% 8%	715
	21st to end	Day	10% 6% 27% 31% 21% 5%	803
September	1st to 10th	Day	10% 5% 30% 32% 18% 5%	535
	11th to 20th	Day	12% 7% 30% 34% 13% 5%	358
	21st to end	Day	16% 12% 31% 22% 15% 4	330
October	1st to 10th	Day	18% 9% 32% 27% 13% 1	330
	11th to 20th	Day	19% 15% 35% 23% 6% 1	330
	21st to end	Day	23% 15% 36% 18% 6% 2	363
November	1st to 10th	Day	22% 13% 31% 26% 7% 1	330
	11th to 20th	Day	17% 18% 40% 19% 5%	330
	21st to end	Day	16% 16% 36% 25% 6%	330
December	1st to 10th	Day	13% 10% 42% 25% 9% 2	330
	11th to 20th	Day	18% 13% 38% 26% 5%	321
	21st to end	Day	23% 9% 34% 28% 5% 1	330
January	1st to 10th	Night	9% 12% 37% 30% 9% 3	1000
	11th to 20th	Night	14% 11% 36% 31% 8% 1	1000
	21st to end	Night	14% 9% 39% 29% 7% 1	1100
February	1st to 10th	Night	12% 11% 36% 32% 8% 1	1000
	11th to 20th	Night	11% 9% 42% 27% 9% 2	979
	21st to end	Night	14% 9% 33% 31% 10% 3	782
March	1st to 10th	Night	15% 8% 36% 30% 9% 1	663
	11th to 20th	Night	14% 9% 43% 27% 7% 1	600
	21st to end	Night	22% 8% 29% 28% 11% 2	660
April	1st to 10th	Night	17% 9% 36% 31% 7% 1	600
	11th to 20th	Night	21% 13% 31% 25% 9% 1	593
	21st to end	Night	22% 7% 32% 27% 10% 1	600
May	1st to 10th	Night	18% 8% 31% 32% 11%	600
	11th to 20th	Night	17% 7% 34% 29% 11% 1	591
	21st to end	Night	15% 7% 31% 35% 12%	650
June	1st to 10th	Night	13% 6% 27% 36% 16% 1	600
	11th to 20th	Night	15% 5% 32% 40% 9%	600
	21st to end	Night	8% 4 28% 43% 16% 1	600
July	1st to 10th	Night	5% 3 22% 43% 23% 3	585
	11th to 20th	Night	7% 3 23% 47% 18% 2	582
	21st to end	Night	5% 2 23% 49% 19% 2	657
August	1st to 10th	Night	10% 2 17% 49% 19% 2	597
	11th to 20th	Night	11% 4 22% 39% 23% 3	594
	21st to end	Night	8% 4 28% 38% 19% 2	660
September	1st to 10th	Night	11% 6% 28% 37% 17% 2	600
	11th to 20th	Night	11% 5% 32% 36% 16% 2	600
	21st to end	Night	14% 7% 32% 33% 14% 1	600
October	1st to 10th	Night	18% 11% 31% 30% 10%	784
	11th to 20th	Night	20% 12% 32% 28% 7%	800
	21st to end	Night	23% 11% 35% 26% 6%	976
November	1st to 10th	Night	16% 12% 34% 30% 7%	1025
	11th to 20th	Night	17% 14% 33% 27% 7% 1	1050
	21st to end	Night	16% 14% 38% 26% 5%	1050
December	1st to 10th	Night	13% 12% 37% 29% 8% 1	1050
	11th to 20th	Night	16% 12% 38% 26% 6% 1	1036
	21st to end	Night	24% 8% 35% 24% 7% 1	1100

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