Farpoint Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Farpoint 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	11% 6% 2 6% 4 4 4 3 5% 7% 47%	126573
	Night	10% 6% 2 6% 4 3 4 3 5% 6% 51%	124375
Transparency	Day	35% 6% 11% 26% 19% 4	130211
	Night	33% 5% 11% 26% 21% 4	128800
Seeing	Day	14% 10% 31% 28% 14% 3	17118
	Night	13% 10% 34% 32% 10% 1	26972

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	14% 8% 3 9% 5% 4 4 3 5% 7% 38%	4077
	11th to 20th	Day	6% 8% 4 10% 6% 8% 5% 3 4 5% 42%	4080
	21st to end	Day	8% 9% 5% 10% 5% 4 3 3 4 5% 45%	4488
February	1st to 10th	Day	12% 10% 4 9% 5% 4 3 3 4 7% 40%	1800
	11th to 20th	Day	9% 9% 3 9% 4 4 4 3 6% 6% 42%	1830
	21st to end	Day	8% 10% 2 5% 4 4 4 4 5% 7% 48%	1651
March	1st to 10th	Day	10% 7% 2 5% 3 3 3 2 4 6% 54%	4936
	11th to 20th	Day	8% 6% 2 5% 3 3 3 3 5% 6% 57%	4980
	21st to end	Day	11% 8% 4 7% 5% 5% 4 3 5% 7% 39%	5462
April	1st to 10th	Day	13% 6% 2 5% 4 3 3 4 5% 6% 48%	2240
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 6% 6% 42%	2420
	21st to end	Day	17% 7% 2 6% 5% 5% 4 3 5% 7% 38%	2600
May	1st to 10th	Day	15% 8% 2 6% 3 3 4 3 4 5% 45%	5862
	11th to 20th	Day	12% 5% 2 5% 4 3 4 3 5% 6% 50%	5862
	21st to end	Day	19% 5% 2 5% 4 4 4 3 6% 7% 40%	6434
June	1st to 10th	Day	6% 4 2 4 4 4 4 4 7% 10% 51%	2600
	11th to 20th	Day	8% 5% 2 5% 5% 5% 4 4 6% 7% 50%	2600
	21st to end	Day	6% 3 1 5% 4 4 5% 4 7% 8% 52%	2600
July	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 4 7% 8% 45%	5900
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 47%	5900
	21st to end	Day	7% 5% 2 5% 5% 5% 6% 6% 7% 10% 44%	6422
August	1st to 10th	Day	6% 5% 2 5% 4 4 4 3 5% 8% 53%	4234
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 5% 7% 48%	4171
	21st to end	Day	6% 4 1 4 4 4 4 4 5% 8% 55%	4520
September	1st to 10th	Day	12% 4 2 5% 3 3 4 3 5% 7% 53%	2298
	11th to 20th	Day	9% 4 2 6% 5% 4 5% 3 4 8% 49%	2200
	21st to end	Day	8% 4 2 6% 3 4 4 4 5% 5% 54%	2200
October	1st to 10th	Day	10% 5% 2 6% 3 4 3 4 6% 6% 54%	2053
	11th to 20th	Day	9% 6% 2 4 3 3 3 2 3 5% 59%	2000
	21st to end	Day	15% 6% 2 5% 3 3 3 3 5% 5% 51%	2200
November	1st to 10th	Day	8% 5% 1 4 3 4 3 3 5% 7% 57%	1963
	11th to 20th	Day	10% 5% 2 5% 3 4 3 3 5% 5% 57%	1890
	21st to end	Day	14% 6% 3 5% 3 3 3 3 4 5% 51%	1813
December	1st to 10th	Day	6% 4 2 4 4 3 4 3 5% 7% 58%	2626
	11th to 20th	Day	8% 6% 3 7% 4 4 4 2 3 5% 53%	3173
	21st to end	Day	17% 11% 7% 13% 5% 4 4 2 4 5% 28%	4488
January	1st to 10th	Night	11% 9% 3 13% 6% 5% 3 3 4 5% 37%	5888
	11th to 20th	Night	6% 6% 3 7% 4 5% 6% 4 4 5% 49%	5900
	21st to end	Night	12% 9% 4 8% 4 3 3 2 4 4 47%	6490
February	1st to 10th	Night	9% 12% 3 7% 4 4 4 4 5% 6% 41%	2600
	11th to 20th	Night	11% 9% 3 7% 4 4 4 3 5% 5% 45%	2473
	21st to end	Night	9% 7% 2 5% 5% 4 4 3 4 5% 51%	1977
March	1st to 10th	Night	11% 6% 2 6% 3 3 3 2 3 5% 56%	4919
	11th to 20th	Night	7% 4 1 4 3 3 4 3 6% 7% 58%	4980
	21st to end	Night	12% 7% 3 7% 4 4 4 3 5% 7% 43%	5467
April	1st to 10th	Night	11% 5% 2 6% 4 3 3 3 5% 7% 52%	2160
	11th to 20th	Night	12% 8% 2 6% 4 3 4 3 5% 6% 48%	1927
	21st to end	Night	16% 7% 2 5% 3 4 4 4 5% 6% 44%	1800
May	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 5% 6% 47%	4053
	11th to 20th	Night	13% 6% 2 4 3 3 3 2 4 6% 52%	4053
	21st to end	Night	18% 5% 2 4 3 2 4 3 5% 7% 49%	4443
June	1st to 10th	Night	5% 3 1 4 4 3 3 4 8% 8% 56%	1800
	11th to 20th	Night	6% 3 2 4 4 4 4 4 6% 10% 53%	1800
	21st to end	Night	5% 3 1 4 3 3 5% 3 7% 8% 59%	1800
July	1st to 10th	Night	8% 5% 2 5% 4 3 4 3 6% 7% 54%	4078
	11th to 20th	Night	5% 4 2 4 4 4 4 4 6% 9% 54%	4077
	21st to end	Night	8% 4 2 6% 3 4 5% 4 7% 10% 48%	4449
August	1st to 10th	Night	2 2 1 4 4 5% 5% 4 6% 9% 57%	2926
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 3 5% 7% 51%	2888
	21st to end	Night	5% 3 1 4 3 4 3 2 5% 8% 61%	3384
September	1st to 10th	Night	11% 5% 1 4 3 3 3 3 4 6% 57%	2098
	11th to 20th	Night	8% 5% 1 5% 3 3 5% 3 5% 7% 56%	2200
	21st to end	Night	7% 4 2 4 4 3 3 3 5% 5% 60%	2200
October	1st to 10th	Night	11% 5% 2 4 4 3 4 2 5% 6% 55%	2325
	11th to 20th	Night	11% 5% 2 4 3 2 3 2 4 5% 59%	2400
	21st to end	Night	14% 7% 2 4 3 3 2 3 4 5% 53%	2640
November	1st to 10th	Night	8% 4 1 4 3 3 3 3 4 5% 61%	2551
	11th to 20th	Night	8% 5% 2 4 3 3 4 3 4 7% 57%	2730
	21st to end	Night	12% 6% 2 4 3 3 3 3 4 5% 54%	2798
December	1st to 10th	Night	5% 5% 2 5% 3 3 3 3 5% 5% 60%	4609
	11th to 20th	Night	9% 6% 3 6% 4 4 4 4 5% 6% 49%	5002
	21st to end	Night	16% 11% 5% 10% 5% 4 3 3 4 5% 35%	6490

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	44% 7% 11% 23% 13% 1	4078
	11th to 20th	Day	45% 4 12% 19% 17% 3	4080
	21st to end	Day	44% 4 11% 21% 18% 3	4488
February	1st to 10th	Day	47% 4 12% 23% 10% 3	1800
	11th to 20th	Day	42% 5% 11% 25% 14% 3	1839
	21st to end	Day	35% 6% 10% 26% 18% 5%	1651
March	1st to 10th	Day	33% 3 9% 20% 24% 11%	4936
	11th to 20th	Day	28% 4 9% 21% 28% 10%	4980
	21st to end	Day	44% 5% 14% 29% 7% 1	5464
April	1st to 10th	Day	36% 6% 12% 23% 20% 3	2240
	11th to 20th	Day	41% 6% 12% 22% 17% 2	2420
	21st to end	Day	46% 7% 10% 25% 11% 1	2600
May	1st to 10th	Day	41% 6% 9% 24% 18% 2	5900
	11th to 20th	Day	33% 6% 10% 21% 24% 5%	5866
	21st to end	Day	42% 7% 11% 25% 14% 1	6447
June	1st to 10th	Day	25% 10% 16% 30% 16% 2	2600
	11th to 20th	Day	31% 8% 13% 28% 19% 2	2600
	21st to end	Day	27% 7% 16% 28% 18% 5%	2600
July	1st to 10th	Day	33% 6% 11% 25% 21% 3	5836
	11th to 20th	Day	32% 6% 13% 28% 18% 3	5831
	21st to end	Day	32% 7% 13% 32% 14% 2	6240
August	1st to 10th	Day	29% 6% 11% 27% 22% 4	4220
	11th to 20th	Day	35% 6% 15% 26% 17% 2	4210
	21st to end	Day	26% 6% 15% 29% 18% 6%	4519
September	1st to 10th	Day	30% 6% 12% 25% 20% 7%	2298
	11th to 20th	Day	33% 7% 11% 25% 21% 3	2200
	21st to end	Day	30% 7% 8% 27% 25% 3	2200
October	1st to 10th	Day	21% 3 8% 20% 40% 8%	3339
	11th to 20th	Day	19% 2 5% 29% 33% 11%	3240
	21st to end	Day	30% 4 9% 26% 26% 5%	3538
November	1st to 10th	Day	27% 5% 12% 30% 20% 6%	1963
	11th to 20th	Day	30% 4 9% 28% 24% 4	1890
	21st to end	Day	37% 4 10% 27% 21% 2	1813
December	1st to 10th	Day	26% 4 12% 39% 19% 1	2626
	11th to 20th	Day	36% 4 10% 34% 16% 1	3171
	21st to end	Day	59% 4 8% 20% 8% 1	4488
January	1st to 10th	Night	49% 5% 9% 23% 12% 1	5888
	11th to 20th	Night	37% 5% 10% 24% 21% 4	5900
	21st to end	Night	42% 3 11% 18% 18% 7%	6490
February	1st to 10th	Night	43% 6% 12% 22% 14% 4	2600
	11th to 20th	Night	40% 5% 11% 25% 16% 3	2474
	21st to end	Night	35% 5% 9% 22% 21% 8%	1977
March	1st to 10th	Night	33% 3 7% 25% 27% 6%	4919
	11th to 20th	Night	24% 5% 7% 20% 34% 10%	4980
	21st to end	Night	40% 7% 14% 27% 10% 2	5467
April	1st to 10th	Night	33% 5% 11% 23% 23% 5%	2160
	11th to 20th	Night	36% 5% 10% 25% 19% 4	1927
	21st to end	Night	40% 7% 13% 23% 15% 2	1800
May	1st to 10th	Night	37% 7% 11% 24% 18% 3	4080
	11th to 20th	Night	33% 5% 10% 25% 20% 7%	4054
	21st to end	Night	35% 6% 12% 28% 18% 1	4452
June	1st to 10th	Night	23% 8% 19% 31% 17% 3	1800
	11th to 20th	Night	26% 7% 14% 32% 17% 3	1800
	21st to end	Night	21% 6% 14% 34% 20% 4	1800
July	1st to 10th	Night	30% 6% 13% 24% 23% 4	4035
	11th to 20th	Night	26% 6% 13% 31% 22% 2	4026
	21st to end	Night	30% 6% 13% 35% 15% 1	4320
August	1st to 10th	Night	23% 5% 18% 25% 21% 7%	2916
	11th to 20th	Night	33% 6% 14% 26% 20% 2	2915
	21st to end	Night	22% 5% 14% 34% 20% 5%	3384
September	1st to 10th	Night	29% 5% 12% 26% 20% 8%	2098
	11th to 20th	Night	28% 5% 11% 27% 23% 5%	2200
	21st to end	Night	27% 6% 8% 25% 31% 5%	2200
October	1st to 10th	Night	21% 3 6% 18% 45% 7%	3806
	11th to 20th	Night	20% 3 5% 28% 31% 13%	3899
	21st to end	Night	30% 4 8% 28% 28% 3	4252
November	1st to 10th	Night	27% 5% 10% 28% 24% 7%	2551
	11th to 20th	Night	27% 5% 10% 28% 24% 5%	2730
	21st to end	Night	34% 3 11% 28% 20% 4	2798
December	1st to 10th	Night	26% 4 14% 34% 21% 1	4609
	11th to 20th	Night	36% 4 11% 29% 18% 3	5003
	21st to end	Night	53% 4 9% 24% 9% 1	6490

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	18% 15% 36% 23% 9%	300
	11th to 20th	Day	20% 19% 41% 17% 3	300
	21st to end	Day	9% 13% 50% 24% 2	330
February	1st to 10th	Day	21% 18% 40% 17% 3	300
	11th to 20th	Day	18% 17% 44% 14% 6%	300
	21st to end	Day	15% 23% 45% 12% 4	249
March	1st to 10th	Day	15% 18% 45% 19% 3	300
	11th to 20th	Day	25% 14% 38% 18% 5%	300
	21st to end	Day	25% 21% 40% 12% 3	330
April	1st to 10th	Day	23% 20% 34% 18% 5%	340
	11th to 20th	Day	19% 17% 39% 20% 5% 1	538
	21st to end	Day	22% 18% 34% 18% 8%	700
May	1st to 10th	Day	18% 15% 36% 22% 9% 1	703
	11th to 20th	Day	19% 13% 27% 26% 12% 2	725
	21st to end	Day	17% 9% 32% 25% 13% 3	789
June	1st to 10th	Day	6% 4 25% 36% 23% 6%	730
	11th to 20th	Day	9% 4 30% 37% 15% 4	730
	21st to end	Day	6% 8% 36% 36% 12% 1	730
July	1st to 10th	Day	10% 3 18% 34% 27% 8%	721
	11th to 20th	Day	4 2 21% 43% 22% 7%	718
	21st to end	Day	7% 3 19% 39% 28% 5%	794
August	1st to 10th	Day	9% 2 23% 36% 27% 3	726
	11th to 20th	Day	9% 3 18% 42% 24% 4	715
	21st to end	Day	11% 3 15% 35% 30% 6%	713
September	1st to 10th	Day	14% 1 18% 40% 22% 4	428
	11th to 20th	Day	6% 3 26% 36% 25% 3	330
	21st to end	Day	12% 6% 29% 34% 17% 3	330
October	1st to 10th	Day	13% 5% 34% 28% 13% 6%	330
	11th to 20th	Day	8% 19% 40% 25% 8%	330
	21st to end	Day	23% 17% 33% 21% 6% 1	363
November	1st to 10th	Day	13% 16% 39% 24% 5% 2	330
	11th to 20th	Day	15% 17% 37% 23% 7% 2	330
	21st to end	Day	20% 14% 38% 18% 10%	330
December	1st to 10th	Day	10% 13% 43% 25% 7% 2	306
	11th to 20th	Day	14% 18% 40% 21% 6% 1	300
	21st to end	Day	20% 19% 38% 22% 1	330
January	1st to 10th	Night	12% 14% 40% 28% 7%	1000
	11th to 20th	Night	14% 14% 40% 26% 5% 1	1000
	21st to end	Night	12% 13% 42% 29% 4	1100
February	1st to 10th	Night	16% 14% 43% 25% 3	1000
	11th to 20th	Night	16% 15% 39% 27% 3	919
	21st to end	Night	12% 16% 45% 22% 5%	657
March	1st to 10th	Night	13% 14% 43% 25% 5%	600
	11th to 20th	Night	17% 12% 40% 26% 5% 1	600
	21st to end	Night	23% 13% 37% 22% 4	660
April	1st to 10th	Night	13% 16% 42% 23% 6%	600
	11th to 20th	Night	19% 16% 36% 25% 4	593
	21st to end	Night	19% 13% 39% 23% 6% 1	600
May	1st to 10th	Night	18% 9% 34% 34% 6% 1	600
	11th to 20th	Night	15% 11% 30% 33% 11%	591
	21st to end	Night	13% 8% 30% 32% 14% 2	650
June	1st to 10th	Night	5% 4 27% 42% 21% 2	600
	11th to 20th	Night	7% 3 30% 44% 16%	600
	21st to end	Night	5% 6% 35% 44% 10% 1	600
July	1st to 10th	Night	8% 2 17% 46% 26% 1	585
	11th to 20th	Night	3 2 20% 48% 23% 3	582
	21st to end	Night	7% 2 16% 47% 26% 1	657
August	1st to 10th	Night	5% 2 21% 47% 24% 2	597
	11th to 20th	Night	7% 3 15% 50% 25% 1	594
	21st to end	Night	7% 1 17% 45% 29% 2	660
September	1st to 10th	Night	13% 4 22% 41% 19% 3	600
	11th to 20th	Night	9% 2 27% 38% 21% 2	600
	21st to end	Night	8% 4 26% 41% 20% 1	600
October	1st to 10th	Night	13% 5% 29% 37% 16% 1	725
	11th to 20th	Night	14% 9% 41% 28% 7%	800
	21st to end	Night	19% 11% 35% 25% 9%	880
November	1st to 10th	Night	10% 11% 35% 32% 11% 1	911
	11th to 20th	Night	11% 14% 39% 29% 7%	1050
	21st to end	Night	16% 11% 36% 30% 6%	1050
December	1st to 10th	Night	13% 13% 37% 31% 6% 1	1011
	11th to 20th	Night	16% 12% 40% 28% 4	1000
	21st to end	Night	17% 15% 37% 28% 3	1100

Page generated at 2025-11-30 00:00:55. Version ac07

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