Starshine Farm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starshine Farm Observatory clear sky chart from 2005-11-06 to 2026-06-01.

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	17% 12% 5% 10% 5% 5% 4 4 5% 6% 28%	132216
	Night	17% 13% 5% 11% 5% 4 4 3 4 6% 28%	130926
Transparency	Day	57% 3 10% 19% 10% 1	135815
	Night	58% 3 10% 18% 10% 1	135397
Seeing	Day	26% 15% 28% 18% 9% 3	16569
	Night	25% 14% 27% 23% 10% 1	26243

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	18% 22% 8% 26% 6% 3 3 2 2 3 8%	5019
	11th to 20th	Day	11% 22% 10% 22% 9% 8% 3 2 2 3 9%	5280
	21st to end	Day	18% 17% 8% 14% 10% 8% 4 3 4 3 12%	5780
February	1st to 10th	Day	16% 19% 6% 15% 9% 5% 3 3 3 4 19%	1890
	11th to 20th	Day	15% 16% 9% 17% 8% 4 3 3 4 4 17%	1843
	21st to end	Day	17% 20% 4 13% 5% 4 4 3 4 4 21%	1695
March	1st to 10th	Day	18% 11% 7% 11% 5% 3 3 3 4 6% 28%	5045
	11th to 20th	Day	13% 14% 7% 10% 5% 4 4 3 4 5% 32%	5090
	21st to end	Day	20% 13% 5% 10% 5% 4 4 3 4 5% 27%	5586
April	1st to 10th	Day	18% 15% 3 8% 4 4 4 4 5% 6% 30%	2436
	11th to 20th	Day	19% 14% 3 6% 4 4 4 4 5% 5% 32%	2551
	21st to end	Day	20% 12% 4 6% 4 3 4 3 4 5% 34%	2730
May	1st to 10th	Day	23% 9% 3 8% 5% 5% 5% 4 5% 6% 27%	5992
	11th to 20th	Day	21% 10% 3 8% 5% 5% 4 4 6% 8% 27%	6051
	21st to end	Day	20% 8% 2 7% 5% 5% 5% 5% 6% 7% 32%	7088
June	1st to 10th	Day	16% 7% 3 6% 5% 5% 5% 4 6% 8% 34%	2800
	11th to 20th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 34%	2800
	21st to end	Day	15% 5% 2 6% 5% 5% 5% 4 7% 9% 36%	2800
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 4 7% 10% 38%	6360
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	5948
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	6424
August	1st to 10th	Day	16% 8% 3 8% 5% 5% 6% 4 7% 8% 30%	4234
	11th to 20th	Day	14% 7% 3 8% 5% 5% 6% 5% 7% 9% 30%	4174
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 9% 36%	4477
September	1st to 10th	Day	16% 8% 2 7% 5% 4 4 3 5% 6% 42%	2400
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 3 6% 8% 42%	2225
	21st to end	Day	23% 8% 3 8% 4 4 3 3 6% 7% 32%	2190
October	1st to 10th	Day	17% 7% 2 7% 4 4 5% 4 6% 7% 38%	2000
	11th to 20th	Day	21% 10% 4 8% 5% 4 5% 3 4 6% 31%	2000
	21st to end	Day	24% 13% 3 7% 4 4 5% 4 5% 6% 25%	2200
November	1st to 10th	Day	13% 12% 3 9% 4 5% 5% 4 5% 7% 33%	1942
	11th to 20th	Day	19% 17% 4 8% 6% 4 4 4 4 6% 25%	1688
	21st to end	Day	20% 22% 7% 9% 5% 3 4 3 5% 5% 17%	1680
December	1st to 10th	Day	20% 22% 15% 15% 4 4 3 2 3 3 10%	2680
	11th to 20th	Day	22% 22% 7% 11% 6% 3 3 3 4 4 15%	3070
	21st to end	Day	25% 24% 6% 13% 6% 3 3 2 3 4 11%	4048
January	1st to 10th	Night	15% 20% 9% 28% 6% 4 3 2 2 3 8%	7859
	11th to 20th	Night	12% 20% 10% 23% 9% 6% 5% 2 2 3 9%	7680
	21st to end	Night	18% 17% 8% 13% 8% 6% 5% 2 3 4 15%	8401
February	1st to 10th	Night	19% 17% 5% 12% 8% 5% 4 3 4 4 20%	2730
	11th to 20th	Night	17% 15% 7% 16% 7% 5% 4 3 5% 4 18%	2663
	21st to end	Night	19% 14% 5% 15% 6% 4 3 3 4 5% 21%	2103
March	1st to 10th	Night	20% 14% 6% 8% 7% 3 3 2 3 6% 27%	5028
	11th to 20th	Night	13% 13% 7% 8% 4 3 3 2 4 6% 36%	5090
	21st to end	Night	19% 12% 5% 9% 4 4 4 3 4 4 31%	5588
April	1st to 10th	Night	19% 15% 4 8% 4 4 4 3 5% 5% 28%	2184
	11th to 20th	Night	19% 11% 3 7% 4 4 4 4 5% 6% 33%	2035
	21st to end	Night	15% 10% 4 7% 5% 4 4 4 5% 7% 34%	1890
May	1st to 10th	Night	27% 11% 3 6% 4 4 3 3 4 6% 27%	4123
	11th to 20th	Night	20% 11% 3 7% 4 4 3 3 5% 6% 35%	4058
	21st to end	Night	20% 8% 2 5% 4 3 4 3 6% 8% 36%	4008
June	1st to 10th	Night	10% 7% 2 7% 6% 5% 5% 4 5% 8% 41%	1600
	11th to 20th	Night	13% 6% 3 6% 5% 4 4 4 6% 8% 41%	1600
	21st to end	Night	12% 7% 3 5% 5% 5% 4 4 6% 8% 42%	1600
July	1st to 10th	Night	13% 7% 3 7% 4 4 4 3 6% 8% 42%	3598
	11th to 20th	Night	11% 6% 2 7% 4 5% 4 5% 7% 10% 39%	4004
	21st to end	Night	9% 6% 2 6% 4 4 4 4 6% 8% 47%	4427
August	1st to 10th	Night	12% 9% 3 8% 4 5% 4 4 6% 7% 38%	2915
	11th to 20th	Night	16% 6% 3 7% 3 5% 4 4 6% 7% 40%	2875
	21st to end	Night	9% 6% 2 6% 5% 4 6% 4 7% 8% 43%	3387
September	1st to 10th	Night	13% 6% 2 5% 4 4 5% 3 5% 7% 47%	2000
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 6% 8% 52%	2172
	21st to end	Night	20% 8% 2 6% 5% 4 4 4 5% 7% 36%	2210
October	1st to 10th	Night	16% 7% 3 5% 3 4 4 3 5% 6% 44%	2400
	11th to 20th	Night	19% 8% 2 7% 5% 4 4 4 6% 7% 35%	2400
	21st to end	Night	25% 11% 3 6% 4 4 4 3 4 5% 31%	2640
November	1st to 10th	Night	14% 11% 3 6% 4 5% 3 3 5% 7% 38%	2573
	11th to 20th	Night	18% 17% 4 8% 5% 4 4 4 5% 6% 24%	2930
	21st to end	Night	20% 19% 6% 8% 5% 4 4 3 4 5% 21%	2940
December	1st to 10th	Night	17% 20% 12% 14% 5% 4 5% 3 4 4 13%	4720
	11th to 20th	Night	21% 21% 8% 12% 5% 4 3 2 3 4 17%	5345
	21st to end	Night	24% 21% 7% 11% 5% 4 4 2 4 5% 13%	7150

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	84% 2 6% 6% 3	5020
	11th to 20th	Day	84% 2 5% 7% 3	5280
	21st to end	Day	79% 1 7% 10% 4	5780
February	1st to 10th	Day	72% 3 7% 13% 6%	1890
	11th to 20th	Day	71% 3 7% 13% 6%	1852
	21st to end	Day	66% 4 10% 14% 5% 2	1695
March	1st to 10th	Day	58% 4 11% 21% 7%	5045
	11th to 20th	Day	55% 3 15% 20% 6% 2	5090
	21st to end	Day	59% 3 6% 19% 12% 1	5586
April	1st to 10th	Day	55% 4 12% 16% 12% 1	2436
	11th to 20th	Day	54% 4 10% 19% 12% 2	2551
	21st to end	Day	53% 4 9% 20% 11% 2	2730
May	1st to 10th	Day	58% 3 8% 20% 8% 3	6027
	11th to 20th	Day	55% 4 10% 21% 9% 1	6055
	21st to end	Day	51% 5% 11% 20% 12% 2	7103
June	1st to 10th	Day	47% 5% 12% 24% 12% 1	2800
	11th to 20th	Day	48% 5% 14% 19% 13% 1	2800
	21st to end	Day	43% 6% 12% 26% 13% 1	2800
July	1st to 10th	Day	41% 3 12% 27% 15% 2	6290
	11th to 20th	Day	45% 3 12% 25% 15% 1	5877
	21st to end	Day	41% 3 11% 25% 20% 1	6240
August	1st to 10th	Day	51% 5% 13% 22% 9%	4221
	11th to 20th	Day	49% 4 12% 26% 8% 1	4213
	21st to end	Day	43% 4 11% 29% 12% 1	4477
September	1st to 10th	Day	44% 5% 10% 24% 15% 2	2400
	11th to 20th	Day	40% 5% 13% 26% 15% 1	2225
	21st to end	Day	52% 4 11% 21% 11%	2190
October	1st to 10th	Day	39% 3 12% 28% 18% 1	3260
	11th to 20th	Day	48% 3 11% 22% 13% 4	3240
	21st to end	Day	47% 3 13% 25% 12% 1	3538
November	1st to 10th	Day	49% 5% 11% 20% 13% 2	1942
	11th to 20th	Day	60% 5% 10% 16% 7% 2	1688
	21st to end	Day	68% 4 10% 13% 4 1	1680
December	1st to 10th	Day	83% 2 7% 6% 2	2680
	11th to 20th	Day	73% 3 8% 14% 2	3066
	21st to end	Day	81% 2 8% 7% 2	4048
January	1st to 10th	Night	84% 2 5% 7% 2	7860
	11th to 20th	Night	84% 2 6% 6% 2	7680
	21st to end	Night	75% 1 7% 12% 4	8401
February	1st to 10th	Night	69% 3 8% 15% 5%	2730
	11th to 20th	Night	69% 3 9% 13% 5%	2665
	21st to end	Night	66% 3 8% 14% 8% 1	2103
March	1st to 10th	Night	61% 3 10% 19% 7% 1	5028
	11th to 20th	Night	51% 3 13% 22% 9% 2	5090
	21st to end	Night	56% 4 7% 17% 15% 1	5588
April	1st to 10th	Night	58% 5% 10% 16% 11% 1	2184
	11th to 20th	Night	52% 4 10% 19% 13% 2	2035
	21st to end	Night	48% 5% 11% 23% 11% 3	1890
May	1st to 10th	Night	59% 4 8% 15% 11% 4	4150
	11th to 20th	Night	51% 4 10% 23% 11% 1	4059
	21st to end	Night	45% 5% 12% 21% 14% 2	4015
June	1st to 10th	Night	40% 6% 12% 26% 15% 2	1600
	11th to 20th	Night	41% 5% 15% 22% 16% 2	1600
	21st to end	Night	39% 6% 14% 23% 17% 1	1600
July	1st to 10th	Night	42% 3 10% 26% 18% 1	3560
	11th to 20th	Night	40% 3 15% 29% 12% 1	3955
	21st to end	Night	36% 4 12% 21% 26% 1	4297
August	1st to 10th	Night	46% 5% 12% 25% 12% 1	2904
	11th to 20th	Night	43% 4 12% 32% 8% 1	2902
	21st to end	Night	37% 5% 14% 30% 12% 2	3387
September	1st to 10th	Night	37% 5% 11% 27% 17% 3	2000
	11th to 20th	Night	30% 6% 14% 29% 21% 1	2172
	21st to end	Night	49% 4 12% 20% 14% 1	2210
October	1st to 10th	Night	39% 3 8% 26% 24% 1	3920
	11th to 20th	Night	45% 3 12% 20% 16% 5%	3899
	21st to end	Night	42% 3 14% 23% 17% 1	4252
November	1st to 10th	Night	46% 4 12% 23% 12% 3	2573
	11th to 20th	Night	60% 4 10% 16% 7% 3	2930
	21st to end	Night	65% 4 11% 16% 4 1	2940
December	1st to 10th	Night	77% 3 10% 7% 3	4720
	11th to 20th	Night	73% 2 9% 13% 3	5348
	21st to end	Night	76% 3 9% 11% 2	7150

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	37% 23% 30% 7% 3	286
	11th to 20th	Day	39% 29% 24% 5% 2 1	330
	21st to end	Day	36% 29% 26% 7% 1	363
February	1st to 10th	Day	33% 25% 33% 8% 1	330
	11th to 20th	Day	41% 23% 29% 6% 1	330
	21st to end	Day	38% 26% 31% 5%	296
March	1st to 10th	Day	34% 22% 29% 13% 3	540
	11th to 20th	Day	34% 21% 31% 10% 2 1	540
	21st to end	Day	37% 20% 28% 12% 3 1	594
April	1st to 10th	Day	34% 19% 29% 14% 5% 1	540
	11th to 20th	Day	31% 18% 28% 14% 6% 2	532
	21st to end	Day	29% 18% 30% 17% 5% 1	540
May	1st to 10th	Day	31% 19% 26% 15% 5% 2	543
	11th to 20th	Day	25% 15% 29% 21% 8% 3	567
	21st to end	Day	21% 12% 29% 22% 12% 5%	617
June	1st to 10th	Day	20% 13% 31% 24% 8% 3	530
	11th to 20th	Day	22% 11% 28% 24% 14% 2	530
	21st to end	Day	18% 11% 33% 25% 10% 3	530
July	1st to 10th	Day	12% 8% 25% 28% 21% 6%	525
	11th to 20th	Day	15% 7% 28% 28% 14% 8%	524
	21st to end	Day	14% 7% 29% 29% 15% 6%	576
August	1st to 10th	Day	13% 8% 26% 27% 20% 7%	526
	11th to 20th	Day	19% 5% 24% 29% 14% 10%	519
	21st to end	Day	12% 8% 24% 31% 17% 7%	583
September	1st to 10th	Day	18% 10% 22% 26% 17% 7%	530
	11th to 20th	Day	12% 5% 22% 28% 25% 8%	530
	21st to end	Day	28% 9% 27% 18% 13% 4	530
October	1st to 10th	Day	18% 12% 27% 24% 16% 3	530
	11th to 20th	Day	26% 17% 32% 16% 6% 2	530
	21st to end	Day	34% 17% 28% 17% 4	583
November	1st to 10th	Day	26% 20% 32% 14% 6% 2	420
	11th to 20th	Day	41% 19% 26% 11% 3 1	223
	21st to end	Day	37% 18% 36% 9% 1	220
December	1st to 10th	Day	40% 28% 24% 4 3 1	220
	11th to 20th	Day	41% 19% 31% 9%	220
	21st to end	Day	37% 24% 30% 9% 1	242
January	1st to 10th	Night	31% 24% 31% 11% 2	840
	11th to 20th	Night	35% 23% 28% 12% 2	840
	21st to end	Night	29% 23% 32% 14% 2	924
February	1st to 10th	Night	33% 19% 29% 18% 1	840
	11th to 20th	Night	31% 23% 31% 14% 1	823
	21st to end	Night	30% 22% 33% 14% 2	692
March	1st to 10th	Night	28% 18% 34% 17% 3	840
	11th to 20th	Night	30% 20% 26% 19% 5%	840
	21st to end	Night	29% 17% 31% 18% 4 1	924
April	1st to 10th	Night	30% 17% 29% 19% 5%	840
	11th to 20th	Night	28% 15% 29% 21% 7% 1	791
	21st to end	Night	24% 9% 33% 28% 5% 1	630
May	1st to 10th	Night	26% 10% 23% 30% 10%	630
	11th to 20th	Night	21% 9% 27% 32% 9% 1	596
	21st to end	Night	16% 6% 28% 29% 18% 2	455
June	1st to 10th	Night	13% 4 33% 35% 15% 1	400
	11th to 20th	Night	15% 7% 23% 41% 14%	400
	21st to end	Night	12% 5% 27% 38% 17% 1	400
July	1st to 10th	Night	12% 3 19% 41% 21% 5%	390
	11th to 20th	Night	13% 3 19% 35% 26% 4	557
	21st to end	Night	13% 3 13% 42% 27% 1	657
August	1st to 10th	Night	11% 3 17% 40% 27% 3	597
	11th to 20th	Night	15% 3 12% 38% 27% 4	594
	21st to end	Night	15% 4 20% 31% 26% 4	759
September	1st to 10th	Night	16% 5% 21% 31% 25% 3	800
	11th to 20th	Night	12% 5% 17% 35% 28% 3	800
	21st to end	Night	24% 8% 23% 26% 17% 3	800
October	1st to 10th	Night	19% 8% 26% 26% 19% 2	800
	11th to 20th	Night	24% 12% 30% 24% 9% 1	800
	21st to end	Night	32% 12% 30% 22% 3	880
November	1st to 10th	Night	22% 15% 28% 26% 8% 1	820
	11th to 20th	Night	31% 18% 27% 17% 6% 1	840
	21st to end	Night	35% 16% 31% 15% 3	840
December	1st to 10th	Night	33% 22% 27% 14% 4	840
	11th to 20th	Night	32% 25% 26% 14% 4	840
	21st to end	Night	33% 21% 29% 15% 1	924

Page generated at 2026-05-29 01:53:27. Version ac07

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