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 2024-01-27.

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% 11% 5% 8% 6% 3 5% 5% 5% 7% 29%	74750
	Night	17% 12% 5% 8% 6% 3 4 4 5% 6% 30%	75298
Transparency	Day	55% 5% 11% 18% 9% 1	74464
	Night	55% 5% 11% 18% 10% 1	75103
Seeing	Day	25% 15% 28% 19% 9% 3	13517
	Night	25% 14% 27% 23% 10% 1	23245

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% 19% 10% 12% 10% 3 5% 3 3 4 14%	1629
	11th to 20th	Day	18% 20% 8% 13% 9% 3 4 3 3 4 14%	1710
	21st to end	Day	16% 19% 10% 16% 9% 4 4 3 3 4 11%	1836
February	1st to 10th	Day	18% 17% 8% 13% 10% 4 4 3 2 4 17%	1620
	11th to 20th	Day	16% 14% 10% 14% 9% 3 4 4 4 4 17%	1573
	21st to end	Day	19% 18% 4 12% 6% 4 4 3 4 5% 21%	1449
March	1st to 10th	Day	18% 12% 7% 10% 7% 2 4 5% 5% 7% 24%	1980
	11th to 20th	Day	18% 14% 6% 9% 6% 3 4 4 4 6% 27%	1980
	21st to end	Day	21% 12% 5% 8% 6% 3 4 3 4 5% 27%	2178
April	1st to 10th	Day	17% 13% 5% 7% 4 3 4 4 5% 6% 32%	2088
	11th to 20th	Day	20% 12% 4 5% 4 3 4 5% 5% 5% 33%	2182
	21st to end	Day	21% 12% 5% 6% 4 3 4 4 3 5% 33%	2340
May	1st to 10th	Day	19% 10% 3 8% 6% 3 5% 5% 6% 7% 28%	2340
	11th to 20th	Day	21% 9% 4 7% 6% 3 4 5% 5% 7% 30%	2318
	21st to end	Day	13% 6% 2 5% 6% 4 6% 5% 7% 8% 37%	2725
June	1st to 10th	Day	16% 6% 3 5% 6% 4 6% 5% 6% 8% 34%	2520
	11th to 20th	Day	15% 7% 3 6% 6% 3 5% 4 6% 8% 35%	2520
	21st to end	Day	16% 5% 2 5% 5% 3 6% 6% 6% 9% 36%	2520
July	1st to 10th	Day	11% 6% 3 6% 5% 3 6% 5% 6% 10% 39%	2520
	11th to 20th	Day	13% 6% 3 5% 6% 3 6% 5% 7% 9% 37%	2360
	21st to end	Day	12% 5% 3 5% 7% 4 6% 6% 7% 10% 33%	2547
August	1st to 10th	Day	10% 6% 3 6% 6% 4 6% 6% 8% 8% 37%	2327
	11th to 20th	Day	13% 8% 3 8% 7% 3 7% 6% 7% 8% 31%	2303
	21st to end	Day	13% 6% 2 5% 6% 4 6% 7% 6% 9% 35%	2466
September	1st to 10th	Day	17% 8% 3 6% 6% 3 4 4 5% 6% 39%	2160
	11th to 20th	Day	14% 6% 2 5% 6% 3 5% 5% 6% 8% 39%	2003
	21st to end	Day	21% 8% 3 7% 5% 4 4 4 6% 7% 34%	1972
October	1st to 10th	Day	18% 7% 2 6% 6% 3 5% 6% 5% 7% 34%	1800
	11th to 20th	Day	23% 10% 5% 7% 6% 3 5% 4 4 6% 29%	1800
	21st to end	Day	26% 12% 4 6% 5% 3 5% 5% 5% 6% 23%	1980
November	1st to 10th	Day	13% 11% 4 9% 6% 3 5% 5% 5% 7% 34%	1754
	11th to 20th	Day	20% 15% 5% 7% 6% 3 4 5% 4 6% 26%	1528
	21st to end	Day	21% 20% 7% 8% 6% 2 4 4 5% 6% 18%	1520
December	1st to 10th	Day	20% 23% 10% 9% 5% 4 4 3 3 4 13%	1520
	11th to 20th	Day	19% 19% 9% 13% 5% 3 4 5% 4 5% 15%	1910
	21st to end	Day	27% 24% 8% 10% 6% 2 3 3 2 3 11%	2772
January	1st to 10th	Night	19% 18% 9% 13% 8% 3 4 4 3 4 15%	2535
	11th to 20th	Night	21% 18% 9% 13% 7% 4 4 3 3 4 15%	2470
	21st to end	Night	16% 21% 10% 12% 9% 3 4 3 3 4 14%	2664
February	1st to 10th	Night	20% 15% 7% 11% 9% 4 4 4 4 4 18%	2340
	11th to 20th	Night	18% 14% 7% 14% 7% 4 5% 4 5% 4 18%	2273
	21st to end	Night	21% 12% 7% 14% 7% 4 3 3 4 5% 21%	1800
March	1st to 10th	Night	16% 11% 8% 9% 7% 4 4 5% 5% 6% 26%	1980
	11th to 20th	Night	18% 12% 6% 7% 6% 3 4 3 4 6% 30%	1980
	21st to end	Night	19% 14% 4 8% 5% 3 4 3 4 5% 29%	2178
April	1st to 10th	Night	17% 14% 4 7% 4 3 5% 4 5% 6% 30%	1872
	11th to 20th	Night	18% 10% 3 6% 5% 2 4 5% 5% 6% 35%	1741
	21st to end	Night	16% 10% 4 6% 5% 4 4 5% 5% 8% 33%	1620
May	1st to 10th	Night	19% 8% 3 6% 6% 4 5% 6% 5% 7% 33%	1620
	11th to 20th	Night	15% 10% 4 7% 6% 3 4 4 5% 7% 36%	1571
	21st to end	Night	10% 6% 3 4 5% 3 4 5% 5% 10% 43%	1550
June	1st to 10th	Night	10% 5% 3 5% 6% 4 6% 5% 6% 9% 41%	1440
	11th to 20th	Night	12% 5% 3 5% 7% 3 5% 5% 5% 8% 42%	1440
	21st to end	Night	12% 6% 3 5% 5% 4 5% 5% 6% 8% 42%	1440
July	1st to 10th	Night	8% 5% 3 6% 5% 3 4 4 6% 7% 48%	1440
	11th to 20th	Night	9% 6% 2 5% 5% 4 4 5% 5% 9% 48%	1595
	21st to end	Night	11% 5% 2 5% 6% 3 5% 5% 7% 9% 42%	1771
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 6% 7% 8% 46%	1611
	11th to 20th	Night	11% 6% 2 5% 4 3 4 6% 8% 9% 42%	1598
	21st to end	Night	12% 5% 2 4 4 3 4 5% 7% 8% 46%	1871
September	1st to 10th	Night	14% 6% 2 5% 5% 3 4 4 5% 7% 46%	1800
	11th to 20th	Night	12% 4 2 4 4 3 4 4 6% 8% 50%	1954
	21st to end	Night	18% 7% 3 5% 6% 3 4 4 5% 7% 38%	1988
October	1st to 10th	Night	17% 7% 3 5% 4 3 4 4 5% 6% 42%	2160
	11th to 20th	Night	20% 8% 3 6% 6% 3 4 5% 6% 7% 33%	2160
	21st to end	Night	27% 11% 4 5% 5% 3 4 4 4 5% 29%	2376
November	1st to 10th	Night	14% 10% 4 6% 4 3 4 4 5% 7% 38%	2321
	11th to 20th	Night	18% 16% 4 7% 5% 4 4 4 5% 6% 25%	2650
	21st to end	Night	20% 18% 6% 7% 6% 3 5% 4 4 6% 22%	2660
December	1st to 10th	Night	22% 19% 9% 10% 7% 3 4 4 3 4 15%	2660
	11th to 20th	Night	18% 20% 8% 11% 7% 3 4 3 4 4 18%	3285
	21st to end	Night	26% 22% 8% 9% 6% 3 4 3 3 4 10%	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	75% 3 9% 10% 4	1630
	11th to 20th	Day	76% 3 9% 10% 2	1710
	21st to end	Day	78% 3 7% 9% 3 1	1836
February	1st to 10th	Day	75% 3 7% 10% 5%	1620
	11th to 20th	Day	71% 3 7% 12% 6%	1582
	21st to end	Day	66% 4 10% 14% 5% 2	1449
March	1st to 10th	Day	59% 5% 11% 18% 6%	1980
	11th to 20th	Day	60% 4 9% 17% 8% 2	1980
	21st to end	Day	60% 3 7% 18% 11% 1	2178
April	1st to 10th	Day	54% 4 12% 18% 12% 1	2088
	11th to 20th	Day	53% 4 10% 19% 12% 2	2182
	21st to end	Day	55% 4 9% 19% 11% 2	2340
May	1st to 10th	Day	54% 5% 11% 19% 10% 2	2340
	11th to 20th	Day	55% 5% 10% 16% 12% 2	2322
	21st to end	Day	42% 8% 16% 23% 11% 1	2725
June	1st to 10th	Day	47% 6% 12% 23% 11% 1	2520
	11th to 20th	Day	47% 5% 14% 20% 13% 1	2520
	21st to end	Day	43% 6% 11% 27% 12% 1	2520
July	1st to 10th	Day	40% 6% 12% 24% 15% 2	2450
	11th to 20th	Day	42% 6% 13% 24% 14% 1	2289
	21st to end	Day	43% 6% 14% 21% 15% 1	2405
August	1st to 10th	Day	41% 7% 14% 28% 9%	2314
	11th to 20th	Day	48% 7% 15% 20% 9% 2	2303
	21st to end	Day	43% 7% 11% 23% 13% 2	2466
September	1st to 10th	Day	46% 5% 11% 22% 14% 3	2160
	11th to 20th	Day	42% 6% 12% 25% 14% 1	2003
	21st to end	Day	50% 5% 12% 22% 11%	1972
October	1st to 10th	Day	48% 5% 14% 20% 12% 1	1800
	11th to 20th	Day	57% 5% 11% 19% 7% 1	1800
	21st to end	Day	62% 5% 11% 14% 8% 1	1980
November	1st to 10th	Day	49% 5% 11% 18% 14% 2	1754
	11th to 20th	Day	59% 5% 11% 16% 7% 2	1528
	21st to end	Day	66% 5% 10% 14% 4 1	1520
December	1st to 10th	Day	76% 3 9% 9% 2	1520
	11th to 20th	Day	71% 5% 9% 13% 2	1906
	21st to end	Day	81% 2 8% 8% 1	2772
January	1st to 10th	Night	74% 3 8% 11% 5%	2535
	11th to 20th	Night	74% 4 9% 10% 2	2470
	21st to end	Night	75% 3 7% 11% 4 1	2664
February	1st to 10th	Night	71% 3 9% 13% 4	2340
	11th to 20th	Night	69% 3 9% 14% 5%	2275
	21st to end	Night	66% 3 8% 14% 8% 1	1800
March	1st to 10th	Night	59% 5% 8% 19% 9%	1980
	11th to 20th	Night	57% 4 9% 19% 10% 1	1980
	21st to end	Night	57% 4 5% 18% 13% 2	2178
April	1st to 10th	Night	54% 5% 11% 18% 12% 1	1872
	11th to 20th	Night	50% 4 10% 19% 14% 3	1741
	21st to end	Night	49% 5% 11% 21% 11% 3	1620
May	1st to 10th	Night	49% 6% 10% 19% 12% 3	1620
	11th to 20th	Night	47% 6% 10% 19% 15% 2	1572
	21st to end	Night	37% 7% 17% 23% 15% 2	1551
June	1st to 10th	Night	39% 7% 13% 26% 15% 2	1440
	11th to 20th	Night	40% 6% 14% 22% 16% 2	1440
	21st to end	Night	39% 7% 13% 23% 17% 1	1440
July	1st to 10th	Night	37% 6% 11% 25% 19% 3	1400
	11th to 20th	Night	34% 6% 13% 26% 19% 3	1543
	21st to end	Night	37% 7% 16% 22% 18% 1	1672
August	1st to 10th	Night	35% 6% 14% 30% 14% 1	1600
	11th to 20th	Night	36% 7% 17% 27% 13% 1	1598
	21st to end	Night	34% 7% 16% 25% 15% 3	1871
September	1st to 10th	Night	39% 5% 12% 25% 16% 3	1800
	11th to 20th	Night	31% 6% 14% 28% 21% 1	1954
	21st to end	Night	47% 4 12% 21% 15% 1	1988
October	1st to 10th	Night	43% 5% 13% 22% 16% 1	2160
	11th to 20th	Night	49% 5% 14% 21% 10% 1	2160
	21st to end	Night	58% 4 11% 16% 9% 2	2376
November	1st to 10th	Night	46% 5% 12% 22% 12% 3	2321
	11th to 20th	Night	59% 5% 10% 17% 7% 3	2650
	21st to end	Night	63% 4 11% 16% 4 1	2660
December	1st to 10th	Night	73% 4 10% 9% 3	2660
	11th to 20th	Night	71% 3 11% 12% 3	3288
	21st to end	Night	79% 3 9% 7% 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	35% 24% 30% 8% 4	234
	11th to 20th	Day	37% 27% 27% 6% 2 1	270
	21st to end	Day	35% 30% 27% 6% 1	282
February	1st to 10th	Day	36% 25% 34% 5%	240
	11th to 20th	Day	40% 25% 29% 6%	240
	21st to end	Day	39% 26% 29% 6%	217
March	1st to 10th	Day	34% 22% 28% 13% 3	420
	11th to 20th	Day	31% 20% 34% 10% 3 2	420
	21st to end	Day	37% 19% 26% 13% 3 1	462
April	1st to 10th	Day	30% 20% 29% 15% 6% 1	420
	11th to 20th	Day	29% 18% 28% 14% 8% 3	412
	21st to end	Day	30% 19% 29% 16% 5% 1	420
May	1st to 10th	Day	31% 17% 27% 16% 7% 2	423
	11th to 20th	Day	24% 15% 30% 22% 7% 3	447
	21st to end	Day	17% 10% 29% 23% 14% 6%	485
June	1st to 10th	Day	19% 13% 31% 25% 9% 3	450
	11th to 20th	Day	22% 11% 27% 24% 15% 2	450
	21st to end	Day	18% 11% 33% 25% 10% 3	450
July	1st to 10th	Day	12% 7% 24% 27% 22% 7%	445
	11th to 20th	Day	14% 6% 29% 29% 14% 8%	444
	21st to end	Day	15% 8% 29% 28% 15% 5%	488
August	1st to 10th	Day	13% 7% 25% 26% 21% 9%	446
	11th to 20th	Day	19% 5% 24% 28% 15% 10%	439
	21st to end	Day	13% 8% 24% 31% 17% 7%	495
September	1st to 10th	Day	19% 8% 23% 27% 17% 6%	450
	11th to 20th	Day	13% 5% 24% 28% 22% 8%	450
	21st to end	Day	24% 10% 29% 18% 14% 5%	450
October	1st to 10th	Day	19% 12% 28% 23% 15% 3	450
	11th to 20th	Day	27% 18% 32% 16% 6% 1	450
	21st to end	Day	37% 16% 27% 17% 3	495
November	1st to 10th	Day	25% 18% 32% 16% 8% 2	352
	11th to 20th	Day	41% 19% 24% 12% 3 1	183
	21st to end	Day	33% 20% 37% 9% 1	180
December	1st to 10th	Day	38% 29% 22% 4 4 2	180
	11th to 20th	Day	37% 21% 34% 9%	180
	21st to end	Day	35% 25% 31% 8% 1	198
January	1st to 10th	Night	31% 23% 32% 11% 3	760
	11th to 20th	Night	35% 20% 29% 13% 2	760
	21st to end	Night	29% 22% 33% 15% 2	820
February	1st to 10th	Night	35% 19% 29% 16% 1	720
	11th to 20th	Night	31% 23% 31% 13% 1	703
	21st to end	Night	32% 22% 31% 14% 2	592
March	1st to 10th	Night	26% 19% 34% 17% 3	720
	11th to 20th	Night	29% 19% 26% 20% 5% 1	720
	21st to end	Night	28% 16% 30% 19% 5% 1	792
April	1st to 10th	Night	27% 17% 30% 20% 6%	720
	11th to 20th	Night	27% 14% 29% 21% 8% 1	677
	21st to end	Night	24% 9% 35% 25% 5% 1	540
May	1st to 10th	Night	24% 10% 24% 31% 11%	540
	11th to 20th	Night	20% 9% 29% 33% 9% 1	510
	21st to end	Night	13% 5% 29% 30% 21% 3	389
June	1st to 10th	Night	12% 3 33% 36% 15% 1	360
	11th to 20th	Night	16% 7% 22% 40% 15%	360
	21st to end	Night	12% 5% 28% 40% 15% 1	360
July	1st to 10th	Night	11% 3 19% 41% 22% 5%	350
	11th to 20th	Night	13% 3 20% 34% 26% 4	499
	21st to end	Night	14% 3 14% 42% 26% 1	591
August	1st to 10th	Night	11% 3 16% 40% 27% 3	537
	11th to 20th	Night	14% 3 12% 40% 27% 4	534
	21st to end	Night	15% 4 20% 29% 27% 5%	683
September	1st to 10th	Night	17% 5% 20% 30% 25% 3	720
	11th to 20th	Night	13% 6% 19% 33% 26% 4	720
	21st to end	Night	21% 8% 24% 26% 17% 4	720
October	1st to 10th	Night	20% 8% 26% 26% 17% 3	720
	11th to 20th	Night	25% 13% 29% 23% 8% 1	720
	21st to end	Night	34% 13% 29% 21% 3	792
November	1st to 10th	Night	21% 15% 27% 27% 9% 1	740
	11th to 20th	Night	30% 18% 27% 17% 7% 1	760
	21st to end	Night	33% 17% 32% 15% 3	760
December	1st to 10th	Night	34% 22% 26% 14% 4	760
	11th to 20th	Night	31% 24% 27% 14% 4	760
	21st to end	Night	34% 21% 29% 15% 1	836

Page generated at 2024-01-24 09:37:28. Version ac07

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