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 2025-02-06.

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	17% 12% 5% 10% 5% 4 4 4 5% 6% 28%	108592
	Night	17% 13% 5% 10% 5% 4 4 3 4 6% 27%	109654
Transparency	Day	56% 4 10% 19% 10% 1	112235
	Night	57% 4 10% 18% 10% 1	114150
Seeing	Day	25% 15% 28% 19% 9% 3	14841
	Night	25% 14% 27% 23% 10% 1	24562

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	15% 22% 9% 26% 5% 3 3 2 2 3 10%	3871
	11th to 20th	Day	11% 23% 11% 21% 8% 7% 2 1 2 3 10%	4060
	21st to end	Day	21% 19% 9% 14% 7% 5% 4 2 3 3 12%	4466
February	1st to 10th	Day	17% 19% 6% 14% 9% 5% 3 2 2 4 19%	1755
	11th to 20th	Day	15% 16% 8% 16% 8% 4 3 3 4 4 18%	1663
	21st to end	Day	18% 19% 3 13% 5% 4 4 3 4 4 22%	1538
March	1st to 10th	Day	22% 12% 6% 9% 5% 3 3 4 4 7% 25%	3435
	11th to 20th	Day	12% 18% 6% 11% 5% 4 4 3 4 5% 29%	3480
	21st to end	Day	21% 12% 4 10% 5% 3 4 3 5% 6% 29%	3815
April	1st to 10th	Day	17% 15% 3 7% 4 4 4 4 5% 6% 31%	2204
	11th to 20th	Day	20% 13% 3 6% 4 4 4 4 5% 5% 33%	2305
	21st to end	Day	20% 12% 4 7% 4 4 4 3 4 5% 33%	2470
May	1st to 10th	Day	22% 10% 3 8% 5% 4 5% 4 5% 6% 29%	4082
	11th to 20th	Day	19% 10% 3 8% 5% 5% 4 4 6% 7% 28%	4126
	21st to end	Day	13% 6% 2 7% 5% 5% 4 4 6% 8% 40%	4823
June	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	2660
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 6% 8% 35%	2660
	21st to end	Day	16% 5% 2 5% 5% 5% 5% 4 7% 9% 36%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 10% 37%	4440
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 4 7% 9% 40%	4154
	21st to end	Day	11% 6% 3 6% 6% 5% 6% 5% 7% 8% 37%	4466
August	1st to 10th	Day	16% 8% 3 8% 5% 5% 5% 4 7% 8% 30%	4104
	11th to 20th	Day	14% 7% 3 8% 5% 5% 6% 5% 7% 9% 29%	4044
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 9% 37%	4340
September	1st to 10th	Day	16% 8% 2 7% 5% 4 4 3 5% 6% 41%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 3 6% 8% 40%	2114
	21st to end	Day	22% 8% 3 7% 4 5% 3 3 6% 7% 32%	2081
October	1st to 10th	Day	17% 7% 2 7% 5% 4 5% 4 6% 7% 35%	1900
	11th to 20th	Day	22% 10% 4 8% 5% 4 5% 3 4 6% 30%	1900
	21st to end	Day	24% 13% 4 7% 4 4 5% 4 5% 6% 24%	2090
November	1st to 10th	Day	13% 11% 3 9% 5% 5% 5% 4 5% 7% 34%	1848
	11th to 20th	Day	18% 17% 4 8% 5% 4 4 4 4 6% 25%	1608
	21st to end	Day	20% 22% 7% 9% 6% 3 4 3 5% 6% 17%	1600
December	1st to 10th	Day	20% 22% 15% 15% 4 4 3 2 2 3 10%	2600
	11th to 20th	Day	23% 22% 7% 10% 6% 3 3 3 4 4 15%	2990
	21st to end	Day	26% 25% 6% 12% 6% 3 3 2 3 4 11%	3960
January	1st to 10th	Night	15% 19% 10% 28% 6% 3 3 2 2 3 9%	6059
	11th to 20th	Night	13% 19% 10% 22% 8% 5% 5% 2 3 3 9%	5900
	21st to end	Night	21% 19% 9% 15% 7% 4 5% 2 3 3 13%	6490
February	1st to 10th	Night	20% 18% 5% 12% 8% 5% 4 3 4 4 19%	2536
	11th to 20th	Night	17% 15% 6% 15% 7% 5% 4 3 5% 4 18%	2403
	21st to end	Night	21% 13% 5% 15% 6% 4 3 3 4 5% 21%	1909
March	1st to 10th	Night	22% 14% 4 8% 5% 3 3 2 4 6% 28%	3418
	11th to 20th	Night	17% 16% 8% 8% 4 4 3 2 4 6% 28%	3480
	21st to end	Night	18% 12% 4 9% 4 4 3 2 4 5% 35%	3817
April	1st to 10th	Night	17% 15% 4 8% 4 4 4 4 5% 5% 30%	1976
	11th to 20th	Night	19% 11% 3 7% 4 3 4 3 5% 6% 34%	1839
	21st to end	Night	16% 11% 4 6% 4 4 4 5% 5% 7% 34%	1710
May	1st to 10th	Night	26% 9% 3 6% 4 4 3 4 5% 6% 30%	2813
	11th to 20th	Night	18% 12% 3 7% 4 4 4 3 6% 7% 34%	2763
	21st to end	Night	12% 6% 2 5% 4 3 4 4 6% 10% 43%	2732
June	1st to 10th	Night	10% 6% 2 7% 6% 5% 6% 4 6% 8% 41%	1520
	11th to 20th	Night	12% 6% 3 6% 5% 4 4 4 6% 8% 42%	1520
	21st to end	Night	12% 7% 3 5% 5% 5% 4 4 6% 8% 41%	1520
July	1st to 10th	Night	12% 7% 3 8% 4 4 4 3 6% 7% 41%	2520
	11th to 20th	Night	10% 6% 2 6% 3 4 4 4 6% 10% 45%	2801
	21st to end	Night	10% 6% 2 7% 5% 4 4 4 7% 8% 43%	3087
August	1st to 10th	Night	13% 9% 3 8% 4 5% 4 4 6% 7% 37%	2825
	11th to 20th	Night	16% 6% 2 6% 3 5% 4 4 6% 7% 40%	2785
	21st to end	Night	9% 6% 2 6% 5% 5% 6% 5% 7% 8% 43%	3283
September	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 6% 8% 51%	2063
	21st to end	Night	20% 8% 2 6% 5% 4 3 3 5% 7% 36%	2099
October	1st to 10th	Night	17% 8% 3 6% 3 4 4 3 5% 6% 43%	2280
	11th to 20th	Night	20% 8% 2 7% 5% 4 4 4 6% 7% 34%	2280
	21st to end	Night	25% 11% 3 6% 4 4 4 4 4 5% 30%	2508
November	1st to 10th	Night	14% 11% 3 6% 4 5% 3 3 5% 7% 38%	2447
	11th to 20th	Night	18% 17% 4 8% 5% 5% 4 4 5% 6% 25%	2790
	21st to end	Night	20% 19% 5% 8% 5% 4 4 3 4 6% 21%	2800
December	1st to 10th	Night	17% 20% 12% 14% 5% 4 4 3 4 4 12%	4580
	11th to 20th	Night	22% 21% 9% 11% 5% 4 3 2 3 4 16%	5205
	21st to end	Night	24% 21% 7% 11% 5% 4 4 2 4 5% 13%	6996

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	82% 2 5% 7% 4	3872
	11th to 20th	Day	83% 2 5% 8% 2	4060
	21st to end	Day	79% 2 7% 9% 3	4466
February	1st to 10th	Day	73% 3 7% 12% 6%	1755
	11th to 20th	Day	70% 4 7% 13% 6%	1672
	21st to end	Day	65% 4 10% 14% 5% 2	1538
March	1st to 10th	Day	58% 5% 9% 23% 4	3435
	11th to 20th	Day	58% 4 15% 17% 5% 1	3480
	21st to end	Day	56% 4 8% 19% 12% 1	3815
April	1st to 10th	Day	55% 4 12% 17% 12% 1	2204
	11th to 20th	Day	53% 4 10% 19% 12% 2	2305
	21st to end	Day	54% 4 9% 19% 11% 2	2470
May	1st to 10th	Day	56% 4 9% 23% 8% 1	4120
	11th to 20th	Day	54% 5% 12% 20% 8% 1	4130
	21st to end	Day	41% 6% 14% 22% 14% 3	4837
June	1st to 10th	Day	47% 6% 12% 23% 11% 1	2660
	11th to 20th	Day	47% 5% 14% 20% 13% 1	2660
	21st to end	Day	43% 6% 11% 26% 12% 1	2660
July	1st to 10th	Day	42% 4 12% 25% 16% 2	4370
	11th to 20th	Day	41% 4 11% 27% 17% 1	4083
	21st to end	Day	43% 4 14% 21% 17% 1	4324
August	1st to 10th	Day	52% 5% 12% 22% 8%	4091
	11th to 20th	Day	49% 4 12% 26% 8% 1	4083
	21st to end	Day	43% 4 12% 29% 12% 1	4340
September	1st to 10th	Day	44% 5% 11% 23% 15% 2	2280
	11th to 20th	Day	41% 6% 12% 25% 15% 1	2114
	21st to end	Day	52% 4 11% 21% 11%	2081
October	1st to 10th	Day	40% 3 12% 27% 18% 1	3160
	11th to 20th	Day	48% 3 11% 22% 12% 4	3140
	21st to end	Day	46% 3 13% 25% 12% 1	3428
November	1st to 10th	Day	48% 5% 11% 20% 14% 2	1848
	11th to 20th	Day	59% 5% 11% 16% 7% 2	1608
	21st to end	Day	68% 5% 10% 13% 4 1	1600
December	1st to 10th	Day	84% 2 7% 6% 1	2600
	11th to 20th	Day	73% 3 7% 14% 2	2986
	21st to end	Day	81% 2 8% 8% 2	3960
January	1st to 10th	Night	82% 2 5% 8% 2	6059
	11th to 20th	Night	82% 3 7% 7% 2	5900
	21st to end	Night	78% 2 7% 8% 4 1	6490
February	1st to 10th	Night	70% 3 9% 14% 5%	2536
	11th to 20th	Night	68% 3 9% 14% 5%	2405
	21st to end	Night	66% 3 9% 14% 8% 1	1909
March	1st to 10th	Night	59% 4 9% 22% 6%	3418
	11th to 20th	Night	59% 4 13% 16% 7% 1	3480
	21st to end	Night	51% 5% 7% 22% 14% 2	3817
April	1st to 10th	Night	55% 5% 10% 17% 12% 1	1976
	11th to 20th	Night	50% 4 11% 19% 13% 2	1839
	21st to end	Night	48% 5% 11% 22% 11% 3	1710
May	1st to 10th	Night	55% 5% 10% 19% 10% 2	2840
	11th to 20th	Night	50% 5% 12% 22% 10% 1	2764
	21st to end	Night	35% 6% 16% 23% 16% 4	2739
June	1st to 10th	Night	39% 7% 12% 26% 14% 2	1520
	11th to 20th	Night	39% 6% 15% 23% 16% 2	1520
	21st to end	Night	40% 7% 13% 23% 17% 1	1520
July	1st to 10th	Night	44% 4 11% 22% 18% 2	2480
	11th to 20th	Night	36% 3 14% 30% 16% 2	2749
	21st to end	Night	40% 5% 13% 19% 23% 1	2988
August	1st to 10th	Night	47% 5% 11% 25% 11% 1	2814
	11th to 20th	Night	43% 4 12% 32% 8%	2812
	21st to end	Night	37% 5% 14% 30% 12% 2	3283
September	1st to 10th	Night	38% 5% 11% 26% 17% 3	1900
	11th to 20th	Night	30% 6% 13% 28% 22% 1	2063
	21st to end	Night	49% 4 12% 20% 14% 1	2099
October	1st to 10th	Night	40% 3 8% 25% 23% 1	3800
	11th to 20th	Night	45% 3 12% 20% 15% 5%	3779
	21st to end	Night	42% 3 14% 24% 17% 1	4120
November	1st to 10th	Night	46% 4 12% 22% 12% 3	2447
	11th to 20th	Night	59% 5% 9% 17% 7% 3	2790
	21st to end	Night	64% 4 11% 16% 4 1	2800
December	1st to 10th	Night	77% 3 10% 7% 2	4580
	11th to 20th	Night	73% 2 9% 13% 2	5208
	21st to end	Night	76% 3 9% 11% 2	6996

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% 29% 8% 3	260
	11th to 20th	Day	37% 28% 26% 6% 2 1	300
	21st to end	Day	35% 29% 28% 7% 1	330
February	1st to 10th	Day	35% 25% 33% 6%	285
	11th to 20th	Day	38% 26% 29% 7% 1	270
	21st to end	Day	39% 25% 30% 6%	246
March	1st to 10th	Day	34% 21% 28% 14% 3	460
	11th to 20th	Day	32% 21% 33% 10% 2 2	460
	21st to end	Day	38% 20% 26% 13% 3 1	506
April	1st to 10th	Day	30% 20% 29% 14% 5% 1	460
	11th to 20th	Day	30% 18% 28% 14% 7% 3	452
	21st to end	Day	29% 18% 30% 16% 5% 1	460
May	1st to 10th	Day	30% 17% 27% 17% 6% 2	463
	11th to 20th	Day	23% 15% 29% 21% 9% 3	487
	21st to end	Day	17% 10% 31% 24% 13% 6%	529
June	1st to 10th	Day	20% 12% 31% 25% 9% 3	490
	11th to 20th	Day	20% 10% 28% 25% 15% 2	490
	21st to end	Day	19% 11% 34% 24% 9% 3	490
July	1st to 10th	Day	12% 8% 26% 27% 21% 7%	485
	11th to 20th	Day	14% 7% 29% 28% 14% 8%	484
	21st to end	Day	15% 8% 29% 28% 15% 5%	532
August	1st to 10th	Day	14% 8% 25% 25% 19% 8%	486
	11th to 20th	Day	19% 6% 25% 27% 14% 9%	479
	21st to end	Day	12% 8% 24% 32% 16% 8%	539
September	1st to 10th	Day	18% 9% 24% 27% 17% 6%	490
	11th to 20th	Day	13% 5% 23% 29% 22% 8%	490
	21st to end	Day	28% 10% 28% 18% 12% 4	490
October	1st to 10th	Day	19% 12% 28% 23% 15% 3	490
	11th to 20th	Day	27% 18% 31% 17% 6% 2	490
	21st to end	Day	35% 17% 28% 17% 4	539
November	1st to 10th	Day	25% 19% 33% 15% 7% 2	386
	11th to 20th	Day	39% 20% 26% 11% 2 1	203
	21st to end	Day	35% 19% 37% 9% 1	200
December	1st to 10th	Day	39% 29% 23% 4 4 2	200
	11th to 20th	Day	40% 19% 33% 9%	200
	21st to end	Day	35% 24% 31% 9% 1	220
January	1st to 10th	Night	31% 24% 31% 11% 2	800
	11th to 20th	Night	35% 22% 29% 13% 2	800
	21st to end	Night	28% 23% 33% 14% 2	880
February	1st to 10th	Night	34% 19% 28% 18% 1	781
	11th to 20th	Night	31% 24% 31% 13% 1	743
	21st to end	Night	31% 22% 31% 14% 2	628
March	1st to 10th	Night	27% 18% 34% 18% 3	760
	11th to 20th	Night	29% 20% 26% 19% 5% 1	760
	21st to end	Night	28% 17% 31% 19% 5% 1	836
April	1st to 10th	Night	28% 16% 30% 20% 6%	760
	11th to 20th	Night	28% 14% 29% 21% 8% 1	715
	21st to end	Night	24% 9% 34% 27% 5% 1	570
May	1st to 10th	Night	24% 10% 24% 31% 11%	570
	11th to 20th	Night	20% 9% 28% 33% 10% 1	538
	21st to end	Night	13% 6% 27% 31% 20% 2	411
June	1st to 10th	Night	13% 4 33% 35% 15% 1	380
	11th to 20th	Night	15% 7% 22% 42% 15%	380
	21st to end	Night	12% 5% 28% 39% 16% 1	380
July	1st to 10th	Night	12% 3 19% 41% 21% 5%	370
	11th to 20th	Night	13% 3 19% 35% 26% 4	528
	21st to end	Night	13% 3 13% 42% 26% 1	624
August	1st to 10th	Night	12% 3 16% 39% 27% 3	567
	11th to 20th	Night	15% 3 13% 39% 26% 4	564
	21st to end	Night	15% 4 20% 30% 26% 4	721
September	1st to 10th	Night	16% 6% 20% 29% 25% 3	760
	11th to 20th	Night	13% 6% 18% 34% 27% 4	760
	21st to end	Night	24% 8% 23% 26% 16% 4	760
October	1st to 10th	Night	19% 9% 27% 25% 18% 2	760
	11th to 20th	Night	25% 13% 29% 23% 9% 1	760
	21st to end	Night	32% 13% 30% 22% 4	836
November	1st to 10th	Night	21% 15% 28% 27% 8% 1	780
	11th to 20th	Night	31% 18% 27% 17% 7% 1	800
	21st to end	Night	34% 17% 31% 15% 3	800
December	1st to 10th	Night	34% 23% 26% 14% 4	800
	11th to 20th	Night	32% 24% 27% 14% 4	800
	21st to end	Night	33% 21% 29% 16% 1	880

Page generated at 2025-02-03 03:05:50. Version ac07

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