Field of Dreams Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Field of Dreams Observatory clear sky chart from 2005-11-06 to 2026-04-02.

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	15% 11% 4 9% 6% 5% 5% 4 5% 7% 29%	131172
	Night	16% 12% 5% 10% 5% 5% 4 3 5% 6% 30%	130642
Transparency	Day	53% 5% 11% 20% 11% 1	134791
	Night	54% 5% 10% 19% 11% 1	135080
Seeing	Day	22% 14% 28% 20% 11% 4	16378
	Night	21% 12% 28% 26% 11% 1	26277

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	16% 21% 7% 22% 7% 4 4 2 3 4 11%	5258
	11th to 20th	Day	11% 21% 8% 18% 10% 6% 4 2 3 4 12%	5280
	21st to end	Day	18% 17% 8% 13% 10% 8% 3 3 3 3 14%	5780
February	1st to 10th	Day	18% 18% 4 12% 8% 4 3 2 4 4 23%	1890
	11th to 20th	Day	16% 15% 7% 14% 7% 4 4 3 4 5% 21%	1864
	21st to end	Day	18% 14% 4 11% 6% 5% 4 3 6% 5% 23%	1730
March	1st to 10th	Day	17% 12% 7% 11% 5% 4 4 3 4 5% 28%	5000
	11th to 20th	Day	12% 10% 4 9% 5% 5% 4 3 4 6% 36%	5090
	21st to end	Day	20% 11% 4 10% 5% 5% 4 3 4 6% 28%	5586
April	1st to 10th	Day	16% 14% 4 7% 6% 4 4 3 5% 8% 29%	2278
	11th to 20th	Day	17% 13% 3 7% 4 4 4 4 5% 6% 33%	2486
	21st to end	Day	20% 11% 3 7% 5% 4 3 4 4 6% 34%	2600
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 5% 4 5% 6% 28%	5862
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 8% 30%	5861
	21st to end	Day	18% 7% 2 7% 5% 5% 5% 4 6% 7% 33%	6652
June	1st to 10th	Day	15% 7% 3 7% 6% 5% 5% 4 6% 9% 34%	2800
	11th to 20th	Day	14% 7% 3 7% 6% 5% 5% 4 6% 8% 35%	2800
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 9% 38%	2800
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 5% 4 7% 10% 41%	5998
	11th to 20th	Day	11% 6% 2 8% 5% 5% 6% 5% 8% 9% 35%	5900
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	6424
August	1st to 10th	Day	15% 7% 3 8% 5% 6% 5% 5% 7% 8% 32%	4234
	11th to 20th	Day	12% 6% 2 7% 5% 6% 6% 5% 7% 10% 33%	4174
	21st to end	Day	9% 5% 2 7% 5% 6% 6% 5% 7% 9% 39%	4543
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 4 5% 6% 45%	2340
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 6% 9% 43%	2200
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 3 5% 6% 35%	2200
October	1st to 10th	Day	15% 7% 2 7% 5% 4 4 3 6% 7% 40%	2038
	11th to 20th	Day	18% 10% 2 7% 5% 5% 4 4 5% 6% 34%	2000
	21st to end	Day	22% 12% 3 7% 5% 5% 3 3 4 7% 29%	2200
November	1st to 10th	Day	12% 9% 3 7% 5% 5% 5% 3 5% 6% 39%	1897
	11th to 20th	Day	17% 16% 3 8% 5% 4 5% 3 4 6% 28%	1811
	21st to end	Day	17% 17% 7% 10% 5% 5% 4 3 5% 5% 22%	1680
December	1st to 10th	Day	20% 16% 7% 14% 6% 4 4 3 4 4 18%	2680
	11th to 20th	Day	22% 19% 7% 11% 4 4 3 3 4 5% 18%	3070
	21st to end	Day	23% 24% 7% 14% 5% 4 3 2 3 4 11%	4166
January	1st to 10th	Night	14% 20% 7% 23% 7% 4 4 3 3 4 11%	7635
	11th to 20th	Night	11% 18% 9% 17% 10% 6% 6% 3 4 4 13%	7680
	21st to end	Night	17% 16% 7% 12% 7% 6% 5% 2 3 4 19%	8401
February	1st to 10th	Night	20% 14% 5% 12% 7% 5% 4 3 4 6% 22%	2730
	11th to 20th	Night	17% 13% 6% 12% 7% 5% 5% 3 4 5% 21%	2637
	21st to end	Night	19% 15% 5% 11% 5% 5% 4 3 5% 4 24%	2076
March	1st to 10th	Night	22% 13% 5% 9% 4 3 3 2 3 5% 30%	5061
	11th to 20th	Night	14% 11% 5% 7% 4 4 4 3 5% 6% 37%	5090
	21st to end	Night	17% 12% 3 9% 5% 4 4 3 4 5% 34%	5588
April	1st to 10th	Night	17% 13% 4 7% 5% 5% 3 4 4 6% 32%	2144
	11th to 20th	Night	16% 10% 3 8% 4 6% 5% 3 5% 7% 33%	1880
	21st to end	Night	16% 9% 3 7% 3 4 4 4 6% 8% 36%	1800
May	1st to 10th	Night	26% 10% 3 7% 4 5% 4 3 5% 6% 26%	4033
	11th to 20th	Night	16% 9% 3 7% 5% 4 3 3 5% 8% 37%	4032
	21st to end	Night	17% 7% 2 5% 4 4 4 4 6% 9% 38%	4197
June	1st to 10th	Night	9% 8% 2 7% 6% 5% 4 4 5% 7% 44%	1600
	11th to 20th	Night	10% 6% 2 8% 5% 4 4 4 6% 9% 41%	1600
	21st to end	Night	9% 5% 2 7% 5% 5% 4 6% 7% 8% 42%	1600
July	1st to 10th	Night	11% 6% 3 6% 5% 4 4 4 5% 9% 43%	3954
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 5% 7% 9% 40%	4057
	21st to end	Night	8% 6% 2 7% 4 5% 4 4 6% 8% 46%	4427
August	1st to 10th	Night	12% 8% 3 8% 4 5% 5% 4 5% 8% 38%	2915
	11th to 20th	Night	13% 8% 3 6% 4 4 4 3 5% 6% 44%	2875
	21st to end	Night	8% 4 2 7% 5% 5% 5% 4 7% 7% 44%	3322
September	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 4 7% 50%	2056
	11th to 20th	Night	10% 5% 2 4 3 3 4 3 5% 7% 53%	2200
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 7% 39%	2200
October	1st to 10th	Night	15% 4 2 5% 5% 4 4 3 5% 7% 46%	2360
	11th to 20th	Night	16% 7% 3 8% 5% 5% 4 3 5% 7% 37%	2400
	21st to end	Night	23% 8% 2 6% 4 4 4 3 5% 7% 35%	2640
November	1st to 10th	Night	14% 9% 2 6% 4 4 4 3 5% 6% 43%	2616
	11th to 20th	Night	16% 14% 4 9% 5% 4 4 3 5% 5% 30%	2804
	21st to end	Night	20% 16% 5% 8% 5% 3 4 3 4 6% 26%	2940
December	1st to 10th	Night	16% 16% 7% 14% 7% 5% 4 3 4 5% 18%	4720
	11th to 20th	Night	19% 20% 7% 11% 5% 4 3 3 4 5% 19%	5345
	21st to end	Night	22% 20% 7% 11% 5% 4 4 3 4 4 14%	7027

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	78% 3 7% 9% 3	5259
	11th to 20th	Day	77% 3 7% 9% 5%	5280
	21st to end	Day	76% 2 7% 12% 3	5780
February	1st to 10th	Day	67% 2 9% 14% 7%	1890
	11th to 20th	Day	66% 5% 8% 14% 7%	1873
	21st to end	Day	61% 4 11% 16% 7% 1	1730
March	1st to 10th	Day	58% 4 10% 21% 7%	5000
	11th to 20th	Day	50% 4 12% 25% 8% 2	5090
	21st to end	Day	57% 3 8% 18% 12% 1	5586
April	1st to 10th	Day	55% 4 11% 18% 12% 1	2278
	11th to 20th	Day	52% 5% 11% 18% 12% 2	2486
	21st to end	Day	52% 5% 10% 21% 11% 2	2600
May	1st to 10th	Day	55% 6% 10% 16% 9% 4	5897
	11th to 20th	Day	51% 6% 11% 21% 11% 1	5865
	21st to end	Day	47% 6% 13% 20% 12% 3	6667
June	1st to 10th	Day	45% 5% 13% 24% 12% 1	2800
	11th to 20th	Day	46% 5% 13% 22% 13% 1	2800
	21st to end	Day	39% 7% 14% 25% 14% 1	2800
July	1st to 10th	Day	37% 6% 13% 27% 15% 2	5933
	11th to 20th	Day	40% 8% 13% 24% 14%	5831
	21st to end	Day	39% 7% 11% 22% 19% 2	6240
August	1st to 10th	Day	47% 7% 13% 22% 11%	4221
	11th to 20th	Day	42% 8% 12% 28% 9% 1	4213
	21st to end	Day	38% 8% 13% 28% 12% 2	4543
September	1st to 10th	Day	39% 5% 11% 24% 18% 3	2340
	11th to 20th	Day	37% 6% 13% 26% 17% 2	2200
	21st to end	Day	48% 5% 10% 23% 13% 1	2200
October	1st to 10th	Day	33% 5% 12% 29% 20% 1	3311
	11th to 20th	Day	47% 5% 10% 20% 14% 4	3240
	21st to end	Day	42% 4 12% 26% 15% 1	3538
November	1st to 10th	Day	45% 4 11% 23% 16% 1	1897
	11th to 20th	Day	57% 4 10% 18% 8% 2	1811
	21st to end	Day	63% 5% 10% 15% 6% 1	1680
December	1st to 10th	Day	68% 5% 12% 12% 3	2680
	11th to 20th	Day	69% 4 10% 13% 5%	3066
	21st to end	Day	79% 3 8% 8% 2	4166
January	1st to 10th	Night	77% 4 8% 9% 3	7636
	11th to 20th	Night	76% 3 8% 9% 4	7680
	21st to end	Night	70% 3 8% 13% 6% 1	8401
February	1st to 10th	Night	65% 4 9% 16% 6%	2730
	11th to 20th	Night	64% 4 9% 16% 6%	2639
	21st to end	Night	63% 4 9% 14% 9% 1	2076
March	1st to 10th	Night	59% 3 11% 19% 8%	5061
	11th to 20th	Night	46% 4 14% 24% 9% 2	5090
	21st to end	Night	52% 4 10% 18% 14% 1	5588
April	1st to 10th	Night	53% 4 10% 18% 12% 2	2144
	11th to 20th	Night	50% 5% 12% 17% 14% 2	1880
	21st to end	Night	45% 4 12% 20% 16% 2	1800
May	1st to 10th	Night	59% 5% 8% 15% 10% 4	4060
	11th to 20th	Night	47% 5% 9% 24% 13% 1	4033
	21st to end	Night	42% 6% 12% 25% 12% 2	4204
June	1st to 10th	Night	39% 6% 11% 24% 17% 2	1600
	11th to 20th	Night	39% 5% 14% 23% 16% 2	1600
	21st to end	Night	37% 7% 14% 23% 18% 1	1600
July	1st to 10th	Night	39% 6% 11% 24% 19% 2	3911
	11th to 20th	Night	37% 8% 16% 26% 12% 1	4006
	21st to end	Night	35% 7% 12% 19% 26% 2	4297
August	1st to 10th	Night	43% 6% 11% 25% 13% 1	2904
	11th to 20th	Night	40% 6% 11% 28% 14% 1	2902
	21st to end	Night	35% 7% 12% 29% 13% 2	3322
September	1st to 10th	Night	34% 6% 10% 27% 19% 4	2056
	11th to 20th	Night	29% 5% 14% 28% 22% 2	2200
	21st to end	Night	45% 3 12% 22% 17% 1	2200
October	1st to 10th	Night	33% 4 9% 28% 25% 1	3854
	11th to 20th	Night	40% 6% 11% 22% 15% 6%	3899
	21st to end	Night	37% 4 9% 30% 18% 2	4252
November	1st to 10th	Night	42% 4 11% 25% 16% 3	2616
	11th to 20th	Night	56% 4 10% 19% 9% 3	2804
	21st to end	Night	60% 4 12% 18% 5% 1	2940
December	1st to 10th	Night	68% 5% 11% 12% 3	4720
	11th to 20th	Night	69% 4 10% 15% 2	5348
	21st to end	Night	73% 4 10% 11% 2	7027

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	31% 26% 31% 9% 3	330
	11th to 20th	Day	34% 27% 31% 6% 2	330
	21st to end	Day	31% 29% 29% 9% 2	363
February	1st to 10th	Day	31% 23% 35% 10% 2	330
	11th to 20th	Day	32% 29% 28% 10% 1	330
	21st to end	Day	28% 31% 35% 7%	273
March	1st to 10th	Day	26% 22% 34% 15% 3	519
	11th to 20th	Day	30% 19% 32% 12% 5% 1	540
	21st to end	Day	34% 19% 27% 15% 3 1	594
April	1st to 10th	Day	27% 21% 28% 16% 7% 1	504
	11th to 20th	Day	30% 16% 26% 16% 9% 3	492
	21st to end	Day	25% 15% 35% 17% 6% 1	500
May	1st to 10th	Day	27% 18% 27% 17% 8% 3	503
	11th to 20th	Day	24% 13% 29% 22% 9% 4	527
	21st to end	Day	16% 10% 27% 24% 19% 5%	573
June	1st to 10th	Day	16% 9% 32% 27% 12% 4	530
	11th to 20th	Day	18% 9% 26% 28% 14% 5%	530
	21st to end	Day	14% 9% 30% 28% 15% 5%	530
July	1st to 10th	Day	14% 5% 20% 26% 24% 11%	525
	11th to 20th	Day	12% 8% 24% 30% 18% 7%	524
	21st to end	Day	12% 4 27% 28% 21% 9%	576
August	1st to 10th	Day	12% 8% 21% 28% 21% 10%	526
	11th to 20th	Day	15% 7% 21% 26% 21% 9%	519
	21st to end	Day	10% 5% 24% 28% 23% 10%	583
September	1st to 10th	Day	14% 8% 22% 24% 22% 10%	530
	11th to 20th	Day	9% 3 18% 33% 24% 13%	530
	21st to end	Day	24% 10% 23% 24% 12% 7%	530
October	1st to 10th	Day	14% 10% 26% 26% 18% 5%	530
	11th to 20th	Day	20% 15% 36% 18% 8% 2	530
	21st to end	Day	30% 16% 31% 18% 5%	583
November	1st to 10th	Day	21% 19% 33% 17% 8% 2	375
	11th to 20th	Day	33% 19% 27% 16% 4 1	289
	21st to end	Day	29% 22% 36% 13%	220
December	1st to 10th	Day	30% 26% 31% 7% 4 1	220
	11th to 20th	Day	32% 20% 33% 12% 3	220
	21st to end	Day	37% 22% 27% 12% 1	270
January	1st to 10th	Night	26% 21% 34% 15% 3	840
	11th to 20th	Night	31% 20% 31% 14% 4	840
	21st to end	Night	28% 20% 29% 20% 3	924
February	1st to 10th	Night	29% 16% 33% 21% 2	840
	11th to 20th	Night	27% 18% 37% 17% 2	823
	21st to end	Night	29% 17% 35% 17% 2	692
March	1st to 10th	Night	25% 16% 34% 22% 3	840
	11th to 20th	Night	26% 17% 30% 21% 5% 1	840
	21st to end	Night	25% 15% 32% 22% 5% 1	924
April	1st to 10th	Night	23% 17% 31% 23% 6%	805
	11th to 20th	Night	23% 12% 33% 23% 8% 1	696
	21st to end	Night	18% 11% 34% 29% 7%	600
May	1st to 10th	Night	23% 9% 27% 32% 9% 1	600
	11th to 20th	Night	19% 7% 24% 36% 12% 2	591
	21st to end	Night	12% 3 24% 36% 22% 3	555
June	1st to 10th	Night	9% 7% 28% 41% 15% 1	400
	11th to 20th	Night	10% 4 27% 44% 15% 1	400
	21st to end	Night	11% 5% 26% 37% 21% 1	400
July	1st to 10th	Night	7% 3 17% 40% 27% 5%	533
	11th to 20th	Night	10% 3 19% 38% 27% 4	582
	21st to end	Night	11% 2 16% 40% 29% 2	657
August	1st to 10th	Night	9% 4 14% 44% 28% 2	597
	11th to 20th	Night	14% 3 12% 39% 28% 5%	594
	21st to end	Night	13% 2 18% 33% 29% 5%	720
September	1st to 10th	Night	14% 5% 19% 32% 26% 4	800
	11th to 20th	Night	11% 3 14% 36% 31% 5%	800
	21st to end	Night	19% 8% 23% 27% 19% 4	800
October	1st to 10th	Night	17% 7% 24% 30% 19% 3	800
	11th to 20th	Night	20% 11% 32% 26% 9% 1	800
	21st to end	Night	28% 10% 30% 26% 6%	880
November	1st to 10th	Night	19% 13% 30% 27% 11% 1	820
	11th to 20th	Night	24% 18% 31% 20% 6% 1	840
	21st to end	Night	29% 16% 31% 19% 5%	840
December	1st to 10th	Night	30% 18% 29% 18% 4	840
	11th to 20th	Night	26% 21% 31% 19% 3	840
	21st to end	Night	28% 17% 34% 19% 2	924

Page generated at 2026-03-30 02:18:44. Version ac07

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