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 2024-12-09.

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	16% 11% 4 8% 5% 5% 4 4 5% 7% 30%	101339
	Night	16% 12% 4 8% 5% 4 4 3 5% 6% 32%	98371
Transparency	Day	51% 5% 11% 20% 11% 1	105002
	Night	52% 5% 11% 20% 11% 2	102834
Seeing	Day	21% 14% 28% 21% 12% 4	14726
	Night	21% 12% 27% 27% 12% 1	24535

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% 23% 8% 12% 6% 3 3 3 3 5% 15%	2836
	11th to 20th	Day	13% 25% 8% 12% 7% 5% 3 2 4 5% 15%	2840
	21st to end	Day	26% 20% 9% 13% 6% 5% 2 3 3 3 9%	3124
February	1st to 10th	Day	18% 19% 4 12% 8% 4 3 2 4 4 22%	1710
	11th to 20th	Day	15% 14% 7% 13% 7% 5% 5% 3 5% 5% 21%	1682
	21st to end	Day	20% 15% 4 10% 6% 5% 4 3 5% 5% 23%	1570
March	1st to 10th	Day	22% 13% 5% 9% 6% 4 4 3 4 5% 26%	3405
	11th to 20th	Day	13% 12% 4 10% 6% 4 5% 4 4 6% 33%	3480
	21st to end	Day	21% 11% 4 9% 5% 4 4 3 4 6% 29%	3815
April	1st to 10th	Day	15% 14% 4 7% 6% 4 4 3 5% 8% 30%	2153
	11th to 20th	Day	17% 13% 3 7% 4 4 4 4 5% 6% 33%	2360
	21st to end	Day	20% 11% 3 7% 5% 4 3 4 4 6% 33%	2470
May	1st to 10th	Day	21% 10% 4 8% 5% 5% 5% 4 5% 6% 28%	4082
	11th to 20th	Day	19% 9% 3 8% 5% 4 5% 3 6% 7% 31%	4081
	21st to end	Day	12% 6% 2 7% 5% 4 5% 4 7% 9% 39%	4625
June	1st to 10th	Day	15% 7% 3 7% 6% 5% 5% 4 7% 9% 33%	2660
	11th to 20th	Day	13% 7% 3 7% 6% 5% 5% 4 6% 8% 36%	2660
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 9% 38%	2660
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 5% 4 7% 10% 39%	4190
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 4 8% 10% 40%	4120
	21st to end	Day	11% 6% 3 7% 6% 5% 6% 5% 7% 8% 36%	4466
August	1st to 10th	Day	15% 7% 3 8% 5% 6% 5% 5% 6% 8% 31%	4104
	11th to 20th	Day	12% 6% 2 7% 5% 6% 6% 5% 7% 9% 33%	4044
	21st to end	Day	9% 5% 2 7% 5% 6% 6% 5% 7% 9% 39%	4404
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 4 5% 6% 44%	2223
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 9% 43%	2090
	21st to end	Day	20% 8% 3 7% 4 5% 5% 3 5% 6% 36%	2090
October	1st to 10th	Day	15% 7% 2 8% 5% 4 4 3 6% 7% 38%	1936
	11th to 20th	Day	18% 11% 2 7% 5% 4 4 4 5% 5% 33%	1900
	21st to end	Day	22% 12% 3 7% 4 5% 3 3 4 7% 29%	2090
November	1st to 10th	Day	11% 9% 3 7% 5% 5% 5% 3 5% 6% 40%	1805
	11th to 20th	Day	17% 16% 3 8% 5% 4 5% 3 5% 6% 29%	1725
	21st to end	Day	17% 17% 7% 11% 5% 5% 4 3 5% 5% 22%	1600
December	1st to 10th	Day	21% 19% 5% 12% 6% 4 4 3 5% 4 17%	1584
	11th to 20th	Day	17% 18% 7% 13% 5% 4 4 4 5% 6% 16%	1910
	21st to end	Day	25% 25% 7% 11% 5% 4 3 2 3 4 11%	2845
January	1st to 10th	Night	16% 22% 8% 14% 5% 4 4 3 4 5% 15%	4109
	11th to 20th	Night	14% 20% 8% 17% 7% 5% 6% 4 4 4 13%	4120
	21st to end	Night	27% 18% 9% 13% 6% 3 3 2 3 3 14%	4532
February	1st to 10th	Night	21% 14% 5% 11% 7% 4 4 3 4 6% 22%	2470
	11th to 20th	Night	17% 14% 6% 12% 7% 5% 5% 3 4 6% 22%	2380
	21st to end	Night	20% 15% 5% 11% 5% 5% 5% 3 5% 4 24%	1884
March	1st to 10th	Night	23% 14% 3 7% 4 4 3 2 3 5% 32%	3436
	11th to 20th	Night	17% 12% 5% 7% 4 4 4 3 5% 6% 32%	3480
	21st to end	Night	17% 12% 3 8% 4 3 4 3 4 5% 36%	3817
April	1st to 10th	Night	16% 13% 3 7% 5% 5% 4 4 4 6% 34%	2026
	11th to 20th	Night	16% 9% 3 8% 4 5% 5% 3 5% 7% 34%	1785
	21st to end	Night	16% 9% 3 7% 4 4 4 4 6% 8% 35%	1710
May	1st to 10th	Night	27% 10% 3 7% 4 4 4 3 5% 6% 27%	2813
	11th to 20th	Night	17% 9% 3 7% 5% 3 4 3 5% 8% 36%	2812
	21st to end	Night	10% 5% 2 5% 4 4 4 4 7% 11% 44%	2925
June	1st to 10th	Night	9% 7% 2 7% 6% 6% 4 4 5% 7% 43%	1520
	11th to 20th	Night	9% 6% 2 8% 4 4 4 4 6% 9% 42%	1520
	21st to end	Night	9% 5% 2 7% 5% 4 4 6% 7% 8% 42%	1520
July	1st to 10th	Night	11% 7% 3 7% 5% 4 4 4 5% 9% 42%	2764
	11th to 20th	Night	10% 5% 2 4 4 4 5% 4 6% 9% 47%	2840
	21st to end	Night	8% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	3087
August	1st to 10th	Night	13% 8% 3 8% 4 5% 5% 4 5% 7% 37%	2825
	11th to 20th	Night	14% 8% 3 6% 4 4 4 3 5% 6% 43%	2785
	21st to end	Night	8% 5% 2 7% 5% 5% 5% 4 7% 7% 44%	3220
September	1st to 10th	Night	13% 5% 2 6% 3 4 4 3 4 7% 49%	1953
	11th to 20th	Night	10% 6% 2 4 3 3 4 4 5% 7% 52%	2090
	21st to end	Night	17% 7% 3 6% 4 3 4 3 5% 8% 39%	2090
October	1st to 10th	Night	15% 4 2 6% 5% 4 4 3 5% 7% 45%	2242
	11th to 20th	Night	17% 8% 3 8% 5% 5% 5% 3 5% 6% 36%	2280
	21st to end	Night	23% 9% 2 6% 4 4 4 3 5% 7% 33%	2508
November	1st to 10th	Night	14% 9% 2 6% 4 4 4 3 5% 6% 43%	2488
	11th to 20th	Night	16% 14% 4 9% 5% 4 4 3 5% 5% 30%	2670
	21st to end	Night	19% 16% 5% 8% 5% 4 4 3 4 6% 26%	2800
December	1st to 10th	Night	20% 17% 6% 12% 6% 4 4 3 4 5% 19%	2779
	11th to 20th	Night	17% 20% 6% 11% 6% 4 3 3 5% 5% 21%	3285
	21st to end	Night	25% 21% 8% 9% 5% 4 4 3 4 4 13%	4806

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	74% 3 8% 12% 3	2837
	11th to 20th	Day	74% 2 8% 12% 3	2840
	21st to end	Day	82% 2 7% 7% 2 1	3124
February	1st to 10th	Day	68% 2 9% 14% 7% 1	1710
	11th to 20th	Day	65% 5% 8% 14% 8%	1691
	21st to end	Day	62% 3 11% 15% 7% 2	1570
March	1st to 10th	Day	60% 4 10% 21% 5%	3405
	11th to 20th	Day	53% 4 12% 23% 7% 1	3480
	21st to end	Day	57% 3 9% 18% 12% 1	3815
April	1st to 10th	Day	54% 4 11% 19% 12% 1	2153
	11th to 20th	Day	52% 5% 11% 18% 13% 2	2360
	21st to end	Day	53% 4 10% 21% 10% 2	2470
May	1st to 10th	Day	56% 5% 10% 20% 9% 1	4120
	11th to 20th	Day	51% 5% 12% 21% 10% 1	4085
	21st to end	Day	40% 5% 15% 22% 14% 4	4639
June	1st to 10th	Day	46% 5% 13% 23% 12% 1	2660
	11th to 20th	Day	44% 5% 13% 23% 14% 1	2660
	21st to end	Day	40% 6% 13% 25% 14% 2	2660
July	1st to 10th	Day	39% 7% 13% 24% 15% 3	4125
	11th to 20th	Day	36% 7% 13% 26% 18% 1	4051
	21st to end	Day	42% 8% 13% 19% 17% 2	4324
August	1st to 10th	Day	48% 7% 13% 22% 10%	4091
	11th to 20th	Day	42% 8% 12% 28% 8% 1	4083
	21st to end	Day	38% 8% 13% 27% 12% 2	4404
September	1st to 10th	Day	40% 5% 11% 23% 18% 3	2223
	11th to 20th	Day	38% 6% 13% 25% 17% 2	2090
	21st to end	Day	48% 4 11% 24% 12% 1	2090
October	1st to 10th	Day	34% 5% 12% 29% 19% 1	3209
	11th to 20th	Day	47% 5% 10% 20% 14% 4	3140
	21st to end	Day	41% 4 12% 27% 15% 1	3428
November	1st to 10th	Day	44% 4 11% 23% 16% 2	1805
	11th to 20th	Day	56% 4 11% 18% 9% 3	1725
	21st to end	Day	63% 5% 10% 15% 6% 1	1600
December	1st to 10th	Day	70% 4 10% 12% 3	1584
	11th to 20th	Day	68% 4 9% 15% 4	1906
	21st to end	Day	79% 2 10% 7% 2	2845
January	1st to 10th	Night	72% 3 10% 11% 3	4109
	11th to 20th	Night	75% 3 9% 10% 2	4120
	21st to end	Night	78% 2 6% 11% 2	4532
February	1st to 10th	Night	65% 4 10% 16% 6%	2470
	11th to 20th	Night	63% 4 9% 17% 7% 1	2382
	21st to end	Night	63% 4 8% 14% 9% 2	1884
March	1st to 10th	Night	57% 3 10% 22% 8%	3436
	11th to 20th	Night	52% 5% 15% 20% 7% 1	3480
	21st to end	Night	50% 4 10% 23% 12% 1	3817
April	1st to 10th	Night	51% 4 11% 19% 13% 2	2026
	11th to 20th	Night	49% 4 13% 16% 15% 3	1785
	21st to end	Night	46% 4 12% 20% 15% 2	1710
May	1st to 10th	Night	57% 4 7% 20% 9% 2	2840
	11th to 20th	Night	47% 6% 11% 24% 11% 2	2813
	21st to end	Night	32% 7% 15% 27% 16% 3	2932
June	1st to 10th	Night	39% 6% 11% 25% 16% 2	1520
	11th to 20th	Night	38% 5% 14% 24% 16% 2	1520
	21st to end	Night	37% 7% 14% 23% 18% 1	1520
July	1st to 10th	Night	40% 6% 11% 22% 18% 2	2719
	11th to 20th	Night	32% 6% 14% 30% 17% 1	2786
	21st to end	Night	38% 8% 12% 18% 23% 2	2988
August	1st to 10th	Night	44% 6% 11% 24% 12% 1	2814
	11th to 20th	Night	40% 6% 11% 28% 14% 1	2812
	21st to end	Night	36% 7% 12% 29% 14% 2	3220
September	1st to 10th	Night	35% 5% 10% 26% 19% 4	1953
	11th to 20th	Night	30% 5% 13% 27% 22% 2	2090
	21st to end	Night	44% 3 12% 22% 17% 1	2090
October	1st to 10th	Night	34% 4 9% 28% 24% 1	3736
	11th to 20th	Night	41% 6% 11% 22% 14% 6%	3779
	21st to end	Night	37% 4 9% 30% 17% 1	4120
November	1st to 10th	Night	42% 4 11% 24% 16% 3	2488
	11th to 20th	Night	56% 4 10% 19% 9% 3	2670
	21st to end	Night	60% 4 12% 18% 5% 1	2800
December	1st to 10th	Night	68% 4 10% 12% 5%	2779
	11th to 20th	Night	66% 4 11% 15% 3	3288
	21st to end	Night	75% 4 11% 9% 2	4806

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	30% 25% 31% 11% 4	270
	11th to 20th	Day	30% 26% 34% 8% 2	270
	21st to end	Day	28% 29% 31% 9% 3	297
February	1st to 10th	Day	31% 20% 37% 10% 1	270
	11th to 20th	Day	29% 31% 29% 10% 1	270
	21st to end	Day	30% 30% 32% 7%	225
March	1st to 10th	Day	25% 21% 33% 17% 4	441
	11th to 20th	Day	29% 17% 34% 13% 6% 1	460
	21st to end	Day	34% 18% 27% 17% 4 1	506
April	1st to 10th	Day	24% 21% 29% 17% 8% 2	460
	11th to 20th	Day	29% 15% 28% 15% 10% 4	452
	21st to end	Day	26% 15% 34% 17% 7% 2	460
May	1st to 10th	Day	26% 17% 27% 18% 8% 3	463
	11th to 20th	Day	23% 11% 29% 22% 9% 5%	487
	21st to end	Day	13% 9% 27% 25% 20% 5%	529
June	1st to 10th	Day	16% 9% 31% 28% 12% 4	490
	11th to 20th	Day	17% 9% 26% 29% 15% 5%	490
	21st to end	Day	14% 10% 31% 26% 14% 5%	490
July	1st to 10th	Day	14% 5% 20% 25% 24% 12%	485
	11th to 20th	Day	12% 7% 24% 30% 19% 8%	484
	21st to end	Day	12% 4 27% 27% 21% 9%	532
August	1st to 10th	Day	13% 8% 20% 27% 21% 10%	486
	11th to 20th	Day	16% 8% 21% 25% 21% 9%	479
	21st to end	Day	10% 5% 23% 29% 23% 11%	539
September	1st to 10th	Day	14% 7% 23% 24% 21% 10%	490
	11th to 20th	Day	10% 4 18% 33% 23% 12%	490
	21st to end	Day	25% 10% 23% 23% 12% 7%	490
October	1st to 10th	Day	14% 11% 27% 26% 18% 5%	490
	11th to 20th	Day	21% 15% 35% 19% 9% 2	490
	21st to end	Day	31% 15% 30% 19% 6%	539
November	1st to 10th	Day	19% 19% 33% 18% 8% 3	343
	11th to 20th	Day	30% 19% 29% 16% 5% 1	263
	21st to end	Day	26% 23% 38% 14% 1	200
December	1st to 10th	Day	30% 26% 31% 8% 4 2	196
	11th to 20th	Day	28% 20% 37% 12% 2	180
	21st to end	Day	34% 25% 28% 12% 2	220
January	1st to 10th	Night	26% 21% 34% 15% 4	760
	11th to 20th	Night	30% 18% 33% 15% 4	760
	21st to end	Night	26% 19% 30% 21% 4	836
February	1st to 10th	Night	29% 16% 32% 21% 2	760
	11th to 20th	Night	26% 18% 37% 17% 2	743
	21st to end	Night	29% 16% 34% 18% 2	628
March	1st to 10th	Night	24% 16% 33% 23% 3	760
	11th to 20th	Night	25% 17% 29% 23% 6% 1	760
	21st to end	Night	24% 14% 32% 24% 6% 1	836
April	1st to 10th	Night	22% 17% 31% 25% 6%	760
	11th to 20th	Night	23% 11% 34% 23% 8% 1	661
	21st to end	Night	19% 11% 35% 29% 7%	570
May	1st to 10th	Night	22% 8% 27% 32% 10% 1	570
	11th to 20th	Night	19% 7% 24% 37% 12% 2	561
	21st to end	Night	11% 3 24% 37% 23% 3	527
June	1st to 10th	Night	9% 6% 27% 42% 15% 1	380
	11th to 20th	Night	9% 4 26% 45% 15% 1	380
	21st to end	Night	11% 5% 26% 38% 21% 1	380
July	1st to 10th	Night	8% 4 17% 40% 27% 6%	505
	11th to 20th	Night	10% 3 19% 39% 26% 4	552
	21st to end	Night	12% 2 15% 40% 29% 2	624
August	1st to 10th	Night	10% 4 13% 43% 29% 2	567
	11th to 20th	Night	14% 3 12% 39% 27% 5%	564
	21st to end	Night	12% 2 18% 33% 29% 6%	684
September	1st to 10th	Night	14% 5% 18% 32% 26% 4	760
	11th to 20th	Night	12% 3 14% 36% 30% 5%	760
	21st to end	Night	19% 8% 23% 27% 19% 4	760
October	1st to 10th	Night	17% 7% 25% 29% 19% 3	760
	11th to 20th	Night	21% 11% 31% 26% 10% 1	760
	21st to end	Night	28% 10% 30% 26% 6%	836
November	1st to 10th	Night	19% 12% 29% 28% 11% 1	780
	11th to 20th	Night	24% 17% 32% 20% 7% 1	800
	21st to end	Night	29% 16% 30% 19% 5%	800
December	1st to 10th	Night	30% 18% 29% 18% 4	795
	11th to 20th	Night	25% 21% 31% 20% 4	760
	21st to end	Night	28% 17% 33% 20% 2	836

Page generated at 2024-12-06 03:54:53. Version ac07

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