Wild Apple Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wild Apple Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	13% 9% 3 8% 5% 4 4 4 6% 7% 38%	101903
	Night	13% 9% 4 8% 5% 4 4 3 5% 6% 39%	98291
Transparency	Day	44% 5% 12% 24% 13% 1	105418
	Night	45% 5% 11% 23% 15% 2	102903
Seeing	Day	16% 11% 30% 25% 14% 5%	16047
	Night	17% 10% 31% 30% 11% 1	25971

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	11% 13% 10% 15% 5% 5% 4 3 3 4 27%	2527
	11th to 20th	Day	10% 11% 5% 15% 6% 4 5% 8% 8% 7% 20%	2530
	21st to end	Day	16% 19% 9% 12% 5% 3 3 2 4 6% 21%	2957
February	1st to 10th	Day	12% 13% 5% 9% 6% 4 4 4 5% 7% 31%	1710
	11th to 20th	Day	13% 12% 4 8% 5% 3 5% 3 6% 7% 36%	1765
	21st to end	Day	12% 14% 4 10% 6% 5% 4 3 4 6% 32%	1570
March	1st to 10th	Day	14% 8% 3 6% 4 3 4 3 4 6% 44%	3120
	11th to 20th	Day	11% 7% 2 9% 4 4 4 4 6% 7% 43%	3406
	21st to end	Day	22% 12% 3 10% 5% 4 4 3 4 5% 27%	4088
April	1st to 10th	Day	18% 13% 4 7% 6% 4 4 3 5% 6% 31%	2280
	11th to 20th	Day	18% 10% 3 8% 5% 4 4 3 5% 6% 34%	2254
	21st to end	Day	19% 10% 3 8% 5% 4 5% 3 5% 5% 33%	2318
May	1st to 10th	Day	16% 8% 2 7% 5% 5% 4 4 6% 7% 37%	4264
	11th to 20th	Day	13% 7% 3 7% 5% 4 4 3 5% 7% 43%	4399
	21st to end	Day	13% 7% 2 7% 5% 5% 4 4 6% 9% 38%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 5% 5% 3 6% 8% 44%	2660
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 7% 8% 42%	2660
	21st to end	Day	12% 6% 3 6% 6% 4 5% 4 7% 7% 39%	2660
July	1st to 10th	Day	10% 7% 3 9% 5% 5% 6% 5% 8% 9% 34%	4440
	11th to 20th	Day	5% 4 2 5% 4 5% 5% 4 7% 9% 51%	4440
	21st to end	Day	8% 6% 3 7% 5% 5% 5% 4 7% 9% 41%	4813
August	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 5% 6% 9% 40%	4301
	11th to 20th	Day	11% 4 2 6% 4 4 5% 4 5% 7% 47%	3850
	21st to end	Day	9% 6% 2 6% 4 4 4 3 7% 9% 45%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 6% 4 3 6% 7% 44%	2280
	11th to 20th	Day	13% 5% 2 4 3 4 4 3 6% 8% 50%	2237
	21st to end	Day	12% 7% 2 7% 4 4 3 3 5% 7% 45%	2090
October	1st to 10th	Day	13% 7% 2 6% 4 4 4 3 4 6% 48%	1911
	11th to 20th	Day	19% 9% 2 7% 4 4 4 3 5% 5% 38%	1900
	21st to end	Day	17% 11% 3 6% 4 3 3 3 4 6% 40%	1937
November	1st to 10th	Day	12% 8% 2 8% 4 5% 4 3 5% 6% 44%	1762
	11th to 20th	Day	15% 12% 4 9% 5% 5% 4 3 5% 6% 34%	1765
	21st to end	Day	13% 12% 4 10% 5% 4 3 2 4 6% 36%	1600
December	1st to 10th	Day	13% 14% 5% 9% 6% 4 4 4 5% 6% 31%	1600
	11th to 20th	Day	12% 14% 5% 10% 5% 4 4 4 6% 8% 27%	1998
	21st to end	Day	18% 21% 9% 11% 4 4 4 4 4 4 16%	2807
January	1st to 10th	Night	11% 13% 8% 12% 6% 5% 4 3 4 5% 30%	4428
	11th to 20th	Night	11% 14% 6% 14% 6% 5% 4 5% 7% 6% 22%	4440
	21st to end	Night	16% 17% 8% 11% 5% 5% 4 3 4 4 23%	4692
February	1st to 10th	Night	11% 14% 4 9% 6% 5% 4 4 5% 5% 33%	2470
	11th to 20th	Night	12% 9% 3 7% 6% 5% 5% 3 4 6% 39%	2301
	21st to end	Night	15% 13% 4 8% 4 4 4 3 5% 5% 36%	1884
March	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 4 41%	3733
	11th to 20th	Night	10% 6% 2 7% 4 5% 3 4 6% 8% 46%	3581
	21st to end	Night	24% 13% 4 10% 5% 4 4 3 4 5% 26%	3542
April	1st to 10th	Night	17% 9% 3 7% 5% 3 4 4 5% 6% 37%	1900
	11th to 20th	Night	18% 9% 3 7% 4 3 4 3 5% 6% 37%	1875
	21st to end	Night	18% 8% 2 5% 4 4 5% 3 6% 7% 37%	1862
May	1st to 10th	Night	17% 8% 3 6% 4 4 4 4 6% 7% 36%	2632
	11th to 20th	Night	12% 8% 3 7% 5% 4 4 4 5% 7% 42%	2506
	21st to end	Night	10% 7% 3 6% 5% 3 4 3 7% 8% 44%	2743
June	1st to 10th	Night	8% 5% 3 6% 3 5% 5% 4 8% 9% 45%	1520
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 6% 9% 46%	1520
	21st to end	Night	9% 6% 2 6% 4 3 4 4 5% 8% 50%	1520
July	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 6% 9% 42%	2530
	11th to 20th	Night	4 3 1 5% 4 4 4 4 5% 8% 56%	2530
	21st to end	Night	6% 4 2 6% 5% 4 5% 4 7% 9% 49%	2750
August	1st to 10th	Night	9% 5% 2 6% 3 4 4 4 6% 7% 50%	2635
	11th to 20th	Night	10% 5% 2 5% 3 4 4 3 6% 8% 50%	2983
	21st to end	Night	10% 4 2 5% 4 4 4 3 5% 7% 50%	3476
September	1st to 10th	Night	8% 5% 1 5% 3 3 4 3 5% 7% 56%	1900
	11th to 20th	Night	11% 5% 2 4 4 4 4 3 5% 7% 52%	1924
	21st to end	Night	9% 5% 2 6% 4 3 4 3 5% 7% 51%	2090
October	1st to 10th	Night	12% 6% 2 6% 3 3 4 3 4 6% 51%	2266
	11th to 20th	Night	16% 8% 2 6% 4 3 3 4 5% 6% 43%	2280
	21st to end	Night	18% 9% 3 6% 4 4 4 4 5% 7% 37%	2660
November	1st to 10th	Night	12% 8% 3 6% 3 4 3 3 4 6% 47%	2536
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 3 6% 6% 35%	2630
	21st to end	Night	16% 11% 4 7% 5% 4 3 3 5% 5% 38%	2800
December	1st to 10th	Night	13% 12% 4 9% 5% 5% 5% 4 5% 6% 32%	2800
	11th to 20th	Night	15% 14% 4 11% 6% 5% 5% 3 5% 5% 28%	3419
	21st to end	Night	19% 17% 6% 11% 6% 5% 5% 3 5% 4 20%	4933

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	62% 4 12% 16% 6%	2528
	11th to 20th	Day	58% 5% 14% 14% 9%	2530
	21st to end	Day	66% 4 9% 15% 5%	2957
February	1st to 10th	Day	53% 4 12% 19% 12% 1	1710
	11th to 20th	Day	48% 5% 11% 24% 10% 2	1774
	21st to end	Day	54% 5% 9% 20% 10% 3	1570
March	1st to 10th	Day	42% 5% 11% 28% 11% 3	3120
	11th to 20th	Day	40% 4 11% 31% 13% 1	3406
	21st to end	Day	60% 4 11% 17% 7% 1	4088
April	1st to 10th	Day	54% 5% 10% 20% 11% 1	2280
	11th to 20th	Day	51% 4 9% 21% 12% 2	2254
	21st to end	Day	52% 6% 10% 18% 13% 2	2318
May	1st to 10th	Day	46% 6% 10% 22% 16% 1	4302
	11th to 20th	Day	41% 6% 10% 30% 12%	4403
	21st to end	Day	41% 7% 10% 23% 15% 3	4837
June	1st to 10th	Day	36% 7% 15% 26% 15% 1	2660
	11th to 20th	Day	37% 7% 14% 23% 18% 2	2660
	21st to end	Day	41% 7% 13% 23% 13% 2	2660
July	1st to 10th	Day	43% 7% 14% 26% 9% 1	4371
	11th to 20th	Day	28% 6% 16% 32% 16% 1	4365
	21st to end	Day	39% 7% 14% 21% 17% 2	4662
August	1st to 10th	Day	39% 7% 15% 27% 13% 1	4286
	11th to 20th	Day	35% 6% 13% 31% 14% 1	3889
	21st to end	Day	34% 5% 14% 30% 15% 1	4179
September	1st to 10th	Day	39% 6% 11% 25% 18% 2	2280
	11th to 20th	Day	32% 5% 12% 32% 17% 2	2237
	21st to end	Day	40% 5% 9% 29% 17% 1	2090
October	1st to 10th	Day	25% 3 6% 40% 26% 1	3171
	11th to 20th	Day	35% 3 9% 26% 24% 2	3140
	21st to end	Day	43% 3 10% 27% 14% 3	3162
November	1st to 10th	Day	43% 4 13% 25% 13% 2	1762
	11th to 20th	Day	51% 5% 12% 20% 10% 1	1765
	21st to end	Day	51% 4 15% 22% 7% 1	1600
December	1st to 10th	Day	53% 5% 16% 17% 9% 1	1600
	11th to 20th	Day	55% 4 15% 15% 8% 2	1995
	21st to end	Day	71% 5% 8% 10% 5%	2807
January	1st to 10th	Night	57% 4 10% 19% 9% 1	4428
	11th to 20th	Night	61% 5% 9% 15% 9%	4440
	21st to end	Night	66% 3 8% 16% 5% 1	4692
February	1st to 10th	Night	53% 4 11% 18% 13% 2	2470
	11th to 20th	Night	46% 5% 11% 23% 14% 1	2302
	21st to end	Night	50% 4 11% 21% 11% 3	1884
March	1st to 10th	Night	46% 4 11% 24% 10% 5%	3733
	11th to 20th	Night	35% 4 9% 32% 17% 2	3581
	21st to end	Night	62% 4 7% 17% 10% 1	3542
April	1st to 10th	Night	46% 6% 10% 22% 13% 2	1900
	11th to 20th	Night	48% 5% 7% 19% 19% 3	1875
	21st to end	Night	45% 6% 12% 23% 12% 2	1862
May	1st to 10th	Night	45% 7% 11% 16% 20% 2	2659
	11th to 20th	Night	41% 7% 11% 24% 17% 1	2507
	21st to end	Night	35% 7% 13% 22% 20% 3	2751
June	1st to 10th	Night	33% 6% 14% 27% 19% 1	1520
	11th to 20th	Night	34% 5% 11% 25% 23% 2	1520
	21st to end	Night	34% 6% 15% 23% 19% 3	1520
July	1st to 10th	Night	40% 6% 14% 24% 12% 3	2490
	11th to 20th	Night	25% 6% 13% 34% 19% 2	2482
	21st to end	Night	30% 7% 17% 22% 19% 5%	2662
August	1st to 10th	Night	32% 5% 13% 29% 20% 1	2626
	11th to 20th	Night	32% 6% 13% 31% 18% 1	3010
	21st to end	Night	34% 5% 11% 27% 19% 4	3476
September	1st to 10th	Night	28% 6% 12% 28% 24% 2	1900
	11th to 20th	Night	32% 5% 11% 32% 19% 2	1924
	21st to end	Night	32% 5% 11% 30% 21% 1	2090
October	1st to 10th	Night	25% 4 5% 37% 28% 2	3786
	11th to 20th	Night	32% 3 10% 27% 25% 2	3779
	21st to end	Night	43% 5% 9% 26% 15% 2	4372
November	1st to 10th	Night	39% 4 11% 26% 17% 2	2536
	11th to 20th	Night	50% 4 13% 20% 11% 2	2630
	21st to end	Night	49% 3 13% 23% 10% 1	2800
December	1st to 10th	Night	53% 5% 13% 21% 8% 1	2800
	11th to 20th	Night	58% 4 12% 18% 8% 1	3421
	21st to end	Night	67% 4 8% 15% 4	4933

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	17% 16% 30% 27% 9% 2	270
	11th to 20th	Day	20% 16% 39% 20% 5% 1	270
	21st to end	Day	21% 15% 36% 23% 5%	297
February	1st to 10th	Day	15% 20% 40% 18% 6% 1	270
	11th to 20th	Day	20% 23% 32% 20% 4	270
	21st to end	Day	23% 16% 44% 15% 2	225
March	1st to 10th	Day	17% 19% 43% 18% 4	270
	11th to 20th	Day	19% 22% 37% 14% 5% 3	270
	21st to end	Day	27% 14% 32% 18% 7% 2	455
April	1st to 10th	Day	25% 16% 33% 21% 5%	460
	11th to 20th	Day	25% 16% 28% 18% 12% 1	452
	21st to end	Day	23% 14% 28% 24% 10% 2	460
May	1st to 10th	Day	20% 12% 32% 26% 9% 1	567
	11th to 20th	Day	19% 12% 29% 25% 11% 4	675
	21st to end	Day	17% 10% 25% 24% 17% 7%	734
June	1st to 10th	Day	10% 7% 29% 29% 20% 5%	680
	11th to 20th	Day	14% 6% 30% 30% 16% 5%	680
	21st to end	Day	13% 9% 28% 29% 16% 5%	680
July	1st to 10th	Day	7% 4 20% 28% 26% 13%	671
	11th to 20th	Day	9% 5% 25% 31% 21% 9%	668
	21st to end	Day	7% 3 27% 33% 22% 7%	739
August	1st to 10th	Day	7% 3 20% 36% 24% 10%	676
	11th to 20th	Day	12% 5% 22% 24% 24% 12%	552
	21st to end	Day	11% 6% 20% 31% 23% 9%	539
September	1st to 10th	Day	14% 7% 23% 29% 19% 7%	490
	11th to 20th	Day	11% 3 22% 30% 25% 9%	490
	21st to end	Day	13% 11% 28% 26% 16% 4	490
October	1st to 10th	Day	16% 12% 28% 28% 14% 3	311
	11th to 20th	Day	23% 16% 36% 17% 8%	300
	21st to end	Day	24% 19% 30% 21% 5% 2	330
November	1st to 10th	Day	15% 17% 38% 21% 9% 1	300
	11th to 20th	Day	20% 18% 38% 16% 8%	300
	21st to end	Day	22% 13% 42% 19% 4	300
December	1st to 10th	Day	17% 18% 41% 16% 8% 1	300
	11th to 20th	Day	21% 14% 38% 19% 8%	300
	21st to end	Day	26% 19% 35% 18% 2	306
January	1st to 10th	Night	16% 15% 38% 23% 7% 1	950
	11th to 20th	Night	21% 12% 39% 24% 5% 1	950
	21st to end	Night	20% 12% 37% 26% 5%	1045
February	1st to 10th	Night	18% 13% 38% 25% 6%	950
	11th to 20th	Night	17% 15% 39% 25% 4	826
	21st to end	Night	22% 16% 39% 20% 4	628
March	1st to 10th	Night	21% 14% 38% 22% 6%	760
	11th to 20th	Night	16% 12% 36% 28% 8%	632
	21st to end	Night	23% 10% 35% 26% 6%	627
April	1st to 10th	Night	21% 13% 37% 24% 5%	570
	11th to 20th	Night	21% 13% 30% 29% 6%	563
	21st to end	Night	19% 10% 33% 28% 9% 1	570
May	1st to 10th	Night	19% 8% 35% 29% 8% 1	570
	11th to 20th	Night	18% 6% 31% 34% 11%	561
	21st to end	Night	13% 4 28% 38% 15% 1	617
June	1st to 10th	Night	11% 5% 25% 44% 15% 1	570
	11th to 20th	Night	15% 4 31% 38% 13%	570
	21st to end	Night	10% 5% 26% 42% 16% 1	570
July	1st to 10th	Night	10% 2 14% 39% 32% 4	555
	11th to 20th	Night	7% 3 22% 41% 23% 3	552
	21st to end	Night	7% 2 18% 46% 25% 2	624
August	1st to 10th	Night	6% 2 17% 45% 28% 3	567
	11th to 20th	Night	11% 3 14% 41% 27% 5%	564
	21st to end	Night	11% 2 16% 46% 23% 3	627
September	1st to 10th	Night	9% 3 24% 36% 23% 6%	570
	11th to 20th	Night	13% 3 21% 35% 24% 4	594
	21st to end	Night	12% 8% 25% 35% 18% 2	760
October	1st to 10th	Night	16% 7% 26% 33% 17% 1	760
	11th to 20th	Night	18% 12% 31% 29% 9%	760
	21st to end	Night	22% 12% 33% 26% 6% 1	836
November	1st to 10th	Night	16% 10% 39% 25% 9% 1	780
	11th to 20th	Night	20% 15% 36% 22% 6% 1	830
	21st to end	Night	21% 14% 35% 23% 6%	1000
December	1st to 10th	Night	20% 13% 39% 24% 5%	1000
	11th to 20th	Night	24% 11% 35% 24% 5% 1	1000
	21st to end	Night	28% 14% 33% 22% 3	1063

Page generated at 2024-12-21 03:13:52. Version ac07

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