Oak Beach Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oak Beach Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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% 10% 4 8% 5% 5% 5% 4 5% 7% 35%	101198
	Night	14% 11% 4 9% 6% 5% 4 4 5% 6% 32%	97830
Transparency	Day	26% 48% 7% 12% 6% 1	104796
	Night	28% 48% 7% 12% 6% 1	102373
Seeing	Day	16% 7% 24% 30% 18% 5%	15414
	Night	19% 8% 28% 29% 14% 2	24884

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% 16% 10% 16% 7% 4 5% 3 4 4 16%	2527
	11th to 20th	Day	12% 18% 8% 17% 14% 9% 4 3 4 4 7%	2530
	21st to end	Day	21% 18% 6% 12% 6% 4 4 4 5% 5% 14%	2967
February	1st to 10th	Day	12% 15% 5% 12% 6% 6% 5% 4 4 7% 22%	1710
	11th to 20th	Day	11% 12% 5% 12% 9% 6% 5% 4 5% 5% 26%	1744
	21st to end	Day	14% 13% 4 7% 7% 5% 4 4 6% 7% 28%	1570
March	1st to 10th	Day	17% 12% 3 9% 6% 4 4 3 4 6% 31%	3203
	11th to 20th	Day	11% 12% 5% 9% 5% 5% 5% 4 5% 7% 31%	3480
	21st to end	Day	15% 11% 4 9% 7% 5% 5% 4 5% 6% 29%	3815
April	1st to 10th	Day	15% 11% 3 8% 5% 4 5% 4 6% 7% 31%	2210
	11th to 20th	Day	17% 8% 3 7% 4 4 4 3 5% 7% 38%	2441
	21st to end	Day	15% 9% 3 8% 5% 5% 5% 3 5% 6% 36%	2470
May	1st to 10th	Day	14% 7% 3 7% 5% 4 4 4 5% 7% 39%	4082
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	4081
	21st to end	Day	10% 6% 2 6% 4 3 4 3 5% 7% 50%	4778
June	1st to 10th	Day	10% 7% 2 5% 4 5% 4 4 7% 8% 43%	2850
	11th to 20th	Day	10% 5% 3 5% 4 4 4 4 7% 9% 45%	2850
	21st to end	Day	11% 6% 2 6% 4 4 5% 5% 6% 8% 44%	2850
July	1st to 10th	Day	11% 5% 3 7% 5% 4 5% 4 7% 9% 41%	4583
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 6% 9% 51%	4440
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 7% 10% 45%	4638
August	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 5% 7% 10% 41%	4104
	11th to 20th	Day	11% 6% 2 6% 3 5% 5% 4 6% 8% 44%	4044
	21st to end	Day	9% 6% 2 6% 4 4 5% 4 6% 9% 45%	4532
September	1st to 10th	Day	10% 7% 2 6% 4 4 5% 4 6% 8% 43%	2176
	11th to 20th	Day	13% 6% 2 4 3 4 4 3 5% 8% 47%	2090
	21st to end	Day	15% 7% 3 6% 5% 4 6% 5% 6% 8% 36%	2090
October	1st to 10th	Day	15% 9% 2 7% 5% 4 4 3 4 6% 40%	2014
	11th to 20th	Day	21% 13% 3 8% 5% 5% 4 4 4 7% 28%	1900
	21st to end	Day	22% 11% 4 8% 6% 5% 5% 4 6% 7% 22%	1919
November	1st to 10th	Day	13% 14% 4 8% 6% 5% 4 3 6% 7% 29%	1708
	11th to 20th	Day	14% 16% 5% 10% 6% 5% 5% 4 5% 8% 21%	1656
	21st to end	Day	17% 18% 6% 13% 6% 5% 4 3 3 6% 18%	1520
December	1st to 10th	Day	11% 21% 9% 13% 8% 6% 4 4 4 4 14%	1506
	11th to 20th	Day	14% 18% 5% 13% 7% 6% 4 5% 5% 5% 18%	1675
	21st to end	Day	25% 22% 7% 12% 6% 5% 4 3 3 4 9%	2445
January	1st to 10th	Night	16% 15% 7% 15% 6% 5% 4 3 4 5% 20%	4428
	11th to 20th	Night	13% 15% 8% 17% 13% 9% 4 3 4 4 11%	4440
	21st to end	Night	17% 16% 8% 12% 8% 5% 5% 4 5% 5% 16%	4692
February	1st to 10th	Night	13% 16% 6% 12% 6% 6% 5% 4 6% 6% 22%	2470
	11th to 20th	Night	14% 14% 5% 11% 6% 5% 5% 3 5% 6% 27%	2318
	21st to end	Night	15% 14% 5% 10% 6% 4 4 5% 4 5% 26%	1884
March	1st to 10th	Night	12% 12% 3 6% 4 4 4 3 4 6% 40%	3649
	11th to 20th	Night	9% 11% 4 9% 5% 4 4 4 4 7% 39%	3480
	21st to end	Night	14% 11% 5% 11% 6% 6% 4 3 4 5% 31%	3817
April	1st to 10th	Night	18% 13% 4 7% 4 4 4 3 4 7% 33%	1986
	11th to 20th	Night	18% 8% 2 6% 5% 3 4 4 5% 8% 37%	1687
	21st to end	Night	17% 11% 3 7% 5% 6% 3 3 5% 6% 35%	1710
May	1st to 10th	Night	12% 8% 4 7% 5% 5% 4 4 6% 8% 39%	2813
	11th to 20th	Night	14% 8% 2 7% 5% 4 5% 3 6% 8% 39%	2812
	21st to end	Night	10% 5% 2 5% 4 4 5% 3 5% 7% 49%	2774
June	1st to 10th	Night	13% 7% 3 6% 5% 4 4 3 6% 8% 41%	1330
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 4 6% 8% 44%	1330
	21st to end	Night	8% 7% 3 7% 5% 4 4 4 6% 8% 44%	1330
July	1st to 10th	Night	8% 6% 3 7% 4 5% 5% 3 6% 8% 45%	2369
	11th to 20th	Night	9% 3 1 4 4 3 4 4 6% 8% 53%	2530
	21st to end	Night	6% 5% 2 6% 5% 4 5% 5% 7% 9% 47%	2916
August	1st to 10th	Night	9% 6% 2 5% 4 4 5% 4 6% 8% 46%	2825
	11th to 20th	Night	11% 6% 1 5% 4 4 3 4 6% 10% 46%	2785
	21st to end	Night	7% 5% 2 7% 5% 5% 5% 3 7% 8% 47%	3124
September	1st to 10th	Night	11% 6% 2 7% 4 5% 4 3 5% 8% 46%	1980
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 51%	2090
	21st to end	Night	15% 7% 3 7% 5% 4 4 3 5% 6% 41%	2090
October	1st to 10th	Night	16% 7% 2 7% 5% 3 5% 3 5% 7% 41%	2166
	11th to 20th	Night	20% 12% 3 9% 5% 4 4 2 4 6% 31%	2280
	21st to end	Night	23% 12% 4 8% 5% 4 5% 3 5% 6% 25%	2677
November	1st to 10th	Night	15% 13% 3 9% 4 4 4 3 4 6% 34%	2470
	11th to 20th	Night	15% 16% 6% 12% 7% 5% 4 4 5% 5% 21%	2522
	21st to end	Night	20% 18% 5% 10% 6% 4 3 4 4 5% 20%	2660
December	1st to 10th	Night	18% 18% 8% 13% 5% 5% 4 4 5% 5% 16%	2669
	11th to 20th	Night	14% 16% 6% 14% 8% 6% 5% 5% 5% 6% 16%	3522
	21st to end	Night	24% 22% 7% 11% 6% 5% 4 3 4 4 11%	5205

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	44% 44% 8% 4 1	2528
	11th to 20th	Day	55% 39% 3 2	2530
	21st to end	Day	45% 43% 9% 3 1	2967
February	1st to 10th	Day	23% 66% 4 6% 1	1710
	11th to 20th	Day	20% 66% 4 7% 3	1753
	21st to end	Day	15% 67% 7% 7% 4	1570
March	1st to 10th	Day	32% 43% 6% 15% 3	3203
	11th to 20th	Day	30% 43% 9% 12% 5% 1	3480
	21st to end	Day	32% 44% 7% 9% 7% 1	3815
April	1st to 10th	Day	18% 66% 4 7% 4	2210
	11th to 20th	Day	17% 66% 4 8% 5% 1	2441
	21st to end	Day	16% 65% 6% 7% 5% 1	2470
May	1st to 10th	Day	26% 42% 8% 11% 12% 2	4120
	11th to 20th	Day	24% 45% 11% 16% 4	4085
	21st to end	Day	20% 41% 6% 13% 14% 6%	4792
June	1st to 10th	Day	13% 66% 4 10% 6%	2850
	11th to 20th	Day	15% 66% 5% 8% 5% 1	2850
	21st to end	Day	13% 65% 5% 10% 7%	2850
July	1st to 10th	Day	29% 37% 10% 12% 10% 2	4514
	11th to 20th	Day	17% 38% 9% 28% 8% 1	4365
	21st to end	Day	22% 37% 12% 16% 13% 1	4491
August	1st to 10th	Day	22% 39% 8% 19% 10% 1	4091
	11th to 20th	Day	27% 39% 11% 17% 5%	4083
	21st to end	Day	23% 39% 10% 19% 9%	4531
September	1st to 10th	Day	14% 63% 7% 11% 4	2176
	11th to 20th	Day	14% 60% 4 14% 8% 1	2090
	21st to end	Day	17% 62% 7% 9% 4	2090
October	1st to 10th	Day	19% 38% 8% 26% 8% 2	3352
	11th to 20th	Day	30% 37% 8% 15% 10%	3140
	21st to end	Day	32% 39% 8% 17% 5%	3143
November	1st to 10th	Day	26% 58% 6% 7% 3	1708
	11th to 20th	Day	25% 61% 6% 5% 3	1656
	21st to end	Day	29% 60% 5% 4 2	1520
December	1st to 10th	Day	29% 62% 4 4 1	1506
	11th to 20th	Day	36% 50% 5% 8% 2	1671
	21st to end	Day	54% 39% 5% 3	2445
January	1st to 10th	Night	42% 39% 10% 7% 2	4428
	11th to 20th	Night	51% 40% 4 4 1	4440
	21st to end	Night	46% 43% 5% 5% 1	4692
February	1st to 10th	Night	23% 65% 4 5% 3	2470
	11th to 20th	Night	19% 65% 5% 9% 3	2320
	21st to end	Night	20% 65% 5% 5% 5% 1	1884
March	1st to 10th	Night	25% 43% 9% 18% 4	3649
	11th to 20th	Night	25% 43% 11% 14% 7% 1	3480
	21st to end	Night	30% 44% 7% 13% 5%	3817
April	1st to 10th	Night	21% 65% 3 6% 5% 1	1986
	11th to 20th	Night	17% 66% 4 7% 6% 1	1687
	21st to end	Night	18% 66% 3 7% 5% 1	1710
May	1st to 10th	Night	25% 42% 8% 12% 9% 4	2840
	11th to 20th	Night	24% 43% 7% 18% 7% 1	2813
	21st to end	Night	22% 42% 5% 14% 12% 5%	2781
June	1st to 10th	Night	14% 65% 4 10% 7% 1	1330
	11th to 20th	Night	14% 66% 5% 7% 6% 2	1330
	21st to end	Night	14% 63% 4 10% 8% 1	1330
July	1st to 10th	Night	27% 37% 10% 14% 7% 5%	2330
	11th to 20th	Night	17% 37% 9% 26% 10%	2482
	21st to end	Night	21% 37% 13% 14% 15% 1	2823
August	1st to 10th	Night	23% 37% 9% 19% 11% 1	2814
	11th to 20th	Night	23% 40% 10% 19% 6% 2	2812
	21st to end	Night	21% 41% 10% 20% 8%	3124
September	1st to 10th	Night	15% 62% 5% 12% 6%	1980
	11th to 20th	Night	12% 60% 3 14% 9% 1	2090
	21st to end	Night	18% 60% 6% 12% 4	2090
October	1st to 10th	Night	16% 38% 7% 24% 14%	3608
	11th to 20th	Night	29% 37% 6% 18% 11%	3779
	21st to end	Night	30% 37% 8% 19% 6%	4403
November	1st to 10th	Night	27% 58% 4 6% 3	2470
	11th to 20th	Night	27% 60% 5% 6% 2	2522
	21st to end	Night	29% 61% 6% 3 1	2660
December	1st to 10th	Night	27% 61% 4 5% 2	2669
	11th to 20th	Night	34% 51% 9% 5% 1	3525
	21st to end	Night	51% 41% 5% 2 1	5205

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	16% 14% 39% 21% 8% 1	270
	11th to 20th	Day	20% 11% 36% 23% 9%	270
	21st to end	Day	24% 6% 32% 30% 7% 1	297
February	1st to 10th	Day	20% 10% 42% 23% 4 1	270
	11th to 20th	Day	15% 14% 40% 26% 5%	270
	21st to end	Day	17% 16% 41% 23% 3	225
March	1st to 10th	Day	18% 14% 34% 27% 7% 1	314
	11th to 20th	Day	15% 13% 30% 31% 9% 2	460
	21st to end	Day	20% 11% 29% 32% 8% 1	506
April	1st to 10th	Day	19% 9% 32% 30% 9% 1	460
	11th to 20th	Day	22% 11% 23% 28% 12% 5%	452
	21st to end	Day	19% 7% 30% 30% 12% 2	460
May	1st to 10th	Day	15% 8% 29% 31% 14% 3	463
	11th to 20th	Day	14% 5% 22% 31% 22% 5%	487
	21st to end	Day	12% 3 19% 33% 26% 7%	600
June	1st to 10th	Day	12% 4 20% 38% 23% 4	680
	11th to 20th	Day	12% 2 20% 39% 22% 5%	680
	21st to end	Day	12% 3 19% 40% 21% 5%	680
July	1st to 10th	Day	9% 2 12% 36% 32% 9%	671
	11th to 20th	Day	11% 3 15% 39% 25% 8%	668
	21st to end	Day	9% 2 14% 39% 28% 8%	639
August	1st to 10th	Day	10% 3 14% 33% 30% 11%	486
	11th to 20th	Day	10% 3 10% 32% 33% 12%	479
	21st to end	Day	14% 4 16% 28% 31% 8%	539
September	1st to 10th	Day	12% 4 21% 29% 22% 11%	490
	11th to 20th	Day	12% 4 15% 25% 28% 16%	490
	21st to end	Day	17% 6% 22% 22% 24% 9%	490
October	1st to 10th	Day	19% 7% 25% 24% 19% 6%	490
	11th to 20th	Day	25% 11% 28% 26% 8% 2	490
	21st to end	Day	28% 12% 27% 25% 7% 1	368
November	1st to 10th	Day	18% 9% 33% 26% 12% 1	282
	11th to 20th	Day	19% 17% 35% 22% 5% 2	244
	21st to end	Day	24% 16% 37% 21% 2	180
December	1st to 10th	Day	21% 17% 36% 24% 3	180
	11th to 20th	Day	25% 21% 32% 18% 3 1	180
	21st to end	Day	27% 16% 37% 17% 2	204
January	1st to 10th	Night	21% 12% 36% 23% 6% 1	950
	11th to 20th	Night	22% 13% 35% 23% 7% 1	950
	21st to end	Night	18% 7% 38% 27% 9%	931
February	1st to 10th	Night	20% 9% 39% 27% 5% 1	760
	11th to 20th	Night	21% 10% 36% 28% 6%	743
	21st to end	Night	21% 11% 38% 26% 4	628
March	1st to 10th	Night	16% 8% 36% 29% 10%	760
	11th to 20th	Night	16% 9% 37% 29% 8% 1	760
	21st to end	Night	21% 9% 29% 29% 11% 1	836
April	1st to 10th	Night	21% 9% 31% 29% 9%	656
	11th to 20th	Night	21% 6% 29% 29% 12% 3	563
	21st to end	Night	21% 6% 23% 35% 14% 1	570
May	1st to 10th	Night	15% 4 23% 42% 15% 3	570
	11th to 20th	Night	17% 4 20% 35% 22% 2	561
	21st to end	Night	13% 3 18% 35% 29% 3	513
June	1st to 10th	Night	14% 2 20% 39% 23% 2	380
	11th to 20th	Night	11% 3 18% 41% 25% 2	380
	21st to end	Night	11% 3 19% 39% 24% 4	380
July	1st to 10th	Night	7% 2 13% 45% 30% 3	460
	11th to 20th	Night	9% 3 14% 39% 28% 7%	552
	21st to end	Night	8% 2 13% 44% 29% 4	624
August	1st to 10th	Night	11% 1 12% 39% 33% 5%	567
	11th to 20th	Night	10% 2 15% 31% 35% 8%	564
	21st to end	Night	12% 3 17% 32% 31% 5%	627
September	1st to 10th	Night	12% 5% 20% 33% 23% 8%	679
	11th to 20th	Night	13% 2 17% 30% 29% 9%	760
	21st to end	Night	17% 6% 22% 27% 20% 7%	760
October	1st to 10th	Night	19% 6% 28% 27% 18% 3	760
	11th to 20th	Night	28% 12% 25% 25% 9%	760
	21st to end	Night	30% 11% 27% 27% 5% 1	836
November	1st to 10th	Night	23% 13% 28% 25% 11% 1	760
	11th to 20th	Night	23% 13% 35% 20% 8%	760
	21st to end	Night	30% 13% 32% 20% 4	760
December	1st to 10th	Night	28% 15% 34% 17% 6%	769
	11th to 20th	Night	24% 15% 37% 20% 3 1	950
	21st to end	Night	28% 13% 36% 20% 2	1045

Page generated at 2024-11-03 02:11:27. Version ac07

Copyright © 2024 Attilla Danko.