Oakland/Lyons Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oakland/Lyons Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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	11% 7% 3 6% 5% 3 4 4 5% 7% 44%	74944
	Night	10% 7% 3 6% 5% 3 4 4 5% 7% 47%	74829
Transparency	Day	39% 7% 14% 25% 14% 2	74666
	Night	36% 6% 14% 26% 16% 2	74628
Seeing	Day	14% 9% 31% 29% 14% 3	14671
	Night	13% 9% 34% 33% 10% 1	24695

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	8% 10% 4 8% 7% 5% 5% 5% 5% 7% 36%	1707
	11th to 20th	Day	9% 10% 5% 9% 7% 3 4 4 5% 8% 36%	1656
	21st to end	Day	10% 10% 5% 11% 8% 3 5% 6% 5% 7% 30%	1782
February	1st to 10th	Day	10% 10% 7% 9% 8% 4 4 5% 6% 6% 33%	1620
	11th to 20th	Day	10% 9% 4 7% 7% 2 5% 5% 5% 6% 40%	1606
	21st to end	Day	12% 9% 4 8% 5% 4 6% 4 5% 6% 37%	1480
March	1st to 10th	Day	11% 9% 3 8% 5% 3 4 3 4 6% 44%	1930
	11th to 20th	Day	14% 11% 4 5% 5% 2 4 5% 4 7% 39%	1980
	21st to end	Day	18% 13% 4 7% 5% 3 4 4 5% 6% 31%	2178
April	1st to 10th	Day	13% 9% 3 6% 5% 3 4 3 5% 7% 41%	2024
	11th to 20th	Day	18% 9% 3 6% 5% 2 3 4 5% 7% 38%	2271
	21st to end	Day	20% 8% 3 5% 5% 2 4 4 4 6% 39%	2340
May	1st to 10th	Day	16% 7% 4 6% 5% 3 5% 6% 6% 7% 36%	2340
	11th to 20th	Day	14% 8% 3 5% 6% 4 5% 4 6% 8% 39%	2302
	21st to end	Day	16% 7% 2 6% 6% 4 5% 5% 5% 7% 36%	2629
June	1st to 10th	Day	8% 4 2 5% 5% 3 5% 5% 6% 8% 50%	2520
	11th to 20th	Day	10% 4 2 5% 5% 3 5% 5% 6% 8% 46%	2548
	21st to end	Day	7% 5% 2 5% 5% 3 4 5% 6% 8% 50%	2700
July	1st to 10th	Day	7% 3 2 4 4 3 5% 6% 7% 9% 51%	2517
	11th to 20th	Day	6% 3 2 5% 3 3 4 5% 6% 8% 55%	2340
	21st to end	Day	6% 3 2 4 4 3 5% 6% 8% 10% 50%	2546
August	1st to 10th	Day	8% 6% 3 6% 7% 4 6% 5% 7% 8% 41%	2328
	11th to 20th	Day	9% 5% 2 4 4 3 4 5% 6% 9% 49%	2301
	21st to end	Day	8% 5% 2 4 4 2 4 4 6% 8% 53%	2556
September	1st to 10th	Day	12% 6% 2 4 5% 3 4 4 4 6% 51%	2080
	11th to 20th	Day	10% 5% 2 5% 4 2 3 3 4 7% 54%	1980
	21st to end	Day	11% 3 2 3 3 3 3 4 5% 7% 56%	1980
October	1st to 10th	Day	15% 5% 2 6% 4 2 3 4 4 5% 49%	1852
	11th to 20th	Day	11% 5% 3 4 4 2 3 3 4 5% 56%	1800
	21st to end	Day	14% 7% 3 5% 5% 2 3 3 4 6% 47%	1962
November	1st to 10th	Day	8% 6% 2 5% 4 2 4 4 5% 5% 53%	1673
	11th to 20th	Day	9% 8% 2 8% 5% 2 4 4 6% 6% 45%	1634
	21st to end	Day	13% 8% 3 6% 3 3 3 4 5% 8% 45%	1520
December	1st to 10th	Day	9% 7% 4 6% 5% 3 5% 4 5% 7% 45%	1520
	11th to 20th	Day	8% 9% 4 7% 6% 4 5% 7% 7% 7% 38%	1918
	21st to end	Day	15% 9% 5% 13% 7% 4 5% 4 5% 5% 26%	2824
January	1st to 10th	Night	7% 8% 4 7% 7% 4 6% 5% 5% 7% 40%	2458
	11th to 20th	Night	8% 11% 5% 9% 7% 3 4 5% 6% 7% 37%	2399
	21st to end	Night	11% 10% 4 8% 6% 2 4 4 5% 7% 39%	2574
February	1st to 10th	Night	12% 10% 4 8% 7% 3 4 5% 3 6% 39%	2340
	11th to 20th	Night	8% 9% 4 6% 5% 3 5% 5% 6% 7% 43%	2255
	21st to end	Night	10% 7% 4 6% 5% 3 5% 4 4 6% 47%	1776
March	1st to 10th	Night	11% 7% 4 6% 4 3 4 4 5% 6% 46%	2030
	11th to 20th	Night	15% 9% 3 6% 4 2 3 5% 5% 6% 44%	1980
	21st to end	Night	17% 11% 4 6% 6% 3 4 6% 4 6% 34%	2178
April	1st to 10th	Night	13% 7% 3 5% 6% 3 4 4 5% 7% 43%	1934
	11th to 20th	Night	13% 7% 3 5% 6% 4 3 4 4 5% 45%	1634
	21st to end	Night	16% 7% 3 5% 6% 3 4 5% 5% 8% 41%	1620
May	1st to 10th	Night	14% 6% 3 5% 4 2 4 4 6% 10% 42%	1620
	11th to 20th	Night	12% 6% 3 5% 4 2 4 4 5% 9% 46%	1593
	21st to end	Night	14% 5% 2 6% 6% 3 5% 4 6% 8% 40%	1644
June	1st to 10th	Night	8% 3 2 3 4 3 3 5% 6% 9% 55%	1440
	11th to 20th	Night	7% 4 3 4 3 2 4 5% 6% 8% 53%	1402
	21st to end	Night	4 3 2 3 4 2 4 5% 6% 9% 59%	1260
July	1st to 10th	Night	6% 4 2 3 4 2 4 4 6% 9% 57%	1429
	11th to 20th	Night	3 2 1 3 4 3 4 4 6% 10% 61%	1620
	21st to end	Night	3 2 2 3 4 2 3 5% 6% 10% 59%	1772
August	1st to 10th	Night	5% 4 2 5% 6% 3 5% 6% 6% 9% 50%	1611
	11th to 20th	Night	7% 3 2 4 3 2 3 3 6% 8% 58%	1600
	21st to end	Night	6% 4 2 4 3 2 4 5% 6% 8% 57%	1800
September	1st to 10th	Night	8% 4 2 4 3 2 4 4 5% 6% 58%	1876
	11th to 20th	Night	8% 4 2 3 3 2 4 4 5% 7% 58%	1980
	21st to end	Night	8% 4 2 4 4 2 3 3 4 5% 60%	1980
October	1st to 10th	Night	14% 6% 2 4 4 2 4 4 5% 7% 49%	2089
	11th to 20th	Night	12% 7% 2 4 4 2 2 3 4 5% 55%	2160
	21st to end	Night	14% 6% 2 4 4 2 3 4 4 5% 53%	2389
November	1st to 10th	Night	7% 4 2 4 4 3 4 4 4 7% 57%	2405
	11th to 20th	Night	9% 6% 3 5% 4 3 4 4 4 6% 52%	2543
	21st to end	Night	10% 8% 3 5% 3 3 3 4 5% 6% 51%	2660
December	1st to 10th	Night	8% 8% 3 7% 5% 3 4 4 5% 7% 45%	2660
	11th to 20th	Night	9% 8% 4 6% 5% 3 4 5% 5% 7% 46%	3279
	21st to end	Night	16% 12% 5% 11% 7% 2 3 3 4 5% 32%	4839

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	46% 7% 17% 19% 10% 1	1708
	11th to 20th	Day	46% 6% 16% 22% 9% 1	1656
	21st to end	Day	52% 7% 16% 17% 8%	1782
February	1st to 10th	Day	51% 7% 14% 16% 10% 1	1620
	11th to 20th	Day	44% 6% 14% 21% 13% 2	1615
	21st to end	Day	46% 7% 12% 21% 11% 3	1480
March	1st to 10th	Day	42% 6% 13% 27% 11% 2	1930
	11th to 20th	Day	46% 6% 12% 23% 12% 2	1980
	21st to end	Day	53% 8% 14% 17% 7% 1	2178
April	1st to 10th	Day	44% 6% 13% 25% 11% 1	2024
	11th to 20th	Day	46% 6% 13% 21% 12% 2	2271
	21st to end	Day	45% 6% 12% 25% 11%	2340
May	1st to 10th	Day	46% 7% 13% 19% 13% 1	2340
	11th to 20th	Day	43% 8% 14% 25% 10% 1	2306
	21st to end	Day	46% 8% 14% 20% 11% 1	2629
June	1st to 10th	Day	31% 9% 17% 28% 13% 2	2520
	11th to 20th	Day	34% 7% 14% 26% 17% 2	2548
	21st to end	Day	30% 7% 15% 30% 14% 3	2700
July	1st to 10th	Day	27% 9% 16% 30% 15% 2	2452
	11th to 20th	Day	25% 8% 14% 29% 18% 5%	2271
	21st to end	Day	25% 9% 17% 29% 18% 2	2405
August	1st to 10th	Day	38% 8% 16% 23% 12% 1	2314
	11th to 20th	Day	30% 7% 15% 31% 16% 1	2301
	21st to end	Day	28% 8% 14% 25% 20% 5%	2556
September	1st to 10th	Day	34% 6% 11% 27% 18% 4	2080
	11th to 20th	Day	31% 6% 12% 33% 17% 1	1980
	21st to end	Day	28% 6% 12% 30% 23% 1	1980
October	1st to 10th	Day	38% 5% 11% 26% 19% 2	1852
	11th to 20th	Day	32% 4 11% 27% 21% 5%	1800
	21st to end	Day	39% 5% 13% 22% 18% 4	1962
November	1st to 10th	Day	31% 6% 16% 26% 19% 2	1673
	11th to 20th	Day	38% 7% 14% 24% 16% 1	1634
	21st to end	Day	39% 5% 14% 27% 14% 2	1520
December	1st to 10th	Day	39% 6% 16% 26% 11% 2	1520
	11th to 20th	Day	43% 8% 19% 26% 5%	1915
	21st to end	Day	57% 7% 11% 17% 7% 1	2824
January	1st to 10th	Night	43% 6% 13% 23% 14% 1	2458
	11th to 20th	Night	45% 7% 16% 23% 8%	2399
	21st to end	Night	44% 6% 17% 22% 10% 1	2574
February	1st to 10th	Night	47% 5% 14% 20% 12% 2	2340
	11th to 20th	Night	40% 7% 14% 22% 14% 3	2256
	21st to end	Night	38% 4 14% 24% 16% 3	1776
March	1st to 10th	Night	38% 6% 13% 29% 12% 2	2030
	11th to 20th	Night	42% 6% 10% 25% 15% 3	1980
	21st to end	Night	50% 8% 14% 19% 7% 2	2178
April	1st to 10th	Night	39% 7% 11% 25% 16% 1	1934
	11th to 20th	Night	41% 6% 10% 25% 16% 2	1634
	21st to end	Night	41% 6% 14% 23% 14% 1	1620
May	1st to 10th	Night	38% 8% 14% 24% 15% 2	1620
	11th to 20th	Night	35% 8% 17% 23% 16% 1	1594
	21st to end	Night	41% 9% 17% 18% 12% 3	1645
June	1st to 10th	Night	24% 8% 16% 34% 15% 3	1440
	11th to 20th	Night	28% 7% 14% 26% 20% 5%	1402
	21st to end	Night	21% 8% 18% 32% 18% 3	1260
July	1st to 10th	Night	23% 7% 16% 29% 21% 4	1386
	11th to 20th	Night	19% 8% 17% 31% 19% 6%	1566
	21st to end	Night	18% 7% 19% 31% 22% 3	1673
August	1st to 10th	Night	29% 9% 15% 28% 16% 2	1601
	11th to 20th	Night	24% 7% 14% 33% 19% 3	1600
	21st to end	Night	25% 7% 14% 25% 20% 9%	1800
September	1st to 10th	Night	26% 6% 11% 30% 22% 5%	1876
	11th to 20th	Night	24% 7% 12% 33% 21% 2	1980
	21st to end	Night	27% 5% 9% 31% 24% 4	1980
October	1st to 10th	Night	35% 5% 11% 23% 24% 2	2089
	11th to 20th	Night	32% 4 9% 26% 25% 5%	2160
	21st to end	Night	34% 4 15% 24% 22% 2	2389
November	1st to 10th	Night	26% 5% 17% 26% 23% 4	2405
	11th to 20th	Night	33% 5% 14% 28% 17% 3	2543
	21st to end	Night	35% 6% 12% 29% 17% 2	2660
December	1st to 10th	Night	39% 6% 15% 28% 12% 1	2660
	11th to 20th	Night	38% 5% 17% 32% 7%	3281
	21st to end	Night	55% 6% 11% 21% 7% 1	4839

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% 14% 34% 25% 11%	270
	11th to 20th	Day	18% 11% 38% 28% 4 1	252
	21st to end	Day	16% 9% 43% 26% 5%	264
February	1st to 10th	Day	18% 16% 39% 25% 3	240
	11th to 20th	Day	16% 15% 38% 24% 6%	240
	21st to end	Day	21% 16% 36% 21% 6%	198
March	1st to 10th	Day	15% 15% 43% 20% 5% 2	240
	11th to 20th	Day	23% 15% 37% 18% 7%	240
	21st to end	Day	33% 14% 31% 18% 3 1	264
April	1st to 10th	Day	20% 15% 43% 19% 4	284
	11th to 20th	Day	21% 15% 35% 22% 7%	549
	21st to end	Day	25% 13% 31% 20% 9% 2	600
May	1st to 10th	Day	20% 14% 32% 23% 8% 2	603
	11th to 20th	Day	18% 11% 30% 25% 13% 3	625
	21st to end	Day	18% 9% 28% 29% 13% 3	679
June	1st to 10th	Day	6% 7% 27% 36% 20% 4	630
	11th to 20th	Day	10% 4 35% 33% 16% 3	630
	21st to end	Day	8% 8% 29% 37% 15% 3	630
July	1st to 10th	Day	7% 3 20% 37% 26% 7%	621
	11th to 20th	Day	6% 4 24% 39% 19% 7%	618
	21st to end	Day	5% 2 23% 44% 23% 2	684
August	1st to 10th	Day	9% 2 21% 37% 26% 4	626
	11th to 20th	Day	9% 4 23% 38% 24% 3	615
	21st to end	Day	9% 3 25% 36% 23% 4	675
September	1st to 10th	Day	15% 5% 26% 36% 15% 3	370
	11th to 20th	Day	8% 6% 33% 33% 15% 5%	270
	21st to end	Day	13% 9% 31% 31% 14% 2	270
October	1st to 10th	Day	19% 9% 32% 23% 12% 5%	270
	11th to 20th	Day	13% 16% 39% 23% 7% 2	270
	21st to end	Day	19% 14% 33% 24% 9%	297
November	1st to 10th	Day	16% 14% 39% 19% 10% 2	270
	11th to 20th	Day	13% 16% 46% 20% 6%	270
	21st to end	Day	22% 14% 28% 29% 7%	270
December	1st to 10th	Day	9% 15% 39% 25% 10% 1	270
	11th to 20th	Day	16% 12% 39% 25% 8%	270
	21st to end	Day	23% 15% 39% 20% 3	297
January	1st to 10th	Night	12% 14% 35% 33% 6% 1	950
	11th to 20th	Night	14% 12% 38% 29% 7% 1	923
	21st to end	Night	16% 9% 43% 26% 5%	990
February	1st to 10th	Night	16% 11% 40% 29% 4	900
	11th to 20th	Night	13% 11% 43% 28% 5%	861
	21st to end	Night	14% 11% 43% 27% 6%	592
March	1st to 10th	Night	12% 14% 39% 28% 6% 1	590
	11th to 20th	Night	21% 9% 37% 27% 7%	540
	21st to end	Night	22% 11% 38% 25% 5%	594
April	1st to 10th	Night	17% 14% 41% 25% 4	540
	11th to 20th	Night	17% 12% 40% 27% 4 1	533
	21st to end	Night	20% 9% 35% 28% 8%	540
May	1st to 10th	Night	17% 9% 32% 34% 8%	540
	11th to 20th	Night	13% 10% 31% 35% 11%	531
	21st to end	Night	16% 5% 33% 34% 11% 1	584
June	1st to 10th	Night	7% 4 25% 47% 16% 1	540
	11th to 20th	Night	9% 6% 32% 40% 13%	540
	21st to end	Night	5% 4 32% 45% 14%	540
July	1st to 10th	Night	7% 2 20% 42% 26% 2	525
	11th to 20th	Night	3 1 22% 50% 23% 2	522
	21st to end	Night	4 2 15% 57% 21%	591
August	1st to 10th	Night	6% 2 21% 45% 25% 1	537
	11th to 20th	Night	9% 4 19% 45% 23% 1	534
	21st to end	Night	7% 2 27% 41% 21% 3	594
September	1st to 10th	Night	9% 5% 27% 39% 19% 1	540
	11th to 20th	Night	11% 2 31% 41% 14% 1	540
	21st to end	Night	9% 7% 36% 32% 14% 1	540
October	1st to 10th	Night	17% 8% 32% 31% 11% 1	649
	11th to 20th	Night	14% 13% 36% 30% 6%	720
	21st to end	Night	17% 12% 29% 31% 11%	805
November	1st to 10th	Night	9% 10% 39% 34% 8% 1	925
	11th to 20th	Night	12% 12% 42% 28% 6%	950
	21st to end	Night	14% 12% 39% 25% 10%	950
December	1st to 10th	Night	14% 11% 41% 29% 5%	950
	11th to 20th	Night	14% 10% 37% 32% 7%	950
	21st to end	Night	19% 13% 36% 27% 5%	1045

Page generated at 2024-01-12 06:31:47. Version ac07

Copyright 2024 Attilla Danko