Edgewood Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edgewood Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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	17% 10% 4 7% 6% 3 5% 5% 5% 7% 31%	74607
	Night	17% 10% 4 7% 5% 3 4 4 5% 7% 33%	75110
Transparency	Day	51% 8% 13% 18% 9% 1	74325
	Night	50% 7% 12% 19% 11% 2	74912
Seeing	Day	22% 15% 26% 20% 12% 4	13575
	Night	21% 12% 26% 27% 12% 1	23338

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	19% 16% 8% 12% 7% 3 4 3 3 5% 19%	1672
	11th to 20th	Day	18% 20% 7% 12% 9% 3 3 2 3 4 17%	1635
	21st to end	Day	18% 18% 8% 12% 9% 4 3 3 4 4 17%	1782
February	1st to 10th	Day	21% 15% 6% 11% 8% 4 4 4 3 4 19%	1620
	11th to 20th	Day	17% 14% 8% 12% 6% 3 4 5% 4 5% 20%	1573
	21st to end	Day	21% 15% 5% 9% 7% 3 4 4 4 5% 24%	1476
March	1st to 10th	Day	17% 11% 4 8% 6% 3 4 5% 4 5% 32%	1980
	11th to 20th	Day	20% 12% 4 7% 6% 3 4 5% 4 6% 29%	1980
	21st to end	Day	21% 11% 5% 8% 6% 3 4 5% 5% 6% 27%	2178
April	1st to 10th	Day	16% 11% 4 7% 6% 4 5% 5% 5% 7% 31%	2088
	11th to 20th	Day	18% 10% 3 7% 6% 3 5% 5% 5% 6% 33%	2144
	21st to end	Day	22% 8% 4 6% 5% 3 4 4 5% 7% 33%	2340
May	1st to 10th	Day	20% 9% 3 5% 6% 4 5% 6% 6% 8% 29%	2340
	11th to 20th	Day	22% 7% 3 6% 7% 4 5% 5% 5% 7% 29%	2301
	21st to end	Day	13% 5% 2 5% 5% 4 5% 6% 8% 9% 38%	2704
June	1st to 10th	Day	15% 6% 2 6% 6% 3 6% 6% 6% 9% 35%	2520
	11th to 20th	Day	14% 7% 3 6% 5% 4 6% 6% 7% 9% 34%	2520
	21st to end	Day	14% 6% 2 6% 7% 3 4 5% 6% 10% 37%	2520
July	1st to 10th	Day	12% 6% 3 5% 6% 3 5% 6% 6% 7% 40%	2484
	11th to 20th	Day	13% 6% 3 5% 5% 4 5% 5% 7% 11% 37%	2340
	21st to end	Day	13% 6% 3 6% 7% 4 6% 7% 6% 8% 35%	2547
August	1st to 10th	Day	11% 5% 2 5% 7% 5% 6% 6% 7% 10% 34%	2327
	11th to 20th	Day	14% 6% 2 5% 6% 4 6% 6% 7% 10% 34%	2303
	21st to end	Day	14% 5% 2 5% 6% 3 5% 6% 6% 9% 38%	2441
September	1st to 10th	Day	18% 6% 2 5% 4 3 4 4 5% 6% 43%	2160
	11th to 20th	Day	14% 6% 2 5% 5% 3 4 6% 5% 7% 44%	2009
	21st to end	Day	19% 7% 3 6% 5% 4 4 4 5% 7% 37%	1966
October	1st to 10th	Day	17% 6% 3 4 6% 3 4 6% 5% 7% 39%	1800
	11th to 20th	Day	21% 8% 3 6% 5% 4 6% 4 5% 6% 34%	1800
	21st to end	Day	24% 9% 3 7% 5% 3 3 4 5% 6% 31%	1980
November	1st to 10th	Day	13% 9% 3 6% 6% 4 4 3 5% 7% 41%	1800
	11th to 20th	Day	18% 13% 4 5% 6% 2 5% 3 5% 6% 32%	1555
	21st to end	Day	19% 14% 5% 8% 6% 4 4 4 5% 5% 26%	1520
December	1st to 10th	Day	21% 17% 7% 10% 7% 4 4 3 4 5% 18%	1520
	11th to 20th	Day	21% 17% 8% 9% 6% 2 3 4 3 6% 21%	1910
	21st to end	Day	25% 22% 8% 9% 6% 3 3 3 4 4 14%	2772
January	1st to 10th	Night	19% 17% 6% 10% 6% 4 5% 4 4 4 20%	2488
	11th to 20th	Night	21% 16% 5% 11% 7% 3 4 4 4 4 20%	2365
	21st to end	Night	19% 15% 7% 10% 7% 3 4 3 4 4 22%	2574
February	1st to 10th	Night	22% 13% 6% 9% 7% 4 5% 4 4 5% 23%	2340
	11th to 20th	Night	20% 12% 5% 12% 6% 3 5% 4 5% 4 24%	2273
	21st to end	Night	21% 12% 5% 9% 6% 3 5% 4 5% 5% 25%	1773
March	1st to 10th	Night	18% 10% 4 7% 6% 3 4 5% 4 6% 33%	1980
	11th to 20th	Night	20% 10% 3 6% 5% 3 3 3 4 8% 34%	1980
	21st to end	Night	19% 10% 5% 7% 5% 3 5% 4 3 5% 34%	2178
April	1st to 10th	Night	19% 12% 3 6% 5% 3 4 4 3 5% 36%	1871
	11th to 20th	Night	17% 6% 3 7% 5% 3 5% 5% 6% 6% 38%	1775
	21st to end	Night	16% 9% 4 7% 5% 3 4 4 4 7% 37%	1624
May	1st to 10th	Night	19% 8% 3 6% 5% 3 5% 5% 6% 5% 34%	1620
	11th to 20th	Night	19% 8% 3 6% 5% 3 3 5% 5% 8% 35%	1592
	21st to end	Night	10% 5% 2 4 4 3 5% 5% 6% 10% 45%	1567
June	1st to 10th	Night	12% 5% 3 5% 5% 3 5% 5% 5% 9% 44%	1440
	11th to 20th	Night	12% 6% 2 6% 5% 3 5% 6% 6% 9% 40%	1440
	21st to end	Night	12% 4 2 3 5% 3 5% 6% 6% 11% 42%	1440
July	1st to 10th	Night	9% 5% 3 6% 5% 3 5% 5% 6% 9% 43%	1470
	11th to 20th	Night	10% 4 2 5% 5% 3 5% 5% 5% 10% 46%	1620
	21st to end	Night	10% 6% 2 5% 6% 4 5% 7% 7% 10% 38%	1771
August	1st to 10th	Night	7% 5% 3 5% 6% 3 5% 7% 8% 9% 44%	1611
	11th to 20th	Night	11% 6% 3 6% 5% 3 5% 5% 6% 9% 43%	1598
	21st to end	Night	11% 6% 2 5% 4 3 5% 6% 7% 8% 44%	1895
September	1st to 10th	Night	13% 4 2 4 4 3 5% 5% 5% 7% 48%	1800
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 6% 8% 51%	1948
	21st to end	Night	16% 8% 2 5% 6% 2 4 4 5% 6% 42%	1993
October	1st to 10th	Night	15% 6% 3 5% 5% 2 5% 4 5% 7% 43%	2160
	11th to 20th	Night	19% 6% 2 6% 6% 3 5% 5% 4 6% 38%	2160
	21st to end	Night	24% 9% 3 5% 5% 2 4 4 3 7% 35%	2376
November	1st to 10th	Night	13% 9% 3 6% 5% 2 4 4 4 7% 43%	2277
	11th to 20th	Night	19% 11% 3 6% 5% 3 5% 4 4 7% 32%	2622
	21st to end	Night	20% 13% 4 6% 5% 3 4 4 4 7% 30%	2660
December	1st to 10th	Night	23% 16% 8% 9% 6% 3 4 3 4 5% 19%	2660
	11th to 20th	Night	20% 16% 6% 9% 6% 3 4 4 4 5% 24%	3285
	21st to end	Night	25% 18% 7% 8% 7% 4 4 4 4 5% 14%	4884

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	69% 5% 11% 11% 4	1673
	11th to 20th	Day	72% 4 11% 11% 2	1635
	21st to end	Day	72% 5% 10% 10% 3	1782
February	1st to 10th	Day	70% 4 8% 12% 5% 1	1620
	11th to 20th	Day	66% 5% 12% 13% 5%	1582
	21st to end	Day	63% 5% 11% 14% 6% 1	1476
March	1st to 10th	Day	53% 7% 12% 20% 7%	1980
	11th to 20th	Day	57% 6% 11% 16% 9% 2	1980
	21st to end	Day	57% 6% 10% 16% 10% 2	2178
April	1st to 10th	Day	51% 7% 11% 18% 10% 2	2088
	11th to 20th	Day	50% 8% 11% 15% 14% 2	2144
	21st to end	Day	51% 7% 10% 20% 9% 2	2340
May	1st to 10th	Day	51% 9% 13% 17% 9% 2	2340
	11th to 20th	Day	53% 9% 11% 15% 11% 2	2305
	21st to end	Day	40% 11% 19% 21% 8% 2	2704
June	1st to 10th	Day	44% 10% 15% 20% 10% 1	2520
	11th to 20th	Day	44% 10% 14% 19% 11% 1	2520
	21st to end	Day	42% 9% 13% 24% 11% 1	2520
July	1st to 10th	Day	41% 10% 12% 20% 13% 3	2416
	11th to 20th	Day	39% 10% 16% 22% 13% 1	2271
	21st to end	Day	44% 9% 14% 19% 13% 1	2405
August	1st to 10th	Day	41% 12% 17% 23% 8%	2314
	11th to 20th	Day	41% 10% 16% 22% 9% 1	2303
	21st to end	Day	39% 10% 14% 22% 12% 3	2441
September	1st to 10th	Day	41% 8% 11% 19% 17% 3	2160
	11th to 20th	Day	37% 7% 15% 26% 14% 1	2009
	21st to end	Day	47% 6% 12% 22% 14% 1	1966
October	1st to 10th	Day	42% 8% 15% 19% 15% 1	1800
	11th to 20th	Day	48% 8% 12% 22% 10%	1800
	21st to end	Day	52% 6% 13% 18% 10% 1	1980
November	1st to 10th	Day	43% 6% 12% 20% 16% 3	1800
	11th to 20th	Day	53% 6% 12% 17% 10% 2	1555
	21st to end	Day	59% 6% 12% 17% 5% 1	1520
December	1st to 10th	Day	70% 6% 10% 11% 3	1520
	11th to 20th	Day	66% 5% 11% 14% 3	1906
	21st to end	Day	73% 6% 9% 10% 2	2772
January	1st to 10th	Night	66% 6% 9% 14% 5% 1	2488
	11th to 20th	Night	68% 5% 12% 12% 2	2365
	21st to end	Night	66% 5% 10% 13% 5% 1	2574
February	1st to 10th	Night	64% 6% 10% 15% 6%	2340
	11th to 20th	Night	63% 5% 11% 15% 7%	2275
	21st to end	Night	61% 5% 9% 14% 9% 1	1773
March	1st to 10th	Night	51% 7% 10% 20% 11% 1	1980
	11th to 20th	Night	50% 6% 12% 20% 10% 2	1980
	21st to end	Night	52% 6% 9% 17% 13% 3	2178
April	1st to 10th	Night	51% 6% 10% 18% 13% 2	1871
	11th to 20th	Night	44% 7% 12% 17% 15% 3	1775
	21st to end	Night	46% 6% 11% 22% 11% 4	1624
May	1st to 10th	Night	50% 7% 10% 18% 12% 3	1620
	11th to 20th	Night	48% 7% 11% 17% 14% 3	1593
	21st to end	Night	33% 10% 16% 26% 13% 2	1568
June	1st to 10th	Night	36% 10% 14% 24% 15% 1	1440
	11th to 20th	Night	39% 9% 14% 23% 13% 1	1440
	21st to end	Night	36% 9% 13% 24% 16% 2	1440
July	1st to 10th	Night	37% 10% 12% 21% 16% 4	1429
	11th to 20th	Night	31% 9% 16% 24% 18% 2	1566
	21st to end	Night	37% 11% 16% 20% 13% 3	1672
August	1st to 10th	Night	33% 10% 18% 24% 15%	1600
	11th to 20th	Night	36% 9% 15% 24% 14% 2	1598
	21st to end	Night	35% 9% 14% 25% 14% 4	1895
September	1st to 10th	Night	33% 8% 13% 23% 19% 4	1800
	11th to 20th	Night	30% 7% 14% 26% 21% 1	1948
	21st to end	Night	43% 6% 12% 22% 17% 1	1993
October	1st to 10th	Night	40% 9% 13% 23% 14% 2	2160
	11th to 20th	Night	46% 7% 11% 23% 12% 1	2160
	21st to end	Night	50% 5% 12% 20% 11% 1	2376
November	1st to 10th	Night	41% 6% 12% 21% 17% 4	2277
	11th to 20th	Night	52% 6% 11% 18% 10% 2	2622
	21st to end	Night	55% 6% 11% 20% 7% 1	2660
December	1st to 10th	Night	66% 6% 11% 12% 4	2660
	11th to 20th	Night	64% 5% 12% 16% 3	3288
	21st to end	Night	69% 9% 10% 9% 2	4884

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% 27% 26% 11% 4 2	254
	11th to 20th	Day	30% 28% 30% 8% 2 1	245
	21st to end	Day	27% 31% 30% 8% 4 1	264
February	1st to 10th	Day	33% 25% 37% 4 1	240
	11th to 20th	Day	35% 31% 28% 6%	240
	21st to end	Day	38% 26% 28% 6% 1	239
March	1st to 10th	Day	28% 24% 31% 14% 4	420
	11th to 20th	Day	32% 20% 31% 11% 5% 1	420
	21st to end	Day	31% 17% 29% 16% 5% 1	462
April	1st to 10th	Day	27% 23% 24% 17% 8% 1	420
	11th to 20th	Day	23% 22% 27% 16% 9% 4	412
	21st to end	Day	27% 20% 26% 17% 7% 2	420
May	1st to 10th	Day	30% 17% 24% 16% 9% 3	423
	11th to 20th	Day	22% 13% 31% 20% 10% 3	447
	21st to end	Day	19% 7% 25% 26% 17% 7%	485
June	1st to 10th	Day	16% 9% 31% 26% 15% 3	450
	11th to 20th	Day	19% 14% 22% 27% 15% 4	450
	21st to end	Day	15% 9% 31% 27% 16% 3	450
July	1st to 10th	Day	12% 7% 21% 27% 22% 11%	445
	11th to 20th	Day	12% 7% 26% 29% 18% 9%	444
	21st to end	Day	15% 6% 24% 30% 19% 7%	488
August	1st to 10th	Day	13% 7% 21% 28% 22% 10%	446
	11th to 20th	Day	16% 6% 21% 26% 20% 11%	439
	21st to end	Day	12% 6% 25% 26% 21% 10%	495
September	1st to 10th	Day	17% 8% 20% 26% 19% 10%	450
	11th to 20th	Day	15% 3 19% 31% 21% 11%	450
	21st to end	Day	23% 11% 21% 25% 13% 6%	450
October	1st to 10th	Day	18% 9% 27% 23% 19% 4	450
	11th to 20th	Day	24% 16% 28% 23% 8% 1	450
	21st to end	Day	29% 17% 29% 17% 7% 1	495
November	1st to 10th	Day	20% 15% 29% 21% 10% 4	398
	11th to 20th	Day	31% 20% 28% 13% 6% 2	196
	21st to end	Day	22% 25% 41% 10% 2 1	180
December	1st to 10th	Day	33% 26% 23% 12% 4 1	180
	11th to 20th	Day	33% 23% 31% 11% 3	180
	21st to end	Day	34% 22% 29% 12% 3	198
January	1st to 10th	Night	27% 24% 29% 16% 4	760
	11th to 20th	Night	31% 17% 31% 18% 3	728
	21st to end	Night	28% 20% 30% 19% 3	792
February	1st to 10th	Night	29% 18% 29% 22% 2	720
	11th to 20th	Night	29% 20% 36% 15% 1	703
	21st to end	Night	29% 17% 34% 19% 2	592
March	1st to 10th	Night	24% 18% 32% 22% 3	720
	11th to 20th	Night	27% 17% 28% 21% 7% 1	720
	21st to end	Night	24% 15% 33% 22% 5% 1	792
April	1st to 10th	Night	26% 17% 29% 23% 6%	720
	11th to 20th	Night	22% 12% 32% 24% 10% 1	711
	21st to end	Night	19% 11% 34% 29% 7%	544
May	1st to 10th	Night	21% 11% 26% 33% 8% 1	540
	11th to 20th	Night	22% 8% 27% 33% 11%	531
	21st to end	Night	11% 4 25% 33% 25% 3	407
June	1st to 10th	Night	11% 6% 25% 41% 17% 1	360
	11th to 20th	Night	14% 4 26% 35% 20% 1	360
	21st to end	Night	12% 3 29% 37% 19% 1	360
July	1st to 10th	Night	9% 3 21% 41% 22% 5%	379
	11th to 20th	Night	10% 3 19% 36% 29% 4	522
	21st to end	Night	11% 3 16% 40% 28% 2	591
August	1st to 10th	Night	7% 4 15% 43% 29% 2	537
	11th to 20th	Night	11% 4 15% 36% 29% 4	534
	21st to end	Night	11% 5% 18% 32% 28% 5%	707
September	1st to 10th	Night	14% 4 19% 34% 26% 4	720
	11th to 20th	Night	12% 4 16% 38% 27% 4	720
	21st to end	Night	18% 8% 22% 28% 20% 3	720
October	1st to 10th	Night	18% 7% 23% 30% 21% 2	720
	11th to 20th	Night	22% 12% 27% 29% 9% 1	720
	21st to end	Night	27% 14% 25% 27% 7%	792
November	1st to 10th	Night	17% 11% 28% 31% 12%	740
	11th to 20th	Night	26% 16% 27% 24% 6% 1	760
	21st to end	Night	28% 15% 29% 22% 6% 1	760
December	1st to 10th	Night	31% 18% 29% 18% 5%	760
	11th to 20th	Night	27% 20% 29% 21% 3	760
	21st to end	Night	28% 18% 30% 21% 2	836

Page generated at 2024-01-09 16:24:25. Version ac07

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