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 2024-11-08.

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 8% 5% 4 4 4 5% 7% 31%	101188
	Night	17% 11% 4 8% 5% 4 4 3 5% 6% 32%	97854
Transparency	Day	50% 7% 12% 20% 10% 1	104835
	Night	50% 7% 11% 20% 11% 2	102347
Seeing	Day	22% 15% 27% 20% 12% 4	14730
	Night	21% 12% 26% 27% 12% 1	24367

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	20% 21% 9% 12% 5% 3 3 2 3 5% 17%	2776
	11th to 20th	Day	13% 23% 8% 17% 9% 4 2 2 3 3 16%	2840
	21st to end	Day	26% 21% 7% 14% 6% 4 3 2 3 3 12%	3124
February	1st to 10th	Day	20% 17% 5% 12% 7% 5% 3 3 3 4 21%	1710
	11th to 20th	Day	17% 15% 6% 14% 5% 4 5% 3 5% 5% 21%	1663
	21st to end	Day	21% 16% 5% 10% 6% 4 3 3 4 5% 24%	1566
March	1st to 10th	Day	22% 11% 4 8% 5% 4 4 3 5% 5% 29%	3435
	11th to 20th	Day	15% 12% 5% 9% 6% 5% 5% 3 4 5% 32%	3480
	21st to end	Day	19% 11% 3 8% 5% 4 5% 4 5% 6% 31%	3815
April	1st to 10th	Day	16% 13% 3 8% 5% 5% 4 4 5% 7% 30%	2205
	11th to 20th	Day	17% 11% 3 8% 6% 4 5% 4 5% 6% 33%	2265
	21st to end	Day	21% 9% 4 7% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	25% 9% 3 7% 5% 4 4 4 5% 6% 28%	4082
	11th to 20th	Day	20% 8% 3 7% 6% 5% 5% 4 6% 7% 30%	4081
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 7% 9% 38%	4788
June	1st to 10th	Day	15% 7% 3 6% 5% 5% 5% 5% 7% 8% 34%	2660
	11th to 20th	Day	14% 7% 3 6% 5% 6% 5% 5% 7% 9% 34%	2660
	21st to end	Day	14% 6% 2 7% 6% 5% 4 4 6% 10% 37%	2660
July	1st to 10th	Day	9% 7% 2 7% 5% 5% 5% 5% 7% 8% 40%	4376
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 7% 10% 39%	4120
	21st to end	Day	12% 7% 3 8% 6% 5% 5% 5% 6% 7% 36%	4466
August	1st to 10th	Day	15% 9% 3 8% 5% 6% 6% 5% 7% 8% 30%	4104
	11th to 20th	Day	12% 7% 2 7% 5% 5% 6% 5% 7% 9% 35%	4044
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 41%	4287
September	1st to 10th	Day	17% 6% 2 5% 3 4 4 3 5% 6% 45%	2280
	11th to 20th	Day	13% 6% 2 5% 5% 3 4 5% 5% 7% 45%	2120
	21st to end	Day	21% 7% 3 7% 4 5% 4 3 5% 6% 35%	2075
October	1st to 10th	Day	17% 6% 2 5% 4 5% 4 4 5% 7% 40%	1900
	11th to 20th	Day	20% 8% 2 7% 4 5% 6% 3 5% 6% 35%	1900
	21st to end	Day	23% 9% 3 8% 4 3 3 3 5% 7% 33%	2090
November	1st to 10th	Day	12% 9% 2 7% 5% 4 4 3 5% 7% 41%	1869
	11th to 20th	Day	18% 14% 3 7% 5% 4 4 3 5% 6% 32%	1555
	21st to end	Day	19% 15% 5% 8% 5% 5% 4 3 5% 5% 26%	1520
December	1st to 10th	Day	21% 19% 6% 11% 6% 4 3 3 4 5% 17%	1520
	11th to 20th	Day	21% 18% 7% 10% 5% 2 3 3 3 6% 21%	1910
	21st to end	Day	24% 23% 7% 10% 5% 4 3 2 4 4 14%	2772
January	1st to 10th	Night	17% 21% 7% 12% 5% 4 4 3 4 4 19%	4164
	11th to 20th	Night	17% 18% 7% 14% 7% 6% 4 3 4 4 16%	4120
	21st to end	Night	28% 17% 7% 12% 6% 4 3 2 3 3 16%	4532
February	1st to 10th	Night	21% 14% 5% 9% 6% 5% 4 3 4 5% 25%	2470
	11th to 20th	Night	19% 13% 4 12% 5% 4 4 3 5% 4 25%	2403
	21st to end	Night	21% 13% 5% 11% 5% 4 5% 3 5% 5% 25%	1881
March	1st to 10th	Night	23% 11% 3 7% 4 3 3 3 4 6% 32%	3418
	11th to 20th	Night	18% 14% 5% 7% 3 3 3 3 4 6% 34%	3480
	21st to end	Night	18% 9% 3 7% 4 4 4 3 4 5% 39%	3817
April	1st to 10th	Night	18% 14% 2 6% 4 4 4 3 4 5% 35%	1974
	11th to 20th	Night	17% 7% 3 7% 4 4 4 4 5% 6% 38%	1875
	21st to end	Night	16% 9% 3 7% 4 4 4 3 5% 7% 37%	1714
May	1st to 10th	Night	27% 10% 2 7% 4 3 4 3 5% 6% 27%	2813
	11th to 20th	Night	18% 10% 3 7% 5% 4 3 3 5% 7% 35%	2812
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 7% 10% 39%	2763
June	1st to 10th	Night	11% 5% 2 6% 5% 4 5% 4 6% 8% 44%	1520
	11th to 20th	Night	12% 6% 2 7% 5% 4 5% 5% 6% 9% 40%	1520
	21st to end	Night	12% 5% 2 5% 5% 4 5% 5% 7% 10% 41%	1520
July	1st to 10th	Night	11% 9% 3 7% 5% 4 4 3 6% 8% 40%	2578
	11th to 20th	Night	11% 6% 2 7% 4 5% 5% 5% 6% 9% 41%	2840
	21st to end	Night	11% 8% 3 8% 5% 4 5% 5% 6% 7% 39%	3087
August	1st to 10th	Night	13% 8% 4 8% 5% 4 6% 4 7% 8% 34%	2825
	11th to 20th	Night	14% 7% 3 7% 4 4 4 4 5% 7% 41%	2785
	21st to end	Night	8% 6% 2 6% 4 5% 6% 5% 7% 8% 44%	3335
September	1st to 10th	Night	13% 5% 2 4 4 4 5% 4 5% 6% 49%	1900
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 6% 8% 51%	2057
	21st to end	Night	16% 9% 2 7% 5% 4 4 3 5% 6% 40%	2104
October	1st to 10th	Night	15% 6% 3 5% 4 3 4 3 5% 7% 44%	2280
	11th to 20th	Night	19% 6% 2 6% 5% 4 5% 4 4 6% 40%	2280
	21st to end	Night	22% 9% 3 5% 4 4 3 3 3 7% 37%	2508
November	1st to 10th	Night	13% 9% 3 7% 4 3 4 4 4 7% 44%	2368
	11th to 20th	Night	19% 12% 3 7% 5% 5% 4 3 5% 6% 32%	2622
	21st to end	Night	20% 14% 4 7% 5% 3 4 3 4 7% 29%	2660
December	1st to 10th	Night	22% 17% 6% 9% 6% 4 4 3 4 5% 19%	2660
	11th to 20th	Night	20% 16% 6% 11% 5% 4 3 3 4 5% 23%	3285
	21st to end	Night	24% 19% 6% 9% 5% 5% 4 3 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% 7% 10% 11% 4	2777
	11th to 20th	Day	73% 5% 7% 11% 3 1	2840
	21st to end	Day	77% 6% 7% 8% 2	3124
February	1st to 10th	Day	68% 4 8% 14% 6% 1	1710
	11th to 20th	Day	64% 5% 12% 13% 6%	1672
	21st to end	Day	62% 6% 11% 14% 6% 1	1566
March	1st to 10th	Day	53% 8% 11% 21% 6%	3435
	11th to 20th	Day	51% 8% 13% 21% 6% 1	3480
	21st to end	Day	51% 8% 12% 19% 10% 1	3815
April	1st to 10th	Day	52% 8% 11% 17% 10% 2	2205
	11th to 20th	Day	49% 8% 11% 16% 14% 2	2265
	21st to end	Day	50% 7% 11% 21% 9% 2	2470
May	1st to 10th	Day	53% 9% 11% 19% 7% 1	4120
	11th to 20th	Day	50% 10% 13% 19% 8% 1	4085
	21st to end	Day	37% 12% 16% 21% 11% 2	4802
June	1st to 10th	Day	43% 11% 15% 20% 10% 1	2660
	11th to 20th	Day	43% 10% 14% 20% 12% 1	2660
	21st to end	Day	42% 9% 13% 25% 11% 1	2660
July	1st to 10th	Day	41% 8% 11% 23% 15% 3	4308
	11th to 20th	Day	39% 7% 13% 27% 14%	4051
	21st to end	Day	45% 6% 12% 19% 17% 1	4324
August	1st to 10th	Day	49% 8% 14% 20% 8%	4091
	11th to 20th	Day	43% 7% 12% 27% 10% 1	4083
	21st to end	Day	37% 7% 13% 27% 14% 2	4287
September	1st to 10th	Day	39% 8% 11% 20% 19% 3	2280
	11th to 20th	Day	36% 7% 15% 26% 15% 1	2120
	21st to end	Day	49% 5% 11% 21% 13% 1	2075
October	1st to 10th	Day	34% 5% 10% 31% 19% 1	3160
	11th to 20th	Day	44% 7% 10% 21% 13% 5%	3140
	21st to end	Day	37% 4 12% 28% 18% 1	3428
November	1st to 10th	Day	43% 6% 12% 20% 16% 2	1869
	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	67% 7% 10% 13% 3	4164
	11th to 20th	Night	70% 6% 11% 10% 2	4120
	21st to end	Night	74% 5% 7% 11% 3	4532
February	1st to 10th	Night	62% 6% 9% 16% 6%	2470
	11th to 20th	Night	61% 5% 11% 16% 7%	2405
	21st to end	Night	60% 6% 10% 14% 9% 1	1881
March	1st to 10th	Night	52% 7% 9% 24% 7%	3418
	11th to 20th	Night	50% 7% 12% 24% 6% 1	3480
	21st to end	Night	45% 7% 11% 22% 13% 2	3817
April	1st to 10th	Night	51% 6% 10% 18% 13% 2	1974
	11th to 20th	Night	44% 8% 12% 17% 15% 3	1875
	21st to end	Night	46% 7% 11% 22% 11% 3	1714
May	1st to 10th	Night	56% 7% 9% 16% 10% 2	2840
	11th to 20th	Night	47% 9% 13% 21% 9% 2	2813
	21st to end	Night	34% 14% 15% 22% 11% 4	2770
June	1st to 10th	Night	36% 10% 14% 24% 15% 2	1520
	11th to 20th	Night	38% 9% 15% 23% 13% 1	1520
	21st to end	Night	37% 9% 13% 24% 16% 1	1520
July	1st to 10th	Night	43% 7% 9% 22% 16% 3	2537
	11th to 20th	Night	38% 6% 15% 25% 15% 1	2786
	21st to end	Night	42% 8% 11% 16% 21% 2	2988
August	1st to 10th	Night	47% 8% 14% 21% 10%	2814
	11th to 20th	Night	41% 6% 10% 28% 13% 1	2812
	21st to end	Night	35% 7% 12% 30% 13% 2	3335
September	1st to 10th	Night	33% 8% 12% 23% 20% 4	1900
	11th to 20th	Night	30% 6% 14% 26% 22% 1	2057
	21st to end	Night	45% 6% 11% 21% 16% 1	2104
October	1st to 10th	Night	36% 6% 8% 26% 22% 1	3800
	11th to 20th	Night	38% 4 11% 24% 15% 8%	3779
	21st to end	Night	36% 3 10% 28% 21% 2	4120
November	1st to 10th	Night	41% 6% 12% 21% 17% 4	2368
	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	31% 30% 28% 7% 2 1	270
	21st to end	Day	28% 30% 29% 8% 4 1	297
February	1st to 10th	Day	31% 25% 35% 7% 1	270
	11th to 20th	Day	35% 30% 27% 7% 1	270
	21st to end	Day	39% 26% 28% 7% 1	269
March	1st to 10th	Day	28% 23% 30% 15% 5%	460
	11th to 20th	Day	33% 20% 30% 12% 5% 1	460
	21st to end	Day	31% 18% 30% 16% 5% 1	506
April	1st to 10th	Day	28% 23% 25% 17% 7% 1	460
	11th to 20th	Day	23% 23% 27% 15% 8% 4	452
	21st to end	Day	26% 21% 27% 18% 6% 2	460
May	1st to 10th	Day	30% 16% 25% 17% 8% 3	463
	11th to 20th	Day	21% 13% 30% 20% 11% 4	487
	21st to end	Day	17% 8% 26% 27% 16% 6%	529
June	1st to 10th	Day	16% 10% 31% 25% 15% 4	490
	11th to 20th	Day	17% 13% 23% 28% 15% 4	490
	21st to end	Day	15% 10% 31% 27% 14% 3	490
July	1st to 10th	Day	11% 7% 23% 27% 21% 10%	485
	11th to 20th	Day	12% 7% 27% 29% 17% 8%	484
	21st to end	Day	15% 6% 25% 31% 18% 6%	532
August	1st to 10th	Day	13% 8% 22% 27% 20% 9%	486
	11th to 20th	Day	16% 7% 22% 26% 19% 10%	479
	21st to end	Day	11% 6% 24% 26% 23% 10%	539
September	1st to 10th	Day	16% 9% 21% 27% 19% 9%	490
	11th to 20th	Day	14% 3 19% 32% 22% 10%	490
	21st to end	Day	26% 11% 22% 24% 13% 5%	490
October	1st to 10th	Day	18% 10% 27% 23% 18% 4	490
	11th to 20th	Day	23% 16% 27% 23% 9% 2	490
	21st to end	Day	27% 17% 30% 17% 8% 1	539
November	1st to 10th	Day	20% 15% 32% 21% 10% 4	425
	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% 18% 30% 18% 3	760
	21st to end	Night	28% 20% 30% 19% 3	836
February	1st to 10th	Night	28% 18% 29% 24% 2	760
	11th to 20th	Night	29% 20% 35% 15% 1	743
	21st to end	Night	29% 16% 34% 20% 2	628
March	1st to 10th	Night	24% 18% 31% 23% 3	760
	11th to 20th	Night	28% 18% 27% 21% 6% 1	760
	21st to end	Night	24% 16% 33% 22% 5% 1	836
April	1st to 10th	Night	26% 17% 29% 22% 5%	760
	11th to 20th	Night	22% 12% 32% 24% 9% 1	751
	21st to end	Night	19% 11% 33% 30% 6%	574
May	1st to 10th	Night	22% 11% 25% 33% 8% 1	570
	11th to 20th	Night	21% 8% 27% 33% 11%	561
	21st to end	Night	10% 5% 25% 33% 24% 3	430
June	1st to 10th	Night	11% 6% 25% 41% 16% 1	380
	11th to 20th	Night	13% 4 25% 37% 20% 1	380
	21st to end	Night	12% 3 29% 37% 18% 1	380
July	1st to 10th	Night	10% 2 21% 41% 21% 5%	401
	11th to 20th	Night	10% 3 19% 35% 28% 4	552
	21st to end	Night	11% 3 16% 41% 27% 2	624
August	1st to 10th	Night	8% 4 15% 43% 28% 2	567
	11th to 20th	Night	12% 4 16% 36% 28% 4	564
	21st to end	Night	11% 5% 18% 33% 28% 5%	747
September	1st to 10th	Night	14% 4 19% 34% 24% 4	760
	11th to 20th	Night	12% 4 16% 37% 27% 4	760
	21st to end	Night	19% 9% 23% 27% 19% 3	760
October	1st to 10th	Night	18% 7% 23% 30% 21% 2	760
	11th to 20th	Night	21% 12% 27% 29% 11% 1	760
	21st to end	Night	25% 14% 26% 27% 8%	836
November	1st to 10th	Night	17% 11% 29% 31% 12%	771
	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 2024-11-05 08:15:53. Version ac07

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