Cadmus Homestead Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cadmus Homestead Observatory clear sky chart from 2005-11-05 to 2024-10-14.

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	16% 7% 2 6% 4 4 4 4 6% 7% 39%	101152
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	97401
Transparency	Day	44% 5% 12% 24% 14% 2	100915
	Night	43% 5% 11% 24% 15% 2	97262
Seeing	Day	21% 14% 28% 22% 11% 4	14835
	Night	20% 12% 29% 28% 11% 1	24147

By Month

Percentage Cloud Cover NE (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% 9% 2 5% 4 4 5% 4 5% 6% 41%	2517
	11th to 20th	Day	15% 12% 5% 10% 5% 4 4 4 5% 6% 31%	2662
	21st to end	Day	20% 12% 4 8% 5% 4 4 3 4 4 32%	3124
February	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 5% 7% 35%	1710
	11th to 20th	Day	15% 9% 3 8% 4 4 4 3 6% 6% 38%	1748
	21st to end	Day	19% 9% 3 8% 4 4 4 3 4 5% 35%	1570
March	1st to 10th	Day	25% 6% 2 5% 4 4 4 3 5% 6% 36%	3230
	11th to 20th	Day	10% 6% 3 6% 6% 5% 5% 4 6% 8% 42%	3480
	21st to end	Day	22% 8% 2 5% 4 3 3 2 4 5% 43%	3969
April	1st to 10th	Day	17% 7% 3 6% 4 5% 4 4 5% 7% 37%	2280
	11th to 20th	Day	16% 8% 2 6% 4 3 4 4 6% 6% 42%	2254
	21st to end	Day	17% 6% 2 6% 5% 4 4 4 6% 7% 39%	2280
May	1st to 10th	Day	28% 7% 2 6% 4 4 4 4 5% 7% 30%	4114
	11th to 20th	Day	25% 9% 3 7% 5% 4 4 4 5% 6% 28%	4398
	21st to end	Day	13% 5% 2 5% 4 4 5% 4 6% 9% 44%	4837
June	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 5% 7% 10% 38%	2660
	11th to 20th	Day	13% 6% 2 6% 4 5% 6% 4 7% 9% 38%	2660
	21st to end	Day	11% 4 2 5% 5% 4 5% 5% 6% 11% 41%	2660
July	1st to 10th	Day	7% 5% 2 6% 6% 7% 6% 6% 9% 10% 36%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 9% 40%	4440
	21st to end	Day	11% 8% 3 8% 5% 6% 6% 5% 6% 7% 35%	4631
August	1st to 10th	Day	20% 6% 2 6% 5% 5% 5% 4 6% 7% 33%	4104
	11th to 20th	Day	15% 5% 2 5% 4 4 5% 4 7% 8% 41%	3826
	21st to end	Day	13% 5% 2 5% 3 4 3 3 5% 8% 48%	4180
September	1st to 10th	Day	16% 6% 2 6% 4 3 4 4 5% 6% 45%	2280
	11th to 20th	Day	12% 5% 2 4 4 3 4 3 6% 7% 50%	2280
	21st to end	Day	20% 8% 3 7% 4 4 4 3 5% 5% 38%	2031
October	1st to 10th	Day	19% 6% 2 4 3 4 4 3 5% 7% 43%	1900
	11th to 20th	Day	17% 5% 2 6% 3 4 4 3 4 7% 44%	1830
	21st to end	Day	19% 7% 2 6% 4 3 4 3 5% 7% 41%	1962
November	1st to 10th	Day	14% 7% 2 4 3 3 3 3 4 7% 49%	1671
	11th to 20th	Day	17% 5% 2 5% 4 3 4 4 5% 7% 44%	1706
	21st to end	Day	17% 6% 2 5% 5% 3 5% 3 6% 8% 41%	1520
December	1st to 10th	Day	19% 9% 2 7% 6% 4 4 4 6% 5% 35%	1520
	11th to 20th	Day	21% 7% 2 5% 3 4 4 4 5% 8% 38%	1906
	21st to end	Day	18% 9% 3 8% 5% 4 5% 4 6% 6% 31%	2772
January	1st to 10th	Night	16% 7% 3 6% 4 4 4 3 5% 8% 40%	4429
	11th to 20th	Night	18% 9% 3 6% 4 4 4 3 5% 7% 38%	4280
	21st to end	Night	23% 9% 3 8% 4 3 3 2 5% 5% 35%	4532
February	1st to 10th	Night	16% 8% 3 6% 5% 3 5% 4 5% 7% 38%	2470
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 3 5% 6% 39%	2316
	21st to end	Night	19% 7% 2 7% 5% 4 4 3 5% 7% 38%	1884
March	1st to 10th	Night	22% 10% 3 6% 4 4 4 3 4 5% 37%	3607
	11th to 20th	Night	11% 7% 2 5% 5% 4 4 3 5% 6% 47%	3479
	21st to end	Night	16% 8% 3 5% 4 3 3 2 4 5% 46%	3661
April	1st to 10th	Night	17% 7% 3 5% 6% 4 4 4 6% 7% 37%	1900
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 5% 7% 42%	1875
	21st to end	Night	18% 6% 2 5% 4 3 3 4 6% 6% 44%	1900
May	1st to 10th	Night	26% 8% 2 6% 3 4 4 4 5% 7% 31%	2857
	11th to 20th	Night	26% 8% 3 8% 5% 4 4 3 5% 7% 29%	2495
	21st to end	Night	14% 5% 3 6% 4 4 5% 4 6% 9% 42%	2738
June	1st to 10th	Night	14% 6% 2 7% 3 4 4 3 6% 8% 42%	1520
	11th to 20th	Night	13% 5% 2 6% 3 5% 5% 4 7% 9% 41%	1520
	21st to end	Night	11% 5% 2 5% 3 4 6% 5% 6% 9% 44%	1520
July	1st to 10th	Night	8% 5% 2 7% 5% 5% 7% 5% 8% 9% 39%	2520
	11th to 20th	Night	8% 5% 2 7% 5% 6% 6% 5% 8% 11% 38%	2520
	21st to end	Night	15% 7% 3 6% 5% 4 5% 4 6% 7% 39%	2918
August	1st to 10th	Night	21% 6% 2 6% 4 4 4 3 7% 8% 34%	2825
	11th to 20th	Night	15% 7% 3 7% 5% 4 5% 4 5% 6% 41%	2969
	21st to end	Night	13% 5% 2 5% 3 4 4 4 6% 8% 48%	3476
September	1st to 10th	Night	14% 7% 2 6% 4 4 3 2 4 6% 47%	1900
	11th to 20th	Night	13% 5% 2 4 3 3 4 3 5% 6% 52%	1900
	21st to end	Night	20% 6% 2 5% 3 4 5% 4 5% 5% 41%	2144
October	1st to 10th	Night	20% 6% 2 5% 4 4 3 3 4 6% 44%	2280
	11th to 20th	Night	16% 6% 2 6% 3 4 3 3 4 6% 47%	2203
	21st to end	Night	19% 6% 2 4 4 3 3 2 5% 7% 45%	2393
November	1st to 10th	Night	12% 5% 2 4 4 3 5% 3 5% 6% 52%	2407
	11th to 20th	Night	15% 7% 3 5% 4 3 3 3 5% 6% 45%	2471
	21st to end	Night	15% 5% 2 5% 4 4 4 4 5% 8% 44%	2660
December	1st to 10th	Night	19% 8% 2 7% 5% 4 5% 3 5% 6% 36%	2660
	11th to 20th	Night	18% 7% 2 6% 4 5% 4 4 5% 6% 39%	3288
	21st to end	Night	18% 8% 3 6% 5% 5% 4 4 6% 7% 33%	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	44% 4 13% 26% 10% 3	2518
	11th to 20th	Day	53% 5% 10% 17% 13% 2	2662
	21st to end	Day	55% 4 11% 21% 8% 1	3124
February	1st to 10th	Day	47% 6% 13% 22% 11% 1	1710
	11th to 20th	Day	46% 4 10% 24% 14% 2	1757
	21st to end	Day	52% 4 9% 22% 11% 3	1570
March	1st to 10th	Day	48% 5% 9% 26% 9% 2	3233
	11th to 20th	Day	38% 5% 11% 28% 14% 3	3480
	21st to end	Day	46% 3 9% 21% 19% 3	3969
April	1st to 10th	Day	44% 4 10% 22% 15% 5%	2280
	11th to 20th	Day	42% 5% 11% 22% 16% 4	2254
	21st to end	Day	43% 4 11% 22% 16% 4	2280
May	1st to 10th	Day	54% 5% 9% 20% 10% 2	4126
	11th to 20th	Day	55% 6% 12% 18% 8% 1	4402
	21st to end	Day	35% 7% 13% 27% 16% 2	4837
June	1st to 10th	Day	40% 7% 13% 24% 15% 2	2660
	11th to 20th	Day	40% 6% 15% 25% 11% 3	2660
	21st to end	Day	36% 7% 15% 26% 15% 1	2660
July	1st to 10th	Day	39% 8% 15% 22% 13% 2	4370
	11th to 20th	Day	37% 7% 16% 25% 14% 1	4365
	21st to end	Day	46% 6% 11% 19% 16% 1	4483
August	1st to 10th	Day	49% 7% 11% 24% 10%	4091
	11th to 20th	Day	39% 5% 11% 31% 13% 1	3865
	21st to end	Day	34% 5% 11% 29% 19% 2	4180
September	1st to 10th	Day	40% 5% 10% 21% 20% 4	2280
	11th to 20th	Day	33% 5% 9% 27% 23% 4	2280
	21st to end	Day	48% 4 7% 18% 20% 2	2031
October	1st to 10th	Day	41% 4 12% 24% 17% 2	1900
	11th to 20th	Day	41% 4 11% 24% 18% 1	1831
	21st to end	Day	42% 4 11% 25% 17% 2	1962
November	1st to 10th	Day	35% 4 14% 25% 18% 4	1671
	11th to 20th	Day	40% 4 11% 24% 19% 2	1706
	21st to end	Day	40% 5% 12% 31% 10% 2	1520
December	1st to 10th	Day	49% 4 16% 19% 11% 1	1520
	11th to 20th	Day	46% 4 14% 28% 8% 1	1906
	21st to end	Day	51% 5% 14% 21% 9% 1	2772
January	1st to 10th	Night	43% 4 12% 27% 10% 3	4429
	11th to 20th	Night	45% 5% 12% 24% 12% 2	4280
	21st to end	Night	51% 3 9% 26% 9% 1	4532
February	1st to 10th	Night	46% 4 13% 25% 11% 2	2470
	11th to 20th	Night	46% 4 9% 21% 18% 3	2318
	21st to end	Night	46% 4 9% 22% 15% 4	1884
March	1st to 10th	Night	50% 4 9% 23% 12% 2	3617
	11th to 20th	Night	36% 5% 12% 29% 16% 2	3480
	21st to end	Night	42% 3 8% 19% 23% 5%	3661
April	1st to 10th	Night	44% 4 10% 22% 15% 4	1900
	11th to 20th	Night	41% 5% 10% 20% 21% 2	1875
	21st to end	Night	40% 5% 11% 22% 17% 5%	1900
May	1st to 10th	Night	53% 5% 9% 20% 11% 2	2864
	11th to 20th	Night	55% 7% 14% 13% 11% 1	2496
	21st to end	Night	39% 6% 13% 23% 15% 4	2739
June	1st to 10th	Night	40% 6% 10% 23% 19% 2	1520
	11th to 20th	Night	37% 7% 14% 26% 14% 2	1520
	21st to end	Night	34% 7% 15% 27% 14% 2	1520
July	1st to 10th	Night	39% 8% 16% 17% 14% 5%	2480
	11th to 20th	Night	38% 7% 16% 24% 13% 1	2472
	21st to end	Night	43% 6% 13% 18% 19% 1	2825
August	1st to 10th	Night	47% 6% 17% 20% 10% 1	2814
	11th to 20th	Night	43% 4 11% 24% 16% 1	2996
	21st to end	Night	34% 4 12% 31% 18% 1	3476
September	1st to 10th	Night	38% 5% 10% 23% 20% 4	1900
	11th to 20th	Night	32% 5% 9% 25% 25% 4	1900
	21st to end	Night	44% 6% 7% 19% 21% 2	2144
October	1st to 10th	Night	43% 4 10% 25% 16% 2	2280
	11th to 20th	Night	38% 4 11% 29% 16% 2	2207
	21st to end	Night	39% 3 10% 28% 18% 2	2393
November	1st to 10th	Night	33% 5% 12% 27% 19% 4	2407
	11th to 20th	Night	40% 4 9% 25% 18% 4	2471
	21st to end	Night	38% 4 13% 29% 14% 1	2660
December	1st to 10th	Night	48% 4 12% 22% 13% 1	2660
	11th to 20th	Night	44% 5% 12% 22% 14% 3	3288
	21st to end	Night	47% 6% 14% 24% 9%	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	28% 26% 27% 14% 4 1	180
	11th to 20th	Day	33% 24% 30% 11% 2	222
	21st to end	Day	24% 30% 29% 13% 2 1	297
February	1st to 10th	Day	29% 23% 32% 13% 3	270
	11th to 20th	Day	31% 22% 37% 8% 2	355
	21st to end	Day	34% 19% 30% 16% 2	382
March	1st to 10th	Day	26% 21% 31% 18% 3	460
	11th to 20th	Day	26% 26% 30% 13% 3 1	460
	21st to end	Day	29% 21% 31% 14% 4 1	506
April	1st to 10th	Day	27% 21% 29% 16% 6% 1	460
	11th to 20th	Day	24% 21% 28% 18% 6% 2	452
	21st to end	Day	28% 14% 33% 18% 4 3	460
May	1st to 10th	Day	29% 17% 25% 18% 8% 2	463
	11th to 20th	Day	23% 15% 30% 22% 8% 2	487
	21st to end	Day	19% 6% 29% 25% 19% 3	529
June	1st to 10th	Day	16% 14% 30% 24% 14% 3	490
	11th to 20th	Day	18% 10% 28% 27% 14% 3	490
	21st to end	Day	14% 10% 32% 27% 12% 4	490
July	1st to 10th	Day	13% 5% 23% 31% 20% 8%	485
	11th to 20th	Day	8% 5% 25% 34% 23% 6%	484
	21st to end	Day	11% 6% 30% 30% 17% 5%	532
August	1st to 10th	Day	13% 6% 24% 28% 20% 8%	486
	11th to 20th	Day	16% 5% 20% 30% 19% 9%	479
	21st to end	Day	13% 5% 24% 31% 16% 11%	539
September	1st to 10th	Day	18% 9% 20% 26% 19% 8%	490
	11th to 20th	Day	14% 6% 22% 29% 17% 12%	490
	21st to end	Day	27% 11% 23% 21% 15% 4	490
October	1st to 10th	Day	22% 10% 24% 23% 15% 5%	490
	11th to 20th	Day	18% 15% 29% 23% 13% 2	462
	21st to end	Day	22% 15% 33% 20% 9% 2	486
November	1st to 10th	Day	19% 13% 28% 25% 12% 3	365
	11th to 20th	Day	20% 20% 30% 22% 7%	366
	21st to end	Day	23% 21% 36% 14% 6% 1	180
December	1st to 10th	Day	26% 22% 34% 12% 5% 1	180
	11th to 20th	Day	29% 23% 30% 14% 3 1	180
	21st to end	Day	26% 23% 26% 18% 6% 1	198
January	1st to 10th	Night	20% 19% 39% 19% 3	760
	11th to 20th	Night	27% 17% 31% 22% 3	760
	21st to end	Night	19% 19% 38% 21% 2	836
February	1st to 10th	Night	23% 17% 34% 24% 2	760
	11th to 20th	Night	25% 23% 36% 15% 2	743
	21st to end	Night	25% 20% 34% 17% 3	628
March	1st to 10th	Night	21% 18% 35% 21% 4	760
	11th to 20th	Night	24% 20% 32% 18% 5% 1	760
	21st to end	Night	22% 17% 36% 20% 5%	836
April	1st to 10th	Night	24% 19% 34% 19% 4	760
	11th to 20th	Night	19% 16% 34% 23% 7%	751
	21st to end	Night	23% 13% 32% 25% 7%	760
May	1st to 10th	Night	25% 10% 28% 28% 8%	594
	11th to 20th	Night	20% 9% 31% 32% 9% 1	374
	21st to end	Night	16% 6% 25% 37% 14% 1	411
June	1st to 10th	Night	17% 5% 26% 37% 16%	380
	11th to 20th	Night	13% 6% 27% 41% 12%	380
	21st to end	Night	12% 3 25% 48% 12% 1	380
July	1st to 10th	Night	11% 4 21% 43% 20% 2	370
	11th to 20th	Night	7% 4 22% 40% 26% 2	368
	21st to end	Night	11% 3 18% 42% 24% 1	520
August	1st to 10th	Night	12% 3 14% 43% 25% 3	567
	11th to 20th	Night	15% 4 14% 38% 27% 2	670
	21st to end	Night	15% 3 18% 36% 25% 2	836
September	1st to 10th	Night	15% 5% 23% 33% 21% 3	760
	11th to 20th	Night	14% 5% 18% 34% 26% 4	760
	21st to end	Night	23% 6% 19% 31% 20% 1	760
October	1st to 10th	Night	21% 8% 23% 27% 17% 3	760
	11th to 20th	Night	19% 10% 27% 31% 13%	735
	21st to end	Night	23% 12% 28% 27% 10%	792
November	1st to 10th	Night	16% 10% 31% 30% 12% 1	740
	11th to 20th	Night	20% 17% 28% 27% 7% 1	760
	21st to end	Night	18% 16% 33% 25% 7%	760
December	1st to 10th	Night	26% 15% 32% 20% 6%	760
	11th to 20th	Night	20% 16% 35% 24% 4	760
	21st to end	Night	22% 15% 33% 28% 1	836

Page generated at 2024-10-11 10:49:56. Version ac07

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