The Observatory at Tangleroot Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Observatory at Tangleroot Farm clear sky chart from 2005-11-06 to 2024-08-15.

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	14% 9% 3 9% 6% 5% 5% 4 6% 7% 32%	95577
	Night	15% 10% 4 9% 6% 5% 5% 4 5% 6% 32%	93154
Transparency	Day	49% 8% 13% 19% 9% 1	95296
	Night	51% 7% 13% 18% 9% 1	92989
Seeing	Day	22% 20% 30% 19% 7% 2	14395
	Night	20% 16% 29% 25% 8% 1	23344

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	11% 15% 4 12% 7% 6% 6% 5% 5% 6% 23%	2517
	11th to 20th	Day	12% 15% 8% 18% 6% 5% 4 3 4 5% 20%	2520
	21st to end	Day	12% 13% 4 12% 7% 6% 6% 4 6% 7% 22%	2772
February	1st to 10th	Day	11% 14% 4 12% 7% 6% 5% 3 7% 7% 24%	1691
	11th to 20th	Day	8% 12% 5% 12% 8% 5% 5% 4 6% 6% 29%	1804
	21st to end	Day	13% 13% 5% 11% 7% 5% 4 3 4 7% 29%	1570
March	1st to 10th	Day	19% 13% 4 11% 7% 5% 5% 3 5% 4 23%	3116
	11th to 20th	Day	10% 16% 5% 10% 6% 6% 5% 5% 5% 6% 26%	3271
	21st to end	Day	13% 10% 3 8% 6% 4 5% 3 4 6% 37%	4166
April	1st to 10th	Day	17% 12% 3 8% 6% 4 4 3 5% 5% 32%	2280
	11th to 20th	Day	17% 9% 3 9% 5% 4 4 3 5% 6% 36%	2254
	21st to end	Day	19% 9% 3 8% 5% 5% 5% 4 4 6% 33%	2422
May	1st to 10th	Day	18% 9% 3 9% 5% 5% 5% 4 5% 7% 29%	4253
	11th to 20th	Day	14% 9% 3 8% 6% 5% 4 4 7% 9% 31%	4398
	21st to end	Day	12% 5% 2 6% 6% 6% 5% 5% 7% 9% 38%	4837
June	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 9% 29%	2660
	11th to 20th	Day	13% 6% 2 7% 5% 6% 5% 4 7% 8% 37%	2660
	21st to end	Day	16% 8% 3 8% 5% 5% 6% 4 7% 8% 29%	2660
July	1st to 10th	Day	10% 6% 2 6% 6% 6% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 9% 11% 36%	4440
	21st to end	Day	10% 5% 3 7% 5% 5% 6% 5% 6% 8% 39%	4814
August	1st to 10th	Day	10% 6% 2 7% 6% 5% 7% 5% 8% 8% 37%	2646
	11th to 20th	Day	9% 5% 2 8% 4 6% 6% 5% 8% 10% 37%	2272
	21st to end	Day	10% 6% 2 7% 5% 5% 6% 4 6% 8% 40%	2376
September	1st to 10th	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 46%	2160
	11th to 20th	Day	11% 7% 1 5% 4 4 3 4 5% 7% 49%	2067
	21st to end	Day	12% 6% 2 7% 5% 5% 4 4 7% 8% 40%	1980
October	1st to 10th	Day	18% 10% 3 7% 5% 4 4 4 6% 6% 32%	1889
	11th to 20th	Day	14% 8% 3 8% 6% 5% 5% 5% 6% 7% 33%	1765
	21st to end	Day	20% 10% 3 10% 5% 5% 4 4 5% 5% 29%	1782
November	1st to 10th	Day	12% 12% 3 8% 5% 6% 5% 4 5% 7% 34%	1671
	11th to 20th	Day	15% 9% 4 9% 5% 6% 5% 4 6% 6% 31%	1706
	21st to end	Day	14% 13% 4 8% 6% 5% 6% 4 6% 6% 30%	1520
December	1st to 10th	Day	16% 20% 5% 12% 5% 6% 5% 3 4 5% 20%	1520
	11th to 20th	Day	19% 14% 4 7% 5% 4 5% 4 6% 7% 23%	1906
	21st to end	Day	22% 14% 4 11% 6% 5% 5% 3 5% 6% 20%	2772
January	1st to 10th	Night	14% 15% 6% 13% 6% 5% 5% 3 4 6% 23%	4429
	11th to 20th	Night	10% 15% 7% 18% 7% 6% 4 4 5% 4 19%	4440
	21st to end	Night	17% 15% 5% 11% 6% 5% 4 3 4 6% 23%	4884
February	1st to 10th	Night	10% 12% 5% 14% 7% 6% 6% 4 6% 6% 24%	2485
	11th to 20th	Night	8% 12% 5% 13% 8% 6% 5% 4 5% 6% 29%	2261
	21st to end	Night	13% 11% 5% 10% 6% 6% 4 4 5% 6% 31%	1884
March	1st to 10th	Night	20% 12% 4 9% 6% 4 4 3 4 5% 29%	3724
	11th to 20th	Night	13% 15% 4 10% 6% 5% 5% 3 5% 5% 30%	3685
	21st to end	Night	12% 11% 3 10% 5% 5% 4 3 4 5% 37%	3466
April	1st to 10th	Night	15% 10% 3 8% 6% 6% 4 3 6% 6% 31%	1900
	11th to 20th	Night	19% 9% 2 9% 6% 5% 4 4 4 6% 33%	1875
	21st to end	Night	19% 8% 3 8% 4 4 5% 3 4 6% 36%	1758
May	1st to 10th	Night	19% 10% 3 9% 6% 5% 5% 4 6% 8% 26%	2716
	11th to 20th	Night	17% 10% 4 10% 5% 4 4 3 4 6% 34%	2495
	21st to end	Night	11% 6% 2 7% 4 5% 6% 4 7% 9% 39%	2738
June	1st to 10th	Night	18% 7% 3 7% 6% 4 5% 4 5% 7% 34%	1520
	11th to 20th	Night	15% 6% 2 5% 4 5% 4 4 5% 9% 39%	1520
	21st to end	Night	15% 7% 2 7% 5% 5% 5% 4 6% 8% 36%	1520
July	1st to 10th	Night	10% 5% 3 7% 5% 6% 5% 4 8% 8% 38%	2520
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 7% 9% 43%	2520
	21st to end	Night	8% 6% 3 7% 5% 5% 5% 4 7% 8% 42%	2739
August	1st to 10th	Night	10% 4 2 5% 5% 5% 6% 3 6% 9% 45%	1512
	11th to 20th	Night	8% 5% 2 8% 5% 6% 5% 4 5% 9% 43%	1705
	21st to end	Night	9% 6% 3 6% 5% 4 5% 4 6% 8% 44%	1980
September	1st to 10th	Night	10% 5% 2 5% 5% 4 4 4 6% 7% 48%	1800
	11th to 20th	Night	12% 6% 2 6% 4 4 3 3 5% 6% 50%	1891
	21st to end	Night	13% 5% 2 5% 5% 5% 4 3 6% 7% 45%	1980
October	1st to 10th	Night	18% 8% 2 7% 5% 5% 5% 5% 5% 6% 34%	2069
	11th to 20th	Night	16% 8% 3 8% 5% 5% 5% 4 6% 7% 34%	2194
	21st to end	Night	21% 11% 2 9% 5% 4 4 3 5% 6% 29%	2574
November	1st to 10th	Night	15% 10% 4 8% 5% 4 4 4 5% 6% 35%	2407
	11th to 20th	Night	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2471
	21st to end	Night	15% 13% 4 8% 5% 6% 5% 4 6% 7% 28%	2660
December	1st to 10th	Night	16% 16% 4 11% 7% 6% 5% 4 5% 5% 19%	2660
	11th to 20th	Night	18% 13% 5% 10% 6% 5% 5% 4 5% 5% 25%	3288
	21st to end	Night	22% 14% 6% 11% 6% 5% 4 3 4 5% 20%	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	57% 9% 14% 16% 3 1	2518
	11th to 20th	Day	66% 8% 10% 11% 5% 1	2520
	21st to end	Day	62% 8% 15% 10% 5% 1	2772
February	1st to 10th	Day	60% 8% 9% 16% 5% 2	1691
	11th to 20th	Day	55% 8% 11% 16% 8% 1	1813
	21st to end	Day	56% 6% 12% 14% 10% 2	1570
March	1st to 10th	Day	61% 7% 12% 12% 7% 1	3119
	11th to 20th	Day	57% 7% 13% 12% 8% 2	3271
	21st to end	Day	47% 7% 8% 18% 17% 2	4166
April	1st to 10th	Day	52% 7% 9% 19% 10% 3	2280
	11th to 20th	Day	49% 7% 10% 18% 15% 2	2254
	21st to end	Day	53% 6% 11% 17% 11% 3	2422
May	1st to 10th	Day	53% 8% 11% 18% 9% 1	4267
	11th to 20th	Day	48% 10% 15% 17% 9% 2	4402
	21st to end	Day	39% 10% 14% 25% 10% 1	4837
June	1st to 10th	Day	51% 8% 13% 18% 10% 1	2660
	11th to 20th	Day	43% 8% 12% 21% 13% 2	2660
	21st to end	Day	50% 8% 13% 19% 9% 1	2660
July	1st to 10th	Day	39% 9% 15% 24% 12%	4370
	11th to 20th	Day	38% 11% 15% 29% 7%	4365
	21st to end	Day	41% 9% 13% 28% 9%	4661
August	1st to 10th	Day	40% 11% 17% 22% 10%	2632
	11th to 20th	Day	37% 11% 18% 24% 9%	2272
	21st to end	Day	40% 9% 13% 26% 12% 1	2376
September	1st to 10th	Day	35% 9% 13% 29% 13% 1	2160
	11th to 20th	Day	34% 6% 13% 31% 15% 1	2067
	21st to end	Day	39% 9% 16% 23% 10% 2	1980
October	1st to 10th	Day	50% 7% 12% 19% 11%	1889
	11th to 20th	Day	47% 10% 15% 21% 7%	1765
	21st to end	Day	56% 7% 13% 15% 7% 1	1782
November	1st to 10th	Day	50% 7% 15% 18% 10% 1	1671
	11th to 20th	Day	52% 7% 13% 15% 10% 2	1706
	21st to end	Day	53% 8% 15% 18% 5% 1	1520
December	1st to 10th	Day	67% 7% 11% 11% 4	1520
	11th to 20th	Day	58% 8% 14% 15% 5%	1906
	21st to end	Day	63% 7% 12% 14% 3	2772
January	1st to 10th	Night	61% 7% 16% 12% 4	4429
	11th to 20th	Night	65% 7% 13% 11% 4	4440
	21st to end	Night	63% 6% 12% 12% 6% 1	4884
February	1st to 10th	Night	58% 6% 14% 12% 8% 1	2485
	11th to 20th	Night	54% 7% 11% 17% 10% 1	2263
	21st to end	Night	54% 6% 13% 17% 9% 2	1884
March	1st to 10th	Night	57% 6% 10% 15% 9% 1	3734
	11th to 20th	Night	55% 6% 12% 17% 9% 1	3686
	21st to end	Night	48% 6% 10% 19% 14% 3	3466
April	1st to 10th	Night	52% 6% 10% 18% 12% 1	1900
	11th to 20th	Night	52% 6% 10% 18% 12% 1	1875
	21st to end	Night	49% 6% 11% 18% 12% 3	1758
May	1st to 10th	Night	55% 7% 10% 16% 10% 2	2722
	11th to 20th	Night	50% 7% 12% 20% 10% 1	2496
	21st to end	Night	38% 10% 13% 21% 16% 2	2739
June	1st to 10th	Night	47% 9% 13% 19% 11% 2	1520
	11th to 20th	Night	42% 7% 14% 22% 13% 2	1520
	21st to end	Night	44% 9% 15% 21% 10% 1	1520
July	1st to 10th	Night	41% 8% 15% 23% 13% 1	2480
	11th to 20th	Night	35% 9% 15% 29% 12%	2472
	21st to end	Night	38% 9% 16% 26% 11% 1	2651
August	1st to 10th	Night	35% 8% 19% 27% 11%	1502
	11th to 20th	Night	36% 9% 15% 27% 13%	1705
	21st to end	Night	36% 8% 16% 26% 12%	1980
September	1st to 10th	Night	34% 8% 17% 28% 12% 1	1800
	11th to 20th	Night	34% 7% 15% 30% 14%	1891
	21st to end	Night	39% 7% 14% 26% 13% 2	1980
October	1st to 10th	Night	47% 8% 13% 21% 11% 1	2069
	11th to 20th	Night	47% 8% 15% 23% 7%	2194
	21st to end	Night	55% 7% 14% 15% 8% 1	2574
November	1st to 10th	Night	48% 8% 14% 19% 10% 2	2407
	11th to 20th	Night	50% 7% 13% 19% 8% 3	2471
	21st to end	Night	55% 8% 15% 17% 5%	2660
December	1st to 10th	Night	65% 8% 13% 12% 2	2660
	11th to 20th	Night	60% 7% 11% 14% 7% 1	3288
	21st to end	Night	66% 6% 12% 14% 3	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	20% 26% 29% 18% 7% 1	180
	11th to 20th	Day	26% 29% 32% 12% 1 1	180
	21st to end	Day	22% 26% 35% 13% 3 1	198
February	1st to 10th	Day	31% 36% 27% 5% 1	261
	11th to 20th	Day	25% 33% 32% 10% 1	412
	21st to end	Day	29% 25% 33% 12% 2	382
March	1st to 10th	Day	29% 22% 30% 17% 3	460
	11th to 20th	Day	26% 29% 26% 15% 3 1	460
	21st to end	Day	27% 28% 25% 12% 5% 1	506
April	1st to 10th	Day	31% 22% 27% 16% 4 1	460
	11th to 20th	Day	30% 27% 23% 13% 4 2	452
	21st to end	Day	29% 28% 23% 12% 5% 2	460
May	1st to 10th	Day	26% 23% 32% 11% 7% 1	463
	11th to 20th	Day	21% 19% 33% 20% 5% 2	487
	21st to end	Day	16% 20% 32% 23% 8% 1	529
June	1st to 10th	Day	25% 16% 34% 18% 6% 1	490
	11th to 20th	Day	16% 18% 33% 23% 9% 1	490
	21st to end	Day	21% 19% 31% 19% 8% 1	490
July	1st to 10th	Day	15% 12% 30% 29% 12% 1	485
	11th to 20th	Day	11% 10% 38% 28% 12% 1	484
	21st to end	Day	13% 10% 36% 29% 11% 2	532
August	1st to 10th	Day	11% 9% 34% 28% 15% 3	486
	11th to 20th	Day	12% 9% 32% 28% 14% 5%	456
	21st to end	Day	12% 16% 27% 28% 11% 5%	495
September	1st to 10th	Day	15% 12% 29% 24% 13% 7%	450
	11th to 20th	Day	16% 13% 25% 21% 15% 8%	450
	21st to end	Day	14% 14% 33% 23% 12% 5%	450
October	1st to 10th	Day	22% 19% 24% 18% 14% 2	450
	11th to 20th	Day	21% 22% 30% 19% 7% 1	432
	21st to end	Day	28% 21% 27% 20% 4	396
November	1st to 10th	Day	25% 19% 28% 20% 7% 1	365
	11th to 20th	Day	30% 21% 29% 14% 5% 2	366
	21st to end	Day	28% 26% 28% 15% 2	180
December	1st to 10th	Day	26% 28% 28% 13% 4 1	180
	11th to 20th	Day	27% 29% 34% 9% 1	180
	21st to end	Day	30% 24% 31% 12% 3	198
January	1st to 10th	Night	21% 21% 36% 18% 4	760
	11th to 20th	Night	25% 22% 31% 18% 4	760
	21st to end	Night	14% 20% 39% 22% 5%	836
February	1st to 10th	Night	17% 21% 38% 21% 3	760
	11th to 20th	Night	19% 24% 36% 19% 2	743
	21st to end	Night	21% 22% 33% 20% 4	628
March	1st to 10th	Night	25% 19% 30% 23% 2	760
	11th to 20th	Night	25% 23% 28% 19% 4 1	760
	21st to end	Night	24% 22% 28% 20% 6% 1	836
April	1st to 10th	Night	22% 23% 28% 23% 4	760
	11th to 20th	Night	25% 22% 27% 18% 7%	751
	21st to end	Night	23% 19% 29% 22% 6%	618
May	1st to 10th	Night	25% 15% 29% 24% 6%	504
	11th to 20th	Night	15% 17% 34% 26% 6% 1	374
	21st to end	Night	13% 15% 31% 29% 11% 1	411
June	1st to 10th	Night	22% 9% 28% 29% 11% 1	380
	11th to 20th	Night	18% 8% 26% 37% 11% 1	380
	21st to end	Night	16% 7% 32% 33% 11% 1	380
July	1st to 10th	Night	14% 6% 26% 38% 15% 1	370
	11th to 20th	Night	12% 3 24% 42% 16% 2	368
	21st to end	Night	12% 5% 23% 45% 15%	416
August	1st to 10th	Night	12% 4 22% 43% 18% 1	378
	11th to 20th	Night	11% 5% 21% 38% 22% 2	611
	21st to end	Night	12% 8% 22% 36% 20% 2	792
September	1st to 10th	Night	13% 7% 27% 35% 16% 3	720
	11th to 20th	Night	16% 9% 24% 29% 19% 3	720
	21st to end	Night	15% 10% 31% 27% 16% 2	720
October	1st to 10th	Night	23% 14% 23% 25% 14% 1	720
	11th to 20th	Night	21% 15% 26% 28% 9% 1	720
	21st to end	Night	28% 15% 29% 24% 5%	792
November	1st to 10th	Night	23% 16% 32% 21% 8% 1	740
	11th to 20th	Night	21% 20% 32% 18% 8% 1	760
	21st to end	Night	24% 22% 28% 20% 6% 1	760
December	1st to 10th	Night	26% 23% 29% 18% 4	760
	11th to 20th	Night	24% 20% 32% 20% 4	760
	21st to end	Night	28% 20% 32% 17% 2	836

Page generated at 2024-08-12 09:52:51. Version ac07

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