Taylor Oaks Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Taylor Oaks Observatory clear sky chart from 2005-11-06 to 2026-04-17.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	131843
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 44%	130330
Transparency	Day	38% 6% 11% 20% 19% 6%	135502
	Night	38% 6% 10% 18% 21% 7%	134741
Seeing	Day	17% 10% 25% 24% 17% 7%	17200
	Night	16% 9% 24% 30% 18% 2	27348

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	15% 6% 2 5% 3 3 3 2 4 5% 51%	5258
	11th to 20th	Day	11% 6% 2 4 3 3 2 2 3 3 61%	5280
	21st to end	Day	19% 9% 3 6% 4 4 4 3 4 4 40%	5780
February	1st to 10th	Day	14% 7% 1 6% 4 3 4 3 6% 8% 42%	1890
	11th to 20th	Day	21% 6% 2 4 3 3 3 3 4 5% 45%	2034
	21st to end	Day	19% 8% 3 6% 4 3 4 3 5% 5% 41%	1784
March	1st to 10th	Day	20% 7% 2 6% 4 3 4 3 5% 5% 41%	5045
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 4 6% 54%	5090
	21st to end	Day	17% 6% 3 6% 4 3 3 3 4 5% 47%	5586
April	1st to 10th	Day	11% 5% 2 4 3 3 4 5% 7% 8% 49%	2310
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 3 4 7% 49%	2430
	21st to end	Day	11% 5% 2 5% 4 4 4 4 5% 7% 49%	2546
May	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 8% 11% 35%	5862
	11th to 20th	Day	19% 7% 3 7% 5% 5% 5% 4 7% 8% 31%	5861
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	6433
June	1st to 10th	Day	9% 5% 2 6% 6% 6% 6% 5% 7% 11% 38%	2600
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 11% 42%	2600
	21st to end	Day	6% 4 2 6% 6% 6% 6% 5% 8% 11% 41%	2600
July	1st to 10th	Day	9% 6% 2 8% 6% 6% 6% 5% 8% 10% 34%	5900
	11th to 20th	Day	6% 5% 2 7% 6% 6% 7% 6% 9% 14% 32%	5900
	21st to end	Day	9% 7% 3 7% 6% 6% 7% 6% 9% 12% 29%	6424
August	1st to 10th	Day	22% 7% 3 7% 5% 5% 6% 5% 7% 9% 24%	4234
	11th to 20th	Day	11% 6% 2 6% 5% 6% 6% 5% 8% 11% 35%	4174
	21st to end	Day	6% 4 2 5% 4 5% 4 4 7% 10% 51%	4378
September	1st to 10th	Day	7% 5% 2 5% 5% 5% 5% 5% 7% 10% 43%	2214
	11th to 20th	Day	12% 7% 3 7% 4 4 6% 5% 6% 9% 40%	2200
	21st to end	Day	17% 6% 2 7% 4 4 4 3 5% 7% 39%	2200
October	1st to 10th	Day	13% 4 2 5% 3 4 4 3 4 6% 53%	2082
	11th to 20th	Day	14% 5% 2 4 3 2 3 2 3 4 59%	2000
	21st to end	Day	13% 4 2 4 3 3 2 2 4 6% 57%	2200
November	1st to 10th	Day	14% 5% 2 4 4 3 3 2 4 5% 54%	2057
	11th to 20th	Day	13% 6% 2 3 2 3 3 2 5% 6% 55%	1953
	21st to end	Day	14% 5% 1 4 3 3 4 3 4 6% 51%	1890
December	1st to 10th	Day	15% 7% 2 5% 3 3 3 2 4 5% 51%	3020
	11th to 20th	Day	17% 7% 3 7% 4 3 3 3 5% 6% 42%	3463
	21st to end	Day	21% 6% 2 4 3 3 3 3 4 6% 45%	4565
January	1st to 10th	Night	13% 7% 2 6% 3 3 3 2 3 4 55%	7635
	11th to 20th	Night	12% 6% 2 4 3 3 3 3 4 5% 56%	7680
	21st to end	Night	19% 9% 3 5% 3 3 3 2 4 5% 44%	8401
February	1st to 10th	Night	14% 7% 2 6% 4 4 3 3 5% 5% 47%	2730
	11th to 20th	Night	20% 6% 2 5% 4 4 3 3 5% 4 43%	2468
	21st to end	Night	16% 7% 2 5% 4 3 4 4 5% 6% 44%	2020
March	1st to 10th	Night	19% 7% 2 6% 4 3 3 3 4 6% 42%	5028
	11th to 20th	Night	10% 4 2 4 3 4 3 3 5% 8% 54%	5090
	21st to end	Night	15% 5% 2 6% 4 3 4 4 5% 6% 48%	5588
April	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 5% 6% 49%	2310
	11th to 20th	Night	11% 5% 2 5% 3 3 4 2 5% 7% 53%	2049
	21st to end	Night	11% 5% 1 5% 4 4 4 4 5% 8% 50%	1870
May	1st to 10th	Night	12% 6% 3 6% 5% 5% 4 3 5% 9% 41%	4033
	11th to 20th	Night	19% 7% 2 6% 4 4 5% 4 7% 9% 33%	4032
	21st to end	Night	13% 5% 2 6% 4 4 5% 4 6% 10% 39%	4421
June	1st to 10th	Night	10% 7% 2 6% 5% 7% 7% 5% 7% 10% 35%	1800
	11th to 20th	Night	10% 6% 2 6% 5% 5% 6% 6% 7% 10% 37%	1800
	21st to end	Night	7% 6% 2 6% 7% 5% 7% 5% 8% 12% 36%	1800
July	1st to 10th	Night	12% 8% 3 9% 6% 6% 7% 5% 8% 10% 28%	4058
	11th to 20th	Night	8% 6% 3 8% 6% 6% 8% 7% 11% 13% 25%	4057
	21st to end	Night	12% 9% 3 9% 7% 7% 7% 5% 8% 10% 23%	4427
August	1st to 10th	Night	23% 8% 3 7% 5% 5% 5% 4 6% 10% 23%	2915
	11th to 20th	Night	11% 8% 3 7% 5% 5% 5% 5% 8% 10% 33%	2875
	21st to end	Night	6% 4 2 5% 4 5% 5% 4 6% 9% 48%	3486
September	1st to 10th	Night	9% 5% 1 6% 5% 4 5% 5% 8% 9% 43%	2181
	11th to 20th	Night	13% 6% 2 7% 5% 4 5% 4 6% 8% 40%	2200
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 5% 7% 39%	2200
October	1st to 10th	Night	13% 5% 2 4 3 4 3 3 5% 6% 52%	2316
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 6% 54%	2400
	21st to end	Night	13% 5% 1 4 3 3 3 2 3 5% 57%	2640
November	1st to 10th	Night	14% 6% 2 4 3 3 2 3 3 6% 53%	2461
	11th to 20th	Night	12% 6% 2 5% 4 4 3 3 4 5% 53%	2664
	21st to end	Night	13% 4 2 5% 3 4 4 3 6% 6% 50%	2730
December	1st to 10th	Night	15% 6% 2 5% 3 3 3 2 4 5% 52%	4380
	11th to 20th	Night	18% 7% 3 6% 4 3 3 3 4 6% 44%	4952
	21st to end	Night	20% 5% 1 5% 3 4 3 3 4 5% 46%	6633

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	36% 3 9% 21% 26% 6%	5259
	11th to 20th	Day	31% 2 4 12% 38% 13%	5280
	21st to end	Day	48% 2 4 15% 20% 11%	5780
February	1st to 10th	Day	40% 4 10% 22% 19% 5%	1890
	11th to 20th	Day	43% 4 6% 19% 23% 5%	2044
	21st to end	Day	45% 4 8% 14% 22% 7%	1784
March	1st to 10th	Day	46% 4 6% 14% 19% 11%	5045
	11th to 20th	Day	31% 4 7% 14% 26% 18%	5090
	21st to end	Day	41% 4 6% 20% 23% 6%	5586
April	1st to 10th	Day	32% 5% 10% 21% 26% 6%	2310
	11th to 20th	Day	34% 5% 8% 21% 22% 9%	2430
	21st to end	Day	34% 6% 12% 22% 22% 4	2546
May	1st to 10th	Day	40% 9% 16% 22% 11% 1	5897
	11th to 20th	Day	49% 8% 13% 18% 12% 1	5865
	21st to end	Day	37% 7% 13% 22% 19% 3	6447
June	1st to 10th	Day	38% 9% 14% 25% 11% 2	2600
	11th to 20th	Day	34% 10% 18% 22% 14% 2	2600
	21st to end	Day	34% 11% 16% 22% 15% 2	2600
July	1st to 10th	Day	41% 11% 16% 22% 9% 1	5835
	11th to 20th	Day	38% 13% 29% 16% 3	5831
	21st to end	Day	44% 12% 16% 21% 6% 1	6240
August	1st to 10th	Day	54% 8% 17% 16% 5%	4221
	11th to 20th	Day	40% 11% 17% 20% 12% 1	4213
	21st to end	Day	27% 8% 15% 31% 16% 2	4378
September	1st to 10th	Day	34% 9% 14% 19% 19% 4	2214
	11th to 20th	Day	40% 8% 10% 18% 21% 3	2200
	21st to end	Day	45% 5% 10% 19% 15% 6%	2200
October	1st to 10th	Day	31% 4 7% 19% 29% 10%	3394
	11th to 20th	Day	20% 2 5% 18% 29% 26%	3240
	21st to end	Day	26% 3 5% 24% 27% 15%	3538
November	1st to 10th	Day	34% 3 7% 18% 29% 9%	2057
	11th to 20th	Day	30% 4 7% 23% 27% 8%	1953
	21st to end	Day	35% 5% 8% 22% 23% 8%	1890
December	1st to 10th	Day	38% 3 5% 18% 27% 9%	3020
	11th to 20th	Day	44% 4 7% 18% 21% 7%	3460
	21st to end	Day	41% 3 8% 24% 21% 3	4565
January	1st to 10th	Night	35% 2 9% 21% 28% 6%	7636
	11th to 20th	Night	33% 3 5% 15% 34% 11%	7680
	21st to end	Night	45% 2 4 16% 24% 9%	8401
February	1st to 10th	Night	40% 4 8% 21% 21% 7%	2730
	11th to 20th	Night	45% 3 5% 17% 23% 7%	2469
	21st to end	Night	39% 5% 8% 17% 22% 9%	2020
March	1st to 10th	Night	44% 4 8% 12% 26% 7%	5028
	11th to 20th	Night	30% 4 7% 13% 29% 18%	5090
	21st to end	Night	38% 4 7% 21% 21% 9%	5588
April	1st to 10th	Night	35% 5% 10% 19% 24% 7%	2310
	11th to 20th	Night	31% 4 9% 24% 23% 10%	2049
	21st to end	Night	33% 5% 11% 26% 21% 4	1870
May	1st to 10th	Night	39% 7% 15% 22% 15% 2	4060
	11th to 20th	Night	46% 8% 15% 18% 11% 1	4033
	21st to end	Night	37% 8% 13% 24% 16% 2	4429
June	1st to 10th	Night	42% 9% 15% 20% 12% 2	1800
	11th to 20th	Night	39% 11% 16% 20% 12% 2	1800
	21st to end	Night	37% 12% 17% 18% 13% 3	1800
July	1st to 10th	Night	48% 11% 18% 16% 7% 1	4015
	11th to 20th	Night	44% 17% 25% 11% 3 1	4006
	21st to end	Night	53% 11% 15% 16% 5%	4297
August	1st to 10th	Night	55% 8% 18% 15% 4	2904
	11th to 20th	Night	42% 10% 23% 18% 8% 1	2902
	21st to end	Night	30% 9% 12% 26% 20% 3	3486
September	1st to 10th	Night	35% 8% 15% 19% 17% 5%	2181
	11th to 20th	Night	41% 8% 12% 16% 21% 2	2200
	21st to end	Night	43% 6% 12% 17% 16% 6%	2200
October	1st to 10th	Night	33% 6% 9% 20% 26% 7%	3784
	11th to 20th	Night	23% 3 5% 18% 28% 24%	3899
	21st to end	Night	28% 3 5% 20% 26% 17%	4252
November	1st to 10th	Night	34% 4 7% 17% 27% 12%	2461
	11th to 20th	Night	33% 5% 6% 17% 27% 12%	2664
	21st to end	Night	34% 4 6% 22% 27% 8%	2730
December	1st to 10th	Night	35% 4 6% 18% 29% 8%	4380
	11th to 20th	Night	42% 4 10% 15% 18% 9%	4954
	21st to end	Night	41% 3 9% 24% 21% 3	6633

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	22% 22% 39% 15% 2	330
	11th to 20th	Day	26% 24% 31% 15% 4	330
	21st to end	Day	22% 23% 39% 12% 3	363
February	1st to 10th	Day	19% 19% 41% 15% 5%	330
	11th to 20th	Day	36% 18% 37% 8% 1	330
	21st to end	Day	29% 20% 35% 13% 2	327
March	1st to 10th	Day	24% 16% 33% 20% 6% 1	540
	11th to 20th	Day	21% 17% 38% 19% 5% 1	540
	21st to end	Day	21% 18% 36% 19% 5% 1	594
April	1st to 10th	Day	19% 16% 34% 21% 9% 1	540
	11th to 20th	Day	16% 14% 33% 24% 11% 3	516
	21st to end	Day	16% 10% 28% 28% 13% 5%	500
May	1st to 10th	Day	12% 15% 34% 21% 14% 4	503
	11th to 20th	Day	19% 6% 22% 27% 20% 7%	527
	21st to end	Day	16% 6% 21% 25% 21% 11%	573
June	1st to 10th	Day	10% 4 20% 34% 24% 8%	530
	11th to 20th	Day	8% 4 20% 28% 28% 11%	530
	21st to end	Day	8% 2 15% 34% 29% 11%	530
July	1st to 10th	Day	9% 2 10% 29% 30% 20%	525
	11th to 20th	Day	8% 2 8% 31% 35% 16%	524
	21st to end	Day	7% 2 11% 32% 35% 13%	576
August	1st to 10th	Day	18% 3 15% 28% 23% 13%	526
	11th to 20th	Day	14% 3 10% 27% 29% 16%	519
	21st to end	Day	11% 2 13% 31% 28% 15%	583
September	1st to 10th	Day	9% 4 14% 31% 30% 13%	530
	11th to 20th	Day	15% 3 15% 27% 26% 13%	530
	21st to end	Day	19% 6% 19% 28% 24% 5%	530
October	1st to 10th	Day	15% 5% 23% 27% 22% 7%	530
	11th to 20th	Day	12% 10% 25% 27% 22% 5%	530
	21st to end	Day	16% 10% 24% 26% 18% 5%	583
November	1st to 10th	Day	19% 9% 27% 27% 16% 3	535
	11th to 20th	Day	18% 13% 36% 24% 6% 2	393
	21st to end	Day	15% 14% 35% 25% 10% 2	330
December	1st to 10th	Day	27% 14% 39% 15% 4	330
	11th to 20th	Day	22% 12% 37% 21% 8% 1	330
	21st to end	Day	26% 16% 34% 16% 6% 2	363
January	1st to 10th	Night	21% 18% 31% 25% 5%	840
	11th to 20th	Night	20% 15% 32% 28% 5%	840
	21st to end	Night	20% 15% 35% 27% 3	924
February	1st to 10th	Night	18% 13% 36% 29% 4	840
	11th to 20th	Night	26% 17% 36% 20% 1	823
	21st to end	Night	20% 16% 36% 24% 4	692
March	1st to 10th	Night	19% 13% 34% 29% 6%	840
	11th to 20th	Night	18% 15% 35% 25% 7% 1	840
	21st to end	Night	19% 14% 34% 27% 6%	924
April	1st to 10th	Night	16% 15% 33% 27% 9%	840
	11th to 20th	Night	13% 14% 28% 31% 12% 1	816
	21st to end	Night	13% 7% 30% 35% 15%	670
May	1st to 10th	Night	11% 8% 31% 36% 14%	600
	11th to 20th	Night	14% 7% 23% 36% 19% 1	591
	21st to end	Night	14% 4 15% 34% 31% 2	650
June	1st to 10th	Night	11% 3 18% 38% 26% 4	600
	11th to 20th	Night	13% 4 15% 31% 30% 8%	600
	21st to end	Night	9% 2 13% 37% 34% 5%	600
July	1st to 10th	Night	11% 2 11% 31% 37% 8%	585
	11th to 20th	Night	9% 2 7% 33% 41% 8%	582
	21st to end	Night	7% 2 12% 30% 42% 6%	657
August	1st to 10th	Night	17% 2 9% 29% 35% 8%	597
	11th to 20th	Night	13% 3 9% 30% 39% 7%	594
	21st to end	Night	11% 2 10% 29% 42% 5%	819
September	1st to 10th	Night	10% 3 12% 31% 38% 6%	800
	11th to 20th	Night	15% 4 11% 30% 36% 5%	800
	21st to end	Night	19% 5% 16% 33% 25% 3	800
October	1st to 10th	Night	15% 5% 18% 31% 26% 5%	800
	11th to 20th	Night	17% 7% 24% 30% 21% 2	800
	21st to end	Night	16% 10% 21% 32% 19% 3	880
November	1st to 10th	Night	16% 8% 25% 32% 16% 3	820
	11th to 20th	Night	14% 11% 30% 33% 10% 1	840
	21st to end	Night	14% 11% 28% 33% 12% 1	840
December	1st to 10th	Night	22% 12% 26% 34% 6% 1	840
	11th to 20th	Night	20% 10% 26% 33% 11%	840
	21st to end	Night	23% 13% 25% 30% 8%	924

Page generated at 2026-04-14 02:44:27. Version ac07

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