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 2024-12-24.

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 5% 4 6% 8% 42%	101650
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	98420
Transparency	Day	38% 7% 11% 20% 19% 5%	105353
	Night	39% 6% 10% 18% 20% 7%	102856
Seeing	Day	16% 9% 25% 25% 18% 7%	15452
	Night	16% 9% 23% 30% 19% 2	25556

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	17% 5% 2 5% 3 3 3 2 4 6% 50%	2836
	11th to 20th	Day	13% 7% 2 5% 3 3 3 2 4 5% 52%	2840
	21st to end	Day	22% 8% 2 5% 3 3 3 3 4 4 42%	3124
February	1st to 10th	Day	15% 8% 2 5% 5% 3 4 4 6% 8% 41%	1710
	11th to 20th	Day	20% 6% 2 4 3 3 4 3 4 5% 46%	1834
	21st to end	Day	19% 8% 3 6% 4 4 4 3 5% 5% 40%	1618
March	1st to 10th	Day	24% 7% 2 5% 3 3 3 3 4 6% 39%	3435
	11th to 20th	Day	11% 4 2 5% 4 4 4 3 5% 6% 53%	3480
	21st to end	Day	20% 7% 2 6% 3 3 4 3 4 5% 43%	3815
April	1st to 10th	Day	11% 5% 2 4 3 3 4 5% 6% 7% 50%	2090
	11th to 20th	Day	13% 5% 2 5% 4 4 5% 3 4 7% 47%	2240
	21st to end	Day	12% 5% 2 5% 4 4 4 4 5% 7% 50%	2418
May	1st to 10th	Day	10% 7% 3 7% 5% 5% 6% 5% 7% 10% 36%	4082
	11th to 20th	Day	16% 8% 3 7% 4 4 4 4 6% 7% 37%	4081
	21st to end	Day	7% 4 2 5% 4 4 5% 4 7% 10% 48%	4476
June	1st to 10th	Day	9% 5% 2 6% 6% 6% 6% 5% 7% 11% 38%	2470
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	2470
	21st to end	Day	6% 4 2 6% 6% 7% 6% 5% 8% 11% 40%	2470
July	1st to 10th	Day	8% 6% 2 8% 6% 6% 6% 5% 9% 11% 33%	4120
	11th to 20th	Day	7% 5% 2 8% 6% 6% 6% 5% 9% 13% 33%	4120
	21st to end	Day	11% 9% 3 9% 6% 6% 7% 6% 9% 12% 23%	4466
August	1st to 10th	Day	21% 7% 3 7% 5% 6% 6% 5% 7% 10% 24%	4104
	11th to 20th	Day	11% 5% 2 6% 5% 6% 6% 5% 8% 11% 35%	4044
	21st to end	Day	6% 4 2 5% 4 5% 4 4 7% 10% 51%	4244
September	1st to 10th	Day	8% 5% 2 5% 5% 6% 5% 5% 7% 10% 42%	2104
	11th to 20th	Day	12% 7% 3 7% 4 4 6% 4 6% 8% 39%	2090
	21st to end	Day	17% 6% 2 7% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Day	14% 4 2 5% 3 3 4 3 4 5% 53%	1978
	11th to 20th	Day	13% 5% 2 4 3 2 3 2 3 4 58%	1900
	21st to end	Day	13% 4 2 4 3 3 2 2 4 6% 57%	2090
November	1st to 10th	Day	14% 6% 2 4 4 3 3 2 4 5% 54%	1957
	11th to 20th	Day	14% 6% 2 3 3 3 3 2 5% 6% 53%	1860
	21st to end	Day	15% 5% 1 5% 3 3 4 4 4 6% 51%	1800
December	1st to 10th	Day	18% 8% 2 5% 3 4 4 3 5% 6% 41%	1800
	11th to 20th	Day	17% 5% 2 5% 3 2 2 2 5% 6% 50%	2243
	21st to end	Day	18% 7% 2 5% 4 3 4 4 5% 6% 43%	3151
January	1st to 10th	Night	17% 6% 2 6% 3 3 3 2 4 5% 48%	4109
	11th to 20th	Night	12% 7% 2 5% 4 3 4 4 5% 6% 48%	4120
	21st to end	Night	22% 9% 2 4 3 3 3 2 4 4 45%	4532
February	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 4 5% 46%	2470
	11th to 20th	Night	21% 6% 2 5% 4 4 3 3 4 4 43%	2228
	21st to end	Night	16% 6% 2 6% 4 4 4 4 5% 7% 43%	1834
March	1st to 10th	Night	23% 10% 3 7% 4 3 3 3 4 6% 34%	3418
	11th to 20th	Night	11% 5% 2 5% 4 4 3 3 5% 8% 51%	3480
	21st to end	Night	19% 5% 2 5% 4 3 4 4 5% 5% 43%	3817
April	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 5% 6% 49%	2090
	11th to 20th	Night	12% 5% 2 5% 3 3 4 2 5% 7% 51%	1887
	21st to end	Night	11% 5% 1 5% 4 3 4 3 5% 8% 50%	1777
May	1st to 10th	Night	13% 6% 3 5% 5% 5% 4 3 5% 8% 42%	2813
	11th to 20th	Night	16% 8% 2 7% 4 4 4 3 6% 7% 38%	2812
	21st to end	Night	7% 4 2 7% 4 5% 6% 5% 7% 12% 41%	3079
June	1st to 10th	Night	9% 7% 2 6% 5% 7% 7% 5% 7% 10% 35%	1710
	11th to 20th	Night	10% 6% 2 6% 5% 6% 6% 5% 7% 10% 37%	1710
	21st to end	Night	7% 6% 2 7% 7% 5% 6% 5% 8% 11% 35%	1710
July	1st to 10th	Night	11% 8% 3 9% 6% 5% 6% 5% 8% 10% 29%	2840
	11th to 20th	Night	9% 6% 2 7% 5% 5% 7% 7% 10% 12% 30%	2840
	21st to end	Night	15% 9% 3 9% 6% 7% 6% 5% 7% 9% 22%	3087
August	1st to 10th	Night	23% 8% 3 6% 5% 5% 5% 4 7% 10% 24%	2825
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 5% 8% 10% 33%	2785
	21st to end	Night	6% 4 2 5% 4 5% 5% 4 7% 9% 49%	3379
September	1st to 10th	Night	9% 5% 1 6% 6% 4 4 5% 8% 9% 43%	2072
	11th to 20th	Night	14% 6% 2 7% 5% 4 5% 4 6% 8% 38%	2090
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 5% 7% 39%	2090
October	1st to 10th	Night	14% 5% 2 4 3 4 3 3 4 5% 53%	2200
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 6% 54%	2280
	21st to end	Night	12% 5% 1 5% 3 3 3 2 3 5% 58%	2508
November	1st to 10th	Night	14% 5% 2 5% 3 3 2 3 4 6% 53%	2341
	11th to 20th	Night	12% 6% 2 5% 4 4 3 3 4 5% 52%	2537
	21st to end	Night	13% 4 2 4 3 4 4 3 6% 6% 50%	2600
December	1st to 10th	Night	18% 7% 2 6% 4 3 4 3 4 4 44%	2600
	11th to 20th	Night	18% 6% 2 5% 3 2 3 2 3 5% 51%	3172
	21st to end	Night	19% 5% 2 5% 3 4 4 3 5% 7% 43%	4578

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% 4 6% 24% 24% 7%	2837
	11th to 20th	Day	36% 3 6% 17% 31% 7%	2840
	21st to end	Day	46% 3 5% 16% 25% 6%	3124
February	1st to 10th	Day	41% 4 10% 21% 19% 5%	1710
	11th to 20th	Day	42% 5% 6% 18% 24% 6%	1844
	21st to end	Day	46% 4 8% 15% 20% 7%	1618
March	1st to 10th	Day	48% 4 7% 16% 15% 10%	3435
	11th to 20th	Day	32% 5% 8% 14% 29% 12%	3480
	21st to end	Day	45% 4 6% 19% 23% 3	3815
April	1st to 10th	Day	32% 5% 10% 21% 27% 6%	2090
	11th to 20th	Day	36% 5% 9% 19% 21% 10%	2240
	21st to end	Day	33% 6% 11% 22% 23% 4	2418
May	1st to 10th	Day	40% 9% 14% 21% 13% 2	4120
	11th to 20th	Day	44% 7% 11% 21% 17% 1	4085
	21st to end	Day	30% 8% 16% 23% 21% 3	4489
June	1st to 10th	Day	38% 10% 14% 26% 11% 2	2470
	11th to 20th	Day	34% 9% 17% 23% 14% 2	2470
	21st to end	Day	35% 12% 15% 22% 15% 2	2470
July	1st to 10th	Day	41% 12% 18% 18% 9% 2	4055
	11th to 20th	Day	40% 12% 25% 18% 4 1	4051
	21st to end	Day	50% 12% 16% 17% 5%	4324
August	1st to 10th	Day	53% 8% 17% 16% 5%	4091
	11th to 20th	Day	40% 11% 17% 20% 12% 1	4083
	21st to end	Day	27% 8% 16% 31% 16% 2	4244
September	1st to 10th	Day	35% 9% 14% 19% 19% 4	2104
	11th to 20th	Day	41% 8% 10% 16% 21% 3	2090
	21st to end	Day	45% 5% 9% 19% 16% 6%	2090
October	1st to 10th	Day	31% 4 6% 19% 29% 10%	3290
	11th to 20th	Day	20% 2 5% 18% 28% 27%	3140
	21st to end	Day	26% 3 5% 24% 26% 16%	3428
November	1st to 10th	Day	34% 3 6% 18% 29% 9%	1957
	11th to 20th	Day	32% 4 7% 22% 27% 8%	1860
	21st to end	Day	35% 5% 8% 21% 23% 8%	1800
December	1st to 10th	Day	44% 4 7% 20% 20% 5%	1800
	11th to 20th	Day	37% 3 7% 21% 24% 10%	2240
	21st to end	Day	42% 4 7% 21% 22% 3	3151
January	1st to 10th	Night	38% 3 8% 18% 26% 7%	4109
	11th to 20th	Night	37% 4 8% 16% 27% 7%	4120
	21st to end	Night	45% 3 4 16% 26% 6%	4532
February	1st to 10th	Night	40% 4 8% 20% 21% 7%	2470
	11th to 20th	Night	45% 3 5% 17% 23% 7%	2229
	21st to end	Night	40% 5% 9% 18% 20% 8%	1834
March	1st to 10th	Night	51% 5% 10% 12% 15% 7%	3418
	11th to 20th	Night	33% 4 8% 15% 26% 15%	3480
	21st to end	Night	42% 5% 7% 18% 20% 7%	3817
April	1st to 10th	Night	35% 5% 9% 19% 25% 7%	2090
	11th to 20th	Night	33% 4 9% 23% 22% 10%	1887
	21st to end	Night	33% 5% 10% 26% 22% 4	1777
May	1st to 10th	Night	39% 7% 13% 23% 15% 2	2840
	11th to 20th	Night	42% 9% 12% 20% 16% 1	2813
	21st to end	Night	31% 9% 15% 27% 17% 1	3087
June	1st to 10th	Night	42% 10% 15% 20% 12% 2	1710
	11th to 20th	Night	39% 11% 15% 21% 13% 2	1710
	21st to end	Night	38% 12% 17% 18% 12% 3	1710
July	1st to 10th	Night	47% 11% 17% 14% 8% 2	2795
	11th to 20th	Night	41% 14% 25% 15% 4 2	2786
	21st to end	Night	56% 11% 14% 14% 5% 1	2988
August	1st to 10th	Night	54% 8% 19% 15% 4	2814
	11th to 20th	Night	41% 10% 22% 18% 8% 1	2812
	21st to end	Night	29% 9% 12% 27% 20% 3	3379
September	1st to 10th	Night	36% 9% 15% 18% 17% 6%	2072
	11th to 20th	Night	42% 8% 12% 15% 20% 2	2090
	21st to end	Night	42% 6% 12% 17% 17% 6%	2090
October	1st to 10th	Night	33% 6% 8% 20% 26% 7%	3668
	11th to 20th	Night	22% 3 5% 17% 28% 25%	3779
	21st to end	Night	27% 3 5% 21% 26% 18%	4120
November	1st to 10th	Night	34% 4 7% 17% 26% 12%	2341
	11th to 20th	Night	34% 5% 5% 17% 27% 12%	2537
	21st to end	Night	34% 4 6% 22% 27% 7%	2600
December	1st to 10th	Night	43% 5% 8% 17% 22% 6%	2600
	11th to 20th	Night	37% 3 8% 17% 24% 10%	3174
	21st to end	Night	42% 3 8% 21% 23% 3	4578

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% 20% 39% 17% 2	270
	11th to 20th	Day	26% 23% 31% 16% 4	270
	21st to end	Day	21% 23% 40% 12% 3	297
February	1st to 10th	Day	21% 20% 39% 14% 6%	270
	11th to 20th	Day	33% 20% 37% 9% 1	270
	21st to end	Day	29% 21% 35% 14% 2	273
March	1st to 10th	Day	24% 16% 33% 19% 7% 1	460
	11th to 20th	Day	21% 16% 40% 18% 5% 1	460
	21st to end	Day	23% 17% 36% 17% 6% 1	506
April	1st to 10th	Day	20% 17% 34% 19% 9% 1	460
	11th to 20th	Day	17% 15% 32% 23% 11% 3	452
	21st to end	Day	17% 10% 28% 27% 13% 4	460
May	1st to 10th	Day	12% 15% 34% 21% 14% 4	463
	11th to 20th	Day	17% 5% 22% 28% 21% 7%	487
	21st to end	Day	14% 5% 20% 27% 23% 12%	529
June	1st to 10th	Day	10% 3 19% 35% 25% 9%	490
	11th to 20th	Day	9% 4 20% 27% 29% 12%	490
	21st to end	Day	9% 3 15% 35% 28% 11%	490
July	1st to 10th	Day	9% 2 9% 29% 29% 21%	485
	11th to 20th	Day	8% 2 9% 32% 34% 15%	484
	21st to end	Day	7% 2 12% 32% 34% 13%	532
August	1st to 10th	Day	15% 3 15% 29% 24% 15%	486
	11th to 20th	Day	14% 4 10% 27% 29% 16%	479
	21st to end	Day	11% 2 12% 30% 28% 16%	539
September	1st to 10th	Day	9% 4 12% 30% 31% 14%	490
	11th to 20th	Day	17% 4 16% 25% 27% 12%	490
	21st to end	Day	19% 6% 18% 28% 24% 5%	490
October	1st to 10th	Day	16% 5% 23% 26% 23% 8%	490
	11th to 20th	Day	11% 10% 24% 27% 23% 5%	490
	21st to end	Day	15% 9% 23% 27% 20% 5%	539
November	1st to 10th	Day	20% 8% 26% 27% 16% 3	495
	11th to 20th	Day	19% 13% 35% 25% 6% 2	360
	21st to end	Day	15% 13% 34% 25% 11% 2	300
December	1st to 10th	Day	25% 14% 41% 15% 5%	300
	11th to 20th	Day	21% 12% 36% 22% 8% 1	300
	21st to end	Day	26% 16% 34% 14% 7% 3	306
January	1st to 10th	Night	21% 18% 30% 25% 6%	760
	11th to 20th	Night	20% 15% 31% 29% 5%	760
	21st to end	Night	20% 15% 34% 28% 3	836
February	1st to 10th	Night	19% 12% 36% 29% 4	760
	11th to 20th	Night	26% 16% 37% 21% 1	743
	21st to end	Night	20% 16% 37% 23% 4	628
March	1st to 10th	Night	19% 12% 34% 29% 6%	760
	11th to 20th	Night	19% 15% 34% 24% 7% 1	760
	21st to end	Night	20% 14% 32% 27% 7%	836
April	1st to 10th	Night	16% 16% 32% 26% 9%	760
	11th to 20th	Night	14% 15% 27% 31% 12% 1	751
	21st to end	Night	13% 7% 30% 34% 15%	637
May	1st to 10th	Night	10% 9% 31% 35% 15%	570
	11th to 20th	Night	13% 6% 23% 37% 20% 1	561
	21st to end	Night	12% 3 14% 35% 33% 2	617
June	1st to 10th	Night	10% 3 17% 39% 26% 4	570
	11th to 20th	Night	12% 4 14% 30% 31% 8%	570
	21st to end	Night	9% 2 13% 38% 33% 5%	570
July	1st to 10th	Night	11% 2 10% 32% 37% 8%	555
	11th to 20th	Night	9% 2 7% 33% 42% 8%	552
	21st to end	Night	7% 2 13% 30% 41% 6%	624
August	1st to 10th	Night	15% 2 9% 29% 37% 8%	567
	11th to 20th	Night	12% 2 10% 30% 39% 6%	564
	21st to end	Night	11% 2 10% 29% 43% 6%	778
September	1st to 10th	Night	10% 3 11% 30% 39% 6%	760
	11th to 20th	Night	16% 4 11% 28% 36% 5%	760
	21st to end	Night	19% 5% 16% 32% 25% 3	760
October	1st to 10th	Night	16% 5% 17% 30% 26% 6%	760
	11th to 20th	Night	16% 7% 24% 30% 21% 2	760
	21st to end	Night	15% 10% 21% 32% 20% 3	836
November	1st to 10th	Night	16% 7% 25% 32% 17% 3	780
	11th to 20th	Night	15% 11% 30% 33% 11% 1	800
	21st to end	Night	15% 11% 27% 34% 13% 1	800
December	1st to 10th	Night	21% 13% 26% 34% 6% 1	800
	11th to 20th	Night	20% 10% 25% 33% 11% 1	800
	21st to end	Night	24% 13% 25% 29% 8%	851

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