Boktuklo Trail Head
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boktuklo Trail Head clear sky chart from 2005-11-06 to 2025-01-22.

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	15% 7% 2 6% 4 4 4 3 5% 6% 44%	105473
	Night	13% 7% 2 5% 3 3 3 3 4 6% 50%	104020
Transparency	Day	39% 5% 10% 22% 19% 5%	109124
	Night	34% 4 9% 22% 22% 8%	108496
Seeing	Day	18% 12% 26% 25% 16% 4	15555
	Night	17% 11% 24% 29% 17% 2	25503

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% 10% 5% 6% 3 3 3 2 3 5% 46%	2937
	11th to 20th	Day	9% 6% 3 5% 4 3 3 3 3 5% 55%	2940
	21st to end	Day	21% 8% 2 5% 3 2 3 2 3 3 45%	3144
February	1st to 10th	Day	22% 10% 3 6% 4 4 3 2 2 4 40%	1710
	11th to 20th	Day	19% 10% 2 6% 4 4 4 3 4 5% 40%	1762
	21st to end	Day	23% 9% 3 6% 3 3 3 2 4 5% 40%	1698
March	1st to 10th	Day	20% 9% 3 6% 4 3 3 3 3 4 42%	3436
	11th to 20th	Day	16% 8% 3 7% 5% 4 4 3 5% 6% 39%	3480
	21st to end	Day	20% 11% 3 6% 4 3 3 3 4 5% 37%	3814
April	1st to 10th	Day	17% 8% 3 5% 5% 4 4 3 4 6% 42%	2138
	11th to 20th	Day	19% 6% 2 7% 4 5% 4 3 4 5% 41%	2254
	21st to end	Day	20% 8% 2 6% 5% 5% 4 3 4 5% 39%	2280
May	1st to 10th	Day	25% 8% 2 5% 4 4 3 3 4 5% 36%	4080
	11th to 20th	Day	14% 6% 2 8% 4 4 4 4 6% 6% 41%	4082
	21st to end	Day	21% 8% 3 8% 5% 4 4 3 5% 6% 32%	4477
June	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 6% 9% 42%	2470
	11th to 20th	Day	9% 6% 2 6% 6% 6% 5% 5% 6% 6% 43%	2470
	21st to end	Day	5% 6% 2 4 4 5% 4 5% 6% 9% 50%	2470
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 7% 9% 43%	4120
	11th to 20th	Day	5% 3 1 5% 4 4 5% 4 6% 8% 55%	4120
	21st to end	Day	11% 6% 2 8% 6% 6% 6% 5% 7% 9% 33%	4465
August	1st to 10th	Day	4 3 1 5% 4 4 5% 4 6% 8% 55%	4104
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 7% 10% 47%	3992
	21st to end	Day	5% 4 2 6% 4 5% 6% 5% 7% 8% 48%	4180
September	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 5% 6% 47%	2218
	11th to 20th	Day	10% 4 2 6% 5% 5% 4 5% 6% 7% 46%	2090
	21st to end	Day	9% 4 2 5% 4 4 5% 4 5% 6% 53%	2090
October	1st to 10th	Day	9% 5% 2 6% 3 2 4 3 4 6% 55%	1916
	11th to 20th	Day	16% 4 2 4 3 3 2 2 3 3 58%	1900
	21st to end	Day	19% 7% 2 4 2 3 3 2 4 4 49%	2090
November	1st to 10th	Day	16% 6% 2 5% 4 3 2 2 5% 6% 50%	1958
	11th to 20th	Day	13% 6% 2 4 3 2 3 2 4 6% 55%	1969
	21st to end	Day	19% 6% 2 4 3 4 3 2 3 5% 49%	1800
December	1st to 10th	Day	19% 7% 2 4 2 3 3 2 3 4 50%	2940
	11th to 20th	Day	23% 8% 2 5% 3 3 3 3 4 5% 43%	3391
	21st to end	Day	23% 11% 3 5% 3 3 2 3 4 5% 38%	4488
January	1st to 10th	Night	13% 9% 4 7% 4 3 3 3 4 5% 46%	4238
	11th to 20th	Night	12% 7% 2 5% 3 2 2 2 4 4 56%	4250
	21st to end	Night	23% 8% 3 4 3 2 2 3 4 4 46%	4546
February	1st to 10th	Night	19% 9% 3 5% 4 2 4 3 4 4 42%	2470
	11th to 20th	Night	18% 9% 3 6% 4 3 3 3 4 5% 44%	2322
	21st to end	Night	18% 8% 2 6% 2 3 3 3 4 5% 46%	1756
March	1st to 10th	Night	22% 10% 3 6% 3 2 3 2 4 4 40%	3419
	11th to 20th	Night	17% 8% 2 5% 4 3 3 2 4 5% 47%	3480
	21st to end	Night	15% 8% 2 8% 5% 4 3 3 5% 6% 41%	3817
April	1st to 10th	Night	14% 7% 3 5% 4 4 3 3 5% 5% 47%	2040
	11th to 20th	Night	15% 7% 2 6% 4 4 3 2 4 6% 47%	1875
	21st to end	Night	14% 7% 2 6% 4 3 3 3 5% 7% 45%	1897
May	1st to 10th	Night	21% 9% 2 5% 4 3 3 4 5% 7% 37%	2823
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 6% 7% 44%	2823
	21st to end	Night	17% 7% 2 6% 4 4 3 3 6% 8% 40%	3090
June	1st to 10th	Night	6% 5% 2 5% 3 3 3 4 5% 8% 56%	1710
	11th to 20th	Night	6% 5% 1 4 4 2 3 3 5% 9% 57%	1710
	21st to end	Night	5% 4 1 3 2 3 3 3 6% 9% 63%	1710
July	1st to 10th	Night	8% 4 2 5% 4 4 4 4 6% 9% 50%	2850
	11th to 20th	Night	5% 2 1 3 2 2 3 3 5% 8% 65%	2850
	21st to end	Night	9% 7% 2 6% 3 4 5% 4 6% 8% 45%	3098
August	1st to 10th	Night	2 2 1 3 2 4 3 3 5% 7% 68%	2836
	11th to 20th	Night	5% 3 2 4 3 3 3 4 6% 9% 60%	2842
	21st to end	Night	3 3 1 4 3 3 3 3 5% 10% 61%	3476
September	1st to 10th	Night	6% 6% 2 4 4 3 4 4 6% 7% 57%	1957
	11th to 20th	Night	10% 4 2 5% 4 4 4 4 5% 7% 51%	2090
	21st to end	Night	9% 4 1 4 3 3 3 3 4 5% 60%	2090
October	1st to 10th	Night	8% 4 2 4 3 3 3 3 5% 7% 59%	2243
	11th to 20th	Night	14% 4 2 4 2 2 3 2 3 5% 60%	2280
	21st to end	Night	17% 6% 2 4 3 3 2 2 3 3 55%	2508
November	1st to 10th	Night	13% 6% 2 4 3 3 3 3 3 5% 56%	2340
	11th to 20th	Night	10% 6% 2 4 3 3 3 3 4 5% 57%	2428
	21st to end	Night	16% 8% 3 5% 3 2 2 2 4 5% 49%	2600
December	1st to 10th	Night	14% 9% 3 5% 3 3 3 2 4 5% 50%	4250
	11th to 20th	Night	21% 7% 3 6% 4 3 2 2 3 3 47%	4816
	21st to end	Night	19% 11% 4 6% 4 3 3 2 3 5% 41%	6490

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	43% 3 5% 23% 21% 4	2938
	11th to 20th	Day	32% 3 13% 25% 23% 4	2940
	21st to end	Day	44% 4 5% 18% 22% 7%	3144
February	1st to 10th	Day	51% 2 8% 15% 20% 4	1710
	11th to 20th	Day	47% 4 6% 19% 19% 5%	1771
	21st to end	Day	48% 3 5% 15% 20% 8%	1698
March	1st to 10th	Day	46% 3 7% 13% 20% 10%	3436
	11th to 20th	Day	45% 6% 11% 17% 16% 5%	3480
	21st to end	Day	49% 5% 8% 21% 16% 2	3814
April	1st to 10th	Day	44% 4 9% 18% 19% 6%	2138
	11th to 20th	Day	45% 5% 7% 20% 18% 5%	2254
	21st to end	Day	48% 6% 7% 19% 18% 3	2280
May	1st to 10th	Day	50% 5% 9% 21% 13% 2	4118
	11th to 20th	Day	40% 7% 12% 22% 18% 1	4086
	21st to end	Day	52% 7% 11% 16% 12% 3	4489
June	1st to 10th	Day	37% 8% 14% 26% 13% 2	2470
	11th to 20th	Day	38% 8% 12% 23% 18% 2	2470
	21st to end	Day	29% 7% 14% 28% 19% 2	2470
July	1st to 10th	Day	35% 7% 20% 25% 11% 1	4056
	11th to 20th	Day	25% 6% 10% 36% 21% 1	4051
	21st to end	Day	42% 9% 14% 25% 9%	4325
August	1st to 10th	Day	24% 6% 13% 28% 25% 4	4090
	11th to 20th	Day	32% 6% 18% 31% 11% 1	4031
	21st to end	Day	30% 8% 14% 35% 12% 2	4179
September	1st to 10th	Day	36% 5% 10% 21% 18% 10%	2218
	11th to 20th	Day	35% 7% 11% 23% 18% 7%	2090
	21st to end	Day	31% 7% 9% 17% 27% 9%	2090
October	1st to 10th	Day	19% 2 6% 11% 35% 27%	3176
	11th to 20th	Day	22% 1 4 17% 36% 19%	3140
	21st to end	Day	32% 3 5% 28% 23% 7%	3428
November	1st to 10th	Day	37% 3 7% 22% 24% 8%	1958
	11th to 20th	Day	32% 4 6% 21% 26% 11%	1969
	21st to end	Day	39% 3 6% 19% 26% 7%	1800
December	1st to 10th	Day	39% 4 6% 27% 20% 4	2940
	11th to 20th	Day	45% 2 6% 18% 25% 5%	3389
	21st to end	Day	50% 3 6% 20% 18% 4	4488
January	1st to 10th	Night	40% 4 7% 18% 27% 5%	4238
	11th to 20th	Night	33% 4 10% 20% 26% 7%	4250
	21st to end	Night	43% 4 7% 16% 23% 7%	4546
February	1st to 10th	Night	45% 4 9% 19% 17% 7%	2470
	11th to 20th	Night	44% 3 5% 20% 21% 6%	2323
	21st to end	Night	40% 4 8% 17% 21% 10%	1756
March	1st to 10th	Night	48% 4 5% 15% 16% 11%	3419
	11th to 20th	Night	40% 5% 8% 24% 14% 10%	3480
	21st to end	Night	42% 5% 9% 19% 21% 2	3817
April	1st to 10th	Night	39% 4 9% 19% 19% 10%	2040
	11th to 20th	Night	38% 4 8% 21% 20% 9%	1875
	21st to end	Night	38% 6% 9% 23% 22% 2	1897
May	1st to 10th	Night	47% 7% 10% 18% 13% 5%	2850
	11th to 20th	Night	37% 7% 14% 24% 16% 2	2824
	21st to end	Night	41% 8% 15% 21% 11% 5%	3099
June	1st to 10th	Night	26% 7% 16% 29% 19% 3	1710
	11th to 20th	Night	25% 6% 11% 33% 22% 3	1710
	21st to end	Night	20% 5% 13% 30% 28% 4	1710
July	1st to 10th	Night	29% 7% 21% 26% 15% 2	2805
	11th to 20th	Night	17% 5% 11% 43% 22% 2	2796
	21st to end	Night	35% 7% 15% 28% 15% 1	2999
August	1st to 10th	Night	15% 5% 14% 29% 30% 7%	2826
	11th to 20th	Night	21% 5% 20% 35% 17% 2	2869
	21st to end	Night	21% 6% 15% 36% 20% 2	3476
September	1st to 10th	Night	27% 6% 11% 23% 22% 11%	1957
	11th to 20th	Night	31% 6% 12% 21% 21% 8%	2090
	21st to end	Night	27% 4 7% 22% 30% 10%	2090
October	1st to 10th	Night	15% 3 7% 13% 27% 35%	3750
	11th to 20th	Night	21% 2 4 15% 39% 19%	3779
	21st to end	Night	30% 3 5% 26% 26% 11%	4120
November	1st to 10th	Night	32% 3 7% 21% 24% 11%	2340
	11th to 20th	Night	30% 3 8% 20% 26% 13%	2428
	21st to end	Night	39% 3 6% 18% 28% 7%	2600
December	1st to 10th	Night	38% 3 7% 24% 23% 5%	4250
	11th to 20th	Night	44% 3 4 16% 21% 11%	4817
	21st to end	Night	46% 3 9% 18% 20% 5%	6490

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% 21% 33% 12% 5%	300
	11th to 20th	Day	26% 27% 33% 10% 3	300
	21st to end	Day	26% 27% 31% 13% 3	300
February	1st to 10th	Day	34% 20% 30% 11% 5%	270
	11th to 20th	Day	37% 26% 28% 8% 1	270
	21st to end	Day	41% 28% 22% 8% 2	225
March	1st to 10th	Day	33% 22% 30% 14% 1	270
	11th to 20th	Day	40% 23% 24% 10% 3	270
	21st to end	Day	32% 23% 35% 8% 2	297
April	1st to 10th	Day	30% 20% 33% 12% 5%	318
	11th to 20th	Day	34% 16% 31% 13% 7%	452
	21st to end	Day	26% 20% 29% 18% 6% 1	460
May	1st to 10th	Day	23% 17% 37% 19% 4 1	651
	11th to 20th	Day	19% 12% 34% 24% 8% 2	675
	21st to end	Day	16% 10% 36% 20% 16% 2	734
June	1st to 10th	Day	12% 8% 23% 32% 21% 5%	680
	11th to 20th	Day	10% 5% 29% 35% 18% 4	680
	21st to end	Day	5% 5% 25% 35% 20% 9%	680
July	1st to 10th	Day	8% 3 17% 35% 29% 7%	671
	11th to 20th	Day	4 1 16% 36% 33% 9%	668
	21st to end	Day	6% 3 13% 35% 33% 10%	739
August	1st to 10th	Day	6% 3 14% 41% 31% 6%	676
	11th to 20th	Day	11% 3 14% 37% 28% 6%	642
	21st to end	Day	8% 1 9% 32% 38% 11%	539
September	1st to 10th	Day	9% 1 10% 38% 33% 9%	428
	11th to 20th	Day	5% 4 24% 38% 25% 4	300
	21st to end	Day	16% 7% 21% 31% 20% 5%	300
October	1st to 10th	Day	7% 7% 37% 29% 18% 2	300
	11th to 20th	Day	17% 14% 37% 26% 5% 1	300
	21st to end	Day	31% 15% 30% 18% 5% 1	330
November	1st to 10th	Day	19% 20% 32% 21% 6% 1	300
	11th to 20th	Day	21% 18% 37% 17% 5% 1	300
	21st to end	Day	30% 21% 29% 15% 5%	300
December	1st to 10th	Day	27% 22% 31% 15% 4 1	300
	11th to 20th	Day	31% 24% 30% 9% 5%	300
	21st to end	Day	29% 23% 35% 9% 3 1	330
January	1st to 10th	Night	22% 16% 31% 26% 5%	1000
	11th to 20th	Night	24% 18% 29% 24% 5% 1	1000
	21st to end	Night	21% 16% 30% 28% 5%	1051
February	1st to 10th	Night	26% 17% 28% 24% 5%	950
	11th to 20th	Night	26% 21% 29% 22% 2	848
	21st to end	Night	29% 18% 31% 19% 4	500
March	1st to 10th	Night	25% 15% 26% 29% 5%	570
	11th to 20th	Night	24% 15% 28% 29% 5% 1	570
	21st to end	Night	21% 19% 33% 21% 6%	627
April	1st to 10th	Night	19% 19% 31% 25% 6%	570
	11th to 20th	Night	21% 17% 27% 27% 8%	563
	21st to end	Night	19% 16% 32% 22% 10% 1	570
May	1st to 10th	Night	16% 10% 32% 33% 9%	570
	11th to 20th	Night	15% 8% 30% 29% 17% 1	561
	21st to end	Night	15% 6% 28% 28% 21% 2	617
June	1st to 10th	Night	8% 5% 16% 35% 34% 3	570
	11th to 20th	Night	8% 3 21% 38% 28% 1	570
	21st to end	Night	5% 2 18% 35% 35% 6%	570
July	1st to 10th	Night	4 2 10% 32% 46% 6%	555
	11th to 20th	Night	4 1 10% 33% 45% 7%	552
	21st to end	Night	5% 2 8% 33% 46% 7%	624
August	1st to 10th	Night	3 1 10% 37% 45% 5%	567
	11th to 20th	Night	8% 2 7% 38% 38% 7%	564
	21st to end	Night	6% 1 10% 36% 40% 7%	627
September	1st to 10th	Night	7% 3 10% 37% 38% 5%	570
	11th to 20th	Night	12% 2 11% 35% 35% 4	570
	21st to end	Night	11% 3 16% 33% 33% 4	570
October	1st to 10th	Night	9% 4 19% 36% 28% 3	723
	11th to 20th	Night	16% 9% 27% 30% 16% 1	760
	21st to end	Night	21% 12% 25% 27% 14% 2	836
November	1st to 10th	Night	17% 10% 29% 33% 12% 1	780
	11th to 20th	Night	16% 14% 28% 31% 11%	828
	21st to end	Night	24% 16% 26% 24% 10% 1	1000
December	1st to 10th	Night	23% 13% 28% 31% 6%	1000
	11th to 20th	Night	27% 14% 26% 27% 6%	1000
	21st to end	Night	24% 17% 27% 25% 7%	1100

Page generated at 2025-01-19 02:06:44. Version ac07

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