Timber Point:
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Timber Point: clear sky chart from 2005-11-06 to 2024-11-12.

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	10% 12% 5% 11% 8% 6% 6% 5% 6% 7% 23%	106462
	Night	8% 15% 5% 13% 8% 7% 6% 5% 6% 7% 21%	101243
Transparency	Day	57% 8% 14% 16% 5%	106159
	Night	60% 8% 12% 14% 6% 1	101193
Seeing	Day	16% 11% 23% 25% 19% 6%	17271
	Night	15% 8% 20% 31% 22% 4	23596

By Month

Percentage Cloud Cover NW (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	3 12% 5% 20% 15% 12% 9% 3 4 5% 13%	1422
	11th to 20th	Day	4 16% 6% 19% 8% 6% 7% 4 5% 7% 18%	1882
	21st to end	Day	8% 22% 8% 15% 7% 7% 5% 5% 6% 6% 13%	2090
February	1st to 10th	Day	5% 13% 5% 13% 8% 5% 8% 4 8% 9% 22%	1371
	11th to 20th	Day	5% 18% 7% 12% 8% 7% 7% 4 7% 7% 19%	1480
	21st to end	Day	3 12% 7% 12% 9% 7% 5% 5% 7% 9% 25%	1356
March	1st to 10th	Day	2 9% 5% 14% 11% 11% 9% 6% 6% 6% 21%	3126
	11th to 20th	Day	3 15% 7% 16% 8% 6% 6% 5% 6% 8% 20%	3246
	21st to end	Day	2 12% 7% 16% 9% 8% 6% 5% 6% 7% 22%	4165
April	1st to 10th	Day	4 15% 7% 14% 9% 6% 6% 6% 7% 7% 20%	2327
	11th to 20th	Day	3 16% 5% 13% 9% 6% 6% 4 5% 8% 25%	2578
	21st to end	Day	5% 13% 5% 10% 9% 7% 6% 5% 6% 8% 28%	2698
May	1st to 10th	Day	11% 14% 4 8% 6% 6% 5% 4 6% 8% 28%	4856
	11th to 20th	Day	7% 14% 5% 11% 8% 6% 6% 5% 7% 7% 24%	5013
	21st to end	Day	10% 10% 4 9% 7% 6% 6% 5% 7% 7% 30%	5781
June	1st to 10th	Day	13% 13% 4 11% 7% 6% 6% 5% 6% 6% 23%	3353
	11th to 20th	Day	14% 11% 4 11% 7% 7% 5% 5% 6% 8% 22%	3420
	21st to end	Day	10% 10% 4 11% 8% 6% 7% 6% 7% 8% 23%	3420
July	1st to 10th	Day	10% 7% 3 9% 6% 6% 6% 6% 8% 9% 30%	5700
	11th to 20th	Day	18% 12% 4 11% 7% 6% 6% 5% 6% 7% 17%	5270
	21st to end	Day	13% 10% 4 10% 7% 6% 6% 5% 6% 7% 26%	5486
August	1st to 10th	Day	8% 6% 3 7% 5% 5% 5% 4 6% 6% 46%	4970
	11th to 20th	Day	15% 9% 3 7% 5% 5% 4 4 6% 9% 33%	4340
	21st to end	Day	20% 11% 3 8% 6% 5% 6% 5% 7% 8% 20%	4819
September	1st to 10th	Day	18% 12% 5% 10% 6% 7% 6% 5% 6% 6% 19%	2352
	11th to 20th	Day	15% 11% 3 9% 7% 5% 6% 5% 6% 8% 27%	2246
	21st to end	Day	16% 16% 5% 12% 7% 6% 5% 5% 5% 6% 18%	2071
October	1st to 10th	Day	11% 17% 4 10% 8% 8% 7% 5% 7% 7% 15%	3091
	11th to 20th	Day	9% 15% 7% 14% 6% 6% 5% 5% 6% 6% 22%	2843
	21st to end	Day	8% 17% 7% 15% 9% 7% 7% 5% 6% 5% 13%	2748
November	1st to 10th	Day	7% 18% 8% 15% 10% 8% 6% 5% 6% 5% 12%	1372
	11th to 20th	Day	8% 20% 6% 17% 9% 9% 6% 4 6% 6% 9%	1235
	21st to end	Day	6% 18% 6% 17% 9% 5% 9% 4 9% 5% 12%	970
December	1st to 10th	Day	8% 14% 5% 15% 9% 9% 7% 7% 7% 7% 12%	950
	11th to 20th	Day	4 13% 6% 12% 9% 8% 7% 5% 8% 9% 18%	1029
	21st to end	Day	7% 16% 6% 13% 8% 6% 5% 7% 9% 7% 15%	1386
January	1st to 10th	Night	4 16% 6% 17% 15% 14% 9% 3 3 4 9%	5553
	11th to 20th	Night	6% 16% 7% 14% 7% 5% 5% 5% 6% 8% 22%	5016
	21st to end	Night	9% 23% 7% 17% 8% 6% 5% 4 5% 5% 12%	5566
February	1st to 10th	Night	5% 15% 6% 14% 8% 7% 8% 4 6% 8% 19%	2807
	11th to 20th	Night	4 15% 5% 16% 8% 8% 6% 5% 7% 7% 19%	2587
	21st to end	Night	3 12% 6% 12% 8% 6% 5% 5% 7% 7% 30%	2098
March	1st to 10th	Night	2 10% 5% 13% 8% 8% 7% 5% 6% 7% 30%	3738
	11th to 20th	Night	3 16% 7% 13% 8% 7% 7% 5% 5% 6% 21%	3723
	21st to end	Night	3 13% 7% 16% 8% 7% 5% 5% 6% 7% 22%	3477
April	1st to 10th	Night	4 12% 5% 12% 9% 7% 7% 5% 6% 5% 27%	1853
	11th to 20th	Night	3 12% 5% 11% 6% 6% 6% 5% 6% 8% 31%	1551
	21st to end	Night	5% 13% 4 9% 8% 7% 6% 5% 8% 7% 28%	1482
May	1st to 10th	Night	8% 11% 4 10% 5% 5% 5% 4 6% 8% 33%	2102
	11th to 20th	Night	6% 12% 5% 12% 7% 7% 5% 5% 7% 7% 26%	1882
	21st to end	Night	7% 8% 3 8% 6% 5% 6% 5% 8% 9% 35%	1794
June	1st to 10th	Night	11% 5% 3 8% 6% 6% 7% 6% 8% 9% 30%	825
	11th to 20th	Night	11% 10% 4 8% 5% 4 6% 4 7% 11% 29%	760
	21st to end	Night	9% 8% 3 8% 6% 5% 8% 5% 8% 10% 30%	760
July	1st to 10th	Night	9% 6% 3 8% 6% 6% 6% 6% 9% 10% 32%	1260
	11th to 20th	Night	18% 9% 3 10% 8% 6% 5% 5% 6% 7% 22%	1686
	21st to end	Night	15% 9% 3 8% 7% 5% 6% 6% 6% 7% 29%	2066
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 7% 8% 50%	1945
	11th to 20th	Night	12% 8% 2 6% 5% 4 5% 4 7% 9% 38%	2498
	21st to end	Night	18% 13% 5% 10% 5% 6% 5% 4 5% 5% 22%	2848
September	1st to 10th	Night	14% 12% 4 9% 7% 5% 5% 5% 6% 8% 25%	1825
	11th to 20th	Night	10% 10% 3 9% 5% 6% 6% 3 6% 8% 34%	1933
	21st to end	Night	16% 16% 4 11% 6% 6% 5% 4 6% 6% 21%	2108
October	1st to 10th	Night	11% 14% 4 10% 6% 6% 6% 5% 7% 8% 23%	3879
	11th to 20th	Night	10% 18% 6% 12% 7% 6% 6% 4 6% 6% 17%	4085
	21st to end	Night	8% 17% 5% 11% 8% 7% 6% 5% 7% 7% 19%	4794
November	1st to 10th	Night	8% 16% 6% 14% 10% 9% 7% 5% 5% 6% 13%	2926
	11th to 20th	Night	7% 18% 7% 16% 8% 7% 7% 4 7% 6% 11%	2964
	21st to end	Night	7% 19% 7% 16% 9% 8% 6% 5% 6% 6% 11%	3190
December	1st to 10th	Night	6% 18% 7% 15% 11% 8% 7% 5% 6% 7% 9%	3230
	11th to 20th	Night	4 17% 6% 16% 10% 8% 6% 4 7% 8% 14%	4162
	21st to end	Night	7% 17% 6% 12% 8% 7% 8% 6% 7% 6% 17%	6270

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	75% 5% 5% 5% 6% 4	1422
	11th to 20th	Day	64% 6% 6% 7% 14% 3	1900
	21st to end	Day	72% 7% 8% 8% 4 1	2090
February	1st to 10th	Day	57% 8% 7% 14% 11% 2	1371
	11th to 20th	Day	62% 8% 10% 12% 8% 1	1488
	21st to end	Day	54% 11% 12% 16% 7% 1	1356
March	1st to 10th	Day	59% 8% 7% 15% 11% 1	3126
	11th to 20th	Day	59% 6% 14% 14% 7%	3246
	21st to end	Day	56% 12% 14% 12% 5%	4165
April	1st to 10th	Day	61% 7% 15% 12% 4	2327
	11th to 20th	Day	56% 8% 13% 16% 6% 1	2578
	21st to end	Day	53% 8% 17% 16% 5%	2698
May	1st to 10th	Day	53% 7% 13% 23% 5%	4856
	11th to 20th	Day	55% 10% 11% 18% 6%	5016
	21st to end	Day	49% 10% 11% 22% 8%	5782
June	1st to 10th	Day	59% 7% 13% 16% 5%	3353
	11th to 20th	Day	58% 8% 14% 17% 3	3420
	21st to end	Day	55% 10% 16% 14% 4	3420
July	1st to 10th	Day	46% 9% 22% 21% 2	5611
	11th to 20th	Day	64% 8% 14% 12% 1	5175
	21st to end	Day	53% 9% 19% 17% 2	5313
August	1st to 10th	Day	37% 7% 18% 22% 14% 2	4951
	11th to 20th	Day	47% 7% 20% 20% 6%	4382
	21st to end	Day	60% 8% 15% 16% 1	4818
September	1st to 10th	Day	62% 10% 12% 12% 3	2352
	11th to 20th	Day	54% 9% 15% 19% 4	2246
	21st to end	Day	66% 8% 11% 12% 3	2071
October	1st to 10th	Day	66% 6% 11% 15% 1	3091
	11th to 20th	Day	61% 6% 14% 17% 2	2843
	21st to end	Day	70% 8% 11% 9% 2	2748
November	1st to 10th	Day	70% 8% 10% 10% 2	1372
	11th to 20th	Day	73% 7% 7% 11% 2	1235
	21st to end	Day	67% 9% 9% 10% 5%	970
December	1st to 10th	Day	68% 9% 11% 9% 3 1	950
	11th to 20th	Day	59% 8% 5% 19% 10%	1031
	21st to end	Day	64% 7% 6% 15% 7% 1	1386
January	1st to 10th	Night	78% 7% 5% 5% 4 1	5553
	11th to 20th	Night	58% 6% 6% 10% 15% 4	5060
	21st to end	Night	74% 7% 6% 8% 4 1	5566
February	1st to 10th	Night	62% 7% 7% 13% 11% 1	2807
	11th to 20th	Night	61% 8% 11% 13% 7% 1	2590
	21st to end	Night	51% 7% 15% 17% 8% 1	2098
March	1st to 10th	Night	49% 8% 7% 21% 12% 2	3738
	11th to 20th	Night	59% 8% 11% 15% 6% 1	3725
	21st to end	Night	56% 10% 17% 13% 4	3477
April	1st to 10th	Night	53% 8% 15% 18% 6%	1853
	11th to 20th	Night	47% 10% 16% 19% 7% 1	1551
	21st to end	Night	51% 8% 16% 18% 6%	1482
May	1st to 10th	Night	46% 9% 14% 26% 4	2102
	11th to 20th	Night	49% 11% 15% 17% 8% 1	1882
	21st to end	Night	40% 7% 14% 28% 11%	1794
June	1st to 10th	Night	46% 10% 17% 22% 4	825
	11th to 20th	Night	46% 11% 21% 18% 5%	760
	21st to end	Night	44% 12% 21% 20% 2	760
July	1st to 10th	Night	41% 10% 24% 22% 3	1240
	11th to 20th	Night	60% 7% 16% 13% 3	1658
	21st to end	Night	52% 9% 19% 18% 1	2000
August	1st to 10th	Night	31% 7% 19% 27% 13% 2	1939
	11th to 20th	Night	41% 8% 19% 24% 7%	2522
	21st to end	Night	63% 6% 13% 16% 2	2848
September	1st to 10th	Night	56% 9% 19% 16% 1	1825
	11th to 20th	Night	47% 8% 19% 22% 4	1933
	21st to end	Night	64% 6% 12% 14% 4	2108
October	1st to 10th	Night	56% 8% 15% 19% 3	3879
	11th to 20th	Night	66% 6% 11% 15% 1	4085
	21st to end	Night	62% 9% 14% 12% 3	4794
November	1st to 10th	Night	68% 8% 10% 11% 3	2926
	11th to 20th	Night	70% 8% 10% 10% 2	2964
	21st to end	Night	71% 6% 9% 11% 3	3190
December	1st to 10th	Night	73% 7% 8% 9% 3	3230
	11th to 20th	Night	67% 7% 8% 12% 6%	4159
	21st to end	Night	63% 8% 7% 10% 10% 2	6270

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	5% 7% 21% 37% 26% 5%	117
	11th to 20th	Day	10% 6% 27% 25% 25% 7%	180
	21st to end	Day	17% 19% 17% 25% 18% 4	198
February	1st to 10th	Day	11% 7% 24% 36% 16% 5%	334
	11th to 20th	Day	9% 13% 27% 28% 17% 6%	365
	21st to end	Day	9% 10% 30% 29% 17% 6%	307
March	1st to 10th	Day	8% 9% 27% 29% 18% 9%	370
	11th to 20th	Day	11% 10% 31% 26% 19% 3	382
	21st to end	Day	8% 14% 22% 28% 21% 6%	506
April	1st to 10th	Day	10% 16% 27% 24% 19% 3	460
	11th to 20th	Day	8% 13% 23% 26% 22% 7%	592
	21st to end	Day	11% 10% 28% 26% 20% 6%	650
May	1st to 10th	Day	15% 13% 23% 25% 18% 6%	653
	11th to 20th	Day	12% 12% 21% 24% 21% 10%	675
	21st to end	Day	13% 11% 21% 24% 23% 8%	890
June	1st to 10th	Day	17% 11% 20% 24% 21% 6%	870
	11th to 20th	Day	17% 8% 22% 26% 21% 6%	870
	21st to end	Day	15% 9% 20% 26% 23% 7%	870
July	1st to 10th	Day	16% 7% 21% 27% 23% 6%	856
	11th to 20th	Day	21% 12% 17% 23% 20% 6%	745
	21st to end	Day	19% 10% 20% 23% 19% 9%	739
August	1st to 10th	Day	14% 11% 20% 26% 21% 8%	676
	11th to 20th	Day	26% 15% 22% 21% 12% 3	665
	21st to end	Day	26% 12% 25% 20% 15% 3	720
September	1st to 10th	Day	25% 14% 26% 15% 14% 5%	490
	11th to 20th	Day	20% 10% 25% 21% 18% 6%	490
	21st to end	Day	28% 14% 24% 20% 12% 3	480
October	1st to 10th	Day	26% 15% 30% 20% 8% 2	390
	11th to 20th	Day	27% 14% 28% 18% 8% 3	390
	21st to end	Day	13% 10% 25% 30% 18% 3	378
November	1st to 10th	Day	13% 13% 29% 27% 15% 4	200
	11th to 20th	Day	16% 5% 29% 25% 16% 8%	182
	21st to end	Day	11% 14% 29% 26% 11% 9%	180
December	1st to 10th	Day	11% 4 27% 36% 16% 6%	180
	11th to 20th	Day	7% 11% 24% 24% 26% 8%	122
	21st to end	Day	10% 7% 23% 27% 19% 13%	99
January	1st to 10th	Night	11% 7% 21% 35% 21% 5%	1017
	11th to 20th	Night	15% 9% 23% 32% 18% 3	850
	21st to end	Night	14% 11% 23% 31% 18% 2	935
February	1st to 10th	Night	13% 7% 18% 41% 18% 3	850
	11th to 20th	Night	10% 10% 23% 35% 19% 3	834
	21st to end	Night	8% 7% 23% 38% 20% 4	694
March	1st to 10th	Night	8% 7% 21% 33% 25% 5%	760
	11th to 20th	Night	8% 9% 21% 32% 27% 4	746
	21st to end	Night	7% 8% 15% 31% 29% 10%	627
April	1st to 10th	Night	6% 8% 15% 32% 32% 6%	570
	11th to 20th	Night	7% 6% 17% 34% 30% 5%	563
	21st to end	Night	11% 6% 18% 27% 30% 8%	532
May	1st to 10th	Night	13% 6% 16% 31% 28% 6%	380
	11th to 20th	Night	11% 5% 16% 29% 33% 5%	374
	21st to end	Night	10% 6% 16% 29% 33% 6%	411
June	1st to 10th	Night	15% 4 16% 34% 28% 3	255
	11th to 20th	Night	18% 3 13% 31% 32% 3	190
	21st to end	Night	11% 4 15% 27% 39% 4	190
July	1st to 10th	Night	11% 4 15% 32% 35% 3	185
	11th to 20th	Night	16% 7% 18% 27% 28% 4	320
	21st to end	Night	15% 6% 18% 28% 27% 6%	416
August	1st to 10th	Night	16% 6% 16% 27% 31% 4	378
	11th to 20th	Night	20% 8% 21% 27% 21% 4	564
	21st to end	Night	26% 9% 19% 22% 21% 4	627
September	1st to 10th	Night	22% 7% 18% 31% 19% 2	570
	11th to 20th	Night	14% 8% 20% 26% 25% 6%	603
	21st to end	Night	28% 9% 20% 25% 14% 4	760
October	1st to 10th	Night	21% 11% 21% 29% 14% 3	760
	11th to 20th	Night	27% 9% 18% 30% 14% 3	760
	21st to end	Night	17% 9% 23% 31% 17% 4	916
November	1st to 10th	Night	16% 7% 21% 35% 17% 4	880
	11th to 20th	Night	17% 6% 19% 31% 22% 6%	855
	21st to end	Night	16% 8% 26% 29% 17% 4	1000
December	1st to 10th	Night	15% 8% 22% 33% 20% 2	1040
	11th to 20th	Night	15% 7% 18% 37% 18% 5%	1040
	21st to end	Night	15% 9% 21% 31% 19% 6%	1144

Page generated at 2024-11-08 19:45:38. Version ac07

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