Teulon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teulon clear sky chart from 2005-11-06 to 2024-11-04.

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	11% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	105589
	Night	9% 10% 4 9% 6% 5% 5% 4 6% 7% 35%	102020
Transparency	Day	45% 8% 16% 23% 7%	105331
	Night	46% 7% 15% 23% 9% 1	101925
Seeing	Day	13% 9% 30% 29% 15% 4	16268
	Night	14% 7% 30% 33% 14% 2	26179

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	8% 15% 5% 11% 8% 9% 8% 5% 6% 5% 20%	2219
	11th to 20th	Day	5% 10% 6% 20% 13% 9% 7% 5% 7% 8% 11%	2199
	21st to end	Day	7% 17% 7% 15% 7% 7% 6% 4 5% 7% 17%	2762
February	1st to 10th	Day	9% 12% 5% 12% 9% 8% 8% 5% 8% 5% 19%	1605
	11th to 20th	Day	7% 10% 4 11% 6% 7% 7% 6% 7% 9% 26%	1664
	21st to end	Day	6% 13% 4 11% 7% 6% 6% 6% 6% 7% 27%	1484
March	1st to 10th	Day	11% 10% 4 12% 8% 6% 5% 5% 7% 8% 25%	3191
	11th to 20th	Day	8% 10% 6% 13% 10% 7% 6% 4 5% 7% 24%	3478
	21st to end	Day	7% 11% 6% 13% 7% 6% 5% 4 5% 6% 31%	3814
April	1st to 10th	Day	9% 11% 3 8% 6% 4 5% 4 6% 7% 37%	2328
	11th to 20th	Day	13% 10% 3 9% 5% 6% 5% 4 5% 6% 36%	2442
	21st to end	Day	14% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	2470
May	1st to 10th	Day	17% 9% 2 7% 4 4 4 4 5% 7% 37%	4276
	11th to 20th	Day	20% 8% 3 8% 5% 4 5% 3 5% 6% 33%	4664
	21st to end	Day	20% 7% 3 7% 5% 4 4 4 4 6% 35%	5173
June	1st to 10th	Day	15% 8% 3 6% 5% 4 6% 4 6% 8% 36%	2850
	11th to 20th	Day	15% 7% 3 6% 5% 5% 5% 5% 6% 7% 35%	2850
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 36%	2850
July	1st to 10th	Day	9% 4 2 5% 5% 6% 6% 5% 7% 10% 39%	4750
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 49%	4750
	21st to end	Day	6% 4 2 5% 4 4 5% 4 6% 9% 51%	5129
August	1st to 10th	Day	6% 5% 2 6% 5% 5% 5% 5% 7% 9% 46%	4300
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 3 5% 8% 46%	4041
	21st to end	Day	13% 5% 2 6% 4 3 4 3 5% 8% 46%	4532
September	1st to 10th	Day	10% 5% 2 6% 3 4 4 3 5% 8% 50%	2366
	11th to 20th	Day	12% 8% 3 9% 5% 5% 4 3 6% 8% 37%	2090
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 8% 41%	2090
October	1st to 10th	Day	13% 7% 2 7% 4 5% 5% 3 4 7% 43%	3210
	11th to 20th	Day	9% 10% 4 7% 5% 4 5% 4 6% 9% 37%	3054
	21st to end	Day	14% 12% 3 9% 4 4 4 4 6% 8% 33%	3091
November	1st to 10th	Day	16% 15% 4 11% 5% 5% 5% 4 5% 5% 26%	1525
	11th to 20th	Day	8% 16% 5% 13% 6% 5% 5% 4 5% 7% 25%	1520
	21st to end	Day	13% 15% 6% 11% 7% 5% 5% 3 4 7% 25%	1371
December	1st to 10th	Day	8% 14% 5% 15% 10% 6% 5% 5% 6% 7% 17%	1330
	11th to 20th	Day	10% 14% 6% 14% 7% 5% 6% 5% 6% 6% 20%	1679
	21st to end	Day	9% 12% 5% 10% 6% 6% 6% 4 6% 7% 29%	2442
January	1st to 10th	Night	5% 14% 6% 12% 7% 9% 8% 5% 7% 7% 21%	4737
	11th to 20th	Night	5% 14% 6% 17% 11% 10% 9% 5% 6% 5% 14%	4709
	21st to end	Night	8% 17% 8% 15% 7% 6% 6% 4 6% 5% 19%	4905
February	1st to 10th	Night	8% 13% 4 12% 7% 7% 6% 5% 5% 8% 26%	2575
	11th to 20th	Night	7% 9% 3 9% 6% 6% 8% 5% 6% 7% 34%	2403
	21st to end	Night	6% 12% 4 9% 6% 5% 6% 5% 6% 7% 34%	1987
March	1st to 10th	Night	10% 11% 3 11% 7% 5% 5% 4 6% 9% 29%	3670
	11th to 20th	Night	5% 8% 3 8% 6% 5% 5% 5% 6% 9% 42%	3480
	21st to end	Night	9% 13% 5% 9% 5% 4 4 4 5% 7% 36%	3817
April	1st to 10th	Night	10% 7% 2 6% 6% 4 5% 5% 7% 8% 41%	1848
	11th to 20th	Night	14% 9% 3 7% 6% 4 5% 5% 5% 6% 35%	1689
	21st to end	Night	11% 8% 2 7% 6% 5% 5% 4 5% 6% 39%	1710
May	1st to 10th	Night	18% 9% 4 6% 4 4 4 4 6% 6% 36%	2693
	11th to 20th	Night	18% 5% 2 5% 4 5% 4 4 6% 7% 40%	2238
	21st to end	Night	17% 6% 2 6% 4 3 3 3 5% 6% 44%	2414
June	1st to 10th	Night	11% 8% 2 6% 4 5% 4 5% 6% 10% 39%	1330
	11th to 20th	Night	14% 6% 2 5% 5% 4 5% 5% 6% 7% 41%	1330
	21st to end	Night	9% 5% 2 6% 5% 4 4 4 9% 10% 42%	1330
July	1st to 10th	Night	8% 3 2 5% 3 3 5% 4 5% 10% 53%	2220
	11th to 20th	Night	6% 3 2 4 3 4 4 3 6% 10% 54%	2220
	21st to end	Night	4 3 2 4 4 4 4 5% 7% 9% 53%	2434
August	1st to 10th	Night	6% 3 2 5% 4 5% 4 4 7% 9% 51%	2639
	11th to 20th	Night	7% 4 1 4 4 4 4 4 7% 10% 51%	2798
	21st to end	Night	10% 6% 3 6% 3 4 4 4 5% 8% 47%	3135
September	1st to 10th	Night	9% 5% 2 6% 4 3 4 3 5% 8% 51%	1809
	11th to 20th	Night	12% 6% 2 7% 5% 4 5% 2 6% 8% 45%	2090
	21st to end	Night	15% 6% 2 7% 4 4 3 3 4 8% 42%	2090
October	1st to 10th	Night	13% 7% 2 5% 3 3 4 3 5% 8% 47%	3704
	11th to 20th	Night	9% 8% 2 7% 5% 5% 5% 4 7% 8% 40%	3865
	21st to end	Night	9% 9% 3 8% 5% 5% 5% 4 5% 7% 39%	4467
November	1st to 10th	Night	13% 14% 4 9% 6% 5% 5% 4 6% 6% 28%	2624
	11th to 20th	Night	9% 16% 6% 12% 6% 5% 5% 4 5% 6% 27%	2660
	21st to end	Night	12% 14% 5% 13% 6% 6% 5% 4 5% 5% 25%	2807
December	1st to 10th	Night	6% 13% 5% 13% 10% 7% 6% 4 6% 8% 22%	2850
	11th to 20th	Night	8% 16% 7% 13% 6% 5% 6% 4 5% 7% 23%	3518
	21st to end	Night	8% 11% 4 12% 8% 7% 6% 4 6% 7% 28%	5225

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	64% 6% 14% 14% 3	2219
	11th to 20th	Day	69% 5% 11% 12% 3	2220
	21st to end	Day	65% 7% 10% 13% 5%	2762
February	1st to 10th	Day	61% 7% 12% 11% 8% 1	1605
	11th to 20th	Day	50% 8% 14% 20% 7%	1673
	21st to end	Day	53% 8% 12% 18% 8%	1484
March	1st to 10th	Day	54% 7% 15% 19% 5%	3191
	11th to 20th	Day	57% 10% 12% 16% 5%	3480
	21st to end	Day	52% 7% 14% 20% 7%	3814
April	1st to 10th	Day	45% 8% 13% 24% 10% 1	2328
	11th to 20th	Day	47% 7% 11% 21% 12% 2	2442
	21st to end	Day	44% 8% 16% 24% 7% 1	2470
May	1st to 10th	Day	44% 7% 13% 26% 10%	4276
	11th to 20th	Day	50% 7% 9% 21% 11% 1	4668
	21st to end	Day	47% 9% 12% 22% 10%	5173
June	1st to 10th	Day	44% 9% 15% 21% 11% 1	2850
	11th to 20th	Day	44% 9% 15% 20% 11% 1	2850
	21st to end	Day	42% 11% 18% 22% 8%	2850
July	1st to 10th	Day	36% 11% 23% 23% 6%	4676
	11th to 20th	Day	27% 8% 22% 36% 6%	4669
	21st to end	Day	28% 8% 22% 35% 7%	4967
August	1st to 10th	Day	31% 8% 20% 31% 9%	4284
	11th to 20th	Day	34% 8% 22% 30% 5%	4080
	21st to end	Day	36% 7% 24% 27% 5%	4531
September	1st to 10th	Day	32% 8% 19% 32% 8% 1	2366
	11th to 20th	Day	44% 9% 18% 25% 4	2090
	21st to end	Day	41% 7% 17% 28% 7%	2090
October	1st to 10th	Day	41% 6% 16% 30% 8%	3210
	11th to 20th	Day	42% 7% 13% 27% 10%	3054
	21st to end	Day	49% 7% 19% 20% 5%	3091
November	1st to 10th	Day	58% 9% 13% 15% 4 1	1525
	11th to 20th	Day	57% 11% 14% 14% 4	1520
	21st to end	Day	60% 6% 18% 13% 3	1371
December	1st to 10th	Day	64% 10% 13% 10% 3	1330
	11th to 20th	Day	61% 8% 15% 12% 4	1680
	21st to end	Day	53% 8% 13% 18% 8%	2442
January	1st to 10th	Night	59% 9% 13% 15% 5%	4737
	11th to 20th	Night	70% 7% 8% 13% 3	4750
	21st to end	Night	64% 6% 11% 14% 4	4905
February	1st to 10th	Night	56% 7% 12% 15% 9%	2575
	11th to 20th	Night	45% 8% 16% 21% 9%	2404
	21st to end	Night	48% 8% 12% 22% 10%	1987
March	1st to 10th	Night	50% 8% 12% 22% 8%	3670
	11th to 20th	Night	36% 9% 18% 25% 12% 1	3480
	21st to end	Night	47% 7% 11% 25% 10% 1	3817
April	1st to 10th	Night	38% 6% 13% 24% 17% 3	1848
	11th to 20th	Night	47% 6% 10% 20% 15% 2	1689
	21st to end	Night	44% 7% 12% 23% 12% 2	1710
May	1st to 10th	Night	44% 8% 11% 23% 13%	2693
	11th to 20th	Night	40% 8% 13% 27% 9% 3	2238
	21st to end	Night	40% 8% 11% 29% 11% 1	2414
June	1st to 10th	Night	40% 9% 16% 21% 13% 1	1330
	11th to 20th	Night	39% 8% 17% 20% 14% 2	1330
	21st to end	Night	34% 8% 25% 24% 9% 1	1330
July	1st to 10th	Night	27% 11% 20% 33% 8% 1	2185
	11th to 20th	Night	24% 8% 21% 37% 8% 1	2178
	21st to end	Night	26% 7% 22% 35% 9% 1	2357
August	1st to 10th	Night	28% 7% 18% 33% 14%	2631
	11th to 20th	Night	26% 7% 27% 31% 9%	2825
	21st to end	Night	33% 7% 18% 33% 9%	3135
September	1st to 10th	Night	32% 7% 17% 32% 12%	1809
	11th to 20th	Night	37% 8% 19% 25% 10% 1	2090
	21st to end	Night	41% 6% 16% 27% 9% 1	2090
October	1st to 10th	Night	38% 7% 12% 31% 12%	3704
	11th to 20th	Night	41% 6% 14% 28% 10%	3865
	21st to end	Night	44% 7% 16% 29% 4	4467
November	1st to 10th	Night	56% 8% 15% 15% 5% 1	2624
	11th to 20th	Night	59% 9% 14% 13% 5%	2660
	21st to end	Night	62% 7% 14% 13% 4	2807
December	1st to 10th	Night	59% 8% 17% 12% 4	2850
	11th to 20th	Night	58% 8% 15% 13% 6%	3516
	21st to end	Night	53% 8% 12% 16% 10% 1	5225

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	10% 7% 33% 32% 14% 4	270
	11th to 20th	Day	10% 7% 32% 34% 16% 2	270
	21st to end	Day	16% 6% 28% 30% 15% 5%	297
February	1st to 10th	Day	12% 6% 33% 37% 8% 3	270
	11th to 20th	Day	10% 11% 31% 28% 14% 5%	270
	21st to end	Day	6% 9% 37% 31% 16% 1	225
March	1st to 10th	Day	15% 8% 30% 31% 15% 1	270
	11th to 20th	Day	10% 8% 36% 28% 15% 3	270
	21st to end	Day	11% 7% 33% 32% 14% 3	297
April	1st to 10th	Day	11% 7% 33% 34% 10% 3	508
	11th to 20th	Day	16% 12% 28% 30% 12% 2	640
	21st to end	Day	14% 10% 36% 26% 12% 2	650
May	1st to 10th	Day	16% 12% 31% 28% 11% 2	653
	11th to 20th	Day	19% 11% 26% 25% 16% 3	675
	21st to end	Day	20% 10% 23% 27% 17% 3	734
June	1st to 10th	Day	15% 12% 28% 25% 14% 6%	680
	11th to 20th	Day	16% 11% 31% 27% 11% 4	680
	21st to end	Day	11% 7% 25% 32% 19% 5%	680
July	1st to 10th	Day	9% 6% 29% 28% 19% 9%	671
	11th to 20th	Day	12% 8% 25% 31% 17% 6%	668
	21st to end	Day	5% 5% 29% 32% 20% 9%	739
August	1st to 10th	Day	7% 6% 29% 32% 20% 7%	676
	11th to 20th	Day	10% 6% 22% 31% 22% 8%	665
	21st to end	Day	12% 8% 27% 30% 20% 3	748
September	1st to 10th	Day	9% 9% 31% 34% 14% 2	576
	11th to 20th	Day	15% 10% 38% 25% 9% 3	300
	21st to end	Day	21% 5% 32% 31% 10% 1	300
October	1st to 10th	Day	20% 11% 27% 28% 10% 3	300
	11th to 20th	Day	13% 15% 33% 26% 11% 2	300
	21st to end	Day	22% 10% 32% 22% 12% 2	330
November	1st to 10th	Day	25% 10% 24% 30% 9% 2	279
	11th to 20th	Day	14% 11% 37% 27% 10% 1	270
	21st to end	Day	17% 14% 37% 27% 5%	270
December	1st to 10th	Day	13% 8% 36% 25% 16% 3	270
	11th to 20th	Day	13% 8% 39% 30% 9% 1	270
	21st to end	Day	11% 8% 30% 30% 16% 5%	297
January	1st to 10th	Night	11% 7% 36% 31% 13% 2	950
	11th to 20th	Night	14% 7% 32% 34% 11% 1	950
	21st to end	Night	15% 6% 31% 34% 13% 1	1045
February	1st to 10th	Night	14% 6% 27% 37% 15% 1	950
	11th to 20th	Night	11% 6% 30% 35% 15% 3	929
	21st to end	Night	10% 6% 35% 30% 17% 2	731
March	1st to 10th	Night	14% 6% 30% 30% 16% 2	722
	11th to 20th	Night	10% 6% 42% 29% 12% 2	570
	21st to end	Night	17% 5% 30% 31% 13% 4	627
April	1st to 10th	Night	14% 5% 31% 37% 11% 2	570
	11th to 20th	Night	18% 6% 28% 35% 13% 1	563
	21st to end	Night	15% 8% 31% 34% 11% 1	570
May	1st to 10th	Night	18% 8% 28% 35% 10% 1	570
	11th to 20th	Night	17% 7% 31% 30% 15% 1	561
	21st to end	Night	18% 8% 28% 33% 13%	617
June	1st to 10th	Night	15% 6% 29% 31% 18% 1	570
	11th to 20th	Night	15% 7% 28% 35% 14% 1	570
	21st to end	Night	11% 5% 22% 40% 20% 1	570
July	1st to 10th	Night	7% 4 23% 42% 23% 1	555
	11th to 20th	Night	7% 4 25% 40% 21% 2	552
	21st to end	Night	8% 3 20% 42% 24% 4	624
August	1st to 10th	Night	8% 4 19% 47% 20% 2	567
	11th to 20th	Night	8% 4 21% 40% 23% 4	564
	21st to end	Night	12% 5% 22% 40% 20% 1	627
September	1st to 10th	Night	10% 5% 30% 34% 19% 2	570
	11th to 20th	Night	14% 7% 26% 39% 13%	570
	21st to end	Night	17% 5% 33% 32% 12% 1	570
October	1st to 10th	Night	21% 6% 33% 31% 8%	703
	11th to 20th	Night	18% 8% 32% 30% 11% 1	809
	21st to end	Night	20% 9% 30% 30% 10% 1	1045
November	1st to 10th	Night	19% 8% 35% 26% 11% 1	943
	11th to 20th	Night	16% 9% 36% 26% 9% 3	950
	21st to end	Night	18% 10% 40% 26% 7% 1	950
December	1st to 10th	Night	11% 8% 31% 36% 13% 2	950
	11th to 20th	Night	15% 9% 36% 30% 9% 1	950
	21st to end	Night	18% 7% 30% 30% 13% 2	1045

Page generated at 2024-11-01 21:47:51. Version ac07

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