Otter Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Otter Point clear sky chart from 2005-11-06 to 2024-04-25.

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	16% 8% 4 7% 7% 4 5% 5% 6% 7% 32%	82981
	Night	20% 10% 4 8% 7% 4 5% 5% 5% 6% 27%	86155
Transparency	Day	48% 10% 17% 18% 6% 1	82691
	Night	53% 10% 15% 16% 6% 1	86025
Seeing	Day	17% 9% 24% 27% 19% 4	14675
	Night	23% 8% 19% 26% 19% 4	23076

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	30% 14% 5% 10% 7% 3 5% 5% 5% 5% 12%	2219
	11th to 20th	Day	22% 13% 5% 7% 7% 3 5% 5% 5% 5% 22%	2199
	21st to end	Day	32% 14% 6% 10% 9% 4 5% 4 4 4 8%	2919
February	1st to 10th	Day	25% 13% 5% 9% 8% 5% 4 5% 5% 5% 15%	1710
	11th to 20th	Day	24% 11% 4 9% 6% 4 6% 4 6% 5% 22%	1665
	21st to end	Day	19% 11% 3 8% 7% 5% 6% 7% 6% 6% 22%	1413
March	1st to 10th	Day	12% 12% 5% 9% 9% 5% 7% 7% 7% 8% 19%	3315
	11th to 20th	Day	14% 9% 4 7% 7% 4 4 5% 5% 6% 34%	3490
	21st to end	Day	19% 11% 4 9% 8% 3 6% 4 6% 6% 23%	3872
April	1st to 10th	Day	19% 11% 5% 8% 8% 4 6% 5% 6% 8% 20%	2280
	11th to 20th	Day	16% 10% 3 8% 7% 4 6% 6% 7% 6% 27%	2370
	21st to end	Day	16% 9% 4 7% 6% 5% 6% 6% 7% 8% 27%	2395
May	1st to 10th	Day	12% 7% 3 6% 8% 3 6% 6% 6% 7% 36%	2515
	11th to 20th	Day	11% 7% 3 7% 7% 4 5% 5% 7% 9% 33%	2477
	21st to end	Day	13% 7% 3 6% 7% 4 6% 5% 6% 8% 33%	2769
June	1st to 10th	Day	13% 8% 4 6% 7% 4 5% 6% 7% 8% 33%	2700
	11th to 20th	Day	10% 7% 3 7% 8% 5% 7% 5% 6% 9% 32%	2700
	21st to end	Day	9% 5% 2 6% 6% 4 5% 6% 6% 8% 43%	2700
July	1st to 10th	Day	8% 4 2 5% 6% 2 4 5% 5% 7% 51%	2700
	11th to 20th	Day	6% 4 2 4 4 3 5% 4 6% 8% 55%	2700
	21st to end	Day	4 2 1 3 3 2 4 4 7% 9% 61%	2794
August	1st to 10th	Day	6% 3 2 4 4 3 5% 5% 7% 8% 55%	2413
	11th to 20th	Day	4 3 2 4 4 2 5% 5% 7% 8% 57%	2298
	21st to end	Day	6% 5% 2 5% 6% 4 5% 6% 6% 10% 45%	2535
September	1st to 10th	Day	8% 4 3 5% 6% 3 5% 5% 5% 8% 48%	2160
	11th to 20th	Day	12% 7% 3 5% 6% 3 5% 6% 5% 7% 41%	2115
	21st to end	Day	15% 6% 4 5% 5% 3 5% 5% 6% 7% 40%	1923
October	1st to 10th	Day	16% 8% 3 7% 6% 3 5% 5% 6% 7% 35%	1800
	11th to 20th	Day	22% 8% 5% 7% 6% 4 6% 5% 6% 9% 23%	1800
	21st to end	Day	24% 9% 3 7% 7% 4 5% 6% 5% 6% 24%	1869
November	1st to 10th	Day	28% 11% 4 9% 7% 4 6% 5% 4 4 18%	1488
	11th to 20th	Day	25% 12% 5% 9% 7% 5% 4 5% 4 4 20%	1520
	21st to end	Day	27% 11% 5% 9% 6% 4 5% 5% 6% 4 18%	1520
December	1st to 10th	Day	20% 13% 5% 9% 8% 3 5% 5% 4 6% 23%	1511
	11th to 20th	Day	26% 13% 5% 8% 7% 4 5% 5% 5% 5% 15%	1685
	21st to end	Day	26% 14% 6% 11% 8% 5% 4 5% 5% 4 12%	2442
January	1st to 10th	Night	27% 17% 6% 11% 8% 3 5% 4 3 4 12%	4726
	11th to 20th	Night	26% 11% 5% 7% 6% 3 4 4 5% 7% 24%	4699
	21st to end	Night	35% 14% 5% 10% 7% 3 3 4 4 4 11%	4739
February	1st to 10th	Night	27% 12% 5% 8% 7% 4 5% 5% 4 5% 19%	2470
	11th to 20th	Night	21% 13% 5% 9% 7% 4 4 4 4 5% 25%	2402
	21st to end	Night	24% 12% 5% 8% 7% 3 5% 5% 5% 6% 22%	2041
March	1st to 10th	Night	15% 12% 5% 10% 8% 4 6% 6% 6% 6% 21%	3556
	11th to 20th	Night	15% 7% 3 7% 6% 3 5% 5% 6% 7% 36%	3489
	21st to end	Night	20% 13% 6% 11% 8% 4 5% 5% 5% 5% 17%	3781
April	1st to 10th	Night	20% 11% 4 7% 6% 5% 5% 6% 5% 7% 24%	1900
	11th to 20th	Night	16% 9% 4 8% 7% 4 6% 6% 7% 7% 27%	1758
	21st to end	Night	16% 10% 3 8% 7% 4 6% 5% 6% 8% 26%	1665
May	1st to 10th	Night	11% 6% 4 8% 8% 3 5% 5% 7% 7% 37%	1445
	11th to 20th	Night	11% 6% 3 8% 6% 4 7% 6% 8% 11% 29%	1416
	21st to end	Night	12% 7% 3 7% 8% 4 6% 6% 7% 9% 31%	1503
June	1st to 10th	Night	13% 7% 5% 8% 7% 5% 5% 6% 6% 7% 32%	1260
	11th to 20th	Night	11% 8% 3 7% 8% 4 8% 8% 7% 10% 26%	1260
	21st to end	Night	6% 5% 3 5% 7% 4 5% 5% 7% 11% 41%	1260
July	1st to 10th	Night	7% 5% 2 5% 7% 4 5% 6% 5% 10% 44%	1260
	11th to 20th	Night	4 4 2 4 6% 4 7% 6% 6% 9% 47%	1260
	21st to end	Night	3 2 1 3 6% 3 5% 6% 6% 11% 54%	1523
August	1st to 10th	Night	4 3 2 5% 5% 3 5% 6% 7% 10% 50%	1525
	11th to 20th	Night	4 3 1 2 4 2 4 5% 6% 10% 58%	1602
	21st to end	Night	6% 5% 3 5% 7% 4 5% 6% 9% 10% 40%	1820
September	1st to 10th	Night	6% 4 2 5% 5% 3 4 6% 6% 8% 52%	1800
	11th to 20th	Night	14% 6% 3 6% 6% 3 4 5% 6% 8% 39%	1844
	21st to end	Night	14% 6% 3 7% 6% 3 4 4 6% 6% 40%	2036
October	1st to 10th	Night	15% 7% 3 6% 7% 4 5% 5% 6% 5% 38%	2160
	11th to 20th	Night	22% 8% 3 8% 7% 3 5% 4 5% 6% 29%	2160
	21st to end	Night	24% 8% 3 7% 5% 3 5% 4 5% 5% 30%	2484
November	1st to 10th	Night	28% 11% 5% 8% 6% 4 5% 4 3 4 21%	2590
	11th to 20th	Night	27% 11% 4 9% 6% 4 4 5% 4 5% 21%	2660
	21st to end	Night	25% 10% 5% 9% 7% 3 6% 5% 4 5% 20%	2660
December	1st to 10th	Night	24% 10% 4 7% 6% 4 6% 4 5% 5% 24%	2667
	11th to 20th	Night	25% 14% 6% 9% 8% 4 5% 5% 5% 5% 13%	3520
	21st to end	Night	28% 14% 6% 11% 7% 4 5% 5% 4 5% 13%	5214

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	72% 9% 8% 9% 3	2219
	11th to 20th	Day	65% 8% 16% 8% 2	2220
	21st to end	Day	78% 8% 7% 6% 1	2919
February	1st to 10th	Day	67% 11% 11% 7% 4	1710
	11th to 20th	Day	63% 10% 10% 13% 4	1674
	21st to end	Day	61% 9% 14% 11% 5% 1	1413
March	1st to 10th	Day	53% 11% 17% 13% 5%	3315
	11th to 20th	Day	46% 8% 17% 26% 3 1	3490
	21st to end	Day	56% 11% 17% 12% 2	3872
April	1st to 10th	Day	56% 13% 16% 13% 2	2280
	11th to 20th	Day	51% 11% 13% 16% 8% 1	2370
	21st to end	Day	49% 11% 15% 19% 5% 1	2395
May	1st to 10th	Day	41% 13% 19% 21% 6% 1	2515
	11th to 20th	Day	42% 11% 22% 19% 6%	2480
	21st to end	Day	43% 11% 22% 20% 4	2770
June	1st to 10th	Day	44% 12% 20% 17% 6% 1	2700
	11th to 20th	Day	41% 14% 22% 18% 4	2700
	21st to end	Day	34% 12% 24% 20% 9% 1	2700
July	1st to 10th	Day	28% 11% 19% 28% 12% 3	2626
	11th to 20th	Day	24% 10% 22% 30% 13% 1	2619
	21st to end	Day	13% 9% 23% 38% 14% 3	2639
August	1st to 10th	Day	22% 9% 24% 31% 13% 2	2396
	11th to 20th	Day	22% 10% 24% 29% 12% 2	2298
	21st to end	Day	30% 11% 22% 30% 7% 1	2535
September	1st to 10th	Day	30% 11% 20% 24% 13% 2	2160
	11th to 20th	Day	39% 11% 15% 20% 14% 1	2115
	21st to end	Day	40% 10% 18% 21% 10% 1	1923
October	1st to 10th	Day	46% 9% 16% 21% 8%	1800
	11th to 20th	Day	55% 11% 18% 13% 4	1800
	21st to end	Day	57% 10% 13% 13% 8%	1869
November	1st to 10th	Day	66% 8% 13% 10% 2 1	1488
	11th to 20th	Day	66% 8% 9% 11% 5% 1	1520
	21st to end	Day	66% 10% 8% 12% 4	1520
December	1st to 10th	Day	62% 8% 13% 13% 4	1511
	11th to 20th	Day	70% 9% 12% 7% 2	1688
	21st to end	Day	72% 9% 11% 6% 2	2442
January	1st to 10th	Night	72% 12% 8% 6% 3	4726
	11th to 20th	Night	61% 7% 15% 14% 2 1	4740
	21st to end	Night	75% 8% 7% 8% 2	4739
February	1st to 10th	Night	66% 9% 12% 8% 5%	2470
	11th to 20th	Night	60% 8% 11% 14% 6%	2404
	21st to end	Night	61% 7% 12% 13% 6% 1	2041
March	1st to 10th	Night	55% 11% 14% 16% 5%	3556
	11th to 20th	Night	39% 12% 18% 27% 2 1	3490
	21st to end	Night	62% 9% 16% 11% 1	3781
April	1st to 10th	Night	54% 11% 17% 14% 4	1900
	11th to 20th	Night	50% 9% 14% 18% 6% 2	1758
	21st to end	Night	50% 11% 15% 16% 8% 1	1665
May	1st to 10th	Night	38% 14% 20% 19% 9% 1	1445
	11th to 20th	Night	39% 14% 20% 18% 8% 1	1416
	21st to end	Night	41% 11% 23% 20% 4	1503
June	1st to 10th	Night	44% 8% 19% 20% 6% 2	1260
	11th to 20th	Night	39% 14% 25% 19% 3	1260
	21st to end	Night	28% 12% 28% 21% 8% 3	1260
July	1st to 10th	Night	27% 11% 19% 26% 14% 3	1225
	11th to 20th	Night	21% 10% 24% 28% 16% 2	1218
	21st to end	Night	12% 9% 19% 36% 19% 4	1438
August	1st to 10th	Night	20% 11% 23% 28% 16% 3	1517
	11th to 20th	Night	16% 10% 24% 31% 14% 5%	1602
	21st to end	Night	28% 10% 20% 31% 10% 1	1820
September	1st to 10th	Night	24% 10% 18% 29% 14% 5%	1800
	11th to 20th	Night	39% 9% 15% 17% 16% 4	1844
	21st to end	Night	39% 8% 16% 22% 14% 1	2036
October	1st to 10th	Night	46% 7% 15% 21% 11% 1	2160
	11th to 20th	Night	52% 7% 18% 16% 8%	2160
	21st to end	Night	53% 8% 12% 18% 9%	2484
November	1st to 10th	Night	62% 8% 14% 11% 4	2590
	11th to 20th	Night	62% 9% 12% 10% 5% 2	2660
	21st to end	Night	65% 10% 10% 10% 6%	2660
December	1st to 10th	Night	62% 7% 13% 12% 5%	2667
	11th to 20th	Night	71% 10% 12% 4 3	3516
	21st to end	Night	69% 10% 11% 7% 3	5214

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	31% 21% 24% 16% 8% 2	180
	11th to 20th	Day	35% 13% 25% 17% 9% 1	180
	21st to end	Day	32% 14% 25% 21% 8% 1	293
February	1st to 10th	Day	32% 16% 25% 20% 5% 1	370
	11th to 20th	Day	29% 17% 25% 23% 6%	365
	21st to end	Day	21% 21% 27% 22% 7% 1	307
March	1st to 10th	Day	19% 14% 30% 24% 11% 1	458
	11th to 20th	Day	22% 13% 26% 22% 14% 3	460
	21st to end	Day	22% 13% 29% 25% 11% 1	506
April	1st to 10th	Day	20% 17% 26% 23% 12% 2	460
	11th to 20th	Day	18% 11% 31% 23% 13% 4	452
	21st to end	Day	19% 12% 27% 29% 12% 2	437
May	1st to 10th	Day	13% 9% 26% 31% 19% 2	423
	11th to 20th	Day	14% 6% 21% 31% 24% 4	448
	21st to end	Day	12% 6% 26% 31% 19% 6%	531
June	1st to 10th	Day	15% 8% 29% 29% 17% 2	630
	11th to 20th	Day	10% 10% 35% 31% 12% 2	630
	21st to end	Day	9% 5% 26% 31% 24% 5%	630
July	1st to 10th	Day	10% 4 19% 34% 30% 3	621
	11th to 20th	Day	4 4 22% 36% 27% 6%	618
	21st to end	Day	3 1 18% 32% 36% 10%	540
August	1st to 10th	Day	5% 4 15% 27% 36% 12%	447
	11th to 20th	Day	4 1 13% 33% 38% 12%	437
	21st to end	Day	8% 4 18% 36% 27% 7%	495
September	1st to 10th	Day	12% 3 20% 37% 24% 4	450
	11th to 20th	Day	14% 6% 19% 27% 27% 7%	450
	21st to end	Day	16% 5% 23% 27% 25% 3	450
October	1st to 10th	Day	20% 6% 19% 26% 23% 5%	450
	11th to 20th	Day	28% 10% 18% 23% 19% 3	450
	21st to end	Day	23% 18% 26% 21% 10% 3	409
November	1st to 10th	Day	28% 17% 25% 24% 6%	180
	11th to 20th	Day	29% 9% 24% 24% 12% 2	180
	21st to end	Day	32% 13% 27% 11% 12% 4	180
December	1st to 10th	Day	27% 16% 21% 21% 14% 1	180
	11th to 20th	Day	35% 14% 23% 19% 8% 1	180
	21st to end	Day	36% 15% 25% 20% 4	198
January	1st to 10th	Night	37% 14% 21% 19% 9% 1	850
	11th to 20th	Night	32% 12% 17% 25% 14%	850
	21st to end	Night	32% 10% 20% 23% 14% 1	845
February	1st to 10th	Night	30% 14% 21% 24% 9% 2	760
	11th to 20th	Night	27% 12% 21% 27% 12% 1	744
	21st to end	Night	28% 15% 22% 20% 11% 3	628
March	1st to 10th	Night	24% 10% 21% 26% 16% 3	760
	11th to 20th	Night	25% 12% 23% 22% 15% 3	760
	21st to end	Night	27% 9% 22% 25% 14% 3	836
April	1st to 10th	Night	25% 9% 22% 25% 16% 3	760
	11th to 20th	Night	18% 9% 23% 32% 15% 3	630
	21st to end	Night	21% 8% 24% 30% 15% 3	555
May	1st to 10th	Night	14% 6% 18% 35% 23% 4	365
	11th to 20th	Night	14% 5% 16% 30% 29% 6%	354
	21st to end	Night	13% 4 19% 37% 24% 3	389
June	1st to 10th	Night	17% 6% 21% 28% 26% 2	360
	11th to 20th	Night	14% 4 29% 33% 17% 3	360
	21st to end	Night	9% 4 21% 31% 30% 6%	360
July	1st to 10th	Night	6% 1 19% 33% 35% 6%	350
	11th to 20th	Night	4 2 17% 37% 33% 7%	348
	21st to end	Night	2 1 13% 32% 41% 11%	394
August	1st to 10th	Night	5% 2 11% 27% 39% 16%	451
	11th to 20th	Night	5% 7% 25% 46% 17%	534
	21st to end	Night	10% 1 17% 31% 33% 8%	632
September	1st to 10th	Night	8% 2 13% 34% 32% 11%	720
	11th to 20th	Night	14% 3 14% 25% 29% 15%	720
	21st to end	Night	16% 4 18% 29% 25% 8%	720
October	1st to 10th	Night	20% 4 14% 24% 29% 9%	720
	11th to 20th	Night	27% 6% 13% 26% 21% 9%	720
	21st to end	Night	29% 8% 19% 25% 16% 3	792
November	1st to 10th	Night	33% 9% 23% 24% 11%	740
	11th to 20th	Night	34% 11% 21% 20% 12% 1	760
	21st to end	Night	31% 9% 22% 24% 12% 2	760
December	1st to 10th	Night	29% 10% 20% 25% 15% 1	764
	11th to 20th	Night	35% 13% 23% 21% 8% 1	850
	21st to end	Night	32% 16% 27% 20% 5%	935

Page generated at 2024-04-22 06:25:44. Version ac07

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