Carnation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carnation clear sky chart from 2005-11-06 to 2024-10-24.

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	23% 9% 3 7% 5% 4 4 3 5% 6% 32%	101999
	Night	27% 10% 3 7% 4 4 4 3 4 5% 30%	96785
Transparency	Day	55% 6% 13% 17% 8% 2	101758
	Night	58% 6% 12% 15% 7% 1	96672
Seeing	Day	28% 9% 19% 26% 14% 3	14973
	Night	33% 6% 13% 26% 18% 2	23292

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	43% 16% 3 8% 4 3 3 3 3 4 11%	2419
	11th to 20th	Day	28% 13% 3 9% 5% 4 3 3 4 6% 22%	2516
	21st to end	Day	45% 12% 4 8% 4 3 3 2 3 4 13%	2835
February	1st to 10th	Day	34% 12% 3 8% 6% 5% 4 3 4 5% 16%	1710
	11th to 20th	Day	32% 13% 4 8% 4 4 4 3 4 4 19%	1665
	21st to end	Day	30% 16% 4 8% 5% 4 3 2 4 4 19%	1493
March	1st to 10th	Day	22% 15% 4 9% 6% 5% 5% 4 5% 5% 21%	3186
	11th to 20th	Day	22% 11% 3 6% 4 3 4 3 3 4 36%	3490
	21st to end	Day	28% 14% 4 9% 6% 5% 4 4 5% 5% 15%	3974
April	1st to 10th	Day	28% 14% 3 9% 6% 5% 5% 4 5% 5% 16%	2280
	11th to 20th	Day	24% 12% 4 8% 7% 4 5% 4 4 5% 24%	2256
	21st to end	Day	26% 11% 3 10% 6% 5% 5% 4 5% 5% 20%	2532
May	1st to 10th	Day	21% 9% 3 6% 5% 4 4 4 5% 5% 35%	4420
	11th to 20th	Day	21% 7% 2 6% 4 3 4 3 5% 9% 35%	4377
	21st to end	Day	33% 11% 3 8% 6% 4 4 3 4 6% 19%	4813
June	1st to 10th	Day	26% 9% 2 7% 5% 5% 5% 4 5% 6% 25%	2662
	11th to 20th	Day	28% 10% 3 8% 6% 5% 6% 4 5% 6% 20%	2850
	21st to end	Day	14% 7% 3 8% 5% 4 5% 4 6% 6% 37%	2850
July	1st to 10th	Day	9% 4 1 5% 3 2 3 3 4 5% 62%	4740
	11th to 20th	Day	7% 4 1 4 3 3 2 3 4 5% 65%	4462
	21st to end	Day	14% 5% 1 4 3 2 3 3 4 6% 56%	4790
August	1st to 10th	Day	7% 3 1 3 3 3 3 3 5% 7% 60%	4358
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 7% 8% 38%	4026
	21st to end	Day	18% 7% 3 7% 4 4 4 3 4 7% 41%	4309
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 49%	2280
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 37%	2280
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 5% 38%	2017
October	1st to 10th	Day	21% 9% 3 6% 3 4 5% 4 6% 6% 31%	1900
	11th to 20th	Day	29% 8% 3 7% 4 4 4 3 4 7% 27%	1900
	21st to end	Day	34% 7% 2 7% 4 3 5% 3 5% 6% 23%	1885
November	1st to 10th	Day	40% 9% 3 6% 4 4 4 5% 4 4 18%	1547
	11th to 20th	Day	37% 10% 3 7% 4 4 4 3 4 4 21%	1520
	21st to end	Day	36% 11% 3 6% 5% 3 4 3 4 4 21%	1520
December	1st to 10th	Day	32% 11% 3 7% 5% 4 3 3 4 4 23%	1520
	11th to 20th	Day	34% 13% 3 7% 5% 4 4 3 4 4 19%	1925
	21st to end	Day	31% 12% 4 9% 6% 5% 4 3 4 4 16%	2692
January	1st to 10th	Night	44% 14% 3 7% 4 4 4 2 3 4 11%	4494
	11th to 20th	Night	31% 12% 4 7% 4 3 3 3 4 7% 23%	4382
	21st to end	Night	41% 11% 3 8% 5% 4 4 3 3 5% 14%	4819
February	1st to 10th	Night	35% 11% 4 7% 4 4 4 3 4 5% 18%	2470
	11th to 20th	Night	31% 13% 3 7% 4 4 3 3 3 5% 22%	2402
	21st to end	Night	33% 15% 3 7% 4 3 3 4 4 5% 19%	1960
March	1st to 10th	Night	21% 16% 3 8% 6% 5% 5% 5% 5% 7% 19%	3686
	11th to 20th	Night	23% 9% 2 6% 3 3 3 2 3 6% 39%	3489
	21st to end	Night	34% 14% 3 8% 4 4 4 4 5% 4 16%	3679
April	1st to 10th	Night	28% 12% 3 8% 5% 4 4 5% 6% 6% 18%	1900
	11th to 20th	Night	23% 11% 4 8% 5% 4 4 3 5% 5% 27%	1874
	21st to end	Night	29% 10% 3 7% 5% 4 4 3 5% 7% 22%	1648
May	1st to 10th	Night	23% 9% 2 7% 4 3 3 2 3 4 39%	2540
	11th to 20th	Night	21% 9% 3 6% 4 4 3 3 4 7% 37%	2516
	21st to end	Night	33% 12% 4 9% 5% 4 4 2 4 4 19%	2762
June	1st to 10th	Night	23% 9% 3 8% 6% 4 4 4 5% 5% 30%	1513
	11th to 20th	Night	27% 10% 3 9% 6% 4 5% 3 4 5% 24%	1330
	21st to end	Night	14% 7% 2 7% 5% 4 4 4 5% 6% 42%	1330
July	1st to 10th	Night	11% 5% 2 5% 3 2 2 2 3 3 61%	2220
	11th to 20th	Night	6% 3 1 3 3 2 2 2 3 4 72%	2494
	21st to end	Night	14% 6% 2 3 3 2 3 2 3 6% 56%	2762
August	1st to 10th	Night	5% 3 1 3 2 2 3 3 4 6% 67%	2558
	11th to 20th	Night	15% 8% 3 6% 4 3 3 2 4 5% 47%	2812
	21st to end	Night	19% 8% 2 6% 3 2 3 2 3 4 47%	3365
September	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 53%	1900
	11th to 20th	Night	20% 8% 2 7% 3 3 4 3 4 5% 41%	1900
	21st to end	Night	20% 7% 2 7% 4 4 4 3 4 5% 40%	2161
October	1st to 10th	Night	22% 7% 3 6% 5% 3 4 3 5% 6% 37%	2280
	11th to 20th	Night	28% 8% 2 6% 4 4 3 4 5% 4 31%	2280
	21st to end	Night	32% 9% 2 7% 4 3 3 3 4 6% 28%	2538
November	1st to 10th	Night	36% 11% 2 6% 4 4 4 3 5% 5% 20%	2529
	11th to 20th	Night	36% 10% 3 7% 5% 3 3 2 4 4 22%	2660
	21st to end	Night	34% 11% 3 7% 4 4 4 3 3 5% 22%	2660
December	1st to 10th	Night	32% 11% 3 6% 5% 4 3 3 4 5% 24%	2660
	11th to 20th	Night	33% 13% 4 9% 5% 4 3 3 4 5% 18%	3280
	21st to end	Night	31% 14% 4 9% 6% 5% 5% 3 4 4 15%	4932

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	80% 4 6% 7% 3 1	2419
	11th to 20th	Day	64% 5% 10% 13% 6% 1	2540
	21st to end	Day	77% 5% 7% 8% 3	2835
February	1st to 10th	Day	72% 7% 9% 8% 3 1	1710
	11th to 20th	Day	70% 5% 9% 8% 6% 1	1674
	21st to end	Day	71% 4 10% 11% 4	1493
March	1st to 10th	Day	63% 6% 15% 12% 3	3186
	11th to 20th	Day	54% 5% 15% 24% 2 1	3490
	21st to end	Day	72% 7% 12% 8% 1	3974
April	1st to 10th	Day	71% 7% 14% 7% 1	2280
	11th to 20th	Day	65% 6% 12% 11% 5% 1	2256
	21st to end	Day	69% 6% 11% 9% 4 1	2532
May	1st to 10th	Day	53% 5% 16% 18% 9%	4420
	11th to 20th	Day	49% 7% 25% 16% 3	4380
	21st to end	Day	70% 8% 14% 8%	4814
June	1st to 10th	Day	62% 7% 16% 10% 5%	2662
	11th to 20th	Day	67% 6% 14% 10% 2	2850
	21st to end	Day	47% 8% 18% 18% 7% 1	2850
July	1st to 10th	Day	27% 6% 10% 21% 23% 14%	4666
	11th to 20th	Day	23% 4 8% 29% 33% 3	4385
	21st to end	Day	30% 6% 15% 33% 14% 2	4639
August	1st to 10th	Day	23% 6% 13% 39% 16% 1	4341
	11th to 20th	Day	42% 11% 19% 20% 7% 1	4065
	21st to end	Day	45% 4 13% 27% 10% 1	4308
September	1st to 10th	Day	36% 7% 15% 25% 13% 5%	2280
	11th to 20th	Day	48% 6% 12% 17% 14% 2	2280
	21st to end	Day	49% 6% 16% 17% 9% 3	2017
October	1st to 10th	Day	52% 7% 11% 22% 6% 1	1900
	11th to 20th	Day	58% 5% 13% 17% 6% 1	1900
	21st to end	Day	63% 5% 10% 12% 10%	1885
November	1st to 10th	Day	70% 5% 12% 10% 4	1547
	11th to 20th	Day	70% 5% 9% 8% 7% 2	1520
	21st to end	Day	70% 5% 5% 11% 7% 2	1520
December	1st to 10th	Day	65% 6% 8% 12% 8% 1	1520
	11th to 20th	Day	71% 5% 11% 11% 2 1	1928
	21st to end	Day	71% 7% 10% 9% 3	2692
January	1st to 10th	Night	79% 5% 6% 6% 3 1	4494
	11th to 20th	Night	63% 4 10% 15% 6% 1	4420
	21st to end	Night	75% 5% 8% 8% 4 1	4819
February	1st to 10th	Night	71% 5% 10% 9% 4 1	2470
	11th to 20th	Night	66% 7% 10% 9% 6% 1	2404
	21st to end	Night	70% 4 10% 11% 4	1960
March	1st to 10th	Night	63% 7% 16% 10% 4	3686
	11th to 20th	Night	50% 5% 20% 22% 2 1	3490
	21st to end	Night	72% 7% 13% 8% 1	3679
April	1st to 10th	Night	68% 8% 12% 10% 1	1900
	11th to 20th	Night	60% 7% 13% 11% 8% 1	1874
	21st to end	Night	66% 7% 11% 11% 5% 1	1648
May	1st to 10th	Night	51% 4 14% 23% 7%	2540
	11th to 20th	Night	50% 6% 21% 19% 3 1	2516
	21st to end	Night	71% 8% 13% 8% 1	2762
June	1st to 10th	Night	60% 5% 16% 14% 5%	1513
	11th to 20th	Night	64% 7% 15% 11% 2	1330
	21st to end	Night	45% 8% 20% 19% 6% 2	1330
July	1st to 10th	Night	30% 6% 10% 18% 17% 19%	2185
	11th to 20th	Night	21% 2 10% 27% 39% 1	2448
	21st to end	Night	31% 6% 14% 28% 19% 2	2674
August	1st to 10th	Night	19% 5% 13% 41% 21% 2	2550
	11th to 20th	Night	40% 10% 18% 21% 8% 2	2839
	21st to end	Night	43% 4 14% 30% 9%	3365
September	1st to 10th	Night	34% 6% 15% 26% 14% 4	1900
	11th to 20th	Night	48% 6% 11% 17% 14% 3	1900
	21st to end	Night	47% 7% 16% 18% 11% 2	2161
October	1st to 10th	Night	49% 6% 14% 23% 7% 1	2280
	11th to 20th	Night	57% 5% 12% 18% 7% 1	2280
	21st to end	Night	60% 6% 11% 13% 10%	2538
November	1st to 10th	Night	68% 5% 13% 10% 4 1	2529
	11th to 20th	Night	69% 4 10% 10% 5% 3	2660
	21st to end	Night	68% 5% 6% 10% 9% 1	2660
December	1st to 10th	Night	66% 5% 9% 11% 8% 1	2660
	11th to 20th	Night	71% 6% 9% 11% 3 1	3276
	21st to end	Night	72% 6% 11% 7% 3	4932

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	44% 8% 15% 18% 11% 5%	180
	11th to 20th	Day	38% 14% 10% 22% 15% 2	180
	21st to end	Day	51% 8% 13% 13% 12% 3	226
February	1st to 10th	Day	43% 11% 19% 18% 9% 1	370
	11th to 20th	Day	46% 10% 19% 17% 8% 1	365
	21st to end	Day	38% 12% 20% 23% 7% 1	346
March	1st to 10th	Day	37% 14% 20% 19% 9% 1	460
	11th to 20th	Day	33% 13% 17% 23% 11% 3	460
	21st to end	Day	40% 12% 24% 15% 7% 1	506
April	1st to 10th	Day	37% 10% 23% 17% 10% 2	460
	11th to 20th	Day	30% 17% 25% 16% 9% 3	452
	21st to end	Day	32% 12% 26% 21% 9% 1	460
May	1st to 10th	Day	24% 10% 27% 27% 11% 2	463
	11th to 20th	Day	30% 9% 19% 23% 14% 4	488
	21st to end	Day	32% 9% 21% 25% 11% 3	529
June	1st to 10th	Day	28% 9% 22% 27% 12% 3	492
	11th to 20th	Day	30% 12% 23% 24% 10% 1	680
	21st to end	Day	17% 6% 21% 36% 17% 3	680
July	1st to 10th	Day	15% 5% 20% 38% 20% 2	671
	11th to 20th	Day	12% 7% 18% 39% 21% 4	511
	21st to end	Day	11% 4 18% 40% 23% 5%	531
August	1st to 10th	Day	13% 5% 15% 39% 21% 8%	487
	11th to 20th	Day	8% 5% 16% 38% 26% 6%	477
	21st to end	Day	18% 8% 19% 34% 16% 6%	539
September	1st to 10th	Day	15% 9% 22% 35% 16% 3	490
	11th to 20th	Day	21% 8% 17% 33% 19% 2	490
	21st to end	Day	23% 6% 22% 27% 19% 3	490
October	1st to 10th	Day	25% 9% 20% 22% 20% 4	490
	11th to 20th	Day	37% 6% 15% 23% 14% 5%	490
	21st to end	Day	37% 10% 18% 21% 9% 4	382
November	1st to 10th	Day	40% 12% 16% 22% 10%	210
	11th to 20th	Day	46% 11% 8% 12% 19% 4	180
	21st to end	Day	41% 8% 13% 17% 13% 8%	180
December	1st to 10th	Day	46% 8% 10% 15% 12% 8%	180
	11th to 20th	Day	43% 12% 16% 21% 9%	180
	21st to end	Day	43% 7% 14% 22% 12% 1	198
January	1st to 10th	Night	50% 8% 13% 17% 11% 1	782
	11th to 20th	Night	42% 9% 14% 22% 12% 2	760
	21st to end	Night	41% 6% 13% 28% 12%	836
February	1st to 10th	Night	42% 7% 17% 25% 9% 1	760
	11th to 20th	Night	40% 8% 12% 29% 12% 1	744
	21st to end	Night	41% 9% 15% 25% 9% 1	628
March	1st to 10th	Night	36% 8% 16% 25% 14% 1	760
	11th to 20th	Night	35% 8% 17% 27% 11% 1	760
	21st to end	Night	40% 8% 16% 25% 8% 2	836
April	1st to 10th	Night	36% 8% 15% 26% 13% 2	760
	11th to 20th	Night	30% 8% 18% 29% 14% 2	746
	21st to end	Night	35% 7% 15% 28% 13% 2	508
May	1st to 10th	Night	26% 8% 13% 33% 19% 1	380
	11th to 20th	Night	28% 5% 10% 28% 25% 4	374
	21st to end	Night	30% 5% 14% 24% 24% 3	411
June	1st to 10th	Night	28% 5% 11% 31% 22% 2	380
	11th to 20th	Night	35% 5% 13% 25% 20% 1	380
	21st to end	Night	19% 3 12% 31% 32% 4	380
July	1st to 10th	Night	16% 5% 8% 30% 36% 4	370
	11th to 20th	Night	13% 2 7% 34% 39% 5%	368
	21st to end	Night	10% 4 7% 27% 46% 6%	416
August	1st to 10th	Night	12% 2 5% 25% 49% 7%	394
	11th to 20th	Night	11% 3 5% 26% 44% 11%	564
	21st to end	Night	20% 3 8% 28% 36% 5%	755
September	1st to 10th	Night	15% 3 8% 36% 33% 5%	760
	11th to 20th	Night	23% 4 9% 26% 32% 6%	760
	21st to end	Night	25% 5% 11% 28% 28% 3	760
October	1st to 10th	Night	27% 5% 11% 31% 24% 3	760
	11th to 20th	Night	33% 6% 13% 26% 18% 3	760
	21st to end	Night	38% 9% 15% 25% 12% 2	804
November	1st to 10th	Night	42% 8% 16% 27% 7%	740
	11th to 20th	Night	43% 7% 16% 24% 9% 1	760
	21st to end	Night	41% 8% 14% 24% 13% 1	760
December	1st to 10th	Night	38% 7% 15% 26% 12% 2	760
	11th to 20th	Night	46% 8% 17% 23% 5% 1	760
	21st to end	Night	50% 9% 15% 21% 5%	856

Page generated at 2024-10-20 23:20:03. Version ac07

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