Dome Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dome Creek clear sky chart from 2005-11-06 to 2025-02-06.

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% 13% 4 10% 6% 6% 6% 4 6% 7% 28%	111369
	Night	11% 16% 5% 11% 6% 6% 5% 4 5% 6% 24%	115500
Transparency	Day	53% 10% 15% 15% 6% 1	111101
	Night	55% 11% 15% 15% 5% 1	115414
Seeing	Day	19% 10% 22% 27% 16% 5%	16576
	Night	23% 9% 20% 31% 15% 1	24796

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% 19% 6% 15% 9% 8% 6% 4 4 6% 15%	2783
	11th to 20th	Day	8% 17% 5% 12% 6% 5% 5% 4 6% 6% 24%	3159
	21st to end	Day	10% 17% 6% 13% 7% 7% 6% 4 6% 7% 19%	3618
February	1st to 10th	Day	9% 22% 7% 12% 6% 4 4 3 4 6% 22%	1560
	11th to 20th	Day	8% 20% 7% 14% 7% 5% 5% 3 4 5% 22%	1650
	21st to end	Day	4 18% 6% 15% 7% 6% 4 4 4 6% 25%	1440
March	1st to 10th	Day	3 16% 7% 14% 8% 6% 5% 4 5% 7% 26%	3138
	11th to 20th	Day	4 16% 5% 11% 7% 7% 7% 5% 6% 7% 25%	3397
	21st to end	Day	6% 16% 5% 9% 6% 5% 5% 4 6% 6% 32%	4062
April	1st to 10th	Day	6% 15% 6% 13% 8% 8% 7% 6% 6% 7% 18%	2280
	11th to 20th	Day	9% 14% 4 11% 7% 7% 6% 5% 6% 7% 24%	2395
	21st to end	Day	10% 15% 4 12% 6% 6% 6% 4 7% 6% 24%	2660
May	1st to 10th	Day	8% 12% 4 11% 7% 6% 6% 5% 7% 8% 28%	4420
	11th to 20th	Day	12% 12% 4 10% 7% 7% 7% 5% 7% 7% 23%	4460
	21st to end	Day	16% 15% 5% 11% 6% 6% 6% 4 6% 6% 18%	5509
June	1st to 10th	Day	14% 9% 4 10% 6% 7% 6% 6% 6% 7% 25%	3040
	11th to 20th	Day	19% 11% 4 9% 7% 7% 6% 5% 6% 7% 18%	3040
	21st to end	Day	15% 9% 4 9% 7% 6% 5% 4 6% 7% 27%	3040
July	1st to 10th	Day	13% 5% 2 5% 4 4 5% 4 5% 7% 46%	5060
	11th to 20th	Day	8% 5% 2 5% 4 5% 4 4 6% 8% 48%	4916
	21st to end	Day	14% 6% 3 8% 7% 6% 6% 5% 6% 8% 32%	5112
August	1st to 10th	Day	7% 5% 1 6% 5% 4 4 4 6% 8% 51%	4401
	11th to 20th	Day	10% 5% 2 7% 4 5% 5% 4 6% 9% 43%	4330
	21st to end	Day	17% 7% 3 8% 5% 6% 6% 4 5% 9% 29%	4471
September	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 4 5% 7% 32%	2280
	11th to 20th	Day	14% 10% 3 7% 6% 6% 5% 4 6% 7% 33%	2280
	21st to end	Day	20% 13% 3 9% 5% 5% 5% 4 5% 7% 23%	2023
October	1st to 10th	Day	15% 13% 4 11% 6% 6% 6% 4 5% 7% 22%	3180
	11th to 20th	Day	17% 15% 5% 9% 6% 5% 5% 4 5% 6% 24%	3046
	21st to end	Day	11% 13% 4 8% 8% 7% 7% 4 6% 6% 26%	2977
November	1st to 10th	Day	17% 21% 6% 11% 6% 5% 4 3 5% 5% 17%	1568
	11th to 20th	Day	9% 23% 8% 13% 7% 5% 5% 4 5% 5% 17%	1500
	21st to end	Day	11% 22% 7% 12% 8% 5% 4 3 6% 4 16%	1360
December	1st to 10th	Day	19% 18% 6% 13% 8% 6% 4 4 5% 5% 12%	1960
	11th to 20th	Day	8% 21% 6% 13% 7% 7% 6% 4 4 6% 17%	2262
	21st to end	Day	6% 18% 7% 12% 6% 5% 5% 4 7% 8% 22%	2992
January	1st to 10th	Night	8% 21% 7% 14% 8% 7% 6% 4 6% 7% 13%	7208
	11th to 20th	Night	10% 19% 5% 11% 6% 6% 6% 4 5% 5% 23%	6739
	21st to end	Night	14% 20% 6% 12% 6% 5% 4 3 4 5% 20%	7324
February	1st to 10th	Night	10% 23% 6% 13% 7% 5% 4 3 4 5% 20%	2730
	11th to 20th	Night	10% 20% 7% 12% 6% 5% 4 4 5% 6% 22%	2414
	21st to end	Night	5% 20% 6% 11% 8% 5% 5% 3 5% 6% 26%	2013
March	1st to 10th	Night	5% 13% 5% 13% 8% 7% 6% 5% 6% 7% 24%	3736
	11th to 20th	Night	8% 17% 5% 11% 7% 7% 7% 4 6% 8% 20%	3582
	21st to end	Night	5% 13% 5% 9% 6% 5% 5% 4 6% 7% 35%	3591
April	1st to 10th	Night	8% 15% 6% 12% 6% 5% 7% 5% 7% 5% 24%	1900
	11th to 20th	Night	9% 13% 4 8% 6% 6% 7% 5% 8% 7% 27%	1734
	21st to end	Night	13% 15% 4 9% 6% 5% 5% 4 6% 7% 26%	1520
May	1st to 10th	Night	11% 10% 4 8% 6% 7% 7% 4 7% 7% 29%	2540
	11th to 20th	Night	15% 12% 4 9% 5% 5% 5% 5% 7% 8% 26%	2418
	21st to end	Night	19% 15% 5% 9% 6% 4 5% 4 5% 6% 22%	2066
June	1st to 10th	Night	11% 9% 3 9% 6% 6% 6% 5% 7% 8% 30%	1140
	11th to 20th	Night	19% 11% 3 10% 5% 6% 5% 4 6% 9% 23%	1140
	21st to end	Night	15% 8% 3 6% 7% 5% 5% 5% 6% 8% 31%	1140
July	1st to 10th	Night	11% 5% 2 6% 3 4 5% 3 5% 6% 50%	1900
	11th to 20th	Night	8% 5% 2 5% 4 5% 5% 3 5% 7% 50%	2028
	21st to end	Night	18% 8% 3 8% 6% 4 5% 4 7% 7% 31%	2440
August	1st to 10th	Night	7% 5% 2 6% 4 3 4 3 5% 8% 53%	2529
	11th to 20th	Night	9% 6% 2 6% 5% 5% 5% 4 6% 7% 46%	2497
	21st to end	Night	18% 7% 3 8% 5% 5% 5% 5% 7% 7% 31%	3195
September	1st to 10th	Night	17% 9% 4 7% 5% 4 4 4 6% 7% 33%	1900
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 5% 7% 39%	1900
	21st to end	Night	22% 11% 3 9% 5% 5% 4 3 5% 5% 29%	2154
October	1st to 10th	Night	17% 13% 4 11% 7% 6% 5% 4 6% 6% 22%	3800
	11th to 20th	Night	16% 10% 3 8% 5% 5% 7% 5% 7% 8% 26%	3887
	21st to end	Night	12% 16% 4 10% 7% 7% 6% 5% 6% 7% 20%	4577
November	1st to 10th	Night	17% 21% 5% 11% 6% 6% 4 3 4 5% 16%	2730
	11th to 20th	Night	12% 22% 8% 13% 7% 5% 5% 4 4 4 16%	2878
	21st to end	Night	11% 24% 7% 13% 8% 6% 5% 3 4 4 15%	3036
December	1st to 10th	Night	15% 20% 6% 14% 7% 6% 5% 4 5% 5% 13%	5220
	11th to 20th	Night	9% 25% 7% 12% 7% 6% 5% 4 5% 5% 15%	5930
	21st to end	Night	5% 19% 8% 12% 7% 5% 6% 4 5% 7% 22%	7964

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	63% 11% 15% 7% 4	2783
	11th to 20th	Day	53% 11% 13% 10% 9% 4	3180
	21st to end	Day	57% 15% 18% 9% 2	3618
February	1st to 10th	Day	64% 7% 9% 9% 11% 1	1560
	11th to 20th	Day	65% 8% 11% 8% 6% 1	1659
	21st to end	Day	62% 5% 12% 11% 7% 2	1440
March	1st to 10th	Day	53% 10% 11% 15% 11% 1	3138
	11th to 20th	Day	53% 13% 12% 19% 3	3397
	21st to end	Day	51% 11% 12% 15% 12%	4062
April	1st to 10th	Day	63% 11% 13% 10% 3	2280
	11th to 20th	Day	58% 8% 14% 16% 4	2395
	21st to end	Day	58% 10% 14% 14% 4	2660
May	1st to 10th	Day	52% 8% 19% 18% 3	4420
	11th to 20th	Day	55% 11% 14% 14% 5%	4463
	21st to end	Day	63% 11% 13% 10% 2	5510
June	1st to 10th	Day	56% 11% 13% 14% 6%	3040
	11th to 20th	Day	63% 11% 13% 12% 2	3040
	21st to end	Day	56% 9% 16% 14% 5%	3040
July	1st to 10th	Day	37% 8% 11% 21% 19% 3	4981
	11th to 20th	Day	33% 8% 16% 31% 10% 1	4829
	21st to end	Day	46% 11% 16% 15% 10% 2	4950
August	1st to 10th	Day	30% 10% 16% 33% 11%	4384
	11th to 20th	Day	37% 10% 21% 24% 8% 1	4372
	21st to end	Day	50% 10% 22% 15% 3	4470
September	1st to 10th	Day	50% 11% 16% 16% 6% 1	2280
	11th to 20th	Day	50% 10% 17% 18% 6%	2280
	21st to end	Day	59% 10% 13% 12% 5% 1	2023
October	1st to 10th	Day	55% 12% 19% 11% 3	3180
	11th to 20th	Day	56% 9% 20% 14% 1	3046
	21st to end	Day	52% 9% 26% 11% 2	2977
November	1st to 10th	Day	67% 9% 9% 12% 3 1	1568
	11th to 20th	Day	66% 11% 11% 8% 3 1	1500
	21st to end	Day	68% 10% 9% 6% 5% 1	1360
December	1st to 10th	Day	68% 13% 10% 7% 2	1960
	11th to 20th	Day	63% 9% 13% 10% 4	2264
	21st to end	Day	52% 11% 21% 13% 3	2992
January	1st to 10th	Night	62% 12% 14% 9% 4	7208
	11th to 20th	Night	60% 7% 13% 8% 8% 4	6780
	21st to end	Night	61% 12% 14% 10% 2	7324
February	1st to 10th	Night	66% 7% 9% 10% 8%	2730
	11th to 20th	Night	63% 8% 12% 12% 5%	2416
	21st to end	Night	59% 7% 12% 14% 7% 1	2013
March	1st to 10th	Night	52% 12% 11% 16% 8% 1	3736
	11th to 20th	Night	56% 11% 12% 16% 5%	3583
	21st to end	Night	45% 10% 13% 20% 12%	3591
April	1st to 10th	Night	57% 12% 11% 15% 5%	1900
	11th to 20th	Night	52% 10% 14% 18% 6%	1734
	21st to end	Night	57% 9% 9% 20% 5%	1520
May	1st to 10th	Night	50% 10% 16% 18% 5%	2540
	11th to 20th	Night	50% 11% 16% 17% 6%	2418
	21st to end	Night	61% 11% 12% 14% 2	2066
June	1st to 10th	Night	48% 12% 16% 16% 8%	1140
	11th to 20th	Night	57% 13% 13% 16% 2	1140
	21st to end	Night	48% 12% 19% 18% 3	1140
July	1st to 10th	Night	34% 8% 13% 24% 16% 5%	1870
	11th to 20th	Night	32% 7% 15% 39% 7%	1992
	21st to end	Night	45% 10% 19% 18% 8%	2363
August	1st to 10th	Night	28% 7% 20% 36% 8%	2521
	11th to 20th	Night	34% 10% 17% 33% 5%	2521
	21st to end	Night	46% 11% 26% 13% 3 1	3195
September	1st to 10th	Night	49% 10% 15% 20% 5% 2	1900
	11th to 20th	Night	44% 8% 15% 25% 7%	1900
	21st to end	Night	55% 10% 13% 14% 7%	2154
October	1st to 10th	Night	54% 12% 18% 13% 3	3800
	11th to 20th	Night	46% 10% 22% 20% 2	3887
	21st to end	Night	53% 12% 21% 11% 3	4577
November	1st to 10th	Night	68% 10% 9% 10% 4	2730
	11th to 20th	Night	67% 11% 10% 8% 4	2878
	21st to end	Night	70% 10% 8% 7% 5% 1	3036
December	1st to 10th	Night	63% 16% 12% 7% 3	5220
	11th to 20th	Night	65% 11% 13% 9% 2	5927
	21st to end	Night	54% 11% 18% 15% 2	7964

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	17% 12% 17% 34% 16% 5%	200
	11th to 20th	Day	21% 10% 27% 23% 18% 3	200
	21st to end	Day	24% 10% 20% 30% 13% 4	220
February	1st to 10th	Day	25% 15% 19% 27% 12% 2	190
	11th to 20th	Day	21% 15% 23% 26% 11% 5%	350
	21st to end	Day	16% 15% 32% 22% 11% 3	321
March	1st to 10th	Day	15% 14% 25% 27% 16% 3	460
	11th to 20th	Day	15% 17% 27% 25% 13% 4	460
	21st to end	Day	21% 15% 23% 24% 12% 5%	506
April	1st to 10th	Day	17% 15% 31% 25% 10% 3	460
	11th to 20th	Day	15% 16% 25% 27% 11% 6%	452
	21st to end	Day	17% 13% 25% 26% 13% 5%	460
May	1st to 10th	Day	17% 9% 26% 26% 19% 3	463
	11th to 20th	Day	16% 5% 22% 32% 21% 5%	531
	21st to end	Day	18% 8% 19% 32% 20% 3	940
June	1st to 10th	Day	19% 10% 26% 30% 14% 1	870
	11th to 20th	Day	24% 9% 21% 28% 15% 3	870
	21st to end	Day	20% 8% 21% 26% 21% 5%	870
July	1st to 10th	Day	17% 8% 18% 32% 22% 4	856
	11th to 20th	Day	17% 8% 19% 29% 23% 5%	773
	21st to end	Day	13% 8% 21% 32% 19% 6%	725
August	1st to 10th	Day	10% 8% 20% 29% 25% 8%	487
	11th to 20th	Day	16% 8% 25% 27% 18% 6%	477
	21st to end	Day	18% 9% 25% 26% 14% 8%	539
September	1st to 10th	Day	19% 10% 20% 26% 18% 7%	490
	11th to 20th	Day	21% 6% 18% 31% 16% 7%	490
	21st to end	Day	29% 13% 23% 20% 12% 3	490
October	1st to 10th	Day	27% 12% 17% 21% 18% 5%	490
	11th to 20th	Day	30% 11% 22% 21% 13% 4	426
	21st to end	Day	28% 11% 19% 29% 10% 4	290
November	1st to 10th	Day	32% 19% 18% 20% 9% 3	200
	11th to 20th	Day	22% 12% 19% 29% 13% 6%	200
	21st to end	Day	28% 14% 20% 24% 9% 7%	200
December	1st to 10th	Day	20% 8% 17% 31% 21% 4	200
	11th to 20th	Day	24% 9% 16% 28% 22% 3	200
	21st to end	Day	20% 9% 20% 30% 15% 6%	220
January	1st to 10th	Night	27% 11% 24% 27% 10% 1	1095
	11th to 20th	Night	27% 13% 22% 29% 9% 1	900
	21st to end	Night	30% 10% 22% 28% 10% 1	962
February	1st to 10th	Night	27% 12% 21% 27% 13% 1	780
	11th to 20th	Night	24% 10% 22% 31% 13% 1	744
	21st to end	Night	19% 8% 26% 31% 15% 2	628
March	1st to 10th	Night	19% 9% 27% 30% 14% 1	760
	11th to 20th	Night	16% 11% 27% 34% 11% 1	760
	21st to end	Night	17% 12% 21% 30% 18% 2	836
April	1st to 10th	Night	20% 8% 17% 36% 17% 2	760
	11th to 20th	Night	15% 10% 24% 33% 18%	606
	21st to end	Night	22% 7% 21% 33% 17% 1	380
May	1st to 10th	Night	20% 7% 17% 38% 18% 1	380
	11th to 20th	Night	17% 2 19% 38% 21% 2	374
	21st to end	Night	16% 5% 21% 35% 21% 2	411
June	1st to 10th	Night	16% 7% 19% 40% 17% 1	380
	11th to 20th	Night	26% 5% 16% 34% 17% 2	380
	21st to end	Night	20% 4 16% 34% 23% 2	380
July	1st to 10th	Night	16% 5% 13% 40% 26% 1	370
	11th to 20th	Night	17% 6% 13% 31% 31% 2	368
	21st to end	Night	15% 7% 10% 36% 28% 3	416
August	1st to 10th	Night	11% 6% 9% 32% 39% 3	378
	11th to 20th	Night	11% 4 9% 43% 31% 2	376
	21st to end	Night	24% 6% 10% 36% 24% 1	650
September	1st to 10th	Night	25% 6% 10% 35% 23% 1	760
	11th to 20th	Night	21% 4 10% 34% 28% 3	760
	21st to end	Night	30% 11% 17% 29% 13% 1	760
October	1st to 10th	Night	26% 7% 19% 31% 16% 1	760
	11th to 20th	Night	27% 8% 20% 29% 15% 1	760
	21st to end	Night	31% 9% 21% 29% 9% 1	836
November	1st to 10th	Night	35% 12% 21% 22% 10%	780
	11th to 20th	Night	28% 15% 24% 24% 8% 1	878
	21st to end	Night	31% 13% 21% 26% 9% 1	1018
December	1st to 10th	Night	23% 11% 20% 34% 11% 1	1100
	11th to 20th	Night	26% 12% 23% 27% 10% 1	1100
	21st to end	Night	21% 12% 27% 27% 11% 2	1210

Page generated at 2025-02-03 00:05:53. Version ac07

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