Dominion City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dominion City clear sky chart from 2005-11-06 to 2024-04-10.

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% 4 8% 7% 4 5% 5% 6% 7% 34%	82565
	Night	10% 10% 5% 8% 7% 4 5% 5% 5% 7% 33%	86211
Transparency	Day	47% 9% 15% 21% 7%	82271
	Night	48% 8% 14% 20% 8% 1	86086
Seeing	Day	14% 9% 31% 29% 14% 4	15294
	Night	14% 7% 33% 33% 12% 1	25449

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	6% 14% 7% 11% 10% 5% 5% 7% 7% 6% 22%	2219
	11th to 20th	Day	4 7% 6% 15% 15% 9% 12% 10% 6% 6% 11%	2244
	21st to end	Day	9% 16% 7% 15% 9% 4 6% 6% 6% 6% 16%	2794
February	1st to 10th	Day	9% 13% 6% 9% 9% 6% 8% 8% 7% 6% 21%	1654
	11th to 20th	Day	6% 10% 4 10% 10% 6% 7% 8% 7% 8% 24%	1664
	21st to end	Day	7% 9% 4 11% 10% 6% 8% 7% 6% 7% 24%	1499
March	1st to 10th	Day	13% 10% 4 8% 14% 4 6% 5% 6% 7% 23%	3214
	11th to 20th	Day	8% 10% 5% 12% 12% 5% 6% 6% 6% 8% 23%	3478
	21st to end	Day	10% 13% 7% 11% 7% 3 5% 4 5% 7% 30%	3814
April	1st to 10th	Day	10% 11% 5% 7% 6% 3 5% 5% 6% 8% 34%	2288
	11th to 20th	Day	14% 10% 3 7% 7% 3 6% 6% 5% 6% 33%	2312
	21st to end	Day	18% 8% 4 8% 5% 3 4 5% 5% 7% 33%	2340
May	1st to 10th	Day	17% 8% 4 5% 5% 4 4 5% 5% 5% 38%	2387
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 5% 5% 8% 39%	2565
	21st to end	Day	18% 6% 3 5% 5% 3 5% 5% 5% 8% 38%	2918
June	1st to 10th	Day	12% 6% 3 6% 6% 2 5% 6% 7% 9% 38%	2700
	11th to 20th	Day	16% 5% 3 5% 5% 4 5% 5% 7% 8% 38%	2700
	21st to end	Day	12% 5% 2 6% 5% 3 6% 6% 6% 10% 37%	2700
July	1st to 10th	Day	7% 2 1 4 5% 4 5% 6% 7% 10% 50%	2700
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 6% 6% 9% 44%	2700
	21st to end	Day	6% 3 2 4 4 3 4 5% 5% 9% 56%	2877
August	1st to 10th	Day	8% 5% 2 4 6% 3 4 6% 6% 8% 48%	2399
	11th to 20th	Day	9% 4 2 4 5% 3 5% 4 6% 10% 48%	2301
	21st to end	Day	11% 5% 2 4 5% 3 4 4 6% 6% 50%	2574
September	1st to 10th	Day	11% 6% 2 4 4 2 4 5% 6% 8% 49%	2221
	11th to 20th	Day	13% 6% 1 5% 5% 3 5% 6% 5% 9% 42%	1980
	21st to end	Day	16% 6% 2 4 4 3 4 4 6% 8% 42%	1980
October	1st to 10th	Day	18% 9% 3 5% 6% 3 4 4 5% 7% 36%	1838
	11th to 20th	Day	15% 9% 3 6% 6% 3 5% 4 5% 8% 34%	1779
	21st to end	Day	15% 11% 4 8% 7% 5% 5% 6% 5% 6% 28%	1782
November	1st to 10th	Day	15% 14% 5% 8% 5% 4 5% 4 4 6% 30%	1533
	11th to 20th	Day	10% 15% 6% 13% 8% 3 5% 4 5% 6% 26%	1520
	21st to end	Day	13% 13% 6% 9% 10% 4 5% 5% 5% 6% 24%	1440
December	1st to 10th	Day	8% 14% 6% 13% 8% 6% 8% 7% 5% 6% 20%	1330
	11th to 20th	Day	10% 13% 7% 13% 8% 5% 7% 7% 7% 7% 17%	1679
	21st to end	Day	10% 13% 6% 12% 10% 5% 9% 6% 6% 6% 17%	2442
January	1st to 10th	Night	5% 13% 7% 12% 9% 7% 7% 7% 7% 7% 20%	4737
	11th to 20th	Night	5% 12% 6% 13% 13% 8% 11% 7% 5% 5% 15%	4663
	21st to end	Night	8% 16% 8% 14% 8% 4 6% 6% 5% 5% 19%	4873
February	1st to 10th	Night	8% 12% 5% 10% 9% 5% 8% 6% 6% 7% 26%	2525
	11th to 20th	Night	7% 9% 4 8% 7% 5% 6% 6% 8% 9% 31%	2403
	21st to end	Night	7% 9% 5% 12% 9% 4 6% 6% 5% 6% 31%	1970
March	1st to 10th	Night	11% 9% 4 7% 10% 4 5% 5% 5% 7% 32%	3646
	11th to 20th	Night	6% 8% 5% 9% 8% 4 5% 6% 6% 8% 36%	3480
	21st to end	Night	10% 13% 5% 11% 8% 4 4 4 4 6% 31%	3817
April	1st to 10th	Night	10% 6% 3 5% 5% 4 6% 6% 7% 7% 41%	1877
	11th to 20th	Night	14% 9% 5% 7% 6% 3 4 5% 5% 6% 36%	1599
	21st to end	Night	15% 9% 3 6% 5% 3 5% 5% 6% 6% 37%	1620
May	1st to 10th	Night	13% 7% 3 6% 5% 3 5% 3 6% 7% 42%	1571
	11th to 20th	Night	14% 7% 3 5% 5% 3 4 4 6% 10% 39%	1327
	21st to end	Night	15% 6% 3 5% 4 3 4 4 6% 9% 42%	1358
June	1st to 10th	Night	12% 4 3 5% 4 3 5% 6% 6% 8% 45%	1260
	11th to 20th	Night	11% 5% 3 5% 4 3 4 4 5% 9% 45%	1260
	21st to end	Night	9% 4 2 5% 7% 3 5% 5% 6% 10% 44%	1260
July	1st to 10th	Night	6% 3 2 3 3 3 4 5% 5% 10% 56%	1260
	11th to 20th	Night	6% 3 1 4 5% 3 4 6% 8% 8% 54%	1260
	21st to end	Night	6% 2 2 3 3 2 4 4 6% 9% 59%	1438
August	1st to 10th	Night	6% 3 1 4 5% 3 5% 4 6% 9% 54%	1539
	11th to 20th	Night	8% 4 2 4 3 3 4 6% 5% 9% 52%	1600
	21st to end	Night	10% 3 2 4 3 3 4 4 5% 8% 55%	1782
September	1st to 10th	Night	9% 5% 3 4 3 2 3 5% 5% 9% 54%	1736
	11th to 20th	Night	10% 4 3 4 4 3 4 5% 5% 9% 49%	1980
	21st to end	Night	16% 6% 2 4 5% 3 4 4 5% 8% 44%	1980
October	1st to 10th	Night	17% 8% 3 6% 6% 3 5% 4 5% 6% 37%	2104
	11th to 20th	Night	16% 10% 4 5% 4 3 4 4 4 7% 39%	2178
	21st to end	Night	15% 11% 3 7% 6% 3 5% 4 5% 8% 34%	2574
November	1st to 10th	Night	13% 12% 6% 8% 7% 3 4 5% 5% 6% 30%	2545
	11th to 20th	Night	11% 14% 6% 10% 8% 3 5% 5% 4 6% 28%	2660
	21st to end	Night	12% 13% 5% 10% 9% 5% 5% 4 4 6% 28%	2736
December	1st to 10th	Night	7% 13% 7% 11% 11% 5% 6% 6% 5% 6% 22%	2850
	11th to 20th	Night	10% 14% 6% 13% 9% 5% 5% 5% 5% 5% 22%	3518
	21st to end	Night	12% 12% 5% 10% 10% 6% 6% 5% 6% 6% 21%	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	59% 7% 14% 16% 4	2219
	11th to 20th	Day	70% 8% 11% 8% 2	2265
	21st to end	Day	65% 10% 7% 14% 4	2794
February	1st to 10th	Day	60% 8% 12% 12% 7% 1	1654
	11th to 20th	Day	53% 8% 14% 16% 8%	1673
	21st to end	Day	55% 8% 15% 15% 7%	1499
March	1st to 10th	Day	52% 11% 17% 16% 4	3214
	11th to 20th	Day	53% 13% 15% 14% 4	3480
	21st to end	Day	53% 7% 13% 20% 7%	3814
April	1st to 10th	Day	47% 7% 14% 22% 9% 1	2288
	11th to 20th	Day	49% 6% 14% 19% 10% 1	2312
	21st to end	Day	50% 6% 16% 19% 7% 2	2340
May	1st to 10th	Day	47% 7% 12% 22% 12% 1	2387
	11th to 20th	Day	43% 6% 13% 25% 12% 1	2569
	21st to end	Day	44% 9% 13% 23% 11% 1	2918
June	1st to 10th	Day	40% 9% 20% 23% 8%	2700
	11th to 20th	Day	42% 10% 15% 23% 9% 1	2700
	21st to end	Day	40% 12% 19% 24% 5%	2700
July	1st to 10th	Day	27% 10% 21% 31% 11% 1	2626
	11th to 20th	Day	34% 9% 19% 26% 11%	2619
	21st to end	Day	26% 10% 20% 32% 12% 1	2717
August	1st to 10th	Day	32% 10% 20% 30% 8% 1	2383
	11th to 20th	Day	31% 10% 22% 30% 7%	2301
	21st to end	Day	33% 8% 18% 30% 11%	2574
September	1st to 10th	Day	33% 9% 17% 30% 11% 1	2221
	11th to 20th	Day	38% 10% 20% 25% 6% 1	1980
	21st to end	Day	40% 7% 17% 31% 5%	1980
October	1st to 10th	Day	47% 8% 17% 20% 8%	1838
	11th to 20th	Day	48% 7% 15% 22% 8% 1	1779
	21st to end	Day	54% 10% 17% 15% 4	1782
November	1st to 10th	Day	56% 7% 14% 17% 5% 1	1533
	11th to 20th	Day	58% 9% 15% 13% 5%	1520
	21st to end	Day	61% 9% 14% 13% 3	1440
December	1st to 10th	Day	62% 9% 14% 11% 4	1330
	11th to 20th	Day	62% 9% 14% 10% 4	1680
	21st to end	Day	63% 9% 9% 14% 4	2442
January	1st to 10th	Night	58% 11% 12% 14% 4	4737
	11th to 20th	Night	68% 9% 9% 11% 3	4704
	21st to end	Night	64% 9% 12% 13% 3	4873
February	1st to 10th	Night	56% 7% 14% 15% 8%	2525
	11th to 20th	Night	45% 9% 16% 19% 10%	2404
	21st to end	Night	53% 7% 13% 18% 10%	1970
March	1st to 10th	Night	47% 11% 15% 19% 8%	3646
	11th to 20th	Night	39% 12% 18% 22% 9% 1	3480
	21st to end	Night	52% 8% 12% 20% 9% 1	3817
April	1st to 10th	Night	39% 8% 15% 21% 14% 2	1877
	11th to 20th	Night	48% 6% 10% 20% 14% 2	1599
	21st to end	Night	44% 7% 13% 24% 10% 2	1620
May	1st to 10th	Night	42% 5% 14% 23% 15% 1	1571
	11th to 20th	Night	40% 7% 12% 24% 15% 2	1327
	21st to end	Night	39% 6% 17% 20% 17% 1	1358
June	1st to 10th	Night	34% 11% 18% 25% 11% 2	1260
	11th to 20th	Night	35% 8% 17% 26% 11% 2	1260
	21st to end	Night	36% 9% 19% 28% 7% 1	1260
July	1st to 10th	Night	23% 8% 19% 34% 13% 2	1225
	11th to 20th	Night	24% 12% 19% 27% 17% 1	1218
	21st to end	Night	23% 6% 16% 37% 16% 2	1358
August	1st to 10th	Night	26% 7% 20% 34% 12% 1	1531
	11th to 20th	Night	27% 8% 22% 30% 12% 1	1600
	21st to end	Night	28% 7% 15% 33% 16% 1	1782
September	1st to 10th	Night	28% 7% 16% 32% 16% 1	1736
	11th to 20th	Night	32% 9% 20% 28% 11% 1	1980
	21st to end	Night	39% 7% 14% 29% 10%	1980
October	1st to 10th	Night	47% 9% 14% 21% 8% 1	2104
	11th to 20th	Night	45% 7% 14% 26% 7%	2178
	21st to end	Night	50% 8% 15% 22% 5%	2574
November	1st to 10th	Night	53% 7% 15% 17% 6% 1	2545
	11th to 20th	Night	58% 9% 14% 14% 5% 1	2660
	21st to end	Night	58% 7% 16% 14% 5%	2736
December	1st to 10th	Night	61% 9% 15% 12% 3	2850
	11th to 20th	Night	62% 7% 14% 12% 4	3516
	21st to end	Night	58% 9% 12% 16% 5%	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	11% 7% 34% 32% 13% 3	270
	11th to 20th	Day	11% 10% 29% 37% 11% 1	270
	21st to end	Day	12% 9% 33% 32% 11% 2	297
February	1st to 10th	Day	13% 11% 34% 36% 5% 1	270
	11th to 20th	Day	10% 14% 37% 26% 12% 1	270
	21st to end	Day	8% 8% 44% 29% 10% 1	225
March	1st to 10th	Day	13% 8% 34% 32% 10% 2	270
	11th to 20th	Day	12% 12% 32% 28% 13% 2	270
	21st to end	Day	13% 13% 28% 31% 12% 2	297
April	1st to 10th	Day	13% 15% 31% 29% 10% 2	476
	11th to 20th	Day	18% 12% 33% 24% 12% 1	590
	21st to end	Day	20% 11% 32% 24% 11% 3	600
May	1st to 10th	Day	15% 13% 30% 29% 11% 2	603
	11th to 20th	Day	20% 9% 28% 26% 14% 4	625
	21st to end	Day	18% 9% 24% 31% 15% 3	679
June	1st to 10th	Day	12% 10% 28% 27% 17% 6%	630
	11th to 20th	Day	16% 12% 31% 27% 12% 3	630
	21st to end	Day	12% 7% 28% 31% 17% 6%	630
July	1st to 10th	Day	9% 4 30% 29% 21% 7%	621
	11th to 20th	Day	11% 8% 29% 29% 19% 4	618
	21st to end	Day	6% 5% 25% 35% 22% 8%	684
August	1st to 10th	Day	6% 5% 25% 33% 23% 7%	626
	11th to 20th	Day	10% 5% 23% 33% 19% 9%	615
	21st to end	Day	12% 8% 27% 28% 20% 5%	693
September	1st to 10th	Day	11% 7% 34% 30% 15% 3	511
	11th to 20th	Day	15% 10% 37% 23% 12% 3	270
	21st to end	Day	21% 9% 36% 25% 9% 1	270
October	1st to 10th	Day	20% 12% 29% 26% 11% 3	270
	11th to 20th	Day	13% 11% 37% 27% 11%	270
	21st to end	Day	24% 12% 36% 20% 7% 1	297
November	1st to 10th	Day	24% 10% 29% 29% 8% 1	270
	11th to 20th	Day	15% 13% 38% 24% 10%	270
	21st to end	Day	20% 11% 41% 24% 4	270
December	1st to 10th	Day	14% 9% 34% 31% 11% 1	270
	11th to 20th	Day	16% 12% 36% 30% 6%	270
	21st to end	Day	13% 9% 35% 27% 12% 3	297
January	1st to 10th	Night	9% 8% 36% 31% 14% 1	950
	11th to 20th	Night	14% 7% 35% 35% 9%	950
	21st to end	Night	13% 7% 38% 32% 9% 1	1045
February	1st to 10th	Night	13% 7% 31% 35% 13% 1	950
	11th to 20th	Night	11% 6% 33% 35% 13% 2	929
	21st to end	Night	10% 6% 37% 33% 13% 1	714
March	1st to 10th	Night	15% 6% 32% 31% 13% 2	711
	11th to 20th	Night	10% 7% 41% 30% 11% 1	570
	21st to end	Night	18% 8% 28% 30% 13% 3	627
April	1st to 10th	Night	13% 9% 32% 35% 10% 1	570
	11th to 20th	Night	16% 8% 32% 32% 11%	533
	21st to end	Night	18% 6% 28% 36% 12%	540
May	1st to 10th	Night	15% 9% 32% 33% 11%	540
	11th to 20th	Night	15% 10% 30% 31% 13% 1	531
	21st to end	Night	17% 6% 34% 32% 11% 1	584
June	1st to 10th	Night	14% 5% 28% 37% 15% 1	540
	11th to 20th	Night	12% 5% 33% 35% 14% 1	540
	21st to end	Night	10% 4 26% 39% 20% 1	540
July	1st to 10th	Night	7% 3 25% 44% 21% 1	525
	11th to 20th	Night	6% 4 27% 43% 19% 1	522
	21st to end	Night	6% 3 23% 43% 21% 3	591
August	1st to 10th	Night	7% 2 26% 44% 20% 1	537
	11th to 20th	Night	10% 3 24% 38% 22% 3	534
	21st to end	Night	11% 6% 24% 38% 21%	594
September	1st to 10th	Night	11% 3 34% 35% 16% 2	540
	11th to 20th	Night	14% 3 31% 39% 13% 1	540
	21st to end	Night	18% 5% 32% 33% 11% 1	540
October	1st to 10th	Night	22% 8% 32% 29% 8%	664
	11th to 20th	Night	22% 8% 33% 27% 9%	738
	21st to end	Night	18% 10% 34% 30% 8% 1	990
November	1st to 10th	Night	20% 8% 37% 27% 8%	925
	11th to 20th	Night	17% 9% 35% 29% 8% 1	950
	21st to end	Night	17% 10% 42% 24% 6% 1	950
December	1st to 10th	Night	13% 8% 33% 33% 12% 1	950
	11th to 20th	Night	17% 8% 36% 32% 6% 1	950
	21st to end	Night	19% 8% 33% 29% 10% 1	1045

Page generated at 2024-04-07 08:28:11. Version ac07

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