AUGO Fort Vermillion
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AUGO Fort Vermillion clear sky chart from 2005-11-06 to 2025-05-26.

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	8% 9% 3 9% 6% 5% 6% 4 7% 8% 35%	116441
	Night	7% 11% 4 11% 7% 6% 5% 4 6% 8% 31%	121478
Transparency	Day	44% 9% 18% 22% 7%	116152
	Night	49% 8% 16% 20% 7%	121413
Seeing	Day	12% 8% 25% 30% 19% 5%	17532
	Night	13% 6% 25% 35% 18% 3	25639

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	7% 12% 5% 15% 9% 7% 7% 5% 8% 8% 18%	2597
	11th to 20th	Day	6% 10% 4 10% 7% 5% 5% 5% 8% 9% 32%	2702
	21st to end	Day	7% 17% 6% 13% 6% 4 4 3 7% 8% 24%	3084
February	1st to 10th	Day	7% 12% 5% 10% 8% 7% 7% 5% 5% 7% 28%	1600
	11th to 20th	Day	6% 13% 4 10% 6% 7% 6% 4 6% 8% 29%	1560
	21st to end	Day	4 13% 5% 11% 7% 7% 6% 6% 7% 9% 24%	1489
March	1st to 10th	Day	2 8% 6% 14% 8% 7% 7% 5% 8% 9% 27%	4518
	11th to 20th	Day	4 10% 5% 13% 8% 7% 7% 4 6% 6% 30%	4750
	21st to end	Day	3 9% 3 9% 6% 5% 5% 4 6% 7% 43%	5837
April	1st to 10th	Day	5% 10% 3 9% 6% 6% 6% 5% 6% 8% 36%	2480
	11th to 20th	Day	5% 7% 2 8% 6% 6% 6% 5% 8% 7% 39%	2597
	21st to end	Day	10% 10% 3 8% 6% 7% 6% 5% 7% 7% 33%	2835
May	1st to 10th	Day	8% 6% 2 6% 3 4 5% 4 6% 8% 48%	4890
	11th to 20th	Day	13% 10% 4 7% 5% 5% 5% 5% 6% 7% 33%	4994
	21st to end	Day	11% 6% 3 8% 6% 5% 5% 4 6% 8% 39%	5716
June	1st to 10th	Day	13% 8% 3 8% 5% 5% 5% 5% 7% 8% 32%	3230
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 4 7% 8% 30%	3230
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 4 7% 10% 36%	3230
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 11% 42%	5349
	11th to 20th	Day	7% 4 2 5% 5% 5% 6% 5% 8% 9% 44%	5060
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 7% 9% 38%	5486
August	1st to 10th	Day	6% 4 2 5% 4 5% 5% 3 6% 8% 51%	4708
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 4 8% 9% 40%	4330
	21st to end	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 7% 38%	4656
September	1st to 10th	Day	14% 5% 2 6% 4 4 4 4 6% 9% 40%	2394
	11th to 20th	Day	9% 8% 2 8% 5% 3 5% 4 6% 8% 42%	2184
	21st to end	Day	10% 8% 3 8% 5% 5% 5% 4 7% 9% 38%	2090
October	1st to 10th	Day	9% 10% 5% 9% 6% 4 4 4 7% 8% 34%	3140
	11th to 20th	Day	10% 13% 3 7% 5% 5% 5% 4 6% 8% 34%	2842
	21st to end	Day	8% 14% 4 10% 5% 5% 7% 5% 6% 6% 28%	2922
November	1st to 10th	Day	12% 13% 5% 11% 9% 6% 5% 3 5% 7% 25%	1372
	11th to 20th	Day	11% 17% 4 14% 8% 5% 5% 5% 5% 7% 20%	1400
	21st to end	Day	9% 12% 5% 12% 7% 7% 6% 5% 6% 7% 25%	1174
December	1st to 10th	Day	7% 15% 6% 16% 10% 7% 4 4 6% 5% 20%	1630
	11th to 20th	Day	8% 20% 7% 11% 7% 6% 6% 3 5% 6% 21%	1879
	21st to end	Day	6% 12% 5% 15% 7% 6% 7% 4 5% 5% 28%	2486
January	1st to 10th	Night	6% 12% 6% 17% 9% 8% 6% 5% 6% 7% 17%	7346
	11th to 20th	Night	6% 11% 4 10% 6% 5% 6% 5% 8% 8% 32%	7196
	21st to end	Night	6% 16% 5% 14% 8% 6% 5% 4 5% 7% 26%	7858
February	1st to 10th	Night	5% 10% 5% 12% 6% 6% 6% 4 6% 7% 34%	2819
	11th to 20th	Night	6% 14% 4 10% 7% 4 5% 5% 6% 7% 33%	2726
	21st to end	Night	5% 10% 4 12% 6% 7% 6% 5% 6% 8% 31%	2137
March	1st to 10th	Night	4 8% 5% 12% 7% 6% 6% 4 6% 8% 32%	5376
	11th to 20th	Night	4 10% 6% 14% 7% 6% 6% 4 6% 8% 27%	5249
	21st to end	Night	3 8% 4 12% 6% 6% 5% 4 6% 6% 40%	5138
April	1st to 10th	Night	6% 11% 4 9% 6% 5% 6% 4 7% 7% 34%	1920
	11th to 20th	Night	7% 10% 4 8% 5% 5% 6% 5% 7% 7% 36%	1751
	21st to end	Night	11% 10% 3 7% 6% 5% 6% 4 7% 9% 30%	1565
May	1st to 10th	Night	9% 8% 2 6% 5% 5% 5% 4 7% 8% 41%	2290
	11th to 20th	Night	10% 7% 3 8% 6% 7% 6% 5% 8% 9% 32%	2120
	21st to end	Night	12% 7% 2 6% 6% 4 5% 5% 8% 9% 35%	1972
June	1st to 10th	Night	14% 8% 3 7% 6% 6% 8% 7% 5% 7% 29%	950
	11th to 20th	Night	15% 7% 2 8% 5% 4 6% 5% 7% 7% 36%	950
	21st to end	Night	10% 6% 3 7% 6% 4 6% 4 9% 8% 38%	950
July	1st to 10th	Night	7% 5% 2 7% 5% 6% 7% 4 9% 10% 36%	1607
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 4 6% 8% 44%	1900
	21st to end	Night	10% 5% 2 5% 4 5% 5% 5% 9% 11% 41%	2066
August	1st to 10th	Night	6% 3 1 4 4 4 5% 5% 6% 8% 53%	2219
	11th to 20th	Night	7% 5% 3 8% 5% 4 5% 4 7% 8% 45%	2497
	21st to end	Night	10% 6% 2 6% 4 5% 4 4 7% 9% 41%	3006
September	1st to 10th	Night	13% 5% 3 7% 5% 4 4 4 7% 8% 39%	1785
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 5% 6% 7% 38%	1995
	21st to end	Night	11% 6% 3 7% 6% 5% 5% 4 6% 9% 37%	2090
October	1st to 10th	Night	7% 8% 3 7% 5% 5% 5% 4 7% 9% 39%	3834
	11th to 20th	Night	9% 11% 3 8% 4 5% 5% 4 7% 8% 35%	4086
	21st to end	Night	9% 15% 4 13% 7% 5% 4 4 5% 6% 28%	4598
November	1st to 10th	Night	12% 15% 5% 11% 6% 5% 5% 4 6% 7% 26%	2925
	11th to 20th	Night	12% 15% 5% 14% 7% 6% 5% 3 6% 7% 20%	3000
	21st to end	Night	9% 14% 6% 13% 7% 5% 4 3 6% 8% 24%	3224
December	1st to 10th	Night	8% 14% 6% 13% 9% 7% 6% 5% 6% 7% 20%	5550
	11th to 20th	Night	9% 19% 6% 13% 7% 6% 5% 4 5% 6% 21%	6313
	21st to end	Night	4 11% 5% 13% 8% 6% 6% 4 6% 7% 28%	8470

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% 8% 13% 17% 4	2597
	11th to 20th	Day	45% 9% 14% 18% 13%	2720
	21st to end	Day	57% 8% 16% 12% 6%	3084
February	1st to 10th	Day	54% 7% 12% 17% 10%	1600
	11th to 20th	Day	50% 8% 19% 18% 5%	1568
	21st to end	Day	51% 11% 16% 16% 5%	1489
March	1st to 10th	Day	49% 9% 16% 22% 5%	4518
	11th to 20th	Day	52% 7% 16% 21% 3	4751
	21st to end	Day	37% 7% 15% 22% 18% 1	5837
April	1st to 10th	Day	44% 9% 16% 20% 10% 1	2480
	11th to 20th	Day	39% 8% 14% 25% 14% 1	2597
	21st to end	Day	47% 9% 16% 19% 8%	2835
May	1st to 10th	Day	31% 7% 14% 28% 19% 1	4890
	11th to 20th	Day	46% 8% 11% 23% 10% 1	4998
	21st to end	Day	40% 8% 14% 22% 14% 1	5717
June	1st to 10th	Day	45% 9% 16% 19% 9% 1	3230
	11th to 20th	Day	48% 10% 16% 20% 6%	3230
	21st to end	Day	41% 12% 18% 23% 7%	3230
July	1st to 10th	Day	31% 10% 26% 29% 3	5265
	11th to 20th	Day	32% 10% 22% 27% 8%	4973
	21st to end	Day	39% 8% 21% 28% 3	5313
August	1st to 10th	Day	29% 10% 20% 36% 6%	4689
	11th to 20th	Day	37% 10% 20% 23% 9% 1	4372
	21st to end	Day	43% 9% 27% 20% 2	4655
September	1st to 10th	Day	40% 10% 25% 20% 5%	2394
	11th to 20th	Day	38% 8% 25% 27% 2	2184
	21st to end	Day	41% 10% 21% 24% 4	2090
October	1st to 10th	Day	48% 7% 19% 23% 3	3140
	11th to 20th	Day	46% 7% 21% 22% 3	2842
	21st to end	Day	54% 8% 20% 15% 3	2922
November	1st to 10th	Day	57% 9% 17% 14% 3	1372
	11th to 20th	Day	61% 10% 15% 12% 2	1400
	21st to end	Day	57% 9% 15% 16% 3	1174
December	1st to 10th	Day	64% 7% 15% 11% 3	1630
	11th to 20th	Day	64% 6% 10% 19% 2	1880
	21st to end	Day	55% 7% 13% 19% 5%	2486
January	1st to 10th	Night	63% 7% 11% 15% 5%	7346
	11th to 20th	Night	46% 8% 13% 20% 13%	7240
	21st to end	Night	54% 8% 20% 13% 5%	7858
February	1st to 10th	Night	48% 6% 16% 20% 10%	2819
	11th to 20th	Night	48% 7% 16% 23% 5%	2728
	21st to end	Night	49% 9% 16% 21% 5%	2137
March	1st to 10th	Night	48% 6% 14% 26% 6%	5376
	11th to 20th	Night	51% 7% 15% 24% 3	5249
	21st to end	Night	41% 6% 11% 26% 14% 2	5138
April	1st to 10th	Night	44% 9% 13% 21% 11% 2	1920
	11th to 20th	Night	43% 7% 11% 20% 16% 2	1751
	21st to end	Night	47% 9% 13% 20% 10% 1	1565
May	1st to 10th	Night	36% 7% 12% 26% 17% 2	2290
	11th to 20th	Night	42% 9% 10% 20% 16% 1	2120
	21st to end	Night	38% 9% 17% 19% 16% 1	1972
June	1st to 10th	Night	48% 10% 11% 21% 9% 1	950
	11th to 20th	Night	45% 10% 15% 21% 8% 1	950
	21st to end	Night	39% 12% 17% 24% 8% 1	950
July	1st to 10th	Night	37% 10% 21% 23% 8%	1582
	11th to 20th	Night	35% 8% 18% 29% 9%	1864
	21st to end	Night	34% 9% 20% 33% 5%	2000
August	1st to 10th	Night	26% 9% 17% 41% 7%	2213
	11th to 20th	Night	35% 8% 19% 24% 13% 1	2521
	21st to end	Night	38% 8% 26% 24% 3	3006
September	1st to 10th	Night	40% 10% 20% 23% 7%	1785
	11th to 20th	Night	42% 10% 18% 24% 6%	1995
	21st to end	Night	42% 8% 20% 22% 8%	2090
October	1st to 10th	Night	40% 7% 19% 28% 6% 1	3834
	11th to 20th	Night	44% 8% 20% 23% 5%	4086
	21st to end	Night	56% 7% 18% 17% 2	4598
November	1st to 10th	Night	57% 8% 15% 17% 3	2925
	11th to 20th	Night	61% 10% 13% 14% 2	3000
	21st to end	Night	58% 7% 16% 16% 3 1	3224
December	1st to 10th	Night	61% 7% 15% 13% 4	5550
	11th to 20th	Night	64% 6% 13% 14% 3	6311
	21st to end	Night	52% 8% 17% 18% 5%	8470

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% 9% 23% 36% 16% 7%	200
	11th to 20th	Day	19% 7% 22% 41% 12% 1	200
	21st to end	Day	16% 10% 27% 35% 10% 3	220
February	1st to 10th	Day	10% 10% 28% 31% 15% 8%	200
	11th to 20th	Day	11% 7% 29% 33% 16% 6%	200
	21st to end	Day	7% 10% 30% 30% 18% 4	279
March	1st to 10th	Day	5% 11% 27% 31% 22% 4	500
	11th to 20th	Day	9% 10% 32% 35% 10% 4	500
	21st to end	Day	9% 10% 29% 34% 16% 2	550
April	1st to 10th	Day	8% 12% 34% 29% 14% 2	500
	11th to 20th	Day	9% 7% 33% 32% 15% 4	492
	21st to end	Day	13% 13% 27% 29% 17% 1	535
May	1st to 10th	Day	10% 13% 27% 30% 16% 4	703
	11th to 20th	Day	12% 10% 24% 28% 19% 6%	808
	21st to end	Day	11% 6% 22% 34% 23% 5%	972
June	1st to 10th	Day	16% 9% 26% 29% 17% 3	870
	11th to 20th	Day	17% 6% 23% 28% 20% 5%	870
	21st to end	Day	10% 5% 18% 31% 27% 8%	870
July	1st to 10th	Day	10% 6% 21% 30% 26% 6%	856
	11th to 20th	Day	11% 5% 18% 31% 26% 9%	852
	21st to end	Day	13% 5% 17% 27% 29% 10%	947
August	1st to 10th	Day	12% 3 16% 29% 28% 11%	677
	11th to 20th	Day	13% 9% 30% 29% 14% 5%	477
	21st to end	Day	17% 6% 24% 30% 17% 7%	539
September	1st to 10th	Day	17% 8% 28% 26% 14% 8%	490
	11th to 20th	Day	10% 7% 25% 28% 23% 8%	490
	21st to end	Day	11% 9% 30% 30% 16% 4	490
October	1st to 10th	Day	17% 11% 27% 26% 15% 3	412
	11th to 20th	Day	16% 7% 33% 30% 11% 3	300
	21st to end	Day	19% 10% 31% 26% 10% 4	313
November	1st to 10th	Day	15% 6% 27% 35% 16% 3	200
	11th to 20th	Day	17% 7% 26% 36% 13% 3	200
	21st to end	Day	15% 8% 27% 31% 17% 4	200
December	1st to 10th	Day	13% 8% 19% 38% 21% 2	200
	11th to 20th	Day	9% 13% 28% 38% 10% 4	200
	21st to end	Day	8% 5% 24% 34% 22% 7%	220
January	1st to 10th	Night	15% 5% 23% 36% 18% 3	1100
	11th to 20th	Night	15% 7% 26% 37% 13% 2	1100
	21st to end	Night	15% 10% 30% 32% 12% 2	1189
February	1st to 10th	Night	8% 6% 27% 35% 19% 5%	819
	11th to 20th	Night	13% 7% 24% 36% 17% 3	784
	21st to end	Night	8% 5% 26% 39% 18% 3	660
March	1st to 10th	Night	7% 8% 26% 34% 22% 4	800
	11th to 20th	Night	12% 8% 29% 35% 15% 2	800
	21st to end	Night	9% 5% 26% 40% 18% 2	880
April	1st to 10th	Night	11% 9% 26% 34% 18% 2	720
	11th to 20th	Night	11% 6% 29% 35% 16% 2	563
	21st to end	Night	14% 8% 28% 34% 16% 1	400
May	1st to 10th	Night	12% 6% 28% 37% 17% 2	400
	11th to 20th	Night	9% 9% 26% 34% 20% 2	394
	21st to end	Night	13% 6% 18% 38% 24% 1	422
June	1st to 10th	Night	16% 5% 21% 34% 22% 2	380
	11th to 20th	Night	17% 3 18% 32% 29% 1	380
	21st to end	Night	10% 3 15% 40% 25% 6%	380
July	1st to 10th	Night	11% 4 15% 39% 29% 2	370
	11th to 20th	Night	13% 2 16% 36% 29% 5%	368
	21st to end	Night	9% 3 15% 32% 36% 5%	416
August	1st to 10th	Night	9% 4 12% 37% 31% 7%	378
	11th to 20th	Night	8% 3 18% 45% 23% 2	376
	21st to end	Night	15% 2 20% 34% 26% 2	539
September	1st to 10th	Night	16% 3 19% 36% 22% 3	645
	11th to 20th	Night	14% 5% 19% 37% 20% 4	760
	21st to end	Night	13% 6% 26% 35% 17% 3	760
October	1st to 10th	Night	13% 7% 29% 34% 15% 2	760
	11th to 20th	Night	14% 6% 29% 35% 14% 2	760
	21st to end	Night	20% 9% 27% 31% 12% 1	891
November	1st to 10th	Night	17% 6% 26% 32% 16% 2	975
	11th to 20th	Night	19% 7% 25% 32% 16% 2	1000
	21st to end	Night	15% 6% 29% 34% 14% 2	1060
December	1st to 10th	Night	14% 6% 24% 37% 16% 3	1100
	11th to 20th	Night	15% 9% 28% 33% 13% 3	1100
	21st to end	Night	11% 5% 21% 36% 23% 4	1210

Page generated at 2025-05-23 07:21:02. Version ac07

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