Victor Mine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victor Mine clear sky chart from 2005-11-06 to 2024-01-13.

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% 11% 5% 8% 7% 4 6% 6% 6% 7% 25%	74611
	Night	14% 12% 5% 9% 8% 4 6% 6% 6% 7% 23%	75140
Transparency	Day	57% 6% 12% 18% 7%	74293
	Night	59% 6% 12% 17% 6%	74993
Seeing	Day	20% 9% 27% 26% 14% 4	14410
	Night	19% 8% 29% 30% 12% 2	23639

By Month

Percentage Cloud Cover NE (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	10% 14% 7% 11% 9% 6% 8% 7% 9% 7% 12%	1328
	11th to 20th	Day	10% 14% 4 10% 11% 4 6% 10% 15% 8% 8%	1274
	21st to end	Day	6% 12% 6% 12% 9% 5% 11% 10% 8% 8% 13%	1530
February	1st to 10th	Day	6% 9% 6% 9% 8% 5% 9% 10% 12% 9% 17%	1440
	11th to 20th	Day	6% 12% 5% 10% 9% 4 8% 8% 10% 8% 19%	1524
	21st to end	Day	4 8% 4 9% 9% 5% 9% 12% 8% 9% 23%	1422
March	1st to 10th	Day	6% 11% 5% 11% 7% 6% 9% 8% 8% 8% 21%	1798
	11th to 20th	Day	7% 12% 6% 11% 9% 6% 7% 7% 6% 8% 22%	1948
	21st to end	Day	9% 11% 4 10% 7% 4 6% 7% 6% 7% 28%	2233
April	1st to 10th	Day	13% 14% 5% 9% 7% 5% 6% 5% 4 6% 25%	2230
	11th to 20th	Day	13% 11% 6% 9% 7% 4 5% 4 4 6% 31%	2312
	21st to end	Day	14% 12% 4 9% 5% 3 5% 4 4 6% 35%	2340
May	1st to 10th	Day	16% 12% 5% 8% 6% 3 5% 5% 5% 7% 28%	2584
	11th to 20th	Day	19% 8% 4 7% 6% 4 5% 4 5% 7% 32%	2656
	21st to end	Day	19% 10% 4 7% 6% 3 4 5% 6% 8% 28%	2919
June	1st to 10th	Day	19% 9% 4 7% 6% 3 4 4 4 6% 33%	2700
	11th to 20th	Day	17% 6% 3 6% 5% 3 6% 4 5% 8% 36%	2700
	21st to end	Day	17% 6% 2 6% 6% 4 4 5% 5% 8% 36%	2700
July	1st to 10th	Day	17% 7% 3 6% 6% 4 5% 6% 6% 9% 32%	2700
	11th to 20th	Day	17% 7% 2 5% 6% 4 5% 6% 7% 8% 33%	2700
	21st to end	Day	19% 8% 3 7% 7% 4 6% 5% 6% 8% 27%	2940
August	1st to 10th	Day	21% 8% 3 5% 5% 3 5% 6% 6% 8% 28%	2531
	11th to 20th	Day	20% 8% 3 7% 6% 4 5% 4 5% 7% 31%	2374
	21st to end	Day	21% 9% 4 6% 7% 3 5% 5% 6% 7% 27%	2574
September	1st to 10th	Day	20% 10% 4 6% 7% 3 5% 5% 6% 7% 27%	2256
	11th to 20th	Day	26% 12% 4 7% 6% 3 4 4 4 6% 25%	1980
	21st to end	Day	27% 13% 4 5% 4 2 4 3 4 6% 26%	1980
October	1st to 10th	Day	23% 16% 5% 6% 7% 3 5% 5% 5% 5% 20%	1872
	11th to 20th	Day	23% 22% 5% 8% 5% 4 4 4 4 5% 17%	1644
	21st to end	Day	20% 22% 6% 9% 7% 3 4 4 4 5% 14%	1782
November	1st to 10th	Day	22% 19% 6% 10% 8% 4 5% 5% 5% 3 14%	1496
	11th to 20th	Day	20% 22% 9% 11% 7% 4 4 3 3 5% 12%	1382
	21st to end	Day	17% 18% 8% 12% 10% 5% 6% 4 3 5% 12%	1330
December	1st to 10th	Day	10% 13% 8% 14% 10% 4 6% 5% 6% 6% 16%	1330
	11th to 20th	Day	8% 12% 7% 12% 8% 9% 9% 6% 7% 7% 14%	1671
	21st to end	Day	10% 19% 6% 12% 10% 5% 7% 5% 4 5% 15%	2431
January	1st to 10th	Night	10% 14% 6% 13% 10% 6% 11% 7% 9% 5% 9%	2838
	11th to 20th	Night	10% 13% 6% 11% 10% 5% 7% 10% 11% 8% 9%	2743
	21st to end	Night	7% 12% 6% 11% 9% 6% 10% 10% 10% 7% 12%	2826
February	1st to 10th	Night	5% 7% 4 11% 10% 6% 9% 12% 10% 10% 15%	2520
	11th to 20th	Night	7% 12% 5% 10% 8% 5% 9% 9% 9% 8% 17%	2322
	21st to end	Night	3 9% 5% 10% 7% 5% 8% 11% 8% 8% 25%	1832
March	1st to 10th	Night	9% 10% 3 8% 9% 5% 7% 9% 6% 8% 27%	2149
	11th to 20th	Night	7% 9% 6% 10% 9% 6% 7% 7% 5% 7% 27%	2010
	21st to end	Night	10% 11% 4 9% 7% 4 6% 6% 5% 6% 32%	2138
April	1st to 10th	Night	12% 12% 5% 9% 8% 4 7% 5% 5% 5% 28%	1729
	11th to 20th	Night	13% 10% 5% 9% 7% 4 5% 4 5% 7% 32%	1597
	21st to end	Night	12% 10% 5% 8% 6% 4 5% 4 4 6% 36%	1620
May	1st to 10th	Night	16% 9% 4 9% 5% 4 5% 5% 5% 7% 30%	1373
	11th to 20th	Night	17% 8% 4 5% 6% 3 4 5% 5% 7% 36%	1239
	21st to end	Night	18% 10% 4 8% 6% 4 5% 5% 6% 8% 27%	1357
June	1st to 10th	Night	19% 8% 2 5% 5% 4 5% 5% 5% 7% 37%	1260
	11th to 20th	Night	17% 6% 3 6% 5% 4 5% 5% 5% 7% 37%	1260
	21st to end	Night	16% 6% 2 6% 4 4 5% 5% 5% 7% 40%	1260
July	1st to 10th	Night	18% 7% 2 6% 5% 3 3 5% 5% 8% 37%	1260
	11th to 20th	Night	12% 7% 3 5% 4 4 5% 6% 7% 9% 37%	1260
	21st to end	Night	18% 5% 3 5% 5% 4 5% 6% 6% 8% 34%	1378
August	1st to 10th	Night	16% 7% 3 7% 6% 3 5% 6% 5% 9% 34%	1404
	11th to 20th	Night	18% 6% 4 6% 5% 3 4 4 6% 7% 36%	1526
	21st to end	Night	16% 8% 4 7% 6% 3 5% 4 5% 7% 34%	1782
September	1st to 10th	Night	18% 10% 2 5% 5% 4 5% 5% 6% 7% 34%	1684
	11th to 20th	Night	22% 10% 3 8% 7% 4 5% 5% 5% 6% 26%	1980
	21st to end	Night	22% 10% 4 7% 6% 4 4 4 4 7% 29%	1980
October	1st to 10th	Night	22% 13% 4 7% 5% 4 4 5% 4 5% 28%	2088
	11th to 20th	Night	22% 17% 5% 9% 6% 5% 4 4 4 6% 18%	2312
	21st to end	Night	17% 20% 8% 8% 7% 3 5% 4 5% 6% 17%	2574
November	1st to 10th	Night	20% 21% 7% 11% 8% 3 4 4 4 5% 14%	2580
	11th to 20th	Night	19% 19% 8% 11% 7% 4 4 4 4 5% 14%	2797
	21st to end	Night	15% 20% 8% 14% 9% 5% 4 4 4 5% 12%	2850
December	1st to 10th	Night	10% 18% 8% 14% 11% 4 6% 6% 6% 6% 12%	2850
	11th to 20th	Night	9% 15% 6% 11% 10% 5% 8% 8% 7% 5% 16%	3526
	21st to end	Night	12% 13% 7% 11% 11% 6% 6% 5% 6% 6% 17%	5236

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	66% 6% 11% 14% 3	1329
	11th to 20th	Day	62% 4 12% 17% 5%	1274
	21st to end	Day	64% 5% 7% 17% 7%	1530
February	1st to 10th	Day	55% 6% 11% 20% 9%	1440
	11th to 20th	Day	57% 5% 11% 20% 6%	1533
	21st to end	Day	51% 6% 13% 23% 8%	1422
March	1st to 10th	Day	57% 5% 10% 17% 11%	1800
	11th to 20th	Day	58% 5% 11% 18% 8% 1	1948
	21st to end	Day	53% 5% 11% 18% 13%	2233
April	1st to 10th	Day	60% 4 9% 15% 11% 1	2230
	11th to 20th	Day	54% 5% 8% 22% 10% 1	2312
	21st to end	Day	50% 6% 8% 22% 13% 2	2340
May	1st to 10th	Day	54% 5% 10% 20% 9% 1	2584
	11th to 20th	Day	52% 5% 12% 19% 11%	2660
	21st to end	Day	52% 7% 12% 23% 6%	2919
June	1st to 10th	Day	52% 5% 11% 21% 11% 1	2700
	11th to 20th	Day	45% 7% 11% 27% 10%	2700
	21st to end	Day	45% 8% 14% 23% 9% 1	2700
July	1st to 10th	Day	46% 9% 16% 25% 4	2626
	11th to 20th	Day	44% 9% 18% 25% 4	2619
	21st to end	Day	52% 10% 18% 17% 4	2777
August	1st to 10th	Day	52% 8% 18% 19% 3	2515
	11th to 20th	Day	52% 8% 15% 21% 4	2374
	21st to end	Day	55% 8% 17% 16% 4	2574
September	1st to 10th	Day	55% 9% 16% 16% 4	2256
	11th to 20th	Day	61% 5% 14% 18% 2	1980
	21st to end	Day	59% 6% 11% 17% 6%	1980
October	1st to 10th	Day	64% 7% 13% 12% 4	1872
	11th to 20th	Day	70% 6% 13% 9% 2	1644
	21st to end	Day	72% 6% 10% 12% 1	1782
November	1st to 10th	Day	74% 5% 10% 9% 2	1496
	11th to 20th	Day	77% 4 7% 9% 2	1382
	21st to end	Day	76% 4 7% 9% 3	1330
December	1st to 10th	Day	66% 6% 10% 14% 5%	1330
	11th to 20th	Day	62% 5% 11% 16% 6%	1671
	21st to end	Day	70% 4 6% 13% 7% 1	2431
January	1st to 10th	Night	71% 5% 10% 12% 2	2838
	11th to 20th	Night	64% 5% 12% 14% 5%	2743
	21st to end	Night	62% 6% 9% 16% 6%	2826
February	1st to 10th	Night	55% 7% 11% 19% 7%	2520
	11th to 20th	Night	58% 6% 11% 18% 7%	2324
	21st to end	Night	50% 7% 12% 21% 10%	1832
March	1st to 10th	Night	52% 5% 11% 20% 12% 1	2160
	11th to 20th	Night	54% 7% 10% 18% 10%	2011
	21st to end	Night	50% 5% 8% 22% 12% 1	2138
April	1st to 10th	Night	57% 5% 8% 17% 11% 2	1729
	11th to 20th	Night	52% 5% 9% 21% 12% 1	1597
	21st to end	Night	49% 5% 6% 22% 15% 2	1620
May	1st to 10th	Night	52% 5% 12% 21% 9% 1	1373
	11th to 20th	Night	47% 6% 14% 18% 15%	1240
	21st to end	Night	54% 6% 11% 21% 7% 1	1358
June	1st to 10th	Night	46% 7% 10% 23% 13%	1260
	11th to 20th	Night	46% 7% 12% 21% 13%	1260
	21st to end	Night	42% 7% 14% 25% 11% 1	1260
July	1st to 10th	Night	45% 8% 14% 28% 5%	1225
	11th to 20th	Night	39% 10% 18% 25% 8%	1218
	21st to end	Night	45% 9% 21% 21% 4	1301
August	1st to 10th	Night	45% 11% 19% 22% 2	1396
	11th to 20th	Night	46% 9% 17% 25% 2	1526
	21st to end	Night	49% 8% 17% 20% 6%	1782
September	1st to 10th	Night	48% 9% 18% 21% 5%	1684
	11th to 20th	Night	58% 9% 15% 16% 3	1980
	21st to end	Night	56% 7% 15% 17% 6%	1980
October	1st to 10th	Night	58% 6% 14% 19% 3	2088
	11th to 20th	Night	66% 7% 14% 11% 1	2312
	21st to end	Night	67% 7% 13% 12% 1	2574
November	1st to 10th	Night	73% 6% 9% 9% 3	2580
	11th to 20th	Night	72% 6% 10% 11% 1	2797
	21st to end	Night	75% 4 8% 10% 2	2850
December	1st to 10th	Night	70% 6% 9% 13% 2	2850
	11th to 20th	Night	64% 5% 10% 14% 6%	3525
	21st to end	Night	67% 5% 7% 14% 8%	5236

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% 12% 33% 24% 17% 3	180
	11th to 20th	Day	12% 9% 26% 33% 15% 6%	164
	21st to end	Day	12% 3 23% 37% 18% 7%	240
February	1st to 10th	Day	6% 7% 33% 34% 17% 3	240
	11th to 20th	Day	11% 8% 38% 27% 11% 5%	240
	21st to end	Day	10% 9% 37% 29% 12% 3	198
March	1st to 10th	Day	13% 10% 29% 25% 16% 7%	240
	11th to 20th	Day	11% 12% 30% 29% 13% 5%	388
	21st to end	Day	11% 9% 32% 31% 14% 3	462
April	1st to 10th	Day	15% 8% 30% 29% 15% 2	420
	11th to 20th	Day	19% 10% 26% 26% 12% 7%	412
	21st to end	Day	15% 6% 28% 28% 16% 6%	420
May	1st to 10th	Day	19% 10% 29% 23% 15% 4	564
	11th to 20th	Day	20% 14% 26% 27% 11% 2	625
	21st to end	Day	24% 10% 26% 28% 10% 3	679
June	1st to 10th	Day	21% 9% 30% 26% 12% 3	630
	11th to 20th	Day	20% 7% 26% 28% 15% 4	630
	21st to end	Day	19% 7% 29% 24% 17% 4	630
July	1st to 10th	Day	17% 9% 26% 28% 16% 5%	621
	11th to 20th	Day	19% 7% 25% 30% 16% 2	618
	21st to end	Day	20% 6% 21% 28% 17% 6%	684
August	1st to 10th	Day	23% 6% 22% 26% 18% 5%	626
	11th to 20th	Day	20% 8% 22% 25% 16% 8%	510
	21st to end	Day	24% 5% 25% 25% 14% 6%	495
September	1st to 10th	Day	21% 9% 30% 29% 8% 3	450
	11th to 20th	Day	27% 10% 24% 22% 12% 4	450
	21st to end	Day	30% 8% 26% 19% 12% 4	450
October	1st to 10th	Day	27% 12% 27% 22% 9% 3	450
	11th to 20th	Day	34% 11% 24% 17% 11% 3	294
	21st to end	Day	24% 10% 31% 23% 9% 3	297
November	1st to 10th	Day	30% 11% 28% 22% 9% 1	185
	11th to 20th	Day	27% 12% 27% 24% 7% 3	180
	21st to end	Day	24% 12% 37% 16% 7% 3	180
December	1st to 10th	Day	17% 6% 31% 32% 9% 5%	180
	11th to 20th	Day	15% 7% 31% 32% 10% 5%	180
	21st to end	Day	15% 7% 31% 27% 16% 4	198
January	1st to 10th	Night	16% 9% 31% 33% 10% 1	950
	11th to 20th	Night	17% 9% 26% 34% 12% 2	915
	21st to end	Night	13% 8% 26% 32% 18% 4	990
February	1st to 10th	Night	8% 7% 29% 38% 17% 1	900
	11th to 20th	Night	12% 6% 32% 33% 14% 3	752
	21st to end	Night	8% 7% 25% 37% 20% 4	592
March	1st to 10th	Night	14% 6% 28% 34% 15% 2	720
	11th to 20th	Night	11% 9% 36% 32% 11% 2	720
	21st to end	Night	14% 9% 30% 32% 13% 2	752
April	1st to 10th	Night	17% 7% 34% 29% 12% 1	540
	11th to 20th	Night	16% 6% 30% 33% 13% 2	533
	21st to end	Night	16% 7% 29% 32% 14% 1	540
May	1st to 10th	Night	22% 9% 27% 31% 11% 1	437
	11th to 20th	Night	19% 9% 34% 27% 10%	354
	21st to end	Night	23% 11% 33% 28% 6%	389
June	1st to 10th	Night	21% 7% 32% 28% 12%	360
	11th to 20th	Night	19% 6% 31% 33% 10% 1	360
	21st to end	Night	18% 7% 29% 35% 11%	360
July	1st to 10th	Night	20% 8% 27% 32% 13%	350
	11th to 20th	Night	12% 4 33% 38% 13%	348
	21st to end	Night	18% 4 27% 34% 17% 1	394
August	1st to 10th	Night	18% 4 17% 43% 17% 1	509
	11th to 20th	Night	19% 5% 24% 34% 16% 1	534
	21st to end	Night	19% 6% 24% 32% 16% 2	594
September	1st to 10th	Night	20% 5% 30% 33% 11% 1	542
	11th to 20th	Night	26% 8% 27% 29% 9%	720
	21st to end	Night	26% 8% 27% 29% 9% 1	720
October	1st to 10th	Night	28% 9% 32% 23% 7% 1	720
	11th to 20th	Night	32% 8% 27% 21% 11% 1	720
	21st to end	Night	24% 9% 30% 24% 11% 2	792
November	1st to 10th	Night	30% 10% 28% 22% 9% 1	740
	11th to 20th	Night	26% 11% 30% 23% 9% 1	897
	21st to end	Night	26% 13% 31% 21% 8% 1	950
December	1st to 10th	Night	16% 11% 34% 26% 11% 2	950
	11th to 20th	Night	16% 9% 29% 28% 16% 2	950
	21st to end	Night	20% 8% 32% 24% 12% 5%	1045

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