Victoria Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victoria Beach clear sky chart from 2005-11-06 to 2025-02-25.

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 9% 5% 5% 5% 4 6% 7% 34%	108401
	Night	10% 11% 4 11% 6% 5% 5% 4 6% 6% 30%	110475
Transparency	Day	47% 5% 16% 24% 7%	111825
	Night	53% 5% 13% 21% 8% 1	115211
Seeing	Day	15% 4 20% 34% 22% 5%	16626
	Night	17% 4 23% 35% 18% 3	26764

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	4 17% 8% 15% 8% 8% 7% 6% 6% 6% 16%	3178
	11th to 20th	Day	5% 11% 5% 16% 9% 8% 10% 8% 10% 7% 12%	3152
	21st to end	Day	5% 16% 7% 17% 8% 8% 7% 4 7% 6% 14%	3842
February	1st to 10th	Day	7% 12% 5% 13% 7% 6% 8% 5% 8% 8% 20%	1708
	11th to 20th	Day	8% 9% 4 10% 6% 6% 8% 5% 6% 10% 28%	1754
	21st to end	Day	6% 13% 4 12% 8% 5% 7% 5% 7% 8% 27%	1483
March	1st to 10th	Day	8% 11% 4 13% 7% 5% 5% 5% 7% 8% 27%	3221
	11th to 20th	Day	8% 10% 4 11% 7% 5% 6% 4 6% 7% 33%	3480
	21st to end	Day	7% 10% 4 10% 6% 6% 5% 4 5% 5% 38%	3814
April	1st to 10th	Day	9% 10% 3 7% 5% 4 4 4 5% 7% 41%	2328
	11th to 20th	Day	11% 9% 3 6% 5% 5% 5% 4 7% 7% 39%	2442
	21st to end	Day	13% 7% 3 8% 4 5% 4 5% 6% 8% 37%	2470
May	1st to 10th	Day	12% 8% 3 6% 5% 4 4 4 6% 8% 41%	4348
	11th to 20th	Day	18% 8% 3 6% 5% 4 5% 3 5% 6% 36%	4637
	21st to end	Day	19% 7% 2 7% 4 4 4 3 5% 5% 38%	5173
June	1st to 10th	Day	16% 7% 2 6% 4 4 4 4 6% 7% 40%	2850
	11th to 20th	Day	14% 6% 2 6% 4 5% 4 4 7% 7% 39%	2850
	21st to end	Day	12% 6% 3 6% 4 5% 4 4 7% 9% 39%	2850
July	1st to 10th	Day	11% 5% 2 6% 4 4 6% 4 6% 9% 44%	4750
	11th to 20th	Day	8% 4 2 4 3 3 4 3 6% 9% 53%	4750
	21st to end	Day	6% 4 2 5% 3 4 5% 4 6% 9% 53%	5151
August	1st to 10th	Day	9% 4 2 5% 4 5% 5% 4 6% 9% 46%	4343
	11th to 20th	Day	11% 4 2 5% 4 4 5% 4 6% 9% 48%	4041
	21st to end	Day	16% 6% 2 6% 3 3 4 4 5% 8% 43%	4532
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 5% 8% 46%	2371
	11th to 20th	Day	16% 8% 3 6% 5% 5% 4 4 6% 8% 35%	2104
	21st to end	Day	13% 8% 3 7% 5% 3 4 4 5% 7% 40%	2090
October	1st to 10th	Day	20% 13% 3 7% 4 4 4 4 5% 7% 29%	1911
	11th to 20th	Day	16% 15% 4 7% 6% 4 4 4 5% 7% 28%	1872
	21st to end	Day	18% 16% 5% 12% 5% 6% 5% 3 5% 5% 20%	1857
November	1st to 10th	Day	17% 15% 4 13% 7% 5% 4 3 5% 5% 22%	1567
	11th to 20th	Day	11% 19% 6% 18% 8% 4 4 3 4 4 20%	1600
	21st to end	Day	12% 17% 5% 15% 10% 6% 4 3 4 5% 18%	1455
December	1st to 10th	Day	10% 17% 8% 19% 13% 9% 4 3 4 3 9%	2290
	11th to 20th	Day	9% 13% 5% 13% 8% 6% 7% 6% 7% 7% 19%	2639
	21st to end	Day	7% 14% 8% 17% 8% 8% 5% 5% 5% 6% 17%	3498
January	1st to 10th	Night	5% 13% 7% 16% 8% 9% 7% 6% 5% 5% 17%	6787
	11th to 20th	Night	5% 13% 7% 15% 11% 9% 9% 8% 6% 4 14%	6753
	21st to end	Night	7% 17% 7% 14% 7% 6% 6% 5% 6% 6% 19%	7135
February	1st to 10th	Night	7% 14% 5% 10% 7% 6% 7% 6% 6% 6% 26%	2690
	11th to 20th	Night	6% 10% 4 9% 5% 5% 5% 7% 8% 8% 32%	2533
	21st to end	Night	5% 12% 5% 12% 6% 6% 6% 5% 5% 6% 33%	2081
March	1st to 10th	Night	10% 12% 3 10% 6% 5% 6% 5% 7% 7% 30%	3613
	11th to 20th	Night	5% 8% 3 8% 5% 5% 5% 4 6% 7% 42%	3479
	21st to end	Night	9% 13% 4 8% 6% 5% 4 3 5% 6% 38%	3817
April	1st to 10th	Night	11% 8% 2 7% 4 4 5% 5% 5% 8% 41%	1849
	11th to 20th	Night	13% 9% 3 7% 5% 4 5% 4 6% 7% 36%	1689
	21st to end	Night	9% 8% 3 9% 4 5% 6% 5% 7% 7% 36%	1710
May	1st to 10th	Night	16% 9% 3 7% 4 4 4 4 6% 6% 37%	2601
	11th to 20th	Night	18% 7% 3 6% 4 3 5% 3 5% 8% 38%	2266
	21st to end	Night	17% 9% 3 7% 4 4 4 4 5% 6% 38%	2414
June	1st to 10th	Night	14% 8% 3 7% 4 5% 6% 4 7% 7% 36%	1330
	11th to 20th	Night	15% 6% 2 6% 3 4 5% 4 6% 8% 41%	1330
	21st to end	Night	12% 5% 2 5% 3 5% 3 5% 8% 12% 39%	1330
July	1st to 10th	Night	10% 4 2 4 3 3 4 4 6% 9% 51%	2220
	11th to 20th	Night	8% 3 1 4 3 4 5% 4 5% 8% 54%	2220
	21st to end	Night	5% 3 1 4 4 4 5% 3 7% 9% 54%	2414
August	1st to 10th	Night	11% 4 2 6% 4 4 5% 4 6% 8% 46%	2594
	11th to 20th	Night	9% 3 1 4 4 4 4 4 7% 9% 51%	2798
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 5% 9% 43%	3135
September	1st to 10th	Night	13% 6% 2 6% 4 4 3 3 5% 8% 47%	1808
	11th to 20th	Night	15% 8% 2 6% 4 4 4 5% 5% 7% 40%	2072
	21st to end	Night	16% 7% 3 7% 5% 4 4 4 5% 8% 38%	2090
October	1st to 10th	Night	18% 12% 3 7% 5% 3 4 4 4 7% 33%	2249
	11th to 20th	Night	17% 15% 4 8% 5% 4 5% 3 5% 6% 28%	2308
	21st to end	Night	18% 16% 5% 9% 5% 4 4 4 4 5% 25%	2741
November	1st to 10th	Night	15% 17% 5% 12% 6% 5% 5% 3 4 5% 24%	2731
	11th to 20th	Night	13% 19% 7% 16% 8% 5% 3 3 5% 5% 18%	2800
	21st to end	Night	13% 16% 8% 15% 10% 6% 4 3 4 4 16%	2940
December	1st to 10th	Night	11% 22% 8% 16% 12% 7% 3 3 4 3 11%	4900
	11th to 20th	Night	7% 13% 5% 14% 8% 5% 8% 6% 5% 6% 22%	5568
	21st to end	Night	7% 12% 6% 19% 9% 6% 6% 4 5% 5% 21%	7480

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	67% 4 10% 13% 5%	3179
	11th to 20th	Day	66% 3 9% 18% 4	3180
	21st to end	Day	68% 4 11% 13% 4	3842
February	1st to 10th	Day	58% 5% 14% 15% 7% 1	1708
	11th to 20th	Day	50% 4 16% 22% 8%	1763
	21st to end	Day	53% 6% 13% 19% 9%	1483
March	1st to 10th	Day	52% 7% 14% 21% 5%	3223
	11th to 20th	Day	49% 6% 13% 22% 9%	3480
	21st to end	Day	45% 7% 12% 28% 7% 1	3814
April	1st to 10th	Day	43% 5% 13% 25% 13% 1	2328
	11th to 20th	Day	43% 5% 11% 23% 16% 2	2442
	21st to end	Day	44% 6% 15% 26% 9% 1	2470
May	1st to 10th	Day	40% 6% 14% 29% 12% 1	4360
	11th to 20th	Day	47% 6% 10% 22% 12% 2	4641
	21st to end	Day	46% 8% 11% 24% 11% 1	5173
June	1st to 10th	Day	42% 7% 14% 26% 11% 1	2850
	11th to 20th	Day	42% 8% 15% 23% 11% 1	2850
	21st to end	Day	40% 8% 19% 25% 8%	2850
July	1st to 10th	Day	38% 5% 23% 27% 8%	4676
	11th to 20th	Day	28% 5% 24% 37% 6%	4669
	21st to end	Day	29% 4 24% 35% 8%	4988
August	1st to 10th	Day	34% 4 21% 32% 8%	4326
	11th to 20th	Day	34% 5% 24% 33% 4	4080
	21st to end	Day	40% 4 24% 28% 4	4531
September	1st to 10th	Day	36% 6% 20% 30% 7%	2371
	11th to 20th	Day	46% 6% 20% 25% 3	2104
	21st to end	Day	43% 6% 17% 27% 7%	2090
October	1st to 10th	Day	46% 4 17% 27% 6%	3171
	11th to 20th	Day	47% 5% 13% 25% 10%	3090
	21st to end	Day	57% 4 20% 18% 2	3043
November	1st to 10th	Day	63% 6% 15% 13% 3 1	1567
	11th to 20th	Day	68% 5% 13% 11% 2	1600
	21st to end	Day	69% 4 15% 11% 1	1455
December	1st to 10th	Day	81% 4 7% 6% 2	2290
	11th to 20th	Day	61% 5% 14% 14% 6%	2640
	21st to end	Day	65% 7% 9% 14% 5%	3498
January	1st to 10th	Night	66% 4 9% 12% 8%	6787
	11th to 20th	Night	69% 4 7% 16% 4	6800
	21st to end	Night	65% 5% 11% 13% 6%	7135
February	1st to 10th	Night	56% 5% 12% 17% 9% 1	2690
	11th to 20th	Night	45% 6% 17% 23% 9%	2534
	21st to end	Night	52% 4 11% 22% 11%	2081
March	1st to 10th	Night	50% 7% 11% 22% 9%	3624
	11th to 20th	Night	37% 6% 16% 27% 13% 1	3480
	21st to end	Night	47% 5% 9% 26% 11% 1	3817
April	1st to 10th	Night	41% 4 9% 24% 17% 3	1849
	11th to 20th	Night	47% 5% 8% 21% 16% 3	1689
	21st to end	Night	43% 5% 10% 25% 15% 1	1710
May	1st to 10th	Night	46% 6% 8% 27% 13%	2608
	11th to 20th	Night	44% 5% 12% 27% 10% 2	2267
	21st to end	Night	46% 5% 12% 23% 12% 1	2414
June	1st to 10th	Night	45% 7% 13% 24% 11% 1	1330
	11th to 20th	Night	41% 5% 15% 25% 12% 2	1330
	21st to end	Night	36% 7% 20% 27% 9% 1	1330
July	1st to 10th	Night	30% 5% 20% 35% 10%	2185
	11th to 20th	Night	29% 5% 19% 39% 8% 1	2178
	21st to end	Night	26% 4 23% 36% 10% 1	2337
August	1st to 10th	Night	36% 4 15% 33% 11%	2587
	11th to 20th	Night	29% 4 27% 33% 6%	2825
	21st to end	Night	39% 4 21% 29% 7%	3135
September	1st to 10th	Night	36% 5% 17% 31% 10%	1808
	11th to 20th	Night	42% 6% 18% 25% 8% 1	2072
	21st to end	Night	43% 5% 15% 27% 9%	2090
October	1st to 10th	Night	42% 4 14% 29% 11%	3756
	11th to 20th	Night	48% 4 14% 25% 8%	3831
	21st to end	Night	53% 4 17% 23% 3	4515
November	1st to 10th	Night	62% 7% 14% 13% 4	2731
	11th to 20th	Night	69% 6% 11% 9% 4	2800
	21st to end	Night	72% 4 13% 9% 2	2940
December	1st to 10th	Night	79% 4 10% 6% 2	4900
	11th to 20th	Night	62% 4 12% 12% 10%	5566
	21st to end	Night	63% 4 9% 17% 6%	7480

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% 3 30% 32% 19% 5%	300
	11th to 20th	Day	9% 6% 20% 42% 20% 2	300
	21st to end	Day	16% 4 22% 35% 18% 4	330
February	1st to 10th	Day	14% 4 28% 35% 15% 4	300
	11th to 20th	Day	10% 5% 25% 33% 20% 6%	300
	21st to end	Day	8% 3 24% 39% 24% 2	237
March	1st to 10th	Day	10% 5% 21% 37% 24% 3	270
	11th to 20th	Day	13% 7% 23% 36% 17% 4	270
	21st to end	Day	16% 3 22% 34% 21% 4	297
April	1st to 10th	Day	11% 4 19% 41% 21% 4	508
	11th to 20th	Day	17% 4 22% 34% 20% 4	640
	21st to end	Day	14% 3 19% 38% 21% 4	650
May	1st to 10th	Day	13% 3 20% 36% 24% 3	653
	11th to 20th	Day	17% 5% 16% 33% 23% 6%	675
	21st to end	Day	19% 4 15% 29% 27% 5%	734
June	1st to 10th	Day	18% 4 16% 34% 21% 7%	680
	11th to 20th	Day	16% 3 22% 33% 23% 4	680
	21st to end	Day	13% 4 14% 35% 26% 8%	680
July	1st to 10th	Day	10% 4 17% 34% 26% 11%	671
	11th to 20th	Day	10% 5% 17% 31% 28% 9%	668
	21st to end	Day	8% 2 15% 34% 31% 10%	739
August	1st to 10th	Day	10% 3 17% 34% 27% 8%	676
	11th to 20th	Day	12% 3 13% 30% 30% 12%	665
	21st to end	Day	17% 4 16% 31% 27% 6%	748
September	1st to 10th	Day	14% 3 23% 34% 22% 4	581
	11th to 20th	Day	18% 7% 20% 38% 14% 4	314
	21st to end	Day	22% 6% 22% 34% 15% 1	300
October	1st to 10th	Day	22% 8% 22% 28% 17% 4	300
	11th to 20th	Day	16% 7% 25% 39% 12% 1	300
	21st to end	Day	28% 8% 21% 27% 13% 3	330
November	1st to 10th	Day	21% 7% 24% 31% 16% 1	300
	11th to 20th	Day	20% 7% 34% 27% 10% 2	300
	21st to end	Day	22% 8% 26% 36% 7% 1	300
December	1st to 10th	Day	15% 4 28% 35% 14% 4	300
	11th to 20th	Day	17% 6% 33% 33% 9% 2	300
	21st to end	Day	12% 4 22% 38% 18% 5%	330
January	1st to 10th	Night	13% 3 28% 34% 18% 3	1000
	11th to 20th	Night	14% 5% 24% 39% 16% 2	1000
	21st to end	Night	15% 4 25% 39% 15% 2	1100
February	1st to 10th	Night	13% 3 23% 41% 18% 2	1000
	11th to 20th	Night	10% 3 23% 39% 21% 4	979
	21st to end	Night	10% 3 26% 38% 21% 2	789
March	1st to 10th	Night	14% 3 22% 36% 22% 3	702
	11th to 20th	Night	13% 3 28% 39% 15% 2	570
	21st to end	Night	18% 4 21% 35% 18% 4	627
April	1st to 10th	Night	15% 2 25% 39% 16% 3	570
	11th to 20th	Night	16% 4 20% 37% 19% 3	563
	21st to end	Night	13% 2 22% 43% 18% 2	570
May	1st to 10th	Night	19% 3 22% 39% 15% 2	570
	11th to 20th	Night	17% 3 17% 38% 20% 4	561
	21st to end	Night	21% 3 17% 38% 19% 2	617
June	1st to 10th	Night	19% 2 16% 35% 23% 4	570
	11th to 20th	Night	18% 4 19% 33% 22% 3	570
	21st to end	Night	14% 3 11% 39% 29% 5%	570
July	1st to 10th	Night	8% 2 17% 38% 29% 6%	555
	11th to 20th	Night	10% 3 18% 37% 27% 6%	552
	21st to end	Night	9% 3 15% 34% 32% 7%	624
August	1st to 10th	Night	10% 4 17% 38% 28% 4	567
	11th to 20th	Night	10% 4 15% 35% 27% 9%	564
	21st to end	Night	17% 2 18% 35% 24% 3	627
September	1st to 10th	Night	17% 3 23% 35% 18% 4	570
	11th to 20th	Night	19% 4 23% 37% 16% 1	570
	21st to end	Night	19% 4 26% 34% 15% 2	570
October	1st to 10th	Night	25% 7% 26% 29% 13% 1	729
	11th to 20th	Night	24% 9% 24% 30% 11% 1	788
	21st to end	Night	28% 6% 26% 28% 10% 1	1045
November	1st to 10th	Night	24% 7% 28% 26% 14% 1	975
	11th to 20th	Night	21% 7% 31% 29% 9% 3	1000
	21st to end	Night	22% 6% 32% 32% 8% 1	1000
December	1st to 10th	Night	16% 4 26% 36% 16% 3	1000
	11th to 20th	Night	17% 5% 30% 37% 10% 2	1000
	21st to end	Night	16% 3 27% 33% 18% 3	1100

Page generated at 2025-02-22 05:51:36. Version ac07

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