Bella Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bella Vista clear sky chart from 2005-11-06 to 2024-11-30.

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	12% 7% 2 6% 4 4 4 3 5% 7% 45%	101038
	Night	12% 7% 2 5% 3 3 3 3 5% 6% 50%	98642
Transparency	Day	20% 47% 6% 14% 11% 2	104689
	Night	19% 47% 6% 14% 12% 3	103131
Seeing	Day	16% 12% 29% 26% 14% 3	15565
	Night	16% 11% 31% 28% 12% 1	25408

By Month

Percentage Cloud Cover SE (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	14% 12% 4 5% 3 3 3 2 4 5% 45%	2847
	11th to 20th	Day	9% 8% 3 7% 4 3 3 3 4 5% 50%	2850
	21st to end	Day	22% 11% 3 5% 3 2 3 2 3 5% 42%	3135
February	1st to 10th	Day	16% 11% 4 7% 5% 4 3 2 4 5% 39%	1710
	11th to 20th	Day	15% 10% 3 7% 4 3 3 2 4 5% 44%	1666
	21st to end	Day	17% 9% 3 6% 3 4 4 3 5% 5% 41%	1704
March	1st to 10th	Day	16% 7% 3 5% 3 3 3 3 4 5% 48%	3436
	11th to 20th	Day	13% 8% 2 5% 4 3 4 4 4 6% 49%	3480
	21st to end	Day	18% 10% 3 8% 5% 4 4 3 5% 6% 35%	3814
April	1st to 10th	Day	14% 7% 2 6% 4 4 3 3 6% 8% 43%	2194
	11th to 20th	Day	17% 8% 2 7% 4 4 4 3 5% 6% 40%	2254
	21st to end	Day	20% 9% 3 7% 5% 4 3 3 4 5% 38%	2294
May	1st to 10th	Day	20% 9% 3 7% 5% 4 4 3 5% 6% 35%	4082
	11th to 20th	Day	13% 7% 3 7% 5% 5% 4 4 6% 6% 40%	4082
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	4477
June	1st to 10th	Day	9% 5% 2 5% 5% 5% 4 5% 7% 10% 45%	2470
	11th to 20th	Day	8% 4 2 5% 5% 4 5% 4 6% 9% 47%	2470
	21st to end	Day	4 3 2 3 4 4 4 4 7% 9% 54%	2470
July	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 5% 8% 10% 40%	4120
	11th to 20th	Day	5% 4 2 5% 4 4 5% 4 7% 10% 49%	4120
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 9% 11% 42%	4465
August	1st to 10th	Day	5% 3 1 5% 3 4 4 4 5% 8% 57%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 45%	4009
	21st to end	Day	4 4 2 5% 4 4 5% 4 5% 8% 55%	4180
September	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 4 6% 53%	2280
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 6% 8% 46%	2119
	21st to end	Day	7% 5% 2 5% 4 4 4 4 5% 7% 54%	2065
October	1st to 10th	Day	10% 4 2 4 4 4 3 3 5% 6% 55%	1900
	11th to 20th	Day	13% 5% 2 4 2 3 2 2 3 6% 58%	1900
	21st to end	Day	18% 6% 2 5% 3 2 2 2 3 5% 50%	2090
November	1st to 10th	Day	11% 6% 2 3 3 3 3 2 4 6% 55%	1958
	11th to 20th	Day	13% 8% 2 5% 3 3 3 3 4 5% 51%	1934
	21st to end	Day	17% 9% 2 5% 3 2 3 3 3 6% 48%	1677
December	1st to 10th	Day	14% 8% 3 6% 4 3 3 3 5% 5% 45%	1520
	11th to 20th	Day	14% 12% 3 7% 4 4 4 2 4 4 43%	2027
	21st to end	Day	16% 17% 6% 6% 4 4 4 3 5% 6% 29%	3135
January	1st to 10th	Night	12% 9% 4 8% 4 3 4 2 5% 5% 42%	4108
	11th to 20th	Night	11% 6% 2 8% 3 4 5% 3 4 5% 48%	4120
	21st to end	Night	21% 11% 4 6% 2 2 2 2 3 4 42%	4532
February	1st to 10th	Night	15% 11% 3 6% 4 3 4 3 6% 6% 41%	2470
	11th to 20th	Night	14% 9% 4 6% 3 3 3 2 3 5% 47%	2403
	21st to end	Night	16% 9% 2 6% 4 3 4 3 4 4 45%	1763
March	1st to 10th	Night	15% 9% 2 5% 4 3 3 3 4 5% 46%	3419
	11th to 20th	Night	12% 7% 2 5% 4 3 3 3 5% 6% 50%	3480
	21st to end	Night	14% 8% 3 7% 5% 4 4 3 5% 6% 41%	3817
April	1st to 10th	Night	13% 7% 1 5% 3 4 3 3 5% 5% 51%	1986
	11th to 20th	Night	13% 6% 2 6% 4 3 4 3 5% 7% 47%	1875
	21st to end	Night	19% 6% 3 6% 4 3 4 3 4 6% 43%	1881
May	1st to 10th	Night	13% 7% 3 6% 4 4 3 3 4 8% 44%	2823
	11th to 20th	Night	13% 7% 3 6% 5% 3 4 4 5% 7% 43%	2823
	21st to end	Night	12% 7% 2 6% 3 4 4 3 6% 9% 43%	3090
June	1st to 10th	Night	6% 4 2 4 5% 3 3 3 7% 9% 55%	1710
	11th to 20th	Night	5% 4 1 4 3 3 4 4 6% 11% 55%	1710
	21st to end	Night	2 3 1 4 3 3 4 4 6% 8% 63%	1710
July	1st to 10th	Night	9% 5% 2 5% 3 3 4 3 5% 9% 52%	2850
	11th to 20th	Night	4 3 1 3 3 3 4 4 5% 8% 64%	2850
	21st to end	Night	6% 3 2 6% 4 4 4 4 7% 10% 52%	3098
August	1st to 10th	Night	3 2 1 3 3 4 4 4 7% 10% 60%	2836
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 8% 52%	2828
	21st to end	Night	3 3 1 3 3 3 3 4 5% 8% 63%	3476
September	1st to 10th	Night	9% 3 2 4 3 3 4 2 5% 7% 58%	1900
	11th to 20th	Night	9% 5% 2 6% 3 3 3 3 5% 8% 53%	2057
	21st to end	Night	8% 4 2 5% 3 3 3 3 5% 7% 57%	2095
October	1st to 10th	Night	6% 3 1 4 3 3 3 2 5% 8% 62%	2280
	11th to 20th	Night	13% 5% 2 4 2 2 3 3 4 5% 57%	2280
	21st to end	Night	16% 7% 2 5% 3 2 3 2 3 5% 52%	2508
November	1st to 10th	Night	12% 5% 1 4 3 3 3 3 3 5% 60%	2340
	11th to 20th	Night	10% 7% 2 4 2 3 3 3 4 5% 56%	2464
	21st to end	Night	15% 7% 2 4 2 3 3 3 4 5% 53%	2712
December	1st to 10th	Night	14% 8% 3 6% 3 3 3 3 4 6% 47%	2660
	11th to 20th	Night	15% 9% 3 6% 4 3 3 3 4 4 44%	3156
	21st to end	Night	17% 15% 7% 7% 4 3 3 2 3 4 35%	4532

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	31% 36% 2 16% 14% 1	2848
	11th to 20th	Day	23% 37% 10% 18% 8% 4	2850
	21st to end	Day	29% 39% 4 11% 12% 4	3135
February	1st to 10th	Day	17% 64% 4 9% 5% 2	1710
	11th to 20th	Day	15% 64% 5% 9% 6% 1	1675
	21st to end	Day	16% 65% 2 6% 7% 4	1704
March	1st to 10th	Day	23% 42% 3 13% 12% 7%	3436
	11th to 20th	Day	17% 41% 8% 16% 15% 2	3480
	21st to end	Day	30% 42% 5% 16% 7%	3814
April	1st to 10th	Day	15% 65% 5% 8% 5% 1	2194
	11th to 20th	Day	17% 67% 4 7% 5%	2254
	21st to end	Day	18% 65% 3 8% 6% 1	2294
May	1st to 10th	Day	30% 42% 5% 13% 9% 1	4120
	11th to 20th	Day	26% 43% 7% 16% 8%	4086
	21st to end	Day	28% 42% 7% 13% 10% 1	4489
June	1st to 10th	Day	12% 67% 7% 9% 5% 1	2470
	11th to 20th	Day	12% 65% 6% 10% 5% 1	2470
	21st to end	Day	10% 64% 7% 13% 7%	2470
July	1st to 10th	Day	24% 39% 13% 16% 8% 2	4056
	11th to 20th	Day	18% 38% 8% 24% 12%	4051
	21st to end	Day	19% 38% 17% 20% 7%	4325
August	1st to 10th	Day	14% 38% 10% 19% 17% 3	4090
	11th to 20th	Day	22% 40% 12% 17% 9%	4048
	21st to end	Day	17% 39% 8% 29% 7%	4179
September	1st to 10th	Day	10% 60% 7% 12% 8% 4	2280
	11th to 20th	Day	15% 61% 5% 11% 8%	2119
	21st to end	Day	15% 60% 5% 12% 8%	2065
October	1st to 10th	Day	8% 37% 3 7% 30% 16%	3160
	11th to 20th	Day	7% 36% 2 11% 30% 13%	3140
	21st to end	Day	15% 36% 5% 21% 19% 4	3428
November	1st to 10th	Day	16% 55% 3 11% 11% 4	1958
	11th to 20th	Day	16% 56% 3 9% 10% 6%	1934
	21st to end	Day	18% 56% 3 12% 10% 1	1677
December	1st to 10th	Day	18% 59% 2 12% 8% 1	1520
	11th to 20th	Day	25% 47% 1 9% 16% 2	2025
	21st to end	Day	43% 38% 3 9% 6% 1	3135
January	1st to 10th	Night	32% 37% 5% 13% 12% 1	4108
	11th to 20th	Night	26% 38% 9% 13% 13% 1	4120
	21st to end	Night	33% 39% 7% 8% 12% 2	4532
February	1st to 10th	Night	15% 65% 4 9% 5% 2	2470
	11th to 20th	Night	15% 64% 3 10% 7% 1	2404
	21st to end	Night	15% 64% 3 6% 9% 3	1763
March	1st to 10th	Night	27% 42% 5% 11% 10% 6%	3419
	11th to 20th	Night	18% 42% 5% 20% 13% 2	3480
	21st to end	Night	25% 42% 7% 17% 8% 1	3817
April	1st to 10th	Night	13% 65% 4 9% 8% 1	1986
	11th to 20th	Night	13% 66% 4 9% 6% 1	1875
	21st to end	Night	16% 65% 4 8% 6% 1	1881
May	1st to 10th	Night	24% 42% 7% 14% 9% 3	2850
	11th to 20th	Night	26% 43% 6% 18% 7%	2824
	21st to end	Night	22% 44% 8% 17% 9%	3099
June	1st to 10th	Night	9% 66% 5% 10% 8% 2	1710
	11th to 20th	Night	8% 65% 6% 12% 8%	1710
	21st to end	Night	8% 64% 7% 14% 8%	1710
July	1st to 10th	Night	22% 38% 13% 15% 8% 4	2805
	11th to 20th	Night	11% 36% 7% 32% 15%	2796
	21st to end	Night	16% 37% 16% 23% 8%	2999
August	1st to 10th	Night	9% 39% 10% 22% 18% 1	2826
	11th to 20th	Night	20% 39% 12% 18% 9% 1	2855
	21st to end	Night	11% 38% 8% 30% 12% 1	3476
September	1st to 10th	Night	8% 60% 6% 14% 9% 3	1900
	11th to 20th	Night	11% 60% 5% 13% 10% 2	2057
	21st to end	Night	14% 60% 6% 10% 9% 1	2095
October	1st to 10th	Night	6% 37% 3 6% 29% 19%	3800
	11th to 20th	Night	10% 36% 3 11% 24% 17%	3779
	21st to end	Night	17% 37% 4 22% 16% 4	4120
November	1st to 10th	Night	16% 56% 3 9% 12% 4	2340
	11th to 20th	Night	13% 57% 3 9% 13% 6%	2464
	21st to end	Night	17% 57% 3 11% 13% 1	2712
December	1st to 10th	Night	17% 59% 3 8% 11% 1	2660
	11th to 20th	Night	21% 49% 2 12% 13% 2	3157
	21st to end	Night	41% 37% 4 9% 8% 1	4532

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	26% 19% 39% 13% 3	270
	11th to 20th	Day	25% 24% 40% 10% 1	270
	21st to end	Day	23% 26% 35% 11% 4	297
February	1st to 10th	Day	29% 24% 34% 11% 1	270
	11th to 20th	Day	31% 27% 29% 11% 1	270
	21st to end	Day	35% 27% 30% 7% 1	225
March	1st to 10th	Day	26% 25% 32% 15% 2	270
	11th to 20th	Day	31% 21% 36% 12%	270
	21st to end	Day	31% 26% 33% 7% 3	297
April	1st to 10th	Day	24% 26% 33% 13% 5%	374
	11th to 20th	Day	26% 20% 34% 15% 4	452
	21st to end	Day	26% 20% 32% 17% 4	474
May	1st to 10th	Day	21% 16% 40% 19% 5%	653
	11th to 20th	Day	17% 13% 34% 25% 9% 2	675
	21st to end	Day	14% 12% 34% 23% 13% 4	734
June	1st to 10th	Day	8% 5% 24% 37% 21% 4	680
	11th to 20th	Day	8% 4 25% 39% 21% 3	680
	21st to end	Day	4 4 33% 35% 20% 3	680
July	1st to 10th	Day	10% 4 18% 32% 30% 7%	671
	11th to 20th	Day	5% 3 19% 39% 28% 6%	668
	21st to end	Day	8% 2 14% 36% 31% 9%	739
August	1st to 10th	Day	9% 3 19% 40% 26% 4	676
	11th to 20th	Day	11% 3 17% 36% 30% 4	646
	21st to end	Day	8% 1 16% 36% 31% 9%	539
September	1st to 10th	Day	10% 3 17% 37% 27% 7%	490
	11th to 20th	Day	9% 1 24% 43% 16% 5%	329
	21st to end	Day	8% 9% 32% 31% 16% 4	300
October	1st to 10th	Day	9% 10% 34% 29% 14% 4	300
	11th to 20th	Day	16% 14% 41% 22% 7%	300
	21st to end	Day	28% 17% 35% 16% 4 1	330
November	1st to 10th	Day	18% 17% 40% 19% 5% 1	300
	11th to 20th	Day	23% 18% 34% 19% 5% 2	300
	21st to end	Day	29% 16% 33% 17% 4	299
December	1st to 10th	Day	23% 21% 35% 14% 5% 1	270
	11th to 20th	Day	24% 24% 34% 14% 4	270
	21st to end	Day	27% 24% 38% 9% 2	297
January	1st to 10th	Night	20% 20% 33% 23% 4	950
	11th to 20th	Night	20% 21% 38% 17% 4	950
	21st to end	Night	18% 21% 36% 21% 3	1045
February	1st to 10th	Night	22% 17% 40% 18% 3	950
	11th to 20th	Night	22% 20% 39% 17% 2	929
	21st to end	Night	26% 19% 34% 20% 2	507
March	1st to 10th	Night	20% 15% 39% 23% 3	570
	11th to 20th	Night	24% 15% 34% 24% 3	570
	21st to end	Night	23% 17% 37% 17% 5%	627
April	1st to 10th	Night	18% 17% 39% 23% 3	570
	11th to 20th	Night	17% 16% 36% 25% 7%	563
	21st to end	Night	23% 11% 40% 18% 8%	570
May	1st to 10th	Night	16% 7% 41% 29% 7%	570
	11th to 20th	Night	16% 6% 32% 31% 13% 1	561
	21st to end	Night	13% 8% 32% 29% 18% 1	617
June	1st to 10th	Night	8% 4 18% 42% 28%	570
	11th to 20th	Night	5% 3 27% 43% 20% 1	570
	21st to end	Night	3 1 26% 47% 21% 2	570
July	1st to 10th	Night	7% 1 14% 40% 34% 4	555
	11th to 20th	Night	5% 1 13% 43% 33% 5%	552
	21st to end	Night	5% 2 12% 44% 32% 5%	624
August	1st to 10th	Night	5% 2 14% 42% 35% 2	567
	11th to 20th	Night	9% 2 14% 44% 27% 4	564
	21st to end	Night	4 1 16% 38% 36% 5%	627
September	1st to 10th	Night	9% 1 17% 41% 29% 2	570
	11th to 20th	Night	12% 1 16% 42% 25% 3	570
	21st to end	Night	9% 4 26% 36% 22% 3	575
October	1st to 10th	Night	7% 4 30% 34% 22% 4	760
	11th to 20th	Night	16% 8% 36% 29% 10%	760
	21st to end	Night	21% 10% 34% 25% 9% 1	836
November	1st to 10th	Night	16% 11% 40% 24% 9% 1	780
	11th to 20th	Night	17% 14% 36% 25% 8%	864
	21st to end	Night	21% 15% 35% 21% 8%	1000
December	1st to 10th	Night	20% 15% 37% 23% 4	950
	11th to 20th	Night	24% 15% 33% 25% 3	950
	21st to end	Night	22% 20% 36% 19% 3	1045

Page generated at 2024-11-27 16:30:53. Version ac07

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