Rio Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rio Vista clear sky chart from 2005-11-06 to 2024-10-25.

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	7% 4 1 3 2 2 3 2 4 5% 66%	101071
	Night	8% 4 1 4 3 3 3 2 4 6% 63%	97934
Transparency	Day	21% 4 8% 18% 25% 24%	100824
	Night	23% 5% 9% 18% 23% 21%	97769
Seeing	Day	7% 7% 24% 33% 21% 7%	15268
	Night	8% 5% 25% 39% 20% 3	24579

By Month

Percentage Cloud Cover SW (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	19% 10% 3 7% 4 5% 4 3 5% 6% 34%	2585
	11th to 20th	Day	18% 12% 3 8% 5% 4 3 2 4 5% 34%	2860
	21st to end	Day	21% 10% 3 8% 5% 5% 4 4 5% 6% 30%	3146
February	1st to 10th	Day	16% 6% 2 6% 5% 3 4 3 4 5% 45%	1710
	11th to 20th	Day	14% 6% 2 5% 4 4 4 4 6% 6% 46%	1768
	21st to end	Day	13% 4 2 5% 4 4 4 3 5% 6% 50%	1570
March	1st to 10th	Day	11% 8% 3 9% 6% 6% 6% 4 7% 6% 34%	3319
	11th to 20th	Day	10% 4 2 4 3 3 3 2 5% 6% 59%	3490
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	3930
April	1st to 10th	Day	12% 6% 2 4 4 3 3 3 6% 7% 49%	2280
	11th to 20th	Day	8% 4 1 4 3 3 4 3 5% 6% 60%	2249
	21st to end	Day	5% 3 1 3 3 2 3 3 4 8% 65%	2280
May	1st to 10th	Day	5% 2 1 2 1 1 1 2 3 4 77%	3889
	11th to 20th	Day	2 1 1 2 1 1 2 1 3 4 83%	4274
	21st to end	Day	2 1 1 2 1 2 2 2 3 5% 80%	4813
June	1st to 10th	Day	3 3 1 3 2 3 3 2 4 8% 69%	2660
	11th to 20th	Day	1 1 1 2 2 4 6% 82%	2660
	21st to end	Day	1 1 1 2 1 1 1 2 2 4 84%	2660
July	1st to 10th	Day	1 1 1 3 92%	4420
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 86%	4274
	21st to end	Day	1 1 1 2 4 89%	4455
August	1st to 10th	Day	1 1 2 1 1 2 3 4 5% 80%	4091
	11th to 20th	Day	1 1 1 1 1 1 2 4 89%	3798
	21st to end	Day	1 1 1 1 1 1 1 2 3 89%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2280
	11th to 20th	Day	2 2 1 2 2 2 2 2 4 5% 77%	2280
	21st to end	Day	2 2 1 2 2 2 2 1 3 5% 80%	2033
October	1st to 10th	Day	2 2 1 3 2 2 3 2 3 5% 75%	1900
	11th to 20th	Day	5% 2 1 3 2 2 4 3 4 5% 70%	1900
	21st to end	Day	5% 3 2 4 2 3 2 2 4 6% 67%	2025
November	1st to 10th	Day	7% 5% 2 3 3 4 4 2 5% 8% 57%	1769
	11th to 20th	Day	9% 7% 2 6% 5% 4 4 3 4 7% 49%	1710
	21st to end	Day	11% 5% 2 4 4 3 3 3 6% 6% 53%	1571
December	1st to 10th	Day	13% 8% 3 8% 4 3 3 3 4 6% 45%	1520
	11th to 20th	Day	25% 11% 4 8% 4 3 3 2 4 5% 30%	1928
	21st to end	Day	16% 9% 3 8% 5% 5% 4 4 6% 8% 31%	2794
January	1st to 10th	Night	13% 7% 3 8% 4 4 4 3 5% 6% 43%	4344
	11th to 20th	Night	21% 9% 3 8% 5% 4 4 3 5% 6% 33%	4110
	21st to end	Night	19% 8% 3 8% 4 4 4 4 5% 7% 35%	4521
February	1st to 10th	Night	15% 6% 3 5% 4 3 3 3 4 4 50%	2470
	11th to 20th	Night	11% 4 2 5% 3 4 3 4 5% 8% 51%	2299
	21st to end	Night	13% 4 1 4 3 3 3 3 4 6% 56%	1884
March	1st to 10th	Night	14% 7% 3 7% 5% 4 5% 3 5% 6% 41%	3552
	11th to 20th	Night	13% 4 1 4 2 3 2 2 3 5% 62%	3490
	21st to end	Night	11% 5% 2 6% 4 5% 4 4 5% 6% 47%	3721
April	1st to 10th	Night	9% 5% 1 4 3 4 3 3 5% 8% 55%	1900
	11th to 20th	Night	7% 4 1 3 3 3 3 2 4 7% 62%	1879
	21st to end	Night	4 3 1 2 2 2 3 3 5% 8% 68%	1900
May	1st to 10th	Night	2 1 2 1 2 2 2 3 5% 80%	3084
	11th to 20th	Night	2 1 1 1 1 1 1 3 4 84%	2619
	21st to end	Night	1 1 1 1 1 2 2 2 5% 84%	2762
June	1st to 10th	Night	3 2 3 2 3 2 2 4 7% 72%	1520
	11th to 20th	Night	1 1 1 1 2 1 3 4 86%	1520
	21st to end	Night	1 1 1 1 1 1 2 1 3 3 85%	1520
July	1st to 10th	Night	1 1 1 1 2 93%	2540
	11th to 20th	Night	1 1 1 1 1 1 1 1 2 3 86%	2687
	21st to end	Night	1 1 1 1 1 1 1 3 5% 84%	3109
August	1st to 10th	Night	2 1 1 2 1 2 2 2 3 7% 77%	2848
	11th to 20th	Night	1 1 1 1 3 5% 88%	3035
	21st to end	Night	1 1 1 1 1 1 1 1 2 4 87%	3498
September	1st to 10th	Night	1 1 1 1 1 1 3 6% 86%	1900
	11th to 20th	Night	2 2 1 2 1 2 2 2 4 6% 77%	1900
	21st to end	Night	1 1 2 2 2 2 1 3 5% 82%	2143
October	1st to 10th	Night	3 2 2 2 1 2 3 4 4 75%	2280
	11th to 20th	Night	3 2 1 2 2 2 2 3 4 7% 71%	2280
	21st to end	Night	4 2 3 2 2 3 2 5% 6% 70%	2436
November	1st to 10th	Night	7% 4 1 3 3 2 4 3 5% 9% 60%	2308
	11th to 20th	Night	8% 5% 2 4 3 3 3 4 5% 6% 57%	2470
	21st to end	Night	9% 4 1 4 3 3 3 3 5% 6% 58%	2607
December	1st to 10th	Night	14% 6% 2 6% 3 4 3 3 4 6% 48%	2660
	11th to 20th	Night	22% 7% 3 6% 5% 5% 4 3 6% 7% 32%	3276
	21st to end	Night	17% 6% 3 8% 5% 5% 5% 4 5% 6% 36%	4862

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	48% 9% 12% 22% 8% 1	2585
	11th to 20th	Day	53% 7% 10% 14% 13% 4	2860
	21st to end	Day	52% 8% 11% 16% 11% 3	3146
February	1st to 10th	Day	40% 5% 9% 21% 18% 6%	1710
	11th to 20th	Day	36% 6% 12% 19% 20% 6%	1777
	21st to end	Day	33% 6% 11% 24% 19% 7%	1570
March	1st to 10th	Day	45% 10% 12% 16% 15% 2	3319
	11th to 20th	Day	27% 5% 11% 29% 17% 11%	3490
	21st to end	Day	37% 9% 15% 24% 12% 3	3930
April	1st to 10th	Day	34% 6% 12% 23% 20% 6%	2280
	11th to 20th	Day	24% 5% 13% 26% 23% 7%	2252
	21st to end	Day	18% 5% 13% 29% 29% 6%	2280
May	1st to 10th	Day	12% 3 8% 31% 25% 22%	3889
	11th to 20th	Day	8% 2 5% 27% 42% 16%	4277
	21st to end	Day	8% 3 9% 36% 34% 9%	4814
June	1st to 10th	Day	15% 5% 11% 26% 31% 13%	2660
	11th to 20th	Day	6% 2 8% 21% 38% 25%	2660
	21st to end	Day	7% 1 3 11% 35% 42%	2660
July	1st to 10th	Day	2 1 2 5% 15% 75%	4351
	11th to 20th	Day	6% 1 3 8% 15% 67%	4199
	21st to end	Day	3 1 2 6% 28% 61%	4315
August	1st to 10th	Day	8% 2 3 8% 27% 52%	4076
	11th to 20th	Day	3 1 2 9% 41% 45%	3835
	21st to end	Day	5% 1 3 10% 38% 43%	4179
September	1st to 10th	Day	5% 1 3 8% 31% 52%	2280
	11th to 20th	Day	10% 3 7% 21% 40% 19%	2280
	21st to end	Day	10% 2 5% 18% 36% 29%	2033
October	1st to 10th	Day	13% 3 6% 17% 31% 29%	1900
	11th to 20th	Day	16% 4 9% 21% 25% 25%	1900
	21st to end	Day	20% 4 9% 21% 27% 19%	2025
November	1st to 10th	Day	26% 5% 10% 26% 22% 11%	1769
	11th to 20th	Day	35% 5% 11% 25% 19% 5%	1710
	21st to end	Day	30% 6% 12% 23% 23% 8%	1571
December	1st to 10th	Day	39% 6% 12% 19% 16% 7%	1520
	11th to 20th	Day	56% 6% 9% 13% 14% 2	1928
	21st to end	Day	47% 10% 14% 16% 11% 2	2794
January	1st to 10th	Night	37% 11% 17% 24% 9% 3	4344
	11th to 20th	Night	50% 8% 14% 12% 10% 6%	4110
	21st to end	Night	48% 8% 12% 15% 12% 4	4521
February	1st to 10th	Night	37% 4 8% 21% 21% 8%	2470
	11th to 20th	Night	31% 5% 12% 21% 23% 8%	2301
	21st to end	Night	30% 5% 10% 28% 21% 6%	1884
March	1st to 10th	Night	40% 11% 15% 14% 15% 3	3552
	11th to 20th	Night	27% 4 9% 27% 20% 13%	3490
	21st to end	Night	33% 9% 15% 25% 13% 4	3721
April	1st to 10th	Night	29% 5% 15% 22% 22% 8%	1900
	11th to 20th	Night	23% 6% 12% 28% 20% 11%	1879
	21st to end	Night	15% 5% 13% 30% 30% 7%	1900
May	1st to 10th	Night	10% 3 11% 28% 31% 18%	3084
	11th to 20th	Night	6% 2 6% 22% 41% 21%	2619
	21st to end	Night	6% 3 9% 39% 33% 10%	2762
June	1st to 10th	Night	13% 6% 11% 24% 32% 14%	1520
	11th to 20th	Night	6% 2 8% 19% 37% 28%	1520
	21st to end	Night	6% 2 3 11% 34% 44%	1520
July	1st to 10th	Night	2 1 1 5% 14% 76%	2500
	11th to 20th	Night	6% 2 3 6% 14% 69%	2639
	21st to end	Night	4 1 2 5% 24% 63%	3011
August	1st to 10th	Night	9% 1 2 9% 26% 53%	2839
	11th to 20th	Night	3 1 2 7% 37% 50%	3063
	21st to end	Night	6% 1 3 9% 34% 48%	3498
September	1st to 10th	Night	3 2 4 7% 30% 53%	1900
	11th to 20th	Night	9% 3 7% 20% 36% 25%	1900
	21st to end	Night	8% 2 5% 18% 34% 33%	2143
October	1st to 10th	Night	12% 3 8% 17% 27% 32%	2280
	11th to 20th	Night	14% 4 7% 20% 27% 28%	2280
	21st to end	Night	16% 4 7% 21% 29% 23%	2436
November	1st to 10th	Night	23% 5% 10% 26% 21% 16%	2308
	11th to 20th	Night	26% 5% 12% 25% 24% 8%	2470
	21st to end	Night	27% 4 9% 22% 27% 10%	2607
December	1st to 10th	Night	37% 6% 11% 20% 17% 10%	2660
	11th to 20th	Night	49% 7% 12% 14% 15% 3	3276
	21st to end	Night	46% 10% 12% 17% 12% 3	4862

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	30% 8% 19% 23% 15% 6%	213
	11th to 20th	Day	18% 7% 19% 22% 24% 10%	370
	21st to end	Day	15% 7% 18% 25% 22% 14%	407
February	1st to 10th	Day	18% 9% 19% 17% 24% 12%	370
	11th to 20th	Day	14% 13% 26% 20% 18% 8%	414
	21st to end	Day	12% 13% 20% 33% 17% 6%	382
March	1st to 10th	Day	16% 12% 27% 27% 13% 6%	460
	11th to 20th	Day	18% 11% 23% 22% 16% 9%	460
	21st to end	Day	13% 13% 30% 27% 14% 3	506
April	1st to 10th	Day	13% 13% 29% 23% 15% 7%	460
	11th to 20th	Day	11% 12% 32% 24% 14% 7%	452
	21st to end	Day	3 16% 28% 29% 17% 6%	460
May	1st to 10th	Day	6% 11% 30% 33% 15% 3	463
	11th to 20th	Day	5% 8% 32% 31% 22% 3	488
	21st to end	Day	4 8% 26% 36% 22% 5%	529
June	1st to 10th	Day	4 10% 28% 35% 18% 4	490
	11th to 20th	Day	1 9% 30% 44% 15% 1	490
	21st to end	Day	1 3 28% 44% 21% 2	490
July	1st to 10th	Day	1 2 23% 52% 21% 1	486
	11th to 20th	Day	1 20% 49% 29% 2	484
	21st to end	Day	1 1 21% 52% 22% 3	531
August	1st to 10th	Day	2 3 23% 49% 20% 3	487
	11th to 20th	Day	1 3 27% 45% 21% 4	477
	21st to end	Day	1 2 21% 47% 25% 5%	539
September	1st to 10th	Day	1 3 20% 41% 30% 6%	490
	11th to 20th	Day	3 8% 21% 40% 20% 8%	490
	21st to end	Day	1 5% 20% 36% 25% 13%	490
October	1st to 10th	Day	3 5% 23% 28% 26% 16%	490
	11th to 20th	Day	5% 6% 18% 26% 25% 19%	490
	21st to end	Day	7% 6% 18% 28% 25% 16%	514
November	1st to 10th	Day	8% 7% 21% 16% 28% 20%	365
	11th to 20th	Day	9% 6% 16% 25% 29% 16%	270
	21st to end	Day	11% 4 17% 30% 28% 11%	203
December	1st to 10th	Day	19% 8% 17% 22% 22% 12%	180
	11th to 20th	Day	20% 7% 18% 20% 27% 9%	180
	21st to end	Day	20% 10% 20% 24% 23% 4	198
January	1st to 10th	Night	18% 4 16% 34% 24% 4	760
	11th to 20th	Night	14% 5% 15% 36% 24% 6%	760
	21st to end	Night	16% 4 16% 33% 28% 3	836
February	1st to 10th	Night	18% 5% 15% 37% 22% 3	760
	11th to 20th	Night	13% 8% 20% 32% 23% 3	744
	21st to end	Night	13% 8% 23% 35% 18% 3	628
March	1st to 10th	Night	14% 8% 23% 33% 18% 2	760
	11th to 20th	Night	15% 9% 23% 33% 18% 1	760
	21st to end	Night	12% 8% 32% 33% 15%	836
April	1st to 10th	Night	10% 7% 33% 34% 16% 1	760
	11th to 20th	Night	8% 10% 36% 29% 15% 2	751
	21st to end	Night	5% 8% 38% 33% 15% 1	760
May	1st to 10th	Night	4 6% 36% 38% 14% 1	703
	11th to 20th	Night	3 4 33% 49% 12%	438
	21st to end	Night	2 7% 34% 48% 8%	411
June	1st to 10th	Night	4 4 39% 47% 6% 1	380
	11th to 20th	Night	1 5% 39% 46% 9%	380
	21st to end	Night	1 3 38% 47% 12%	380
July	1st to 10th	Night	1 34% 55% 10%	370
	11th to 20th	Night	1 1 26% 57% 14% 1	450
	21st to end	Night	2 24% 56% 16% 1	624
August	1st to 10th	Night	2 1 26% 51% 18% 1	567
	11th to 20th	Night	1 33% 50% 15%	697
	21st to end	Night	1 1 25% 53% 19%	836
September	1st to 10th	Night	1 2 27% 47% 23% 1	760
	11th to 20th	Night	2 3 28% 46% 18% 2	760
	21st to end	Night	2 3 23% 42% 27% 4	760
October	1st to 10th	Night	3 4 23% 39% 26% 5%	760
	11th to 20th	Night	3 5% 22% 36% 29% 4	760
	21st to end	Night	5% 3 18% 36% 30% 8%	812
November	1st to 10th	Night	6% 4 20% 34% 31% 5%	740
	11th to 20th	Night	9% 2 16% 38% 30% 5%	760
	21st to end	Night	10% 3 16% 38% 27% 5%	760
December	1st to 10th	Night	15% 5% 16% 37% 22% 5%	760
	11th to 20th	Night	22% 4 13% 34% 23% 3	760
	21st to end	Night	19% 7% 20% 33% 20% 1	836

Page generated at 2024-10-22 17:21:03. Version ac07

Copyright © 2024 Attilla Danko.