Velveeta Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Velveeta Valley Observatory clear sky chart from 2005-11-06 to 2024-11-12.

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	13% 9% 3 7% 5% 4 4 4 5% 7% 38%	101487
	Night	14% 9% 3 7% 4 4 4 3 5% 6% 39%	97774
Transparency	Day	44% 6% 12% 23% 13% 1	105026
	Night	44% 6% 11% 23% 14% 2	102376
Seeing	Day	17% 11% 29% 25% 14% 5%	15882
	Night	17% 9% 31% 30% 12% 1	25728

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	12% 13% 9% 15% 5% 4 4 4 4 5% 26%	2527
	11th to 20th	Day	12% 12% 5% 15% 5% 5% 5% 8% 8% 6% 19%	2530
	21st to end	Day	16% 19% 11% 11% 5% 4 3 2 4 5% 19%	2952
February	1st to 10th	Day	12% 14% 6% 8% 6% 4 5% 4 5% 7% 29%	1710
	11th to 20th	Day	13% 10% 4 9% 6% 4 4 3 5% 7% 36%	1800
	21st to end	Day	14% 15% 4 10% 5% 4 4 3 5% 5% 32%	1570
March	1st to 10th	Day	14% 9% 3 7% 4 4 4 3 4 7% 41%	3120
	11th to 20th	Day	11% 7% 3 7% 4 4 4 4 6% 7% 43%	3366
	21st to end	Day	21% 13% 4 11% 5% 5% 4 4 5% 5% 23%	4121
April	1st to 10th	Day	19% 11% 3 8% 5% 4 4 3 4 6% 31%	2280
	11th to 20th	Day	17% 9% 3 7% 5% 5% 4 4 5% 6% 34%	2254
	21st to end	Day	20% 10% 3 7% 4 5% 4 3 5% 6% 34%	2327
May	1st to 10th	Day	17% 7% 3 7% 5% 4 5% 4 6% 6% 36%	4170
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 3 5% 6% 44%	4399
	21st to end	Day	12% 7% 2 6% 4 5% 5% 5% 7% 8% 40%	4824
June	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 7% 43%	2660
	11th to 20th	Day	11% 5% 2 5% 4 5% 5% 4 5% 10% 45%	2660
	21st to end	Day	12% 7% 3 7% 4 5% 5% 5% 7% 9% 38%	2660
July	1st to 10th	Day	11% 7% 3 8% 5% 6% 5% 5% 7% 9% 34%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 6% 9% 52%	4440
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 4 7% 9% 41%	4813
August	1st to 10th	Day	10% 4 2 6% 5% 4 6% 5% 7% 9% 42%	4311
	11th to 20th	Day	11% 4 2 5% 3 4 4 4 6% 9% 48%	3773
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 8% 48%	4180
September	1st to 10th	Day	13% 6% 2 4 5% 4 5% 3 4 7% 47%	2280
	11th to 20th	Day	12% 4 1 3 3 3 4 3 6% 8% 52%	2214
	21st to end	Day	12% 6% 2 7% 4 4 4 3 5% 7% 45%	2090
October	1st to 10th	Day	14% 6% 2 6% 4 3 3 3 4 6% 49%	1948
	11th to 20th	Day	19% 8% 2 6% 5% 4 3 3 5% 6% 37%	1900
	21st to end	Day	19% 9% 3 6% 4 3 3 3 4 6% 39%	1924
November	1st to 10th	Day	12% 10% 4 5% 4 4 4 4 4 6% 44%	1762
	11th to 20th	Day	14% 12% 4 7% 5% 4 5% 4 6% 6% 33%	1719
	21st to end	Day	16% 14% 3 8% 3 3 3 3 4 6% 36%	1542
December	1st to 10th	Day	15% 13% 3 10% 5% 3 5% 3 4 6% 32%	1520
	11th to 20th	Day	14% 14% 4 10% 5% 4 5% 4 5% 7% 29%	1918
	21st to end	Day	21% 20% 9% 12% 5% 4 4 3 3 3 15%	2783
January	1st to 10th	Night	13% 14% 8% 11% 5% 4 3 3 3 4 31%	4428
	11th to 20th	Night	13% 16% 7% 14% 5% 4 4 5% 7% 4 20%	4440
	21st to end	Night	18% 18% 7% 11% 5% 5% 4 3 4 5% 22%	4713
February	1st to 10th	Night	13% 14% 5% 8% 5% 5% 4 3 4 4 34%	2470
	11th to 20th	Night	13% 10% 4 7% 5% 4 4 3 5% 6% 39%	2265
	21st to end	Night	18% 11% 4 6% 4 3 4 3 4 6% 36%	1884
March	1st to 10th	Night	19% 8% 3 6% 4 4 4 3 4 4 42%	3733
	11th to 20th	Night	9% 6% 2 6% 5% 4 4 4 5% 7% 47%	3622
	21st to end	Night	24% 11% 4 9% 5% 3 4 3 3 5% 28%	3508
April	1st to 10th	Night	17% 11% 3 5% 4 4 4 3 4 6% 39%	1900
	11th to 20th	Night	19% 9% 2 8% 4 3 3 3 4 6% 39%	1875
	21st to end	Night	17% 8% 2 7% 4 4 5% 4 5% 7% 36%	1853
May	1st to 10th	Night	17% 7% 3 7% 4 4 4 4 6% 7% 36%	2725
	11th to 20th	Night	14% 6% 2 6% 4 5% 5% 4 7% 7% 40%	2506
	21st to end	Night	10% 7% 2 6% 4 4 4 4 6% 8% 45%	2743
June	1st to 10th	Night	8% 5% 2 4 5% 4 5% 5% 7% 8% 47%	1520
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 6% 10% 46%	1520
	21st to end	Night	9% 6% 2 6% 4 5% 4 4 6% 8% 45%	1520
July	1st to 10th	Night	15% 6% 2 6% 5% 4 5% 4 5% 8% 40%	2530
	11th to 20th	Night	6% 3 2 4 3 4 4 4 5% 8% 58%	2530
	21st to end	Night	7% 5% 2 6% 5% 4 5% 5% 6% 9% 46%	2750
August	1st to 10th	Night	7% 3 2 6% 4 4 4 3 5% 8% 53%	2612
	11th to 20th	Night	9% 4 2 5% 4 3 4 4 5% 7% 51%	3054
	21st to end	Night	10% 4 2 5% 4 4 4 3 5% 8% 51%	3476
September	1st to 10th	Night	9% 6% 2 5% 3 3 3 2 4 6% 57%	1900
	11th to 20th	Night	10% 4 2 4 3 4 4 3 5% 7% 53%	1946
	21st to end	Night	11% 5% 2 5% 4 4 4 3 5% 6% 50%	2090
October	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 5% 5% 51%	2228
	11th to 20th	Night	17% 6% 2 5% 4 4 3 3 4 6% 46%	2280
	21st to end	Night	19% 9% 2 7% 4 4 4 3 5% 6% 38%	2674
November	1st to 10th	Night	12% 8% 2 6% 3 3 3 3 4 5% 50%	2536
	11th to 20th	Night	14% 10% 4 8% 5% 3 4 4 6% 6% 37%	2484
	21st to end	Night	18% 9% 3 7% 5% 3 4 3 4 6% 38%	2636
December	1st to 10th	Night	15% 12% 4 9% 5% 5% 4 3 5% 6% 30%	2660
	11th to 20th	Night	15% 13% 4 9% 5% 4 4 3 4 6% 32%	3279
	21st to end	Night	22% 16% 5% 11% 5% 5% 5% 4 4 4 19%	4884

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	62% 6% 12% 15% 6%	2528
	11th to 20th	Day	58% 7% 15% 12% 8%	2530
	21st to end	Day	67% 4 9% 14% 5%	2952
February	1st to 10th	Day	55% 5% 12% 17% 10% 1	1710
	11th to 20th	Day	48% 5% 12% 24% 9% 2	1810
	21st to end	Day	53% 6% 10% 20% 10% 2	1570
March	1st to 10th	Day	44% 6% 13% 24% 11% 3	3120
	11th to 20th	Day	38% 6% 12% 31% 11% 1	3366
	21st to end	Day	62% 8% 12% 14% 4 1	4121
April	1st to 10th	Day	53% 6% 10% 21% 9%	2280
	11th to 20th	Day	49% 6% 9% 21% 12% 2	2254
	21st to end	Day	50% 6% 11% 18% 12% 2	2327
May	1st to 10th	Day	46% 8% 11% 20% 14% 1	4208
	11th to 20th	Day	41% 6% 11% 28% 14%	4403
	21st to end	Day	38% 9% 12% 21% 16% 4	4837
June	1st to 10th	Day	37% 8% 13% 25% 16% 1	2660
	11th to 20th	Day	34% 7% 13% 25% 20% 2	2660
	21st to end	Day	40% 7% 15% 23% 12% 2	2660
July	1st to 10th	Day	45% 7% 14% 24% 9% 2	4371
	11th to 20th	Day	27% 7% 17% 30% 17% 1	4365
	21st to end	Day	38% 8% 15% 18% 18% 3	4662
August	1st to 10th	Day	36% 8% 16% 27% 13% 1	4296
	11th to 20th	Day	32% 7% 14% 33% 14% 1	3809
	21st to end	Day	34% 6% 13% 30% 16% 1	4179
September	1st to 10th	Day	36% 6% 10% 26% 20% 2	2280
	11th to 20th	Day	29% 7% 11% 31% 19% 2	2214
	21st to end	Day	38% 5% 10% 27% 18% 1	2090
October	1st to 10th	Day	24% 4 7% 37% 28% 1	3234
	11th to 20th	Day	33% 4 10% 27% 24% 2	3140
	21st to end	Day	43% 4 8% 28% 14% 3	3149
November	1st to 10th	Day	40% 4 15% 25% 14% 2	1762
	11th to 20th	Day	51% 5% 13% 20% 10% 1	1719
	21st to end	Day	50% 5% 14% 22% 8% 1	1542
December	1st to 10th	Day	54% 6% 14% 17% 8% 1	1520
	11th to 20th	Day	56% 4 16% 15% 8% 2	1915
	21st to end	Day	75% 5% 8% 8% 4	2783
January	1st to 10th	Night	57% 5% 11% 18% 8% 1	4428
	11th to 20th	Night	64% 5% 10% 12% 8%	4440
	21st to end	Night	67% 4 9% 14% 5% 1	4713
February	1st to 10th	Night	54% 4 10% 19% 12% 1	2470
	11th to 20th	Night	47% 4 12% 22% 14% 1	2266
	21st to end	Night	50% 4 12% 20% 11% 4	1884
March	1st to 10th	Night	45% 5% 13% 22% 10% 4	3733
	11th to 20th	Night	35% 7% 10% 29% 17% 2	3622
	21st to end	Night	60% 4 11% 17% 8% 1	3508
April	1st to 10th	Night	46% 6% 11% 22% 13% 2	1900
	11th to 20th	Night	47% 4 7% 21% 18% 4	1875
	21st to end	Night	45% 7% 13% 23% 11% 2	1853
May	1st to 10th	Night	44% 8% 13% 17% 16% 2	2752
	11th to 20th	Night	39% 8% 14% 25% 13% 1	2507
	21st to end	Night	32% 11% 13% 20% 20% 4	2751
June	1st to 10th	Night	31% 7% 15% 26% 19% 2	1520
	11th to 20th	Night	33% 7% 10% 24% 24% 3	1520
	21st to end	Night	37% 7% 14% 22% 18% 3	1520
July	1st to 10th	Night	42% 6% 15% 21% 12% 3	2490
	11th to 20th	Night	24% 7% 15% 34% 19% 2	2482
	21st to end	Night	32% 8% 16% 20% 20% 4	2662
August	1st to 10th	Night	29% 6% 15% 31% 18% 2	2603
	11th to 20th	Night	30% 7% 15% 30% 17% 1	3084
	21st to end	Night	30% 6% 13% 30% 17% 3	3476
September	1st to 10th	Night	30% 6% 11% 27% 24% 3	1900
	11th to 20th	Night	31% 5% 10% 32% 19% 3	1946
	21st to end	Night	34% 6% 10% 29% 19% 2	2090
October	1st to 10th	Night	24% 4 7% 35% 29% 1	3722
	11th to 20th	Night	33% 5% 8% 25% 26% 3	3779
	21st to end	Night	42% 4 9% 25% 16% 3	4399
November	1st to 10th	Night	37% 5% 10% 27% 18% 3	2536
	11th to 20th	Night	47% 6% 12% 22% 12% 1	2484
	21st to end	Night	48% 5% 13% 23% 11% 1	2636
December	1st to 10th	Night	55% 5% 11% 20% 8% 1	2660
	11th to 20th	Night	53% 5% 13% 19% 8% 1	3281
	21st to end	Night	67% 6% 9% 13% 5%	4884

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	19% 14% 31% 29% 7% 1	270
	11th to 20th	Day	19% 15% 40% 20% 4 1	270
	21st to end	Day	24% 10% 39% 21% 4 1	297
February	1st to 10th	Day	18% 20% 37% 18% 7%	270
	11th to 20th	Day	20% 22% 30% 23% 4	270
	21st to end	Day	24% 19% 41% 12% 4	225
March	1st to 10th	Day	19% 21% 41% 16% 3	270
	11th to 20th	Day	23% 20% 36% 14% 7% 1	270
	21st to end	Day	29% 14% 31% 18% 6% 1	475
April	1st to 10th	Day	26% 15% 32% 22% 5%	460
	11th to 20th	Day	22% 21% 27% 19% 9% 3	452
	21st to end	Day	24% 14% 29% 23% 9% 2	460
May	1st to 10th	Day	20% 14% 32% 24% 7% 3	512
	11th to 20th	Day	22% 10% 29% 24% 12% 3	675
	21st to end	Day	17% 11% 27% 23% 16% 7%	734
June	1st to 10th	Day	10% 7% 30% 30% 18% 5%	680
	11th to 20th	Day	12% 7% 32% 29% 15% 5%	680
	21st to end	Day	15% 7% 28% 31% 15% 4	680
July	1st to 10th	Day	9% 3 17% 32% 25% 13%	671
	11th to 20th	Day	9% 5% 26% 31% 21% 9%	668
	21st to end	Day	8% 3 23% 36% 22% 7%	739
August	1st to 10th	Day	7% 3 22% 33% 25% 10%	676
	11th to 20th	Day	12% 6% 19% 27% 22% 15%	511
	21st to end	Day	11% 4 18% 31% 26% 9%	539
September	1st to 10th	Day	16% 6% 22% 28% 21% 7%	490
	11th to 20th	Day	11% 3 19% 30% 25% 11%	490
	21st to end	Day	15% 12% 25% 24% 17% 7%	490
October	1st to 10th	Day	16% 9% 27% 26% 18% 3	348
	11th to 20th	Day	23% 21% 32% 16% 9%	300
	21st to end	Day	28% 15% 30% 20% 7%	330
November	1st to 10th	Day	18% 17% 34% 20% 9% 2	300
	11th to 20th	Day	20% 16% 39% 17% 6% 1	273
	21st to end	Day	26% 13% 36% 21% 4	270
December	1st to 10th	Day	19% 15% 43% 17% 5% 2	270
	11th to 20th	Day	20% 11% 40% 21% 8% 1	270
	21st to end	Day	26% 16% 40% 16% 2	297
January	1st to 10th	Night	19% 14% 37% 25% 5% 1	950
	11th to 20th	Night	19% 13% 38% 24% 5% 1	950
	21st to end	Night	21% 11% 37% 26% 5%	1045
February	1st to 10th	Night	20% 12% 38% 24% 5%	950
	11th to 20th	Night	18% 14% 38% 25% 5%	790
	21st to end	Night	24% 14% 37% 21% 4	628
March	1st to 10th	Night	22% 11% 36% 24% 6%	760
	11th to 20th	Night	16% 13% 35% 28% 7%	660
	21st to end	Night	25% 10% 34% 25% 6% 1	627
April	1st to 10th	Night	21% 13% 37% 24% 4	570
	11th to 20th	Night	21% 14% 29% 28% 7%	563
	21st to end	Night	21% 9% 32% 28% 9% 1	570
May	1st to 10th	Night	18% 8% 34% 30% 9% 1	570
	11th to 20th	Night	19% 6% 32% 32% 11%	561
	21st to end	Night	13% 5% 31% 34% 15% 1	617
June	1st to 10th	Night	10% 5% 26% 43% 16% 1	570
	11th to 20th	Night	12% 4 29% 42% 12%	570
	21st to end	Night	9% 4 29% 40% 17% 1	570
July	1st to 10th	Night	8% 3 14% 42% 30% 3	555
	11th to 20th	Night	8% 2 21% 42% 24% 3	552
	21st to end	Night	9% 2 16% 45% 26% 1	624
August	1st to 10th	Night	5% 2 16% 46% 29% 3	567
	11th to 20th	Night	8% 2 15% 38% 31% 6%	564
	21st to end	Night	10% 2 17% 41% 27% 3	627
September	1st to 10th	Night	10% 3 22% 36% 24% 5%	570
	11th to 20th	Night	11% 3 22% 36% 25% 4	616
	21st to end	Night	12% 9% 26% 32% 20% 2	760
October	1st to 10th	Night	14% 7% 29% 33% 17% 1	760
	11th to 20th	Night	20% 12% 30% 27% 10%	760
	21st to end	Night	23% 11% 33% 24% 8%	836
November	1st to 10th	Night	15% 10% 42% 23% 10% 1	780
	11th to 20th	Night	19% 14% 36% 25% 6%	765
	21st to end	Night	22% 12% 35% 25% 7%	926
December	1st to 10th	Night	21% 12% 39% 22% 6%	950
	11th to 20th	Night	22% 11% 35% 26% 5% 1	950
	21st to end	Night	27% 13% 36% 22% 3	1045

Page generated at 2024-11-08 21:45:39. Version ac07

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