Yarger Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yarger Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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% 10% 4 8% 5% 5% 5% 4 5% 7% 34%	101164
	Night	15% 11% 4 9% 5% 4 4 4 5% 7% 33%	97895
Transparency	Day	49% 2 11% 23% 13% 1	104763
	Night	51% 2 10% 22% 13% 1	102437
Seeing	Day	17% 10% 27% 24% 16% 6%	15746
	Night	19% 8% 28% 30% 13% 1	25577

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	15% 20% 7% 12% 5% 5% 6% 4 4 5% 16%	2527
	11th to 20th	Day	15% 18% 8% 14% 8% 7% 8% 5% 5% 4 9%	2530
	21st to end	Day	25% 23% 8% 13% 5% 4 3 2 3 4 10%	2791
February	1st to 10th	Day	14% 15% 6% 12% 10% 8% 4 3 4 5% 18%	1807
	11th to 20th	Day	15% 12% 5% 15% 9% 5% 4 4 5% 4 22%	1848
	21st to end	Day	16% 15% 7% 13% 5% 4 5% 4 5% 6% 21%	1570
March	1st to 10th	Day	17% 13% 6% 8% 5% 5% 4 4 4 6% 28%	3120
	11th to 20th	Day	11% 9% 6% 10% 6% 5% 4 4 7% 8% 30%	3379
	21st to end	Day	19% 14% 6% 11% 7% 5% 5% 3 4 5% 23%	3959
April	1st to 10th	Day	17% 13% 4 8% 5% 5% 4 3 5% 6% 30%	2280
	11th to 20th	Day	16% 11% 2 7% 4 4 4 4 5% 6% 36%	2287
	21st to end	Day	18% 9% 3 7% 5% 4 4 3 5% 7% 35%	2470
May	1st to 10th	Day	18% 8% 2 7% 4 5% 5% 4 6% 7% 33%	4082
	11th to 20th	Day	14% 8% 2 6% 4 4 4 4 6% 8% 39%	4081
	21st to end	Day	9% 6% 2 7% 5% 4 5% 4 6% 9% 44%	4747
June	1st to 10th	Day	9% 6% 2 7% 4 5% 4 4 7% 8% 44%	2660
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 5% 7% 9% 44%	2660
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 5% 5% 6% 10% 36%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 6% 11% 49%	4440
	21st to end	Day	6% 6% 3 7% 4 6% 6% 5% 7% 8% 43%	4790
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 46%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 6% 7% 46%	4030
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 9% 47%	4180
September	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 5% 9% 46%	2246
	11th to 20th	Day	11% 4 2 5% 4 4 5% 3 6% 8% 48%	2090
	21st to end	Day	13% 7% 3 6% 5% 5% 4 4 6% 8% 40%	2090
October	1st to 10th	Day	13% 6% 2 8% 5% 4 4 3 5% 6% 43%	2090
	11th to 20th	Day	18% 8% 3 8% 5% 5% 4 4 5% 7% 33%	1880
	21st to end	Day	21% 11% 4 8% 6% 6% 5% 3 5% 7% 26%	1881
November	1st to 10th	Day	12% 12% 4 7% 4 4 5% 4 6% 7% 38%	1699
	11th to 20th	Day	16% 17% 5% 9% 6% 5% 4 3 5% 6% 24%	1710
	21st to end	Day	21% 15% 5% 10% 5% 4 4 3 4 5% 23%	1710
December	1st to 10th	Day	15% 19% 8% 11% 7% 4 3 3 4 6% 21%	1625
	11th to 20th	Day	12% 20% 9% 14% 7% 4 4 3 4 5% 17%	1918
	21st to end	Day	22% 20% 7% 14% 7% 4 4 3 4 4 11%	2783
January	1st to 10th	Night	16% 18% 9% 13% 6% 5% 4 3 5% 5% 16%	4428
	11th to 20th	Night	15% 18% 9% 17% 6% 4 6% 5% 5% 4 11%	4440
	21st to end	Night	25% 18% 9% 13% 6% 4 3 3 3 4 11%	4875
February	1st to 10th	Night	17% 16% 4 12% 8% 5% 4 3 5% 5% 21%	2371
	11th to 20th	Night	14% 12% 5% 12% 7% 6% 4 3 5% 6% 25%	2218
	21st to end	Night	19% 12% 5% 11% 5% 4 4 4 5% 5% 26%	1884
March	1st to 10th	Night	16% 11% 5% 9% 5% 4 3 3 4 6% 34%	3733
	11th to 20th	Night	10% 7% 3 7% 6% 4 5% 4 5% 7% 42%	3579
	21st to end	Night	19% 11% 5% 11% 5% 4 4 3 4 6% 28%	3700
April	1st to 10th	Night	15% 10% 2 7% 5% 4 5% 4 5% 8% 35%	1900
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 4 6% 37%	1840
	21st to end	Night	18% 8% 2 8% 5% 3 5% 3 5% 7% 36%	1710
May	1st to 10th	Night	14% 9% 2 8% 4 5% 5% 4 7% 8% 33%	2813
	11th to 20th	Night	18% 8% 3 6% 3 3 4 3 4 7% 42%	2812
	21st to end	Night	13% 6% 3 7% 4 4 4 4 6% 7% 42%	2815
June	1st to 10th	Night	10% 4 2 4 4 5% 4 4 7% 10% 46%	1520
	11th to 20th	Night	9% 6% 2 6% 4 4 5% 5% 7% 9% 43%	1520
	21st to end	Night	9% 6% 2 5% 6% 4 4 4 7% 11% 43%	1520
July	1st to 10th	Night	8% 5% 2 6% 4 4 5% 5% 7% 10% 43%	2530
	11th to 20th	Night	7% 3 2 5% 3 3 3 3 5% 9% 56%	2530
	21st to end	Night	6% 5% 2 5% 5% 5% 5% 4 6% 10% 46%	2770
August	1st to 10th	Night	9% 6% 2 6% 4 4 4 4 7% 10% 45%	2825
	11th to 20th	Night	8% 4 2 6% 4 5% 4 4 6% 8% 48%	2785
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 8% 48%	3473
September	1st to 10th	Night	10% 5% 3 5% 4 4 4 4 5% 6% 50%	1914
	11th to 20th	Night	10% 4 1 4 5% 3 4 3 4 8% 54%	2090
	21st to end	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	2090
October	1st to 10th	Night	13% 7% 2 6% 4 3 3 3 5% 6% 47%	2090
	11th to 20th	Night	17% 9% 3 9% 5% 4 4 2 4 6% 38%	2298
	21st to end	Night	21% 11% 3 7% 4 4 4 3 4 6% 33%	2717
November	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 5% 6% 39%	2452
	11th to 20th	Night	15% 14% 5% 9% 6% 4 4 4 6% 6% 26%	2470
	21st to end	Night	17% 17% 5% 9% 4 5% 3 3 5% 6% 25%	2470
December	1st to 10th	Night	16% 20% 6% 11% 7% 5% 4 3 4 5% 18%	2550
	11th to 20th	Night	15% 18% 8% 12% 7% 5% 4 4 4 4 18%	3279
	21st to end	Night	27% 20% 6% 11% 5% 4 5% 3 4 4 12%	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	71% 2 10% 15% 3	2528
	11th to 20th	Day	76% 1 8% 10% 5%	2530
	21st to end	Day	81% 1 6% 9% 3	2791
February	1st to 10th	Day	68% 2 8% 14% 6% 1	1807
	11th to 20th	Day	64% 3 8% 16% 9% 1	1858
	21st to end	Day	64% 2 10% 15% 7% 1	1570
March	1st to 10th	Day	59% 2 10% 21% 8%	3120
	11th to 20th	Day	52% 2 11% 26% 8% 1	3379
	21st to end	Day	66% 1 9% 19% 4	3959
April	1st to 10th	Day	55% 3 9% 21% 12%	2280
	11th to 20th	Day	49% 3 9% 23% 13% 3	2287
	21st to end	Day	50% 2 12% 20% 15% 2	2470
May	1st to 10th	Day	50% 2 10% 25% 12% 1	4120
	11th to 20th	Day	44% 2 14% 28% 11% 1	4085
	21st to end	Day	38% 2 10% 23% 24% 2	4760
June	1st to 10th	Day	38% 3 11% 28% 18% 2	2660
	11th to 20th	Day	37% 4 11% 27% 19% 3	2660
	21st to end	Day	40% 4 14% 23% 16% 3	2660
July	1st to 10th	Day	45% 3 13% 21% 16% 3	4371
	11th to 20th	Day	31% 2 14% 35% 17% 2	4365
	21st to end	Day	39% 3 14% 20% 21% 2	4639
August	1st to 10th	Day	36% 3 15% 29% 17% 1	4091
	11th to 20th	Day	37% 2 12% 32% 17% 1	4069
	21st to end	Day	34% 3 13% 30% 18% 3	4179
September	1st to 10th	Day	37% 3 14% 25% 19% 3	2246
	11th to 20th	Day	35% 3 9% 30% 21% 2	2090
	21st to end	Day	42% 3 9% 26% 19% 1	2090
October	1st to 10th	Day	30% 2 9% 39% 18% 1	3480
	11th to 20th	Day	42% 1 10% 23% 23%	3096
	21st to end	Day	49% 2 10% 26% 11% 2	3081
November	1st to 10th	Day	45% 3 12% 24% 16% 1	1699
	11th to 20th	Day	61% 1 10% 19% 7% 1	1710
	21st to end	Day	64% 2 11% 17% 5%	1710
December	1st to 10th	Day	66% 2 10% 17% 5%	1625
	11th to 20th	Day	70% 2 11% 14% 3	1915
	21st to end	Day	80% 2 7% 8% 3	2783
January	1st to 10th	Night	71% 1 8% 14% 5%	4428
	11th to 20th	Night	76% 2 9% 10% 3	4440
	21st to end	Night	78% 1 7% 10% 3	4875
February	1st to 10th	Night	66% 2 10% 14% 7% 1	2371
	11th to 20th	Night	61% 2 8% 20% 9%	2219
	21st to end	Night	61% 3 10% 18% 7% 2	1884
March	1st to 10th	Night	53% 1 11% 25% 9% 1	3733
	11th to 20th	Night	44% 2 11% 25% 16% 2	3579
	21st to end	Night	59% 1 11% 20% 8% 1	3700
April	1st to 10th	Night	48% 3 11% 23% 14% 1	1900
	11th to 20th	Night	50% 2 7% 19% 19% 3	1840
	21st to end	Night	49% 2 9% 22% 16% 2	1710
May	1st to 10th	Night	49% 2 10% 25% 12% 1	2840
	11th to 20th	Night	45% 2 10% 28% 15% 1	2813
	21st to end	Night	41% 2 12% 21% 21% 3	2823
June	1st to 10th	Night	34% 3 11% 31% 19% 3	1520
	11th to 20th	Night	36% 4 13% 25% 20% 2	1520
	21st to end	Night	37% 3 16% 24% 16% 3	1520
July	1st to 10th	Night	36% 2 15% 26% 14% 7%	2490
	11th to 20th	Night	28% 2 13% 29% 25% 3	2482
	21st to end	Night	35% 3 15% 18% 26% 3	2682
August	1st to 10th	Night	36% 3 13% 30% 17% 1	2814
	11th to 20th	Night	33% 3 12% 33% 18% 1	2812
	21st to end	Night	35% 3 9% 31% 19% 3	3473
September	1st to 10th	Night	35% 3 11% 25% 22% 4	1914
	11th to 20th	Night	30% 2 7% 34% 26% 2	2090
	21st to end	Night	41% 3 8% 29% 18% 1	2090
October	1st to 10th	Night	28% 2 8% 34% 27% 1	3480
	11th to 20th	Night	41% 1 8% 26% 23% 1	3821
	21st to end	Night	42% 2 7% 30% 18% 1	4467
November	1st to 10th	Night	47% 3 9% 25% 16% 1	2452
	11th to 20th	Night	56% 3 12% 19% 8% 1	2470
	21st to end	Night	61% 2 12% 19% 6%	2470
December	1st to 10th	Night	68% 2 9% 15% 6%	2550
	11th to 20th	Night	69% 2 10% 14% 5% 1	3281
	21st to end	Night	77% 2 10% 8% 3	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	21% 17% 31% 20% 9% 1	270
	11th to 20th	Day	21% 15% 39% 17% 6% 1	270
	21st to end	Day	25% 17% 28% 25% 5%	297
February	1st to 10th	Day	23% 18% 31% 20% 7% 1	270
	11th to 20th	Day	24% 19% 33% 20% 4	270
	21st to end	Day	24% 20% 40% 11% 4	225
March	1st to 10th	Day	19% 20% 42% 14% 5%	270
	11th to 20th	Day	22% 16% 30% 24% 8% 1	398
	21st to end	Day	30% 12% 29% 21% 7% 1	506
April	1st to 10th	Day	24% 12% 32% 24% 7% 1	460
	11th to 20th	Day	23% 16% 30% 18% 10% 3	452
	21st to end	Day	23% 12% 32% 20% 11% 2	460
May	1st to 10th	Day	24% 11% 29% 23% 11% 3	463
	11th to 20th	Day	24% 9% 24% 23% 14% 5%	487
	21st to end	Day	12% 7% 26% 27% 20% 8%	683
June	1st to 10th	Day	11% 7% 26% 32% 18% 5%	680
	11th to 20th	Day	12% 5% 30% 28% 19% 6%	680
	21st to end	Day	12% 8% 28% 28% 18% 6%	680
July	1st to 10th	Day	9% 4 22% 28% 23% 15%	671
	11th to 20th	Day	10% 3 25% 26% 24% 11%	668
	21st to end	Day	6% 4 21% 34% 24% 10%	728
August	1st to 10th	Day	8% 4 16% 28% 25% 19%	486
	11th to 20th	Day	10% 4 18% 28% 28% 11%	479
	21st to end	Day	10% 3 19% 29% 28% 12%	539
September	1st to 10th	Day	14% 6% 19% 27% 24% 11%	490
	11th to 20th	Day	9% 3 19% 21% 31% 17%	490
	21st to end	Day	16% 10% 23% 24% 19% 9%	490
October	1st to 10th	Day	14% 8% 27% 26% 18% 6%	490
	11th to 20th	Day	21% 18% 24% 27% 9% 1	408
	21st to end	Day	25% 16% 38% 15% 4 2	330
November	1st to 10th	Day	15% 14% 33% 25% 9% 4	279
	11th to 20th	Day	23% 19% 31% 17% 9% 1	270
	21st to end	Day	29% 11% 38% 17% 4	270
December	1st to 10th	Day	22% 23% 32% 13% 9% 1	270
	11th to 20th	Day	21% 16% 40% 18% 4	270
	21st to end	Day	22% 22% 35% 18% 3	297
January	1st to 10th	Night	22% 14% 34% 23% 6%	950
	11th to 20th	Night	25% 13% 34% 23% 5% 1	950
	21st to end	Night	21% 10% 37% 27% 4	1036
February	1st to 10th	Night	26% 9% 36% 25% 4	760
	11th to 20th	Night	20% 13% 35% 27% 4	743
	21st to end	Night	26% 11% 36% 24% 4	628
March	1st to 10th	Night	20% 11% 35% 26% 7% 1	760
	11th to 20th	Night	18% 10% 37% 27% 7% 1	760
	21st to end	Night	24% 11% 29% 30% 6% 1	770
April	1st to 10th	Night	18% 12% 33% 30% 6% 1	570
	11th to 20th	Night	23% 10% 33% 28% 5% 1	563
	21st to end	Night	21% 7% 35% 26% 10%	570
May	1st to 10th	Night	19% 6% 32% 34% 8% 1	570
	11th to 20th	Night	24% 4 25% 32% 15%	561
	21st to end	Night	14% 3 23% 37% 21% 1	617
June	1st to 10th	Night	11% 3 25% 44% 18% 1	570
	11th to 20th	Night	12% 4 25% 41% 18% 1	570
	21st to end	Night	11% 2 22% 40% 24% 1	570
July	1st to 10th	Night	8% 2 17% 41% 27% 5%	555
	11th to 20th	Night	9% 3 15% 41% 28% 4	552
	21st to end	Night	7% 2 14% 42% 33% 2	624
August	1st to 10th	Night	9% 2 10% 46% 29% 4	567
	11th to 20th	Night	8% 2 16% 41% 29% 5%	564
	21st to end	Night	11% 1 15% 35% 33% 5%	627
September	1st to 10th	Night	11% 3 16% 38% 29% 4	584
	11th to 20th	Night	11% 3 15% 36% 30% 5%	760
	21st to end	Night	18% 6% 23% 28% 21% 5%	760
October	1st to 10th	Night	16% 5% 24% 34% 18% 2	760
	11th to 20th	Night	22% 11% 28% 29% 10% 1	760
	21st to end	Night	27% 12% 31% 23% 7%	836
November	1st to 10th	Night	20% 9% 32% 27% 11% 1	755
	11th to 20th	Night	24% 13% 32% 24% 6% 1	760
	21st to end	Night	24% 10% 33% 28% 5%	760
December	1st to 10th	Night	25% 14% 35% 22% 5%	840
	11th to 20th	Night	24% 11% 36% 24% 4	950
	21st to end	Night	31% 13% 32% 22% 2	1045

Page generated at 2024-11-01 22:47:52. Version ac07

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