Skunk Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skunk Ridge Observatory clear sky chart from 2005-11-06 to 2025-01-07.

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	15% 9% 3 7% 4 4 4 4 5% 7% 38%	105213
	Night	15% 10% 3 7% 4 4 4 3 5% 6% 38%	103802
Transparency	Day	25% 46% 6% 14% 9% 1	108896
	Night	26% 45% 6% 13% 9% 1	108246
Seeing	Day	19% 14% 28% 22% 12% 5%	15535
	Night	19% 11% 26% 27% 15% 2	25327

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% 18% 6% 8% 4 4 4 3 4 5% 29%	2575
	11th to 20th	Day	17% 14% 5% 12% 5% 6% 4 3 3 4 27%	2683
	21st to end	Day	29% 15% 8% 7% 4 3 3 3 3 4 22%	3124
February	1st to 10th	Day	19% 13% 4 9% 4 3 3 3 5% 5% 32%	1857
	11th to 20th	Day	17% 11% 5% 8% 4 4 4 2 5% 5% 34%	1848
	21st to end	Day	19% 13% 5% 8% 4 3 4 3 5% 6% 31%	1570
March	1st to 10th	Day	24% 14% 4 7% 4 3 3 2 3 4 32%	3120
	11th to 20th	Day	14% 8% 3 6% 4 4 3 3 5% 7% 42%	3467
	21st to end	Day	17% 9% 3 6% 4 5% 4 4 5% 7% 36%	3815
April	1st to 10th	Day	16% 9% 3 6% 4 4 4 4 6% 8% 36%	2280
	11th to 20th	Day	17% 8% 3 6% 4 4 4 2 5% 7% 40%	2269
	21st to end	Day	18% 7% 3 7% 4 5% 5% 3 5% 8% 36%	2470
May	1st to 10th	Day	21% 9% 3 7% 5% 5% 4 4 5% 8% 29%	4082
	11th to 20th	Day	21% 7% 2 6% 4 4 4 3 5% 6% 39%	4081
	21st to end	Day	11% 6% 3 8% 6% 5% 6% 5% 7% 9% 34%	4476
June	1st to 10th	Day	11% 6% 2 7% 6% 4 5% 4 5% 7% 42%	2498
	11th to 20th	Day	9% 4 2 7% 6% 5% 4 5% 6% 9% 44%	2660
	21st to end	Day	9% 6% 3 6% 5% 6% 5% 4 6% 9% 41%	2660
July	1st to 10th	Day	13% 7% 2 6% 4 5% 5% 4 6% 10% 39%	4440
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 7% 10% 47%	4344
	21st to end	Day	11% 8% 3 9% 7% 7% 7% 5% 7% 8% 29%	4466
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 46%	4104
	11th to 20th	Day	8% 5% 2 6% 4 5% 6% 4 7% 11% 42%	3965
	21st to end	Day	5% 4 1 5% 3 4 5% 3 5% 8% 56%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 5% 7% 47%	2185
	11th to 20th	Day	9% 5% 2 7% 5% 4 4 4 6% 7% 48%	2090
	21st to end	Day	16% 4 2 6% 3 4 3 2 4 6% 48%	2090
October	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 5% 5% 53%	2090
	11th to 20th	Day	13% 7% 2 5% 4 4 4 3 5% 6% 47%	1963
	21st to end	Day	20% 8% 3 4 4 4 4 4 4 6% 39%	1916
November	1st to 10th	Day	10% 7% 2 5% 3 4 3 3 4 6% 53%	1762
	11th to 20th	Day	16% 11% 3 6% 5% 4 4 3 5% 6% 38%	1800
	21st to end	Day	18% 11% 4 7% 4 3 3 2 4 6% 39%	1800
December	1st to 10th	Day	19% 10% 3 6% 4 3 3 3 4 4 41%	2930
	11th to 20th	Day	18% 14% 5% 8% 5% 5% 5% 4 4 5% 27%	3373
	21st to end	Day	22% 19% 4 8% 5% 4 4 3 4 5% 20%	4180
January	1st to 10th	Night	17% 16% 6% 9% 5% 4 5% 4 5% 5% 24%	4513
	11th to 20th	Night	17% 16% 6% 15% 5% 4 3 2 3 4 25%	4276
	21st to end	Night	26% 18% 5% 6% 4 3 3 2 3 4 25%	4532
February	1st to 10th	Night	21% 14% 5% 7% 4 4 3 4 4 5% 29%	2318
	11th to 20th	Night	18% 11% 4 8% 5% 3 4 3 5% 6% 33%	2218
	21st to end	Night	21% 14% 4 8% 4 3 3 3 4 5% 30%	1884
March	1st to 10th	Night	23% 13% 3 6% 4 3 3 3 4 5% 32%	3733
	11th to 20th	Night	14% 8% 2 6% 3 3 4 3 5% 6% 47%	3492
	21st to end	Night	16% 8% 3 7% 5% 4 4 3 5% 6% 39%	3817
April	1st to 10th	Night	13% 8% 3 6% 5% 4 5% 4 7% 7% 38%	1915
	11th to 20th	Night	15% 8% 2 6% 5% 4 3 4 5% 6% 41%	1857
	21st to end	Night	18% 6% 2 6% 6% 4 3 3 7% 7% 37%	1710
May	1st to 10th	Night	21% 11% 3 9% 5% 5% 4 3 5% 7% 27%	2813
	11th to 20th	Night	19% 6% 1 5% 4 4 5% 4 6% 8% 39%	2812
	21st to end	Night	10% 5% 2 6% 4 5% 4 4 7% 9% 45%	3079
June	1st to 10th	Night	9% 5% 2 5% 5% 4 4 4 5% 9% 49%	1676
	11th to 20th	Night	7% 5% 2 5% 3 5% 5% 3 7% 11% 47%	1520
	21st to end	Night	6% 4 1 5% 4 5% 5% 5% 7% 10% 48%	1520
July	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	2530
	11th to 20th	Night	5% 3 1 5% 3 4 5% 4 6% 10% 54%	2620
	21st to end	Night	11% 7% 3 8% 5% 5% 6% 5% 7% 8% 36%	3087
August	1st to 10th	Night	7% 5% 2 6% 5% 4 5% 4 6% 9% 48%	2825
	11th to 20th	Night	7% 5% 2 7% 4 4 4 4 6% 9% 48%	2846
	21st to end	Night	4 3 1 4 3 3 4 3 5% 9% 61%	3476
September	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 6% 7% 51%	1976
	11th to 20th	Night	10% 4 1 4 3 3 4 3 6% 8% 53%	2090
	21st to end	Night	14% 5% 2 6% 4 3 4 3 5% 5% 50%	2090
October	1st to 10th	Night	9% 4 2 5% 3 3 4 3 5% 6% 56%	2090
	11th to 20th	Night	14% 6% 2 5% 3 4 4 4 6% 6% 47%	2216
	21st to end	Night	18% 8% 2 6% 3 4 3 3 4 6% 41%	2679
November	1st to 10th	Night	13% 8% 2 5% 4 3 4 3 5% 5% 49%	2536
	11th to 20th	Night	16% 9% 3 7% 4 3 4 3 5% 7% 40%	2600
	21st to end	Night	19% 12% 4 6% 5% 4 3 3 4 6% 35%	2600
December	1st to 10th	Night	18% 11% 3 8% 4 3 3 2 4 4 39%	4250
	11th to 20th	Night	19% 13% 5% 8% 4 4 4 3 4 6% 29%	4822
	21st to end	Night	23% 20% 6% 9% 5% 4 4 3 4 4 18%	6784

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	38% 38% 7% 10% 7%	2576
	11th to 20th	Day	40% 38% 6% 12% 5%	2683
	21st to end	Day	46% 40% 3 9% 2	3124
February	1st to 10th	Day	20% 64% 4 7% 5%	1857
	11th to 20th	Day	18% 64% 3 9% 5%	1858
	21st to end	Day	17% 65% 4 8% 5% 1	1570
March	1st to 10th	Day	39% 41% 3 8% 5% 3	3120
	11th to 20th	Day	20% 41% 7% 20% 12% 1	3467
	21st to end	Day	23% 43% 9% 14% 10%	3815
April	1st to 10th	Day	19% 65% 4 8% 3	2280
	11th to 20th	Day	15% 66% 4 8% 6% 1	2269
	21st to end	Day	15% 65% 5% 9% 5% 1	2470
May	1st to 10th	Day	31% 44% 9% 11% 5%	4120
	11th to 20th	Day	27% 42% 9% 16% 7%	4085
	21st to end	Day	26% 44% 8% 11% 10% 1	4489
June	1st to 10th	Day	15% 66% 4 8% 7% 1	2498
	11th to 20th	Day	14% 66% 3 8% 7% 1	2660
	21st to end	Day	15% 65% 6% 7% 6% 1	2660
July	1st to 10th	Day	27% 38% 7% 14% 13% 1	4371
	11th to 20th	Day	18% 37% 6% 26% 12%	4269
	21st to end	Day	37% 37% 7% 9% 9% 1	4324
August	1st to 10th	Day	20% 39% 9% 26% 6%	4091
	11th to 20th	Day	23% 38% 6% 24% 9%	4004
	21st to end	Day	14% 38% 10% 24% 13% 1	4179
September	1st to 10th	Day	13% 61% 4 10% 9% 2	2185
	11th to 20th	Day	13% 60% 6% 10% 9% 1	2090
	21st to end	Day	15% 60% 4 12% 8%	2090
October	1st to 10th	Day	11% 37% 3 23% 24% 1	3480
	11th to 20th	Day	16% 38% 4 19% 22% 1	3242
	21st to end	Day	19% 37% 6% 18% 19% 1	3128
November	1st to 10th	Day	18% 56% 5% 13% 6% 1	1762
	11th to 20th	Day	19% 56% 2 10% 10% 2	1800
	21st to end	Day	23% 57% 5% 11% 4	1800
December	1st to 10th	Day	29% 36% 5% 18% 12%	2930
	11th to 20th	Day	41% 32% 5% 15% 6% 1	3370
	21st to end	Day	52% 28% 7% 8% 5% 1	4180
January	1st to 10th	Night	40% 40% 5% 8% 7%	4513
	11th to 20th	Night	43% 37% 6% 9% 5%	4276
	21st to end	Night	41% 40% 4 9% 5%	4532
February	1st to 10th	Night	20% 65% 3 7% 4	2318
	11th to 20th	Night	18% 64% 4 8% 5%	2219
	21st to end	Night	20% 64% 3 6% 5% 1	1884
March	1st to 10th	Night	36% 42% 5% 12% 4 1	3733
	11th to 20th	Night	17% 42% 8% 18% 14% 1	3492
	21st to end	Night	25% 42% 4 19% 9% 1	3817
April	1st to 10th	Night	18% 66% 4 7% 4	1915
	11th to 20th	Night	16% 65% 4 8% 6% 1	1857
	21st to end	Night	16% 65% 4 10% 4 1	1710
May	1st to 10th	Night	35% 44% 5% 11% 4 1	2840
	11th to 20th	Night	23% 43% 12% 19% 3	2813
	21st to end	Night	19% 44% 9% 17% 10% 2	3087
June	1st to 10th	Night	13% 65% 3 10% 7% 2	1676
	11th to 20th	Night	12% 65% 5% 7% 9% 2	1520
	21st to end	Night	11% 65% 7% 10% 7% 1	1520
July	1st to 10th	Night	22% 39% 6% 17% 13% 3	2490
	11th to 20th	Night	17% 37% 8% 25% 13% 1	2572
	21st to end	Night	33% 37% 9% 13% 6% 3	2988
August	1st to 10th	Night	22% 39% 9% 24% 6%	2814
	11th to 20th	Night	22% 38% 7% 21% 10%	2873
	21st to end	Night	11% 37% 11% 25% 15% 1	3476
September	1st to 10th	Night	11% 61% 5% 10% 10% 2	1976
	11th to 20th	Night	10% 60% 5% 12% 11% 2	2090
	21st to end	Night	14% 60% 6% 10% 9% 1	2090
October	1st to 10th	Night	11% 37% 3 15% 32% 1	3480
	11th to 20th	Night	12% 37% 6% 15% 29% 1	3676
	21st to end	Night	18% 36% 5% 15% 23% 4	4405
November	1st to 10th	Night	21% 55% 5% 10% 8% 1	2536
	11th to 20th	Night	19% 57% 3 10% 9% 2	2600
	21st to end	Night	25% 57% 5% 10% 4	2600
December	1st to 10th	Night	31% 35% 7% 16% 10%	4250
	11th to 20th	Night	39% 33% 9% 13% 7%	4824
	21st to end	Night	54% 27% 6% 9% 3	6784

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	28% 25% 31% 12% 3 1	288
	11th to 20th	Day	31% 29% 28% 10% 1	270
	21st to end	Day	31% 28% 32% 6% 3	297
February	1st to 10th	Day	30% 26% 32% 10% 1	270
	11th to 20th	Day	32% 28% 30% 7% 1 1	270
	21st to end	Day	34% 21% 36% 7% 2	225
March	1st to 10th	Day	27% 28% 34% 10% 1	270
	11th to 20th	Day	27% 24% 32% 12% 5%	447
	21st to end	Day	31% 21% 29% 13% 5%	506
April	1st to 10th	Day	26% 19% 29% 16% 8% 1	460
	11th to 20th	Day	26% 19% 28% 19% 6% 3	452
	21st to end	Day	23% 20% 36% 14% 6% 2	460
May	1st to 10th	Day	23% 18% 35% 14% 6% 4	463
	11th to 20th	Day	20% 14% 30% 22% 9% 5%	487
	21st to end	Day	14% 10% 29% 24% 14% 8%	529
June	1st to 10th	Day	13% 9% 26% 29% 17% 7%	518
	11th to 20th	Day	11% 7% 26% 34% 16% 6%	680
	21st to end	Day	11% 7% 30% 28% 16% 8%	680
July	1st to 10th	Day	15% 5% 20% 26% 20% 15%	671
	11th to 20th	Day	8% 5% 25% 30% 22% 10%	611
	21st to end	Day	13% 4 20% 33% 19% 11%	532
August	1st to 10th	Day	9% 4 20% 32% 22% 13%	486
	11th to 20th	Day	13% 6% 23% 31% 19% 9%	479
	21st to end	Day	9% 4 17% 30% 28% 11%	539
September	1st to 10th	Day	12% 6% 19% 30% 26% 8%	490
	11th to 20th	Day	11% 4 18% 32% 23% 13%	490
	21st to end	Day	20% 8% 22% 24% 19% 6%	490
October	1st to 10th	Day	11% 6% 25% 33% 19% 6%	490
	11th to 20th	Day	19% 15% 31% 20% 12% 4	490
	21st to end	Day	22% 17% 37% 19% 4 1	365
November	1st to 10th	Day	14% 18% 35% 25% 6% 2	300
	11th to 20th	Day	26% 21% 27% 21% 4 1	300
	21st to end	Day	28% 16% 35% 16% 4	300
December	1st to 10th	Day	26% 24% 35% 11% 4 1	300
	11th to 20th	Day	24% 23% 34% 13% 5%	300
	21st to end	Day	34% 21% 30% 12% 3	330
January	1st to 10th	Night	24% 21% 31% 20% 4	981
	11th to 20th	Night	31% 19% 32% 16% 3	851
	21st to end	Night	27% 19% 34% 18% 3	836
February	1st to 10th	Night	28% 16% 31% 22% 2	760
	11th to 20th	Night	26% 22% 32% 19% 1	743
	21st to end	Night	30% 17% 35% 17% 1	628
March	1st to 10th	Night	24% 20% 30% 22% 4	760
	11th to 20th	Night	24% 17% 33% 20% 6% 1	760
	21st to end	Night	24% 16% 32% 23% 6%	836
April	1st to 10th	Night	19% 14% 36% 25% 7%	585
	11th to 20th	Night	20% 14% 30% 25% 10% 1	563
	21st to end	Night	20% 11% 36% 24% 7% 1	570
May	1st to 10th	Night	21% 9% 32% 24% 13% 1	570
	11th to 20th	Night	17% 6% 29% 31% 16% 2	561
	21st to end	Night	11% 4 22% 33% 26% 4	617
June	1st to 10th	Night	12% 3 21% 39% 22% 2	570
	11th to 20th	Night	9% 4 18% 42% 24% 3	570
	21st to end	Night	6% 4 24% 36% 27% 3	570
July	1st to 10th	Night	13% 2 14% 33% 29% 9%	555
	11th to 20th	Night	6% 3 15% 38% 34% 4	552
	21st to end	Night	13% 2 13% 38% 30% 4	624
August	1st to 10th	Night	9% 2 11% 37% 36% 6%	567
	11th to 20th	Night	9% 2 13% 39% 32% 5%	564
	21st to end	Night	6% 3 13% 32% 39% 6%	627
September	1st to 10th	Night	14% 2 15% 34% 30% 4	646
	11th to 20th	Night	9% 4 17% 31% 34% 5%	760
	21st to end	Night	16% 7% 21% 30% 23% 2	760
October	1st to 10th	Night	11% 6% 23% 33% 23% 4	760
	11th to 20th	Night	18% 10% 26% 28% 16% 2	760
	21st to end	Night	22% 13% 31% 23% 11% 1	836
November	1st to 10th	Night	17% 12% 29% 26% 15% 1	780
	11th to 20th	Night	20% 17% 29% 24% 9% 1	800
	21st to end	Night	27% 15% 23% 28% 7% 1	800
December	1st to 10th	Night	28% 15% 31% 20% 6%	800
	11th to 20th	Night	26% 17% 29% 21% 6% 1	800
	21st to end	Night	30% 15% 32% 20% 3	1005

Page generated at 2025-01-04 03:24:04. Version ac07

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