Pettigrew State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pettigrew State Park clear sky chart from 2005-11-06 to 2024-11-05.

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% 7% 2 7% 5% 5% 5% 4 6% 8% 39%	100833
	Night	14% 7% 2 6% 4 4 4 4 5% 7% 42%	98130
Transparency	Day	41% 6% 12% 21% 16% 4	104474
	Night	40% 5% 12% 21% 17% 5%	102628
Seeing	Day	18% 12% 26% 25% 14% 5%	15417
	Night	17% 11% 27% 30% 13% 2	25089

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% 6% 2 4 2 4 3 3 4 5% 52%	2786
	11th to 20th	Day	11% 7% 2 6% 4 4 3 3 4 6% 49%	2840
	21st to end	Day	14% 12% 3 6% 5% 4 3 3 4 7% 39%	3124
February	1st to 10th	Day	14% 8% 2 7% 4 4 3 4 5% 7% 43%	1710
	11th to 20th	Day	19% 6% 3 5% 5% 4 3 3 4 5% 44%	1839
	21st to end	Day	15% 8% 2 5% 4 4 5% 3 6% 7% 41%	1570
March	1st to 10th	Day	24% 10% 2 5% 3 3 4 3 5% 6% 36%	3343
	11th to 20th	Day	12% 5% 2 4 4 3 3 3 5% 5% 53%	3480
	21st to end	Day	17% 6% 2 6% 4 4 3 3 4 5% 47%	3925
April	1st to 10th	Day	13% 6% 1 4 3 4 4 3 4 6% 52%	2280
	11th to 20th	Day	9% 5% 1 6% 4 4 5% 4 5% 7% 49%	2254
	21st to end	Day	11% 5% 2 5% 5% 4 4 3 5% 8% 47%	2280
May	1st to 10th	Day	10% 6% 3 8% 5% 6% 5% 5% 7% 9% 35%	3765
	11th to 20th	Day	19% 7% 2 8% 6% 5% 5% 4 6% 7% 31%	4002
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 4 7% 9% 42%	4823
June	1st to 10th	Day	10% 5% 2 7% 6% 5% 6% 5% 7% 10% 36%	2660
	11th to 20th	Day	9% 4 1 6% 6% 5% 6% 6% 8% 10% 38%	2660
	21st to end	Day	6% 6% 2 8% 6% 6% 7% 7% 9% 11% 33%	2660
July	1st to 10th	Day	8% 6% 3 7% 6% 6% 7% 6% 9% 12% 30%	4354
	11th to 20th	Day	10% 8% 3 11% 7% 6% 7% 7% 8% 10% 23%	4120
	21st to end	Day	11% 8% 4 10% 7% 7% 7% 5% 7% 9% 26%	4466
August	1st to 10th	Day	18% 11% 4 10% 7% 6% 6% 5% 6% 8% 19%	4016
	11th to 20th	Day	8% 8% 2 8% 6% 6% 6% 5% 7% 9% 35%	3730
	21st to end	Day	7% 5% 2 7% 7% 6% 7% 5% 7% 9% 38%	4180
September	1st to 10th	Day	12% 7% 3 7% 6% 5% 6% 5% 7% 9% 34%	2280
	11th to 20th	Day	15% 7% 2 8% 5% 5% 5% 5% 5% 7% 36%	2280
	21st to end	Day	20% 8% 3 8% 3 4 4 4 6% 7% 35%	2034
October	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	1900
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 4 5% 50%	1900
	21st to end	Day	12% 6% 2 7% 3 4 3 3 4 5% 51%	2090
November	1st to 10th	Day	16% 6% 1 5% 3 3 3 2 4 7% 48%	1860
	11th to 20th	Day	16% 5% 2 4 3 3 3 2 5% 5% 51%	1710
	21st to end	Day	15% 5% 2 4 3 2 3 4 5% 6% 50%	1710
December	1st to 10th	Day	17% 7% 2 6% 5% 5% 4 4 5% 6% 40%	1520
	11th to 20th	Day	16% 7% 2 5% 2 2 3 2 4 5% 52%	1910
	21st to end	Day	15% 7% 2 6% 3 3 4 3 4 7% 46%	2772
January	1st to 10th	Night	15% 8% 2 5% 4 3 4 3 5% 6% 45%	4141
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 4 6% 6% 41%	4120
	21st to end	Night	16% 8% 2 6% 4 4 4 3 4 6% 42%	4532
February	1st to 10th	Night	19% 7% 2 5% 3 3 3 4 6% 6% 43%	2470
	11th to 20th	Night	19% 9% 2 6% 3 3 4 3 4 5% 41%	2225
	21st to end	Night	16% 7% 2 5% 4 3 4 3 6% 6% 45%	1884
March	1st to 10th	Night	27% 10% 2 5% 5% 4 4 3 4 5% 32%	3493
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 51%	3480
	21st to end	Night	18% 6% 2 4 3 3 3 3 4 6% 48%	3705
April	1st to 10th	Night	12% 6% 2 6% 4 4 3 4 5% 7% 47%	1900
	11th to 20th	Night	10% 6% 2 6% 4 5% 4 4 5% 7% 46%	1875
	21st to end	Night	11% 6% 2 5% 4 4 4 4 5% 7% 48%	1900
May	1st to 10th	Night	10% 5% 3 8% 6% 6% 6% 4 6% 8% 38%	3130
	11th to 20th	Night	20% 7% 2 6% 5% 4 4 3 5% 7% 36%	2915
	21st to end	Night	8% 5% 3 7% 4 5% 5% 4 7% 10% 44%	2732
June	1st to 10th	Night	10% 6% 2 6% 5% 4 5% 5% 6% 10% 41%	1520
	11th to 20th	Night	8% 4 2 5% 5% 4 5% 7% 8% 12% 39%	1520
	21st to end	Night	8% 5% 2 6% 5% 5% 6% 6% 8% 10% 40%	1520
July	1st to 10th	Night	7% 4 2 6% 5% 6% 7% 5% 8% 13% 37%	2601
	11th to 20th	Night	8% 8% 3 8% 6% 5% 6% 5% 8% 12% 30%	2840
	21st to end	Night	13% 7% 3 8% 7% 6% 6% 5% 7% 8% 30%	3087
August	1st to 10th	Night	16% 10% 3 9% 5% 5% 5% 4 6% 10% 27%	2879
	11th to 20th	Night	8% 6% 3 9% 6% 6% 5% 5% 7% 8% 37%	3097
	21st to end	Night	6% 5% 2 7% 5% 4 7% 5% 8% 10% 40%	3476
September	1st to 10th	Night	10% 6% 2 6% 5% 6% 5% 4 6% 8% 41%	1900
	11th to 20th	Night	13% 7% 3 7% 4 4 4 4 6% 9% 39%	1900
	21st to end	Night	18% 7% 2 7% 5% 5% 4 4 6% 7% 35%	2139
October	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 6% 49%	2280
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 5% 52%	2280
	21st to end	Night	11% 5% 2 5% 2 3 3 3 5% 6% 55%	2508
November	1st to 10th	Night	15% 5% 2 6% 3 3 4 3 4 5% 49%	2317
	11th to 20th	Night	17% 7% 2 4 4 3 3 3 4 6% 46%	2470
	21st to end	Night	12% 6% 2 5% 3 3 3 3 5% 7% 50%	2470
December	1st to 10th	Night	16% 9% 3 6% 4 4 4 4 5% 5% 40%	2655
	11th to 20th	Night	17% 6% 2 5% 4 4 3 3 4 6% 47%	3285
	21st to end	Night	14% 7% 2 5% 4 3 4 3 5% 7% 47%	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	35% 4 6% 29% 22% 4	2787
	11th to 20th	Day	37% 4 7% 18% 28% 6%	2840
	21st to end	Day	47% 4 8% 17% 17% 7%	3124
February	1st to 10th	Day	41% 4 10% 24% 18% 3	1710
	11th to 20th	Day	45% 3 8% 18% 21% 6%	1848
	21st to end	Day	43% 4 10% 20% 18% 5%	1570
March	1st to 10th	Day	51% 4 10% 16% 13% 6%	3343
	11th to 20th	Day	33% 4 7% 19% 24% 13%	3480
	21st to end	Day	41% 3 10% 24% 18% 5%	3925
April	1st to 10th	Day	33% 4 11% 22% 24% 6%	2280
	11th to 20th	Day	34% 4 10% 24% 21% 7%	2254
	21st to end	Day	34% 6% 12% 26% 18% 4	2280
May	1st to 10th	Day	43% 7% 18% 21% 10% 2	3800
	11th to 20th	Day	51% 5% 10% 23% 9% 1	4006
	21st to end	Day	37% 7% 13% 30% 12% 1	4837
June	1st to 10th	Day	42% 8% 14% 21% 14% 1	2660
	11th to 20th	Day	38% 8% 18% 22% 13% 1	2660
	21st to end	Day	40% 9% 18% 21% 11% 1	2660
July	1st to 10th	Day	40% 11% 19% 19% 10% 1	4286
	11th to 20th	Day	51% 12% 19% 13% 4 1	4051
	21st to end	Day	51% 10% 12% 17% 9%	4324
August	1st to 10th	Day	60% 8% 17% 11% 4	4003
	11th to 20th	Day	41% 10% 14% 22% 13%	3766
	21st to end	Day	39% 8% 15% 25% 11% 2	4180
September	1st to 10th	Day	46% 8% 14% 15% 14% 3	2280
	11th to 20th	Day	46% 6% 10% 19% 17% 2	2280
	21st to end	Day	49% 4 10% 19% 15% 3	2034
October	1st to 10th	Day	35% 5% 9% 22% 24% 5%	3160
	11th to 20th	Day	27% 3 6% 20% 27% 16%	3140
	21st to end	Day	24% 4 6% 29% 31% 6%	3428
November	1st to 10th	Day	38% 3 10% 20% 24% 4	1860
	11th to 20th	Day	36% 3 9% 22% 23% 6%	1710
	21st to end	Day	35% 4 9% 26% 23% 4	1710
December	1st to 10th	Day	45% 4 11% 21% 15% 3	1520
	11th to 20th	Day	37% 2 7% 27% 19% 8%	1906
	21st to end	Day	39% 4 9% 25% 21% 2	2772
January	1st to 10th	Night	40% 4 6% 24% 21% 5%	4141
	11th to 20th	Night	44% 3 7% 19% 22% 5%	4120
	21st to end	Night	43% 5% 7% 18% 20% 7%	4532
February	1st to 10th	Night	41% 4 9% 24% 17% 5%	2470
	11th to 20th	Night	46% 4 8% 17% 19% 6%	2227
	21st to end	Night	40% 4 9% 21% 19% 7%	1884
March	1st to 10th	Night	56% 3 9% 16% 13% 3	3493
	11th to 20th	Night	36% 4 8% 14% 24% 14%	3480
	21st to end	Night	39% 3 9% 27% 16% 5%	3705
April	1st to 10th	Night	37% 4 12% 17% 24% 5%	1900
	11th to 20th	Night	37% 5% 12% 24% 19% 4	1875
	21st to end	Night	35% 5% 11% 28% 17% 4	1900
May	1st to 10th	Night	43% 7% 18% 22% 8% 2	3160
	11th to 20th	Night	48% 5% 12% 24% 10% 1	2916
	21st to end	Night	34% 7% 20% 26% 12% 1	2739
June	1st to 10th	Night	38% 7% 16% 25% 13% 1	1520
	11th to 20th	Night	33% 10% 21% 23% 12% 1	1520
	21st to end	Night	36% 8% 20% 25% 11%	1520
July	1st to 10th	Night	37% 11% 23% 18% 9% 1	2559
	11th to 20th	Night	44% 11% 26% 15% 4	2786
	21st to end	Night	48% 12% 14% 16% 9%	2988
August	1st to 10th	Night	52% 8% 21% 16% 3	2868
	11th to 20th	Night	41% 9% 18% 21% 11%	3127
	21st to end	Night	35% 7% 17% 27% 12% 1	3476
September	1st to 10th	Night	39% 9% 19% 17% 14% 2	1900
	11th to 20th	Night	42% 7% 12% 21% 15% 3	1900
	21st to end	Night	47% 6% 11% 21% 13% 1	2139
October	1st to 10th	Night	38% 5% 7% 21% 26% 3	3800
	11th to 20th	Night	26% 3 6% 18% 28% 20%	3779
	21st to end	Night	22% 3 7% 29% 29% 10%	4120
November	1st to 10th	Night	38% 4 7% 23% 23% 5%	2317
	11th to 20th	Night	40% 4 9% 17% 23% 7%	2470
	21st to end	Night	34% 3 9% 25% 23% 5%	2470
December	1st to 10th	Night	46% 4 12% 17% 17% 4	2655
	11th to 20th	Night	40% 3 8% 20% 23% 6%	3288
	21st to end	Night	37% 4 11% 24% 21% 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	25% 28% 33% 12% 2	258
	11th to 20th	Day	24% 27% 34% 13% 1	270
	21st to end	Day	27% 25% 33% 11% 3	297
February	1st to 10th	Day	26% 21% 37% 12% 4	270
	11th to 20th	Day	32% 24% 30% 12% 2	447
	21st to end	Day	27% 22% 32% 15% 3 1	382
March	1st to 10th	Day	25% 17% 36% 15% 5% 1	460
	11th to 20th	Day	24% 24% 32% 15% 4 2	460
	21st to end	Day	22% 21% 36% 15% 6%	506
April	1st to 10th	Day	25% 24% 30% 15% 5% 2	460
	11th to 20th	Day	17% 18% 32% 22% 8% 4	452
	21st to end	Day	15% 15% 34% 25% 10% 2	460
May	1st to 10th	Day	17% 15% 33% 25% 7% 2	463
	11th to 20th	Day	20% 5% 30% 31% 12% 2	487
	21st to end	Day	17% 5% 24% 29% 19% 6%	529
June	1st to 10th	Day	13% 7% 28% 32% 16% 5%	490
	11th to 20th	Day	11% 7% 19% 36% 20% 7%	490
	21st to end	Day	9% 4 22% 36% 21% 7%	490
July	1st to 10th	Day	10% 4 15% 34% 27% 9%	485
	11th to 20th	Day	11% 4 12% 37% 29% 8%	484
	21st to end	Day	11% 3 19% 39% 23% 5%	532
August	1st to 10th	Day	16% 6% 19% 31% 21% 8%	486
	11th to 20th	Day	13% 3 15% 28% 28% 13%	479
	21st to end	Day	13% 3 17% 32% 24% 11%	539
September	1st to 10th	Day	15% 4 22% 25% 20% 13%	490
	11th to 20th	Day	19% 6% 20% 29% 18% 8%	490
	21st to end	Day	26% 6% 20% 24% 17% 7%	490
October	1st to 10th	Day	19% 6% 23% 27% 17% 8%	490
	11th to 20th	Day	17% 11% 25% 28% 14% 4	490
	21st to end	Day	15% 12% 25% 26% 17% 4	539
November	1st to 10th	Day	21% 11% 30% 23% 12% 4	454
	11th to 20th	Day	20% 16% 30% 23% 9% 2	370
	21st to end	Day	21% 16% 23% 22% 17% 2	370
December	1st to 10th	Day	25% 25% 31% 13% 6% 1	180
	11th to 20th	Day	24% 22% 28% 17% 9%	180
	21st to end	Day	21% 20% 30% 18% 10% 1	198
January	1st to 10th	Night	21% 22% 29% 23% 5%	760
	11th to 20th	Night	20% 17% 32% 24% 7%	760
	21st to end	Night	21% 19% 34% 22% 4	836
February	1st to 10th	Night	22% 18% 31% 26% 3	760
	11th to 20th	Night	28% 22% 31% 16% 2	743
	21st to end	Night	23% 20% 33% 21% 4	628
March	1st to 10th	Night	21% 15% 37% 22% 5%	760
	11th to 20th	Night	22% 14% 39% 20% 5%	760
	21st to end	Night	19% 20% 33% 22% 5%	836
April	1st to 10th	Night	18% 19% 37% 22% 4	760
	11th to 20th	Night	15% 15% 40% 22% 7%	751
	21st to end	Night	15% 11% 38% 30% 6% 1	760
May	1st to 10th	Night	15% 13% 38% 27% 7% 1	760
	11th to 20th	Night	19% 8% 29% 33% 10%	625
	21st to end	Night	11% 4 21% 45% 18% 1	411
June	1st to 10th	Night	12% 3 24% 45% 15% 1	380
	11th to 20th	Night	9% 3 23% 43% 20% 3	380
	21st to end	Night	9% 2 20% 50% 18%	380
July	1st to 10th	Night	8% 2 14% 46% 26% 3	410
	11th to 20th	Night	8% 1 12% 44% 28% 7%	552
	21st to end	Night	10% 4 17% 41% 25% 3	624
August	1st to 10th	Night	15% 3 11% 40% 27% 4	595
	11th to 20th	Night	9% 2 14% 41% 27% 6%	750
	21st to end	Night	13% 3 12% 36% 31% 6%	836
September	1st to 10th	Night	12% 3 17% 33% 27% 8%	760
	11th to 20th	Night	17% 4 17% 35% 23% 4	760
	21st to end	Night	22% 4 17% 33% 20% 3	760
October	1st to 10th	Night	16% 4 22% 30% 24% 4	760
	11th to 20th	Night	19% 8% 26% 30% 16% 2	760
	21st to end	Night	15% 9% 26% 29% 18% 3	836
November	1st to 10th	Night	18% 9% 26% 30% 14% 3	760
	11th to 20th	Night	22% 13% 27% 26% 11% 1	760
	21st to end	Night	16% 14% 28% 26% 16% 1	760
December	1st to 10th	Night	22% 15% 29% 27% 7%	760
	11th to 20th	Night	19% 14% 31% 28% 8%	760
	21st to end	Night	19% 17% 29% 28% 7%	836

Page generated at 2024-11-03 02:11:06. Version ac07

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