Picketwire Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Picketwire Observatory 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	3 5% 2 5% 3 4 5% 4 6% 8% 56%	105000
	Night	2 4 2 4 3 3 4 3 5% 7% 63%	102741
Transparency	Day	23% 7% 10% 21% 26% 14%	104751
	Night	20% 6% 10% 23% 28% 13%	102580
Seeing	Day	13% 19% 30% 23% 12% 3	15382
	Night	10% 17% 33% 27% 12% 2	25398

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	6% 2 5% 2 2 3 3 6% 9% 62%	2538
	11th to 20th	Day	1 3 2 4 2 2 3 3 4 5% 70%	2796
	21st to end	Day	1 10% 3 6% 3 3 3 3 5% 6% 58%	3146
February	1st to 10th	Day	1 4 2 6% 4 2 3 3 4 8% 63%	1767
	11th to 20th	Day	1 3 2 4 2 3 3 3 6% 8% 66%	1849
	21st to end	Day	1 4 3 5% 3 3 4 3 5% 6% 63%	1570
March	1st to 10th	Day	1 5% 3 5% 3 2 3 2 4 7% 65%	3130
	11th to 20th	Day	3 14% 4 6% 4 3 3 3 5% 6% 48%	3458
	21st to end	Day	2 7% 2 4 3 3 3 3 5% 8% 61%	4062
April	1st to 10th	Day	2 5% 1 4 3 3 4 4 6% 9% 58%	2280
	11th to 20th	Day	5% 6% 1 4 4 3 4 3 6% 8% 55%	2251
	21st to end	Day	4 7% 1 5% 4 4 4 3 7% 8% 51%	2280
May	1st to 10th	Day	6% 6% 2 4 3 3 3 3 5% 7% 59%	3864
	11th to 20th	Day	6% 6% 2 5% 4 5% 6% 5% 7% 7% 47%	4165
	21st to end	Day	3 2 1 3 3 3 4 4 7% 9% 62%	4825
June	1st to 10th	Day	3 3 1 4 4 5% 6% 6% 8% 10% 51%	2660
	11th to 20th	Day	3 3 1 3 3 3 5% 5% 7% 9% 60%	2660
	21st to end	Day	4 4 1 5% 4 5% 6% 6% 9% 9% 45%	2660
July	1st to 10th	Day	4 4 1 4 4 5% 6% 5% 9% 9% 48%	4430
	11th to 20th	Day	3 3 1 5% 5% 6% 9% 7% 10% 11% 41%	4430
	21st to end	Day	6% 4 2 6% 6% 6% 7% 6% 8% 9% 42%	4499
August	1st to 10th	Day	6% 4 1 7% 5% 7% 8% 8% 9% 11% 35%	3946
	11th to 20th	Day	4 3 1 5% 4 5% 6% 6% 8% 11% 48%	3726
	21st to end	Day	4 4 2 6% 5% 6% 7% 6% 10% 10% 40%	4180
September	1st to 10th	Day	6% 5% 2 6% 4 5% 5% 5% 8% 8% 48%	2280
	11th to 20th	Day	5% 3 1 3 2 4 5% 4 5% 7% 60%	2247
	21st to end	Day	5% 4 1 4 3 3 3 3 4 6% 63%	2090
October	1st to 10th	Day	4 3 1 3 2 3 2 3 4 5% 70%	3242
	11th to 20th	Day	4 3 1 3 2 2 4 3 6% 8% 62%	3150
	21st to end	Day	3 3 1 3 2 1 2 2 3 4 76%	3412
November	1st to 10th	Day	1 3 1 3 1 2 2 4 4 7% 72%	1709
	11th to 20th	Day	1 2 1 4 2 3 3 4 5% 7% 68%	1710
	21st to end	Day	1 5% 2 5% 2 3 3 3 5% 7% 65%	1710
December	1st to 10th	Day	3 2 5% 2 2 2 3 4 7% 70%	1558
	11th to 20th	Day	1 4 2 4 2 3 3 3 6% 8% 64%	1926
	21st to end	Day	1 3 2 6% 3 3 3 3 4 7% 65%	2794
January	1st to 10th	Night	3 3 6% 4 3 3 3 5% 6% 63%	4417
	11th to 20th	Night	2 1 4 2 3 4 3 4 6% 70%	4202
	21st to end	Night	1 5% 3 5% 4 3 3 3 4 6% 63%	4521
February	1st to 10th	Night	1 4 2 5% 3 3 3 3 4 6% 66%	2411
	11th to 20th	Night	1 4 2 5% 3 3 3 3 5% 6% 66%	2218
	21st to end	Night	4 2 4 3 2 3 2 4 5% 70%	1884
March	1st to 10th	Night	1 6% 2 3 2 2 3 2 3 5% 70%	3734
	11th to 20th	Night	3 13% 3 4 3 3 3 3 5% 6% 54%	3505
	21st to end	Night	1 6% 3 4 3 2 3 3 5% 6% 66%	3583
April	1st to 10th	Night	2 4 1 3 2 2 3 3 5% 6% 69%	1900
	11th to 20th	Night	3 5% 1 5% 3 3 3 3 4 7% 64%	1877
	21st to end	Night	4 6% 2 3 3 3 4 4 5% 6% 61%	1900
May	1st to 10th	Night	5% 6% 2 2 2 3 3 3 4 5% 66%	3106
	11th to 20th	Night	8% 6% 2 4 3 4 4 3 6% 8% 52%	2736
	21st to end	Night	3 3 1 2 2 2 3 3 5% 7% 71%	2762
June	1st to 10th	Night	2 4 1 3 3 4 4 4 7% 9% 60%	1520
	11th to 20th	Night	2 3 1 3 2 4 4 4 5% 8% 65%	1520
	21st to end	Night	5% 4 2 3 3 5% 4 6% 8% 10% 51%	1520
July	1st to 10th	Night	6% 4 2 4 4 5% 6% 5% 8% 9% 46%	2540
	11th to 20th	Night	2 2 1 4 4 4 7% 6% 9% 12% 49%	2540
	21st to end	Night	4 3 1 4 4 4 5% 5% 10% 10% 50%	3046
August	1st to 10th	Night	4 4 2 6% 6% 8% 7% 6% 9% 10% 37%	2991
	11th to 20th	Night	3 2 1 4 3 4 5% 5% 11% 15% 47%	3113
	21st to end	Night	3 3 2 5% 4 6% 7% 6% 10% 13% 41%	3487
September	1st to 10th	Night	6% 3 1 3 3 3 4 4 7% 10% 55%	1900
	11th to 20th	Night	5% 3 1 2 2 2 3 2 4 8% 67%	1933
	21st to end	Night	4 4 1 3 2 2 2 3 4 6% 69%	2090
October	1st to 10th	Night	3 3 1 2 2 2 3 2 3 5% 74%	3722
	11th to 20th	Night	5% 3 1 2 2 2 3 3 4 6% 68%	3778
	21st to end	Night	2 3 2 4 2 2 2 2 2 3 76%	4120
November	1st to 10th	Night	1 3 1 2 2 1 2 3 4 5% 75%	2464
	11th to 20th	Night	1 2 1 4 2 2 2 2 4 5% 76%	2470
	21st to end	Night	1 4 1 3 3 2 3 3 5% 6% 68%	2470
December	1st to 10th	Night	3 1 4 2 3 3 3 6% 8% 66%	2617
	11th to 20th	Night	1 3 1 4 2 3 3 3 5% 8% 67%	3271
	21st to end	Night	1 4 1 5% 3 3 3 3 5% 7% 65%	4873

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	17% 5% 8% 28% 31% 10%	2539
	11th to 20th	Day	15% 5% 7% 25% 41% 8%	2796
	21st to end	Day	24% 4 8% 25% 30% 8%	3146
February	1st to 10th	Day	21% 3 9% 26% 27% 14%	1767
	11th to 20th	Day	17% 4 8% 25% 31% 15%	1859
	21st to end	Day	20% 4 6% 16% 30% 24%	1570
March	1st to 10th	Day	19% 3 5% 15% 39% 17%	3130
	11th to 20th	Day	35% 4 8% 21% 27% 6%	3458
	21st to end	Day	21% 3 8% 25% 34% 7%	4062
April	1st to 10th	Day	21% 6% 8% 23% 25% 17%	2280
	11th to 20th	Day	25% 6% 7% 23% 22% 16%	2254
	21st to end	Day	26% 7% 11% 21% 27% 9%	2280
May	1st to 10th	Day	23% 6% 9% 17% 23% 22%	3864
	11th to 20th	Day	30% 9% 12% 17% 20% 12%	4169
	21st to end	Day	16% 7% 11% 17% 23% 26%	4825
June	1st to 10th	Day	24% 9% 13% 21% 19% 13%	2660
	11th to 20th	Day	18% 7% 11% 17% 21% 26%	2660
	21st to end	Day	28% 9% 12% 18% 19% 14%	2660
July	1st to 10th	Day	26% 11% 12% 15% 22% 15%	4361
	11th to 20th	Day	27% 12% 15% 26% 15% 4	4355
	21st to end	Day	32% 11% 13% 20% 18% 6%	4357
August	1st to 10th	Day	35% 14% 20% 18% 9% 5%	3932
	11th to 20th	Day	24% 12% 16% 20% 16% 13%	3762
	21st to end	Day	30% 13% 15% 20% 18% 4	4179
September	1st to 10th	Day	29% 8% 10% 21% 20% 11%	2280
	11th to 20th	Day	21% 7% 10% 17% 27% 18%	2247
	21st to end	Day	21% 5% 9% 19% 33% 14%	2090
October	1st to 10th	Day	17% 4 6% 19% 35% 19%	3242
	11th to 20th	Day	16% 6% 8% 24% 31% 14%	3150
	21st to end	Day	13% 3 4 16% 40% 25%	3412
November	1st to 10th	Day	12% 4 5% 23% 36% 21%	1709
	11th to 20th	Day	15% 3 7% 26% 35% 14%	1710
	21st to end	Day	19% 3 6% 17% 34% 21%	1710
December	1st to 10th	Day	15% 4 10% 27% 31% 14%	1558
	11th to 20th	Day	19% 4 10% 22% 31% 14%	1924
	21st to end	Day	18% 3 9% 23% 31% 17%	2794
January	1st to 10th	Night	22% 3 8% 23% 35% 9%	4417
	11th to 20th	Night	17% 3 6% 28% 35% 10%	4202
	21st to end	Night	20% 6% 8% 28% 30% 8%	4521
February	1st to 10th	Night	20% 4 8% 27% 27% 14%	2411
	11th to 20th	Night	19% 3 10% 26% 28% 13%	2218
	21st to end	Night	17% 3 5% 20% 36% 19%	1884
March	1st to 10th	Night	18% 3 6% 14% 40% 19%	3734
	11th to 20th	Night	29% 6% 9% 20% 27% 9%	3505
	21st to end	Night	19% 4 7% 30% 33% 6%	3583
April	1st to 10th	Night	17% 4 7% 28% 28% 15%	1900
	11th to 20th	Night	21% 4 9% 25% 27% 13%	1877
	21st to end	Night	23% 7% 12% 25% 25% 8%	1900
May	1st to 10th	Night	21% 5% 8% 18% 24% 24%	3106
	11th to 20th	Night	28% 7% 12% 26% 17% 9%	2737
	21st to end	Night	13% 6% 11% 16% 28% 25%	2762
June	1st to 10th	Night	19% 8% 14% 23% 20% 16%	1520
	11th to 20th	Night	17% 6% 10% 18% 26% 24%	1520
	21st to end	Night	24% 10% 13% 18% 22% 14%	1520
July	1st to 10th	Night	28% 11% 16% 15% 13% 16%	2500
	11th to 20th	Night	23% 9% 22% 32% 10% 4	2492
	21st to end	Night	24% 12% 18% 25% 15% 7%	2950
August	1st to 10th	Night	36% 14% 21% 16% 9% 5%	2982
	11th to 20th	Night	21% 11% 24% 22% 15% 8%	3143
	21st to end	Night	27% 12% 20% 24% 13% 3	3487
September	1st to 10th	Night	22% 8% 14% 26% 22% 9%	1900
	11th to 20th	Night	17% 5% 12% 18% 30% 18%	1933
	21st to end	Night	17% 5% 9% 23% 33% 13%	2090
October	1st to 10th	Night	15% 4 7% 18% 35% 21%	3722
	11th to 20th	Night	16% 5% 8% 23% 33% 13%	3778
	21st to end	Night	16% 3 4 19% 37% 22%	4120
November	1st to 10th	Night	12% 2 6% 22% 37% 21%	2464
	11th to 20th	Night	13% 2 5% 27% 35% 17%	2470
	21st to end	Night	17% 3 7% 21% 32% 20%	2470
December	1st to 10th	Night	16% 5% 9% 30% 29% 12%	2617
	11th to 20th	Night	17% 3 9% 22% 36% 14%	3272
	21st to end	Night	18% 4 11% 23% 28% 16%	4873

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	20% 21% 30% 17% 12%	270
	11th to 20th	Day	22% 27% 28% 19% 3 1	270
	21st to end	Day	11% 24% 35% 21% 9%	297
February	1st to 10th	Day	20% 31% 34% 12% 3 1	270
	11th to 20th	Day	22% 28% 32% 13% 4	270
	21st to end	Day	32% 28% 29% 10%	225
March	1st to 10th	Day	23% 28% 26% 19% 3	270
	11th to 20th	Day	20% 27% 32% 16% 5% 1	441
	21st to end	Day	28% 34% 25% 10% 2	506
April	1st to 10th	Day	22% 34% 30% 9% 4 1	460
	11th to 20th	Day	25% 33% 28% 10% 2	452
	21st to end	Day	21% 35% 30% 13% 2	460
May	1st to 10th	Day	18% 28% 37% 11% 5% 1	501
	11th to 20th	Day	12% 19% 35% 23% 9% 2	675
	21st to end	Day	13% 21% 33% 22% 10% 1	734
June	1st to 10th	Day	6% 15% 29% 33% 15% 4	680
	11th to 20th	Day	7% 16% 36% 25% 13% 3	680
	21st to end	Day	6% 13% 36% 26% 14% 5%	680
July	1st to 10th	Day	6% 8% 26% 32% 22% 6%	671
	11th to 20th	Day	5% 4 17% 35% 28% 10%	668
	21st to end	Day	8% 5% 17% 36% 26% 8%	563
August	1st to 10th	Day	10% 5% 22% 37% 20% 7%	487
	11th to 20th	Day	5% 6% 30% 38% 17% 5%	477
	21st to end	Day	6% 7% 30% 35% 16% 5%	539
September	1st to 10th	Day	7% 9% 29% 34% 18% 5%	490
	11th to 20th	Day	8% 12% 33% 31% 13% 3	457
	21st to end	Day	12% 13% 30% 23% 17% 5%	300
October	1st to 10th	Day	15% 15% 25% 26% 13% 6%	300
	11th to 20th	Day	12% 21% 29% 24% 9% 4	300
	21st to end	Day	17% 18% 31% 22% 11% 2	330
November	1st to 10th	Day	15% 20% 33% 21% 11%	282
	11th to 20th	Day	11% 23% 30% 23% 11% 2	270
	21st to end	Day	14% 20% 36% 18% 9% 3	270
December	1st to 10th	Day	16% 28% 33% 17% 6% 1	270
	11th to 20th	Day	14% 26% 32% 21% 6% 1	270
	21st to end	Day	23% 29% 32% 13% 4	297
January	1st to 10th	Night	11% 20% 33% 24% 9% 2	950
	11th to 20th	Night	14% 22% 33% 21% 8% 1	813
	21st to end	Night	6% 22% 37% 25% 8% 1	836
February	1st to 10th	Night	10% 25% 41% 19% 4	760
	11th to 20th	Night	13% 24% 41% 16% 4	744
	21st to end	Night	14% 27% 42% 15% 2	628
March	1st to 10th	Night	15% 28% 34% 19% 4 1	760
	11th to 20th	Night	10% 19% 39% 24% 7% 1	760
	21st to end	Night	15% 26% 37% 19% 3	694
April	1st to 10th	Night	13% 26% 44% 15% 3	570
	11th to 20th	Night	13% 24% 37% 21% 5%	563
	21st to end	Night	14% 21% 39% 20% 6%	570
May	1st to 10th	Night	11% 18% 38% 27% 5% 1	570
	11th to 20th	Night	12% 15% 31% 29% 11% 2	561
	21st to end	Night	10% 17% 36% 27% 10% 1	617
June	1st to 10th	Night	4 12% 31% 36% 15% 2	570
	11th to 20th	Night	3 14% 42% 32% 9% 1	570
	21st to end	Night	5% 7% 32% 34% 21% 2	570
July	1st to 10th	Night	8% 4 24% 35% 27% 3	555
	11th to 20th	Night	4 3 18% 40% 31% 5%	552
	21st to end	Night	7% 2 12% 35% 38% 7%	624
August	1st to 10th	Night	4 4 14% 39% 34% 5%	567
	11th to 20th	Night	7% 3 16% 43% 28% 3	564
	21st to end	Night	5% 4 21% 37% 29% 4	627
September	1st to 10th	Night	6% 4 21% 41% 23% 4	570
	11th to 20th	Night	7% 6% 34% 31% 19% 3	570
	21st to end	Night	7% 12% 26% 36% 15% 2	570
October	1st to 10th	Night	8% 14% 33% 30% 13% 2	708
	11th to 20th	Night	6% 16% 35% 29% 12% 3	760
	21st to end	Night	12% 16% 32% 25% 12% 3	836
November	1st to 10th	Night	10% 15% 35% 28% 10% 1	944
	11th to 20th	Night	9% 17% 37% 26% 9% 2	950
	21st to end	Night	10% 16% 35% 27% 10% 1	950
December	1st to 10th	Night	11% 20% 37% 24% 7% 1	950
	11th to 20th	Night	13% 22% 35% 23% 7% 1	950
	21st to end	Night	13% 22% 36% 23% 4 1	1045

Page generated at 2024-11-03 00:11:16. Version ac07

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