Pickersville Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pickersville Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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% 6% 2 6% 4 4 5% 4 6% 8% 42%	100696
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	98204
Transparency	Day	39% 7% 12% 20% 17% 5%	100505
	Night	39% 7% 11% 19% 18% 5%	98065
Seeing	Day	15% 8% 23% 25% 21% 10%	15440
	Night	15% 7% 24% 34% 19% 2	25707

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	16% 5% 2 5% 3 3 3 2 3 5% 51%	2836
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 4 5% 53%	2840
	21st to end	Day	17% 8% 2 6% 3 4 3 3 4 5% 44%	3124
February	1st to 10th	Day	15% 6% 2 6% 4 4 4 3 5% 7% 43%	1710
	11th to 20th	Day	20% 6% 2 5% 3 3 3 2 5% 5% 45%	1705
	21st to end	Day	19% 7% 3 5% 4 4 4 3 4 6% 41%	1703
March	1st to 10th	Day	23% 7% 3 6% 4 3 4 4 5% 6% 36%	3435
	11th to 20th	Day	10% 4 2 5% 4 3 4 3 5% 6% 54%	3480
	21st to end	Day	17% 7% 2 6% 4 4 3 3 4 5% 44%	3815
April	1st to 10th	Day	10% 4 1 4 4 3 4 3 5% 7% 55%	2218
	11th to 20th	Day	10% 5% 2 5% 4 3 4 4 6% 7% 50%	2254
	21st to end	Day	12% 5% 2 5% 4 4 4 3 6% 7% 50%	2280
May	1st to 10th	Day	9% 6% 3 8% 6% 6% 6% 4 7% 10% 36%	3954
	11th to 20th	Day	16% 7% 2 8% 5% 5% 5% 4 6% 7% 36%	4081
	21st to end	Day	6% 4 2 5% 5% 4 5% 4 7% 10% 47%	4476
June	1st to 10th	Day	9% 6% 3 7% 6% 6% 5% 5% 7% 9% 38%	2470
	11th to 20th	Day	9% 5% 1 5% 5% 5% 6% 5% 7% 10% 42%	2470
	21st to end	Day	8% 5% 2 6% 6% 5% 6% 5% 8% 10% 39%	2470
July	1st to 10th	Day	7% 5% 2 7% 6% 6% 7% 5% 9% 12% 33%	4120
	11th to 20th	Day	10% 7% 3 9% 6% 6% 7% 5% 9% 11% 28%	4120
	21st to end	Day	9% 7% 4 9% 6% 6% 6% 5% 8% 11% 28%	4466
August	1st to 10th	Day	20% 10% 4 9% 6% 6% 5% 5% 8% 9% 20%	4104
	11th to 20th	Day	10% 6% 3 9% 6% 5% 6% 4 7% 10% 34%	3858
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 7% 10% 47%	4180
September	1st to 10th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 9% 42%	2280
	11th to 20th	Day	14% 6% 2 7% 4 5% 4 3 6% 7% 41%	2176
	21st to end	Day	18% 7% 3 6% 5% 5% 4 4 6% 7% 36%	2034
October	1st to 10th	Day	15% 6% 3 5% 3 3 3 3 5% 6% 47%	1900
	11th to 20th	Day	11% 5% 2 5% 3 3 2 2 4 5% 57%	1900
	21st to end	Day	11% 5% 2 5% 4 3 3 2 4 5% 57%	2090
November	1st to 10th	Day	13% 6% 2 4 3 2 3 3 4 6% 54%	1867
	11th to 20th	Day	14% 5% 2 5% 3 3 3 4 3 6% 51%	1900
	21st to end	Day	15% 5% 2 4 3 3 3 3 5% 7% 49%	1659
December	1st to 10th	Day	16% 7% 3 5% 4 5% 4 3 7% 6% 40%	1520
	11th to 20th	Day	16% 5% 2 5% 2 2 2 2 4 5% 55%	2077
	21st to end	Day	16% 7% 3 6% 4 4 4 3 5% 7% 42%	3124
January	1st to 10th	Night	15% 6% 2 5% 3 3 3 3 5% 6% 47%	4109
	11th to 20th	Night	14% 7% 2 7% 5% 4 4 4 5% 5% 44%	4120
	21st to end	Night	16% 7% 2 6% 4 4 3 3 4 5% 44%	4532
February	1st to 10th	Night	17% 6% 2 5% 3 4 4 3 4 7% 45%	2470
	11th to 20th	Night	19% 6% 2 6% 4 4 4 4 4 6% 42%	2360
	21st to end	Night	16% 6% 2 5% 3 4 4 3 5% 6% 46%	1746
March	1st to 10th	Night	25% 10% 3 7% 4 4 3 3 4 4 33%	3418
	11th to 20th	Night	14% 5% 2 4 4 4 4 3 5% 6% 50%	3480
	21st to end	Night	17% 5% 2 4 4 3 4 3 5% 5% 49%	3817
April	1st to 10th	Night	12% 5% 2 6% 3 4 4 3 5% 6% 49%	1962
	11th to 20th	Night	11% 4 2 6% 4 5% 4 2 5% 6% 50%	1875
	21st to end	Night	11% 3 2 4 4 4 4 4 6% 7% 50%	1900
May	1st to 10th	Night	10% 7% 3 8% 5% 4 5% 4 6% 9% 39%	2956
	11th to 20th	Night	16% 8% 4 7% 5% 5% 4 4 4 7% 36%	2812
	21st to end	Night	7% 5% 2 5% 4 5% 6% 4 7% 11% 44%	3079
June	1st to 10th	Night	10% 5% 3 5% 6% 5% 5% 5% 7% 11% 38%	1710
	11th to 20th	Night	10% 5% 2 6% 6% 4 5% 5% 6% 9% 41%	1710
	21st to end	Night	8% 5% 2 6% 6% 6% 6% 5% 9% 11% 38%	1710
July	1st to 10th	Night	9% 6% 3 8% 6% 6% 6% 4 10% 12% 30%	2840
	11th to 20th	Night	12% 7% 3 7% 6% 5% 6% 5% 8% 12% 29%	2840
	21st to end	Night	16% 10% 4 10% 5% 6% 5% 5% 6% 8% 27%	3087
August	1st to 10th	Night	19% 9% 4 9% 6% 5% 6% 4 6% 8% 24%	2825
	11th to 20th	Night	8% 6% 3 8% 6% 6% 7% 5% 7% 11% 32%	2936
	21st to end	Night	6% 4 2 5% 4 5% 5% 5% 8% 10% 45%	3476
September	1st to 10th	Night	10% 4 2 6% 5% 5% 4 3 6% 9% 46%	1900
	11th to 20th	Night	13% 6% 3 7% 5% 5% 5% 4 6% 7% 40%	2000
	21st to end	Night	18% 7% 3 8% 6% 5% 4 3 4 6% 38%	2144
October	1st to 10th	Night	15% 6% 2 5% 4 3 4 2 4 7% 49%	2280
	11th to 20th	Night	13% 4 2 5% 3 2 3 3 4 4 56%	2280
	21st to end	Night	11% 4 2 4 4 3 3 3 4 6% 56%	2508
November	1st to 10th	Night	14% 6% 2 4 3 2 3 3 3 5% 54%	2234
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 6% 49%	2280
	21st to end	Night	14% 4 2 5% 3 3 3 3 5% 7% 51%	2507
December	1st to 10th	Night	17% 8% 2 6% 4 4 3 3 5% 7% 41%	2660
	11th to 20th	Night	17% 6% 2 5% 3 3 3 3 4 5% 48%	3109
	21st to end	Night	17% 6% 2 6% 3 3 3 3 4 6% 47%	4532

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	37% 3 6% 24% 24% 6%	2837
	11th to 20th	Day	35% 3 5% 18% 30% 8%	2840
	21st to end	Day	44% 4 6% 15% 22% 10%	3124
February	1st to 10th	Day	40% 4 11% 19% 20% 6%	1710
	11th to 20th	Day	42% 4 6% 18% 24% 7%	1714
	21st to end	Day	44% 5% 9% 17% 19% 6%	1703
March	1st to 10th	Day	48% 5% 8% 16% 15% 8%	3435
	11th to 20th	Day	30% 6% 9% 16% 26% 12%	3480
	21st to end	Day	44% 4 7% 21% 19% 5%	3815
April	1st to 10th	Day	29% 5% 10% 23% 25% 8%	2218
	11th to 20th	Day	32% 6% 10% 22% 22% 8%	2254
	21st to end	Day	34% 5% 13% 23% 20% 5%	2280
May	1st to 10th	Day	41% 10% 17% 18% 13% 2	3989
	11th to 20th	Day	45% 8% 11% 21% 14% 1	4085
	21st to end	Day	29% 10% 15% 22% 20% 3	4489
June	1st to 10th	Day	40% 11% 14% 19% 15% 1	2470
	11th to 20th	Day	33% 10% 16% 23% 15% 2	2470
	21st to end	Day	35% 12% 16% 21% 12% 3	2470
July	1st to 10th	Day	37% 12% 18% 20% 10% 2	4055
	11th to 20th	Day	45% 14% 23% 13% 4 1	4051
	21st to end	Day	47% 13% 15% 15% 9% 1	4324
August	1st to 10th	Day	58% 10% 16% 11% 5%	4091
	11th to 20th	Day	43% 11% 13% 22% 10%	3897
	21st to end	Day	30% 8% 16% 31% 14% 1	4180
September	1st to 10th	Day	36% 10% 15% 17% 17% 5%	2280
	11th to 20th	Day	41% 7% 11% 15% 21% 4	2176
	21st to end	Day	46% 6% 10% 18% 15% 4	2034
October	1st to 10th	Day	38% 4 9% 21% 24% 3	1900
	11th to 20th	Day	30% 5% 9% 24% 23% 9%	1900
	21st to end	Day	31% 4 7% 21% 26% 10%	2090
November	1st to 10th	Day	33% 4 8% 19% 27% 9%	1867
	11th to 20th	Day	35% 3 9% 20% 25% 9%	1900
	21st to end	Day	35% 4 7% 23% 23% 8%	1659
December	1st to 10th	Day	44% 6% 11% 19% 17% 4	1520
	11th to 20th	Day	35% 3 6% 22% 25% 8%	2074
	21st to end	Day	42% 4 8% 21% 23% 2	3124
January	1st to 10th	Night	37% 4 8% 19% 27% 5%	4109
	11th to 20th	Night	40% 6% 8% 15% 24% 7%	4120
	21st to end	Night	42% 5% 7% 15% 23% 8%	4532
February	1st to 10th	Night	41% 4 8% 20% 21% 7%	2470
	11th to 20th	Night	44% 5% 9% 15% 20% 7%	2362
	21st to end	Night	39% 5% 9% 18% 21% 8%	1746
March	1st to 10th	Night	55% 5% 7% 13% 14% 5%	3418
	11th to 20th	Night	34% 6% 8% 11% 23% 17%	3480
	21st to end	Night	37% 6% 9% 22% 20% 6%	3817
April	1st to 10th	Night	35% 5% 11% 16% 23% 9%	1962
	11th to 20th	Night	34% 5% 10% 22% 21% 8%	1875
	21st to end	Night	31% 8% 13% 25% 19% 5%	1900
May	1st to 10th	Night	39% 10% 16% 21% 12% 2	2986
	11th to 20th	Night	46% 7% 11% 21% 15% 1	2813
	21st to end	Night	29% 10% 17% 25% 17% 2	3087
June	1st to 10th	Night	36% 11% 19% 21% 11% 2	1710
	11th to 20th	Night	37% 9% 18% 21% 13% 2	1710
	21st to end	Night	37% 12% 17% 22% 10% 2	1710
July	1st to 10th	Night	43% 13% 18% 19% 7% 1	2795
	11th to 20th	Night	44% 14% 24% 13% 5% 1	2786
	21st to end	Night	54% 9% 13% 14% 9%	2988
August	1st to 10th	Night	57% 9% 18% 13% 3	2814
	11th to 20th	Night	42% 12% 19% 19% 7% 1	2963
	21st to end	Night	30% 9% 14% 30% 15% 2	3476
September	1st to 10th	Night	36% 10% 14% 19% 15% 5%	1900
	11th to 20th	Night	41% 8% 13% 17% 18% 3	2000
	21st to end	Night	48% 7% 11% 17% 15% 3	2144
October	1st to 10th	Night	36% 6% 9% 20% 24% 5%	2280
	11th to 20th	Night	30% 5% 9% 21% 24% 11%	2280
	21st to end	Night	30% 4 8% 22% 25% 12%	2508
November	1st to 10th	Night	34% 4 7% 17% 27% 10%	2234
	11th to 20th	Night	36% 5% 9% 16% 24% 11%	2280
	21st to end	Night	34% 4 7% 21% 26% 8%	2507
December	1st to 10th	Night	43% 6% 10% 17% 18% 6%	2660
	11th to 20th	Night	40% 4 6% 20% 23% 8%	3111
	21st to end	Night	39% 4 7% 22% 25% 3	4532

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	17% 17% 42% 19% 5%	270
	11th to 20th	Day	18% 23% 31% 21% 7%	270
	21st to end	Day	16% 21% 38% 20% 6%	297
February	1st to 10th	Day	18% 15% 37% 24% 6% 1	270
	11th to 20th	Day	32% 12% 38% 17% 2	312
	21st to end	Day	22% 15% 34% 20% 7% 1	382
March	1st to 10th	Day	17% 16% 31% 26% 9% 1	460
	11th to 20th	Day	17% 14% 38% 24% 6% 1	460
	21st to end	Day	18% 13% 35% 25% 8% 2	506
April	1st to 10th	Day	17% 16% 30% 23% 12% 2	460
	11th to 20th	Day	12% 11% 30% 24% 18% 5%	452
	21st to end	Day	16% 9% 25% 24% 21% 4	460
May	1st to 10th	Day	10% 11% 35% 22% 16% 6%	463
	11th to 20th	Day	15% 4 20% 26% 26% 9%	487
	21st to end	Day	14% 4 16% 25% 24% 16%	529
June	1st to 10th	Day	12% 3 15% 34% 24% 12%	490
	11th to 20th	Day	11% 2 14% 26% 30% 16%	490
	21st to end	Day	8% 3 13% 27% 33% 16%	490
July	1st to 10th	Day	10% 3 8% 23% 33% 23%	485
	11th to 20th	Day	9% 2 8% 21% 37% 22%	484
	21st to end	Day	7% 2 11% 28% 38% 15%	532
August	1st to 10th	Day	14% 2 13% 22% 29% 19%	486
	11th to 20th	Day	12% 2 10% 23% 29% 24%	479
	21st to end	Day	12% 2 9% 24% 27% 26%	539
September	1st to 10th	Day	10% 2 14% 26% 26% 22%	490
	11th to 20th	Day	18% 4 11% 23% 30% 14%	490
	21st to end	Day	21% 3 18% 28% 22% 7%	490
October	1st to 10th	Day	16% 7% 18% 24% 24% 11%	490
	11th to 20th	Day	13% 6% 24% 29% 22% 6%	490
	21st to end	Day	12% 8% 21% 30% 23% 6%	539
November	1st to 10th	Day	19% 7% 23% 29% 17% 5%	459
	11th to 20th	Day	16% 8% 31% 32% 10% 2	460
	21st to end	Day	13% 10% 30% 26% 18% 2	268
December	1st to 10th	Day	18% 11% 38% 21% 11% 1	180
	11th to 20th	Day	20% 8% 39% 18% 12% 3	234
	21st to end	Day	22% 14% 31% 20% 10% 3	297
January	1st to 10th	Night	19% 11% 35% 28% 7% 1	760
	11th to 20th	Night	17% 11% 34% 31% 7%	760
	21st to end	Night	19% 9% 39% 30% 4	836
February	1st to 10th	Night	19% 9% 35% 32% 4	760
	11th to 20th	Night	23% 12% 40% 24% 1	743
	21st to end	Night	17% 13% 38% 28% 5%	628
March	1st to 10th	Night	18% 11% 33% 32% 6%	760
	11th to 20th	Night	17% 10% 39% 26% 7% 1	760
	21st to end	Night	16% 10% 37% 31% 6%	836
April	1st to 10th	Night	14% 13% 36% 30% 7%	760
	11th to 20th	Night	13% 9% 33% 34% 11% 1	751
	21st to end	Night	13% 7% 29% 41% 9% 1	760
May	1st to 10th	Night	8% 8% 33% 38% 13%	664
	11th to 20th	Night	15% 5% 22% 41% 17%	561
	21st to end	Night	10% 2 12% 42% 32% 2	617
June	1st to 10th	Night	11% 2 16% 44% 25% 2	570
	11th to 20th	Night	11% 2 14% 39% 29% 6%	570
	21st to end	Night	8% 2 13% 41% 34% 2	570
July	1st to 10th	Night	8% 2 9% 34% 42% 5%	555
	11th to 20th	Night	7% 2 7% 35% 43% 5%	552
	21st to end	Night	9% 3 10% 38% 38% 2	624
August	1st to 10th	Night	13% 2 9% 34% 38% 4	567
	11th to 20th	Night	12% 2 10% 33% 38% 5%	650
	21st to end	Night	11% 2 8% 34% 38% 6%	836
September	1st to 10th	Night	11% 2 11% 30% 39% 6%	760
	11th to 20th	Night	14% 4 12% 31% 35% 4	760
	21st to end	Night	22% 4 16% 32% 24% 2	760
October	1st to 10th	Night	17% 4 16% 31% 28% 4	760
	11th to 20th	Night	14% 4 26% 33% 22% 2	760
	21st to end	Night	14% 4 24% 34% 22% 2	836
November	1st to 10th	Night	15% 6% 23% 36% 17% 3	745
	11th to 20th	Night	14% 10% 27% 34% 13% 1	760
	21st to end	Night	15% 6% 28% 34% 17% 1	760
December	1st to 10th	Night	19% 10% 28% 36% 7%	760
	11th to 20th	Night	19% 7% 28% 36% 9% 1	760
	21st to end	Night	19% 9% 28% 35% 8%	836

Page generated at 2024-10-30 01:22:53. Version ac07

Copyright © 2024 Attilla Danko.