Annville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Annville clear sky chart from 2005-11-06 to 2024-11-30.

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	16% 6% 2 6% 4 4 5% 4 6% 8% 38%	101595
	Night	17% 7% 2 6% 4 4 4 4 5% 7% 40%	98018
Transparency	Day	41% 7% 12% 23% 14% 2	105197
	Night	41% 7% 12% 23% 15% 2	102504
Seeing	Day	20% 15% 28% 22% 12% 4	14966
	Night	19% 13% 29% 28% 11% 1	24341

By Month

Percentage Cloud Cover NE (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	14% 7% 2 6% 5% 5% 5% 4 6% 5% 41%	2517
	11th to 20th	Day	14% 12% 4 9% 5% 6% 6% 4 6% 7% 28%	2713
	21st to end	Day	20% 10% 4 8% 5% 4 4 4 5% 5% 30%	3124
February	1st to 10th	Day	16% 8% 2 7% 4 5% 6% 4 7% 6% 35%	1710
	11th to 20th	Day	14% 8% 3 6% 5% 5% 5% 3 6% 7% 38%	1728
	21st to end	Day	18% 9% 3 7% 5% 5% 4 3 4 5% 35%	1570
March	1st to 10th	Day	25% 6% 2 5% 4 4 4 4 5% 7% 35%	3266
	11th to 20th	Day	10% 5% 2 6% 6% 5% 4 4 7% 7% 43%	3480
	21st to end	Day	21% 8% 2 6% 3 3 3 3 4 5% 43%	3941
April	1st to 10th	Day	15% 8% 3 6% 5% 5% 4 4 6% 7% 37%	2280
	11th to 20th	Day	16% 6% 2 6% 4 5% 4 4 5% 6% 42%	2254
	21st to end	Day	18% 5% 2 6% 5% 4 4 4 6% 7% 39%	2280
May	1st to 10th	Day	28% 6% 2 6% 3 4 4 3 5% 7% 31%	4115
	11th to 20th	Day	23% 9% 3 8% 5% 4 4 4 5% 7% 27%	4398
	21st to end	Day	13% 5% 2 5% 4 5% 5% 4 6% 10% 43%	4837
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 9% 39%	2660
	11th to 20th	Day	14% 5% 2 6% 5% 5% 5% 5% 7% 9% 38%	2660
	21st to end	Day	10% 4 2 5% 5% 5% 5% 5% 7% 11% 42%	2660
July	1st to 10th	Day	6% 5% 2 8% 6% 6% 6% 6% 8% 11% 36%	4440
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 4 8% 11% 40%	4440
	21st to end	Day	10% 8% 3 8% 6% 6% 6% 5% 6% 8% 35%	4574
August	1st to 10th	Day	19% 5% 2 6% 4 6% 5% 5% 7% 9% 32%	4104
	11th to 20th	Day	15% 5% 2 6% 3 4 5% 4 7% 9% 41%	3861
	21st to end	Day	14% 5% 2 5% 3 3 3 3 6% 9% 47%	4180
September	1st to 10th	Day	16% 6% 2 5% 3 3 3 3 4 6% 47%	2280
	11th to 20th	Day	13% 4 2 5% 3 3 4 3 5% 8% 50%	2280
	21st to end	Day	23% 7% 2 5% 3 4 4 3 5% 6% 38%	2021
October	1st to 10th	Day	18% 6% 2 4 3 3 4 3 6% 7% 44%	1900
	11th to 20th	Day	17% 5% 2 6% 3 3 4 3 4 7% 45%	1900
	21st to end	Day	17% 6% 2 5% 3 4 4 3 6% 8% 41%	2090
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 5% 8% 50%	1766
	11th to 20th	Day	17% 5% 1 4 4 4 5% 3 5% 7% 44%	1770
	21st to end	Day	17% 6% 2 6% 4 4 5% 3 6% 8% 40%	1598
December	1st to 10th	Day	19% 8% 2 7% 5% 5% 4 4 5% 6% 34%	1520
	11th to 20th	Day	20% 6% 2 6% 4 4 5% 3 5% 7% 37%	1906
	21st to end	Day	19% 7% 3 8% 5% 5% 5% 4 7% 6% 29%	2772
January	1st to 10th	Night	16% 7% 2 6% 4 4 5% 3 6% 8% 38%	4429
	11th to 20th	Night	18% 7% 3 7% 4 5% 5% 4 6% 6% 36%	4244
	21st to end	Night	23% 8% 3 8% 4 3 3 3 5% 6% 34%	4532
February	1st to 10th	Night	16% 9% 3 5% 4 4 5% 4 5% 7% 38%	2470
	11th to 20th	Night	16% 8% 3 7% 4 4 4 4 4 7% 39%	2337
	21st to end	Night	18% 8% 2 7% 5% 5% 4 3 5% 6% 38%	1884
March	1st to 10th	Night	22% 10% 2 6% 4 4 3 3 4 5% 37%	3569
	11th to 20th	Night	11% 7% 2 6% 4 4 4 4 5% 6% 47%	3479
	21st to end	Night	15% 9% 2 6% 4 4 4 2 4 5% 46%	3690
April	1st to 10th	Night	18% 8% 2 6% 5% 4 4 4 5% 8% 36%	1900
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 6% 8% 41%	1875
	21st to end	Night	20% 6% 2 5% 3 3 4 3 5% 6% 44%	1900
May	1st to 10th	Night	27% 7% 3 6% 4 4 4 4 5% 6% 31%	2852
	11th to 20th	Night	26% 9% 3 6% 4 4 4 3 5% 7% 28%	2495
	21st to end	Night	12% 6% 2 7% 4 4 5% 4 5% 9% 42%	2738
June	1st to 10th	Night	14% 5% 2 5% 4 4 5% 3 6% 8% 44%	1520
	11th to 20th	Night	12% 5% 2 6% 5% 4 4 4 6% 10% 42%	1520
	21st to end	Night	11% 4 2 5% 4 5% 6% 5% 6% 11% 42%	1520
July	1st to 10th	Night	7% 5% 3 8% 6% 5% 6% 5% 7% 9% 40%	2520
	11th to 20th	Night	8% 5% 2 6% 6% 6% 6% 5% 7% 10% 39%	2520
	21st to end	Night	14% 7% 3 6% 5% 5% 5% 4 6% 7% 38%	2976
August	1st to 10th	Night	20% 6% 2 6% 5% 4 4 4 6% 8% 34%	2825
	11th to 20th	Night	14% 7% 2 8% 4 4 4 3 5% 7% 40%	2934
	21st to end	Night	13% 5% 2 5% 4 4 4 4 6% 8% 46%	3476
September	1st to 10th	Night	15% 6% 2 6% 3 4 3 3 4 7% 48%	1900
	11th to 20th	Night	13% 4 1 5% 3 4 3 3 5% 7% 51%	1900
	21st to end	Night	22% 5% 2 6% 3 4 4 3 5% 6% 40%	2155
October	1st to 10th	Night	20% 7% 2 5% 3 3 3 3 4 6% 44%	2280
	11th to 20th	Night	17% 6% 2 5% 3 4 4 2 4 6% 47%	2280
	21st to end	Night	17% 6% 2 4 3 3 4 4 6% 7% 45%	2508
November	1st to 10th	Night	11% 5% 1 5% 4 3 4 3 5% 6% 53%	2532
	11th to 20th	Night	15% 8% 2 5% 4 4 4 3 5% 6% 44%	2628
	21st to end	Night	15% 6% 2 5% 5% 4 5% 4 5% 7% 43%	2798
December	1st to 10th	Night	18% 8% 2 6% 5% 4 5% 4 5% 7% 35%	2660
	11th to 20th	Night	18% 7% 2 6% 4 4 5% 4 6% 7% 38%	3288
	21st to end	Night	18% 8% 3 6% 6% 5% 5% 5% 6% 7% 31%	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	41% 7% 15% 25% 10% 2	2518
	11th to 20th	Day	52% 7% 11% 16% 11% 2	2713
	21st to end	Day	53% 8% 10% 20% 7% 1	3124
February	1st to 10th	Day	47% 7% 13% 21% 11% 1	1710
	11th to 20th	Day	44% 7% 10% 23% 13% 2	1737
	21st to end	Day	50% 5% 10% 21% 10% 4	1570
March	1st to 10th	Day	46% 6% 12% 25% 8% 2	3269
	11th to 20th	Day	35% 8% 13% 26% 14% 4	3480
	21st to end	Day	45% 5% 9% 21% 18% 2	3941
April	1st to 10th	Day	44% 7% 12% 19% 14% 5%	2280
	11th to 20th	Day	40% 7% 11% 22% 15% 4	2254
	21st to end	Day	42% 7% 10% 21% 16% 4	2280
May	1st to 10th	Day	52% 8% 9% 20% 10% 2	4127
	11th to 20th	Day	53% 9% 13% 16% 7% 1	4402
	21st to end	Day	34% 9% 13% 26% 16% 2	4837
June	1st to 10th	Day	39% 9% 13% 23% 15% 1	2660
	11th to 20th	Day	39% 9% 14% 23% 11% 3	2660
	21st to end	Day	34% 9% 15% 26% 15% 1	2660
July	1st to 10th	Day	39% 9% 14% 22% 13% 2	4370
	11th to 20th	Day	36% 8% 15% 26% 14% 1	4365
	21st to end	Day	45% 7% 11% 18% 18% 2	4428
August	1st to 10th	Day	47% 8% 13% 23% 9%	4091
	11th to 20th	Day	38% 7% 11% 28% 15% 1	3900
	21st to end	Day	34% 6% 11% 28% 20% 2	4180
September	1st to 10th	Day	38% 6% 11% 20% 20% 4	2280
	11th to 20th	Day	33% 5% 11% 25% 22% 4	2280
	21st to end	Day	47% 5% 9% 17% 19% 2	2021
October	1st to 10th	Day	36% 5% 9% 21% 25% 4	3160
	11th to 20th	Day	28% 5% 12% 28% 21% 6%	3140
	21st to end	Day	27% 4 13% 28% 26% 3	3428
November	1st to 10th	Day	34% 4 14% 24% 20% 4	1766
	11th to 20th	Day	38% 5% 12% 24% 18% 3	1770
	21st to end	Day	41% 5% 14% 29% 9% 2	1598
December	1st to 10th	Day	49% 8% 15% 18% 11% 1	1520
	11th to 20th	Day	44% 7% 15% 26% 8% 1	1906
	21st to end	Day	49% 8% 16% 18% 8% 1	2772
January	1st to 10th	Night	42% 6% 15% 24% 10% 3	4429
	11th to 20th	Night	44% 8% 15% 22% 10% 2	4244
	21st to end	Night	50% 6% 11% 24% 8% 1	4532
February	1st to 10th	Night	45% 5% 14% 24% 10% 1	2470
	11th to 20th	Night	45% 5% 10% 20% 17% 2	2339
	21st to end	Night	46% 6% 11% 20% 14% 3	1884
March	1st to 10th	Night	48% 7% 10% 23% 12% 1	3579
	11th to 20th	Night	34% 8% 13% 29% 14% 2	3480
	21st to end	Night	41% 5% 8% 20% 22% 4	3690
April	1st to 10th	Night	45% 5% 10% 20% 15% 3	1900
	11th to 20th	Night	40% 7% 11% 20% 19% 3	1875
	21st to end	Night	40% 6% 11% 21% 16% 5%	1900
May	1st to 10th	Night	52% 8% 8% 18% 11% 2	2859
	11th to 20th	Night	53% 10% 12% 13% 10% 1	2496
	21st to end	Night	37% 10% 12% 23% 13% 4	2739
June	1st to 10th	Night	37% 8% 11% 23% 19% 2	1520
	11th to 20th	Night	36% 10% 13% 24% 15% 2	1520
	21st to end	Night	34% 9% 15% 26% 15% 2	1520
July	1st to 10th	Night	39% 9% 16% 17% 15% 5%	2480
	11th to 20th	Night	38% 9% 14% 24% 14% 1	2472
	21st to end	Night	42% 8% 13% 17% 19% 1	2881
August	1st to 10th	Night	46% 7% 17% 21% 9% 1	2814
	11th to 20th	Night	42% 6% 11% 24% 16% 1	2961
	21st to end	Night	34% 7% 11% 29% 18% 2	3476
September	1st to 10th	Night	37% 6% 12% 21% 20% 4	1900
	11th to 20th	Night	32% 5% 10% 25% 24% 4	1900
	21st to end	Night	45% 5% 9% 18% 20% 3	2155
October	1st to 10th	Night	43% 4 10% 21% 21% 2	3800
	11th to 20th	Night	28% 4 10% 28% 24% 5%	3779
	21st to end	Night	26% 4 12% 31% 24% 2	4120
November	1st to 10th	Night	32% 5% 12% 26% 20% 4	2532
	11th to 20th	Night	40% 4 10% 24% 17% 4	2628
	21st to end	Night	40% 6% 12% 27% 14% 1	2798
December	1st to 10th	Night	47% 7% 13% 21% 12%	2660
	11th to 20th	Night	43% 6% 13% 22% 13% 2	3288
	21st to end	Night	46% 10% 15% 21% 8%	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	28% 28% 27% 14% 3	180
	11th to 20th	Day	31% 27% 30% 11% 1	235
	21st to end	Day	24% 29% 30% 13% 3 1	297
February	1st to 10th	Day	25% 27% 32% 13% 3	270
	11th to 20th	Day	29% 26% 35% 10%	335
	21st to end	Day	31% 20% 30% 17% 2	382
March	1st to 10th	Day	24% 23% 32% 16% 5%	460
	11th to 20th	Day	23% 29% 30% 13% 4 1	460
	21st to end	Day	26% 23% 31% 14% 5% 1	506
April	1st to 10th	Day	25% 23% 29% 15% 7% 1	460
	11th to 20th	Day	23% 23% 25% 18% 8% 3	452
	21st to end	Day	25% 17% 34% 15% 7% 2	460
May	1st to 10th	Day	26% 18% 29% 18% 6% 3	463
	11th to 20th	Day	22% 17% 30% 19% 9% 3	487
	21st to end	Day	18% 9% 26% 25% 18% 5%	529
June	1st to 10th	Day	15% 15% 29% 21% 15% 4	490
	11th to 20th	Day	17% 12% 27% 27% 14% 3	490
	21st to end	Day	12% 11% 32% 28% 14% 3	490
July	1st to 10th	Day	13% 6% 22% 30% 21% 8%	485
	11th to 20th	Day	8% 5% 24% 35% 23% 6%	484
	21st to end	Day	11% 7% 30% 30% 18% 4	532
August	1st to 10th	Day	13% 5% 23% 30% 20% 9%	486
	11th to 20th	Day	15% 6% 21% 30% 20% 8%	479
	21st to end	Day	12% 6% 24% 31% 16% 11%	539
September	1st to 10th	Day	19% 10% 19% 23% 21% 8%	490
	11th to 20th	Day	13% 4 23% 29% 21% 9%	490
	21st to end	Day	28% 12% 22% 21% 14% 4	490
October	1st to 10th	Day	23% 7% 27% 23% 17% 5%	490
	11th to 20th	Day	19% 17% 26% 24% 12% 2	490
	21st to end	Day	20% 16% 31% 22% 9% 2	539
November	1st to 10th	Day	17% 15% 28% 25% 12% 2	398
	11th to 20th	Day	21% 19% 32% 21% 7%	370
	21st to end	Day	25% 22% 33% 15% 5% 1	200
December	1st to 10th	Day	24% 28% 32% 9% 5% 1	180
	11th to 20th	Day	28% 24% 28% 16% 3 1	180
	21st to end	Day	25% 23% 29% 16% 5% 1	198
January	1st to 10th	Night	19% 21% 39% 18% 3	760
	11th to 20th	Night	24% 19% 31% 23% 4	760
	21st to end	Night	19% 20% 37% 22% 2	836
February	1st to 10th	Night	21% 20% 32% 25% 2	760
	11th to 20th	Night	21% 25% 36% 16% 1	743
	21st to end	Night	24% 21% 34% 17% 3	628
March	1st to 10th	Night	21% 20% 33% 23% 4	760
	11th to 20th	Night	23% 20% 32% 19% 5% 1	760
	21st to end	Night	22% 14% 38% 20% 5%	836
April	1st to 10th	Night	23% 20% 33% 19% 5%	760
	11th to 20th	Night	18% 15% 35% 24% 7%	751
	21st to end	Night	22% 13% 32% 25% 8%	760
May	1st to 10th	Night	24% 11% 26% 30% 10%	589
	11th to 20th	Night	21% 8% 33% 29% 9%	374
	21st to end	Night	15% 5% 25% 37% 17% 1	411
June	1st to 10th	Night	15% 6% 26% 33% 20%	380
	11th to 20th	Night	14% 6% 28% 38% 14%	380
	21st to end	Night	11% 3 26% 46% 14% 1	380
July	1st to 10th	Night	11% 4 22% 41% 21% 2	370
	11th to 20th	Night	9% 2 17% 42% 28% 2	368
	21st to end	Night	11% 3 20% 40% 24% 1	552
August	1st to 10th	Night	14% 2 13% 42% 27% 2	567
	11th to 20th	Night	13% 5% 14% 36% 28% 3	648
	21st to end	Night	14% 3 18% 35% 28% 2	836
September	1st to 10th	Night	16% 4 23% 33% 22% 3	760
	11th to 20th	Night	13% 5% 19% 34% 25% 4	760
	21st to end	Night	23% 6% 20% 29% 20% 2	760
October	1st to 10th	Night	23% 7% 22% 27% 18% 3	760
	11th to 20th	Night	19% 10% 28% 31% 12% 1	760
	21st to end	Night	21% 13% 26% 30% 11%	836
November	1st to 10th	Night	13% 11% 33% 31% 11% 1	780
	11th to 20th	Night	18% 18% 28% 27% 7% 1	800
	21st to end	Night	17% 18% 33% 25% 6%	800
December	1st to 10th	Night	24% 17% 31% 21% 6%	760
	11th to 20th	Night	19% 17% 35% 25% 4	760
	21st to end	Night	21% 17% 30% 29% 2	836

Page generated at 2024-11-27 17:30:52. Version ac07

Copyright © 2024 Attilla Danko.