Whippoorwill Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whippoorwill Hill Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	17% 10% 3 8% 5% 5% 4 3 5% 7% 33%	101817
	Night	18% 11% 3 8% 5% 4 4 3 5% 6% 32%	97824
Transparency	Day	51% 3 12% 23% 11% 1	105326
	Night	53% 3 11% 21% 10% 1	102404
Seeing	Day	24% 13% 31% 20% 9% 3	14565
	Night	24% 12% 29% 25% 9% 1	23729

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% 18% 5% 10% 5% 6% 4 3 4 4 26%	2517
	11th to 20th	Day	14% 15% 6% 14% 7% 5% 4 3 4 4 23%	2520
	21st to end	Day	18% 18% 5% 14% 7% 6% 4 3 4 4 18%	2968
February	1st to 10th	Day	17% 14% 4 12% 8% 4 5% 4 5% 5% 23%	1710
	11th to 20th	Day	12% 15% 5% 11% 6% 5% 4 3 4 6% 29%	1663
	21st to end	Day	20% 15% 5% 9% 5% 6% 4 4 4 5% 23%	1564
March	1st to 10th	Day	21% 14% 4 9% 6% 4 4 3 4 4 28%	3170
	11th to 20th	Day	12% 16% 4 8% 5% 6% 4 3 4 6% 31%	3480
	21st to end	Day	13% 9% 3 7% 5% 4 3 3 4 5% 42%	3995
April	1st to 10th	Day	21% 13% 3 6% 4 4 3 3 4 5% 33%	2280
	11th to 20th	Day	21% 10% 2 6% 4 3 3 3 5% 5% 37%	2254
	21st to end	Day	22% 9% 3 8% 4 4 3 4 5% 5% 32%	2383
May	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 5% 7% 33%	4426
	11th to 20th	Day	17% 8% 3 8% 5% 4 4 3 5% 8% 34%	4398
	21st to end	Day	14% 6% 2 6% 4 5% 5% 3 6% 9% 40%	4837
June	1st to 10th	Day	21% 8% 2 7% 6% 4 5% 4 5% 7% 31%	2660
	11th to 20th	Day	16% 5% 2 6% 5% 5% 5% 4 7% 8% 38%	2660
	21st to end	Day	17% 8% 3 7% 5% 5% 4 5% 5% 7% 33%	2660
July	1st to 10th	Day	12% 5% 3 7% 5% 5% 6% 5% 6% 10% 37%	4440
	11th to 20th	Day	13% 5% 2 5% 4 5% 5% 4 6% 10% 40%	4440
	21st to end	Day	11% 5% 2 6% 4 4 6% 4 7% 9% 41%	4814
August	1st to 10th	Day	17% 8% 3 7% 5% 4 4 3 6% 6% 37%	4267
	11th to 20th	Day	17% 7% 3 5% 4 4 4 4 6% 9% 38%	4012
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 6% 9% 39%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 5% 5% 3 5% 7% 42%	2280
	11th to 20th	Day	13% 4 2 6% 4 4 4 4 5% 7% 47%	2280
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 6% 40%	2019
October	1st to 10th	Day	21% 8% 2 7% 5% 4 3 3 5% 6% 37%	1900
	11th to 20th	Day	21% 10% 3 7% 5% 5% 5% 3 5% 7% 30%	1900
	21st to end	Day	25% 11% 2 8% 4 4 5% 4 4 5% 27%	1971
November	1st to 10th	Day	14% 10% 3 8% 5% 5% 5% 4 5% 7% 34%	1761
	11th to 20th	Day	17% 12% 3 10% 4 5% 4 3 4 6% 31%	1602
	21st to end	Day	20% 15% 5% 9% 6% 5% 5% 3 5% 5% 22%	1600
December	1st to 10th	Day	23% 17% 5% 9% 5% 4 5% 3 6% 4 18%	1528
	11th to 20th	Day	21% 15% 5% 10% 5% 4 4 3 4 4 25%	1906
	21st to end	Day	26% 17% 6% 11% 5% 3 3 2 3 3 21%	2772
January	1st to 10th	Night	18% 14% 7% 12% 6% 5% 4 3 5% 5% 21%	4429
	11th to 20th	Night	14% 15% 6% 14% 7% 5% 6% 4 4 5% 21%	4440
	21st to end	Night	19% 17% 6% 11% 6% 6% 4 2 4 4 20%	4685
February	1st to 10th	Night	15% 16% 5% 10% 6% 6% 5% 4 6% 6% 22%	2470
	11th to 20th	Night	13% 15% 5% 10% 7% 5% 4 3 4 5% 29%	2403
	21st to end	Night	15% 15% 4 9% 5% 5% 4 3 5% 5% 29%	1889
March	1st to 10th	Night	21% 12% 3 8% 5% 4 3 3 4 4 32%	3668
	11th to 20th	Night	19% 16% 4 8% 4 4 4 3 5% 6% 27%	3479
	21st to end	Night	16% 11% 3 7% 3 3 3 3 4 5% 41%	3636
April	1st to 10th	Night	21% 10% 3 7% 5% 4 3 3 4 5% 34%	1900
	11th to 20th	Night	21% 9% 2 6% 4 4 4 3 4 5% 37%	1875
	21st to end	Night	20% 10% 3 7% 5% 3 4 3 4 6% 33%	1810
May	1st to 10th	Night	22% 10% 3 7% 4 4 5% 4 5% 6% 30%	2514
	11th to 20th	Night	20% 9% 2 7% 4 4 4 3 5% 5% 38%	2495
	21st to end	Night	14% 6% 2 6% 3 4 4 4 6% 8% 42%	2738
June	1st to 10th	Night	16% 7% 3 7% 5% 5% 5% 4 7% 7% 34%	1520
	11th to 20th	Night	14% 7% 2 5% 4 4 5% 3 6% 7% 42%	1520
	21st to end	Night	17% 7% 2 7% 4 5% 5% 5% 6% 8% 35%	1520
July	1st to 10th	Night	11% 6% 3 8% 5% 5% 6% 5% 6% 8% 37%	2520
	11th to 20th	Night	14% 6% 2 6% 3 4 5% 3 6% 7% 44%	2520
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 6% 7% 45%	2739
August	1st to 10th	Night	11% 7% 2 7% 4 4 4 3 6% 7% 43%	2659
	11th to 20th	Night	12% 7% 2 8% 5% 4 4 4 6% 7% 42%	2785
	21st to end	Night	11% 5% 2 7% 4 5% 5% 4 6% 9% 43%	3476
September	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	13% 4 1 5% 3 3 4 4 5% 6% 52%	1900
	21st to end	Night	17% 6% 2 6% 4 4 4 3 5% 7% 43%	2157
October	1st to 10th	Night	17% 8% 3 6% 4 4 4 4 5% 7% 36%	2280
	11th to 20th	Night	22% 9% 3 7% 5% 4 4 4 5% 6% 32%	2280
	21st to end	Night	24% 9% 3 7% 5% 4 4 4 5% 6% 28%	2627
November	1st to 10th	Night	18% 11% 3 6% 4 3 5% 4 4 6% 36%	2537
	11th to 20th	Night	17% 11% 4 8% 4 4 4 4 4 6% 33%	2795
	21st to end	Night	21% 13% 4 9% 6% 4 5% 3 5% 6% 24%	2800
December	1st to 10th	Night	20% 19% 5% 11% 5% 5% 4 3 4 5% 20%	2686
	11th to 20th	Night	22% 15% 4 9% 5% 4 4 3 3 4 27%	3288
	21st to end	Night	30% 16% 4 11% 5% 4 3 3 4 4 16%	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	63% 2 15% 13% 6% 2	2518
	11th to 20th	Day	68% 1 10% 12% 8%	2520
	21st to end	Day	73% 3 9% 10% 5% 1	2968
February	1st to 10th	Day	63% 3 8% 20% 5% 1	1710
	11th to 20th	Day	59% 2 10% 18% 10% 1	1672
	21st to end	Day	65% 2 9% 12% 10% 1	1564
March	1st to 10th	Day	61% 2 8% 19% 9% 1	3173
	11th to 20th	Day	56% 3 12% 15% 12% 2	3480
	21st to end	Day	45% 3 6% 25% 18% 4	3995
April	1st to 10th	Day	55% 3 6% 20% 13% 3	2280
	11th to 20th	Day	51% 3 5% 22% 17% 2	2254
	21st to end	Day	54% 3 8% 17% 14% 4	2383
May	1st to 10th	Day	53% 3 9% 22% 11% 2	4440
	11th to 20th	Day	51% 2 13% 23% 9% 1	4402
	21st to end	Day	42% 3 13% 26% 15% 2	4837
June	1st to 10th	Day	53% 4 9% 20% 12% 1	2660
	11th to 20th	Day	43% 4 10% 27% 13% 2	2660
	21st to end	Day	50% 4 13% 21% 11% 1	2660
July	1st to 10th	Day	41% 5% 13% 28% 12% 1	4370
	11th to 20th	Day	38% 5% 15% 33% 9%	4365
	21st to end	Day	39% 5% 13% 32% 11%	4661
August	1st to 10th	Day	47% 3 14% 24% 11% 1	4253
	11th to 20th	Day	43% 4 14% 28% 11% 1	4051
	21st to end	Day	41% 3 15% 29% 11%	4180
September	1st to 10th	Day	41% 4 14% 29% 13% 1	2280
	11th to 20th	Day	36% 4 13% 31% 16%	2280
	21st to end	Day	45% 4 13% 26% 12%	2019
October	1st to 10th	Day	45% 3 12% 32% 8%	3160
	11th to 20th	Day	46% 3 15% 26% 10%	3140
	21st to end	Day	49% 4 15% 25% 7%	3222
November	1st to 10th	Day	50% 3 14% 23% 9%	1761
	11th to 20th	Day	55% 3 11% 18% 11% 1	1602
	21st to end	Day	65% 4 13% 11% 8%	1600
December	1st to 10th	Day	69% 3 12% 11% 4 1	1528
	11th to 20th	Day	65% 4 14% 13% 5%	1906
	21st to end	Day	73% 2 7% 14% 4	2772
January	1st to 10th	Night	66% 2 15% 12% 4	4429
	11th to 20th	Night	69% 2 11% 12% 5%	4440
	21st to end	Night	71% 2 10% 11% 6% 1	4685
February	1st to 10th	Night	63% 3 10% 17% 7% 1	2470
	11th to 20th	Night	58% 3 9% 20% 9%	2405
	21st to end	Night	58% 4 9% 18% 11% 1	1889
March	1st to 10th	Night	57% 2 8% 23% 10% 1	3678
	11th to 20th	Night	60% 2 13% 15% 9% 1	3480
	21st to end	Night	47% 3 5% 25% 17% 3	3636
April	1st to 10th	Night	53% 2 7% 21% 15% 2	1900
	11th to 20th	Night	51% 3 7% 20% 17% 2	1875
	21st to end	Night	53% 3 8% 17% 16% 3	1810
May	1st to 10th	Night	56% 2 9% 20% 10% 3	2520
	11th to 20th	Night	49% 3 11% 25% 10% 2	2496
	21st to end	Night	41% 3 13% 23% 18% 2	2739
June	1st to 10th	Night	48% 5% 11% 23% 12% 1	1520
	11th to 20th	Night	41% 3 12% 23% 18% 2	1520
	21st to end	Night	46% 6% 13% 21% 13% 1	1520
July	1st to 10th	Night	43% 5% 13% 22% 15% 2	2480
	11th to 20th	Night	38% 4 12% 35% 10%	2472
	21st to end	Night	38% 6% 14% 26% 14% 2	2651
August	1st to 10th	Night	40% 4 14% 27% 13% 1	2649
	11th to 20th	Night	41% 4 14% 32% 9% 1	2812
	21st to end	Night	38% 5% 15% 29% 11% 1	3476
September	1st to 10th	Night	38% 4 12% 30% 15% 1	1900
	11th to 20th	Night	33% 4 14% 34% 14% 1	1900
	21st to end	Night	42% 3 11% 31% 12% 1	2157
October	1st to 10th	Night	42% 3 12% 29% 14%	3800
	11th to 20th	Night	45% 3 15% 27% 10%	3779
	21st to end	Night	49% 4 14% 25% 8%	4326
November	1st to 10th	Night	50% 3 13% 22% 11% 1	2537
	11th to 20th	Night	53% 3 11% 20% 12% 2	2795
	21st to end	Night	62% 3 12% 17% 6%	2800
December	1st to 10th	Night	68% 3 9% 15% 4	2686
	11th to 20th	Night	62% 3 10% 16% 8% 1	3288
	21st to end	Night	73% 2 9% 13% 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	29% 17% 36% 13% 4 1	180
	11th to 20th	Day	36% 13% 32% 16% 2 1	180
	21st to end	Day	24% 18% 34% 18% 6%	254
February	1st to 10th	Day	35% 20% 33% 11% 1	270
	11th to 20th	Day	30% 24% 39% 7% 1	270
	21st to end	Day	36% 16% 35% 11% 2	376
March	1st to 10th	Day	28% 19% 32% 17% 5%	460
	11th to 20th	Day	31% 15% 33% 15% 5%	460
	21st to end	Day	32% 19% 29% 12% 7% 1	506
April	1st to 10th	Day	32% 19% 28% 14% 7%	460
	11th to 20th	Day	35% 17% 23% 14% 8% 3	452
	21st to end	Day	30% 16% 34% 13% 5% 2	460
May	1st to 10th	Day	26% 14% 31% 21% 7% 2	463
	11th to 20th	Day	20% 13% 35% 21% 9% 2	487
	21st to end	Day	19% 13% 32% 23% 11% 2	529
June	1st to 10th	Day	24% 10% 32% 23% 8% 2	490
	11th to 20th	Day	19% 13% 30% 23% 12% 3	490
	21st to end	Day	22% 11% 30% 23% 11% 3	490
July	1st to 10th	Day	15% 6% 29% 32% 14% 4	485
	11th to 20th	Day	17% 7% 32% 26% 14% 4	484
	21st to end	Day	14% 8% 32% 30% 13% 4	532
August	1st to 10th	Day	17% 6% 29% 31% 14% 4	486
	11th to 20th	Day	14% 6% 28% 30% 16% 7%	479
	21st to end	Day	17% 9% 31% 26% 12% 6%	539
September	1st to 10th	Day	16% 11% 30% 24% 12% 7%	490
	11th to 20th	Day	13% 8% 24% 25% 19% 11%	490
	21st to end	Day	21% 9% 27% 24% 14% 4	490
October	1st to 10th	Day	27% 14% 27% 18% 11% 4	490
	11th to 20th	Day	30% 16% 29% 17% 6% 2	490
	21st to end	Day	30% 18% 28% 19% 4	476
November	1st to 10th	Day	26% 17% 29% 21% 8%	395
	11th to 20th	Day	28% 15% 36% 12% 6% 2	202
	21st to end	Day	30% 22% 33% 13% 3	200
December	1st to 10th	Day	32% 16% 35% 13% 4	182
	11th to 20th	Day	36% 21% 31% 9% 4 1	180
	21st to end	Day	38% 14% 32% 12% 3 1	198
January	1st to 10th	Night	30% 17% 30% 20% 3	760
	11th to 20th	Night	31% 15% 30% 20% 4 1	760
	21st to end	Night	22% 14% 33% 25% 6%	836
February	1st to 10th	Night	24% 19% 34% 20% 2	760
	11th to 20th	Night	23% 18% 38% 18% 3	743
	21st to end	Night	25% 17% 35% 19% 4	628
March	1st to 10th	Night	27% 15% 31% 24% 4	760
	11th to 20th	Night	28% 19% 28% 21% 4	760
	21st to end	Night	25% 14% 31% 21% 8%	836
April	1st to 10th	Night	29% 13% 33% 22% 3	760
	11th to 20th	Night	27% 18% 28% 19% 7% 1	751
	21st to end	Night	26% 12% 29% 24% 8% 1	670
May	1st to 10th	Night	25% 8% 26% 29% 11% 2	380
	11th to 20th	Night	16% 10% 33% 32% 9% 1	374
	21st to end	Night	12% 11% 38% 27% 12%	411
June	1st to 10th	Night	16% 7% 30% 37% 10% 1	380
	11th to 20th	Night	16% 8% 29% 31% 14% 1	380
	21st to end	Night	19% 5% 25% 37% 14% 1	380
July	1st to 10th	Night	12% 5% 31% 35% 16% 1	370
	11th to 20th	Night	15% 3 27% 38% 16% 1	368
	21st to end	Night	10% 4 29% 41% 14% 1	416
August	1st to 10th	Night	14% 4 24% 36% 20% 1	466
	11th to 20th	Night	14% 3 22% 35% 24% 2	564
	21st to end	Night	13% 6% 29% 33% 17% 2	836
September	1st to 10th	Night	15% 6% 30% 31% 17% 1	760
	11th to 20th	Night	16% 6% 20% 29% 23% 6%	760
	21st to end	Night	20% 8% 25% 25% 19% 2	760
October	1st to 10th	Night	23% 11% 27% 23% 15% 3	760
	11th to 20th	Night	27% 11% 30% 24% 8% 1	760
	21st to end	Night	30% 13% 27% 25% 6%	836
November	1st to 10th	Night	28% 13% 29% 21% 8% 1	780
	11th to 20th	Night	27% 16% 31% 17% 9% 1	800
	21st to end	Night	31% 16% 27% 19% 6%	800
December	1st to 10th	Night	30% 16% 32% 18% 4	768
	11th to 20th	Night	28% 18% 32% 18% 3 1	760
	21st to end	Night	35% 15% 29% 19% 2	836

Page generated at 2024-11-29 10:43:07. Version ac07

Copyright © 2024 Attilla Danko.