Country Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Country Hill Observatory clear sky chart from 2005-11-06 to 2026-02-16.

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% 8% 2 6% 4 4 4 4 5% 7% 39%	130359
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 40%	130457
Transparency	Day	45% 4 11% 22% 16% 3	133892
	Night	45% 4 10% 22% 16% 3	134998
Seeing	Day	26% 16% 32% 17% 7% 2	16641
	Night	24% 15% 32% 23% 6%	25673

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	10% 8% 4 7% 4 4 4 4 5% 6% 44%	4661
	11th to 20th	Day	15% 9% 3 5% 3 4 3 3 4 5% 46%	4650
	21st to end	Day	15% 9% 2 5% 3 3 3 3 4 6% 46%	5124
February	1st to 10th	Day	18% 8% 2 5% 5% 5% 4 4 6% 6% 37%	1991
	11th to 20th	Day	14% 7% 3 6% 5% 4 4 3 5% 7% 42%	1998
	21st to end	Day	18% 10% 3 6% 4 3 4 3 4 6% 38%	1650
March	1st to 10th	Day	22% 11% 2 6% 4 3 3 3 5% 5% 37%	4476
	11th to 20th	Day	15% 9% 2 6% 4 4 4 4 5% 7% 41%	4768
	21st to end	Day	25% 10% 2 5% 4 4 4 4 5% 6% 32%	5779
April	1st to 10th	Day	20% 9% 3 7% 4 3 3 4 5% 7% 37%	2400
	11th to 20th	Day	18% 7% 2 5% 4 4 4 3 6% 7% 40%	2375
	21st to end	Day	21% 6% 2 7% 4 4 4 3 5% 5% 39%	2600
May	1st to 10th	Day	29% 10% 3 6% 3 4 4 3 4 7% 25%	5886
	11th to 20th	Day	21% 9% 3 7% 5% 5% 4 3 5% 6% 32%	5906
	21st to end	Day	20% 7% 3 6% 4 4 4 4 5% 8% 35%	6949
June	1st to 10th	Day	18% 7% 2 5% 5% 4 5% 4 6% 9% 34%	2800
	11th to 20th	Day	16% 6% 2 7% 4 5% 5% 4 5% 9% 36%	2800
	21st to end	Day	16% 7% 2 6% 5% 4 4 4 7% 9% 37%	2800
July	1st to 10th	Day	17% 7% 2 7% 5% 5% 5% 5% 7% 9% 32%	6360
	11th to 20th	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 11% 34%	6360
	21st to end	Day	16% 7% 2 6% 4 4 4 4 6% 7% 41%	6926
August	1st to 10th	Day	16% 8% 3 8% 5% 5% 5% 4 6% 8% 32%	4252
	11th to 20th	Day	12% 6% 3 7% 5% 6% 6% 4 5% 7% 39%	4086
	21st to end	Day	8% 4 2 6% 4 5% 6% 5% 7% 9% 45%	4312
September	1st to 10th	Day	14% 6% 2 6% 4 3 5% 4 5% 6% 45%	2395
	11th to 20th	Day	14% 5% 2 5% 3 4 3 3 4 5% 51%	2200
	21st to end	Day	19% 6% 2 5% 4 4 3 4 5% 5% 42%	2200
October	1st to 10th	Day	22% 7% 2 5% 3 3 3 2 4 5% 44%	2200
	11th to 20th	Day	16% 4 2 6% 3 3 3 3 5% 7% 47%	1966
	21st to end	Day	18% 6% 2 6% 4 3 4 4 4 5% 44%	1980
November	1st to 10th	Day	16% 6% 2 5% 4 3 4 3 3 5% 49%	1851
	11th to 20th	Day	18% 6% 2 4 4 3 3 3 4 6% 47%	1890
	21st to end	Day	18% 7% 2 5% 4 3 3 3 5% 6% 44%	1890
December	1st to 10th	Day	15% 9% 2 4 4 3 3 3 4 6% 48%	2764
	11th to 20th	Day	19% 6% 2 4 4 3 3 2 4 4 49%	3066
	21st to end	Day	20% 10% 3 7% 3 3 3 2 4 5% 38%	4048
January	1st to 10th	Night	15% 7% 2 5% 3 3 4 3 4 6% 48%	8234
	11th to 20th	Night	15% 10% 4 8% 4 4 3 3 4 5% 40%	8235
	21st to end	Night	15% 9% 3 7% 4 4 4 3 4 5% 41%	9057
February	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 5% 6% 40%	2622
	11th to 20th	Night	16% 8% 2 6% 4 4 5% 4 5% 6% 41%	2399
	21st to end	Night	17% 10% 2 7% 4 3 4 3 4 5% 41%	1980
March	1st to 10th	Night	23% 9% 2 5% 3 3 4 3 5% 6% 38%	5364
	11th to 20th	Night	16% 10% 3 6% 4 4 4 3 5% 6% 39%	5191
	21st to end	Night	25% 10% 2 6% 3 3 4 3 5% 5% 34%	5150
April	1st to 10th	Night	19% 9% 3 7% 4 5% 4 4 4 6% 36%	2000
	11th to 20th	Night	19% 8% 2 6% 5% 4 4 3 5% 5% 38%	1972
	21st to end	Night	20% 8% 2 6% 4 3 3 3 4 6% 40%	1800
May	1st to 10th	Night	29% 9% 3 7% 4 4 4 3 4 7% 26%	4054
	11th to 20th	Night	19% 9% 3 8% 5% 6% 5% 4 6% 7% 27%	4015
	21st to end	Night	20% 8% 3 7% 5% 5% 5% 4 6% 7% 32%	3926
June	1st to 10th	Night	15% 8% 3 6% 6% 4 5% 5% 6% 7% 37%	1600
	11th to 20th	Night	19% 7% 3 6% 4 3 5% 4 5% 8% 36%	1600
	21st to end	Night	15% 6% 3 6% 4 4 5% 4 6% 8% 41%	1600
July	1st to 10th	Night	16% 8% 3 6% 4 4 4 4 6% 10% 35%	3600
	11th to 20th	Night	15% 7% 3 7% 4 5% 4 4 6% 9% 36%	3600
	21st to end	Night	13% 8% 3 6% 5% 4 4 4 6% 6% 41%	3926
August	1st to 10th	Night	21% 7% 3 8% 4 5% 5% 4 6% 7% 30%	2850
	11th to 20th	Night	10% 8% 3 8% 5% 6% 7% 5% 6% 7% 36%	2958
	21st to end	Night	9% 4 1 5% 3 3 4 3 5% 7% 55%	3586
September	1st to 10th	Night	12% 7% 2 7% 4 5% 5% 4 5% 6% 44%	2005
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 4 6% 52%	2200
	21st to end	Night	19% 8% 2 6% 4 3 4 3 5% 5% 41%	2200
October	1st to 10th	Night	19% 8% 2 5% 4 3 3 3 4 6% 44%	2200
	11th to 20th	Night	16% 5% 2 4 4 3 4 3 5% 7% 47%	2430
	21st to end	Night	20% 7% 2 7% 4 4 4 2 4 5% 40%	2860
November	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 6% 48%	2667
	11th to 20th	Night	18% 6% 2 5% 3 3 3 2 4 6% 47%	2730
	21st to end	Night	16% 6% 2 4 3 4 4 4 5% 7% 45%	2730
December	1st to 10th	Night	18% 9% 1 5% 4 3 3 3 3 5% 46%	4618
	11th to 20th	Night	22% 8% 2 5% 3 3 3 3 4 5% 42%	5348
	21st to end	Night	17% 11% 3 6% 4 3 3 3 4 5% 40%	7150

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% 3 9% 25% 19% 3	4662
	11th to 20th	Day	42% 2 9% 21% 18% 8%	4680
	21st to end	Day	41% 2 10% 24% 22% 2	5124
February	1st to 10th	Day	48% 3 12% 19% 15% 3	1991
	11th to 20th	Day	43% 4 10% 23% 16% 3	2007
	21st to end	Day	48% 3 9% 21% 16% 3	1650
March	1st to 10th	Day	50% 3 10% 15% 12% 11%	4479
	11th to 20th	Day	44% 4 10% 29% 11% 2	4768
	21st to end	Day	55% 3 5% 15% 15% 7%	5779
April	1st to 10th	Day	49% 3 9% 19% 17% 4	2400
	11th to 20th	Day	43% 4 9% 22% 18% 3	2375
	21st to end	Day	47% 3 8% 21% 17% 4	2600
May	1st to 10th	Day	60% 4 13% 14% 8% 1	5897
	11th to 20th	Day	53% 4 13% 16% 11% 2	5910
	21st to end	Day	48% 5% 10% 23% 13% 1	6949
June	1st to 10th	Day	47% 5% 12% 23% 13% 1	2800
	11th to 20th	Day	46% 4 11% 22% 15% 2	2800
	21st to end	Day	44% 5% 13% 22% 15% 1	2800
July	1st to 10th	Day	47% 7% 11% 21% 13% 2	6290
	11th to 20th	Day	42% 7% 16% 24% 11% 1	6285
	21st to end	Day	42% 4 10% 26% 16% 2	6728
August	1st to 10th	Day	50% 6% 14% 21% 9% 1	4238
	11th to 20th	Day	44% 5% 13% 28% 10% 1	4125
	21st to end	Day	32% 6% 13% 28% 19% 2	4312
September	1st to 10th	Day	39% 5% 9% 24% 21% 2	2395
	11th to 20th	Day	35% 4 9% 25% 25% 3	2200
	21st to end	Day	44% 3 7% 21% 23% 2	2200
October	1st to 10th	Day	40% 4 8% 24% 21% 4	3590
	11th to 20th	Day	33% 2 6% 28% 28% 4	3169
	21st to end	Day	33% 2 12% 29% 21% 3	3180
November	1st to 10th	Day	39% 3 12% 23% 20% 2	1851
	11th to 20th	Day	39% 3 8% 24% 22% 4	1890
	21st to end	Day	43% 3 10% 28% 13% 3	1890
December	1st to 10th	Day	40% 3 14% 28% 15% 1	2764
	11th to 20th	Day	40% 3 13% 18% 19% 7%	3066
	21st to end	Day	50% 3 8% 21% 14% 4	4048
January	1st to 10th	Night	38% 2 10% 31% 17% 2	8234
	11th to 20th	Night	48% 2 10% 19% 15% 5%	8280
	21st to end	Night	47% 2 8% 19% 21% 4	9057
February	1st to 10th	Night	45% 4 11% 22% 15% 2	2622
	11th to 20th	Night	46% 4 8% 21% 18% 4	2401
	21st to end	Night	47% 2 8% 23% 16% 4	1980
March	1st to 10th	Night	49% 2 9% 17% 16% 7%	5374
	11th to 20th	Night	47% 3 15% 20% 13% 3	5192
	21st to end	Night	55% 2 4 13% 20% 6%	5150
April	1st to 10th	Night	49% 4 8% 20% 15% 4	2000
	11th to 20th	Night	49% 2 8% 20% 18% 3	1972
	21st to end	Night	48% 4 9% 20% 16% 4	1800
May	1st to 10th	Night	60% 4 13% 13% 8% 2	4060
	11th to 20th	Night	55% 5% 13% 16% 8% 2	4016
	21st to end	Night	52% 6% 12% 20% 10% 1	3927
June	1st to 10th	Night	46% 5% 12% 23% 13% 1	1600
	11th to 20th	Night	47% 4 12% 23% 14% 1	1600
	21st to end	Night	41% 7% 13% 24% 14% 1	1600
July	1st to 10th	Night	45% 5% 12% 23% 14%	3560
	11th to 20th	Night	45% 5% 16% 23% 10% 1	3552
	21st to end	Night	42% 5% 10% 27% 15% 1	3809
August	1st to 10th	Night	52% 7% 12% 19% 9% 1	2840
	11th to 20th	Night	43% 7% 13% 27% 9%	2985
	21st to end	Night	28% 4 15% 29% 22% 1	3586
September	1st to 10th	Night	41% 4 10% 25% 19% 2	2005
	11th to 20th	Night	36% 3 9% 24% 26% 2	2200
	21st to end	Night	46% 4 7% 21% 20% 2	2200
October	1st to 10th	Night	40% 4 11% 25% 17% 3	3590
	11th to 20th	Night	28% 2 8% 28% 31% 3	3953
	21st to end	Night	35% 3 11% 29% 20% 2	4610
November	1st to 10th	Night	37% 4 11% 24% 20% 3	2667
	11th to 20th	Night	41% 2 8% 23% 22% 3	2730
	21st to end	Night	40% 3 13% 28% 14% 2	2730
December	1st to 10th	Night	43% 2 11% 28% 15% 1	4618
	11th to 20th	Night	47% 3 13% 15% 20% 2	5348
	21st to end	Night	47% 4 7% 22% 17% 3	7150

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	34% 25% 26% 13% 3	220
	11th to 20th	Day	35% 22% 34% 7% 1	220
	21st to end	Day	33% 25% 31% 9% 1 1	242
February	1st to 10th	Day	33% 22% 31% 13% 1	461
	11th to 20th	Day	35% 28% 29% 7% 2	516
	21st to end	Day	32% 22% 32% 11% 3	414
March	1st to 10th	Day	35% 19% 31% 12% 3	500
	11th to 20th	Day	35% 21% 28% 11% 4 1	500
	21st to end	Day	33% 21% 31% 8% 4 2	550
April	1st to 10th	Day	38% 19% 26% 11% 4 1	500
	11th to 20th	Day	34% 23% 28% 12% 3 1	492
	21st to end	Day	30% 16% 33% 16% 2 2	500
May	1st to 10th	Day	37% 20% 28% 13% 2	503
	11th to 20th	Day	23% 19% 40% 13% 4 1	527
	21st to end	Day	22% 14% 35% 20% 6% 2	573
June	1st to 10th	Day	24% 12% 34% 21% 7% 1	530
	11th to 20th	Day	19% 16% 38% 20% 6% 1	530
	21st to end	Day	19% 13% 39% 22% 7% 1	530
July	1st to 10th	Day	21% 9% 32% 25% 12% 2	525
	11th to 20th	Day	18% 7% 34% 27% 12% 2	524
	21st to end	Day	14% 9% 40% 26% 9% 1	576
August	1st to 10th	Day	14% 10% 33% 29% 10% 3	526
	11th to 20th	Day	15% 9% 32% 29% 12% 3	519
	21st to end	Day	14% 11% 33% 25% 13% 4	583
September	1st to 10th	Day	20% 12% 28% 24% 12% 5%	530
	11th to 20th	Day	18% 10% 28% 23% 14% 7%	530
	21st to end	Day	23% 11% 35% 18% 9% 4	530
October	1st to 10th	Day	28% 12% 26% 20% 9% 5%	530
	11th to 20th	Day	23% 14% 34% 15% 10% 3	473
	21st to end	Day	29% 15% 30% 17% 8% 1	462
November	1st to 10th	Day	25% 16% 32% 17% 9% 2	425
	11th to 20th	Day	30% 21% 29% 15% 5%	430
	21st to end	Day	30% 20% 29% 15% 6% 1	430
December	1st to 10th	Day	29% 27% 29% 12% 4	278
	11th to 20th	Day	39% 22% 30% 6% 2	220
	21st to end	Day	33% 21% 30% 11% 3 2	242
January	1st to 10th	Night	24% 21% 35% 17% 3	840
	11th to 20th	Night	30% 20% 33% 15% 2	840
	21st to end	Night	25% 21% 33% 18% 3	924
February	1st to 10th	Night	25% 19% 35% 20% 1	840
	11th to 20th	Night	28% 23% 33% 14% 2	804
	21st to end	Night	28% 20% 32% 17% 3	660
March	1st to 10th	Night	27% 19% 34% 17% 3	800
	11th to 20th	Night	23% 22% 33% 17% 4	800
	21st to end	Night	29% 19% 33% 15% 4	880
April	1st to 10th	Night	28% 20% 32% 16% 3	800
	11th to 20th	Night	26% 20% 33% 17% 5%	788
	21st to end	Night	26% 16% 39% 17% 3	600
May	1st to 10th	Night	32% 13% 31% 19% 4	600
	11th to 20th	Night	23% 17% 37% 20% 3	587
	21st to end	Night	21% 8% 37% 30% 4	433
June	1st to 10th	Night	18% 9% 35% 29% 10%	400
	11th to 20th	Night	22% 6% 36% 30% 6%	400
	21st to end	Night	17% 5% 38% 33% 6% 1	400
July	1st to 10th	Night	15% 4 34% 38% 9%	390
	11th to 20th	Night	16% 3 31% 38% 11% 1	388
	21st to end	Night	14% 4 33% 40% 8%	438
August	1st to 10th	Night	14% 5% 35% 36% 9%	558
	11th to 20th	Night	14% 6% 28% 40% 11% 1	639
	21st to end	Night	16% 5% 27% 36% 15% 2	880
September	1st to 10th	Night	16% 7% 32% 34% 11% 1	800
	11th to 20th	Night	17% 8% 28% 29% 17% 2	800
	21st to end	Night	23% 8% 29% 27% 12% 2	800
October	1st to 10th	Night	24% 10% 26% 26% 11% 2	800
	11th to 20th	Night	21% 11% 33% 22% 11% 1	800
	21st to end	Night	26% 14% 32% 21% 7%	880
November	1st to 10th	Night	20% 15% 31% 24% 9% 1	820
	11th to 20th	Night	24% 17% 35% 17% 6%	840
	21st to end	Night	25% 19% 32% 19% 5% 1	840
December	1st to 10th	Night	28% 17% 33% 18% 4	840
	11th to 20th	Night	28% 18% 31% 19% 3	840
	21st to end	Night	29% 18% 32% 18% 2	924

Page generated at 2026-02-13 01:42:17. Version ac07

Copyright © 2026 Attilla Danko.