Avonmore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Avonmore clear sky chart from 2005-11-06 to 2025-04-26.

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% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	113638
	Night	17% 13% 4 9% 5% 4 4 3 5% 6% 29%	114968
Transparency	Day	51% 6% 12% 20% 9% 1	117138
	Night	55% 6% 11% 18% 9% 1	119632
Seeing	Day	24% 16% 29% 20% 9% 2	15045
	Night	24% 12% 29% 25% 9% 1	24255

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	16% 19% 6% 15% 5% 5% 3 3 4 4 19%	3597
	11th to 20th	Day	12% 17% 8% 13% 7% 5% 4 4 5% 5% 20%	3570
	21st to end	Day	12% 20% 7% 11% 5% 6% 5% 4 5% 6% 19%	4048
February	1st to 10th	Day	16% 17% 4 11% 6% 4 5% 3 5% 6% 23%	1800
	11th to 20th	Day	15% 14% 5% 12% 7% 4 4 3 5% 5% 26%	1803
	21st to end	Day	19% 15% 5% 8% 6% 4 4 4 5% 5% 25%	1650
March	1st to 10th	Day	18% 13% 5% 11% 5% 5% 5% 3 4 5% 25%	4476
	11th to 20th	Day	12% 13% 4 9% 6% 5% 6% 4 5% 7% 30%	4876
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 4 5% 35%	5850
April	1st to 10th	Day	22% 13% 3 7% 4 3 3 3 4 5% 32%	2400
	11th to 20th	Day	21% 11% 3 8% 5% 3 3 2 4 5% 35%	2374
	21st to end	Day	23% 10% 3 8% 4 4 4 3 5% 5% 31%	2449
May	1st to 10th	Day	21% 9% 3 7% 5% 4 5% 4 6% 7% 30%	4426
	11th to 20th	Day	18% 11% 3 8% 5% 4 4 3 5% 7% 32%	4398
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 6% 8% 37%	4837
June	1st to 10th	Day	23% 8% 3 7% 5% 5% 4 4 6% 6% 29%	2660
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 5% 6% 8% 37%	2660
	21st to end	Day	20% 8% 2 7% 4 5% 4 4 7% 9% 30%	2660
July	1st to 10th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	13% 7% 3 6% 4 5% 6% 4 7% 9% 37%	4440
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 7% 8% 43%	4814
August	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 9% 34%	4423
	11th to 20th	Day	16% 7% 2 6% 4 4 4 4 6% 7% 39%	3929
	21st to end	Day	16% 6% 2 6% 5% 4 5% 4 6% 8% 38%	4180
September	1st to 10th	Day	14% 6% 3 6% 4 4 4 3 7% 7% 43%	2280
	11th to 20th	Day	13% 5% 1 5% 4 4 4 3 5% 7% 48%	2247
	21st to end	Day	18% 6% 2 6% 4 4 3 4 4 8% 40%	2080
October	1st to 10th	Day	20% 7% 2 7% 5% 4 4 4 4 8% 34%	1900
	11th to 20th	Day	19% 11% 3 9% 5% 5% 4 3 5% 5% 30%	1900
	21st to end	Day	25% 12% 3 7% 5% 4 4 3 4 5% 28%	1901
November	1st to 10th	Day	16% 10% 4 8% 5% 4 5% 4 5% 6% 32%	1761
	11th to 20th	Day	17% 13% 3 8% 5% 4 4 4 4 7% 30%	1663
	21st to end	Day	21% 15% 5% 10% 5% 5% 4 3 5% 6% 21%	1600
December	1st to 10th	Day	21% 21% 6% 10% 6% 4 4 4 5% 5% 14%	2600
	11th to 20th	Day	18% 17% 5% 11% 5% 5% 4 3 5% 4 23%	2986
	21st to end	Day	22% 16% 5% 11% 5% 4 5% 3 4 4 21%	3960
January	1st to 10th	Night	15% 21% 7% 14% 6% 4 4 2 4 5% 19%	6349
	11th to 20th	Night	11% 18% 8% 15% 7% 6% 6% 3 5% 4 16%	6315
	21st to end	Night	15% 17% 7% 13% 6% 6% 4 3 4 5% 20%	6904
February	1st to 10th	Night	15% 15% 5% 13% 6% 6% 5% 3 5% 5% 22%	2600
	11th to 20th	Night	14% 14% 4 13% 6% 5% 5% 3 5% 5% 26%	2482
	21st to end	Night	15% 17% 5% 9% 6% 5% 4 3 4 4 28%	1980
March	1st to 10th	Night	21% 14% 4 9% 5% 4 4 3 3 4 29%	5364
	11th to 20th	Night	14% 13% 3 9% 5% 4 4 4 5% 7% 30%	5081
	21st to end	Night	18% 12% 3 8% 5% 4 4 3 4 5% 33%	5082
April	1st to 10th	Night	23% 10% 3 8% 5% 4 4 3 5% 6% 30%	2000
	11th to 20th	Night	20% 11% 3 6% 5% 4 4 4 4 5% 34%	1975
	21st to end	Night	22% 9% 3 7% 4 3 4 3 4 6% 34%	1861
May	1st to 10th	Night	20% 9% 4 7% 4 5% 5% 4 7% 8% 27%	2514
	11th to 20th	Night	21% 10% 3 6% 4 4 3 3 5% 6% 35%	2495
	21st to end	Night	14% 7% 3 6% 4 4 5% 4 6% 8% 38%	2738
June	1st to 10th	Night	18% 8% 2 7% 6% 5% 5% 4 7% 10% 29%	1520
	11th to 20th	Night	15% 8% 2 5% 4 4 4 3 6% 9% 39%	1520
	21st to end	Night	20% 7% 2 6% 5% 4 3 4 7% 8% 34%	1520
July	1st to 10th	Night	13% 8% 3 8% 5% 5% 4 4 7% 8% 34%	2520
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 6% 9% 41%	2520
	21st to end	Night	12% 7% 2 6% 5% 4 5% 4 7% 9% 40%	2739
August	1st to 10th	Night	15% 8% 3 7% 4 4 5% 3 6% 8% 38%	2506
	11th to 20th	Night	15% 8% 2 6% 4 4 4 3 5% 8% 39%	2865
	21st to end	Night	13% 6% 3 6% 4 5% 5% 4 6% 8% 40%	3476
September	1st to 10th	Night	11% 7% 2 7% 5% 5% 4 4 5% 6% 44%	1900
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 5% 7% 49%	1932
	21st to end	Night	16% 6% 2 6% 4 4 5% 3 5% 6% 42%	2098
October	1st to 10th	Night	19% 9% 2 6% 4 4 5% 4 5% 6% 37%	2280
	11th to 20th	Night	20% 9% 3 8% 4 5% 4 3 5% 6% 33%	2280
	21st to end	Night	23% 10% 3 8% 5% 4 4 3 5% 6% 28%	2696
November	1st to 10th	Night	20% 11% 4 7% 4 4 4 3 5% 6% 33%	2537
	11th to 20th	Night	18% 11% 3 8% 5% 5% 5% 4 4 6% 32%	2735
	21st to end	Night	21% 14% 5% 10% 6% 4 4 3 4 5% 24%	2800
December	1st to 10th	Night	19% 18% 6% 12% 6% 5% 5% 4 4 5% 16%	4580
	11th to 20th	Night	23% 16% 5% 9% 5% 4 4 3 3 3 24%	5208
	21st to end	Night	26% 17% 4 10% 4 4 4 3 4 4 21%	6996

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	69% 6% 10% 12% 4	3598
	11th to 20th	Day	64% 7% 10% 11% 7%	3600
	21st to end	Day	65% 7% 10% 10% 7% 1	4048
February	1st to 10th	Day	63% 5% 8% 19% 4 1	1800
	11th to 20th	Day	60% 5% 11% 15% 7% 1	1812
	21st to end	Day	62% 5% 10% 13% 9% 1	1650
March	1st to 10th	Day	61% 5% 9% 14% 9% 3	4479
	11th to 20th	Day	53% 7% 15% 14% 9% 1	4876
	21st to end	Day	51% 5% 6% 18% 17% 2	5850
April	1st to 10th	Day	55% 4 7% 20% 12% 2	2400
	11th to 20th	Day	52% 4 6% 20% 16% 2	2374
	21st to end	Day	55% 5% 8% 16% 13% 3	2449
May	1st to 10th	Day	50% 9% 9% 20% 10% 2	4440
	11th to 20th	Day	50% 8% 12% 19% 9% 1	4402
	21st to end	Day	43% 8% 11% 24% 13% 1	4837
June	1st to 10th	Day	53% 7% 11% 18% 11% 1	2660
	11th to 20th	Day	42% 7% 12% 24% 12% 2	2660
	21st to end	Day	50% 8% 12% 20% 10% 1	2660
July	1st to 10th	Day	43% 7% 13% 26% 11%	4370
	11th to 20th	Day	40% 7% 15% 30% 7%	4365
	21st to end	Day	37% 8% 14% 32% 10%	4661
August	1st to 10th	Day	47% 7% 15% 23% 9%	4409
	11th to 20th	Day	41% 6% 18% 28% 7%	3968
	21st to end	Day	42% 7% 16% 24% 11%	4180
September	1st to 10th	Day	39% 7% 13% 27% 13%	2280
	11th to 20th	Day	36% 6% 12% 32% 13%	2247
	21st to end	Day	43% 7% 14% 26% 10%	2080
October	1st to 10th	Day	47% 5% 12% 28% 9%	3160
	11th to 20th	Day	48% 5% 15% 25% 6%	3140
	21st to end	Day	48% 4 17% 23% 6%	3113
November	1st to 10th	Day	51% 7% 13% 22% 7% 1	1761
	11th to 20th	Day	54% 6% 11% 17% 10% 1	1663
	21st to end	Day	64% 7% 12% 12% 5%	1600
December	1st to 10th	Day	72% 5% 11% 10% 1	2600
	11th to 20th	Day	65% 6% 8% 15% 6%	2986
	21st to end	Day	67% 4 9% 16% 5%	3960
January	1st to 10th	Night	70% 5% 10% 11% 3	6349
	11th to 20th	Night	68% 8% 9% 9% 4	6360
	21st to end	Night	67% 5% 9% 9% 10% 1	6904
February	1st to 10th	Night	65% 5% 9% 15% 6% 1	2600
	11th to 20th	Night	59% 5% 9% 19% 7%	2484
	21st to end	Night	59% 5% 8% 18% 10% 1	1980
March	1st to 10th	Night	60% 4 6% 15% 12% 2	5374
	11th to 20th	Night	51% 6% 16% 16% 8% 3	5082
	21st to end	Night	53% 4 6% 22% 12% 2	5082
April	1st to 10th	Night	55% 5% 8% 19% 13% 2	2000
	11th to 20th	Night	52% 6% 8% 19% 14% 1	1975
	21st to end	Night	51% 5% 8% 17% 15% 4	1861
May	1st to 10th	Night	51% 10% 11% 16% 9% 3	2520
	11th to 20th	Night	48% 9% 10% 19% 13% 2	2496
	21st to end	Night	40% 7% 14% 20% 17% 2	2739
June	1st to 10th	Night	48% 8% 13% 18% 11% 1	1520
	11th to 20th	Night	41% 6% 13% 21% 17% 1	1520
	21st to end	Night	46% 8% 13% 20% 12% 1	1520
July	1st to 10th	Night	45% 7% 13% 21% 14% 1	2480
	11th to 20th	Night	39% 7% 15% 31% 8%	2472
	21st to end	Night	40% 9% 15% 22% 14%	2651
August	1st to 10th	Night	45% 6% 15% 25% 9%	2496
	11th to 20th	Night	43% 6% 15% 28% 7%	2892
	21st to end	Night	40% 7% 15% 24% 12% 1	3476
September	1st to 10th	Night	41% 7% 10% 27% 15% 1	1900
	11th to 20th	Night	34% 6% 13% 33% 13% 1	1932
	21st to end	Night	41% 7% 11% 27% 13% 1	2098
October	1st to 10th	Night	44% 5% 13% 28% 9%	3800
	11th to 20th	Night	45% 5% 15% 27% 9%	3779
	21st to end	Night	49% 5% 17% 19% 9%	4434
November	1st to 10th	Night	51% 5% 13% 21% 9% 1	2537
	11th to 20th	Night	52% 6% 12% 19% 10% 2	2735
	21st to end	Night	62% 6% 11% 15% 5%	2800
December	1st to 10th	Night	71% 5% 10% 11% 2	4580
	11th to 20th	Night	65% 5% 7% 14% 9% 1	5208
	21st to end	Night	68% 4 7% 12% 9%	6996

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% 16% 27% 21% 4	200
	11th to 20th	Day	27% 28% 30% 13% 4 1	200
	21st to end	Day	21% 22% 36% 16% 5%	238
February	1st to 10th	Day	32% 28% 28% 10% 2	300
	11th to 20th	Day	26% 27% 36% 10% 1	350
	21st to end	Day	31% 19% 34% 14% 2	414
March	1st to 10th	Day	28% 19% 30% 19% 4	500
	11th to 20th	Day	23% 24% 34% 16% 3 1	500
	21st to end	Day	31% 20% 26% 15% 6% 1	550
April	1st to 10th	Day	32% 19% 27% 16% 5% 1	500
	11th to 20th	Day	31% 21% 23% 16% 6% 2	492
	21st to end	Day	32% 16% 28% 15% 8% 1	480
May	1st to 10th	Day	27% 15% 30% 18% 8% 2	463
	11th to 20th	Day	18% 16% 33% 18% 11% 2	487
	21st to end	Day	19% 15% 31% 22% 11% 1	529
June	1st to 10th	Day	28% 11% 28% 22% 8% 3	490
	11th to 20th	Day	16% 13% 31% 28% 10% 2	490
	21st to end	Day	26% 14% 28% 18% 12% 2	490
July	1st to 10th	Day	14% 9% 26% 32% 14% 4	485
	11th to 20th	Day	14% 11% 30% 28% 15% 3	484
	21st to end	Day	16% 8% 31% 31% 13% 2	532
August	1st to 10th	Day	16% 8% 24% 34% 15% 3	486
	11th to 20th	Day	16% 7% 22% 32% 16% 7%	479
	21st to end	Day	16% 9% 29% 25% 13% 7%	539
September	1st to 10th	Day	15% 10% 30% 23% 14% 8%	490
	11th to 20th	Day	13% 8% 23% 24% 21% 11%	490
	21st to end	Day	19% 12% 32% 19% 14% 5%	490
October	1st to 10th	Day	25% 12% 27% 20% 12% 5%	490
	11th to 20th	Day	24% 19% 29% 19% 7% 1	490
	21st to end	Day	33% 15% 26% 19% 6%	439
November	1st to 10th	Day	27% 19% 27% 19% 7% 1	395
	11th to 20th	Day	24% 22% 35% 13% 6%	263
	21st to end	Day	32% 24% 26% 15% 4 1	200
December	1st to 10th	Day	31% 20% 26% 19% 4	200
	11th to 20th	Day	32% 28% 28% 11% 2 1	200
	21st to end	Day	30% 27% 25% 12% 5%	220
January	1st to 10th	Night	28% 18% 32% 19% 4	800
	11th to 20th	Night	29% 16% 29% 21% 5% 1	800
	21st to end	Night	20% 15% 34% 25% 6%	880
February	1st to 10th	Night	23% 18% 34% 23% 3	800
	11th to 20th	Night	24% 18% 35% 19% 4	783
	21st to end	Night	25% 17% 30% 25% 3	660
March	1st to 10th	Night	27% 15% 30% 23% 5%	800
	11th to 20th	Night	26% 16% 34% 20% 4	800
	21st to end	Night	26% 14% 28% 25% 6%	880
April	1st to 10th	Night	30% 13% 30% 24% 4	800
	11th to 20th	Night	24% 16% 33% 20% 7%	791
	21st to end	Night	27% 12% 30% 23% 7% 1	687
May	1st to 10th	Night	27% 8% 30% 26% 8% 2	380
	11th to 20th	Night	23% 7% 32% 29% 8% 1	374
	21st to end	Night	14% 9% 38% 27% 11%	411
June	1st to 10th	Night	19% 7% 28% 37% 8%	380
	11th to 20th	Night	19% 7% 28% 32% 13% 1	380
	21st to end	Night	19% 4 30% 30% 14% 1	380
July	1st to 10th	Night	11% 7% 26% 40% 15% 1	370
	11th to 20th	Night	14% 4 26% 37% 18% 1	368
	21st to end	Night	13% 5% 28% 42% 12% 1	416
August	1st to 10th	Night	15% 4 20% 45% 15% 1	378
	11th to 20th	Night	14% 5% 20% 37% 22% 1	605
	21st to end	Night	16% 5% 25% 34% 18% 2	836
September	1st to 10th	Night	14% 8% 28% 33% 16% 1	760
	11th to 20th	Night	17% 6% 21% 31% 21% 4	760
	21st to end	Night	19% 8% 29% 23% 19% 2	760
October	1st to 10th	Night	24% 7% 29% 26% 14% 1	760
	11th to 20th	Night	25% 10% 31% 24% 9%	760
	21st to end	Night	29% 14% 29% 23% 6%	836
November	1st to 10th	Night	27% 15% 27% 22% 8% 1	780
	11th to 20th	Night	24% 17% 32% 19% 8% 1	800
	21st to end	Night	29% 17% 26% 21% 7%	800
December	1st to 10th	Night	30% 17% 29% 20% 3	800
	11th to 20th	Night	31% 16% 32% 17% 5% 1	800
	21st to end	Night	34% 15% 28% 19% 4	880

Page generated at 2025-04-23 09:25:03. Version ac07

Copyright © 2025 Attilla Danko.