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 2026-08-30.

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	17% 10% 3 8% 5% 5% 5% 4 5% 7% 31%	144481
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 29%	137730
Transparency	Day	51% 6% 12% 21% 9% 1	147935
	Night	55% 6% 11% 18% 10% 1	142365
Seeing	Day	24% 16% 29% 20% 9% 2	16813
	Night	24% 13% 29% 25% 9% 1	25783

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	15% 19% 6% 14% 6% 5% 4 3 4 5% 19%	4661
	11th to 20th	Day	12% 18% 8% 13% 7% 5% 5% 4 4 5% 18%	4650
	21st to end	Day	10% 17% 7% 13% 8% 8% 6% 4 4 5% 18%	5240
February	1st to 10th	Day	16% 17% 4 12% 6% 4 4 3 5% 6% 24%	1890
	11th to 20th	Day	15% 13% 5% 12% 7% 4 4 3 5% 6% 26%	1896
	21st to end	Day	19% 16% 5% 9% 6% 5% 4 4 5% 5% 24%	1730
March	1st to 10th	Day	18% 13% 4 11% 5% 5% 5% 3 5% 6% 25%	4576
	11th to 20th	Day	13% 13% 4 9% 6% 5% 6% 4 5% 7% 29%	4983
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 4 5% 35%	5979
April	1st to 10th	Day	22% 13% 4 7% 4 3 3 3 4 5% 32%	2520
	11th to 20th	Day	22% 11% 3 8% 4 4 3 2 4 5% 35%	2494
	21st to end	Day	23% 10% 3 8% 4 4 4 3 5% 5% 32%	2641
May	1st to 10th	Day	23% 10% 3 8% 5% 4 5% 4 5% 7% 24%	8237
	11th to 20th	Day	18% 10% 3 9% 5% 4 5% 3 5% 7% 32%	8221
	21st to end	Day	21% 9% 3 6% 4 4 4 4 5% 6% 34%	9060
June	1st to 10th	Day	22% 8% 3 7% 5% 5% 4 4 6% 7% 30%	2940
	11th to 20th	Day	15% 6% 3 7% 5% 5% 5% 5% 6% 8% 36%	2940
	21st to end	Day	19% 8% 2 7% 4 5% 4 4 7% 9% 31%	2940
July	1st to 10th	Day	11% 6% 3 8% 5% 5% 6% 5% 7% 10% 35%	8280
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 6% 10% 45%	8280
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 7% 9% 41%	8993
August	1st to 10th	Day	15% 8% 3 7% 4 5% 5% 4 6% 9% 35%	4703
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 6% 8% 39%	4181
	21st to end	Day	15% 6% 2 6% 5% 4 5% 4 6% 8% 38%	4420
September	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 7% 8% 43%	2400
	11th to 20th	Day	13% 5% 1 5% 4 4 4 3 5% 7% 49%	2365
	21st to end	Day	18% 6% 2 6% 4 5% 3 4 5% 8% 39%	2189
October	1st to 10th	Day	20% 7% 2 7% 4 4 4 3 4 8% 37%	2000
	11th to 20th	Day	19% 10% 3 9% 5% 5% 4 3 5% 5% 31%	2000
	21st to end	Day	25% 12% 3 7% 4 4 4 3 4 5% 28%	2001
November	1st to 10th	Day	16% 11% 4 8% 5% 4 5% 4 5% 6% 31%	1851
	11th to 20th	Day	17% 14% 4 8% 5% 4 4 4 4 7% 29%	1746
	21st to end	Day	21% 16% 5% 10% 5% 5% 4 3 5% 5% 21%	1680
December	1st to 10th	Day	20% 21% 5% 10% 6% 4 4 4 5% 5% 14%	2680
	11th to 20th	Day	18% 16% 5% 11% 5% 5% 4 3 5% 4 22%	3066
	21st to end	Day	22% 15% 5% 12% 6% 5% 5% 3 4 4 21%	4048
January	1st to 10th	Night	14% 19% 7% 15% 6% 4 4 2 4 5% 20%	8234
	11th to 20th	Night	12% 19% 8% 16% 7% 6% 5% 3 5% 4 15%	8235
	21st to end	Night	13% 15% 6% 12% 7% 7% 5% 4 5% 5% 21%	8937
February	1st to 10th	Night	15% 15% 5% 13% 6% 6% 5% 3 5% 5% 22%	2730
	11th to 20th	Night	14% 15% 4 13% 6% 5% 4 3 5% 5% 27%	2609
	21st to end	Night	15% 17% 5% 9% 6% 5% 4 3 4 5% 28%	2076
March	1st to 10th	Night	21% 14% 4 9% 5% 4 4 3 3 4 29%	5484
	11th to 20th	Night	15% 13% 3 9% 5% 4 4 4 5% 7% 30%	5194
	21st to end	Night	18% 12% 3 8% 5% 4 4 3 4 5% 33%	5195
April	1st to 10th	Night	23% 10% 3 8% 5% 4 4 3 5% 5% 30%	2100
	11th to 20th	Night	20% 11% 3 6% 5% 4 4 4 4 5% 33%	2075
	21st to end	Night	22% 9% 4 7% 4 3 3 3 4 6% 35%	1993
May	1st to 10th	Night	21% 10% 4 9% 5% 5% 6% 4 6% 7% 21%	4660
	11th to 20th	Night	18% 10% 3 7% 5% 5% 4 4 5% 7% 33%	4639
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 6% 7% 32%	5114
June	1st to 10th	Night	18% 8% 2 6% 6% 5% 6% 4 7% 9% 30%	1680
	11th to 20th	Night	16% 8% 2 5% 4 4 4 3 5% 9% 39%	1680
	21st to end	Night	19% 7% 3 6% 5% 4 3 4 7% 7% 35%	1680
July	1st to 10th	Night	12% 7% 2 7% 5% 5% 5% 4 8% 10% 34%	4680
	11th to 20th	Night	11% 7% 2 5% 4 3 4 4 6% 9% 45%	4680
	21st to end	Night	13% 6% 2 7% 5% 4 5% 4 7% 8% 39%	5084
August	1st to 10th	Night	15% 8% 3 7% 4 4 5% 3 6% 8% 39%	2666
	11th to 20th	Night	15% 8% 2 6% 4 4 4 3 5% 7% 40%	3050
	21st to end	Night	13% 6% 3 6% 4 5% 5% 4 5% 8% 40%	3677
September	1st to 10th	Night	11% 7% 2 7% 5% 5% 4 4 5% 6% 44%	2000
	11th to 20th	Night	14% 5% 2 5% 3 3 4 3 5% 7% 49%	2034
	21st to end	Night	16% 6% 2 6% 4 4 5% 3 5% 6% 42%	2209
October	1st to 10th	Night	19% 8% 2 5% 4 4 5% 4 5% 6% 39%	2400
	11th to 20th	Night	19% 9% 3 8% 4 5% 5% 3 5% 6% 34%	2400
	21st to end	Night	23% 10% 3 8% 5% 4 4 4 5% 6% 28%	2838
November	1st to 10th	Night	20% 11% 4 7% 4 4 3 3 5% 6% 33%	2667
	11th to 20th	Night	18% 12% 3 8% 5% 5% 5% 4 4 6% 32%	2872
	21st to end	Night	21% 14% 5% 10% 6% 4 4 3 4 5% 23%	2940
December	1st to 10th	Night	19% 18% 6% 12% 6% 5% 5% 4 4 5% 16%	4720
	11th to 20th	Night	23% 16% 5% 10% 5% 4 4 3 3 3 24%	5348
	21st to end	Night	26% 17% 5% 11% 4 4 4 3 4 4 21%	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	68% 5% 10% 12% 4	4662
	11th to 20th	Day	67% 6% 8% 10% 8% 1	4680
	21st to end	Day	68% 6% 9% 9% 8% 1	5240
February	1st to 10th	Day	63% 4 8% 20% 4 1	1890
	11th to 20th	Day	60% 5% 11% 16% 7% 1	1905
	21st to end	Day	63% 5% 10% 12% 8% 1	1730
March	1st to 10th	Day	60% 5% 9% 14% 9% 3	4579
	11th to 20th	Day	54% 7% 15% 14% 9% 1	4983
	21st to end	Day	51% 5% 6% 18% 17% 2	5979
April	1st to 10th	Day	56% 4 7% 19% 12% 2	2520
	11th to 20th	Day	53% 4 6% 20% 15% 2	2494
	21st to end	Day	54% 5% 8% 17% 14% 3	2641
May	1st to 10th	Day	57% 7% 8% 18% 9% 1	8249
	11th to 20th	Day	51% 6% 12% 22% 9% 1	8225
	21st to end	Day	50% 6% 10% 24% 10% 1	9061
June	1st to 10th	Day	52% 7% 10% 18% 12% 1	2940
	11th to 20th	Day	43% 7% 12% 25% 12% 2	2940
	21st to end	Day	49% 8% 12% 21% 10% 1	2940
July	1st to 10th	Day	42% 7% 15% 25% 11%	8210
	11th to 20th	Day	34% 6% 14% 34% 12%	8205
	21st to end	Day	38% 7% 15% 32% 8%	8795
August	1st to 10th	Day	46% 7% 15% 23% 9%	4689
	11th to 20th	Day	41% 6% 17% 29% 7%	4220
	21st to end	Day	42% 7% 16% 24% 10%	4420
September	1st to 10th	Day	38% 7% 13% 29% 12%	2400
	11th to 20th	Day	35% 6% 12% 33% 14%	2365
	21st to end	Day	43% 7% 13% 26% 11%	2189
October	1st to 10th	Day	45% 4 12% 28% 10%	3260
	11th to 20th	Day	48% 5% 15% 25% 6% 1	3240
	21st to end	Day	48% 4 17% 23% 7%	3213
November	1st to 10th	Day	52% 7% 12% 21% 8% 1	1851
	11th to 20th	Day	56% 6% 11% 17% 10% 1	1746
	21st to end	Day	65% 7% 11% 12% 5%	1680
December	1st to 10th	Day	72% 5% 11% 10% 1	2680
	11th to 20th	Day	65% 6% 9% 15% 6%	3066
	21st to end	Day	67% 4 9% 15% 5%	4048
January	1st to 10th	Night	69% 5% 10% 12% 4	8234
	11th to 20th	Night	71% 7% 8% 9% 5%	8280
	21st to end	Night	65% 4 8% 12% 10% 1	8937
February	1st to 10th	Night	64% 5% 9% 16% 6% 1	2730
	11th to 20th	Night	59% 5% 9% 19% 7%	2611
	21st to end	Night	59% 5% 8% 17% 10% 1	2076
March	1st to 10th	Night	60% 4 7% 15% 12% 2	5494
	11th to 20th	Night	52% 6% 16% 16% 8% 3	5195
	21st to end	Night	54% 4 6% 22% 12% 2	5195
April	1st to 10th	Night	55% 5% 8% 18% 13% 1	2100
	11th to 20th	Night	52% 6% 8% 18% 14% 1	2075
	21st to end	Night	50% 5% 8% 17% 16% 4	1993
May	1st to 10th	Night	58% 8% 11% 16% 6% 2	4666
	11th to 20th	Night	49% 8% 10% 21% 12% 1	4640
	21st to end	Night	49% 6% 11% 19% 14% 1	5115
June	1st to 10th	Night	48% 8% 12% 19% 12% 1	1680
	11th to 20th	Night	41% 6% 13% 21% 17% 2	1680
	21st to end	Night	47% 8% 12% 21% 12%	1680
July	1st to 10th	Night	43% 6% 17% 21% 13% 1	4640
	11th to 20th	Night	36% 5% 13% 32% 14%	4632
	21st to end	Night	41% 7% 13% 25% 13%	4967
August	1st to 10th	Night	44% 6% 16% 25% 9% 1	2656
	11th to 20th	Night	43% 6% 15% 28% 8%	3077
	21st to end	Night	41% 7% 15% 24% 12% 1	3677
September	1st to 10th	Night	40% 7% 10% 29% 14% 1	2000
	11th to 20th	Night	33% 6% 13% 34% 13% 1	2034
	21st to end	Night	42% 7% 11% 27% 13% 1	2209
October	1st to 10th	Night	43% 5% 13% 28% 10% 1	3920
	11th to 20th	Night	45% 5% 14% 26% 9% 1	3899
	21st to end	Night	49% 5% 17% 20% 9%	4576
November	1st to 10th	Night	52% 5% 13% 21% 8% 1	2667
	11th to 20th	Night	53% 6% 12% 19% 9% 1	2872
	21st to end	Night	63% 6% 11% 15% 5%	2940
December	1st to 10th	Night	71% 5% 10% 11% 3	4720
	11th to 20th	Night	65% 5% 7% 13% 9% 1	5348
	21st to end	Night	68% 4 7% 12% 9%	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	33% 15% 28% 20% 3	220
	11th to 20th	Day	30% 27% 28% 11% 3	220
	21st to end	Day	21% 23% 35% 15% 5%	262
February	1st to 10th	Day	30% 26% 29% 12% 2	330
	11th to 20th	Day	25% 28% 35% 11% 1	383
	21st to end	Day	31% 19% 35% 14% 2	446
March	1st to 10th	Day	27% 21% 30% 18% 4	540
	11th to 20th	Day	26% 23% 32% 15% 3 1	540
	21st to end	Day	32% 21% 27% 14% 6% 1	594
April	1st to 10th	Day	33% 20% 27% 15% 5% 1	540
	11th to 20th	Day	33% 21% 22% 16% 6% 2	532
	21st to end	Day	32% 17% 28% 15% 7% 1	540
May	1st to 10th	Day	28% 17% 30% 17% 7% 1	543
	11th to 20th	Day	19% 18% 33% 18% 10% 2	567
	21st to end	Day	23% 16% 30% 20% 10% 1	617
June	1st to 10th	Day	27% 12% 29% 21% 8% 3	570
	11th to 20th	Day	17% 14% 33% 25% 8% 2	570
	21st to end	Day	24% 15% 31% 18% 11% 2	570
July	1st to 10th	Day	14% 10% 29% 30% 14% 4	565
	11th to 20th	Day	14% 12% 32% 26% 13% 3	564
	21st to end	Day	16% 10% 30% 29% 13% 2	620
August	1st to 10th	Day	16% 8% 25% 33% 14% 3	566
	11th to 20th	Day	16% 8% 24% 31% 15% 6%	559
	21st to end	Day	16% 10% 29% 26% 12% 6%	619
September	1st to 10th	Day	15% 11% 29% 23% 15% 7%	530
	11th to 20th	Day	12% 8% 23% 25% 21% 11%	530
	21st to end	Day	19% 13% 32% 19% 14% 4	530
October	1st to 10th	Day	24% 12% 27% 21% 12% 5%	530
	11th to 20th	Day	24% 20% 30% 18% 6% 1	530
	21st to end	Day	33% 16% 27% 19% 6%	473
November	1st to 10th	Day	28% 20% 28% 18% 6% 1	425
	11th to 20th	Day	25% 21% 34% 13% 7% 1	286
	21st to end	Day	32% 24% 26% 14% 3 1	220
December	1st to 10th	Day	30% 21% 27% 18% 4	220
	11th to 20th	Day	31% 26% 30% 10% 2	220
	21st to end	Day	30% 27% 26% 12% 5%	242
January	1st to 10th	Night	27% 18% 33% 19% 3	840
	11th to 20th	Night	31% 16% 28% 21% 4 1	840
	21st to end	Night	21% 15% 33% 25% 6%	924
February	1st to 10th	Night	22% 17% 34% 23% 4	840
	11th to 20th	Night	24% 19% 35% 19% 4	823
	21st to end	Night	25% 17% 30% 25% 3	692
March	1st to 10th	Night	27% 15% 31% 22% 5%	840
	11th to 20th	Night	27% 16% 33% 19% 4	840
	21st to end	Night	27% 14% 29% 24% 6%	924
April	1st to 10th	Night	30% 14% 29% 24% 3	840
	11th to 20th	Night	25% 16% 32% 20% 7%	831
	21st to end	Night	27% 13% 29% 23% 7% 1	733
May	1st to 10th	Night	27% 9% 30% 26% 7% 1	420
	11th to 20th	Night	23% 9% 33% 27% 7%	414
	21st to end	Night	15% 10% 38% 27% 10%	455
June	1st to 10th	Night	19% 7% 29% 36% 8%	420
	11th to 20th	Night	20% 10% 28% 30% 11% 1	420
	21st to end	Night	19% 5% 31% 30% 14% 1	420
July	1st to 10th	Night	11% 6% 28% 40% 14%	410
	11th to 20th	Night	14% 6% 27% 36% 16%	408
	21st to end	Night	13% 6% 26% 42% 12% 1	460
August	1st to 10th	Night	14% 5% 21% 44% 15% 1	418
	11th to 20th	Night	14% 5% 21% 37% 21% 1	670
	21st to end	Night	16% 6% 25% 34% 17% 2	917
September	1st to 10th	Night	14% 8% 28% 33% 17% 1	800
	11th to 20th	Night	17% 6% 21% 31% 21% 4	800
	21st to end	Night	19% 8% 29% 23% 19% 2	800
October	1st to 10th	Night	23% 7% 29% 27% 14% 1	800
	11th to 20th	Night	25% 10% 32% 24% 9%	800
	21st to end	Night	29% 13% 29% 23% 6%	880
November	1st to 10th	Night	28% 15% 27% 22% 7% 1	820
	11th to 20th	Night	23% 18% 33% 19% 8%	840
	21st to end	Night	28% 18% 26% 21% 7%	840
December	1st to 10th	Night	30% 17% 29% 20% 3	840
	11th to 20th	Night	30% 17% 31% 17% 4 1	840
	21st to end	Night	34% 16% 27% 18% 4	924

Page generated at 2026-08-27 04:07:13. Version ac07

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