Poole's Resort Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poole's Resort Observatory clear sky chart from 2005-11-06 to 2026-06-01.

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 9% 5% 4 4 4 5% 7% 32%	132429
	Night	17% 12% 4 9% 5% 5% 4 3 5% 6% 29%	130702
Transparency	Day	35% 36% 8% 14% 6%	135920
	Night	39% 35% 7% 12% 6% 1	135298
Seeing	Day	24% 16% 30% 19% 9% 2	16475
	Night	25% 13% 29% 24% 9% 1	25674

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% 17% 6% 14% 6% 4 4 3 5% 5% 21%	4661
	11th to 20th	Day	13% 20% 9% 17% 6% 5% 4 3 4 5% 15%	4650
	21st to end	Day	11% 16% 6% 16% 9% 7% 5% 3 4 4 18%	5482
February	1st to 10th	Day	16% 17% 4 13% 6% 5% 4 3 5% 5% 21%	1890
	11th to 20th	Day	14% 16% 5% 11% 6% 5% 5% 4 5% 5% 24%	1863
	21st to end	Day	19% 16% 5% 12% 7% 5% 4 3 4 5% 21%	1730
March	1st to 10th	Day	20% 13% 4 11% 5% 3 3 3 4 5% 28%	4612
	11th to 20th	Day	11% 14% 5% 9% 6% 5% 5% 4 6% 6% 30%	5090
	21st to end	Day	20% 10% 3 9% 5% 4 3 3 4 5% 35%	5883
April	1st to 10th	Day	21% 13% 4 8% 5% 4 3 3 4 5% 31%	2520
	11th to 20th	Day	22% 10% 3 7% 4 3 4 3 4 5% 36%	2494
	21st to end	Day	21% 11% 3 8% 4 3 4 4 5% 5% 32%	2605
May	1st to 10th	Day	25% 11% 3 8% 5% 4 4 3 5% 6% 25%	6486
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 4 6% 6% 33%	6458
	21st to end	Day	21% 9% 3 6% 4 4 4 4 5% 8% 33%	7103
June	1st to 10th	Day	20% 7% 3 6% 5% 4 5% 3 5% 8% 33%	2800
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 4 6% 9% 38%	2800
	21st to end	Day	17% 8% 2 7% 4 4 5% 4 6% 7% 36%	2800
July	1st to 10th	Day	11% 6% 2 7% 5% 4 5% 5% 7% 9% 38%	6360
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 4 7% 8% 42%	6360
	21st to end	Day	10% 5% 2 5% 4 4 4 5% 7% 9% 44%	6926
August	1st to 10th	Day	15% 7% 3 7% 4 4 4 4 5% 8% 38%	4410
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 7% 9% 36%	4090
	21st to end	Day	16% 6% 2 5% 4 4 4 4 6% 10% 40%	4312
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 5% 8% 43%	2400
	11th to 20th	Day	11% 6% 2 5% 4 5% 3 3 5% 8% 48%	2400
	21st to end	Day	17% 7% 2 7% 4 4 5% 4 5% 6% 38%	2135
October	1st to 10th	Day	21% 8% 3 7% 4 4 3 4 5% 7% 37%	2000
	11th to 20th	Day	20% 10% 3 8% 5% 4 6% 3 5% 6% 30%	2000
	21st to end	Day	25% 10% 3 8% 5% 5% 5% 3 4 5% 27%	2064
November	1st to 10th	Day	16% 10% 3 7% 5% 5% 4 5% 6% 7% 31%	1851
	11th to 20th	Day	15% 13% 4 9% 5% 5% 4 3 4 5% 31%	1720
	21st to end	Day	21% 15% 4 9% 6% 4 4 4 6% 6% 22%	1680
December	1st to 10th	Day	21% 17% 5% 13% 6% 4 4 4 4 5% 17%	2680
	11th to 20th	Day	20% 17% 6% 11% 5% 4 4 3 4 4 21%	3066
	21st to end	Day	22% 16% 5% 11% 5% 4 4 3 4 4 22%	4048
January	1st to 10th	Night	16% 18% 6% 13% 6% 5% 4 3 4 4 21%	8234
	11th to 20th	Night	14% 19% 7% 15% 7% 6% 5% 3 4 4 15%	8235
	21st to end	Night	14% 14% 6% 12% 7% 7% 5% 4 5% 5% 20%	8684
February	1st to 10th	Night	17% 15% 5% 13% 6% 5% 5% 3 4 5% 21%	2730
	11th to 20th	Night	14% 14% 5% 11% 6% 4 4 3 5% 6% 27%	2642
	21st to end	Night	18% 15% 5% 10% 6% 4 4 3 4 5% 26%	2076
March	1st to 10th	Night	21% 13% 3 9% 5% 5% 4 3 3 5% 29%	5442
	11th to 20th	Night	16% 13% 4 7% 4 4 4 4 5% 8% 31%	5089
	21st to end	Night	21% 12% 4 9% 5% 3 3 3 4 5% 31%	5290
April	1st to 10th	Night	21% 10% 2 8% 4 3 4 3 4 6% 33%	2100
	11th to 20th	Night	22% 9% 3 6% 5% 4 4 3 4 5% 35%	2075
	21st to end	Night	22% 9% 3 8% 4 4 3 4 4 6% 34%	2030
May	1st to 10th	Night	26% 11% 3 8% 4 4 4 4 5% 6% 24%	3674
	11th to 20th	Night	16% 9% 3 8% 5% 5% 5% 3 5% 7% 35%	3655
	21st to end	Night	19% 9% 2 7% 4 5% 5% 4 5% 7% 33%	4014
June	1st to 10th	Night	16% 9% 3 7% 5% 5% 5% 4 6% 8% 32%	1600
	11th to 20th	Night	13% 6% 3 6% 4 5% 5% 4 6% 8% 41%	1600
	21st to end	Night	18% 7% 2 6% 4 4 6% 4 6% 8% 35%	1600
July	1st to 10th	Night	13% 6% 3 7% 5% 5% 5% 4 6% 9% 37%	3600
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 6% 7% 43%	3600
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 8% 47%	3926
August	1st to 10th	Night	11% 8% 3 7% 4 4 4 4 6% 8% 40%	2735
	11th to 20th	Night	14% 8% 3 6% 4 4 4 4 5% 8% 41%	2926
	21st to end	Night	10% 5% 2 6% 5% 5% 6% 5% 8% 8% 39%	3586
September	1st to 10th	Night	12% 6% 3 7% 4 4 4 3 5% 7% 46%	2000
	11th to 20th	Night	13% 6% 1 5% 3 3 4 4 6% 8% 49%	2000
	21st to end	Night	16% 6% 2 7% 4 4 3 4 6% 7% 40%	2261
October	1st to 10th	Night	19% 8% 2 6% 4 4 5% 4 5% 7% 38%	2400
	11th to 20th	Night	19% 7% 3 8% 5% 5% 5% 4 5% 6% 33%	2400
	21st to end	Night	25% 9% 3 8% 5% 4 4 3 5% 5% 29%	2775
November	1st to 10th	Night	19% 11% 3 7% 4 4 3 3 5% 6% 35%	2667
	11th to 20th	Night	17% 11% 3 8% 5% 5% 5% 4 5% 6% 32%	2898
	21st to end	Night	22% 14% 3 9% 6% 4 5% 4 5% 6% 22%	2940
December	1st to 10th	Night	19% 17% 5% 13% 7% 5% 5% 4 5% 5% 15%	4720
	11th to 20th	Night	22% 16% 4 9% 4 4 3 3 4 4 26%	5348
	21st to end	Night	27% 14% 4 12% 5% 3 4 3 5% 4 19%	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	55% 22% 7% 12% 3 1	4662
	11th to 20th	Day	62% 21% 6% 4 6% 1	4680
	21st to end	Day	57% 22% 6% 7% 8%	5482
February	1st to 10th	Day	28% 59% 4 7% 2	1890
	11th to 20th	Day	27% 58% 3 9% 4	1872
	21st to end	Day	28% 59% 3 5% 4 1	1730
March	1st to 10th	Day	44% 28% 6% 9% 9% 2	4615
	11th to 20th	Day	38% 29% 15% 9% 8% 1	5090
	21st to end	Day	40% 28% 6% 14% 12% 1	5883
April	1st to 10th	Day	26% 59% 3 6% 6% 1	2520
	11th to 20th	Day	22% 59% 3 8% 6% 1	2494
	21st to end	Day	22% 59% 4 8% 6% 1	2605
May	1st to 10th	Day	47% 29% 6% 13% 4	6497
	11th to 20th	Day	39% 31% 9% 14% 8%	6462
	21st to end	Day	39% 29% 9% 17% 6%	7103
June	1st to 10th	Day	19% 62% 4 9% 6%	2800
	11th to 20th	Day	17% 62% 5% 10% 4 1	2800
	21st to end	Day	18% 61% 5% 10% 6% 1	2800
July	1st to 10th	Day	33% 24% 10% 24% 9%	6290
	11th to 20th	Day	30% 25% 10% 23% 12%	6285
	21st to end	Day	27% 25% 9% 31% 8%	6728
August	1st to 10th	Day	30% 36% 11% 16% 7%	4396
	11th to 20th	Day	31% 37% 8% 19% 5%	4129
	21st to end	Day	28% 35% 10% 20% 7%	4312
September	1st to 10th	Day	14% 58% 7% 15% 5% 1	2400
	11th to 20th	Day	13% 57% 6% 14% 9%	2400
	21st to end	Day	18% 58% 5% 12% 7%	2135
October	1st to 10th	Day	29% 35% 7% 23% 6%	3260
	11th to 20th	Day	30% 36% 11% 18% 5%	3240
	21st to end	Day	30% 35% 11% 20% 4	3315
November	1st to 10th	Day	29% 54% 6% 8% 3	1851
	11th to 20th	Day	26% 55% 5% 11% 3	1720
	21st to end	Day	30% 55% 7% 4 3	1680
December	1st to 10th	Day	49% 34% 10% 6% 1	2680
	11th to 20th	Day	48% 32% 6% 9% 5%	3066
	21st to end	Day	49% 26% 7% 14% 4	4048
January	1st to 10th	Night	56% 22% 9% 10% 4	8234
	11th to 20th	Night	62% 21% 4 7% 5%	8280
	21st to end	Night	57% 23% 4 8% 8%	8684
February	1st to 10th	Night	29% 59% 3 6% 3	2730
	11th to 20th	Night	26% 58% 5% 8% 4	2644
	21st to end	Night	26% 58% 4 7% 3	2076
March	1st to 10th	Night	45% 28% 3 12% 9% 3	5452
	11th to 20th	Night	37% 28% 14% 11% 6% 3	5090
	21st to end	Night	45% 27% 4 15% 8% 1	5290
April	1st to 10th	Night	24% 58% 3 8% 5%	2100
	11th to 20th	Night	22% 59% 3 7% 8% 1	2075
	21st to end	Night	22% 59% 4 7% 7% 1	2030
May	1st to 10th	Night	49% 29% 7% 10% 4 1	3680
	11th to 20th	Night	39% 30% 10% 13% 8%	3656
	21st to end	Night	41% 28% 7% 14% 10%	4015
June	1st to 10th	Night	19% 63% 4 8% 6% 1	1600
	11th to 20th	Night	18% 62% 4 8% 8% 1	1600
	21st to end	Night	19% 61% 4 10% 6% 1	1600
July	1st to 10th	Night	34% 25% 13% 17% 10% 1	3560
	11th to 20th	Night	33% 25% 9% 25% 8% 1	3552
	21st to end	Night	27% 25% 9% 27% 11%	3809
August	1st to 10th	Night	28% 36% 10% 17% 7% 1	2725
	11th to 20th	Night	31% 36% 9% 20% 4	2953
	21st to end	Night	27% 35% 9% 22% 7% 1	3586
September	1st to 10th	Night	15% 57% 7% 14% 6%	2000
	11th to 20th	Night	14% 57% 5% 16% 8% 1	2000
	21st to end	Night	17% 57% 6% 12% 8%	2261
October	1st to 10th	Night	27% 35% 7% 22% 9%	3920
	11th to 20th	Night	27% 35% 11% 19% 7%	3899
	21st to end	Night	32% 35% 10% 19% 4	4474
November	1st to 10th	Night	27% 53% 7% 9% 4	2667
	11th to 20th	Night	25% 54% 6% 10% 4	2898
	21st to end	Night	30% 55% 5% 8% 2	2940
December	1st to 10th	Night	51% 34% 7% 7% 1	4720
	11th to 20th	Night	46% 32% 5% 9% 7%	5348
	21st to end	Night	52% 26% 5% 9% 7%	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	25% 20% 36% 14% 5%	220
	11th to 20th	Day	36% 17% 30% 15% 2	220
	21st to end	Day	24% 23% 34% 15% 4	308
February	1st to 10th	Day	30% 25% 30% 13% 2	330
	11th to 20th	Day	29% 27% 33% 9% 1	350
	21st to end	Day	34% 19% 33% 13% 1	446
March	1st to 10th	Day	27% 20% 31% 17% 4	540
	11th to 20th	Day	29% 22% 31% 14% 4	540
	21st to end	Day	34% 20% 26% 14% 5% 1	594
April	1st to 10th	Day	33% 17% 31% 14% 5%	540
	11th to 20th	Day	32% 19% 26% 14% 7% 3	532
	21st to end	Day	30% 19% 30% 14% 6% 2	540
May	1st to 10th	Day	26% 18% 31% 18% 6% 1	543
	11th to 20th	Day	18% 16% 35% 20% 9% 2	567
	21st to end	Day	19% 15% 31% 23% 10% 1	617
June	1st to 10th	Day	25% 14% 31% 22% 7% 1	530
	11th to 20th	Day	16% 13% 36% 23% 10% 2	530
	21st to end	Day	21% 15% 33% 21% 8% 2	530
July	1st to 10th	Day	14% 9% 33% 27% 16% 2	525
	11th to 20th	Day	16% 9% 29% 29% 13% 3	524
	21st to end	Day	13% 10% 36% 27% 13% 2	576
August	1st to 10th	Day	15% 8% 28% 29% 17% 4	526
	11th to 20th	Day	15% 8% 25% 29% 16% 6%	519
	21st to end	Day	16% 10% 33% 22% 13% 7%	583
September	1st to 10th	Day	15% 12% 30% 24% 12% 6%	530
	11th to 20th	Day	11% 9% 24% 25% 19% 13%	530
	21st to end	Day	19% 10% 27% 24% 15% 4	530
October	1st to 10th	Day	24% 15% 25% 19% 13% 5%	530
	11th to 20th	Day	25% 19% 31% 18% 6% 2	530
	21st to end	Day	33% 15% 28% 18% 5% 1	508
November	1st to 10th	Day	27% 21% 29% 17% 6%	425
	11th to 20th	Day	29% 13% 35% 13% 7% 2	260
	21st to end	Day	31% 21% 34% 11% 2	220
December	1st to 10th	Day	34% 20% 26% 15% 5%	220
	11th to 20th	Day	32% 22% 34% 10% 2	220
	21st to end	Day	32% 19% 29% 15% 4	242
January	1st to 10th	Night	33% 16% 30% 17% 4	840
	11th to 20th	Night	31% 18% 29% 19% 4	840
	21st to end	Night	24% 16% 33% 20% 6%	924
February	1st to 10th	Night	26% 20% 32% 19% 3	840
	11th to 20th	Night	25% 17% 36% 18% 3	823
	21st to end	Night	27% 18% 32% 20% 3	692
March	1st to 10th	Night	29% 15% 32% 21% 4	840
	11th to 20th	Night	29% 16% 32% 20% 4 1	840
	21st to end	Night	27% 14% 34% 18% 7%	924
April	1st to 10th	Night	29% 14% 32% 23% 2	840
	11th to 20th	Night	28% 17% 29% 20% 6%	831
	21st to end	Night	27% 10% 31% 23% 8%	770
May	1st to 10th	Night	28% 9% 28% 26% 8% 1	420
	11th to 20th	Night	15% 11% 35% 31% 7%	414
	21st to end	Night	16% 9% 36% 28% 10% 1	455
June	1st to 10th	Night	20% 8% 29% 35% 8% 1	400
	11th to 20th	Night	14% 11% 29% 33% 13% 1	400
	21st to end	Night	19% 7% 28% 32% 13% 1	400
July	1st to 10th	Night	13% 6% 28% 39% 15%	390
	11th to 20th	Night	13% 4 28% 36% 19% 1	388
	21st to end	Night	14% 4 26% 42% 12% 1	438
August	1st to 10th	Night	12% 4 25% 37% 21%	482
	11th to 20th	Night	17% 4 18% 36% 22% 3	619
	21st to end	Night	14% 6% 27% 35% 16% 2	880
September	1st to 10th	Night	16% 8% 27% 31% 16% 2	800
	11th to 20th	Night	16% 6% 20% 29% 23% 6%	800
	21st to end	Night	19% 10% 25% 27% 18% 2	800
October	1st to 10th	Night	25% 12% 26% 20% 16% 2	800
	11th to 20th	Night	24% 14% 28% 25% 8% 1	800
	21st to end	Night	32% 12% 29% 23% 4	880
November	1st to 10th	Night	28% 15% 29% 21% 7%	820
	11th to 20th	Night	26% 17% 31% 17% 9%	840
	21st to end	Night	34% 18% 28% 15% 6%	840
December	1st to 10th	Night	33% 18% 28% 17% 3	840
	11th to 20th	Night	30% 18% 33% 16% 2 1	840
	21st to end	Night	34% 17% 29% 18% 2	924

Page generated at 2026-05-29 01:53:28. Version ac07

Copyright © 2026 Attilla Danko.