Waid Observatory (Margate)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waid Observatory (Margate) clear sky chart from 2005-11-06 to 2026-07-01.

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	7% 5% 2 7% 6% 6% 6% 6% 9% 11% 35%	136937
	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	135445
Transparency	Day	36% 11% 20% 21% 10% 2	140590
	Night	34% 10% 20% 22% 11% 3	139864
Seeing	Day	7% 3 16% 28% 28% 18%	18293
	Night	8% 3 14% 31% 32% 13%	28424

By Month

Percentage Cloud Cover SE (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	6% 4 2 5% 3 3 4 3 6% 10% 53%	5258
	11th to 20th	Day	14% 7% 3 9% 6% 6% 6% 5% 7% 9% 27%	5280
	21st to end	Day	11% 7% 2 8% 6% 5% 5% 4 6% 8% 38%	5822
February	1st to 10th	Day	9% 7% 2 6% 5% 4 5% 5% 7% 10% 41%	2100
	11th to 20th	Day	7% 5% 2 4 4 5% 4 4 7% 10% 48%	2182
	21st to end	Day	6% 6% 2 7% 5% 5% 6% 4 7% 9% 45%	1903
March	1st to 10th	Day	5% 5% 2 7% 5% 6% 6% 6% 8% 10% 40%	5045
	11th to 20th	Day	4 2 1 4 3 3 4 4 7% 9% 58%	5090
	21st to end	Day	7% 4 2 6% 6% 5% 5% 5% 8% 10% 42%	5586
April	1st to 10th	Day	5% 5% 1 5% 4 4 5% 5% 9% 13% 44%	2310
	11th to 20th	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 10% 41%	2398
	21st to end	Day	6% 4 2 5% 6% 6% 5% 5% 8% 11% 43%	2520
May	1st to 10th	Day	4 3 1 3 3 4 4 4 8% 12% 53%	7021
	11th to 20th	Day	5% 4 2 6% 5% 5% 7% 5% 9% 12% 40%	7084
	21st to end	Day	4 4 2 6% 5% 6% 8% 7% 10% 14% 35%	8391
June	1st to 10th	Day	13% 9% 3 11% 8% 8% 7% 6% 8% 9% 17%	2730
	11th to 20th	Day	8% 7% 3 10% 7% 9% 8% 7% 9% 11% 22%	2730
	21st to end	Day	7% 7% 2 8% 7% 7% 9% 7% 10% 12% 23%	2730
July	1st to 10th	Day	5% 6% 3 9% 7% 7% 7% 6% 9% 14% 25%	5900
	11th to 20th	Day	5% 5% 3 8% 6% 7% 8% 7% 10% 13% 28%	5900
	21st to end	Day	3 3 2 5% 5% 5% 7% 6% 11% 16% 36%	6424
August	1st to 10th	Day	5% 5% 3 10% 8% 8% 9% 8% 11% 13% 21%	4142
	11th to 20th	Day	4 4 2 7% 6% 7% 8% 7% 11% 16% 26%	3850
	21st to end	Day	5% 5% 2 7% 7% 7% 10% 7% 12% 18% 21%	4057
September	1st to 10th	Day	9% 6% 3 10% 7% 8% 9% 8% 9% 11% 20%	2200
	11th to 20th	Day	7% 7% 3 9% 9% 9% 9% 7% 10% 11% 19%	2200
	21st to end	Day	11% 9% 3 10% 8% 8% 8% 7% 8% 9% 19%	2200
October	1st to 10th	Day	10% 7% 4 9% 7% 7% 7% 6% 9% 11% 22%	2093
	11th to 20th	Day	10% 6% 4 7% 6% 7% 8% 6% 9% 10% 28%	2000
	21st to end	Day	11% 6% 3 7% 5% 6% 5% 5% 7% 9% 35%	2200
November	1st to 10th	Day	8% 6% 2 6% 5% 7% 6% 5% 8% 10% 37%	2057
	11th to 20th	Day	10% 7% 3 7% 6% 6% 6% 5% 7% 8% 34%	2100
	21st to end	Day	8% 4 3 6% 6% 6% 6% 5% 8% 8% 40%	2100
December	1st to 10th	Day	6% 4 2 5% 4 4 4 5% 6% 8% 51%	3306
	11th to 20th	Day	8% 6% 2 7% 5% 6% 6% 6% 8% 11% 36%	3463
	21st to end	Day	11% 7% 3 8% 6% 6% 6% 6% 8% 10% 29%	4565
January	1st to 10th	Night	5% 4 2 6% 4 4 5% 4 6% 8% 52%	7635
	11th to 20th	Night	13% 9% 3 9% 5% 5% 5% 4 6% 8% 30%	7680
	21st to end	Night	11% 8% 3 7% 5% 5% 4 4 5% 6% 42%	8341
February	1st to 10th	Night	8% 6% 2 5% 4 3 4 4 7% 9% 48%	2520
	11th to 20th	Night	6% 3 2 5% 4 3 5% 4 6% 7% 55%	2320
	21st to end	Night	6% 3 1 5% 3 4 4 3 5% 8% 56%	1903
March	1st to 10th	Night	4 4 2 6% 4 4 5% 4 7% 9% 50%	5028
	11th to 20th	Night	5% 3 1 4 2 4 4 3 5% 9% 60%	5090
	21st to end	Night	6% 4 2 5% 5% 4 5% 5% 7% 8% 49%	5588
April	1st to 10th	Night	4 3 1 5% 3 4 4 4 7% 10% 56%	2310
	11th to 20th	Night	5% 4 2 5% 4 5% 5% 5% 7% 9% 50%	2170
	21st to end	Night	6% 5% 1 4 4 3 4 4 8% 9% 51%	2100
May	1st to 10th	Night	3 3 1 4 3 3 4 4 7% 11% 57%	5833
	11th to 20th	Night	5% 5% 2 6% 4 4 5% 4 8% 11% 45%	5830
	21st to end	Night	4 4 2 5% 5% 5% 6% 6% 11% 13% 38%	5761
June	1st to 10th	Night	12% 7% 3 9% 6% 7% 6% 7% 8% 9% 26%	1890
	11th to 20th	Night	7% 6% 2 7% 6% 6% 7% 5% 10% 13% 32%	1890
	21st to end	Night	5% 5% 2 7% 6% 7% 7% 6% 10% 13% 33%	1890
July	1st to 10th	Night	4 6% 3 9% 6% 6% 6% 5% 8% 12% 35%	4058
	11th to 20th	Night	4 4 2 8% 6% 5% 6% 5% 9% 13% 38%	4057
	21st to end	Night	2 3 2 5% 4 4 5% 4 8% 13% 50%	4427
August	1st to 10th	Night	4 4 2 6% 6% 7% 8% 7% 10% 13% 34%	2974
	11th to 20th	Night	2 3 2 6% 5% 6% 7% 6% 9% 14% 41%	3197
	21st to end	Night	5% 4 2 6% 5% 8% 8% 8% 13% 17% 24%	3834
September	1st to 10th	Night	6% 6% 2 8% 5% 8% 8% 7% 9% 12% 27%	2200
	11th to 20th	Night	9% 6% 3 8% 7% 7% 7% 6% 10% 11% 27%	2200
	21st to end	Night	9% 7% 2 10% 7% 7% 7% 7% 9% 10% 25%	2200
October	1st to 10th	Night	8% 6% 3 10% 6% 8% 8% 5% 9% 10% 26%	2305
	11th to 20th	Night	10% 5% 2 6% 5% 6% 5% 5% 7% 11% 37%	2400
	21st to end	Night	11% 6% 2 6% 5% 4 5% 5% 6% 9% 41%	2640
November	1st to 10th	Night	9% 6% 2 7% 4 4 6% 4 6% 9% 44%	2461
	11th to 20th	Night	9% 6% 2 7% 5% 6% 5% 4 7% 9% 40%	2520
	21st to end	Night	8% 6% 2 6% 4 5% 4 4 6% 10% 44%	2520
December	1st to 10th	Night	7% 4 2 5% 4 4 4 3 5% 9% 53%	4088
	11th to 20th	Night	11% 8% 3 7% 6% 5% 5% 4 7% 8% 35%	4952
	21st to end	Night	9% 8% 3 9% 6% 6% 6% 5% 8% 9% 30%	6633

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	25% 6% 10% 33% 20% 7%	5259
	11th to 20th	Day	50% 8% 14% 18% 7% 3	5280
	21st to end	Day	42% 6% 8% 28% 12% 4	5822
February	1st to 10th	Day	35% 8% 14% 22% 15% 6%	2100
	11th to 20th	Day	27% 7% 13% 29% 19% 6%	2192
	21st to end	Day	32% 8% 13% 17% 22% 8%	1903
March	1st to 10th	Day	32% 12% 13% 20% 19% 4	5045
	11th to 20th	Day	18% 9% 14% 29% 19% 11%	5090
	21st to end	Day	32% 8% 13% 27% 15% 4	5586
April	1st to 10th	Day	26% 9% 20% 25% 16% 3	2310
	11th to 20th	Day	33% 10% 15% 19% 17% 5%	2398
	21st to end	Day	30% 9% 13% 26% 19% 3	2520
May	1st to 10th	Day	20% 7% 19% 38% 15% 2	7053
	11th to 20th	Day	31% 10% 24% 28% 6% 1	7088
	21st to end	Day	31% 10% 28% 24% 7%	8405
June	1st to 10th	Day	58% 13% 16% 10% 3	2730
	11th to 20th	Day	48% 17% 19% 14% 2	2730
	21st to end	Day	46% 17% 26% 10% 1	2730
July	1st to 10th	Day	42% 14% 32% 13%	5835
	11th to 20th	Day	41% 14% 31% 13% 1	5831
	21st to end	Day	28% 14% 34% 23% 1	6240
August	1st to 10th	Day	45% 18% 26% 10% 1	4129
	11th to 20th	Day	35% 16% 31% 17% 1	3886
	21st to end	Day	40% 17% 36% 6%	4057
September	1st to 10th	Day	48% 21% 20% 10% 1	2200
	11th to 20th	Day	50% 20% 19% 9% 2	2200
	21st to end	Day	53% 18% 14% 10% 5% 1	2200
October	1st to 10th	Day	48% 14% 18% 15% 4 1	3405
	11th to 20th	Day	47% 10% 16% 17% 10% 1	3240
	21st to end	Day	37% 7% 12% 27% 14% 3	3538
November	1st to 10th	Day	37% 10% 14% 18% 15% 6%	2057
	11th to 20th	Day	44% 9% 11% 16% 15% 4	2100
	21st to end	Day	38% 10% 13% 18% 18% 4	2100
December	1st to 10th	Day	28% 7% 15% 28% 17% 4	3306
	11th to 20th	Day	38% 8% 14% 20% 17% 4	3460
	21st to end	Day	45% 9% 15% 15% 14% 2	4565
January	1st to 10th	Night	28% 7% 12% 30% 18% 6%	7636
	11th to 20th	Night	49% 7% 18% 15% 8% 3	7680
	21st to end	Night	39% 7% 10% 29% 11% 4	8341
February	1st to 10th	Night	30% 8% 15% 26% 16% 5%	2520
	11th to 20th	Night	25% 7% 13% 29% 20% 6%	2321
	21st to end	Night	25% 7% 13% 23% 25% 7%	1903
March	1st to 10th	Night	27% 10% 14% 22% 23% 4	5028
	11th to 20th	Night	19% 8% 20% 26% 17% 9%	5090
	21st to end	Night	29% 7% 15% 27% 19% 3	5588
April	1st to 10th	Night	21% 9% 20% 32% 15% 3	2310
	11th to 20th	Night	27% 9% 18% 21% 20% 5%	2170
	21st to end	Night	26% 9% 17% 27% 18% 4	2100
May	1st to 10th	Night	20% 6% 25% 36% 12% 2	5863
	11th to 20th	Night	29% 10% 23% 28% 9%	5831
	21st to end	Night	30% 11% 33% 22% 5%	5771
June	1st to 10th	Night	48% 15% 22% 13% 3	1890
	11th to 20th	Night	39% 17% 24% 17% 3	1890
	21st to end	Night	37% 18% 31% 12% 1	1890
July	1st to 10th	Night	40% 12% 35% 12%	4015
	11th to 20th	Night	35% 12% 41% 12%	4006
	21st to end	Night	24% 12% 40% 22% 2	4297
August	1st to 10th	Night	37% 17% 28% 16% 2	2963
	11th to 20th	Night	30% 15% 33% 22%	3227
	21st to end	Night	39% 19% 35% 6% 1	3834
September	1st to 10th	Night	43% 22% 23% 11% 1	2200
	11th to 20th	Night	45% 20% 22% 11% 2	2200
	21st to end	Night	49% 19% 14% 12% 6%	2200
October	1st to 10th	Night	49% 13% 19% 15% 4 1	3773
	11th to 20th	Night	46% 8% 17% 16% 11% 1	3899
	21st to end	Night	37% 7% 12% 27% 13% 4	4252
November	1st to 10th	Night	36% 8% 15% 19% 16% 6%	2461
	11th to 20th	Night	40% 9% 12% 22% 13% 5%	2520
	21st to end	Night	35% 9% 16% 18% 17% 5%	2520
December	1st to 10th	Night	29% 7% 16% 28% 17% 3	4088
	11th to 20th	Night	41% 9% 12% 19% 14% 5%	4954
	21st to end	Night	45% 11% 14% 16% 13% 2	6633

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	7% 8% 29% 39% 15% 2	330
	11th to 20th	Day	14% 11% 28% 29% 16% 3	330
	21st to end	Day	10% 9% 35% 36% 9% 1	363
February	1st to 10th	Day	7% 8% 25% 39% 18% 3	330
	11th to 20th	Day	7% 6% 23% 38% 22% 4	465
	21st to end	Day	5% 6% 22% 36% 29% 2	446
March	1st to 10th	Day	3 6% 30% 41% 17% 3	540
	11th to 20th	Day	6% 6% 26% 37% 22% 2	540
	21st to end	Day	5% 3 27% 35% 25% 5%	594
April	1st to 10th	Day	3 3 29% 40% 20% 5%	540
	11th to 20th	Day	5% 3 25% 38% 23% 5%	532
	21st to end	Day	5% 2 15% 42% 29% 6%	540
May	1st to 10th	Day	4 1 13% 39% 33% 9%	543
	11th to 20th	Day	9% 3 16% 32% 29% 11%	567
	21st to end	Day	9% 2 9% 20% 37% 23%	617
June	1st to 10th	Day	12% 2 9% 24% 35% 19%	570
	11th to 20th	Day	7% 2 7% 21% 31% 32%	570
	21st to end	Day	4 1 3 16% 31% 45%	570
July	1st to 10th	Day	5% 1 4 10% 34% 47%	525
	11th to 20th	Day	5% 1 4 12% 34% 44%	524
	21st to end	Day	3 1 4 16% 30% 47%	576
August	1st to 10th	Day	5% 2 5% 15% 34% 41%	526
	11th to 20th	Day	3 3 13% 36% 45%	519
	21st to end	Day	7% 1 5% 17% 36% 34%	583
September	1st to 10th	Day	9% 2 3 14% 31% 41%	530
	11th to 20th	Day	5% 2 6% 15% 32% 40%	530
	21st to end	Day	8% 3 8% 21% 32% 28%	530
October	1st to 10th	Day	9% 2 11% 28% 38% 11%	530
	11th to 20th	Day	10% 3 14% 31% 30% 12%	530
	21st to end	Day	9% 5% 20% 30% 28% 8%	583
November	1st to 10th	Day	9% 4 20% 33% 27% 7%	535
	11th to 20th	Day	10% 4 21% 34% 24% 5%	540
	21st to end	Day	6% 3 23% 37% 28% 3	540
December	1st to 10th	Day	9% 4 19% 37% 28% 3	512
	11th to 20th	Day	8% 5% 27% 33% 23% 5%	330
	21st to end	Day	10% 8% 24% 32% 21% 6%	363
January	1st to 10th	Night	8% 5% 22% 38% 26% 2	840
	11th to 20th	Night	10% 7% 24% 37% 21% 1	840
	21st to end	Night	8% 7% 27% 42% 16%	924
February	1st to 10th	Night	9% 6% 22% 40% 22% 2	840
	11th to 20th	Night	6% 5% 23% 40% 24% 1	823
	21st to end	Night	6% 3 20% 47% 23% 1	692
March	1st to 10th	Night	4 3 28% 42% 20% 2	840
	11th to 20th	Night	7% 4 21% 42% 24% 2	840
	21st to end	Night	5% 4 23% 44% 22% 2	924
April	1st to 10th	Night	5% 3 16% 49% 25% 2	840
	11th to 20th	Night	6% 3 21% 43% 26% 2	831
	21st to end	Night	7% 1 16% 46% 28% 2	840
May	1st to 10th	Night	4 1 12% 44% 36% 3	840
	11th to 20th	Night	7% 2 14% 40% 33% 3	829
	21st to end	Night	7% 1 8% 25% 47% 12%	683
June	1st to 10th	Night	11% 1 7% 22% 43% 16%	630
	11th to 20th	Night	6% 2 4 13% 47% 28%	630
	21st to end	Night	4 3 11% 39% 42%	630
July	1st to 10th	Night	5% 1 2 9% 40% 43%	585
	11th to 20th	Night	4 1 3 9% 41% 42%	582
	21st to end	Night	2 2 9% 41% 46%	657
August	1st to 10th	Night	7% 1 2 9% 45% 36%	630
	11th to 20th	Night	3 3 10% 44% 40%	790
	21st to end	Night	9% 2 4 14% 41% 31%	880
September	1st to 10th	Night	8% 2 6% 12% 39% 35%	800
	11th to 20th	Night	9% 2 7% 13% 41% 29%	800
	21st to end	Night	10% 2 8% 17% 37% 26%	800
October	1st to 10th	Night	10% 2 10% 28% 39% 11%	800
	11th to 20th	Night	10% 3 11% 27% 41% 9%	800
	21st to end	Night	13% 1 15% 35% 27% 7%	880
November	1st to 10th	Night	11% 3 20% 32% 29% 5%	820
	11th to 20th	Night	9% 4 17% 33% 33% 4	840
	21st to end	Night	9% 3 18% 39% 29% 2	840
December	1st to 10th	Night	8% 3 19% 36% 31% 3	840
	11th to 20th	Night	10% 5% 21% 33% 28% 4	840
	21st to end	Night	8% 5% 19% 36% 28% 4	924

Page generated at 2026-06-28 02:10:47. Version ac07

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