Tiplady Farms Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tiplady Farms Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	18% 10% 3 8% 5% 4 4 4 5% 6% 32%	126295
	Night	19% 12% 4 9% 5% 4 4 3 5% 6% 30%	122756
Transparency	Day	53% 5% 11% 20% 10% 1	129775
	Night	56% 5% 11% 17% 9% 1	127350
Seeing	Day	26% 17% 28% 18% 8% 2	15914
	Night	25% 15% 27% 24% 8% 1	24867

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	13% 14% 8% 21% 5% 4 4 3 4 3 21%	3597
	11th to 20th	Day	11% 14% 7% 14% 8% 5% 4 3 5% 5% 22%	3570
	21st to end	Day	14% 17% 6% 11% 5% 5% 4 3 4 4 27%	3983
February	1st to 10th	Day	15% 14% 5% 11% 8% 5% 4 4 6% 5% 23%	1800
	11th to 20th	Day	15% 16% 6% 12% 5% 5% 3 3 4 5% 26%	1936
	21st to end	Day	18% 14% 4 10% 6% 4 3 3 4 5% 28%	1650
March	1st to 10th	Day	22% 14% 6% 10% 5% 4 3 2 4 4 25%	4476
	11th to 20th	Day	15% 16% 4 7% 4 4 3 3 4 6% 34%	4671
	21st to end	Day	23% 10% 3 9% 5% 4 4 3 4 4 31%	5970
April	1st to 10th	Day	21% 14% 3 7% 4 4 3 3 4 5% 32%	2400
	11th to 20th	Day	18% 11% 3 7% 5% 5% 4 3 5% 5% 34%	2374
	21st to end	Day	22% 11% 3 6% 5% 4 4 4 5% 5% 32%	2530
May	1st to 10th	Day	32% 11% 3 7% 4 4 4 3 5% 5% 22%	5971
	11th to 20th	Day	20% 8% 3 8% 5% 4 5% 4 6% 7% 29%	6318
	21st to end	Day	20% 8% 3 7% 4 5% 4 4 6% 7% 32%	6949
June	1st to 10th	Day	19% 7% 3 7% 5% 5% 6% 4 6% 8% 30%	2800
	11th to 20th	Day	20% 6% 2 7% 4 5% 4 4 6% 8% 33%	2800
	21st to end	Day	18% 9% 2 7% 5% 5% 5% 4 6% 8% 30%	2800
July	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 4 7% 9% 35%	6360
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 10% 36%	6360
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 40%	6926
August	1st to 10th	Day	18% 6% 2 7% 5% 5% 5% 4 6% 9% 33%	4536
	11th to 20th	Day	15% 6% 3 7% 5% 5% 6% 4 7% 9% 34%	3925
	21st to end	Day	14% 5% 2 5% 4 5% 5% 4 8% 9% 40%	4312
September	1st to 10th	Day	14% 6% 1 6% 4 3 4 4 6% 8% 44%	2400
	11th to 20th	Day	15% 5% 2 5% 3 3 4 4 5% 7% 48%	2265
	21st to end	Day	17% 7% 2 5% 4 3 5% 4 5% 8% 40%	2090
October	1st to 10th	Day	23% 8% 3 7% 4 5% 5% 3 4 5% 33%	2012
	11th to 20th	Day	17% 10% 4 6% 4 4 4 3 4 7% 38%	1875
	21st to end	Day	27% 10% 3 6% 4 4 5% 3 4 5% 29%	1881
November	1st to 10th	Day	15% 11% 3 6% 5% 4 3 3 5% 7% 39%	1761
	11th to 20th	Day	19% 12% 3 8% 4 4 4 3 5% 5% 34%	1800
	21st to end	Day	20% 13% 4 7% 5% 4 4 3 4 6% 30%	1651
December	1st to 10th	Day	19% 17% 5% 10% 5% 4 4 3 4 6% 23%	2600
	11th to 20th	Day	21% 15% 6% 9% 5% 3 3 3 4 4 27%	2986
	21st to end	Day	22% 17% 4 9% 3 3 3 2 4 5% 26%	3960
January	1st to 10th	Night	14% 14% 10% 16% 5% 4 4 3 4 4 23%	6349
	11th to 20th	Night	12% 16% 7% 17% 8% 6% 4 3 5% 5% 18%	6315
	21st to end	Night	17% 13% 5% 13% 6% 6% 5% 3 5% 5% 23%	6969
February	1st to 10th	Night	16% 16% 5% 11% 7% 5% 5% 4 4 4 23%	2600
	11th to 20th	Night	13% 13% 5% 12% 7% 5% 6% 3 5% 5% 24%	2348
	21st to end	Night	16% 15% 4 11% 5% 4 4 3 5% 5% 28%	1980
March	1st to 10th	Night	20% 11% 5% 10% 5% 5% 5% 4 4 5% 26%	5364
	11th to 20th	Night	18% 14% 3 7% 4 4 4 3 4 6% 32%	5268
	21st to end	Night	25% 15% 4 9% 4 4 3 2 3 4 28%	4962
April	1st to 10th	Night	23% 12% 3 7% 4 4 4 3 4 5% 30%	2000
	11th to 20th	Night	22% 12% 2 7% 4 3 3 3 5% 6% 33%	1975
	21st to end	Night	22% 11% 3 6% 4 3 4 3 4 5% 35%	1869
May	1st to 10th	Night	33% 10% 3 8% 5% 4 4 4 4 5% 21%	4012
	11th to 20th	Night	20% 10% 4 9% 6% 4 5% 3 5% 6% 28%	3575
	21st to end	Night	23% 9% 3 7% 5% 5% 4 4 5% 6% 30%	3926
June	1st to 10th	Night	21% 7% 2 6% 4 4 4 4 6% 8% 34%	1600
	11th to 20th	Night	21% 6% 3 4 4 3 4 4 6% 8% 38%	1600
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 6% 7% 39%	1600
July	1st to 10th	Night	13% 7% 2 7% 5% 5% 5% 5% 6% 9% 36%	3600
	11th to 20th	Night	19% 8% 4 7% 4 4 5% 4 5% 7% 33%	3600
	21st to end	Night	13% 6% 2 6% 4 5% 4 3 5% 7% 45%	3926
August	1st to 10th	Night	25% 7% 3 6% 4 4 3 3 5% 8% 33%	2586
	11th to 20th	Night	15% 7% 3 7% 4 4 5% 4 6% 7% 36%	3113
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	3586
September	1st to 10th	Night	16% 7% 3 5% 3 3 3 3 5% 6% 47%	2000
	11th to 20th	Night	16% 5% 1 4 4 3 4 3 4 6% 50%	2090
	21st to end	Night	18% 6% 2 5% 4 5% 4 4 5% 5% 43%	2090
October	1st to 10th	Night	23% 7% 3 8% 4 4 3 3 5% 5% 34%	2166
	11th to 20th	Night	18% 9% 2 7% 5% 4 4 4 5% 6% 37%	2304
	21st to end	Night	26% 10% 3 6% 5% 4 4 3 5% 6% 28%	2717
November	1st to 10th	Night	16% 11% 3 7% 5% 4 4 3 4 5% 38%	2537
	11th to 20th	Night	20% 11% 3 7% 5% 4 4 3 5% 6% 35%	2600
	21st to end	Night	18% 14% 4 8% 4 4 3 3 5% 7% 30%	2745
December	1st to 10th	Night	18% 20% 8% 10% 5% 4 4 3 5% 5% 18%	4580
	11th to 20th	Night	25% 15% 4 9% 4 3 4 3 4 3 26%	5208
	21st to end	Night	21% 18% 5% 8% 4 4 4 3 4 5% 24%	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	70% 4 7% 17% 3	3598
	11th to 20th	Day	66% 5% 7% 12% 8% 2	3600
	21st to end	Day	64% 4 9% 15% 8% 2	3983
February	1st to 10th	Day	63% 5% 10% 14% 7%	1800
	11th to 20th	Day	62% 5% 8% 16% 8% 1	1945
	21st to end	Day	61% 3 9% 15% 11% 1	1650
March	1st to 10th	Day	65% 3 9% 11% 8% 4	4479
	11th to 20th	Day	53% 4 15% 17% 7% 3	4671
	21st to end	Day	57% 4 6% 13% 17% 3	5970
April	1st to 10th	Day	56% 4 7% 20% 10% 2	2400
	11th to 20th	Day	53% 4 9% 19% 13% 1	2374
	21st to end	Day	55% 5% 9% 17% 12% 2	2530
May	1st to 10th	Day	66% 5% 8% 14% 7% 1	5982
	11th to 20th	Day	55% 5% 15% 16% 8% 1	6322
	21st to end	Day	52% 6% 11% 23% 8% 1	6949
June	1st to 10th	Day	52% 7% 14% 18% 9% 1	2800
	11th to 20th	Day	49% 6% 13% 20% 12% 1	2800
	21st to end	Day	52% 6% 12% 19% 9%	2800
July	1st to 10th	Day	46% 6% 13% 24% 11%	6290
	11th to 20th	Day	43% 7% 14% 24% 11% 1	6285
	21st to end	Day	43% 5% 13% 31% 8%	6728
August	1st to 10th	Day	48% 7% 15% 20% 10%	4522
	11th to 20th	Day	46% 6% 17% 24% 5% 1	3963
	21st to end	Day	39% 6% 16% 28% 10% 1	4312
September	1st to 10th	Day	40% 6% 13% 29% 12% 1	2400
	11th to 20th	Day	38% 4 11% 28% 19% 1	2265
	21st to end	Day	43% 5% 13% 25% 12% 1	2090
October	1st to 10th	Day	52% 5% 8% 23% 12% 1	3337
	11th to 20th	Day	45% 4 13% 23% 15% 1	3091
	21st to end	Day	43% 5% 12% 28% 11% 1	3081
November	1st to 10th	Day	46% 5% 14% 22% 12% 1	1761
	11th to 20th	Day	54% 4 10% 17% 14% 2	1800
	21st to end	Day	59% 4 15% 16% 5% 1	1651
December	1st to 10th	Day	67% 5% 12% 13% 3	2600
	11th to 20th	Day	65% 3 9% 17% 6% 1	2986
	21st to end	Day	62% 3 7% 15% 10% 2	3960
January	1st to 10th	Night	69% 3 12% 12% 5%	6349
	11th to 20th	Night	70% 6% 8% 11% 5% 1	6360
	21st to end	Night	65% 4 9% 10% 10% 2	6969
February	1st to 10th	Night	66% 4 9% 14% 6% 1	2600
	11th to 20th	Night	62% 4 10% 14% 9% 1	2350
	21st to end	Night	59% 4 11% 17% 7% 2	1980
March	1st to 10th	Night	60% 4 10% 14% 10% 1	5374
	11th to 20th	Night	53% 5% 17% 15% 8% 2	5269
	21st to end	Night	62% 3 5% 13% 15% 2	4962
April	1st to 10th	Night	58% 4 9% 18% 10% 1	2000
	11th to 20th	Night	54% 5% 8% 19% 12% 1	1975
	21st to end	Night	53% 4 9% 18% 13% 3	1869
May	1st to 10th	Night	66% 5% 8% 13% 7% 1	4018
	11th to 20th	Night	57% 6% 12% 17% 7% 1	3576
	21st to end	Night	56% 5% 11% 17% 10% 1	3927
June	1st to 10th	Night	49% 6% 13% 20% 11% 1	1600
	11th to 20th	Night	45% 6% 16% 21% 11% 1	1600
	21st to end	Night	46% 6% 13% 24% 11% 1	1600
July	1st to 10th	Night	44% 6% 16% 22% 11% 1	3560
	11th to 20th	Night	51% 6% 11% 20% 11%	3552
	21st to end	Night	40% 6% 13% 31% 10% 1	3809
August	1st to 10th	Night	51% 5% 13% 21% 9% 1	2576
	11th to 20th	Night	45% 7% 17% 21% 9%	3141
	21st to end	Night	38% 6% 16% 28% 11% 1	3586
September	1st to 10th	Night	40% 5% 13% 28% 14% 1	2000
	11th to 20th	Night	36% 4 11% 30% 19% 1	2090
	21st to end	Night	43% 5% 11% 25% 15% 2	2090
October	1st to 10th	Night	55% 5% 11% 20% 7% 1	3608
	11th to 20th	Night	44% 4 12% 22% 16% 2	3827
	21st to end	Night	48% 5% 11% 28% 7% 1	4467
November	1st to 10th	Night	51% 5% 10% 20% 12% 2	2537
	11th to 20th	Night	52% 4 11% 18% 12% 3	2600
	21st to end	Night	56% 5% 14% 18% 7%	2745
December	1st to 10th	Night	72% 4 10% 11% 2	4580
	11th to 20th	Night	66% 3 9% 12% 9%	5208
	21st to end	Night	65% 4 8% 14% 6% 3	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% 23% 26% 15% 3 1	200
	11th to 20th	Day	38% 23% 30% 7% 2 1	200
	21st to end	Day	28% 24% 32% 11% 4 1	225
February	1st to 10th	Day	38% 33% 23% 6% 1	300
	11th to 20th	Day	30% 32% 26% 10% 2	484
	21st to end	Day	33% 22% 31% 13% 1	414
March	1st to 10th	Day	31% 24% 28% 15% 2	500
	11th to 20th	Day	32% 26% 26% 13% 3 1	500
	21st to end	Day	32% 26% 24% 11% 5% 2	550
April	1st to 10th	Day	39% 19% 24% 12% 5% 1	500
	11th to 20th	Day	37% 21% 23% 12% 6% 2	492
	21st to end	Day	31% 21% 29% 12% 5% 2	500
May	1st to 10th	Day	34% 20% 24% 13% 7% 2	503
	11th to 20th	Day	25% 16% 34% 20% 5% 1	527
	21st to end	Day	22% 14% 33% 20% 9% 2	573
June	1st to 10th	Day	21% 16% 33% 20% 8% 2	530
	11th to 20th	Day	24% 11% 33% 22% 9% 2	530
	21st to end	Day	23% 15% 31% 21% 9% 2	530
July	1st to 10th	Day	16% 12% 34% 25% 13% 2	525
	11th to 20th	Day	14% 8% 36% 30% 11% 2	524
	21st to end	Day	18% 7% 39% 26% 8% 2	576
August	1st to 10th	Day	16% 9% 26% 31% 15% 3	526
	11th to 20th	Day	17% 9% 28% 26% 14% 6%	519
	21st to end	Day	15% 12% 28% 26% 12% 5%	583
September	1st to 10th	Day	16% 13% 25% 25% 15% 6%	530
	11th to 20th	Day	14% 12% 26% 19% 19% 10%	522
	21st to end	Day	19% 10% 30% 22% 12% 6%	490
October	1st to 10th	Day	30% 11% 25% 17% 14% 3	490
	11th to 20th	Day	26% 17% 26% 21% 9% 1	476
	21st to end	Day	36% 15% 26% 19% 4	429
November	1st to 10th	Day	28% 20% 25% 18% 9% 1	395
	11th to 20th	Day	31% 21% 24% 19% 4 1	400
	21st to end	Day	36% 22% 27% 12% 3	251
December	1st to 10th	Day	37% 20% 30% 12% 3 1	200
	11th to 20th	Day	36% 28% 27% 7% 4	200
	21st to end	Day	35% 22% 25% 15% 2	220
January	1st to 10th	Night	26% 25% 31% 17% 2	800
	11th to 20th	Night	29% 21% 28% 19% 2 1	800
	21st to end	Night	22% 22% 33% 20% 4	880
February	1st to 10th	Night	27% 23% 35% 14% 2	800
	11th to 20th	Night	25% 23% 33% 17% 2	783
	21st to end	Night	25% 24% 31% 18% 3	660
March	1st to 10th	Night	25% 22% 31% 20% 3	800
	11th to 20th	Night	28% 20% 31% 17% 4	800
	21st to end	Night	29% 20% 26% 18% 7%	880
April	1st to 10th	Night	31% 20% 26% 20% 4	800
	11th to 20th	Night	29% 19% 26% 18% 7%	791
	21st to end	Night	30% 16% 27% 22% 5%	669
May	1st to 10th	Night	30% 14% 26% 22% 8%	584
	11th to 20th	Night	22% 12% 32% 28% 6%	394
	21st to end	Night	20% 9% 25% 34% 12%	433
June	1st to 10th	Night	23% 9% 26% 31% 11% 1	400
	11th to 20th	Night	23% 6% 23% 37% 11%	400
	21st to end	Night	18% 8% 24% 40% 10% 1	400
July	1st to 10th	Night	18% 5% 21% 43% 12% 1	390
	11th to 20th	Night	18% 4 22% 40% 15% 1	388
	21st to end	Night	15% 4 23% 45% 12% 2	438
August	1st to 10th	Night	17% 4 20% 39% 19%	398
	11th to 20th	Night	17% 5% 19% 36% 19% 3	730
	21st to end	Night	18% 6% 21% 34% 20% 1	880
September	1st to 10th	Night	19% 7% 22% 35% 16% 2	800
	11th to 20th	Night	19% 7% 18% 30% 21% 4	793
	21st to end	Night	20% 8% 26% 29% 15% 2	760
October	1st to 10th	Night	27% 11% 20% 26% 14% 1	760
	11th to 20th	Night	24% 13% 25% 29% 9%	760
	21st to end	Night	32% 13% 28% 22% 5%	836
November	1st to 10th	Night	25% 18% 28% 23% 6% 1	780
	11th to 20th	Night	26% 17% 29% 20% 6% 2	800
	21st to end	Night	26% 20% 31% 17% 5% 1	800
December	1st to 10th	Night	33% 21% 27% 16% 4	800
	11th to 20th	Night	30% 22% 27% 18% 3	800
	21st to end	Night	30% 20% 31% 17% 3	880

Page generated at 2025-09-16 01:49:12. Version ac07

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