South Tamworth Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Tamworth Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	16% 8% 3 7% 5% 4 5% 4 6% 7% 36%	101743
	Night	17% 8% 3 7% 5% 4 5% 4 5% 6% 37%	98366
Transparency	Day	45% 6% 12% 22% 13% 2	105268
	Night	45% 6% 12% 22% 13% 2	102930
Seeing	Day	23% 15% 29% 21% 9% 3	15014
	Night	21% 11% 26% 30% 10% 1	23937

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% 9% 2 6% 5% 5% 5% 5% 6% 7% 38%	2517
	11th to 20th	Day	15% 8% 3 8% 6% 5% 6% 3 6% 6% 33%	2520
	21st to end	Day	15% 11% 3 7% 6% 4 4 4 6% 7% 33%	2772
February	1st to 10th	Day	13% 10% 3 6% 6% 6% 5% 4 5% 7% 34%	1677
	11th to 20th	Day	11% 7% 3 9% 6% 5% 5% 4 6% 6% 37%	1848
	21st to end	Day	15% 11% 4 7% 5% 5% 5% 5% 5% 5% 34%	1570
March	1st to 10th	Day	19% 14% 3 9% 5% 4 4 4 5% 4 28%	3116
	11th to 20th	Day	14% 9% 2 7% 5% 5% 6% 4 6% 7% 35%	3337
	21st to end	Day	19% 10% 3 7% 5% 5% 4 3 5% 7% 33%	4033
April	1st to 10th	Day	19% 10% 3 6% 5% 3 4 3 5% 6% 36%	2280
	11th to 20th	Day	16% 7% 2 6% 5% 4 5% 4 6% 7% 38%	2295
	21st to end	Day	21% 9% 3 7% 6% 4 4 3 4 5% 34%	2470
May	1st to 10th	Day	22% 12% 4 10% 6% 5% 4 4 5% 5% 25%	4106
	11th to 20th	Day	18% 9% 3 8% 6% 5% 5% 4 5% 7% 30%	4266
	21st to end	Day	14% 6% 2 6% 5% 4 5% 5% 7% 8% 38%	4837
June	1st to 10th	Day	20% 8% 2 7% 5% 4 5% 4 6% 7% 30%	2660
	11th to 20th	Day	16% 7% 2 6% 5% 6% 4 4 6% 7% 36%	2660
	21st to end	Day	19% 7% 3 6% 5% 5% 5% 4 6% 8% 31%	2660
July	1st to 10th	Day	13% 6% 3 6% 5% 4 5% 5% 7% 10% 35%	4440
	11th to 20th	Day	11% 6% 2 6% 4 4 6% 5% 9% 11% 37%	4440
	21st to end	Day	18% 7% 2 6% 5% 4 5% 4 6% 8% 36%	4814
August	1st to 10th	Day	14% 6% 3 7% 5% 5% 5% 5% 6% 8% 35%	4238
	11th to 20th	Day	17% 8% 3 8% 4 4 5% 5% 6% 7% 32%	4045
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 6% 10% 45%	4194
September	1st to 10th	Day	12% 4 2 5% 4 4 4 4 7% 8% 47%	2280
	11th to 20th	Day	13% 5% 2 4 3 4 4 3 3 7% 51%	2094
	21st to end	Day	16% 5% 1 5% 4 4 6% 3 5% 7% 44%	2090
October	1st to 10th	Day	21% 7% 3 6% 4 4 4 3 5% 6% 37%	2090
	11th to 20th	Day	16% 7% 2 5% 5% 5% 5% 3 5% 6% 41%	1815
	21st to end	Day	23% 8% 2 7% 4 4 3 4 5% 5% 35%	1881
November	1st to 10th	Day	13% 7% 2 5% 4 3 3 4 6% 7% 45%	1761
	11th to 20th	Day	18% 5% 2 5% 5% 4 5% 4 6% 7% 42%	1800
	21st to end	Day	20% 8% 2 5% 4 4 4 4 5% 6% 38%	1755
December	1st to 10th	Day	19% 11% 3 7% 4 5% 6% 5% 5% 7% 30%	1600
	11th to 20th	Day	21% 8% 2 5% 4 4 3 4 4 6% 39%	1986
	21st to end	Day	22% 12% 3 6% 4 4 5% 4 6% 5% 30%	2796
January	1st to 10th	Night	16% 8% 2 5% 4 4 5% 4 5% 7% 40%	4429
	11th to 20th	Night	12% 9% 3 10% 6% 5% 6% 5% 6% 6% 30%	4440
	21st to end	Night	18% 11% 3 9% 5% 4 5% 4 5% 6% 29%	4884
February	1st to 10th	Night	12% 9% 4 7% 5% 5% 5% 4 6% 7% 34%	2496
	11th to 20th	Night	10% 9% 3 7% 6% 4 5% 5% 6% 7% 39%	2218
	21st to end	Night	12% 10% 3 6% 5% 4 5% 4 6% 7% 39%	1884
March	1st to 10th	Night	24% 11% 3 6% 4 4 4 3 5% 5% 31%	3724
	11th to 20th	Night	11% 10% 4 9% 8% 6% 5% 4 6% 6% 32%	3621
	21st to end	Night	22% 10% 3 7% 4 3 4 3 5% 6% 32%	3594
April	1st to 10th	Night	18% 10% 3 6% 5% 4 5% 3 4 5% 37%	1900
	11th to 20th	Night	17% 7% 2 7% 6% 5% 4 3 5% 7% 36%	1833
	21st to end	Night	21% 8% 2 5% 4 4 4 3 5% 6% 37%	1710
May	1st to 10th	Night	25% 11% 4 7% 4 4 4 4 5% 6% 25%	2834
	11th to 20th	Night	17% 10% 4 8% 5% 5% 6% 4 7% 7% 27%	2655
	21st to end	Night	16% 6% 2 6% 4 4 5% 3 6% 7% 41%	2738
June	1st to 10th	Night	20% 7% 2 7% 5% 4 5% 4 6% 7% 34%	1520
	11th to 20th	Night	17% 7% 2 5% 4 4 5% 4 5% 8% 39%	1520
	21st to end	Night	18% 6% 2 6% 5% 4 5% 4 7% 7% 36%	1520
July	1st to 10th	Night	13% 5% 2 7% 5% 5% 6% 4 8% 9% 37%	2520
	11th to 20th	Night	15% 6% 2 6% 5% 4 4 4 5% 7% 43%	2520
	21st to end	Night	16% 6% 2 5% 4 4 5% 4 6% 7% 41%	2739
August	1st to 10th	Night	22% 8% 2 8% 5% 4 4 3 5% 6% 33%	2658
	11th to 20th	Night	17% 7% 3 6% 4 4 5% 4 5% 7% 37%	2782
	21st to end	Night	9% 5% 2 4 4 3 4 4 7% 9% 48%	3444
September	1st to 10th	Night	12% 5% 1 4 3 3 3 3 6% 7% 51%	1900
	11th to 20th	Night	14% 5% 1 4 4 4 3 3 4 6% 51%	2085
	21st to end	Night	16% 6% 2 5% 3 4 4 3 5% 7% 45%	2090
October	1st to 10th	Night	20% 6% 2 7% 4 4 4 4 6% 5% 38%	2090
	11th to 20th	Night	15% 6% 2 6% 4 5% 5% 4 6% 8% 39%	2360
	21st to end	Night	22% 8% 3 5% 4 4 5% 3 5% 6% 36%	2717
November	1st to 10th	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	2537
	11th to 20th	Night	15% 6% 2 7% 4 4 4 4 5% 6% 43%	2600
	21st to end	Night	16% 8% 3 6% 5% 4 4 4 5% 6% 41%	2643
December	1st to 10th	Night	18% 10% 4 7% 5% 5% 5% 3 6% 6% 33%	2800
	11th to 20th	Night	21% 9% 2 5% 4 4 4 4 5% 6% 37%	3428
	21st to end	Night	21% 11% 3 7% 4 4 4 4 4 4 32%	4933

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	43% 4 11% 30% 11% 1	2518
	11th to 20th	Day	49% 4 14% 24% 8% 2	2520
	21st to end	Day	49% 4 14% 21% 11% 1	2772
February	1st to 10th	Day	49% 4 15% 19% 10% 2	1677
	11th to 20th	Day	46% 6% 11% 19% 14% 4	1857
	21st to end	Day	50% 4 12% 18% 13% 3	1570
March	1st to 10th	Day	59% 4 9% 13% 12% 3	3119
	11th to 20th	Day	46% 4 14% 18% 13% 6%	3337
	21st to end	Day	50% 4 6% 16% 19% 5%	4033
April	1st to 10th	Day	49% 4 9% 20% 14% 4	2280
	11th to 20th	Day	45% 6% 12% 21% 15% 1	2295
	21st to end	Day	53% 5% 7% 18% 14% 3	2470
May	1st to 10th	Day	59% 5% 10% 17% 8% 1	4120
	11th to 20th	Day	52% 6% 15% 17% 9% 2	4270
	21st to end	Day	39% 8% 13% 24% 15% 1	4837
June	1st to 10th	Day	50% 6% 12% 22% 9% 1	2660
	11th to 20th	Day	44% 6% 12% 21% 14% 3	2660
	21st to end	Day	49% 8% 12% 18% 11% 1	2660
July	1st to 10th	Day	41% 7% 13% 24% 14%	4370
	11th to 20th	Day	36% 8% 18% 27% 10%	4365
	21st to end	Day	44% 7% 13% 22% 15% 1	4661
August	1st to 10th	Day	44% 8% 15% 23% 10%	4224
	11th to 20th	Day	47% 7% 16% 23% 7%	4084
	21st to end	Day	32% 6% 17% 27% 17% 1	4194
September	1st to 10th	Day	33% 7% 13% 30% 15% 1	2280
	11th to 20th	Day	34% 3 9% 32% 20% 2	2094
	21st to end	Day	39% 6% 11% 25% 17% 2	2090
October	1st to 10th	Day	45% 7% 10% 21% 16% 1	3480
	11th to 20th	Day	38% 4 13% 27% 15% 3	2992
	21st to end	Day	37% 3 11% 27% 17% 4	3081
November	1st to 10th	Day	37% 5% 15% 26% 15% 2	1761
	11th to 20th	Day	40% 4 12% 20% 19% 3	1800
	21st to end	Day	47% 4 16% 21% 11% 1	1755
December	1st to 10th	Day	52% 5% 13% 21% 8% 1	1600
	11th to 20th	Day	47% 5% 9% 21% 17% 2	1986
	21st to end	Day	56% 4 10% 19% 9% 2	2796
January	1st to 10th	Night	42% 4 14% 26% 10% 3	4429
	11th to 20th	Night	48% 5% 14% 22% 9% 2	4440
	21st to end	Night	53% 5% 11% 19% 10% 2	4884
February	1st to 10th	Night	47% 5% 13% 19% 13% 2	2496
	11th to 20th	Night	43% 6% 10% 23% 15% 3	2220
	21st to end	Night	44% 5% 12% 22% 12% 4	1884
March	1st to 10th	Night	55% 4 10% 18% 11% 2	3734
	11th to 20th	Night	50% 6% 10% 18% 13% 3	3622
	21st to end	Night	51% 4 6% 15% 19% 5%	3594
April	1st to 10th	Night	49% 4 9% 20% 15% 3	1900
	11th to 20th	Night	47% 5% 8% 23% 15% 1	1833
	21st to end	Night	47% 4 12% 19% 15% 3	1710
May	1st to 10th	Night	59% 5% 10% 16% 8% 1	2840
	11th to 20th	Night	55% 6% 13% 16% 8% 2	2656
	21st to end	Night	40% 7% 17% 21% 13% 2	2739
June	1st to 10th	Night	48% 7% 13% 20% 12%	1520
	11th to 20th	Night	44% 7% 15% 19% 13% 2	1520
	21st to end	Night	45% 8% 14% 22% 10% 1	1520
July	1st to 10th	Night	39% 9% 18% 20% 14%	2480
	11th to 20th	Night	40% 6% 15% 24% 15%	2472
	21st to end	Night	41% 7% 12% 29% 11% 1	2651
August	1st to 10th	Night	52% 6% 12% 21% 9%	2648
	11th to 20th	Night	45% 8% 16% 21% 11%	2809
	21st to end	Night	29% 8% 17% 29% 15% 1	3444
September	1st to 10th	Night	31% 7% 14% 31% 17% 1	1900
	11th to 20th	Night	34% 5% 10% 29% 20% 2	2085
	21st to end	Night	38% 5% 11% 30% 14% 2	2090
October	1st to 10th	Night	43% 9% 14% 22% 12% 1	3480
	11th to 20th	Night	34% 5% 12% 28% 17% 4	3922
	21st to end	Night	40% 3 11% 28% 16% 2	4467
November	1st to 10th	Night	39% 6% 12% 26% 15% 2	2537
	11th to 20th	Night	41% 5% 10% 25% 17% 2	2600
	21st to end	Night	43% 5% 15% 25% 11% 1	2643
December	1st to 10th	Night	52% 4 12% 23% 8% 1	2800
	11th to 20th	Night	47% 5% 12% 19% 16% 2	3428
	21st to end	Night	56% 4 9% 21% 10% 1	4933

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	27% 18% 29% 19% 7%	180
	11th to 20th	Day	30% 22% 25% 18% 3 2	180
	21st to end	Day	18% 21% 34% 21% 6% 1	198
February	1st to 10th	Day	27% 23% 31% 16% 3	299
	11th to 20th	Day	26% 22% 32% 18% 2	456
	21st to end	Day	30% 17% 29% 21% 4	382
March	1st to 10th	Day	29% 15% 31% 21% 3	460
	11th to 20th	Day	28% 23% 29% 13% 6% 1	460
	21st to end	Day	27% 19% 30% 15% 6% 3	506
April	1st to 10th	Day	32% 17% 27% 16% 7% 2	460
	11th to 20th	Day	30% 20% 26% 15% 7% 2	452
	21st to end	Day	28% 21% 30% 12% 6% 2	460
May	1st to 10th	Day	31% 19% 29% 15% 5% 2	463
	11th to 20th	Day	21% 18% 33% 19% 7% 2	487
	21st to end	Day	21% 14% 34% 22% 7% 2	529
June	1st to 10th	Day	22% 14% 34% 19% 7% 3	490
	11th to 20th	Day	18% 16% 32% 23% 9% 2	490
	21st to end	Day	22% 15% 33% 17% 11% 2	490
July	1st to 10th	Day	18% 9% 32% 24% 14% 3	485
	11th to 20th	Day	14% 7% 36% 28% 12% 3	484
	21st to end	Day	16% 9% 35% 27% 11% 2	532
August	1st to 10th	Day	12% 12% 29% 27% 16% 4	486
	11th to 20th	Day	20% 9% 27% 23% 16% 5%	479
	21st to end	Day	14% 9% 28% 29% 14% 6%	539
September	1st to 10th	Day	16% 10% 26% 24% 18% 6%	490
	11th to 20th	Day	19% 11% 23% 22% 15% 10%	490
	21st to end	Day	16% 12% 28% 25% 13% 6%	490
October	1st to 10th	Day	26% 15% 21% 20% 14% 5%	490
	11th to 20th	Day	21% 17% 24% 22% 13% 3	424
	21st to end	Day	33% 13% 25% 23% 6% 1	429
November	1st to 10th	Day	23% 16% 26% 26% 7% 2	395
	11th to 20th	Day	27% 18% 27% 20% 8% 1	400
	21st to end	Day	33% 16% 28% 17% 5% 1	355
December	1st to 10th	Day	25% 26% 25% 16% 8% 1	200
	11th to 20th	Day	32% 20% 31% 14% 4	200
	21st to end	Day	30% 18% 30% 17% 3 1	204
January	1st to 10th	Night	21% 12% 34% 29% 4	760
	11th to 20th	Night	24% 14% 28% 29% 5%	760
	21st to end	Night	18% 17% 31% 27% 6%	836
February	1st to 10th	Night	20% 15% 34% 29% 2	760
	11th to 20th	Night	19% 18% 38% 21% 4	743
	21st to end	Night	20% 16% 32% 28% 4	628
March	1st to 10th	Night	26% 13% 31% 26% 5%	760
	11th to 20th	Night	23% 15% 30% 26% 6%	760
	21st to end	Night	24% 14% 28% 25% 9% 1	836
April	1st to 10th	Night	25% 13% 28% 28% 5%	760
	11th to 20th	Night	22% 15% 29% 27% 7%	709
	21st to end	Night	27% 13% 24% 28% 7%	570
May	1st to 10th	Night	28% 8% 26% 28% 9% 1	570
	11th to 20th	Night	21% 10% 30% 28% 11%	469
	21st to end	Night	21% 7% 21% 36% 14% 1	411
June	1st to 10th	Night	21% 7% 25% 36% 10% 1	380
	11th to 20th	Night	19% 6% 23% 36% 14% 1	380
	21st to end	Night	21% 5% 23% 37% 12% 1	380
July	1st to 10th	Night	17% 4 19% 43% 17%	370
	11th to 20th	Night	16% 3 20% 40% 20% 2	368
	21st to end	Night	15% 4 17% 46% 18% 1	416
August	1st to 10th	Night	17% 4 16% 41% 22% 1	465
	11th to 20th	Night	17% 6% 24% 32% 20% 2	562
	21st to end	Night	17% 4 18% 37% 21% 4	817
September	1st to 10th	Night	14% 6% 23% 34% 20% 2	760
	11th to 20th	Night	18% 7% 18% 30% 23% 5%	760
	21st to end	Night	18% 8% 23% 31% 17% 3	760
October	1st to 10th	Night	23% 10% 19% 30% 17% 1	760
	11th to 20th	Night	21% 11% 24% 30% 13% 1	760
	21st to end	Night	29% 13% 23% 27% 8%	836
November	1st to 10th	Night	19% 12% 28% 30% 9% 2	780
	11th to 20th	Night	21% 15% 29% 26% 7% 1	800
	21st to end	Night	23% 18% 24% 28% 6%	800
December	1st to 10th	Night	26% 14% 29% 25% 6% 1	800
	11th to 20th	Night	26% 15% 27% 28% 4	800
	21st to end	Night	26% 15% 28% 28% 3	851

Page generated at 2024-12-21 04:13:53. Version ac07

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