Tmakwa Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tmakwa Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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% 13% 4 10% 6% 5% 5% 4 5% 6% 26%	101270
	Night	16% 14% 5% 11% 6% 5% 4 3 5% 5% 25%	97551
Transparency	Day	54% 9% 11% 16% 8% 1	101028
	Night	56% 10% 11% 15% 7% 1	97413
Seeing	Day	26% 19% 28% 18% 7% 2	14801
	Night	24% 16% 25% 25% 9% 1	23641

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	12% 17% 8% 21% 7% 5% 4 3 4 3 16%	2517
	11th to 20th	Day	8% 13% 6% 19% 14% 7% 5% 3 4 5% 17%	2520
	21st to end	Day	11% 18% 8% 17% 7% 5% 5% 4 4 3 18%	2772
February	1st to 10th	Day	13% 15% 7% 13% 10% 6% 4 2 5% 4 20%	1650
	11th to 20th	Day	9% 14% 8% 15% 10% 7% 6% 4 4 4 18%	1848
	21st to end	Day	10% 16% 6% 14% 8% 6% 4 3 5% 5% 22%	1570
March	1st to 10th	Day	16% 17% 6% 11% 7% 5% 5% 3 5% 4 21%	3116
	11th to 20th	Day	11% 18% 11% 14% 6% 4 4 2 3 4 23%	3310
	21st to end	Day	18% 14% 5% 12% 7% 3 4 3 3 6% 25%	4065
April	1st to 10th	Day	16% 20% 5% 10% 4 4 3 3 3 4 26%	2280
	11th to 20th	Day	14% 17% 5% 9% 4 4 4 4 4 5% 29%	2291
	21st to end	Day	20% 17% 3 9% 5% 3 4 4 5% 4 25%	2470
May	1st to 10th	Day	25% 16% 4 8% 5% 4 5% 3 3 4 23%	4106
	11th to 20th	Day	17% 12% 4 9% 6% 5% 6% 3 5% 7% 25%	4331
	21st to end	Day	13% 9% 3 8% 5% 5% 5% 5% 7% 9% 32%	4837
June	1st to 10th	Day	26% 11% 3 8% 5% 4 5% 3 6% 6% 23%	2660
	11th to 20th	Day	19% 8% 3 7% 5% 4 5% 4 6% 8% 31%	2660
	21st to end	Day	21% 11% 3 9% 6% 5% 5% 5% 5% 6% 24%	2660
July	1st to 10th	Day	15% 8% 2 7% 5% 6% 6% 5% 8% 10% 27%	4440
	11th to 20th	Day	11% 8% 3 8% 6% 6% 7% 5% 9% 9% 27%	4440
	21st to end	Day	17% 8% 3 8% 6% 5% 5% 4 6% 7% 30%	4814
August	1st to 10th	Day	17% 11% 3 9% 6% 5% 6% 4 5% 7% 26%	4280
	11th to 20th	Day	17% 9% 3 9% 7% 5% 6% 5% 7% 9% 23%	4045
	21st to end	Day	15% 8% 2 7% 5% 5% 5% 5% 7% 9% 34%	4190
September	1st to 10th	Day	15% 7% 2 6% 4 4 4 4 4 8% 41%	2280
	11th to 20th	Day	16% 8% 2 5% 3 4 4 3 4 6% 45%	2106
	21st to end	Day	15% 11% 2 7% 4 5% 4 3 6% 8% 36%	2090
October	1st to 10th	Day	21% 12% 4 6% 4 5% 4 3 5% 7% 29%	2090
	11th to 20th	Day	14% 16% 4 7% 4 4 4 3 5% 5% 32%	1798
	21st to end	Day	19% 20% 4 7% 4 5% 4 3 4 5% 25%	1825
November	1st to 10th	Day	14% 17% 4 9% 4 3 3 4 6% 6% 30%	1671
	11th to 20th	Day	14% 16% 7% 12% 7% 5% 4 4 5% 6% 22%	1710
	21st to end	Day	14% 16% 6% 14% 7% 4 4 4 5% 5% 22%	1630
December	1st to 10th	Day	14% 19% 7% 15% 8% 4 4 3 3 4 18%	1520
	11th to 20th	Day	12% 21% 8% 13% 7% 4 3 3 3 5% 22%	1906
	21st to end	Day	17% 18% 5% 12% 8% 6% 5% 4 5% 4 15%	2772
January	1st to 10th	Night	10% 18% 8% 21% 9% 6% 5% 3 4 4 14%	4429
	11th to 20th	Night	9% 16% 9% 20% 15% 6% 5% 3 3 3 11%	4440
	21st to end	Night	14% 18% 7% 15% 9% 7% 4 3 4 3 15%	4884
February	1st to 10th	Night	11% 15% 7% 17% 10% 7% 5% 3 4 5% 17%	2525
	11th to 20th	Night	9% 14% 7% 18% 10% 8% 6% 3 4 3 18%	2218
	21st to end	Night	8% 17% 6% 13% 9% 6% 5% 3 5% 5% 24%	1884
March	1st to 10th	Night	18% 15% 5% 10% 7% 7% 5% 3 4 5% 23%	3724
	11th to 20th	Night	12% 21% 9% 12% 6% 4 4 3 4 4 21%	3647
	21st to end	Night	18% 17% 6% 11% 7% 4 3 2 3 4 24%	3565
April	1st to 10th	Night	18% 19% 5% 9% 5% 5% 3 3 4 6% 24%	1900
	11th to 20th	Night	17% 16% 4 7% 6% 5% 4 4 4 5% 28%	1838
	21st to end	Night	19% 14% 4 9% 4 4 4 3 5% 6% 29%	1710
May	1st to 10th	Night	25% 14% 4 7% 4 4 4 3 5% 6% 24%	2834
	11th to 20th	Night	18% 12% 3 9% 5% 5% 5% 4 5% 6% 28%	2591
	21st to end	Night	15% 7% 3 7% 4 4 5% 4 6% 9% 36%	2738
June	1st to 10th	Night	28% 10% 3 6% 4 4 4 3 4 8% 26%	1520
	11th to 20th	Night	19% 7% 2 7% 5% 6% 4 4 5% 7% 33%	1520
	21st to end	Night	21% 9% 2 7% 5% 5% 4 6% 6% 6% 29%	1520
July	1st to 10th	Night	16% 8% 3 8% 5% 6% 5% 5% 6% 8% 31%	2520
	11th to 20th	Night	18% 10% 3 8% 4 4 5% 3 6% 6% 32%	2520
	21st to end	Night	15% 8% 3 8% 6% 5% 5% 4 6% 7% 33%	2739
August	1st to 10th	Night	23% 11% 4 7% 4 4 4 4 4 6% 29%	2616
	11th to 20th	Night	18% 9% 3 8% 5% 4 6% 4 6% 7% 29%	2782
	21st to end	Night	16% 11% 2 5% 4 4 4 3 5% 7% 38%	3462
September	1st to 10th	Night	18% 7% 2 5% 4 2 3 3 5% 6% 44%	1900
	11th to 20th	Night	17% 8% 2 5% 3 3 3 2 5% 6% 46%	2072
	21st to end	Night	18% 8% 2 5% 4 4 5% 4 6% 7% 39%	2090
October	1st to 10th	Night	20% 12% 3 6% 5% 4 4 4 5% 6% 30%	2090
	11th to 20th	Night	17% 16% 3 7% 5% 4 4 3 5% 5% 30%	2379
	21st to end	Night	20% 18% 4 7% 5% 5% 4 4 4 5% 22%	2637
November	1st to 10th	Night	17% 17% 5% 10% 4 4 4 2 4 5% 28%	2407
	11th to 20th	Night	13% 17% 6% 13% 6% 4 3 4 4 6% 24%	2470
	21st to end	Night	14% 17% 8% 15% 8% 5% 3 3 4 5% 19%	2548
December	1st to 10th	Night	16% 20% 9% 15% 7% 5% 4 3 4 3 13%	2660
	11th to 20th	Night	14% 20% 8% 17% 7% 4 4 4 4 4 15%	3288
	21st to end	Night	18% 17% 6% 18% 7% 5% 4 3 4 4 16%	4884

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	61% 15% 9% 12% 3	2518
	11th to 20th	Day	58% 18% 9% 10% 4 1	2520
	21st to end	Day	62% 12% 9% 10% 5% 1	2772
February	1st to 10th	Day	66% 7% 7% 12% 6% 2	1650
	11th to 20th	Day	63% 10% 10% 10% 6% 2	1857
	21st to end	Day	61% 7% 9% 12% 8% 2	1570
March	1st to 10th	Day	62% 10% 8% 9% 9% 2	3119
	11th to 20th	Day	54% 16% 9% 9% 9% 4	3310
	21st to end	Day	55% 10% 7% 13% 14% 2	4065
April	1st to 10th	Day	61% 5% 8% 14% 9% 2	2280
	11th to 20th	Day	53% 8% 10% 17% 10% 1	2291
	21st to end	Day	60% 6% 8% 15% 9% 2	2470
May	1st to 10th	Day	62% 8% 8% 16% 5% 1	4120
	11th to 20th	Day	55% 11% 14% 12% 7% 1	4335
	21st to end	Day	42% 11% 14% 23% 9% 1	4837
June	1st to 10th	Day	60% 6% 11% 17% 6%	2660
	11th to 20th	Day	49% 8% 11% 19% 12% 1	2660
	21st to end	Day	58% 8% 10% 15% 7% 1	2660
July	1st to 10th	Day	47% 9% 15% 20% 8%	4370
	11th to 20th	Day	45% 10% 17% 24% 4	4365
	21st to end	Day	49% 7% 12% 24% 7%	4661
August	1st to 10th	Day	55% 8% 14% 17% 6%	4266
	11th to 20th	Day	54% 9% 17% 15% 4	4084
	21st to end	Day	42% 10% 16% 17% 11% 3	4190
September	1st to 10th	Day	40% 8% 13% 27% 12% 1	2280
	11th to 20th	Day	39% 6% 10% 29% 14% 2	2106
	21st to end	Day	44% 9% 13% 22% 11% 1	2090
October	1st to 10th	Day	55% 6% 10% 18% 10% 1	2090
	11th to 20th	Day	51% 9% 13% 20% 7% 1	1798
	21st to end	Day	61% 7% 10% 12% 8% 2	1825
November	1st to 10th	Day	54% 7% 11% 15% 11% 1	1671
	11th to 20th	Day	59% 10% 9% 10% 10% 2	1710
	21st to end	Day	62% 8% 13% 13% 3	1630
December	1st to 10th	Day	69% 7% 8% 11% 4 1	1520
	11th to 20th	Day	63% 7% 7% 11% 11% 1	1906
	21st to end	Day	64% 13% 9% 9% 6%	2772
January	1st to 10th	Night	61% 15% 12% 9% 3	4429
	11th to 20th	Night	66% 15% 8% 8% 3	4440
	21st to end	Night	66% 13% 8% 8% 4 1	4884
February	1st to 10th	Night	66% 9% 8% 9% 6% 2	2525
	11th to 20th	Night	65% 9% 8% 11% 7% 1	2220
	21st to end	Night	56% 10% 10% 15% 7% 2	1884
March	1st to 10th	Night	58% 10% 11% 13% 7% 1	3734
	11th to 20th	Night	58% 13% 9% 11% 8% 1	3648
	21st to end	Night	57% 9% 8% 11% 13% 2	3565
April	1st to 10th	Night	60% 8% 7% 15% 9% 1	1900
	11th to 20th	Night	55% 8% 8% 19% 10%	1838
	21st to end	Night	55% 7% 9% 14% 12% 2	1710
May	1st to 10th	Night	59% 8% 10% 16% 6% 1	2840
	11th to 20th	Night	53% 12% 11% 15% 7% 1	2592
	21st to end	Night	40% 13% 16% 18% 12% 1	2739
June	1st to 10th	Night	56% 8% 11% 17% 8%	1520
	11th to 20th	Night	48% 10% 12% 19% 9% 2	1520
	21st to end	Night	52% 10% 13% 17% 7%	1520
July	1st to 10th	Night	49% 8% 15% 18% 10%	2480
	11th to 20th	Night	49% 8% 14% 24% 6%	2472
	21st to end	Night	47% 9% 12% 23% 9%	2651
August	1st to 10th	Night	56% 7% 13% 18% 6%	2606
	11th to 20th	Night	48% 13% 16% 15% 7%	2809
	21st to end	Night	42% 8% 17% 19% 12% 2	3462
September	1st to 10th	Night	39% 8% 15% 27% 11%	1900
	11th to 20th	Night	39% 6% 11% 29% 13% 1	2072
	21st to end	Night	43% 9% 13% 22% 12% 2	2090
October	1st to 10th	Night	53% 8% 12% 16% 10% 1	2090
	11th to 20th	Night	54% 8% 12% 19% 6% 1	2379
	21st to end	Night	62% 7% 10% 12% 7% 2	2637
November	1st to 10th	Night	57% 7% 10% 16% 8% 2	2407
	11th to 20th	Night	58% 9% 10% 13% 8% 2	2470
	21st to end	Night	64% 9% 10% 12% 5%	2548
December	1st to 10th	Night	73% 8% 7% 9% 3	2660
	11th to 20th	Night	64% 14% 6% 9% 7%	3288
	21st to end	Night	65% 12% 7% 11% 4	4884

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	23% 31% 26% 18% 3	180
	11th to 20th	Day	33% 24% 26% 14% 2 1	180
	21st to end	Day	20% 28% 32% 16% 4 1	198
February	1st to 10th	Day	36% 26% 23% 13% 1	272
	11th to 20th	Day	30% 28% 29% 11% 2	456
	21st to end	Day	29% 24% 29% 15% 2	382
March	1st to 10th	Day	29% 23% 28% 17% 3	460
	11th to 20th	Day	30% 26% 27% 13% 3 1	460
	21st to end	Day	32% 24% 24% 13% 5% 2	506
April	1st to 10th	Day	34% 22% 24% 14% 5% 1	460
	11th to 20th	Day	29% 27% 22% 15% 6% 2	452
	21st to end	Day	33% 22% 27% 12% 4 2	460
May	1st to 10th	Day	35% 21% 25% 14% 3 3	463
	11th to 20th	Day	28% 16% 31% 18% 6% 2	487
	21st to end	Day	20% 20% 32% 21% 6%	529
June	1st to 10th	Day	32% 17% 31% 12% 7% 1	490
	11th to 20th	Day	21% 16% 34% 20% 8% 1	490
	21st to end	Day	27% 20% 28% 17% 6% 2	490
July	1st to 10th	Day	20% 15% 29% 23% 11% 2	485
	11th to 20th	Day	14% 14% 38% 24% 9% 2	484
	21st to end	Day	20% 13% 35% 24% 6% 2	532
August	1st to 10th	Day	17% 14% 30% 25% 13% 2	486
	11th to 20th	Day	20% 14% 29% 19% 14% 5%	479
	21st to end	Day	17% 15% 29% 23% 11% 6%	539
September	1st to 10th	Day	19% 16% 26% 21% 14% 4	490
	11th to 20th	Day	20% 13% 23% 21% 16% 7%	490
	21st to end	Day	19% 15% 29% 20% 13% 5%	490
October	1st to 10th	Day	27% 17% 22% 19% 12% 4	490
	11th to 20th	Day	27% 17% 25% 18% 12% 1	427
	21st to end	Day	31% 19% 26% 18% 5%	411
November	1st to 10th	Day	28% 20% 20% 25% 6% 1	365
	11th to 20th	Day	30% 18% 28% 17% 5% 2	370
	21st to end	Day	28% 22% 27% 17% 4 1	290
December	1st to 10th	Day	28% 27% 23% 13% 8%	180
	11th to 20th	Day	34% 26% 28% 8% 4 1	180
	21st to end	Day	35% 21% 27% 14% 2 1	198
January	1st to 10th	Night	25% 23% 27% 20% 4	760
	11th to 20th	Night	24% 24% 29% 20% 3	760
	21st to end	Night	18% 22% 35% 20% 5%	836
February	1st to 10th	Night	22% 24% 33% 18% 3	760
	11th to 20th	Night	22% 26% 32% 17% 3	743
	21st to end	Night	24% 21% 31% 21% 3	628
March	1st to 10th	Night	26% 20% 29% 21% 3	760
	11th to 20th	Night	25% 21% 27% 21% 6%	760
	21st to end	Night	28% 21% 23% 21% 6% 1	836
April	1st to 10th	Night	29% 21% 25% 20% 4	760
	11th to 20th	Night	24% 21% 23% 25% 5% 1	714
	21st to end	Night	28% 16% 29% 19% 7%	570
May	1st to 10th	Night	29% 13% 25% 23% 8% 1	570
	11th to 20th	Night	20% 13% 31% 27% 9% 1	431
	21st to end	Night	20% 11% 20% 38% 11%	411
June	1st to 10th	Night	30% 10% 22% 29% 9%	380
	11th to 20th	Night	18% 12% 19% 37% 14%	380
	21st to end	Night	23% 9% 21% 37% 10%	380
July	1st to 10th	Night	17% 5% 21% 42% 14% 1	370
	11th to 20th	Night	18% 4 20% 40% 16% 2	368
	21st to end	Night	18% 4 20% 41% 15% 1	416
August	1st to 10th	Night	18% 4 17% 42% 17% 2	436
	11th to 20th	Night	18% 8% 23% 32% 17% 2	562
	21st to end	Night	19% 6% 20% 33% 19% 3	822
September	1st to 10th	Night	19% 9% 20% 32% 17% 2	760
	11th to 20th	Night	21% 8% 17% 30% 21% 4	760
	21st to end	Night	21% 11% 20% 29% 16% 3	760
October	1st to 10th	Night	26% 11% 22% 26% 13% 2	760
	11th to 20th	Night	26% 14% 24% 24% 10% 2	760
	21st to end	Night	31% 17% 26% 21% 5%	812
November	1st to 10th	Night	27% 16% 21% 26% 7% 1	740
	11th to 20th	Night	25% 18% 26% 22% 8% 2	760
	21st to end	Night	25% 23% 24% 21% 5% 2	760
December	1st to 10th	Night	28% 24% 25% 19% 4	760
	11th to 20th	Night	27% 21% 28% 20% 4	760
	21st to end	Night	30% 21% 28% 18% 3	836

Page generated at 2024-10-22 20:20:59. Version ac07

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