Tamke-Allan Observatory
Clear Sky Chart
History

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

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	13% 7% 2 6% 5% 4 5% 4 6% 8% 39%	101017
	Night	14% 7% 2 6% 4 4 4 4 6% 7% 42%	98108
Transparency	Day	39% 9% 12% 21% 15% 3	104800
	Night	38% 8% 12% 22% 17% 4	102463
Seeing	Day	17% 11% 23% 23% 18% 8%	14788
	Night	16% 9% 23% 30% 19% 3	24807

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	17% 12% 3 6% 4 4 4 5% 5% 6% 33%	2836
	11th to 20th	Day	19% 9% 5% 9% 4 5% 5% 4 4 5% 33%	2840
	21st to end	Day	23% 11% 2 6% 3 3 3 4 4 7% 34%	3170
February	1st to 10th	Day	19% 11% 3 6% 5% 4 4 3 5% 4 37%	1900
	11th to 20th	Day	22% 8% 4 6% 4 4 4 3 4 5% 36%	1848
	21st to end	Day	21% 8% 3 7% 5% 3 3 3 5% 5% 36%	1570
March	1st to 10th	Day	23% 11% 3 7% 4 3 3 3 4 6% 31%	3170
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 6% 49%	3480
	21st to end	Day	16% 7% 2 6% 5% 5% 5% 4 5% 6% 40%	3815
April	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 6% 44%	2209
	11th to 20th	Day	14% 7% 2 5% 4 4 4 3 5% 7% 45%	2254
	21st to end	Day	13% 6% 2 6% 3 4 5% 4 5% 7% 44%	2449
May	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 5% 6% 36%	4082
	11th to 20th	Day	15% 7% 3 8% 5% 4 5% 4 6% 8% 35%	4081
	21st to end	Day	11% 6% 2 6% 4 5% 5% 4 7% 9% 42%	4476
June	1st to 10th	Day	10% 7% 2 6% 4 5% 5% 5% 7% 10% 39%	2470
	11th to 20th	Day	5% 4 1 5% 5% 5% 6% 7% 9% 10% 43%	2470
	21st to end	Day	7% 5% 2 5% 5% 5% 7% 5% 8% 11% 40%	2470
July	1st to 10th	Day	6% 4 2 7% 6% 6% 6% 6% 9% 11% 36%	4120
	11th to 20th	Day	10% 6% 2 6% 6% 6% 6% 5% 8% 11% 35%	4120
	21st to end	Day	16% 10% 4 10% 7% 7% 7% 5% 7% 7% 19%	4466
August	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 6% 9% 11% 40%	4104
	11th to 20th	Day	6% 4 2 6% 5% 5% 7% 5% 8% 11% 40%	3855
	21st to end	Day	6% 4 2 5% 4 4 5% 5% 6% 8% 51%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 7% 8% 42%	2138
	11th to 20th	Day	15% 5% 2 6% 4 5% 4 5% 6% 8% 41%	2090
	21st to end	Day	15% 5% 2 5% 4 4 4 3 4 6% 48%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 3 3 2 4 5% 55%	2090
	11th to 20th	Day	12% 5% 2 4 3 3 3 3 4 6% 54%	1981
	21st to end	Day	14% 5% 2 4 4 3 3 4 5% 7% 49%	2024
November	1st to 10th	Day	12% 6% 2 4 4 2 3 3 4 6% 54%	1762
	11th to 20th	Day	14% 6% 3 5% 3 3 3 3 5% 6% 49%	1710
	21st to end	Day	16% 7% 2 4 4 4 3 4 5% 5% 46%	1710
December	1st to 10th	Day	22% 8% 3 7% 5% 3 5% 4 5% 5% 34%	1710
	11th to 20th	Day	15% 10% 3 6% 5% 5% 4 4 6% 6% 37%	2153
	21st to end	Day	19% 12% 2 7% 4 4 4 3 6% 7% 31%	3124
January	1st to 10th	Night	17% 9% 3 6% 4 4 4 4 6% 6% 35%	4109
	11th to 20th	Night	20% 8% 3 7% 4 3 4 3 5% 6% 37%	4120
	21st to end	Night	21% 12% 3 6% 4 4 4 4 5% 5% 32%	4468
February	1st to 10th	Night	17% 8% 3 6% 4 5% 4 3 6% 6% 38%	2280
	11th to 20th	Night	23% 8% 3 6% 4 4 4 3 5% 5% 36%	2218
	21st to end	Night	24% 8% 3 5% 5% 3 5% 3 4 5% 34%	1884
March	1st to 10th	Night	22% 9% 2 7% 5% 5% 4 3 6% 7% 31%	3683
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 50%	3480
	21st to end	Night	15% 7% 2 7% 5% 4 4 4 5% 6% 42%	3817
April	1st to 10th	Night	12% 5% 1 5% 3 4 4 3 5% 7% 49%	1986
	11th to 20th	Night	14% 5% 2 5% 4 3 3 3 5% 6% 49%	1875
	21st to end	Night	11% 5% 2 6% 4 4 4 4 6% 8% 45%	1729
May	1st to 10th	Night	14% 7% 3 8% 6% 4 5% 4 6% 8% 36%	2813
	11th to 20th	Night	16% 7% 2 6% 4 4 4 4 6% 7% 40%	2812
	21st to end	Night	7% 5% 3 7% 4 5% 5% 4 6% 9% 43%	3079
June	1st to 10th	Night	7% 6% 3 7% 5% 5% 4 6% 7% 8% 42%	1710
	11th to 20th	Night	4 3 1 4 4 4 4 5% 9% 12% 50%	1710
	21st to end	Night	6% 5% 2 6% 6% 5% 5% 5% 6% 11% 43%	1710
July	1st to 10th	Night	7% 6% 2 6% 6% 5% 6% 6% 9% 12% 35%	2840
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 5% 8% 10% 44%	2840
	21st to end	Night	13% 11% 3 9% 7% 6% 6% 5% 7% 9% 24%	3087
August	1st to 10th	Night	6% 4 2 6% 4 4 5% 5% 7% 11% 46%	2825
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 6% 9% 49%	2969
	21st to end	Night	6% 4 2 4 3 4 4 4 6% 9% 56%	3476
September	1st to 10th	Night	9% 7% 2 6% 4 5% 4 4 6% 7% 45%	2023
	11th to 20th	Night	12% 6% 3 8% 4 3 3 3 6% 9% 42%	2090
	21st to end	Night	13% 6% 2 5% 3 4 4 2 5% 6% 50%	2090
October	1st to 10th	Night	11% 5% 2 4 3 3 4 2 4 6% 57%	2090
	11th to 20th	Night	13% 5% 1 4 3 3 3 3 4 5% 54%	2198
	21st to end	Night	14% 6% 2 4 3 4 3 3 3 5% 52%	2570
November	1st to 10th	Night	12% 6% 1 5% 4 3 4 3 5% 6% 51%	2536
	11th to 20th	Night	12% 7% 3 5% 4 3 3 3 4 6% 49%	2477
	21st to end	Night	16% 7% 3 5% 3 3 5% 4 5% 8% 43%	2470
December	1st to 10th	Night	21% 9% 3 7% 4 4 4 3 5% 5% 35%	2470
	11th to 20th	Night	17% 8% 3 6% 4 4 3 3 5% 6% 41%	3042
	21st to end	Night	20% 9% 3 8% 5% 6% 5% 5% 7% 7% 27%	4532

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	48% 7% 9% 20% 15% 2	2837
	11th to 20th	Day	51% 6% 9% 18% 16% 1	2840
	21st to end	Day	49% 7% 10% 21% 13% 1	3170
February	1st to 10th	Day	51% 5% 8% 17% 16% 2	1900
	11th to 20th	Day	51% 6% 8% 18% 14% 3	1858
	21st to end	Day	50% 7% 8% 15% 15% 6%	1570
March	1st to 10th	Day	53% 8% 8% 14% 11% 6%	3170
	11th to 20th	Day	36% 6% 9% 25% 18% 5%	3480
	21st to end	Day	43% 8% 9% 27% 12% 2	3815
April	1st to 10th	Day	38% 8% 12% 22% 17% 3	2209
	11th to 20th	Day	39% 6% 10% 17% 24% 5%	2254
	21st to end	Day	38% 8% 13% 25% 14% 2	2449
May	1st to 10th	Day	44% 11% 11% 22% 11% 1	4120
	11th to 20th	Day	44% 11% 13% 22% 9% 1	4085
	21st to end	Day	36% 10% 14% 20% 17% 2	4489
June	1st to 10th	Day	37% 12% 16% 19% 13% 2	2470
	11th to 20th	Day	30% 14% 19% 21% 14% 2	2470
	21st to end	Day	34% 14% 17% 18% 13% 3	2470
July	1st to 10th	Day	35% 14% 20% 19% 10% 1	4055
	11th to 20th	Day	38% 12% 20% 21% 7% 2	4051
	21st to end	Day	60% 12% 10% 12% 5% 1	4324
August	1st to 10th	Day	32% 11% 17% 29% 10%	4091
	11th to 20th	Day	32% 12% 17% 24% 14% 1	3894
	21st to end	Day	28% 9% 14% 31% 17% 2	4179
September	1st to 10th	Day	37% 10% 13% 19% 16% 5%	2138
	11th to 20th	Day	39% 9% 12% 20% 16% 3	2090
	21st to end	Day	35% 7% 13% 21% 18% 6%	2090
October	1st to 10th	Day	22% 6% 7% 21% 31% 13%	3480
	11th to 20th	Day	22% 4 8% 24% 32% 10%	3273
	21st to end	Day	27% 6% 10% 25% 22% 8%	3313
November	1st to 10th	Day	32% 5% 9% 24% 25% 5%	1762
	11th to 20th	Day	36% 4 8% 24% 24% 5%	1710
	21st to end	Day	40% 5% 10% 23% 20% 3	1710
December	1st to 10th	Day	51% 6% 7% 21% 12% 3	1710
	11th to 20th	Day	46% 8% 10% 19% 15% 2	2150
	21st to end	Day	49% 7% 13% 21% 9% 1	3124
January	1st to 10th	Night	43% 9% 10% 20% 15% 2	4109
	11th to 20th	Night	45% 8% 9% 16% 17% 5%	4120
	21st to end	Night	52% 6% 9% 17% 15% 1	4468
February	1st to 10th	Night	46% 5% 10% 21% 16% 3	2280
	11th to 20th	Night	50% 5% 8% 18% 14% 4	2219
	21st to end	Night	52% 6% 8% 15% 15% 4	1884
March	1st to 10th	Night	49% 9% 12% 13% 14% 4	3683
	11th to 20th	Night	32% 7% 9% 25% 17% 10%	3480
	21st to end	Night	42% 7% 10% 24% 16% 2	3817
April	1st to 10th	Night	33% 7% 12% 24% 21% 3	1986
	11th to 20th	Night	36% 6% 9% 21% 22% 7%	1875
	21st to end	Night	36% 9% 11% 27% 15% 2	1729
May	1st to 10th	Night	42% 11% 13% 23% 10% 1	2840
	11th to 20th	Night	41% 10% 14% 21% 13% 1	2813
	21st to end	Night	31% 13% 15% 23% 16% 1	3087
June	1st to 10th	Night	36% 10% 15% 23% 14% 2	1710
	11th to 20th	Night	23% 11% 23% 28% 14% 2	1710
	21st to end	Night	34% 10% 16% 24% 12% 4	1710
July	1st to 10th	Night	37% 12% 21% 20% 9% 1	2795
	11th to 20th	Night	32% 11% 22% 26% 7% 3	2786
	21st to end	Night	54% 13% 13% 13% 6% 1	2988
August	1st to 10th	Night	29% 10% 18% 31% 12% 1	2814
	11th to 20th	Night	30% 10% 20% 26% 13% 1	2996
	21st to end	Night	23% 8% 15% 38% 15% 1	3476
September	1st to 10th	Night	35% 10% 16% 18% 15% 6%	2023
	11th to 20th	Night	38% 9% 14% 17% 21% 1	2090
	21st to end	Night	34% 7% 11% 21% 21% 5%	2090
October	1st to 10th	Night	24% 6% 8% 21% 27% 14%	3480
	11th to 20th	Night	20% 4 6% 24% 32% 14%	3645
	21st to end	Night	25% 4 7% 26% 28% 9%	4231
November	1st to 10th	Night	34% 5% 8% 21% 23% 8%	2536
	11th to 20th	Night	35% 5% 8% 21% 24% 7%	2477
	21st to end	Night	41% 5% 7% 23% 21% 3	2470
December	1st to 10th	Night	49% 6% 10% 19% 13% 3	2470
	11th to 20th	Night	42% 7% 10% 20% 19% 2	3044
	21st to end	Night	49% 10% 13% 17% 10% 1	4532

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	24% 26% 30% 17% 3	270
	11th to 20th	Day	30% 25% 27% 14% 3 1	270
	21st to end	Day	21% 24% 40% 11% 4	297
February	1st to 10th	Day	28% 25% 26% 16% 5%	270
	11th to 20th	Day	36% 23% 31% 9% 1 1	270
	21st to end	Day	39% 23% 30% 8% 1	225
March	1st to 10th	Day	27% 20% 32% 16% 4	294
	11th to 20th	Day	22% 20% 32% 20% 5% 1	460
	21st to end	Day	24% 15% 34% 18% 8%	506
April	1st to 10th	Day	20% 19% 26% 22% 11% 2	460
	11th to 20th	Day	20% 15% 29% 23% 12% 1	452
	21st to end	Day	20% 12% 29% 25% 11% 3	460
May	1st to 10th	Day	15% 14% 32% 23% 11% 4	463
	11th to 20th	Day	11% 8% 25% 29% 17% 10%	487
	21st to end	Day	15% 7% 18% 25% 22% 13%	529
June	1st to 10th	Day	13% 6% 21% 25% 23% 12%	490
	11th to 20th	Day	6% 3 14% 29% 30% 17%	490
	21st to end	Day	9% 2 19% 29% 26% 15%	490
July	1st to 10th	Day	8% 4 12% 26% 29% 21%	485
	11th to 20th	Day	10% 4 11% 25% 30% 20%	484
	21st to end	Day	11% 5% 10% 25% 31% 18%	532
August	1st to 10th	Day	11% 5% 12% 26% 31% 15%	486
	11th to 20th	Day	11% 3 18% 29% 29% 10%	479
	21st to end	Day	10% 3 12% 22% 32% 21%	539
September	1st to 10th	Day	10% 3 15% 23% 33% 16%	490
	11th to 20th	Day	15% 3 11% 24% 32% 15%	490
	21st to end	Day	18% 5% 15% 25% 28% 8%	490
October	1st to 10th	Day	13% 4 23% 26% 24% 9%	490
	11th to 20th	Day	10% 14% 24% 29% 19% 3	490
	21st to end	Day	18% 9% 24% 29% 16% 3	473
November	1st to 10th	Day	18% 10% 30% 25% 13% 3	300
	11th to 20th	Day	14% 14% 35% 31% 6%	270
	21st to end	Day	17% 12% 36% 23% 10% 1	270
December	1st to 10th	Day	29% 18% 28% 19% 6%	270
	11th to 20th	Day	23% 17% 29% 21% 9%	270
	21st to end	Day	29% 18% 30% 18% 5% 1	297
January	1st to 10th	Night	22% 16% 33% 24% 4	760
	11th to 20th	Night	23% 16% 32% 24% 4	760
	21st to end	Night	20% 15% 37% 26% 2	836
February	1st to 10th	Night	20% 13% 35% 27% 4	760
	11th to 20th	Night	28% 15% 34% 22% 2	743
	21st to end	Night	25% 18% 34% 21% 1	628
March	1st to 10th	Night	20% 13% 32% 32% 4	760
	11th to 20th	Night	19% 14% 34% 25% 8% 1	760
	21st to end	Night	20% 12% 30% 29% 8%	836
April	1st to 10th	Night	14% 13% 32% 31% 10%	656
	11th to 20th	Night	17% 10% 29% 31% 13%	563
	21st to end	Night	12% 8% 32% 37% 10% 1	570
May	1st to 10th	Night	11% 6% 27% 36% 17% 2	570
	11th to 20th	Night	12% 6% 22% 34% 22% 4	561
	21st to end	Night	7% 4 14% 34% 35% 4	617
June	1st to 10th	Night	8% 3 16% 36% 32% 5%	570
	11th to 20th	Night	4 2 14% 34% 37% 9%	570
	21st to end	Night	7% 1 10% 35% 38% 8%	570
July	1st to 10th	Night	10% 3 9% 26% 42% 11%	555
	11th to 20th	Night	8% 4 8% 28% 43% 10%	552
	21st to end	Night	8% 3 10% 29% 40% 10%	624
August	1st to 10th	Night	9% 1 8% 28% 44% 9%	567
	11th to 20th	Night	10% 2 10% 32% 41% 4	564
	21st to end	Night	10% 1 8% 30% 42% 9%	627
September	1st to 10th	Night	10% 3 12% 29% 38% 8%	693
	11th to 20th	Night	13% 3 13% 31% 34% 6%	760
	21st to end	Night	15% 3 17% 31% 31% 2	760
October	1st to 10th	Night	11% 7% 18% 27% 31% 6%	760
	11th to 20th	Night	16% 6% 24% 33% 19% 2	760
	21st to end	Night	16% 7% 22% 37% 17% 2	836
November	1st to 10th	Night	14% 8% 22% 35% 17% 3	780
	11th to 20th	Night	14% 11% 31% 33% 10% 1	763
	21st to end	Night	19% 10% 27% 32% 11%	760
December	1st to 10th	Night	24% 13% 27% 28% 8%	760
	11th to 20th	Night	22% 11% 30% 30% 8%	760
	21st to end	Night	26% 14% 24% 31% 5%	836

Page generated at 2024-11-08 06:44:48. Version ac07

Copyright © 2024 Attilla Danko.