Trubble Terrestrial Telescope
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trubble Terrestrial Telescope clear sky chart from 2005-11-06 to 2024-11-05.

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	5% 5% 2 5% 4 4 5% 4 6% 8% 53%	105227
	Night	5% 6% 2 5% 3 3 4 3 5% 7% 57%	102547
Transparency	Day	27% 5% 10% 25% 23% 10%	104969
	Night	26% 4 10% 26% 24% 9%	102395
Seeing	Day	8% 8% 29% 33% 17% 4	15649
	Night	7% 6% 27% 42% 15% 2	25648

By Month

Percentage Cloud Cover SW (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	1 5% 2 7% 4 3 3 2 4 8% 59%	2538
	11th to 20th	Day	2 7% 3 8% 4 4 4 4 5% 7% 52%	2572
	21st to end	Day	1 5% 2 5% 4 4 4 4 6% 8% 58%	3146
February	1st to 10th	Day	3 6% 3 7% 3 4 4 4 4 7% 54%	1710
	11th to 20th	Day	1 5% 2 5% 4 3 4 4 5% 9% 58%	1800
	21st to end	Day	1 8% 3 7% 4 3 3 3 5% 7% 57%	1570
March	1st to 10th	Day	4 9% 2 5% 3 3 3 3 6% 9% 53%	3130
	11th to 20th	Day	5% 8% 3 8% 4 4 4 3 6% 6% 49%	3449
	21st to end	Day	4 8% 3 6% 4 4 5% 4 6% 9% 47%	4058
April	1st to 10th	Day	5% 7% 1 4 3 3 4 3 7% 9% 55%	2280
	11th to 20th	Day	10% 9% 2 6% 4 3 5% 4 6% 8% 45%	2251
	21st to end	Day	10% 8% 3 5% 3 4 5% 4 6% 8% 44%	2280
May	1st to 10th	Day	10% 9% 3 6% 5% 5% 5% 4 6% 8% 39%	4098
	11th to 20th	Day	10% 6% 2 5% 4 5% 6% 6% 8% 9% 39%	4388
	21st to end	Day	6% 4 1 5% 4 5% 6% 5% 8% 9% 48%	4825
June	1st to 10th	Day	5% 4 2 4 3 5% 5% 5% 8% 11% 48%	2660
	11th to 20th	Day	7% 3 1 3 4 5% 5% 5% 7% 9% 52%	2660
	21st to end	Day	3 3 1 4 4 6% 6% 6% 7% 9% 51%	2660
July	1st to 10th	Day	5% 4 2 5% 4 4 5% 4 7% 7% 54%	4430
	11th to 20th	Day	3 3 1 5% 5% 5% 7% 7% 8% 9% 48%	4430
	21st to end	Day	4 3 1 5% 4 4 5% 5% 6% 8% 54%	4772
August	1st to 10th	Day	10% 4 1 5% 4 5% 7% 6% 9% 9% 38%	4092
	11th to 20th	Day	3 2 1 5% 4 5% 7% 5% 8% 9% 50%	3764
	21st to end	Day	4 3 1 4 3 4 6% 4 7% 9% 55%	4180
September	1st to 10th	Day	5% 4 1 4 3 4 4 4 6% 6% 59%	2280
	11th to 20th	Day	6% 3 1 3 3 3 3 4 7% 7% 59%	2265
	21st to end	Day	7% 4 2 3 2 2 3 2 4 6% 64%	2090
October	1st to 10th	Day	5% 3 1 3 2 2 3 2 4 4 71%	3174
	11th to 20th	Day	5% 4 1 3 3 4 4 3 5% 7% 60%	3150
	21st to end	Day	5% 6% 1 4 3 2 3 2 4 6% 63%	3293
November	1st to 10th	Day	3 4 1 3 3 3 3 3 5% 8% 65%	1709
	11th to 20th	Day	2 6% 1 3 3 3 3 3 5% 8% 62%	1710
	21st to end	Day	2 5% 3 5% 3 2 3 4 7% 7% 60%	1573
December	1st to 10th	Day	1 5% 3 5% 4 3 3 4 5% 8% 58%	1520
	11th to 20th	Day	3 5% 2 5% 3 2 4 4 6% 8% 58%	1926
	21st to end	Day	3 8% 3 9% 4 4 3 3 5% 6% 52%	2794
January	1st to 10th	Night	1 6% 3 7% 4 4 3 3 5% 7% 55%	4417
	11th to 20th	Night	1 5% 3 5% 3 4 4 3 5% 8% 58%	4426
	21st to end	Night	2 7% 3 6% 4 3 3 4 5% 6% 56%	4521
February	1st to 10th	Night	2 8% 3 7% 3 3 4 3 5% 7% 54%	2470
	11th to 20th	Night	2 7% 3 7% 5% 4 4 3 5% 6% 56%	2266
	21st to end	Night	2 9% 3 7% 3 3 2 2 4 5% 59%	1884
March	1st to 10th	Night	3 9% 3 5% 3 3 3 3 5% 7% 56%	3734
	11th to 20th	Night	7% 12% 2 4 3 3 3 2 4 6% 55%	3526
	21st to end	Night	5% 8% 2 6% 4 3 4 3 6% 8% 51%	3586
April	1st to 10th	Night	5% 8% 2 4 3 4 3 3 6% 7% 56%	1900
	11th to 20th	Night	10% 7% 1 6% 3 3 3 3 5% 7% 52%	1877
	21st to end	Night	14% 7% 2 5% 3 4 3 3 4 7% 48%	1900
May	1st to 10th	Night	12% 7% 2 5% 4 4 5% 4 6% 7% 44%	2868
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 9% 45%	2517
	21st to end	Night	7% 5% 2 4 3 4 4 4 5% 7% 55%	2762
June	1st to 10th	Night	6% 3 1 4 3 3 4 3 6% 10% 57%	1520
	11th to 20th	Night	5% 3 1 4 3 2 4 4 5% 8% 61%	1520
	21st to end	Night	4 2 2 3 2 3 3 4 6% 9% 61%	1520
July	1st to 10th	Night	5% 2 1 3 3 4 4 4 7% 8% 61%	2540
	11th to 20th	Night	2 2 1 3 4 3 4 4 8% 10% 58%	2540
	21st to end	Night	4 3 1 4 4 3 5% 4 7% 8% 58%	2787
August	1st to 10th	Night	11% 4 2 4 4 4 4 4 8% 9% 46%	2847
	11th to 20th	Night	3 3 2 5% 3 3 5% 4 8% 9% 53%	3075
	21st to end	Night	3 3 1 3 3 4 5% 4 7% 9% 58%	3487
September	1st to 10th	Night	6% 4 2 3 3 3 5% 3 5% 6% 61%	1900
	11th to 20th	Night	7% 2 1 3 2 2 3 3 4 6% 68%	1914
	21st to end	Night	7% 3 1 3 2 2 4 3 4 6% 65%	2090
October	1st to 10th	Night	6% 3 1 2 2 2 2 2 3 4 73%	3793
	11th to 20th	Night	6% 5% 2 5% 3 3 3 3 4 6% 60%	3778
	21st to end	Night	6% 6% 2 4 3 2 3 2 4 6% 64%	4232
November	1st to 10th	Night	3 4 1 3 3 3 3 3 4 7% 66%	2470
	11th to 20th	Night	2 5% 1 4 4 2 3 2 5% 7% 65%	2470
	21st to end	Night	3 6% 2 4 3 2 3 3 6% 7% 60%	2606
December	1st to 10th	Night	2 5% 3 6% 4 3 3 3 4 7% 61%	2660
	11th to 20th	Night	2 6% 2 4 4 3 3 3 5% 11% 57%	3271
	21st to end	Night	4 9% 3 7% 4 4 4 3 5% 7% 52%	4873

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% 2 10% 32% 22% 8%	2539
	11th to 20th	Day	30% 4 12% 28% 18% 8%	2572
	21st to end	Day	24% 3 12% 33% 23% 5%	3146
February	1st to 10th	Day	29% 3 12% 29% 20% 6%	1710
	11th to 20th	Day	23% 4 10% 31% 27% 6%	1810
	21st to end	Day	27% 4 9% 27% 25% 9%	1570
March	1st to 10th	Day	27% 3 8% 26% 30% 6%	3130
	11th to 20th	Day	35% 4 13% 31% 14% 3	3449
	21st to end	Day	33% 4 11% 36% 13% 2	4058
April	1st to 10th	Day	26% 5% 12% 27% 21% 9%	2280
	11th to 20th	Day	37% 5% 9% 23% 19% 7%	2254
	21st to end	Day	37% 5% 10% 26% 19% 3	2280
May	1st to 10th	Day	40% 6% 9% 25% 13% 7%	4098
	11th to 20th	Day	38% 7% 12% 27% 14% 4	4392
	21st to end	Day	28% 5% 13% 29% 20% 5%	4825
June	1st to 10th	Day	27% 7% 17% 26% 17% 7%	2660
	11th to 20th	Day	26% 6% 11% 20% 23% 14%	2660
	21st to end	Day	25% 7% 10% 23% 23% 12%	2660
July	1st to 10th	Day	25% 5% 8% 16% 28% 17%	4361
	11th to 20th	Day	27% 8% 11% 21% 20% 15%	4355
	21st to end	Day	25% 6% 9% 19% 22% 19%	4621
August	1st to 10th	Day	35% 9% 14% 19% 16% 8%	4078
	11th to 20th	Day	25% 9% 13% 19% 22% 13%	3800
	21st to end	Day	23% 6% 10% 21% 26% 14%	4179
September	1st to 10th	Day	23% 6% 7% 21% 27% 17%	2280
	11th to 20th	Day	22% 4 8% 22% 29% 15%	2265
	21st to end	Day	22% 3 6% 21% 36% 12%	2090
October	1st to 10th	Day	18% 3 6% 18% 33% 23%	3174
	11th to 20th	Day	23% 4 11% 27% 28% 8%	3150
	21st to end	Day	22% 2 8% 27% 32% 9%	3293
November	1st to 10th	Day	18% 3 12% 29% 26% 12%	1709
	11th to 20th	Day	20% 3 9% 29% 32% 8%	1710
	21st to end	Day	23% 4 9% 25% 30% 10%	1573
December	1st to 10th	Day	23% 5% 11% 32% 20% 9%	1520
	11th to 20th	Day	23% 4 10% 28% 32% 4	1924
	21st to end	Day	33% 3 8% 25% 25% 7%	2794
January	1st to 10th	Night	29% 3 9% 29% 26% 5%	4417
	11th to 20th	Night	24% 4 14% 26% 23% 10%	4426
	21st to end	Night	29% 3 12% 32% 18% 6%	4521
February	1st to 10th	Night	29% 4 10% 29% 22% 6%	2470
	11th to 20th	Night	30% 3 8% 30% 22% 6%	2266
	21st to end	Night	28% 3 6% 24% 27% 12%	1884
March	1st to 10th	Night	27% 4 6% 22% 35% 6%	3734
	11th to 20th	Night	32% 3 12% 24% 26% 4	3526
	21st to end	Night	32% 4 12% 32% 17% 3	3586
April	1st to 10th	Night	27% 5% 9% 26% 22% 10%	1900
	11th to 20th	Night	33% 4 11% 26% 19% 7%	1877
	21st to end	Night	37% 4 7% 27% 22% 3	1900
May	1st to 10th	Night	36% 6% 11% 24% 15% 8%	2868
	11th to 20th	Night	37% 4 16% 25% 15% 4	2518
	21st to end	Night	28% 5% 17% 24% 20% 7%	2762
June	1st to 10th	Night	24% 4 20% 29% 15% 8%	1520
	11th to 20th	Night	22% 4 11% 22% 22% 18%	1520
	21st to end	Night	19% 6% 10% 24% 28% 13%	1520
July	1st to 10th	Night	20% 5% 11% 23% 28% 14%	2500
	11th to 20th	Night	18% 5% 15% 27% 23% 12%	2492
	21st to end	Night	21% 5% 12% 28% 19% 15%	2700
August	1st to 10th	Night	32% 6% 16% 23% 17% 5%	2838
	11th to 20th	Night	23% 8% 17% 22% 19% 11%	3105
	21st to end	Night	21% 6% 12% 25% 27% 11%	3487
September	1st to 10th	Night	23% 5% 9% 22% 22% 20%	1900
	11th to 20th	Night	18% 3 9% 27% 25% 18%	1914
	21st to end	Night	22% 3 6% 24% 31% 14%	2090
October	1st to 10th	Night	16% 2 8% 18% 32% 24%	3793
	11th to 20th	Night	25% 3 8% 26% 28% 9%	3778
	21st to end	Night	23% 3 6% 26% 32% 11%	4232
November	1st to 10th	Night	19% 4 10% 26% 28% 13%	2470
	11th to 20th	Night	20% 3 7% 30% 31% 9%	2470
	21st to end	Night	23% 3 9% 24% 31% 10%	2606
December	1st to 10th	Night	24% 3 11% 28% 23% 10%	2660
	11th to 20th	Night	23% 4 8% 30% 31% 4	3272
	21st to end	Night	33% 3 8% 25% 25% 6%	4873

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	6% 10% 26% 42% 12% 4	270
	11th to 20th	Day	6% 10% 38% 35% 10% 1	270
	21st to end	Day	4 11% 39% 35% 9% 1	297
February	1st to 10th	Day	6% 17% 42% 32% 3 1	270
	11th to 20th	Day	4 12% 46% 30% 7%	270
	21st to end	Day	7% 14% 44% 31% 4	225
March	1st to 10th	Day	7% 16% 29% 39% 9% 1	270
	11th to 20th	Day	13% 13% 32% 31% 10% 1	432
	21st to end	Day	12% 16% 39% 24% 7% 1	506
April	1st to 10th	Day	12% 17% 38% 25% 8% 1	460
	11th to 20th	Day	17% 20% 37% 18% 5% 2	452
	21st to end	Day	16% 17% 33% 23% 9% 1	460
May	1st to 10th	Day	15% 14% 32% 27% 10% 2	601
	11th to 20th	Day	20% 7% 23% 31% 15% 5%	675
	21st to end	Day	10% 8% 27% 30% 21% 4	734
June	1st to 10th	Day	6% 5% 23% 35% 24% 7%	680
	11th to 20th	Day	8% 6% 28% 35% 20% 3	680
	21st to end	Day	4 5% 26% 37% 23% 6%	680
July	1st to 10th	Day	8% 2 18% 35% 28% 9%	671
	11th to 20th	Day	5% 2 16% 38% 29% 10%	668
	21st to end	Day	5% 2 18% 34% 33% 8%	721
August	1st to 10th	Day	8% 2 23% 39% 22% 6%	487
	11th to 20th	Day	4 3 25% 41% 21% 6%	477
	21st to end	Day	7% 2 28% 36% 20% 7%	539
September	1st to 10th	Day	8% 3 23% 38% 21% 7%	490
	11th to 20th	Day	6% 3 28% 33% 25% 4	475
	21st to end	Day	9% 3 26% 32% 20% 10%	300
October	1st to 10th	Day	11% 5% 25% 29% 20% 10%	300
	11th to 20th	Day	3 11% 34% 34% 14% 4	300
	21st to end	Day	7% 10% 34% 35% 13% 1	330
November	1st to 10th	Day	6% 10% 31% 33% 14% 5%	282
	11th to 20th	Day	7% 9% 31% 43% 6% 4	270
	21st to end	Day	6% 11% 31% 43% 8% 1	270
December	1st to 10th	Day	7% 13% 32% 35% 12% 2	270
	11th to 20th	Day	6% 10% 34% 42% 7% 1	270
	21st to end	Day	6% 12% 35% 38% 6% 3	297
January	1st to 10th	Night	4 12% 31% 39% 11% 3	950
	11th to 20th	Night	5% 15% 38% 34% 8% 1	946
	21st to end	Night	5% 9% 33% 44% 7% 1	836
February	1st to 10th	Night	6% 9% 45% 34% 5% 1	760
	11th to 20th	Night	4 9% 41% 40% 7%	744
	21st to end	Night	6% 10% 39% 42% 3	628
March	1st to 10th	Night	5% 6% 38% 42% 8% 1	760
	11th to 20th	Night	9% 7% 30% 43% 11% 1	760
	21st to end	Night	10% 9% 33% 40% 7% 1	697
April	1st to 10th	Night	8% 10% 35% 41% 5%	570
	11th to 20th	Night	14% 8% 33% 35% 9% 1	563
	21st to end	Night	18% 7% 27% 36% 11% 1	570
May	1st to 10th	Night	17% 8% 26% 35% 13% 2	570
	11th to 20th	Night	21% 2 20% 36% 18% 3	561
	21st to end	Night	10% 3 26% 36% 23% 2	617
June	1st to 10th	Night	7% 2 15% 49% 23% 3	570
	11th to 20th	Night	6% 3 23% 51% 16% 1	570
	21st to end	Night	6% 2 13% 49% 27% 3	570
July	1st to 10th	Night	8% 3 10% 41% 34% 4	555
	11th to 20th	Night	3 1 9% 46% 37% 5%	552
	21st to end	Night	7% 1 7% 39% 41% 4	624
August	1st to 10th	Night	7% 2 9% 44% 34% 4	567
	11th to 20th	Night	6% 1 8% 48% 31% 4	564
	21st to end	Night	4 1 10% 47% 34% 4	627
September	1st to 10th	Night	8% 2 14% 45% 25% 6%	570
	11th to 20th	Night	8% 1 15% 47% 23% 5%	570
	21st to end	Night	8% 2 22% 44% 21% 3	570
October	1st to 10th	Night	11% 4 21% 44% 17% 4	753
	11th to 20th	Night	8% 4 24% 48% 13% 2	760
	21st to end	Night	11% 6% 29% 41% 10% 3	899
November	1st to 10th	Night	5% 5% 31% 45% 13% 2	950
	11th to 20th	Night	5% 10% 34% 43% 7% 2	950
	21st to end	Night	7% 7% 30% 45% 10% 1	950
December	1st to 10th	Night	4 11% 32% 45% 7%	950
	11th to 20th	Night	6% 9% 35% 41% 9% 1	950
	21st to end	Night	6% 9% 34% 42% 8% 1	1045

Page generated at 2024-11-03 00:11:28. Version ac07

Copyright © 2024 Attilla Danko.