Lake Titus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Titus Observatory clear sky chart from 2005-11-06 to 2024-01-31.

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	19% 12% 5% 8% 6% 3 4 4 4 6% 27%	74895
	Night	18% 14% 5% 9% 6% 3 4 4 4 5% 27%	75227
Transparency	Day	59% 4 10% 18% 9% 1	74600
	Night	61% 3 10% 17% 8% 1	75056
Seeing	Day	31% 16% 29% 16% 6% 2	13530
	Night	29% 18% 26% 20% 8% 1	22717

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% 22% 8% 14% 10% 4 4 3 3 4 14%	1517
	11th to 20th	Day	15% 19% 7% 13% 12% 4 4 4 4 3 16%	1520
	21st to end	Day	11% 16% 8% 13% 10% 4 6% 4 4 4 17%	1678
February	1st to 10th	Day	13% 19% 8% 15% 11% 4 4 4 3 4 15%	1620
	11th to 20th	Day	12% 17% 9% 14% 10% 4 5% 4 4 5% 18%	1658
	21st to end	Day	15% 18% 8% 13% 8% 6% 4 3 5% 4 17%	1480
March	1st to 10th	Day	15% 16% 9% 11% 8% 3 5% 3 4 3 23%	1797
	11th to 20th	Day	16% 16% 7% 9% 8% 3 5% 4 4 3 25%	1896
	21st to end	Day	19% 16% 5% 9% 4 2 4 3 3 5% 30%	2351
April	1st to 10th	Day	19% 17% 7% 7% 5% 3 3 3 4 4 28%	2160
	11th to 20th	Day	19% 15% 4 7% 5% 3 3 3 4 4 33%	2134
	21st to end	Day	23% 15% 3 6% 4 3 4 5% 4 4 28%	2263
May	1st to 10th	Day	24% 10% 3 6% 5% 2 4 4 4 6% 31%	2488
	11th to 20th	Day	19% 10% 2 6% 6% 2 4 4 5% 6% 35%	2478
	21st to end	Day	19% 9% 3 6% 5% 3 5% 5% 5% 7% 33%	2725
June	1st to 10th	Day	29% 7% 2 5% 6% 3 5% 5% 5% 6% 27%	2520
	11th to 20th	Day	21% 7% 3 5% 6% 4 4 6% 5% 8% 32%	2520
	21st to end	Day	25% 8% 3 6% 5% 3 5% 5% 5% 6% 28%	2520
July	1st to 10th	Day	18% 6% 3 5% 6% 3 6% 4 6% 7% 36%	2520
	11th to 20th	Day	17% 6% 3 6% 6% 3 5% 7% 7% 8% 32%	2520
	21st to end	Day	17% 7% 3 5% 6% 3 6% 5% 6% 10% 33%	2744
August	1st to 10th	Day	18% 7% 2 6% 6% 4 6% 5% 5% 9% 32%	2506
	11th to 20th	Day	17% 5% 3 6% 6% 4 6% 6% 6% 8% 33%	2228
	21st to end	Day	19% 6% 3 5% 6% 3 6% 5% 6% 8% 34%	2376
September	1st to 10th	Day	18% 6% 2 5% 5% 3 4 4 5% 9% 39%	2160
	11th to 20th	Day	19% 7% 2 5% 3 2 3 4 4 7% 43%	2102
	21st to end	Day	19% 8% 3 5% 5% 3 4 5% 6% 7% 34%	1980
October	1st to 10th	Day	26% 10% 3 7% 5% 3 5% 4 4 5% 29%	1832
	11th to 20th	Day	22% 15% 4 8% 4 3 4 4 4 5% 26%	1797
	21st to end	Day	28% 19% 3 5% 5% 2 3 3 4 4 23%	1782
November	1st to 10th	Day	16% 18% 5% 8% 5% 4 4 4 4 5% 27%	1671
	11th to 20th	Day	17% 17% 7% 10% 7% 3 4 4 3 4 24%	1634
	21st to end	Day	16% 20% 8% 12% 8% 4 4 3 3 4 18%	1520
December	1st to 10th	Day	19% 23% 10% 12% 8% 3 4 3 3 4 11%	1520
	11th to 20th	Day	19% 19% 7% 14% 7% 2 4 3 4 4 17%	1906
	21st to end	Day	21% 18% 9% 9% 9% 3 4 4 3 4 16%	2772
January	1st to 10th	Night	14% 21% 9% 17% 8% 4 5% 4 3 3 12%	2649
	11th to 20th	Night	13% 19% 8% 14% 11% 4 7% 3 3 3 15%	2660
	21st to end	Night	10% 16% 8% 14% 10% 4 6% 6% 3 4 18%	2902
February	1st to 10th	Night	13% 17% 8% 17% 11% 4 4 3 3 4 15%	2340
	11th to 20th	Night	13% 14% 7% 14% 11% 4 6% 4 3 3 20%	2188
	21st to end	Night	13% 18% 7% 12% 9% 5% 4 3 4 4 22%	1776
March	1st to 10th	Night	14% 17% 7% 11% 8% 4 4 3 3 3 24%	2150
	11th to 20th	Night	15% 18% 6% 10% 7% 4 4 3 4 4 27%	2061
	21st to end	Night	17% 16% 5% 8% 6% 2 4 3 2 4 33%	2004
April	1st to 10th	Night	19% 17% 5% 9% 6% 3 4 3 3 4 27%	1800
	11th to 20th	Night	22% 13% 3 6% 6% 3 5% 4 3 5% 31%	1775
	21st to end	Night	22% 12% 3 6% 5% 2 4 3 5% 5% 32%	1697
May	1st to 10th	Night	25% 11% 3 6% 5% 3 5% 5% 4 6% 29%	1487
	11th to 20th	Night	17% 10% 3 5% 5% 3 4 4 6% 5% 37%	1415
	21st to end	Night	17% 7% 3 6% 5% 3 5% 5% 5% 8% 37%	1550
June	1st to 10th	Night	25% 7% 3 5% 5% 2 4 6% 6% 8% 29%	1440
	11th to 20th	Night	19% 6% 3 6% 6% 3 5% 5% 6% 5% 37%	1440
	21st to end	Night	21% 7% 2 5% 7% 3 5% 5% 6% 7% 32%	1440
July	1st to 10th	Night	14% 4 2 5% 5% 3 5% 4 6% 7% 45%	1440
	11th to 20th	Night	11% 5% 3 5% 5% 3 6% 6% 7% 8% 41%	1440
	21st to end	Night	16% 7% 2 5% 5% 3 5% 5% 7% 7% 40%	1574
August	1st to 10th	Night	15% 5% 2 5% 5% 3 4 6% 6% 9% 41%	1432
	11th to 20th	Night	18% 6% 3 6% 5% 3 4 3 6% 6% 41%	1651
	21st to end	Night	16% 7% 3 6% 5% 3 4 5% 5% 8% 38%	1980
September	1st to 10th	Night	19% 6% 3 5% 6% 4 4 4 4 5% 41%	1800
	11th to 20th	Night	17% 7% 2 4 4 2 3 4 5% 6% 46%	1857
	21st to end	Night	20% 7% 2 6% 4 2 3 4 6% 7% 39%	1980
October	1st to 10th	Night	23% 9% 3 6% 5% 2 4 5% 5% 6% 32%	2124
	11th to 20th	Night	21% 14% 4 6% 6% 3 4 4 4 6% 28%	2161
	21st to end	Night	27% 18% 4 6% 4 3 4 3 4 5% 22%	2574
November	1st to 10th	Night	20% 16% 4 8% 5% 3 4 4 5% 4 26%	2407
	11th to 20th	Night	19% 15% 7% 9% 5% 3 4 4 4 5% 25%	2541
	21st to end	Night	17% 20% 8% 11% 6% 3 5% 3 3 4 19%	2660
December	1st to 10th	Night	18% 25% 11% 12% 7% 3 3 3 3 4 11%	2660
	11th to 20th	Night	18% 22% 8% 13% 6% 3 4 3 3 3 17%	3288
	21st to end	Night	23% 19% 7% 14% 7% 4 3 3 3 3 14%	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	76% 2 6% 12% 3	1518
	11th to 20th	Day	75% 2 5% 9% 8% 2	1520
	21st to end	Day	70% 3 9% 9% 7% 1	1678
February	1st to 10th	Day	76% 2 4 13% 3 2	1620
	11th to 20th	Day	71% 3 6% 12% 7% 1	1667
	21st to end	Day	71% 3 6% 11% 7% 2	1480
March	1st to 10th	Day	68% 2 8% 13% 8% 2	1800
	11th to 20th	Day	64% 4 9% 10% 11% 2	1896
	21st to end	Day	59% 2 5% 16% 14% 3	2351
April	1st to 10th	Day	62% 2 6% 18% 10% 2	2160
	11th to 20th	Day	57% 3 7% 19% 14% 2	2134
	21st to end	Day	60% 3 9% 14% 11% 3	2263
May	1st to 10th	Day	56% 4 7% 19% 12% 2	2488
	11th to 20th	Day	50% 5% 9% 21% 14% 2	2482
	21st to end	Day	51% 4 13% 19% 11% 1	2725
June	1st to 10th	Day	58% 4 10% 17% 10% 1	2520
	11th to 20th	Day	50% 4 11% 24% 9% 2	2520
	21st to end	Day	56% 5% 11% 19% 9% 1	2520
July	1st to 10th	Day	45% 5% 12% 25% 11% 1	2450
	11th to 20th	Day	47% 6% 14% 27% 6%	2445
	21st to end	Day	48% 6% 15% 23% 8%	2591
August	1st to 10th	Day	51% 5% 14% 23% 7%	2492
	11th to 20th	Day	49% 4 16% 22% 9%	2228
	21st to end	Day	48% 5% 12% 24% 10%	2376
September	1st to 10th	Day	44% 4 13% 26% 12% 1	2160
	11th to 20th	Day	42% 4 10% 30% 14% 1	2102
	21st to end	Day	48% 5% 14% 25% 9% 1	1980
October	1st to 10th	Day	60% 3 8% 18% 11% 1	1832
	11th to 20th	Day	61% 4 13% 15% 6% 1	1797
	21st to end	Day	66% 3 9% 14% 7% 1	1782
November	1st to 10th	Day	61% 4 11% 17% 7%	1671
	11th to 20th	Day	66% 3 9% 12% 7% 3	1634
	21st to end	Day	72% 3 10% 11% 4	1520
December	1st to 10th	Day	79% 3 8% 8% 2	1520
	11th to 20th	Day	73% 3 9% 10% 5%	1906
	21st to end	Day	75% 2 7% 12% 4	2772
January	1st to 10th	Night	79% 4 5% 8% 4	2649
	11th to 20th	Night	76% 3 6% 10% 4 1	2660
	21st to end	Night	69% 4 7% 11% 8% 1	2902
February	1st to 10th	Night	76% 2 6% 8% 6% 1	2340
	11th to 20th	Night	70% 3 6% 13% 7%	2190
	21st to end	Night	67% 3 6% 14% 9% 1	1776
March	1st to 10th	Night	67% 3 8% 13% 8% 1	2160
	11th to 20th	Night	63% 2 8% 17% 8% 2	2062
	21st to end	Night	58% 3 6% 18% 13% 2	2004
April	1st to 10th	Night	62% 3 5% 17% 11% 1	1800
	11th to 20th	Night	59% 3 9% 18% 11% 1	1775
	21st to end	Night	55% 3 8% 18% 12% 3	1697
May	1st to 10th	Night	57% 3 8% 15% 14% 2	1487
	11th to 20th	Night	48% 4 10% 20% 16% 2	1416
	21st to end	Night	46% 4 15% 20% 13% 1	1551
June	1st to 10th	Night	53% 5% 13% 19% 9% 1	1440
	11th to 20th	Night	47% 5% 13% 21% 14% 1	1440
	21st to end	Night	50% 5% 14% 22% 9%	1440
July	1st to 10th	Night	38% 6% 15% 27% 14%	1400
	11th to 20th	Night	39% 4 16% 32% 9%	1392
	21st to end	Night	42% 6% 16% 24% 10% 1	1486
August	1st to 10th	Night	40% 4 20% 27% 9%	1422
	11th to 20th	Night	45% 3 16% 25% 11% 1	1651
	21st to end	Night	45% 4 15% 26% 10%	1980
September	1st to 10th	Night	46% 5% 12% 27% 11% 1	1800
	11th to 20th	Night	40% 3 12% 33% 11% 1	1857
	21st to end	Night	45% 4 13% 26% 12% 1	1980
October	1st to 10th	Night	53% 3 11% 21% 10% 1	2124
	11th to 20th	Night	58% 4 13% 16% 8% 1	2161
	21st to end	Night	67% 2 11% 12% 6% 1	2574
November	1st to 10th	Night	61% 3 11% 14% 8% 1	2407
	11th to 20th	Night	62% 4 10% 14% 7% 3	2541
	21st to end	Night	71% 3 9% 11% 5% 1	2660
December	1st to 10th	Night	79% 2 7% 9% 2	2660
	11th to 20th	Night	74% 3 6% 10% 6%	3288
	21st to end	Night	77% 2 7% 10% 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	32% 21% 27% 16% 4 1	180
	11th to 20th	Day	32% 26% 30% 11% 1 1	180
	21st to end	Day	28% 24% 35% 11% 1	202
February	1st to 10th	Day	46% 29% 22% 3 1	240
	11th to 20th	Day	37% 26% 31% 5% 1	325
	21st to end	Day	38% 23% 29% 8% 2	346
March	1st to 10th	Day	33% 25% 27% 12% 3	420
	11th to 20th	Day	31% 24% 32% 9% 3 1	420
	21st to end	Day	37% 18% 26% 12% 6% 1	462
April	1st to 10th	Day	35% 21% 26% 12% 5%	420
	11th to 20th	Day	38% 14% 26% 15% 5% 2	412
	21st to end	Day	40% 16% 26% 10% 5% 1	420
May	1st to 10th	Day	38% 14% 29% 11% 6% 2	423
	11th to 20th	Day	27% 19% 29% 18% 5% 2	447
	21st to end	Day	26% 17% 29% 19% 8%	485
June	1st to 10th	Day	36% 13% 29% 16% 6% 1	450
	11th to 20th	Day	26% 14% 31% 19% 8% 2	450
	21st to end	Day	28% 14% 32% 18% 6% 2	450
July	1st to 10th	Day	22% 9% 33% 24% 11% 1	445
	11th to 20th	Day	22% 11% 34% 24% 7% 2	444
	21st to end	Day	19% 10% 40% 23% 6% 2	488
August	1st to 10th	Day	22% 12% 28% 24% 11% 3	446
	11th to 20th	Day	21% 7% 34% 22% 11% 5%	439
	21st to end	Day	26% 13% 27% 20% 9% 5%	495
September	1st to 10th	Day	23% 10% 32% 17% 13% 6%	450
	11th to 20th	Day	23% 10% 24% 20% 15% 7%	450
	21st to end	Day	22% 13% 29% 23% 9% 4	450
October	1st to 10th	Day	33% 13% 22% 17% 10% 5%	450
	11th to 20th	Day	34% 20% 25% 13% 7% 1	448
	21st to end	Day	42% 16% 23% 15% 4	396
November	1st to 10th	Day	36% 16% 26% 15% 5%	365
	11th to 20th	Day	41% 23% 20% 10% 4 1	294
	21st to end	Day	38% 20% 30% 10% 2	180
December	1st to 10th	Day	37% 19% 32% 9% 3	180
	11th to 20th	Day	44% 23% 26% 6% 1 1	180
	21st to end	Day	42% 22% 23% 10% 3 1	198
January	1st to 10th	Night	31% 25% 30% 12% 2	760
	11th to 20th	Night	32% 26% 26% 12% 3 1	760
	21st to end	Night	22% 27% 28% 18% 5% 1	835
February	1st to 10th	Night	28% 26% 31% 13% 2	720
	11th to 20th	Night	28% 29% 29% 14% 1	703
	21st to end	Night	29% 22% 31% 15% 2	592
March	1st to 10th	Night	31% 22% 26% 17% 3 1	720
	11th to 20th	Night	31% 23% 26% 16% 4 1	720
	21st to end	Night	30% 20% 24% 19% 7% 1	792
April	1st to 10th	Night	32% 18% 27% 20% 3	720
	11th to 20th	Night	32% 21% 22% 18% 8%	711
	21st to end	Night	32% 15% 28% 18% 6% 1	617
May	1st to 10th	Night	34% 11% 26% 21% 7% 1	407
	11th to 20th	Night	27% 11% 30% 23% 8% 1	354
	21st to end	Night	19% 13% 31% 26% 11% 1	389
June	1st to 10th	Night	29% 10% 28% 25% 8% 1	360
	11th to 20th	Night	24% 7% 29% 27% 12% 1	360
	21st to end	Night	24% 8% 29% 28% 10% 1	360
July	1st to 10th	Night	13% 10% 26% 38% 14%	350
	11th to 20th	Night	14% 5% 29% 35% 16% 1	348
	21st to end	Night	18% 6% 31% 33% 11% 1	394
August	1st to 10th	Night	17% 7% 24% 34% 17% 2	358
	11th to 20th	Night	21% 3 23% 32% 20% 2	587
	21st to end	Night	21% 7% 28% 29% 13% 2	792
September	1st to 10th	Night	21% 9% 26% 29% 13% 1	720
	11th to 20th	Night	22% 8% 22% 29% 19% 2	720
	21st to end	Night	25% 12% 23% 22% 18% 1	720
October	1st to 10th	Night	30% 13% 24% 19% 13% 1	720
	11th to 20th	Night	32% 16% 25% 19% 7% 1	720
	21st to end	Night	40% 17% 21% 19% 3	792
November	1st to 10th	Night	35% 17% 26% 15% 6% 1	740
	11th to 20th	Night	33% 23% 22% 13% 7% 2	760
	21st to end	Night	34% 23% 23% 14% 5% 1	760
December	1st to 10th	Night	38% 22% 24% 13% 3	760
	11th to 20th	Night	33% 26% 22% 13% 4 1	760
	21st to end	Night	37% 24% 25% 11% 3	836

Page generated at 2024-01-28 05:26:37. Version ac07

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