Tranquility Gate Observatory
Clear Sky Chart
History

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

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% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	101140
	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 32%	97935
Transparency	Day	50% 7% 12% 19% 10% 1	104803
	Night	50% 7% 11% 19% 11% 2	102411
Seeing	Day	21% 14% 28% 21% 11% 4	14670
	Night	21% 11% 27% 27% 12% 1	24391

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	19% 22% 8% 12% 5% 4 4 2 4 5% 16%	2836
	11th to 20th	Day	13% 25% 8% 13% 6% 5% 4 2 3 5% 16%	2840
	21st to end	Day	26% 20% 9% 13% 6% 4 3 2 3 4 10%	3124
February	1st to 10th	Day	19% 19% 4 11% 8% 5% 4 2 3 4 21%	1710
	11th to 20th	Day	16% 14% 6% 14% 6% 5% 5% 3 4 5% 21%	1667
	21st to end	Day	19% 15% 5% 11% 5% 4 4 3 5% 6% 24%	1570
March	1st to 10th	Day	21% 12% 5% 10% 4 4 4 2 5% 5% 27%	3429
	11th to 20th	Day	13% 11% 5% 10% 6% 5% 4 4 4 5% 33%	3480
	21st to end	Day	20% 11% 4 9% 5% 4 4 3 5% 6% 29%	3815
April	1st to 10th	Day	14% 14% 3 8% 5% 3 5% 3 6% 7% 30%	2166
	11th to 20th	Day	16% 12% 3 7% 5% 4 4 4 6% 7% 32%	2340
	21st to end	Day	20% 11% 3 8% 5% 4 4 3 4 6% 33%	2470
May	1st to 10th	Day	22% 9% 3 8% 5% 5% 5% 4 5% 7% 28%	4082
	11th to 20th	Day	19% 9% 3 8% 4 5% 5% 4 6% 7% 31%	4081
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	4666
June	1st to 10th	Day	14% 7% 3 8% 6% 5% 5% 4 6% 9% 34%	2660
	11th to 20th	Day	13% 7% 2 7% 5% 5% 5% 4 6% 10% 35%	2660
	21st to end	Day	12% 6% 3 5% 5% 5% 5% 5% 8% 10% 37%	2660
July	1st to 10th	Day	8% 6% 3 7% 4 5% 5% 5% 6% 10% 40%	4248
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	4120
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 4 7% 8% 36%	4466
August	1st to 10th	Day	15% 8% 3 8% 5% 6% 6% 5% 7% 8% 31%	4104
	11th to 20th	Day	12% 7% 3 6% 5% 6% 6% 5% 8% 9% 33%	4044
	21st to end	Day	8% 5% 2 8% 5% 6% 5% 5% 7% 9% 39%	4377
September	1st to 10th	Day	14% 7% 2 7% 4 4 4 3 5% 6% 44%	2242
	11th to 20th	Day	10% 6% 3 6% 4 4 5% 4 6% 8% 44%	2090
	21st to end	Day	19% 8% 3 7% 5% 4 4 4 5% 6% 35%	2090
October	1st to 10th	Day	15% 6% 2 6% 5% 4 5% 4 6% 7% 38%	1924
	11th to 20th	Day	18% 10% 3 8% 5% 5% 4 3 5% 6% 33%	1900
	21st to end	Day	21% 12% 3 7% 4 4 4 3 4 7% 30%	2090
November	1st to 10th	Day	11% 9% 4 7% 5% 5% 4 3 4 7% 41%	1815
	11th to 20th	Day	16% 14% 4 8% 5% 5% 4 3 5% 6% 30%	1616
	21st to end	Day	16% 16% 6% 10% 5% 5% 4 4 5% 5% 24%	1520
December	1st to 10th	Day	21% 18% 6% 11% 6% 4 3 4 5% 4 18%	1520
	11th to 20th	Day	18% 18% 8% 12% 5% 4 4 4 5% 6% 18%	1910
	21st to end	Day	25% 24% 7% 11% 5% 3 3 3 3 4 12%	2808
January	1st to 10th	Night	16% 21% 9% 13% 6% 4 4 3 4 5% 16%	4109
	11th to 20th	Night	15% 20% 8% 16% 6% 5% 5% 3 4 4 14%	4120
	21st to end	Night	27% 17% 9% 12% 6% 3 3 2 3 3 14%	4532
February	1st to 10th	Night	20% 15% 5% 10% 7% 5% 4 4 4 5% 22%	2470
	11th to 20th	Night	17% 14% 6% 12% 6% 5% 4 4 4 5% 23%	2397
	21st to end	Night	19% 15% 6% 11% 5% 4 4 3 4 5% 24%	1884
March	1st to 10th	Night	23% 13% 3 8% 4 3 3 3 3 5% 32%	3423
	11th to 20th	Night	17% 11% 5% 8% 5% 4 4 3 5% 6% 32%	3480
	21st to end	Night	18% 11% 3 7% 4 4 4 3 4 5% 37%	3817
April	1st to 10th	Night	16% 12% 4 7% 4 5% 4 4 5% 6% 33%	2014
	11th to 20th	Night	16% 9% 3 7% 5% 5% 5% 3 6% 6% 34%	1805
	21st to end	Night	16% 8% 4 7% 5% 4 4 4 6% 8% 35%	1710
May	1st to 10th	Night	25% 10% 3 7% 4 4 4 4 5% 7% 28%	2813
	11th to 20th	Night	16% 9% 3 7% 4 4 4 3 5% 8% 36%	2812
	21st to end	Night	9% 6% 2 5% 4 4 4 5% 8% 11% 44%	2871
June	1st to 10th	Night	9% 6% 2 6% 5% 5% 5% 4 7% 6% 43%	1520
	11th to 20th	Night	9% 6% 3 6% 5% 4 6% 4 5% 8% 43%	1520
	21st to end	Night	10% 4 3 6% 5% 6% 5% 4 7% 8% 42%	1520
July	1st to 10th	Night	10% 7% 3 7% 5% 5% 5% 4 5% 8% 42%	2706
	11th to 20th	Night	10% 5% 2 5% 4 5% 4 4 6% 10% 46%	2840
	21st to end	Night	8% 6% 3 6% 5% 5% 4 4 7% 8% 43%	3087
August	1st to 10th	Night	12% 8% 3 8% 5% 5% 4 4 6% 7% 37%	2825
	11th to 20th	Night	12% 8% 2 8% 4 3 4 3 5% 7% 43%	2785
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 44%	3245
September	1st to 10th	Night	13% 5% 2 5% 4 3 3 3 5% 7% 49%	1933
	11th to 20th	Night	10% 5% 2 4 3 4 4 4 6% 8% 51%	2090
	21st to end	Night	18% 7% 2 6% 4 3 4 3 5% 7% 40%	2090
October	1st to 10th	Night	14% 6% 2 6% 4 4 4 4 5% 7% 45%	2255
	11th to 20th	Night	16% 7% 3 7% 5% 4 4 4 6% 8% 36%	2280
	21st to end	Night	22% 9% 3 5% 5% 4 4 3 5% 7% 34%	2508
November	1st to 10th	Night	13% 9% 2 5% 4 5% 4 3 5% 7% 43%	2466
	11th to 20th	Night	16% 14% 4 7% 5% 4 4 3 5% 6% 31%	2560
	21st to end	Night	19% 15% 4 8% 5% 4 4 3 4 6% 28%	2660
December	1st to 10th	Night	21% 16% 5% 11% 6% 5% 4 4 4 5% 20%	2660
	11th to 20th	Night	17% 20% 6% 10% 5% 5% 3 3 5% 5% 21%	3285
	21st to end	Night	25% 20% 7% 11% 6% 5% 4 3 5% 4 12%	4843

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	70% 6% 9% 11% 3	2837
	11th to 20th	Day	71% 5% 9% 11% 3	2840
	21st to end	Day	79% 6% 7% 6% 2	3124
February	1st to 10th	Day	68% 4 9% 12% 6%	1710
	11th to 20th	Day	65% 7% 8% 13% 7%	1676
	21st to end	Day	61% 6% 11% 14% 7% 1	1570
March	1st to 10th	Day	57% 7% 11% 20% 5%	3429
	11th to 20th	Day	50% 9% 13% 21% 7% 1	3480
	21st to end	Day	53% 7% 11% 17% 11% 1	3815
April	1st to 10th	Day	51% 7% 11% 17% 12% 1	2166
	11th to 20th	Day	50% 7% 11% 17% 13% 2	2340
	21st to end	Day	51% 6% 12% 20% 9% 2	2470
May	1st to 10th	Day	53% 9% 10% 18% 8% 1	4120
	11th to 20th	Day	49% 9% 13% 19% 9% 1	4085
	21st to end	Day	37% 11% 14% 21% 13% 4	4680
June	1st to 10th	Day	45% 9% 13% 22% 11% 1	2660
	11th to 20th	Day	43% 9% 13% 21% 13% 1	2660
	21st to end	Day	40% 10% 13% 24% 13% 1	2660
July	1st to 10th	Day	39% 8% 13% 23% 14% 3	4183
	11th to 20th	Day	37% 7% 12% 26% 17% 1	4051
	21st to end	Day	42% 8% 13% 19% 17% 1	4324
August	1st to 10th	Day	48% 8% 14% 21% 9%	4091
	11th to 20th	Day	43% 7% 13% 28% 8% 1	4083
	21st to end	Day	39% 8% 13% 26% 12% 2	4377
September	1st to 10th	Day	40% 7% 12% 21% 18% 3	2242
	11th to 20th	Day	36% 8% 14% 25% 16% 1	2090
	21st to end	Day	47% 8% 11% 21% 11% 1	2090
October	1st to 10th	Day	33% 6% 13% 28% 19% 1	3197
	11th to 20th	Day	47% 5% 10% 19% 14% 4	3140
	21st to end	Day	40% 6% 12% 26% 15%	3428
November	1st to 10th	Day	42% 7% 12% 21% 16% 2	1815
	11th to 20th	Day	54% 7% 12% 17% 8% 3	1616
	21st to end	Day	60% 6% 12% 15% 6% 1	1520
December	1st to 10th	Day	69% 7% 10% 11% 3	1520
	11th to 20th	Day	67% 6% 9% 13% 3	1906
	21st to end	Day	77% 5% 9% 7% 2	2808
January	1st to 10th	Night	69% 7% 11% 10% 3	4109
	11th to 20th	Night	73% 7% 9% 9% 2	4120
	21st to end	Night	77% 4 6% 11% 2	4532
February	1st to 10th	Night	64% 6% 10% 15% 5%	2470
	11th to 20th	Night	63% 5% 10% 16% 6%	2399
	21st to end	Night	62% 6% 9% 14% 8% 1	1884
March	1st to 10th	Night	55% 5% 10% 21% 8%	3423
	11th to 20th	Night	50% 7% 16% 19% 6% 1	3480
	21st to end	Night	47% 7% 12% 21% 12% 1	3817
April	1st to 10th	Night	50% 7% 11% 17% 13% 2	2014
	11th to 20th	Night	48% 7% 13% 16% 14% 3	1805
	21st to end	Night	44% 8% 13% 19% 13% 2	1710
May	1st to 10th	Night	54% 8% 9% 18% 10% 2	2840
	11th to 20th	Night	44% 9% 11% 23% 10% 2	2813
	21st to end	Night	29% 11% 17% 26% 14% 4	2878
June	1st to 10th	Night	37% 9% 13% 23% 15% 2	1520
	11th to 20th	Night	37% 8% 15% 22% 16% 2	1520
	21st to end	Night	37% 9% 12% 24% 16% 1	1520
July	1st to 10th	Night	41% 6% 10% 22% 18% 2	2661
	11th to 20th	Night	32% 8% 14% 29% 16% 1	2786
	21st to end	Night	37% 8% 13% 17% 23% 2	2988
August	1st to 10th	Night	45% 7% 12% 22% 13% 1	2814
	11th to 20th	Night	39% 6% 11% 28% 14% 1	2812
	21st to end	Night	34% 8% 12% 30% 13% 2	3245
September	1st to 10th	Night	35% 7% 11% 24% 19% 4	1933
	11th to 20th	Night	29% 8% 14% 25% 22% 2	2090
	21st to end	Night	43% 6% 13% 20% 17% 1	2090
October	1st to 10th	Night	34% 5% 10% 27% 23% 1	3762
	11th to 20th	Night	39% 7% 12% 23% 13% 7%	3779
	21st to end	Night	37% 5% 10% 30% 17% 2	4120
November	1st to 10th	Night	40% 7% 12% 23% 15% 3	2466
	11th to 20th	Night	55% 6% 11% 18% 9% 3	2560
	21st to end	Night	58% 6% 12% 19% 5% 1	2660
December	1st to 10th	Night	66% 7% 12% 11% 4	2660
	11th to 20th	Night	65% 6% 12% 14% 3	3288
	21st to end	Night	73% 8% 10% 8% 1	4843

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	30% 26% 30% 11% 3	270
	11th to 20th	Day	32% 27% 30% 9% 3	270
	21st to end	Day	28% 28% 32% 10% 2	297
February	1st to 10th	Day	30% 20% 39% 9% 1	270
	11th to 20th	Day	33% 28% 30% 9% 1	270
	21st to end	Day	34% 28% 31% 8%	225
March	1st to 10th	Day	28% 21% 31% 16% 3	454
	11th to 20th	Day	30% 17% 33% 13% 5% 1	460
	21st to end	Day	33% 19% 29% 15% 4 1	506
April	1st to 10th	Day	26% 22% 29% 14% 8% 1	460
	11th to 20th	Day	27% 16% 27% 16% 9% 4	452
	21st to end	Day	27% 16% 32% 17% 7% 1	460
May	1st to 10th	Day	27% 20% 23% 19% 8% 3	463
	11th to 20th	Day	21% 13% 32% 21% 9% 3	487
	21st to end	Day	15% 9% 25% 28% 18% 6%	529
June	1st to 10th	Day	15% 10% 33% 27% 12% 4	490
	11th to 20th	Day	18% 9% 26% 28% 14% 4	490
	21st to end	Day	14% 11% 32% 26% 13% 4	490
July	1st to 10th	Day	10% 6% 21% 32% 20% 12%	485
	11th to 20th	Day	11% 7% 28% 25% 21% 7%	484
	21st to end	Day	13% 6% 25% 30% 18% 8%	532
August	1st to 10th	Day	14% 5% 22% 29% 20% 10%	486
	11th to 20th	Day	16% 6% 23% 27% 19% 10%	479
	21st to end	Day	10% 5% 24% 29% 19% 13%	539
September	1st to 10th	Day	15% 8% 20% 26% 21% 9%	490
	11th to 20th	Day	10% 5% 19% 31% 24% 10%	490
	21st to end	Day	22% 12% 25% 21% 14% 6%	490
October	1st to 10th	Day	14% 10% 27% 25% 19% 5%	490
	11th to 20th	Day	22% 16% 32% 20% 8% 2	490
	21st to end	Day	27% 16% 30% 20% 6%	539
November	1st to 10th	Day	16% 23% 35% 14% 11% 2	359
	11th to 20th	Day	30% 20% 27% 14% 7% 1	225
	21st to end	Day	26% 23% 37% 13% 1	180
December	1st to 10th	Day	32% 27% 28% 9% 4 1	180
	11th to 20th	Day	29% 22% 34% 12% 2	180
	21st to end	Day	35% 25% 28% 10% 2	209
January	1st to 10th	Night	28% 19% 35% 15% 3	760
	11th to 20th	Night	30% 18% 33% 15% 4	760
	21st to end	Night	26% 20% 30% 20% 3	836
February	1st to 10th	Night	30% 16% 29% 23% 2	760
	11th to 20th	Night	27% 18% 38% 16% 1	743
	21st to end	Night	29% 17% 33% 18% 3	628
March	1st to 10th	Night	24% 15% 34% 23% 3	760
	11th to 20th	Night	25% 16% 29% 23% 5% 1	760
	21st to end	Night	23% 15% 34% 22% 6% 1	836
April	1st to 10th	Night	24% 14% 31% 24% 6%	760
	11th to 20th	Night	21% 13% 34% 22% 9% 1	681
	21st to end	Night	19% 9% 36% 30% 6%	570
May	1st to 10th	Night	21% 9% 26% 32% 10% 1	570
	11th to 20th	Night	20% 7% 26% 33% 13% 1	561
	21st to end	Night	10% 5% 24% 37% 22% 3	499
June	1st to 10th	Night	11% 3 28% 40% 17%	380
	11th to 20th	Night	11% 6% 22% 45% 16%	380
	21st to end	Night	9% 4 26% 37% 23%	380
July	1st to 10th	Night	8% 3 15% 43% 24% 7%	473
	11th to 20th	Night	9% 3 18% 39% 28% 4	552
	21st to end	Night	11% 3 14% 42% 29% 2	624
August	1st to 10th	Night	12% 2 15% 41% 28% 2	567
	11th to 20th	Night	14% 4 11% 40% 28% 4	564
	21st to end	Night	12% 4 17% 34% 28% 5%	696
September	1st to 10th	Night	16% 4 18% 34% 26% 4	760
	11th to 20th	Night	11% 4 15% 36% 30% 4	760
	21st to end	Night	19% 7% 24% 26% 19% 4	760
October	1st to 10th	Night	17% 8% 22% 31% 20% 2	760
	11th to 20th	Night	20% 12% 31% 26% 10% 1	760
	21st to end	Night	28% 11% 28% 26% 7%	836
November	1st to 10th	Night	19% 11% 28% 30% 12%	779
	11th to 20th	Night	26% 16% 29% 21% 7% 1	760
	21st to end	Night	28% 16% 30% 21% 5%	760
December	1st to 10th	Night	32% 17% 28% 19% 4	760
	11th to 20th	Night	28% 18% 30% 20% 4	760
	21st to end	Night	30% 18% 31% 19% 2	836

Page generated at 2024-11-07 06:55:50. Version ac07

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