Tripp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tripp 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	10% 7% 2 7% 4 4 4 3 5% 7% 46%	105039
	Night	9% 7% 2 7% 4 4 4 3 5% 7% 47%	102751
Transparency	Day	37% 6% 14% 25% 15% 2	104790
	Night	36% 6% 13% 25% 17% 3	102590
Seeing	Day	14% 10% 31% 30% 13% 2	15935
	Night	12% 9% 35% 34% 10% 1	25825

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	7% 11% 5% 12% 7% 7% 6% 4 4 6% 30%	2538
	11th to 20th	Day	5% 11% 5% 13% 6% 5% 7% 4 7% 6% 31%	2540
	21st to end	Day	6% 10% 5% 13% 6% 5% 5% 3 5% 6% 36%	3076
February	1st to 10th	Day	10% 10% 4 9% 7% 5% 5% 4 5% 6% 34%	1710
	11th to 20th	Day	8% 10% 4 9% 6% 6% 4 4 6% 6% 38%	1756
	21st to end	Day	10% 9% 3 9% 5% 5% 4 4 6% 6% 39%	1570
March	1st to 10th	Day	9% 9% 3 9% 4 3 3 2 4 7% 47%	3223
	11th to 20th	Day	9% 7% 2 7% 4 4 3 3 6% 7% 49%	3480
	21st to end	Day	23% 11% 4 11% 6% 3 4 3 5% 5% 25%	3814
April	1st to 10th	Day	16% 7% 2 7% 4 4 4 3 6% 7% 41%	2171
	11th to 20th	Day	18% 8% 3 6% 4 3 4 3 4 6% 41%	2434
	21st to end	Day	18% 7% 2 7% 4 4 4 3 5% 6% 40%	2470
May	1st to 10th	Day	14% 7% 2 7% 4 4 5% 4 7% 7% 38%	4120
	11th to 20th	Day	11% 6% 2 6% 4 4 3 3 5% 6% 50%	4082
	21st to end	Day	17% 7% 2 6% 4 4 4 4 5% 8% 40%	4590
June	1st to 10th	Day	10% 4 2 5% 4 4 3 4 6% 8% 50%	2850
	11th to 20th	Day	13% 5% 2 4 3 4 5% 4 6% 8% 46%	2850
	21st to end	Day	7% 5% 2 5% 3 4 4 4 6% 9% 52%	2850
July	1st to 10th	Day	10% 4 2 5% 4 5% 5% 5% 7% 9% 45%	4466
	11th to 20th	Day	6% 4 1 4 3 3 3 4 6% 8% 58%	4430
	21st to end	Day	4 4 1 4 3 4 4 4 6% 9% 55%	4540
August	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 8% 49%	4103
	11th to 20th	Day	16% 7% 2 6% 4 3 4 3 6% 8% 40%	4041
	21st to end	Day	7% 4 2 5% 3 4 4 3 5% 7% 56%	4532
September	1st to 10th	Day	12% 5% 1 4 3 2 3 3 5% 6% 55%	2174
	11th to 20th	Day	8% 4 1 4 2 3 4 3 4 6% 59%	2090
	21st to end	Day	10% 4 2 4 3 3 3 3 5% 6% 57%	2090
October	1st to 10th	Day	8% 3 1 3 3 2 3 2 4 5% 65%	3336
	11th to 20th	Day	7% 4 1 5% 3 4 3 3 5% 7% 57%	3140
	21st to end	Day	10% 7% 2 6% 4 4 4 4 5% 8% 46%	3190
November	1st to 10th	Day	7% 8% 3 6% 5% 4 5% 4 6% 6% 47%	1763
	11th to 20th	Day	6% 7% 2 8% 6% 5% 4 4 5% 7% 46%	1691
	21st to end	Day	9% 8% 3 7% 4 4 3 3 6% 7% 46%	1520
December	1st to 10th	Day	7% 9% 3 8% 6% 5% 4 4 6% 8% 41%	1520
	11th to 20th	Day	8% 9% 4 7% 6% 4 6% 5% 5% 7% 39%	1745
	21st to end	Day	15% 11% 5% 13% 6% 4 3 3 5% 4 30%	2544
January	1st to 10th	Night	7% 12% 4 11% 9% 7% 6% 4 6% 7% 28%	4417
	11th to 20th	Night	4 11% 4 9% 5% 5% 8% 5% 9% 7% 33%	4430
	21st to end	Night	4 9% 5% 14% 6% 5% 4 4 6% 7% 37%	4589
February	1st to 10th	Night	9% 10% 4 9% 6% 5% 5% 4 4 6% 38%	2470
	11th to 20th	Night	7% 10% 3 8% 5% 4 4 4 5% 6% 43%	2328
	21st to end	Night	9% 8% 3 6% 5% 4 5% 5% 6% 5% 45%	1884
March	1st to 10th	Night	8% 7% 2 6% 4 4 4 3 5% 6% 50%	3624
	11th to 20th	Night	9% 6% 2 6% 4 4 4 3 5% 8% 50%	3480
	21st to end	Night	18% 12% 3 8% 5% 4 4 3 5% 6% 30%	3817
April	1st to 10th	Night	13% 9% 3 6% 3 4 3 4 6% 7% 43%	2005
	11th to 20th	Night	14% 9% 3 6% 4 3 3 3 5% 8% 42%	1693
	21st to end	Night	14% 7% 3 5% 4 5% 4 3 6% 7% 42%	1710
May	1st to 10th	Night	16% 5% 1 5% 4 4 4 3 5% 7% 45%	2850
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 6% 8% 52%	2823
	21st to end	Night	16% 5% 2 5% 4 3 4 3 5% 8% 44%	2989
June	1st to 10th	Night	7% 4 1 5% 4 2 3 2 5% 8% 56%	1330
	11th to 20th	Night	9% 5% 1 4 3 4 4 4 7% 9% 51%	1330
	21st to end	Night	7% 3 1 3 3 4 5% 4 5% 9% 57%	1330
July	1st to 10th	Night	7% 6% 2 5% 4 4 4 4 6% 8% 52%	2498
	11th to 20th	Night	4 3 1 3 3 3 4 3 5% 7% 64%	2540
	21st to end	Night	2 2 1 4 3 3 4 4 7% 10% 61%	3020
August	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 7% 10% 49%	2836
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 5% 7% 48%	2798
	21st to end	Night	6% 3 2 5% 3 3 4 3 6% 8% 56%	3135
September	1st to 10th	Night	8% 4 2 3 3 3 3 3 4 7% 58%	2001
	11th to 20th	Night	7% 4 1 4 2 3 4 3 5% 6% 61%	2090
	21st to end	Night	9% 4 1 4 3 3 3 2 4 6% 62%	2090
October	1st to 10th	Night	9% 3 1 2 2 2 2 2 3 4 71%	3590
	11th to 20th	Night	7% 4 2 4 2 2 3 2 4 7% 62%	3779
	21st to end	Night	10% 6% 2 5% 5% 4 4 4 5% 7% 48%	4363
November	1st to 10th	Night	9% 5% 1 5% 4 4 3 3 5% 7% 54%	2535
	11th to 20th	Night	7% 7% 2 7% 5% 5% 4 4 5% 7% 47%	2492
	21st to end	Night	7% 8% 2 6% 4 4 4 4 6% 7% 49%	2660
December	1st to 10th	Night	8% 7% 3 9% 4 5% 5% 4 6% 6% 43%	2660
	11th to 20th	Night	6% 8% 3 7% 5% 4 4 3 6% 8% 45%	3447
	21st to end	Night	16% 11% 4 12% 5% 4 3 3 3 5% 33%	5118

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	55% 6% 13% 18% 8%	2539
	11th to 20th	Day	52% 5% 13% 22% 8%	2540
	21st to end	Day	49% 6% 18% 16% 11%	3076
February	1st to 10th	Day	49% 7% 16% 19% 9% 1	1710
	11th to 20th	Day	45% 6% 12% 22% 12% 2	1765
	21st to end	Day	45% 6% 15% 20% 12% 2	1570
March	1st to 10th	Day	38% 5% 11% 28% 16% 2	3223
	11th to 20th	Day	35% 6% 12% 29% 16% 3	3480
	21st to end	Day	61% 7% 15% 14% 3 1	3814
April	1st to 10th	Day	42% 6% 13% 26% 13% 1	2171
	11th to 20th	Day	44% 5% 12% 22% 15% 2	2437
	21st to end	Day	44% 6% 12% 25% 12%	2470
May	1st to 10th	Day	42% 6% 12% 23% 16%	4120
	11th to 20th	Day	34% 6% 12% 29% 16% 3	4086
	21st to end	Day	42% 7% 13% 24% 13% 1	4590
June	1st to 10th	Day	31% 8% 16% 30% 12% 2	2850
	11th to 20th	Day	34% 8% 15% 23% 17% 3	2850
	21st to end	Day	28% 8% 16% 30% 16% 2	2850
July	1st to 10th	Day	33% 9% 18% 27% 12% 2	4397
	11th to 20th	Day	24% 6% 12% 34% 20% 4	4355
	21st to end	Day	22% 8% 17% 28% 21% 4	4396
August	1st to 10th	Day	30% 8% 14% 29% 14% 4	4090
	11th to 20th	Day	42% 7% 13% 25% 12% 1	4080
	21st to end	Day	27% 7% 17% 26% 20% 4	4531
September	1st to 10th	Day	30% 6% 11% 29% 20% 4	2174
	11th to 20th	Day	27% 5% 14% 33% 19% 1	2090
	21st to end	Day	28% 5% 11% 30% 23% 2	2090
October	1st to 10th	Day	22% 4 8% 23% 38% 5%	3336
	11th to 20th	Day	27% 4 14% 30% 20% 5%	3140
	21st to end	Day	36% 5% 12% 26% 19% 3	3190
November	1st to 10th	Day	36% 7% 16% 24% 15% 2	1763
	11th to 20th	Day	39% 6% 14% 26% 14% 1	1691
	21st to end	Day	37% 4 16% 27% 14% 1	1520
December	1st to 10th	Day	42% 6% 16% 23% 10% 2	1520
	11th to 20th	Day	43% 6% 19% 25% 7%	1742
	21st to end	Day	57% 4 10% 23% 5% 1	2544
January	1st to 10th	Night	54% 7% 12% 18% 8% 1	4417
	11th to 20th	Night	46% 8% 13% 24% 7% 2	4430
	21st to end	Night	45% 8% 17% 19% 10%	4589
February	1st to 10th	Night	46% 6% 14% 20% 12% 1	2470
	11th to 20th	Night	42% 5% 15% 22% 13% 4	2329
	21st to end	Night	39% 7% 13% 25% 13% 3	1884
March	1st to 10th	Night	34% 5% 12% 24% 23% 2	3624
	11th to 20th	Night	33% 4 10% 30% 20% 3	3480
	21st to end	Night	52% 9% 15% 18% 5% 1	3817
April	1st to 10th	Night	40% 6% 14% 24% 15% 1	2005
	11th to 20th	Night	40% 6% 10% 23% 20% 2	1693
	21st to end	Night	40% 7% 13% 25% 13% 2	1710
May	1st to 10th	Night	37% 6% 15% 21% 18% 4	2850
	11th to 20th	Night	29% 8% 12% 27% 23% 2	2824
	21st to end	Night	37% 8% 13% 25% 16% 1	2990
June	1st to 10th	Night	26% 8% 15% 30% 19% 3	1330
	11th to 20th	Night	28% 8% 14% 25% 21% 5%	1330
	21st to end	Night	24% 7% 15% 32% 20% 3	1330
July	1st to 10th	Night	30% 7% 21% 25% 13% 4	2458
	11th to 20th	Night	20% 6% 12% 36% 21% 5%	2492
	21st to end	Night	17% 8% 18% 31% 22% 4	2925
August	1st to 10th	Night	29% 7% 17% 30% 14% 3	2826
	11th to 20th	Night	34% 8% 15% 27% 15% 2	2825
	21st to end	Night	25% 7% 17% 24% 22% 5%	3135
September	1st to 10th	Night	26% 7% 11% 27% 22% 6%	2001
	11th to 20th	Night	23% 7% 12% 35% 22% 2	2090
	21st to end	Night	25% 4 9% 30% 27% 4	2090
October	1st to 10th	Night	20% 3 6% 18% 47% 6%	3590
	11th to 20th	Night	23% 3 10% 33% 24% 6%	3779
	21st to end	Night	34% 5% 14% 26% 20% 1	4363
November	1st to 10th	Night	30% 5% 14% 25% 21% 5%	2535
	11th to 20th	Night	35% 5% 13% 24% 19% 3	2492
	21st to end	Night	33% 6% 14% 28% 17% 1	2660
December	1st to 10th	Night	41% 6% 14% 27% 11% 1	2660
	11th to 20th	Night	38% 5% 16% 33% 8%	3449
	21st to end	Night	55% 5% 11% 21% 8%	5118

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	15% 11% 33% 27% 13% 1	270
	11th to 20th	Day	13% 15% 38% 27% 7%	270
	21st to end	Day	13% 10% 43% 23% 8% 1	297
February	1st to 10th	Day	12% 19% 40% 25% 4	270
	11th to 20th	Day	15% 13% 43% 21% 6% 1	270
	21st to end	Day	14% 15% 40% 28% 4	225
March	1st to 10th	Day	13% 14% 41% 26% 5% 1	270
	11th to 20th	Day	19% 8% 38% 24% 10% 1	270
	21st to end	Day	25% 12% 33% 24% 6% 1	297
April	1st to 10th	Day	23% 18% 38% 17% 4	351
	11th to 20th	Day	22% 16% 30% 25% 6%	635
	21st to end	Day	22% 14% 30% 23% 9% 2	650
May	1st to 10th	Day	18% 14% 32% 27% 9% 1	653
	11th to 20th	Day	19% 11% 29% 26% 14% 2	675
	21st to end	Day	18% 10% 30% 27% 12% 3	734
June	1st to 10th	Day	10% 7% 26% 33% 20% 5%	680
	11th to 20th	Day	13% 6% 36% 29% 14% 2	680
	21st to end	Day	10% 7% 29% 35% 17% 2	680
July	1st to 10th	Day	8% 3 22% 38% 26% 4	671
	11th to 20th	Day	6% 4 26% 44% 19% 2	668
	21st to end	Day	5% 3 25% 45% 19% 3	739
August	1st to 10th	Day	9% 3 25% 40% 20% 3	676
	11th to 20th	Day	10% 5% 24% 38% 19% 4	665
	21st to end	Day	7% 3 28% 39% 19% 3	748
September	1st to 10th	Day	14% 5% 31% 30% 17% 4	384
	11th to 20th	Day	7% 7% 37% 27% 18% 4	300
	21st to end	Day	16% 10% 31% 26% 14% 3	300
October	1st to 10th	Day	17% 5% 28% 31% 15% 4	300
	11th to 20th	Day	16% 13% 37% 25% 8% 1	300
	21st to end	Day	18% 17% 37% 20% 8% 1	330
November	1st to 10th	Day	17% 15% 34% 23% 9% 3	300
	11th to 20th	Day	11% 18% 40% 26% 6%	270
	21st to end	Day	20% 17% 30% 24% 9%	270
December	1st to 10th	Day	13% 10% 38% 29% 10% 1	270
	11th to 20th	Day	13% 14% 41% 25% 7%	270
	21st to end	Day	22% 14% 35% 24% 4	297
January	1st to 10th	Night	11% 11% 37% 31% 8% 1	950
	11th to 20th	Night	10% 14% 37% 31% 6% 1	950
	21st to end	Night	13% 9% 42% 28% 7%	1045
February	1st to 10th	Night	15% 12% 40% 27% 6%	950
	11th to 20th	Night	12% 11% 40% 30% 6% 1	854
	21st to end	Night	15% 9% 37% 31% 8% 1	628
March	1st to 10th	Night	13% 11% 41% 28% 6%	702
	11th to 20th	Night	14% 10% 40% 30% 5%	570
	21st to end	Night	19% 10% 38% 26% 7%	627
April	1st to 10th	Night	16% 15% 38% 28% 3	570
	11th to 20th	Night	18% 13% 33% 29% 6%	563
	21st to end	Night	17% 10% 39% 27% 6% 1	570
May	1st to 10th	Night	16% 9% 36% 29% 9%	570
	11th to 20th	Night	16% 8% 32% 33% 11%	561
	21st to end	Night	19% 6% 32% 34% 9%	617
June	1st to 10th	Night	9% 5% 29% 41% 15% 1	570
	11th to 20th	Night	10% 3 35% 41% 10%	570
	21st to end	Night	6% 4 29% 46% 15%	570
July	1st to 10th	Night	6% 3 21% 46% 22% 1	555
	11th to 20th	Night	5% 1 25% 52% 17%	552
	21st to end	Night	3 2 24% 54% 16%	624
August	1st to 10th	Night	8% 5% 24% 44% 19%	567
	11th to 20th	Night	8% 2 26% 44% 19% 1	564
	21st to end	Night	6% 3 29% 44% 16% 1	627
September	1st to 10th	Night	10% 5% 27% 42% 14% 2	570
	11th to 20th	Night	7% 5% 31% 41% 14% 2	570
	21st to end	Night	10% 9% 34% 33% 14% 1	570
October	1st to 10th	Night	18% 8% 31% 32% 10% 1	628
	11th to 20th	Night	14% 12% 34% 31% 8%	760
	21st to end	Night	15% 10% 36% 30% 8%	978
November	1st to 10th	Night	12% 10% 37% 32% 8% 1	975
	11th to 20th	Night	11% 12% 39% 29% 8% 1	953
	21st to end	Night	11% 11% 37% 31% 8%	950
December	1st to 10th	Night	12% 12% 40% 30% 6%	950
	11th to 20th	Night	13% 9% 38% 33% 8%	950
	21st to end	Night	19% 12% 34% 28% 6% 1	1045

Page generated at 2024-11-08 05:44:47. Version ac07

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