Conway Summit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Conway Summit 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	1 3 1 4 3 3 3 3 5% 7% 68%	105105
	Night	1 3 1 3 2 2 3 3 5% 7% 70%	102799
Transparency	Day	15% 8% 11% 19% 26% 22%	104850
	Night	13% 7% 12% 22% 27% 18%	102645
Seeing	Day	4 13% 27% 29% 19% 7%	15153
	Night	2 6% 26% 37% 24% 5%	24603

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	2 2 3 2 3 3 3 6% 12% 65%	2539
	11th to 20th	Day	2 1 3 4 4 5% 5% 9% 12% 56%	2605
	21st to end	Day	1 5% 2 6% 4 4 5% 4 8% 10% 52%	3146
February	1st to 10th	Day	3 1 5% 3 2 4 4 5% 8% 66%	1799
	11th to 20th	Day	3 1 5% 4 3 4 3 8% 9% 60%	1850
	21st to end	Day	2 2 4 3 3 4 3 6% 8% 65%	1570
March	1st to 10th	Day	3 2 7% 4 5% 5% 4 8% 10% 52%	3138
	11th to 20th	Day	3 3 7% 2 3 3 3 5% 9% 62%	3356
	21st to end	Day	4 3 7% 3 3 4 4 6% 9% 56%	4125
April	1st to 10th	Day	1 3 2 5% 3 3 4 4 7% 9% 59%	2280
	11th to 20th	Day	1 3 1 3 3 3 4 3 7% 8% 63%	2249
	21st to end	Day	1 3 1 4 3 2 3 4 5% 7% 66%	2280
May	1st to 10th	Day	1 3 1 2 2 2 3 2 4 6% 73%	4007
	11th to 20th	Day	2 3 1 3 2 3 3 3 5% 5% 71%	4118
	21st to end	Day	2 4 2 4 3 3 3 2 4 6% 67%	4813
June	1st to 10th	Day	3 3 2 3 3 3 4 4 6% 6% 63%	2660
	11th to 20th	Day	1 1 1 3 2 2 3 2 4 4 77%	2660
	21st to end	Day	2 3 1 3 2 3 2 3 4 4 73%	2660
July	1st to 10th	Day	1 2 1 2 2 2 2 2 3 3 81%	4420
	11th to 20th	Day	4 5% 2 6% 3 4 4 4 4 5% 59%	4420
	21st to end	Day	3 4 1 4 3 3 3 3 4 5% 66%	4700
August	1st to 10th	Day	4 4 1 4 3 3 4 3 3 5% 66%	3906
	11th to 20th	Day	2 2 1 2 1 1 2 2 2 3 82%	3724
	21st to end	Day	1 2 1 2 1 2 2 1 2 4 83%	4180
September	1st to 10th	Day	2 3 1 3 2 2 2 2 3 3 76%	2280
	11th to 20th	Day	2 2 1 3 2 2 3 2 4 5% 73%	2211
	21st to end	Day	1 2 1 2 2 2 3 2 3 5% 77%	2090
October	1st to 10th	Day	2 3 1 3 2 2 3 3 4 5% 72%	3344
	11th to 20th	Day	1 2 1 2 1 1 2 1 2 4 81%	3161
	21st to end	Day	2 1 2 2 2 2 2 4 6% 77%	3331
November	1st to 10th	Day	1 1 4 3 4 3 2 6% 8% 69%	1764
	11th to 20th	Day	1 1 2 1 2 2 3 5% 10% 72%	1710
	21st to end	Day	1 2 1 2 2 2 3 3 6% 9% 70%	1710
December	1st to 10th	Day	1 2 1 3 1 2 3 3 6% 10% 67%	1577
	11th to 20th	Day	1 4 2 6% 4 5% 4 4 7% 9% 54%	1928
	21st to end	Day	6% 2 6% 3 3 4 4 8% 12% 51%	2794
January	1st to 10th	Night	2 2 5% 3 3 3 3 6% 10% 63%	4406
	11th to 20th	Night	2 1 4 3 3 4 5% 9% 11% 58%	4354
	21st to end	Night	1 4 2 5% 4 4 4 4 8% 10% 54%	4521
February	1st to 10th	Night	3 1 6% 3 4 4 3 6% 9% 61%	2379
	11th to 20th	Night	1 3 1 4 3 3 4 3 6% 10% 64%	2218
	21st to end	Night	3 1 4 3 2 4 3 7% 9% 65%	1884
March	1st to 10th	Night	3 2 5% 4 4 5% 4 7% 8% 58%	3736
	11th to 20th	Night	4 2 5% 3 2 3 3 5% 9% 63%	3620
	21st to end	Night	3 2 6% 3 3 5% 4 7% 9% 59%	3526
April	1st to 10th	Night	1 3 1 4 3 4 3 3 6% 8% 64%	1900
	11th to 20th	Night	3 1 3 4 3 3 4 5% 6% 68%	1879
	21st to end	Night	2 4 2 3 2 2 2 2 4 6% 72%	1900
May	1st to 10th	Night	1 2 1 2 2 2 2 2 3 5% 77%	2964
	11th to 20th	Night	1 2 1 3 2 2 3 2 3 5% 76%	2780
	21st to end	Night	2 3 1 3 2 2 2 2 4 5% 74%	2762
June	1st to 10th	Night	3 3 1 3 2 2 3 4 6% 6% 68%	1520
	11th to 20th	Night	2 2 1 2 1 1 2 1 3 5% 82%	1520
	21st to end	Night	1 2 1 2 2 2 2 1 2 4 81%	1520
July	1st to 10th	Night	1 1 1 1 1 2 3 3 88%	2540
	11th to 20th	Night	4 5% 2 5% 3 3 4 3 4 4 65%	2540
	21st to end	Night	2 2 1 2 2 2 2 3 3 5% 76%	2849
August	1st to 10th	Night	2 2 1 2 2 2 2 2 4 5% 76%	3039
	11th to 20th	Night	2 1 1 1 1 1 2 2 3 85%	3126
	21st to end	Night	1 1 1 1 1 1 2 3 88%	3498
September	1st to 10th	Night	1 1 1 1 1 2 1 1 3 88%	1900
	11th to 20th	Night	2 2 1 2 1 2 2 2 4 4 78%	1967
	21st to end	Night	1 2 1 2 1 1 1 2 3 5% 81%	2090
October	1st to 10th	Night	3 3 1 3 2 1 1 2 2 5% 78%	3633
	11th to 20th	Night	1 1 1 2 1 1 1 2 4 4 82%	3777
	21st to end	Night	1 1 3 1 2 2 2 3 6% 78%	4232
November	1st to 10th	Night	2 1 2 2 2 2 3 4 7% 75%	2535
	11th to 20th	Night	1 1 1 2 2 3 3 2 5% 7% 75%	2476
	21st to end	Night	1 3 1 2 2 2 3 3 5% 9% 70%	2470
December	1st to 10th	Night	2 1 4 2 3 3 3 6% 8% 67%	2600
	11th to 20th	Night	3 2 4 4 3 4 5% 7% 11% 57%	3276
	21st to end	Night	1 7% 2 6% 4 4 4 5% 7% 12% 48%	4862

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	13% 12% 23% 29% 19% 4	2539
	11th to 20th	Day	18% 16% 18% 21% 20% 7%	2605
	21st to end	Day	23% 12% 18% 23% 19% 5%	3146
February	1st to 10th	Day	17% 8% 16% 24% 24% 12%	1799
	11th to 20th	Day	18% 8% 15% 28% 24% 8%	1860
	21st to end	Day	16% 10% 18% 29% 22% 6%	1570
March	1st to 10th	Day	21% 13% 20% 21% 16% 8%	3138
	11th to 20th	Day	13% 14% 19% 35% 14% 4	3356
	21st to end	Day	19% 13% 20% 29% 16% 3	4125
April	1st to 10th	Day	19% 11% 17% 27% 18% 8%	2280
	11th to 20th	Day	17% 9% 15% 29% 21% 8%	2252
	21st to end	Day	16% 9% 18% 30% 23% 5%	2280
May	1st to 10th	Day	11% 8% 10% 25% 34% 10%	4007
	11th to 20th	Day	13% 7% 10% 23% 35% 12%	4121
	21st to end	Day	17% 7% 10% 22% 37% 7%	4814
June	1st to 10th	Day	19% 8% 11% 21% 30% 11%	2660
	11th to 20th	Day	10% 4 7% 19% 35% 24%	2660
	21st to end	Day	13% 4 4 10% 32% 35%	2660
July	1st to 10th	Day	9% 3 3 6% 13% 67%	4351
	11th to 20th	Day	21% 7% 5% 9% 16% 43%	4345
	21st to end	Day	18% 6% 6% 11% 18% 42%	4552
August	1st to 10th	Day	18% 6% 5% 8% 23% 41%	3891
	11th to 20th	Day	9% 3 2 6% 17% 63%	3760
	21st to end	Day	9% 2 3 7% 30% 49%	4179
September	1st to 10th	Day	13% 3 4 9% 29% 41%	2280
	11th to 20th	Day	13% 4 5% 20% 29% 28%	2211
	21st to end	Day	11% 2 5% 18% 34% 29%	2090
October	1st to 10th	Day	13% 4 6% 12% 36% 30%	3344
	11th to 20th	Day	10% 2 4 13% 47% 24%	3161
	21st to end	Day	8% 4 6% 22% 43% 17%	3331
November	1st to 10th	Day	13% 6% 14% 24% 29% 13%	1764
	11th to 20th	Day	9% 8% 14% 27% 31% 12%	1710
	21st to end	Day	13% 6% 13% 28% 28% 12%	1710
December	1st to 10th	Day	13% 11% 17% 26% 23% 11%	1577
	11th to 20th	Day	23% 17% 16% 21% 15% 8%	1928
	21st to end	Day	22% 12% 19% 21% 21% 5%	2794
January	1st to 10th	Night	16% 10% 17% 32% 21% 4	4406
	11th to 20th	Night	17% 13% 22% 25% 17% 6%	4354
	21st to end	Night	22% 13% 18% 26% 17% 5%	4521
February	1st to 10th	Night	19% 9% 14% 25% 22% 11%	2379
	11th to 20th	Night	16% 6% 15% 28% 27% 8%	2219
	21st to end	Night	16% 9% 15% 30% 23% 7%	1884
March	1st to 10th	Night	19% 12% 19% 23% 19% 8%	3736
	11th to 20th	Night	14% 11% 19% 34% 17% 4	3620
	21st to end	Night	17% 11% 19% 33% 18% 2	3526
April	1st to 10th	Night	18% 10% 17% 31% 18% 7%	1900
	11th to 20th	Night	16% 8% 16% 28% 23% 9%	1879
	21st to end	Night	15% 6% 17% 35% 23% 4	1900
May	1st to 10th	Night	10% 5% 9% 33% 36% 7%	2964
	11th to 20th	Night	12% 5% 9% 27% 38% 9%	2781
	21st to end	Night	12% 6% 10% 30% 37% 4	2762
June	1st to 10th	Night	15% 7% 11% 27% 33% 8%	1520
	11th to 20th	Night	8% 4 7% 20% 38% 23%	1520
	21st to end	Night	10% 3 4 15% 34% 35%	1520
July	1st to 10th	Night	4 2 3 7% 16% 68%	2500
	11th to 20th	Night	19% 6% 5% 9% 20% 41%	2492
	21st to end	Night	11% 5% 4 15% 21% 44%	2760
August	1st to 10th	Night	11% 3 6% 12% 29% 40%	3030
	11th to 20th	Night	7% 3 3 9% 18% 61%	3156
	21st to end	Night	5% 2 3 12% 33% 47%	3498
September	1st to 10th	Night	5% 2 4 13% 37% 39%	1900
	11th to 20th	Night	9% 4 7% 18% 37% 25%	1967
	21st to end	Night	9% 2 6% 19% 38% 26%	2090
October	1st to 10th	Night	11% 3 5% 14% 42% 24%	3633
	11th to 20th	Night	7% 3 5% 15% 45% 25%	3777
	21st to end	Night	7% 5% 6% 20% 39% 23%	4232
November	1st to 10th	Night	10% 7% 13% 27% 30% 13%	2535
	11th to 20th	Night	10% 7% 14% 27% 31% 11%	2476
	21st to end	Night	13% 7% 16% 25% 29% 11%	2470
December	1st to 10th	Night	15% 10% 17% 24% 24% 10%	2600
	11th to 20th	Night	19% 15% 20% 22% 19% 5%	3276
	21st to end	Night	24% 15% 17% 18% 20% 6%	4862

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	4 19% 34% 27% 13% 3	180
	11th to 20th	Day	1 16% 29% 26% 20% 7%	219
	21st to end	Day	3 14% 23% 35% 20% 6%	407
February	1st to 10th	Day	5% 14% 30% 27% 17% 7%	412
	11th to 20th	Day	2 16% 29% 31% 18% 3	455
	21st to end	Day	4 16% 32% 30% 16% 2	382
March	1st to 10th	Day	3 17% 35% 31% 12% 3	460
	11th to 20th	Day	3 22% 28% 24% 17% 5%	460
	21st to end	Day	3 21% 36% 26% 12%	506
April	1st to 10th	Day	6% 19% 32% 23% 18% 2	460
	11th to 20th	Day	6% 19% 30% 27% 13% 4	452
	21st to end	Day	4 18% 28% 28% 16% 7%	460
May	1st to 10th	Day	7% 15% 34% 27% 12% 5%	463
	11th to 20th	Day	7% 19% 27% 24% 14% 9%	488
	21st to end	Day	8% 14% 23% 26% 20% 8%	529
June	1st to 10th	Day	6% 15% 26% 24% 21% 8%	490
	11th to 20th	Day	4 16% 29% 28% 16% 8%	490
	21st to end	Day	3 10% 27% 35% 18% 8%	490
July	1st to 10th	Day	2 6% 27% 35% 20% 10%	486
	11th to 20th	Day	4 4 22% 33% 27% 10%	484
	21st to end	Day	6% 5% 22% 34% 22% 12%	531
August	1st to 10th	Day	4 8% 25% 31% 22% 10%	487
	11th to 20th	Day	3 7% 27% 31% 23% 9%	477
	21st to end	Day	2 6% 26% 35% 22% 9%	539
September	1st to 10th	Day	3 7% 23% 34% 23% 8%	490
	11th to 20th	Day	5% 13% 28% 29% 22% 4	490
	21st to end	Day	3 9% 24% 35% 24% 5%	490
October	1st to 10th	Day	4 14% 26% 28% 21% 7%	490
	11th to 20th	Day	3 10% 26% 29% 24% 7%	490
	21st to end	Day	3 11% 27% 28% 23% 7%	471
November	1st to 10th	Day	4 9% 28% 28% 19% 12%	300
	11th to 20th	Day	3 11% 20% 28% 26% 11%	270
	21st to end	Day	1 10% 25% 30% 26% 9%	270
December	1st to 10th	Day	7% 8% 29% 29% 17% 11%	207
	11th to 20th	Day	2 13% 26% 30% 21% 8%	180
	21st to end	Day	4 18% 29% 27% 16% 6%	198
January	1st to 10th	Night	3 7% 34% 30% 18% 8%	760
	11th to 20th	Night	1 7% 30% 40% 15% 7%	760
	21st to end	Night	2 6% 32% 35% 19% 6%	836
February	1st to 10th	Night	2 7% 32% 35% 20% 5%	760
	11th to 20th	Night	1 9% 32% 33% 19% 6%	744
	21st to end	Night	1 10% 36% 35% 14% 4	628
March	1st to 10th	Night	3 9% 38% 33% 14% 4	760
	11th to 20th	Night	2 9% 33% 30% 18% 7%	760
	21st to end	Night	1 11% 37% 33% 15% 2	836
April	1st to 10th	Night	3 8% 33% 35% 18% 3	760
	11th to 20th	Night	2 10% 32% 34% 17% 5%	751
	21st to end	Night	3 8% 29% 36% 19% 6%	760
May	1st to 10th	Night	4 7% 30% 37% 19% 4	635
	11th to 20th	Night	4 5% 24% 39% 25% 3	534
	21st to end	Night	5% 5% 24% 32% 30% 4	411
June	1st to 10th	Night	3 3 21% 38% 33% 3	380
	11th to 20th	Night	2 2 25% 39% 28% 3	380
	21st to end	Night	1 1 19% 49% 27% 3	380
July	1st to 10th	Night	1 9% 52% 36% 3	370
	11th to 20th	Night	2 1 10% 45% 39% 2	368
	21st to end	Night	2 7% 46% 39% 6%	468
August	1st to 10th	Night	3 1 12% 41% 37% 6%	680
	11th to 20th	Night	3 1 14% 43% 35% 5%	752
	21st to end	Night	2 1 12% 44% 36% 5%	836
September	1st to 10th	Night	1 2 14% 40% 38% 6%	760
	11th to 20th	Night	3 3 19% 39% 31% 6%	760
	21st to end	Night	2 3 19% 37% 31% 8%	760
October	1st to 10th	Night	4 4 21% 38% 28% 6%	760
	11th to 20th	Night	2 6% 17% 40% 28% 7%	760
	21st to end	Night	2 4 22% 34% 26% 12%	836
November	1st to 10th	Night	1 5% 27% 34% 25% 8%	780
	11th to 20th	Night	2 6% 26% 39% 22% 6%	762
	21st to end	Night	3 6% 27% 33% 26% 5%	760
December	1st to 10th	Night	2 6% 33% 37% 16% 7%	760
	11th to 20th	Night	1 7% 35% 36% 17% 4	760
	21st to end	Night	1 11% 38% 33% 14% 3	836

Page generated at 2024-11-08 03:44:51. Version ac07

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