Dell City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dell City clear sky chart from 2005-11-06 to 2026-01-02.

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	3 2 1 3 3 3 3 3 5% 7% 67%	134745
	Night	3 3 1 3 3 3 3 3 5% 7% 65%	134016
Transparency	Day	16% 4 8% 18% 28% 27%	129841
	Night	17% 4 7% 16% 28% 27%	129924
Seeing	Day	4 6% 16% 31% 27% 14%	16111
	Night	4 4 21% 45% 24% 1	26401

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	4 4 1 4 3 3 3 3 4 6% 64%	4107
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 6% 78%	4100
	21st to end	Day	3 3 1 4 3 3 3 3 5% 7% 65%	4702
February	1st to 10th	Day	3 3 1 3 2 2 4 3 4 8% 68%	2000
	11th to 20th	Day	4 4 1 4 4 4 3 3 4 6% 64%	1949
	21st to end	Day	4 3 1 3 3 2 3 2 5% 6% 70%	1650
March	1st to 10th	Day	2 2 1 3 3 3 3 3 5% 7% 69%	4638
	11th to 20th	Day	5% 3 1 3 2 2 3 3 5% 6% 68%	5000
	21st to end	Day	2 4 1 4 3 3 3 3 4 6% 66%	5748
April	1st to 10th	Day	2 2 1 3 2 2 2 3 4 7% 71%	2400
	11th to 20th	Day	2 3 1 2 2 2 2 2 3 5% 77%	2371
	21st to end	Day	2 1 1 2 2 2 2 2 3 5% 79%	2400
May	1st to 10th	Day	1 1 1 1 1 2 2 2 3 4 81%	5440
	11th to 20th	Day	2 1 1 2 2 2 3 3 4 6% 75%	5405
	21st to end	Day	1 1 1 1 2 2 2 2 4 4 80%	6123
June	1st to 10th	Day	2 1 1 2 3 3 3 3 5% 7% 71%	2723
	11th to 20th	Day	1 1 1 2 2 3 2 3 5% 5% 75%	2800
	21st to end	Day	3 3 1 3 3 3 5% 5% 7% 9% 57%	2715
July	1st to 10th	Day	3 2 1 4 4 4 5% 5% 8% 9% 56%	5879
	11th to 20th	Day	1 2 1 2 3 4 4 4 8% 12% 60%	5880
	21st to end	Day	3 2 1 4 4 5% 5% 5% 9% 13% 48%	6106
August	1st to 10th	Day	1 1 1 2 3 3 4 4 7% 11% 65%	5348
	11th to 20th	Day	2 2 1 4 3 4 6% 5% 9% 12% 53%	5366
	21st to end	Day	2 2 1 4 3 3 4 4 7% 10% 59%	5984
September	1st to 10th	Day	7% 4 2 4 3 4 4 4 5% 8% 56%	2400
	11th to 20th	Day	6% 4 1 5% 3 3 4 4 6% 8% 55%	2365
	21st to end	Day	3 2 1 3 3 3 3 3 4 6% 69%	2200
October	1st to 10th	Day	2 1 2 2 1 2 2 3 5% 79%	3403
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	3250
	21st to end	Day	1 1 2 1 1 2 2 2 3 84%	3548
November	1st to 10th	Day	3 2 1 3 2 2 2 2 4 5% 73%	2059
	11th to 20th	Day	1 2 1 2 2 2 3 3 4 6% 72%	1910
	21st to end	Day	4 3 1 3 3 2 4 3 5% 6% 65%	1890
December	1st to 10th	Day	5% 5% 2 5% 4 3 4 3 5% 5% 61%	3030
	11th to 20th	Day	1 3 1 4 4 3 3 2 4 7% 67%	3464
	21st to end	Day	3 2 1 2 2 2 3 2 4 7% 72%	4392
January	1st to 10th	Night	5% 6% 1 4 3 2 2 3 5% 6% 64%	5880
	11th to 20th	Night	2 2 2 2 2 2 3 4 5% 76%	5880
	21st to end	Night	4 3 1 4 3 3 4 3 4 7% 63%	6272
February	1st to 10th	Night	3 3 1 3 2 2 3 3 5% 7% 68%	2400
	11th to 20th	Night	4 3 1 4 3 3 3 3 5% 6% 65%	2338
	21st to end	Night	4 3 1 3 3 3 2 2 5% 6% 68%	1980
March	1st to 10th	Night	3 3 1 2 2 2 3 2 4 6% 71%	5225
	11th to 20th	Night	6% 4 1 3 2 2 3 3 5% 7% 65%	5000
	21st to end	Night	3 3 1 3 2 2 3 3 5% 7% 68%	5214
April	1st to 10th	Night	3 2 1 3 2 2 3 3 5% 6% 69%	2000
	11th to 20th	Night	3 2 1 2 2 2 3 3 4 6% 72%	1977
	21st to end	Night	2 1 1 2 2 2 3 2 4 5% 77%	2000
May	1st to 10th	Night	3 2 1 2 2 2 2 2 3 4 78%	4540
	11th to 20th	Night	3 3 1 3 3 3 3 2 5% 8% 66%	4510
	21st to end	Night	1 1 1 2 2 2 2 2 4 5% 79%	4751
June	1st to 10th	Night	2 2 1 3 3 4 4 4 7% 10% 60%	1670
	11th to 20th	Night	2 2 1 2 3 3 3 3 6% 6% 70%	1600
	21st to end	Night	2 3 1 5% 5% 4 6% 4 8% 8% 53%	1674
July	1st to 10th	Night	3 3 2 6% 4 5% 5% 4 8% 12% 49%	4100
	11th to 20th	Night	1 2 1 3 3 4 5% 5% 8% 13% 56%	4100
	21st to end	Night	3 3 2 6% 5% 6% 7% 6% 9% 12% 41%	4750
August	1st to 10th	Night	2 1 1 3 3 4 5% 4 8% 11% 59%	4464
	11th to 20th	Night	2 4 2 6% 5% 5% 6% 5% 8% 13% 45%	4483
	21st to end	Night	2 3 1 4 4 5% 6% 5% 9% 12% 48%	4993
September	1st to 10th	Night	5% 4 2 5% 3 4 6% 5% 7% 8% 53%	2000
	11th to 20th	Night	5% 4 2 6% 4 4 4 3 7% 9% 52%	2034
	21st to end	Night	4 3 2 4 3 3 3 4 6% 7% 61%	2200
October	1st to 10th	Night	2 2 1 2 2 2 2 2 3 4 77%	3778
	11th to 20th	Night	5% 3 1 4 3 2 2 2 3 5% 69%	3898
	21st to end	Night	2 1 2 1 2 2 2 3 4 81%	4252
November	1st to 10th	Night	4 2 1 3 2 1 2 2 3 5% 75%	2460
	11th to 20th	Night	2 1 1 3 2 2 3 2 4 6% 73%	2685
	21st to end	Night	5% 3 1 3 3 3 3 2 5% 5% 67%	2730
December	1st to 10th	Night	6% 3 1 4 2 3 3 4 5% 6% 64%	4380
	11th to 20th	Night	2 2 1 3 3 2 3 2 4 7% 70%	4946
	21st to end	Night	2 2 1 2 2 2 3 2 3 5% 75%	6852

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	21% 3 4 13% 36% 23%	4108
	11th to 20th	Day	10% 2 3 19% 46% 20%	4100
	21st to end	Day	18% 5% 6% 21% 27% 23%	4702
February	1st to 10th	Day	16% 4 7% 16% 27% 30%	2000
	11th to 20th	Day	21% 4 7% 17% 26% 24%	1959
	21st to end	Day	17% 3 3 12% 29% 37%	1650
March	1st to 10th	Day	15% 3 5% 8% 27% 43%	4638
	11th to 20th	Day	17% 4 4 15% 29% 32%	5000
	21st to end	Day	18% 4 5% 11% 25% 38%	5748
April	1st to 10th	Day	14% 3 5% 12% 30% 36%	2400
	11th to 20th	Day	12% 3 4 12% 25% 44%	2374
	21st to end	Day	10% 3 4 12% 28% 44%	2400
May	1st to 10th	Day	8% 3 4 15% 25% 46%	5440
	11th to 20th	Day	10% 4 4 12% 24% 46%	5408
	21st to end	Day	8% 2 6% 14% 15% 55%	6124
June	1st to 10th	Day	12% 4 8% 20% 27% 29%	2723
	11th to 20th	Day	10% 3 5% 13% 25% 44%	2800
	21st to end	Day	20% 7% 11% 19% 21% 23%	2715
July	1st to 10th	Day	23% 6% 13% 25% 23% 10%	5816
	11th to 20th	Day	16% 4 16% 33% 24% 7%	5811
	21st to end	Day	24% 6% 19% 28% 19% 3	5931
August	1st to 10th	Day	15% 7% 10% 32% 30% 6%	3892
	11th to 20th	Day	19% 6% 13% 22% 30% 11%	3882
	21st to end	Day	23% 6% 14% 31% 21% 5%	4311
September	1st to 10th	Day	27% 5% 12% 18% 22% 16%	2400
	11th to 20th	Day	26% 6% 10% 19% 26% 14%	2365
	21st to end	Day	16% 4 8% 19% 33% 19%	2200
October	1st to 10th	Day	10% 3 6% 10% 26% 45%	3403
	11th to 20th	Day	13% 3 7% 17% 27% 34%	3250
	21st to end	Day	8% 2 3 15% 37% 35%	3548
November	1st to 10th	Day	14% 3 5% 19% 30% 29%	2059
	11th to 20th	Day	13% 3 8% 20% 31% 25%	1910
	21st to end	Day	19% 3 8% 19% 32% 19%	1890
December	1st to 10th	Day	25% 3 7% 20% 30% 15%	3030
	11th to 20th	Day	19% 3 6% 17% 39% 17%	3462
	21st to end	Day	13% 3 5% 18% 41% 19%	4392
January	1st to 10th	Night	21% 3 4 14% 40% 18%	5880
	11th to 20th	Night	11% 3 4 19% 41% 22%	5880
	21st to end	Night	20% 4 5% 20% 31% 19%	6272
February	1st to 10th	Night	15% 3 7% 16% 26% 34%	2400
	11th to 20th	Night	19% 4 7% 14% 28% 28%	2338
	21st to end	Night	17% 3 6% 10% 25% 39%	1980
March	1st to 10th	Night	14% 3 3 8% 28% 44%	5225
	11th to 20th	Night	18% 5% 5% 11% 26% 34%	5000
	21st to end	Night	15% 4 5% 13% 26% 38%	5214
April	1st to 10th	Night	16% 3 4 10% 31% 36%	2000
	11th to 20th	Night	13% 4 6% 12% 23% 42%	1977
	21st to end	Night	10% 3 5% 12% 26% 43%	2000
May	1st to 10th	Night	12% 2 4 17% 15% 50%	4537
	11th to 20th	Night	16% 4 5% 12% 22% 41%	4511
	21st to end	Night	9% 3 7% 10% 13% 58%	4752
June	1st to 10th	Night	19% 5% 9% 18% 21% 28%	1670
	11th to 20th	Night	13% 4 8% 12% 20% 43%	1600
	21st to end	Night	25% 7% 13% 17% 18% 20%	1674
July	1st to 10th	Night	27% 6% 16% 27% 18% 6%	4055
	11th to 20th	Night	18% 5% 18% 27% 24% 8%	4046
	21st to end	Night	32% 5% 16% 26% 18% 3	4613
August	1st to 10th	Night	20% 7% 10% 24% 29% 10%	3244
	11th to 20th	Night	21% 6% 11% 21% 31% 10%	3243
	21st to end	Night	26% 7% 16% 23% 21% 6%	3597
September	1st to 10th	Night	26% 10% 11% 18% 18% 18%	2000
	11th to 20th	Night	27% 7% 12% 19% 18% 17%	2034
	21st to end	Night	21% 5% 9% 16% 29% 20%	2200
October	1st to 10th	Night	13% 3 5% 9% 24% 46%	3778
	11th to 20th	Night	20% 2 6% 12% 21% 39%	3898
	21st to end	Night	10% 1 3 13% 33% 40%	4252
November	1st to 10th	Night	14% 2 5% 15% 32% 32%	2460
	11th to 20th	Night	14% 3 5% 17% 33% 27%	2685
	21st to end	Night	19% 4 5% 17% 32% 23%	2730
December	1st to 10th	Night	20% 3 6% 24% 31% 15%	4380
	11th to 20th	Night	15% 3 4 14% 39% 25%	4947
	21st to end	Night	12% 2 4 18% 41% 22%	6852

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	9% 7% 22% 41% 20% 1	303
	11th to 20th	Day	5% 6% 22% 42% 23% 2	300
	21st to end	Day	4 8% 21% 43% 20% 4	330
February	1st to 10th	Day	7% 5% 21% 38% 23% 5%	300
	11th to 20th	Day	8% 10% 27% 37% 19% 1	300
	21st to end	Day	9% 11% 26% 40% 11% 3	249
March	1st to 10th	Day	7% 14% 25% 41% 12% 1	360
	11th to 20th	Day	8% 17% 26% 30% 14% 4	500
	21st to end	Day	6% 19% 31% 29% 13% 2	550
April	1st to 10th	Day	6% 13% 31% 32% 16% 3	500
	11th to 20th	Day	5% 18% 31% 33% 10% 3	492
	21st to end	Day	3 15% 35% 28% 17% 2	500
May	1st to 10th	Day	2 11% 35% 32% 17% 3	503
	11th to 20th	Day	2 10% 26% 36% 20% 7%	528
	21st to end	Day	1 6% 25% 41% 23% 4	648
June	1st to 10th	Day	2 3 12% 40% 35% 9%	730
	11th to 20th	Day	1 1 13% 38% 36% 10%	730
	21st to end	Day	4 1 9% 31% 38% 18%	645
July	1st to 10th	Day	3 6% 22% 34% 35%	526
	11th to 20th	Day	3 1 3 18% 34% 40%	524
	21st to end	Day	2 1 3 20% 36% 38%	575
August	1st to 10th	Day	2 1 2 14% 39% 43%	527
	11th to 20th	Day	3 3 4 20% 37% 32%	517
	21st to end	Day	4 1 5% 20% 35% 35%	583
September	1st to 10th	Day	7% 2 5% 25% 37% 25%	530
	11th to 20th	Day	4 1 6% 25% 42% 22%	495
	21st to end	Day	5% 1 5% 24% 37% 29%	330
October	1st to 10th	Day	6% 3 7% 29% 35% 21%	330
	11th to 20th	Day	5% 4 12% 27% 38% 14%	330
	21st to end	Day	3 7% 15% 29% 28% 18%	363
November	1st to 10th	Day	5% 8% 14% 33% 30% 12%	330
	11th to 20th	Day	2 8% 10% 32% 36% 11%	330
	21st to end	Day	7% 9% 18% 38% 22% 5%	330
December	1st to 10th	Day	8% 5% 13% 37% 33% 4	330
	11th to 20th	Day	4 7% 14% 43% 24% 7%	330
	21st to end	Day	8% 8% 19% 40% 19% 7%	363
January	1st to 10th	Night	7% 4 24% 49% 15% 1	804
	11th to 20th	Night	6% 4 27% 48% 14% 2	800
	21st to end	Night	6% 7% 26% 47% 13% 1	880
February	1st to 10th	Night	4 5% 27% 48% 16%	800
	11th to 20th	Night	5% 6% 34% 45% 9% 1	784
	21st to end	Night	5% 7% 41% 42% 5%	660
March	1st to 10th	Night	7% 8% 34% 43% 8%	800
	11th to 20th	Night	8% 9% 28% 44% 12% 1	800
	21st to end	Night	3 6% 40% 43% 8%	760
April	1st to 10th	Night	5% 7% 37% 43% 8%	600
	11th to 20th	Night	4 8% 40% 41% 7%	593
	21st to end	Night	2 8% 36% 45% 9%	600
May	1st to 10th	Night	4 5% 37% 48% 7%	600
	11th to 20th	Night	3 6% 25% 52% 14%	591
	21st to end	Night	2 2 26% 56% 14%	650
June	1st to 10th	Night	3 3 15% 58% 23%	600
	11th to 20th	Night	2 1 14% 60% 24%	600
	21st to end	Night	3 1 9% 50% 35% 2	600
July	1st to 10th	Night	2 1 4 40% 50% 3	585
	11th to 20th	Night	2 1 3 35% 56% 3	582
	21st to end	Night	2 1 2 31% 58% 6%	657
August	1st to 10th	Night	4 1 3 21% 66% 6%	597
	11th to 20th	Night	3 2 3 26% 60% 7%	594
	21st to end	Night	4 2 3 29% 58% 5%	660
September	1st to 10th	Night	7% 2 4 38% 47% 4	600
	11th to 20th	Night	6% 2 5% 44% 43% 2	600
	21st to end	Night	6% 1 9% 47% 36% 2	600
October	1st to 10th	Night	4 2 12% 51% 30% 1	710
	11th to 20th	Night	7% 2 16% 48% 27% 1	800
	21st to end	Night	4 4 15% 46% 28% 4	880
November	1st to 10th	Night	5% 2 17% 47% 28% 2	820
	11th to 20th	Night	3 3 19% 49% 24% 1	1005
	21st to end	Night	6% 4 26% 42% 20% 2	1050
December	1st to 10th	Night	7% 4 22% 50% 17%	1050
	11th to 20th	Night	5% 5% 24% 51% 15% 1	1050
	21st to end	Night	5% 6% 24% 51% 14%	1039

Page generated at 2025-12-30 00:14:09. Version ac07

Copyright © 2025 Attilla Danko.