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 2024-11-12.

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%	104430
	Night	3 3 1 3 3 3 3 3 5% 7% 65%	103424
Transparency	Day	16% 4 8% 18% 27% 26%	104200
	Night	18% 5% 8% 16% 27% 26%	103243
Seeing	Day	4 7% 17% 31% 27% 14%	14639
	Night	5% 4 21% 45% 24% 2	24844

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	3 3 1 3 3 3 3 3 4 6% 67%	2858
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 77%	2860
	21st to end	Day	5% 4 2 5% 4 3 4 3 6% 8% 57%	3273
February	1st to 10th	Day	3 3 1 3 2 2 4 3 4 8% 67%	1900
	11th to 20th	Day	4 4 1 4 4 4 3 3 4 6% 64%	1849
	21st to end	Day	4 3 1 3 3 2 3 2 5% 6% 69%	1570
March	1st to 10th	Day	3 2 1 4 3 3 4 3 5% 7% 64%	3226
	11th to 20th	Day	6% 3 2 4 3 3 3 3 5% 6% 63%	3490
	21st to end	Day	2 3 1 4 3 4 3 4 5% 6% 64%	4009
April	1st to 10th	Day	2 2 1 3 2 2 2 3 5% 7% 71%	2280
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 76%	2251
	21st to end	Day	2 1 1 2 2 2 2 2 3 5% 79%	2280
May	1st to 10th	Day	2 1 1 1 1 2 2 2 3 4 83%	3800
	11th to 20th	Day	2 1 1 2 2 2 3 3 4 6% 74%	3765
	21st to end	Day	1 1 1 2 2 2 2 2 3 4 81%	4264
June	1st to 10th	Day	2 1 1 2 3 3 3 3 5% 7% 70%	2587
	11th to 20th	Day	1 1 1 2 2 3 2 3 5% 5% 74%	2660
	21st to end	Day	3 2 1 3 3 3 5% 6% 7% 9% 60%	2580
July	1st to 10th	Day	2 2 1 4 4 4 5% 5% 8% 9% 56%	4110
	11th to 20th	Day	2 2 1 3 3 4 4 4 7% 11% 58%	4110
	21st to end	Day	5% 3 2 4 4 5% 5% 5% 8% 12% 48%	4250
August	1st to 10th	Day	2 2 1 2 3 3 4 4 8% 11% 60%	3784
	11th to 20th	Day	2 2 1 3 3 3 5% 4 7% 9% 61%	3726
	21st to end	Day	3 2 1 5% 4 4 5% 4 8% 11% 53%	4180
September	1st to 10th	Day	7% 3 2 4 3 4 4 4 6% 8% 56%	2280
	11th to 20th	Day	6% 4 1 5% 3 3 4 4 6% 8% 56%	2247
	21st to end	Day	4 2 1 3 3 2 3 3 4 6% 70%	2090
October	1st to 10th	Day	2 1 2 2 1 1 2 3 5% 79%	3299
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	3150
	21st to end	Day	1 1 2 1 1 2 2 2 3 84%	3438
November	1st to 10th	Day	3 3 1 3 3 2 2 2 4 6% 72%	1959
	11th to 20th	Day	1 2 1 2 2 2 3 3 5% 6% 72%	1738
	21st to end	Day	5% 3 1 3 3 3 4 4 5% 6% 64%	1710
December	1st to 10th	Day	5% 4 1 3 3 3 4 3 6% 7% 61%	1710
	11th to 20th	Day	2 4 2 5% 5% 3 4 3 5% 9% 58%	2157
	21st to end	Day	4 3 1 3 3 2 3 3 5% 8% 65%	2990
January	1st to 10th	Night	3 5% 1 3 3 2 3 3 4 6% 67%	4097
	11th to 20th	Night	3 3 1 2 2 2 2 3 4 5% 74%	4110
	21st to end	Night	6% 5% 1 5% 4 4 5% 3 5% 8% 55%	4390
February	1st to 10th	Night	3 4 1 3 2 2 3 3 5% 7% 67%	2280
	11th to 20th	Night	4 3 1 4 3 3 4 3 5% 6% 64%	2218
	21st to end	Night	4 3 1 3 3 3 2 2 5% 7% 67%	1884
March	1st to 10th	Night	5% 4 1 3 2 2 3 3 4 6% 67%	3624
	11th to 20th	Night	9% 5% 2 4 3 2 3 3 5% 7% 56%	3490
	21st to end	Night	3 4 1 4 2 3 4 3 5% 8% 64%	3637
April	1st to 10th	Night	3 2 1 3 2 2 3 3 5% 6% 69%	1900
	11th to 20th	Night	4 2 1 2 2 2 3 3 4 6% 71%	1877
	21st to end	Night	2 1 1 2 2 2 3 2 4 5% 76%	1900
May	1st to 10th	Night	2 2 1 2 2 2 2 2 3 4 81%	3170
	11th to 20th	Night	3 2 1 3 2 3 3 3 5% 6% 69%	3140
	21st to end	Night	1 1 1 2 2 2 2 2 4 4 79%	3300
June	1st to 10th	Night	2 2 1 3 3 4 4 4 7% 10% 59%	1587
	11th to 20th	Night	2 2 1 2 3 3 3 3 6% 6% 69%	1520
	21st to end	Night	2 3 1 5% 5% 4 6% 4 8% 8% 55%	1590
July	1st to 10th	Night	1 2 2 6% 5% 6% 6% 5% 8% 11% 46%	2860
	11th to 20th	Night	1 2 1 3 3 3 4 4 7% 11% 61%	2860
	21st to end	Night	4 3 2 6% 5% 5% 7% 6% 8% 10% 44%	3309
August	1st to 10th	Night	2 2 1 3 3 4 6% 5% 8% 11% 54%	3155
	11th to 20th	Night	1 2 1 4 4 4 4 4 7% 11% 58%	3113
	21st to end	Night	2 3 2 4 5% 5% 7% 6% 10% 13% 44%	3487
September	1st to 10th	Night	5% 3 2 4 3 4 6% 4 7% 8% 53%	1900
	11th to 20th	Night	5% 4 2 6% 3 4 4 3 7% 9% 53%	1932
	21st to end	Night	4 2 2 4 3 3 3 4 6% 7% 62%	2090
October	1st to 10th	Night	2 2 1 2 2 2 2 2 3 4 78%	3662
	11th to 20th	Night	5% 3 1 4 3 2 2 2 3 5% 70%	3778
	21st to end	Night	2 1 2 1 2 2 2 3 4 81%	4120
November	1st to 10th	Night	4 2 1 3 2 1 2 2 3 6% 74%	2340
	11th to 20th	Night	2 1 1 3 3 2 3 2 5% 6% 72%	2441
	21st to end	Night	6% 3 1 3 3 3 3 2 5% 5% 67%	2470
December	1st to 10th	Night	6% 3 1 3 3 3 3 3 5% 6% 64%	2470
	11th to 20th	Night	3 3 1 5% 4 3 4 3 4 8% 62%	3036
	21st to end	Night	3 3 1 3 2 3 3 3 4 5% 69%	4687

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	16% 3 6% 16% 37% 22%	2859
	11th to 20th	Day	11% 2 5% 19% 45% 17%	2860
	21st to end	Day	23% 6% 7% 24% 27% 14%	3273
February	1st to 10th	Day	16% 4 7% 17% 28% 28%	1900
	11th to 20th	Day	21% 4 7% 16% 27% 25%	1859
	21st to end	Day	16% 3 3 12% 29% 36%	1570
March	1st to 10th	Day	17% 3 7% 11% 32% 30%	3226
	11th to 20th	Day	21% 5% 6% 19% 28% 21%	3490
	21st to end	Day	17% 5% 6% 13% 29% 30%	4009
April	1st to 10th	Day	13% 3 5% 12% 31% 36%	2280
	11th to 20th	Day	12% 3 4 12% 26% 44%	2254
	21st to end	Day	10% 3 4 13% 28% 42%	2280
May	1st to 10th	Day	8% 3 3 8% 18% 60%	3800
	11th to 20th	Day	10% 5% 6% 14% 25% 41%	3768
	21st to end	Day	8% 2 5% 11% 15% 58%	4264
June	1st to 10th	Day	12% 4 8% 19% 27% 29%	2587
	11th to 20th	Day	11% 3 5% 13% 24% 44%	2660
	21st to end	Day	17% 7% 11% 20% 21% 24%	2580
July	1st to 10th	Day	22% 7% 14% 24% 22% 11%	4046
	11th to 20th	Day	18% 6% 14% 24% 29% 9%	4041
	21st to end	Day	26% 7% 14% 29% 21% 3	4115
August	1st to 10th	Day	16% 7% 10% 32% 30% 5%	3772
	11th to 20th	Day	18% 6% 12% 22% 31% 11%	3762
	21st to end	Day	23% 6% 15% 31% 20% 5%	4179
September	1st to 10th	Day	26% 6% 13% 18% 22% 16%	2280
	11th to 20th	Day	25% 6% 10% 18% 26% 14%	2247
	21st to end	Day	16% 5% 8% 18% 34% 20%	2090
October	1st to 10th	Day	10% 3 6% 10% 26% 46%	3299
	11th to 20th	Day	13% 3 6% 17% 27% 34%	3150
	21st to end	Day	8% 2 3 15% 37% 35%	3438
November	1st to 10th	Day	15% 3 6% 19% 30% 27%	1959
	11th to 20th	Day	13% 3 8% 21% 31% 24%	1738
	21st to end	Day	20% 3 7% 19% 31% 19%	1710
December	1st to 10th	Day	21% 4 9% 25% 29% 12%	1710
	11th to 20th	Day	23% 4 9% 22% 29% 13%	2155
	21st to end	Day	16% 4 7% 19% 34% 20%	2990
January	1st to 10th	Night	18% 4 5% 15% 41% 18%	4097
	11th to 20th	Night	12% 4 6% 19% 42% 18%	4110
	21st to end	Night	25% 5% 7% 22% 26% 13%	4390
February	1st to 10th	Night	16% 3 7% 16% 26% 31%	2280
	11th to 20th	Night	20% 4 7% 13% 27% 29%	2218
	21st to end	Night	18% 3 6% 10% 25% 39%	1884
March	1st to 10th	Night	18% 3 5% 11% 28% 35%	3624
	11th to 20th	Night	25% 7% 8% 15% 24% 21%	3490
	21st to end	Night	16% 5% 6% 14% 32% 27%	3637
April	1st to 10th	Night	16% 3 4 10% 30% 36%	1900
	11th to 20th	Night	14% 4 7% 12% 23% 41%	1877
	21st to end	Night	11% 3 5% 12% 27% 42%	1900
May	1st to 10th	Night	9% 2 4 7% 15% 63%	3170
	11th to 20th	Night	14% 5% 8% 14% 20% 40%	3141
	21st to end	Night	9% 4 5% 8% 15% 59%	3301
June	1st to 10th	Night	19% 6% 9% 17% 21% 28%	1587
	11th to 20th	Night	14% 4 8% 12% 19% 43%	1520
	21st to end	Night	23% 7% 13% 17% 18% 21%	1590
July	1st to 10th	Night	28% 6% 18% 26% 15% 8%	2815
	11th to 20th	Night	15% 7% 14% 22% 31% 12%	2806
	21st to end	Night	31% 6% 14% 25% 20% 3	3205
August	1st to 10th	Night	20% 8% 10% 24% 29% 9%	3144
	11th to 20th	Night	20% 6% 11% 21% 32% 11%	3143
	21st to end	Night	26% 7% 16% 23% 21% 6%	3487
September	1st to 10th	Night	25% 10% 11% 18% 18% 18%	1900
	11th to 20th	Night	26% 7% 12% 19% 18% 18%	1932
	21st to end	Night	20% 5% 9% 16% 29% 21%	2090
October	1st to 10th	Night	12% 3 5% 9% 23% 47%	3662
	11th to 20th	Night	19% 2 6% 12% 21% 39%	3778
	21st to end	Night	10% 1 3 13% 33% 40%	4120
November	1st to 10th	Night	15% 2 5% 16% 32% 30%	2340
	11th to 20th	Night	14% 3 6% 18% 33% 26%	2441
	21st to end	Night	20% 4 5% 17% 30% 23%	2470
December	1st to 10th	Night	20% 4 7% 23% 28% 17%	2470
	11th to 20th	Night	21% 4 6% 21% 31% 15%	3037
	21st to end	Night	16% 3 5% 17% 39% 19%	4687

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% 8% 21% 42% 19%	270
	11th to 20th	Day	5% 7% 23% 42% 21% 2	270
	21st to end	Day	4 8% 22% 41% 20% 4	297
February	1st to 10th	Day	7% 6% 21% 40% 21% 4	270
	11th to 20th	Day	9% 9% 27% 37% 18% 1	270
	21st to end	Day	9% 12% 28% 38% 9% 3	225
March	1st to 10th	Day	7% 13% 26% 42% 11% 1	327
	11th to 20th	Day	8% 15% 27% 31% 14% 4	460
	21st to end	Day	7% 20% 32% 29% 11% 2	506
April	1st to 10th	Day	4 14% 32% 32% 16% 2	460
	11th to 20th	Day	5% 19% 32% 33% 9% 2	452
	21st to end	Day	3 15% 37% 27% 16% 2	460
May	1st to 10th	Day	2 11% 36% 32% 17% 3	463
	11th to 20th	Day	2 8% 26% 37% 20% 7%	488
	21st to end	Day	2 6% 26% 41% 22% 3	600
June	1st to 10th	Day	2 3 12% 39% 35% 9%	680
	11th to 20th	Day	1 1 14% 38% 36% 9%	680
	21st to end	Day	3 1 9% 32% 38% 19%	600
July	1st to 10th	Day	2 6% 23% 34% 34%	486
	11th to 20th	Day	4 1 3 19% 34% 39%	484
	21st to end	Day	2 1 3 21% 36% 37%	531
August	1st to 10th	Day	2 1 2 14% 41% 40%	487
	11th to 20th	Day	4 3 5% 21% 37% 31%	477
	21st to end	Day	5% 1 5% 21% 36% 32%	539
September	1st to 10th	Day	7% 1 5% 26% 37% 24%	490
	11th to 20th	Day	5% 1 6% 25% 42% 22%	457
	21st to end	Day	5% 1 5% 24% 36% 28%	300
October	1st to 10th	Day	6% 3 7% 29% 36% 19%	300
	11th to 20th	Day	6% 4 11% 27% 37% 14%	300
	21st to end	Day	4 7% 15% 30% 26% 18%	330
November	1st to 10th	Day	5% 9% 14% 35% 28% 9%	300
	11th to 20th	Day	2 7% 11% 34% 37% 8%	273
	21st to end	Day	9% 11% 20% 34% 20% 6%	270
December	1st to 10th	Day	9% 6% 14% 36% 31% 4	270
	11th to 20th	Day	4 9% 17% 49% 21% 1	270
	21st to end	Day	8% 9% 20% 43% 17% 2	297
January	1st to 10th	Night	7% 4 24% 49% 15% 1	760
	11th to 20th	Night	6% 4 26% 47% 15% 2	760
	21st to end	Night	6% 7% 26% 46% 14% 1	836
February	1st to 10th	Night	4 6% 27% 47% 16%	760
	11th to 20th	Night	5% 6% 35% 45% 8% 1	744
	21st to end	Night	6% 8% 41% 41% 4	628
March	1st to 10th	Night	7% 8% 33% 44% 8%	760
	11th to 20th	Night	8% 8% 27% 45% 12% 1	760
	21st to end	Night	3 6% 40% 42% 8%	722
April	1st to 10th	Night	4 7% 38% 43% 8%	570
	11th to 20th	Night	4 8% 39% 42% 7%	563
	21st to end	Night	2 8% 36% 44% 9%	570
May	1st to 10th	Night	3 5% 37% 48% 7%	570
	11th to 20th	Night	2 6% 24% 53% 15%	561
	21st to end	Night	2 2 26% 55% 14%	617
June	1st to 10th	Night	3 3 14% 57% 24%	570
	11th to 20th	Night	2 1 14% 59% 24%	570
	21st to end	Night	3 1 9% 50% 35% 2	570
July	1st to 10th	Night	1 1 4 40% 50% 4	555
	11th to 20th	Night	2 1 3 35% 56% 3	552
	21st to end	Night	2 1 2 32% 57% 6%	624
August	1st to 10th	Night	4 1 3 21% 65% 6%	567
	11th to 20th	Night	2 1 3 26% 61% 7%	564
	21st to end	Night	4 1 3 30% 58% 5%	627
September	1st to 10th	Night	6% 1 4 37% 47% 4	570
	11th to 20th	Night	6% 1 4 44% 43% 2	570
	21st to end	Night	6% 1 9% 46% 36% 2	570
October	1st to 10th	Night	4 2 12% 51% 30% 1	674
	11th to 20th	Night	6% 2 16% 48% 26% 1	760
	21st to end	Night	4 4 15% 45% 27% 4	836
November	1st to 10th	Night	5% 2 17% 47% 27% 2	780
	11th to 20th	Night	2 4 18% 50% 25% 2	913
	21st to end	Night	6% 5% 25% 41% 21% 2	950
December	1st to 10th	Night	7% 4 21% 49% 18%	950
	11th to 20th	Night	5% 5% 26% 50% 13%	950
	21st to end	Night	6% 6% 25% 50% 13%	941

Page generated at 2024-11-08 21:45:39. Version ac07

Copyright © 2024 Attilla Danko.