Dirt Hills and Cactus Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dirt Hills and Cactus Hills clear sky chart from 2005-11-06 to 2024-11-04.

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	8% 8% 3 8% 5% 5% 5% 4 6% 8% 40%	105395
	Night	7% 8% 3 8% 5% 5% 5% 4 6% 8% 40%	102237
Transparency	Day	41% 7% 15% 26% 10% 1	105128
	Night	41% 6% 15% 25% 11% 2	102093
Seeing	Day	13% 10% 31% 29% 14% 4	15964
	Night	12% 8% 34% 33% 11% 1	25398

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	6% 10% 5% 11% 8% 8% 8% 6% 5% 6% 26%	2219
	11th to 20th	Day	4 8% 3 9% 9% 8% 12% 10% 8% 7% 21%	2454
	21st to end	Day	4 11% 5% 11% 6% 5% 4 5% 6% 7% 36%	2794
February	1st to 10th	Day	7% 13% 6% 14% 9% 6% 7% 5% 6% 5% 24%	1619
	11th to 20th	Day	7% 11% 5% 11% 9% 7% 8% 6% 5% 5% 26%	1665
	21st to end	Day	4 11% 6% 11% 10% 7% 6% 5% 8% 8% 25%	1513
March	1st to 10th	Day	6% 13% 6% 13% 8% 6% 4 4 5% 6% 27%	3130
	11th to 20th	Day	5% 13% 5% 10% 5% 4 5% 4 6% 8% 35%	3389
	21st to end	Day	7% 15% 6% 12% 7% 6% 5% 4 7% 7% 24%	4067
April	1st to 10th	Day	6% 11% 4 8% 6% 6% 6% 4 6% 7% 36%	2280
	11th to 20th	Day	13% 14% 5% 9% 6% 5% 5% 5% 6% 7% 26%	2251
	21st to end	Day	15% 9% 3 7% 5% 4 4 4 6% 7% 35%	2629
May	1st to 10th	Day	16% 11% 4 8% 5% 4 3 4 6% 7% 31%	4430
	11th to 20th	Day	8% 8% 3 8% 5% 6% 6% 5% 7% 10% 34%	4388
	21st to end	Day	14% 8% 3 7% 6% 5% 5% 5% 6% 8% 33%	4825
June	1st to 10th	Day	16% 7% 2 6% 4 4 5% 5% 7% 8% 37%	2854
	11th to 20th	Day	17% 7% 3 7% 6% 4 5% 4 6% 8% 32%	3040
	21st to end	Day	9% 5% 2 5% 4 5% 5% 5% 6% 9% 44%	2962
July	1st to 10th	Day	5% 4 2 6% 5% 6% 6% 5% 8% 9% 46%	4740
	11th to 20th	Day	5% 3 1 4 3 3 5% 4 7% 11% 54%	4618
	21st to end	Day	4 3 1 3 3 3 3 3 6% 7% 63%	4802
August	1st to 10th	Day	8% 4 2 6% 4 4 4 4 5% 7% 51%	4411
	11th to 20th	Day	6% 4 2 5% 3 4 4 5% 6% 9% 53%	4247
	21st to end	Day	9% 4 2 5% 3 3 3 3 5% 7% 56%	4284
September	1st to 10th	Day	12% 4 2 5% 4 4 4 3 5% 8% 49%	2280
	11th to 20th	Day	12% 8% 2 6% 4 4 4 3 5% 7% 45%	2280
	21st to end	Day	13% 7% 1 6% 4 3 3 3 6% 8% 46%	2039
October	1st to 10th	Day	8% 7% 2 5% 4 3 4 3 5% 7% 51%	3170
	11th to 20th	Day	7% 6% 3 6% 3 2 3 3 7% 12% 48%	3088
	21st to end	Day	6% 10% 3 8% 4 5% 5% 4 7% 8% 40%	3091
November	1st to 10th	Day	12% 12% 6% 10% 5% 4 5% 3 5% 6% 32%	1569
	11th to 20th	Day	5% 11% 5% 12% 8% 6% 6% 4 5% 6% 32%	1520
	21st to end	Day	9% 11% 4 9% 7% 7% 5% 3 5% 8% 31%	1501
December	1st to 10th	Day	7% 12% 5% 13% 9% 8% 6% 4 6% 5% 24%	1330
	11th to 20th	Day	5% 13% 5% 13% 7% 6% 6% 4 6% 8% 25%	1588
	21st to end	Day	6% 7% 3 8% 7% 5% 4 3 5% 5% 48%	2328
January	1st to 10th	Night	3 10% 5% 13% 7% 6% 7% 5% 8% 7% 29%	4726
	11th to 20th	Night	3 7% 4 12% 9% 9% 11% 6% 8% 7% 24%	4509
	21st to end	Night	5% 12% 4 10% 5% 4 5% 5% 6% 7% 36%	4873
February	1st to 10th	Night	6% 13% 4 12% 8% 6% 6% 5% 8% 8% 23%	2580
	11th to 20th	Night	6% 12% 4 11% 7% 6% 5% 5% 7% 8% 28%	2402
	21st to end	Night	3 10% 4 11% 7% 7% 7% 4 6% 8% 32%	1941
March	1st to 10th	Night	5% 9% 5% 13% 9% 6% 6% 5% 7% 8% 28%	3734
	11th to 20th	Night	5% 9% 4 9% 5% 6% 5% 4 6% 9% 39%	3584
	21st to end	Night	7% 11% 6% 15% 7% 5% 5% 4 6% 8% 26%	3578
April	1st to 10th	Night	7% 9% 3 7% 5% 4 5% 5% 7% 8% 41%	1900
	11th to 20th	Night	11% 12% 5% 8% 5% 4 4 4 7% 8% 32%	1877
	21st to end	Night	12% 10% 3 7% 4 5% 5% 4 6% 8% 37%	1549
May	1st to 10th	Night	18% 13% 3 7% 3 4 4 3 6% 6% 32%	2540
	11th to 20th	Night	12% 7% 2 5% 4 5% 6% 5% 6% 8% 40%	2517
	21st to end	Night	14% 6% 3 7% 5% 5% 5% 4 7% 8% 36%	2762
June	1st to 10th	Night	12% 5% 3 4 4 3 4 4 7% 10% 44%	1316
	11th to 20th	Night	13% 5% 2 4 5% 5% 5% 4 6% 9% 43%	1140
	21st to end	Night	8% 5% 1 5% 3 4 3 4 6% 10% 50%	1209
July	1st to 10th	Night	6% 4 2 5% 3 3 4 4 8% 10% 51%	2220
	11th to 20th	Night	4 3 1 4 3 4 4 4 6% 9% 58%	2343
	21st to end	Night	3 2 1 4 3 3 3 4 6% 8% 64%	2761
August	1st to 10th	Night	7% 5% 2 5% 3 3 3 2 5% 6% 58%	2528
	11th to 20th	Night	4 3 2 5% 4 4 4 4 6% 9% 56%	2589
	21st to end	Night	7% 4 2 4 3 3 4 4 5% 8% 57%	3382
September	1st to 10th	Night	9% 4 1 5% 3 4 4 3 5% 7% 55%	1900
	11th to 20th	Night	9% 6% 2 5% 4 4 4 4 5% 8% 49%	1900
	21st to end	Night	9% 6% 1 5% 4 4 4 3 5% 7% 51%	2138
October	1st to 10th	Night	9% 5% 2 6% 3 4 4 3 5% 7% 51%	3800
	11th to 20th	Night	5% 5% 2 5% 3 4 4 3 7% 12% 51%	3809
	21st to end	Night	7% 8% 3 7% 4 5% 5% 4 6% 8% 43%	4467
November	1st to 10th	Night	12% 14% 4 8% 6% 3 4 3 5% 6% 34%	2577
	11th to 20th	Night	6% 10% 4 12% 8% 6% 5% 4 5% 8% 31%	2660
	21st to end	Night	7% 11% 5% 11% 6% 6% 6% 4 5% 8% 32%	2676
December	1st to 10th	Night	7% 11% 4 13% 10% 7% 6% 4 6% 6% 26%	2850
	11th to 20th	Night	6% 12% 6% 14% 8% 7% 5% 5% 6% 6% 26%	3590
	21st to end	Night	4 7% 3 8% 5% 4 3 4 5% 6% 51%	5310

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% 7% 15% 18% 5%	2219
	11th to 20th	Day	56% 7% 15% 15% 6% 1	2454
	21st to end	Day	46% 7% 16% 27% 5%	2794
February	1st to 10th	Day	61% 5% 9% 16% 9%	1619
	11th to 20th	Day	56% 7% 12% 11% 12% 1	1674
	21st to end	Day	53% 7% 15% 16% 9% 1	1513
March	1st to 10th	Day	57% 5% 12% 21% 5%	3130
	11th to 20th	Day	46% 8% 21% 20% 5%	3389
	21st to end	Day	56% 7% 15% 13% 8%	4067
April	1st to 10th	Day	44% 7% 15% 21% 12% 1	2280
	11th to 20th	Day	54% 7% 13% 19% 6% 1	2254
	21st to end	Day	48% 6% 15% 22% 9% 1	2629
May	1st to 10th	Day	50% 7% 13% 22% 7% 1	4430
	11th to 20th	Day	41% 9% 13% 25% 11%	4392
	21st to end	Day	45% 8% 15% 25% 6%	4825
June	1st to 10th	Day	43% 7% 16% 23% 9% 2	2854
	11th to 20th	Day	48% 8% 13% 19% 10% 1	3040
	21st to end	Day	35% 8% 17% 30% 9% 1	2962
July	1st to 10th	Day	31% 10% 20% 26% 12% 1	4666
	11th to 20th	Day	21% 7% 17% 36% 17% 1	4537
	21st to end	Day	19% 4 12% 38% 20% 6%	4651
August	1st to 10th	Day	31% 6% 16% 28% 18% 1	4396
	11th to 20th	Day	26% 7% 18% 36% 13% 1	4289
	21st to end	Day	28% 5% 14% 38% 14% 1	4283
September	1st to 10th	Day	33% 5% 15% 27% 17% 3	2280
	11th to 20th	Day	39% 5% 15% 27% 12% 2	2280
	21st to end	Day	36% 5% 12% 30% 15% 2	2039
October	1st to 10th	Day	34% 5% 11% 35% 13% 2	3170
	11th to 20th	Day	30% 3 15% 36% 13% 2	3088
	21st to end	Day	40% 5% 16% 32% 7%	3091
November	1st to 10th	Day	53% 6% 12% 20% 8% 1	1569
	11th to 20th	Day	52% 7% 14% 19% 8% 1	1520
	21st to end	Day	52% 7% 19% 16% 5%	1501
December	1st to 10th	Day	59% 6% 15% 14% 6% 1	1330
	11th to 20th	Day	56% 7% 20% 11% 6%	1585
	21st to end	Day	39% 4 10% 23% 15% 9%	2328
January	1st to 10th	Night	50% 7% 17% 20% 5%	4726
	11th to 20th	Night	55% 6% 16% 16% 6% 1	4509
	21st to end	Night	45% 8% 18% 24% 4	4873
February	1st to 10th	Night	56% 6% 12% 16% 8% 1	2580
	11th to 20th	Night	52% 6% 14% 16% 10% 1	2403
	21st to end	Night	48% 6% 12% 23% 11%	1941
March	1st to 10th	Night	50% 8% 16% 20% 6%	3734
	11th to 20th	Night	41% 7% 22% 24% 5%	3584
	21st to end	Night	55% 7% 15% 15% 8%	3578
April	1st to 10th	Night	38% 7% 14% 25% 16% 1	1900
	11th to 20th	Night	48% 6% 11% 21% 12% 2	1877
	21st to end	Night	45% 7% 13% 24% 11%	1549
May	1st to 10th	Night	50% 6% 11% 22% 9% 1	2540
	11th to 20th	Night	37% 9% 12% 25% 16% 1	2518
	21st to end	Night	41% 9% 12% 30% 7% 1	2762
June	1st to 10th	Night	34% 7% 16% 29% 12% 2	1316
	11th to 20th	Night	37% 7% 16% 25% 13% 1	1140
	21st to end	Night	29% 7% 19% 33% 12% 1	1209
July	1st to 10th	Night	25% 9% 27% 28% 10% 1	2185
	11th to 20th	Night	21% 7% 16% 32% 22% 2	2301
	21st to end	Night	17% 5% 12% 40% 19% 7%	2674
August	1st to 10th	Night	27% 5% 14% 33% 20% 1	2520
	11th to 20th	Night	24% 6% 15% 37% 17% 1	2613
	21st to end	Night	25% 5% 15% 36% 17% 2	3382
September	1st to 10th	Night	28% 6% 10% 30% 21% 5%	1900
	11th to 20th	Night	33% 6% 13% 28% 18% 3	1900
	21st to end	Night	32% 6% 12% 31% 17% 2	2138
October	1st to 10th	Night	33% 5% 14% 32% 15% 2	3800
	11th to 20th	Night	27% 4 14% 41% 13% 1	3809
	21st to end	Night	39% 5% 11% 33% 12% 1	4467
November	1st to 10th	Night	52% 7% 12% 19% 9% 2	2577
	11th to 20th	Night	52% 6% 16% 18% 7% 1	2660
	21st to end	Night	51% 6% 18% 19% 6%	2676
December	1st to 10th	Night	57% 5% 14% 16% 7% 1	2850
	11th to 20th	Night	57% 7% 13% 18% 5% 1	3592
	21st to end	Night	34% 5% 11% 27% 16% 7%	5310

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	12% 13% 34% 28% 12% 2	180
	11th to 20th	Day	11% 14% 30% 31% 12% 1	248
	21st to end	Day	10% 14% 37% 29% 9%	297
February	1st to 10th	Day	17% 9% 40% 27% 6% 1	270
	11th to 20th	Day	11% 10% 39% 26% 11% 2	270
	21st to end	Day	4 8% 33% 40% 12% 2	225
March	1st to 10th	Day	16% 11% 37% 24% 9% 3	270
	11th to 20th	Day	13% 12% 36% 25% 10% 4	398
	21st to end	Day	15% 11% 34% 23% 14% 3	506
April	1st to 10th	Day	11% 17% 36% 29% 5% 2	460
	11th to 20th	Day	20% 14% 31% 26% 8% 1	452
	21st to end	Day	19% 10% 30% 27% 13%	631
May	1st to 10th	Day	14% 7% 27% 31% 17% 4	653
	11th to 20th	Day	12% 11% 25% 29% 16% 7%	675
	21st to end	Day	18% 9% 24% 25% 18% 6%	734
June	1st to 10th	Day	16% 14% 27% 24% 15% 4	680
	11th to 20th	Day	20% 14% 31% 22% 11% 3	680
	21st to end	Day	11% 9% 26% 30% 18% 5%	680
July	1st to 10th	Day	8% 6% 25% 34% 23% 5%	671
	11th to 20th	Day	7% 8% 29% 34% 18% 4	668
	21st to end	Day	6% 6% 26% 34% 21% 7%	739
August	1st to 10th	Day	11% 4 25% 36% 18% 6%	676
	11th to 20th	Day	10% 5% 25% 33% 20% 7%	608
	21st to end	Day	9% 6% 26% 38% 15% 5%	539
September	1st to 10th	Day	12% 10% 33% 27% 13% 4	490
	11th to 20th	Day	16% 10% 27% 33% 14% 1	490
	21st to end	Day	17% 13% 32% 25% 10% 3	314
October	1st to 10th	Day	18% 7% 31% 23% 19% 2	300
	11th to 20th	Day	12% 13% 36% 25% 12% 2	300
	21st to end	Day	14% 17% 38% 22% 7% 2	330
November	1st to 10th	Day	19% 12% 32% 27% 9% 1	279
	11th to 20th	Day	11% 14% 39% 27% 9%	270
	21st to end	Day	12% 10% 43% 25% 9% 1	270
December	1st to 10th	Day	12% 9% 44% 23% 10% 2	270
	11th to 20th	Day	8% 13% 49% 22% 7% 1	243
	21st to end	Day	11% 9% 37% 31% 10% 3	198
January	1st to 10th	Night	8% 13% 39% 31% 8% 1	950
	11th to 20th	Night	11% 13% 40% 29% 7% 1	950
	21st to end	Night	12% 11% 40% 26% 10% 1	1045
February	1st to 10th	Night	11% 10% 33% 33% 11% 1	870
	11th to 20th	Night	12% 9% 41% 28% 9% 1	744
	21st to end	Night	7% 8% 29% 34% 17% 4	628
March	1st to 10th	Night	10% 9% 36% 33% 11% 1	760
	11th to 20th	Night	11% 9% 39% 30% 11% 1	760
	21st to end	Night	13% 7% 31% 36% 12% 1	689
April	1st to 10th	Night	11% 10% 33% 33% 12%	570
	11th to 20th	Night	16% 8% 36% 32% 7% 1	563
	21st to end	Night	16% 10% 31% 36% 7%	570
May	1st to 10th	Night	17% 5% 27% 36% 14% 1	570
	11th to 20th	Night	14% 8% 28% 32% 16% 2	561
	21st to end	Night	19% 7% 27% 29% 16% 3	617
June	1st to 10th	Night	14% 6% 31% 33% 15% 1	456
	11th to 20th	Night	16% 7% 28% 36% 13%	380
	21st to end	Night	10% 7% 25% 40% 16% 2	380
July	1st to 10th	Night	7% 3 25% 45% 19% 1	370
	11th to 20th	Night	8% 5% 26% 44% 17% 1	439
	21st to end	Night	4 4 28% 46% 17% 2	624
August	1st to 10th	Night	8% 3 23% 46% 17% 2	567
	11th to 20th	Night	8% 3 23% 41% 23% 2	564
	21st to end	Night	8% 4 27% 40% 20% 1	627
September	1st to 10th	Night	9% 4 24% 45% 16% 1	570
	11th to 20th	Night	12% 6% 23% 44% 14% 2	570
	21st to end	Night	12% 7% 31% 40% 10%	632
October	1st to 10th	Night	18% 7% 27% 35% 12% 1	760
	11th to 20th	Night	12% 9% 32% 35% 11% 1	779
	21st to end	Night	15% 10% 37% 31% 6%	1045
November	1st to 10th	Night	20% 10% 36% 27% 6%	943
	11th to 20th	Night	11% 11% 40% 27% 9% 2	950
	21st to end	Night	12% 11% 45% 25% 7% 1	950
December	1st to 10th	Night	12% 7% 39% 27% 11% 3	950
	11th to 20th	Night	11% 11% 39% 29% 9% 1	950
	21st to end	Night	14% 8% 38% 28% 11% 2	1045

Page generated at 2024-11-01 20:47:40. Version ac07

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