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 2024-04-03.

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% 8% 4 7% 6% 4 5% 5% 6% 8% 38%	78407
	Night	7% 8% 4 8% 7% 4 5% 5% 6% 8% 38%	81694
Transparency	Day	44% 7% 15% 23% 10% 1	78097
	Night	43% 6% 14% 23% 11% 2	81525
Seeing	Day	13% 10% 31% 29% 14% 3	15031
	Night	12% 8% 34% 33% 11% 1	24739

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% 10% 9% 6% 8% 8% 5% 6% 26%	2219
	11th to 20th	Day	4 7% 4 7% 11% 6% 11% 12% 8% 7% 21%	2454
	21st to end	Day	4 10% 5% 10% 7% 4 5% 6% 6% 7% 37%	2794
February	1st to 10th	Day	7% 11% 7% 13% 9% 5% 8% 6% 6% 5% 24%	1619
	11th to 20th	Day	7% 10% 5% 11% 10% 5% 7% 8% 6% 5% 26%	1665
	21st to end	Day	4 9% 7% 10% 11% 6% 7% 6% 8% 8% 25%	1513
March	1st to 10th	Day	9% 13% 7% 10% 9% 6% 5% 6% 6% 8% 21%	1900
	11th to 20th	Day	7% 12% 5% 8% 6% 4 5% 6% 6% 8% 34%	2028
	21st to end	Day	9% 11% 6% 9% 8% 4 6% 6% 7% 9% 25%	2446
April	1st to 10th	Day	7% 10% 4 7% 7% 4 6% 5% 6% 7% 37%	2185
	11th to 20th	Day	14% 12% 5% 7% 7% 3 6% 6% 6% 8% 26%	2131
	21st to end	Day	16% 9% 3 6% 7% 3 5% 4 5% 8% 35%	2490
May	1st to 10th	Day	13% 7% 3 6% 6% 4 4 5% 6% 7% 38%	2520
	11th to 20th	Day	8% 8% 4 5% 6% 4 5% 6% 6% 9% 39%	2478
	21st to end	Day	19% 7% 3 5% 6% 4 5% 6% 6% 8% 32%	2724
June	1st to 10th	Day	16% 6% 3 5% 5% 3 5% 6% 7% 8% 37%	2703
	11th to 20th	Day	18% 6% 3 6% 6% 3 5% 5% 5% 8% 32%	2880
	21st to end	Day	9% 4 2 5% 5% 3 6% 6% 6% 9% 45%	2807
July	1st to 10th	Day	6% 4 2 4 4 4 5% 5% 7% 9% 51%	2700
	11th to 20th	Day	7% 4 1 5% 4 2 4 5% 6% 10% 51%	2630
	21st to end	Day	5% 3 2 3 4 3 4 4 6% 7% 59%	2742
August	1st to 10th	Day	9% 4 1 4 5% 3 5% 5% 5% 8% 51%	2507
	11th to 20th	Day	9% 4 2 5% 4 3 4 6% 5% 9% 51%	2423
	21st to end	Day	10% 4 2 5% 4 3 3 5% 5% 7% 53%	2441
September	1st to 10th	Day	12% 4 3 4 5% 3 4 4 5% 8% 48%	2160
	11th to 20th	Day	12% 8% 2 5% 4 3 3 4 4 7% 46%	2160
	21st to end	Day	14% 6% 2 5% 5% 2 3 4 5% 8% 46%	1933
October	1st to 10th	Day	14% 9% 3 6% 5% 2 3 4 4 6% 42%	1800
	11th to 20th	Day	10% 8% 4 8% 5% 3 4 4 5% 7% 41%	1764
	21st to end	Day	9% 13% 5% 9% 6% 3 4 4 5% 7% 34%	1782
November	1st to 10th	Day	12% 11% 7% 9% 6% 3 5% 5% 4 6% 32%	1542
	11th to 20th	Day	6% 10% 5% 10% 10% 4 6% 6% 5% 6% 32%	1520
	21st to end	Day	10% 10% 5% 8% 8% 5% 6% 5% 4 8% 31%	1501
December	1st to 10th	Day	8% 11% 6% 12% 10% 6% 7% 5% 6% 6% 24%	1330
	11th to 20th	Day	5% 12% 6% 12% 9% 5% 6% 5% 6% 8% 26%	1588
	21st to end	Day	6% 7% 3 7% 7% 4 4 4 5% 4 48%	2328
January	1st to 10th	Night	3 10% 6% 11% 9% 4 7% 6% 7% 7% 30%	4726
	11th to 20th	Night	3 6% 4 10% 11% 7% 11% 8% 8% 8% 24%	4509
	21st to end	Night	5% 11% 5% 9% 6% 3 5% 6% 6% 7% 36%	4873
February	1st to 10th	Night	6% 12% 6% 11% 9% 4 7% 7% 7% 8% 23%	2580
	11th to 20th	Night	7% 11% 4 10% 8% 5% 6% 6% 7% 8% 29%	2402
	21st to end	Night	4 8% 5% 10% 8% 5% 8% 6% 6% 8% 32%	1941
March	1st to 10th	Night	7% 9% 5% 10% 10% 4 6% 5% 6% 7% 30%	2280
	11th to 20th	Night	7% 10% 5% 8% 6% 4 6% 5% 6% 8% 36%	2148
	21st to end	Night	9% 9% 5% 10% 8% 4 5% 5% 6% 9% 30%	2152
April	1st to 10th	Night	7% 9% 4 6% 6% 3 5% 6% 6% 8% 41%	1820
	11th to 20th	Night	12% 12% 5% 7% 6% 2 5% 5% 7% 8% 32%	1777
	21st to end	Night	12% 10% 4 6% 5% 4 5% 5% 6% 7% 35%	1468
May	1st to 10th	Night	12% 8% 2 4 4 3 6% 5% 7% 9% 41%	1440
	11th to 20th	Night	11% 7% 2 4 5% 3 5% 6% 6% 7% 43%	1417
	21st to end	Night	17% 6% 3 6% 5% 3 5% 6% 7% 9% 33%	1552
June	1st to 10th	Night	12% 5% 3 4 4 2 4 5% 6% 10% 45%	1247
	11th to 20th	Night	14% 4 3 4 5% 3 5% 5% 5% 10% 42%	1080
	21st to end	Night	9% 4 1 3 5% 3 4 5% 5% 10% 50%	1145
July	1st to 10th	Night	6% 4 2 3 4 2 4 5% 6% 8% 57%	1260
	11th to 20th	Night	6% 3 1 3 3 2 4 5% 6% 10% 57%	1327
	21st to end	Night	4 1 1 3 4 2 3 5% 6% 7% 64%	1576
August	1st to 10th	Night	6% 4 1 4 4 2 4 3 6% 8% 58%	1432
	11th to 20th	Night	5% 3 2 3 4 2 4 4 6% 9% 57%	1475
	21st to end	Night	8% 4 1 3 3 2 3 4 4 8% 60%	1914
September	1st to 10th	Night	10% 4 2 4 4 3 4 4 6% 7% 53%	1800
	11th to 20th	Night	10% 5% 2 4 5% 3 4 5% 5% 8% 50%	1800
	21st to end	Night	10% 6% 2 4 5% 3 4 5% 5% 7% 51%	2024
October	1st to 10th	Night	14% 6% 2 6% 5% 3 3 4 5% 8% 45%	2160
	11th to 20th	Night	8% 8% 3 6% 5% 3 4 3 6% 8% 46%	2178
	21st to end	Night	9% 11% 5% 8% 6% 3 5% 5% 6% 8% 33%	2574
November	1st to 10th	Night	13% 14% 5% 7% 7% 2 4 4 4 6% 34%	2531
	11th to 20th	Night	7% 9% 5% 10% 9% 5% 6% 5% 5% 8% 31%	2660
	21st to end	Night	7% 10% 5% 10% 7% 4 7% 5% 4 8% 32%	2676
December	1st to 10th	Night	7% 10% 5% 11% 10% 6% 7% 6% 5% 6% 26%	2850
	11th to 20th	Night	6% 11% 6% 12% 10% 5% 5% 6% 6% 6% 26%	3590
	21st to end	Night	5% 7% 3 7% 6% 4 4 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	60% 6% 13% 17% 4	1900
	11th to 20th	Day	48% 6% 17% 21% 7%	2028
	21st to end	Day	53% 8% 17% 15% 6%	2446
April	1st to 10th	Day	45% 7% 15% 21% 12% 1	2185
	11th to 20th	Day	55% 6% 13% 18% 6% 1	2134
	21st to end	Day	48% 6% 15% 22% 8% 1	2490
May	1st to 10th	Day	44% 6% 12% 26% 10% 1	2520
	11th to 20th	Day	40% 9% 11% 30% 11%	2482
	21st to end	Day	50% 7% 13% 20% 9% 1	2724
June	1st to 10th	Day	43% 7% 17% 24% 8% 1	2703
	11th to 20th	Day	48% 8% 14% 19% 10% 1	2880
	21st to end	Day	35% 9% 17% 30% 9% 1	2807
July	1st to 10th	Day	28% 8% 18% 32% 13% 1	2626
	11th to 20th	Day	27% 8% 17% 27% 19% 1	2549
	21st to end	Day	24% 5% 14% 36% 19% 2	2590
August	1st to 10th	Day	30% 7% 17% 31% 13% 2	2491
	11th to 20th	Day	30% 7% 17% 30% 14% 2	2423
	21st to end	Day	30% 5% 11% 32% 19% 2	2441
September	1st to 10th	Day	34% 6% 15% 26% 17% 3	2160
	11th to 20th	Day	38% 4 15% 28% 13% 2	2160
	21st to end	Day	37% 5% 12% 30% 14% 2	1933
October	1st to 10th	Day	44% 6% 13% 25% 11% 1	1800
	11th to 20th	Day	42% 4 13% 28% 11% 1	1764
	21st to end	Day	50% 5% 17% 21% 6%	1782
November	1st to 10th	Day	53% 6% 12% 19% 8% 1	1542
	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	52% 7% 16% 19% 6%	2280
	11th to 20th	Night	46% 6% 14% 24% 8% 1	2148
	21st to end	Night	51% 6% 16% 18% 9%	2152
April	1st to 10th	Night	39% 6% 13% 25% 15% 1	1820
	11th to 20th	Night	48% 6% 12% 20% 12% 2	1777
	21st to end	Night	47% 7% 13% 23% 10%	1468
May	1st to 10th	Night	38% 7% 13% 25% 15% 2	1440
	11th to 20th	Night	38% 6% 12% 28% 15% 1	1418
	21st to end	Night	46% 8% 13% 22% 10% 1	1552
June	1st to 10th	Night	34% 7% 17% 30% 11% 1	1247
	11th to 20th	Night	38% 7% 17% 24% 13% 1	1080
	21st to end	Night	29% 7% 19% 32% 12% 1	1145
July	1st to 10th	Night	23% 8% 19% 35% 13% 2	1225
	11th to 20th	Night	22% 7% 17% 32% 18% 3	1285
	21st to end	Night	18% 6% 13% 38% 22% 3	1488
August	1st to 10th	Night	24% 6% 16% 33% 18% 2	1424
	11th to 20th	Night	23% 7% 15% 36% 17% 2	1475
	21st to end	Night	24% 5% 12% 31% 25% 4	1914
September	1st to 10th	Night	30% 6% 10% 29% 20% 4	1800
	11th to 20th	Night	32% 6% 13% 27% 19% 3	1800
	21st to end	Night	33% 6% 12% 32% 16% 2	2024
October	1st to 10th	Night	39% 6% 15% 25% 14% 1	2160
	11th to 20th	Night	37% 5% 15% 28% 13% 1	2178
	21st to end	Night	49% 6% 13% 22% 9% 1	2574
November	1st to 10th	Night	52% 7% 12% 19% 9% 2	2531
	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% 28% 5% 1	429
	11th to 20th	Day	22% 13% 30% 26% 8% 1	412
	21st to end	Day	19% 10% 31% 27% 13%	582
May	1st to 10th	Day	12% 7% 27% 32% 18% 4	603
	11th to 20th	Day	12% 12% 24% 29% 16% 8%	625
	21st to end	Day	19% 9% 24% 24% 18% 6%	679
June	1st to 10th	Day	15% 12% 27% 25% 16% 4	630
	11th to 20th	Day	19% 13% 32% 22% 11% 3	630
	21st to end	Day	11% 8% 25% 32% 19% 6%	630
July	1st to 10th	Day	8% 6% 26% 35% 21% 4	621
	11th to 20th	Day	7% 9% 31% 33% 17% 3	618
	21st to end	Day	6% 7% 26% 35% 20% 7%	684
August	1st to 10th	Day	11% 4 24% 37% 19% 5%	626
	11th to 20th	Day	10% 6% 25% 32% 20% 7%	561
	21st to end	Day	10% 5% 25% 38% 16% 6%	495
September	1st to 10th	Day	13% 11% 35% 27% 11% 3	450
	11th to 20th	Day	16% 8% 26% 34% 14% 1	450
	21st to end	Day	19% 10% 31% 26% 11% 3	284
October	1st to 10th	Day	20% 7% 30% 22% 20% 2	270
	11th to 20th	Day	13% 12% 35% 25% 12% 2	270
	21st to end	Day	15% 18% 36% 21% 7% 2	297
November	1st to 10th	Day	20% 12% 32% 26% 9% 1	270
	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	12% 11% 33% 34% 11%	546
	11th to 20th	Night	17% 8% 36% 32% 7% 1	533
	21st to end	Night	17% 10% 30% 36% 7%	540
May	1st to 10th	Night	16% 5% 28% 37% 13% 1	540
	11th to 20th	Night	14% 8% 27% 33% 17% 2	531
	21st to end	Night	20% 7% 27% 28% 16% 3	584
June	1st to 10th	Night	14% 5% 31% 33% 16% 1	432
	11th to 20th	Night	16% 7% 28% 35% 13%	360
	21st to end	Night	11% 6% 24% 41% 17% 2	360
July	1st to 10th	Night	8% 3 26% 46% 17% 1	350
	11th to 20th	Night	8% 5% 27% 44% 15% 1	415
	21st to end	Night	4 4 28% 46% 17% 1	591
August	1st to 10th	Night	8% 3 23% 47% 16% 2	537
	11th to 20th	Night	8% 3 23% 40% 24% 2	534
	21st to end	Night	9% 4 25% 41% 20% 1	594
September	1st to 10th	Night	10% 4 25% 45% 15% 1	540
	11th to 20th	Night	11% 5% 22% 45% 14% 2	540
	21st to end	Night	13% 7% 30% 39% 10% 1	598
October	1st to 10th	Night	18% 7% 26% 35% 12% 1	720
	11th to 20th	Night	12% 9% 31% 35% 12% 1	738
	21st to end	Night	15% 10% 37% 31% 6%	990
November	1st to 10th	Night	20% 10% 36% 27% 6%	925
	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 2024-03-31 04:08:49. Version ac07

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