Dixon Lomax Memorial Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dixon Lomax Memorial Observing Site clear sky chart from 2005-11-06 to 2026-10-14.

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	14% 5% 2 5% 4 4 5% 4 6% 8% 43%	148902
	Night	16% 5% 2 5% 4 4 4 3 5% 7% 44%	142835
Transparency	Day	27% 33% 9% 14% 12% 5%	152639
	Night	28% 33% 7% 13% 13% 5%	147170
Seeing	Day	19% 9% 23% 24% 17% 8%	17585
	Night	19% 7% 21% 30% 20% 4	27571

By Month

Percentage Cloud Cover SE (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	19% 5% 2 4 3 3 3 2 4 5% 50%	5258
	11th to 20th	Day	11% 4 1 4 3 2 2 2 2 3 65%	5280
	21st to end	Day	22% 7% 2 6% 4 3 3 3 3 4 42%	5780
February	1st to 10th	Day	16% 6% 2 6% 4 3 4 4 5% 6% 45%	2069
	11th to 20th	Day	21% 6% 2 5% 3 2 3 3 5% 6% 43%	2048
	21st to end	Day	20% 5% 2 6% 4 4 3 2 5% 4 44%	1730
March	1st to 10th	Day	23% 6% 2 5% 3 3 4 3 4 5% 41%	4855
	11th to 20th	Day	12% 4 2 4 3 3 4 3 4 6% 56%	5090
	21st to end	Day	20% 4 2 5% 4 4 3 3 4 4 47%	5586
April	1st to 10th	Day	14% 3 2 4 3 4 5% 5% 5% 7% 45%	2310
	11th to 20th	Day	13% 4 2 4 4 4 4 4 5% 7% 48%	2507
	21st to end	Day	13% 4 2 4 4 4 4 3 6% 8% 49%	2730
May	1st to 10th	Day	14% 7% 3 7% 4 4 4 4 6% 8% 38%	7616
	11th to 20th	Day	16% 6% 2 7% 5% 5% 5% 4 7% 8% 35%	7626
	21st to end	Day	20% 6% 2 7% 5% 5% 5% 4 6% 8% 32%	8391
June	1st to 10th	Day	12% 6% 2 6% 6% 6% 6% 5% 8% 10% 34%	2730
	11th to 20th	Day	6% 4 2 6% 5% 6% 7% 5% 9% 12% 38%	2730
	21st to end	Day	7% 4 2 6% 5% 5% 7% 6% 8% 12% 39%	2730
July	1st to 10th	Day	5% 4 2 6% 5% 6% 7% 5% 8% 12% 40%	7680
	11th to 20th	Day	9% 5% 2 6% 6% 6% 7% 6% 9% 12% 33%	7680
	21st to end	Day	10% 5% 3 8% 6% 8% 7% 6% 9% 11% 27%	8340
August	1st to 10th	Day	13% 7% 3 7% 5% 6% 6% 6% 8% 11% 29%	6014
	11th to 20th	Day	7% 3 2 5% 4 5% 5% 4 7% 12% 46%	5910
	21st to end	Day	8% 4 2 5% 4 4 5% 4 7% 9% 49%	5968
September	1st to 10th	Day	10% 5% 2 6% 6% 5% 6% 4 7% 8% 40%	2310
	11th to 20th	Day	16% 5% 2 5% 4 5% 5% 4 6% 7% 39%	2310
	21st to end	Day	16% 5% 2 4 4 4 5% 3 4 7% 46%	2310
October	1st to 10th	Day	16% 5% 1 3 3 3 3 3 4 6% 53%	2310
	11th to 20th	Day	13% 4 1 4 2 2 2 3 4 5% 59%	2046
	21st to end	Day	16% 4 1 3 2 3 3 2 4 4 58%	2200
November	1st to 10th	Day	15% 4 1 4 2 3 2 3 3 5% 58%	1930
	11th to 20th	Day	15% 5% 1 3 3 3 3 2 5% 6% 55%	1890
	21st to end	Day	16% 4 1 4 3 3 3 3 5% 6% 51%	1890
December	1st to 10th	Day	20% 5% 2 4 3 3 3 2 4 4 50%	3020
	11th to 20th	Day	20% 5% 2 5% 4 3 4 4 4 5% 44%	3463
	21st to end	Day	25% 4 1 3 2 2 3 2 4 6% 47%	4565
January	1st to 10th	Night	18% 4 2 4 3 3 3 3 4 5% 53%	7635
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 4 5% 56%	7680
	21st to end	Night	21% 6% 2 5% 3 3 3 2 3 4 47%	8401
February	1st to 10th	Night	15% 5% 1 5% 4 3 4 3 5% 6% 49%	2549
	11th to 20th	Night	23% 6% 1 5% 3 3 3 3 5% 5% 44%	2458
	21st to end	Night	20% 5% 2 5% 3 4 4 4 5% 6% 42%	2076
March	1st to 10th	Night	22% 6% 2 5% 4 3 4 3 5% 6% 40%	5216
	11th to 20th	Night	11% 3 1 3 3 3 3 3 6% 7% 56%	5090
	21st to end	Night	18% 5% 2 5% 4 3 4 3 4 6% 46%	5588
April	1st to 10th	Night	15% 4 1 5% 3 3 4 4 5% 7% 49%	2310
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 8% 52%	2078
	21st to end	Night	12% 5% 2 5% 4 3 4 3 5% 7% 50%	1890
May	1st to 10th	Night	15% 7% 2 7% 5% 4 5% 5% 6% 8% 35%	5237
	11th to 20th	Night	20% 6% 2 6% 4 4 5% 3 5% 8% 37%	5234
	21st to end	Night	21% 6% 3 6% 4 4 4 4 6% 8% 33%	5761
June	1st to 10th	Night	11% 7% 2 7% 6% 5% 5% 6% 7% 9% 36%	1890
	11th to 20th	Night	9% 5% 2 5% 4 5% 5% 5% 7% 10% 42%	1890
	21st to end	Night	8% 3 2 5% 5% 4 6% 6% 8% 11% 42%	1890
July	1st to 10th	Night	10% 6% 3 7% 6% 6% 6% 5% 7% 11% 33%	5278
	11th to 20th	Night	11% 6% 2 7% 5% 6% 6% 6% 9% 12% 30%	5277
	21st to end	Night	15% 7% 3 8% 6% 5% 6% 5% 7% 11% 28%	5736
August	1st to 10th	Night	17% 8% 2 7% 5% 6% 6% 5% 8% 10% 27%	4135
	11th to 20th	Night	13% 5% 2 6% 4 4 5% 4 7% 12% 37%	4118
	21st to end	Night	11% 6% 2 6% 4 5% 5% 4 6% 9% 42%	5109
September	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 9% 38%	2310
	11th to 20th	Night	17% 6% 2 7% 4 4 5% 3 6% 7% 37%	2310
	21st to end	Night	16% 5% 2 6% 4 4 4 3 4 6% 45%	2310
October	1st to 10th	Night	16% 4 1 4 3 3 4 3 4 5% 52%	2310
	11th to 20th	Night	14% 4 2 5% 3 3 3 2 4 5% 56%	2420
	21st to end	Night	15% 4 1 4 2 3 3 2 4 4 58%	2640
November	1st to 10th	Night	15% 5% 2 4 3 3 3 3 4 4 56%	2584
	11th to 20th	Night	16% 5% 1 4 3 3 2 2 4 5% 54%	2730
	21st to end	Night	17% 5% 2 4 3 4 4 4 5% 6% 48%	2730
December	1st to 10th	Night	18% 5% 1 4 3 3 3 2 4 4 51%	4380
	11th to 20th	Night	21% 5% 2 5% 3 3 3 3 4 4 46%	4952
	21st to end	Night	24% 5% 2 4 3 3 3 3 4 6% 44%	6633

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	31% 19% 4 18% 21% 6%	5259
	11th to 20th	Day	20% 19% 2 9% 32% 18%	5280
	21st to end	Day	40% 21% 2 11% 14% 12%	5780
February	1st to 10th	Day	17% 58% 3 11% 9% 3	2069
	11th to 20th	Day	20% 58% 3 8% 9% 3	2058
	21st to end	Day	19% 58% 2 6% 9% 5%	1730
March	1st to 10th	Day	38% 28% 3 10% 12% 10%	4855
	11th to 20th	Day	20% 27% 3 9% 22% 19%	5090
	21st to end	Day	30% 27% 2 19% 16% 6%	5586
April	1st to 10th	Day	18% 59% 5% 8% 9% 2	2310
	11th to 20th	Day	16% 59% 5% 9% 9% 3	2507
	21st to end	Day	16% 59% 5% 11% 8% 1	2730
May	1st to 10th	Day	37% 23% 9% 20% 10% 1	7651
	11th to 20th	Day	37% 23% 12% 18% 8% 2	7630
	21st to end	Day	44% 23% 9% 11% 12% 2	8405
June	1st to 10th	Day	19% 59% 6% 10% 4 1	2730
	11th to 20th	Day	15% 60% 11% 9% 5%	2730
	21st to end	Day	14% 59% 10% 10% 5%	2730
July	1st to 10th	Day	25% 27% 22% 22% 4	7615
	11th to 20th	Day	33% 28% 24% 14% 1	7611
	21st to end	Day	39% 25% 13% 15% 6% 1	8156
August	1st to 10th	Day	37% 31% 14% 15% 3	6001
	11th to 20th	Day	18% 30% 22% 20% 9% 1	5949
	21st to end	Day	19% 29% 13% 24% 15% 1	5968
September	1st to 10th	Day	17% 55% 8% 11% 10% 1	2310
	11th to 20th	Day	19% 54% 8% 10% 7% 1	2310
	21st to end	Day	19% 54% 7% 9% 10% 1	2310
October	1st to 10th	Day	17% 35% 3 12% 27% 6%	3700
	11th to 20th	Day	10% 35% 2 8% 22% 22%	3286
	21st to end	Day	20% 35% 2 16% 16% 11%	3538
November	1st to 10th	Day	19% 53% 4 9% 11% 5%	1930
	11th to 20th	Day	15% 53% 3 11% 13% 4	1890
	21st to end	Day	15% 53% 5% 9% 15% 3	1890
December	1st to 10th	Day	24% 34% 2 11% 18% 11%	3020
	11th to 20th	Day	32% 31% 3 9% 16% 9%	3460
	21st to end	Day	31% 25% 4 22% 17% 1	4565
January	1st to 10th	Night	29% 20% 7% 17% 20% 8%	7636
	11th to 20th	Night	25% 20% 2 12% 28% 14%	7680
	21st to end	Night	34% 21% 3 12% 19% 10%	8401
February	1st to 10th	Night	15% 59% 3 11% 9% 3	2549
	11th to 20th	Night	22% 57% 3 8% 9% 2	2459
	21st to end	Night	19% 58% 2 8% 9% 4	2076
March	1st to 10th	Night	36% 28% 4 9% 18% 5%	5216
	11th to 20th	Night	18% 27% 3 12% 22% 18%	5090
	21st to end	Night	30% 27% 3 17% 14% 8%	5588
April	1st to 10th	Night	17% 59% 4 7% 10% 3	2310
	11th to 20th	Night	15% 59% 3 11% 8% 3	2078
	21st to end	Night	16% 58% 5% 12% 8% 1	1890
May	1st to 10th	Night	39% 23% 9% 19% 8% 2	5264
	11th to 20th	Night	38% 23% 12% 17% 9% 1	5235
	21st to end	Night	42% 24% 8% 15% 10% 1	5771
June	1st to 10th	Night	19% 60% 7% 7% 5% 2	1890
	11th to 20th	Night	16% 60% 9% 9% 5%	1890
	21st to end	Night	14% 59% 11% 10% 6%	1890
July	1st to 10th	Night	32% 26% 22% 17% 2	5235
	11th to 20th	Night	35% 28% 22% 13% 1	5226
	21st to end	Night	43% 23% 15% 13% 4 2	5606
August	1st to 10th	Night	41% 31% 14% 13% 2	4124
	11th to 20th	Night	27% 29% 20% 16% 8%	4145
	21st to end	Night	25% 29% 12% 22% 12% 1	5109
September	1st to 10th	Night	19% 55% 6% 10% 9% 1	2310
	11th to 20th	Night	21% 56% 6% 11% 6% 1	2310
	21st to end	Night	22% 54% 6% 9% 8% 1	2310
October	1st to 10th	Night	18% 36% 7% 10% 24% 5%	3700
	11th to 20th	Night	9% 34% 3 11% 23% 20%	3919
	21st to end	Night	19% 35% 1 13% 18% 13%	4252
November	1st to 10th	Night	20% 53% 4 9% 11% 4	2584
	11th to 20th	Night	16% 53% 3 8% 14% 6%	2730
	21st to end	Night	17% 54% 3 11% 13% 3	2730
December	1st to 10th	Night	25% 35% 2 12% 20% 7%	4380
	11th to 20th	Night	31% 31% 5% 11% 15% 7%	4954
	21st to end	Night	34% 25% 4 21% 15% 2	6633

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	27% 17% 39% 13% 3 1	330
	11th to 20th	Day	29% 21% 31% 15% 4 1	330
	21st to end	Day	31% 19% 35% 12% 3 1	363
February	1st to 10th	Day	22% 18% 41% 16% 3	330
	11th to 20th	Day	39% 17% 33% 11% 1	330
	21st to end	Day	33% 19% 35% 11% 1	273
March	1st to 10th	Day	27% 15% 30% 22% 7%	449
	11th to 20th	Day	28% 13% 33% 20% 5% 1	540
	21st to end	Day	26% 15% 31% 21% 7% 1	594
April	1st to 10th	Day	24% 12% 27% 27% 9% 2	540
	11th to 20th	Day	17% 13% 33% 22% 12% 2	532
	21st to end	Day	19% 9% 26% 27% 15% 5%	540
May	1st to 10th	Day	16% 13% 30% 23% 11% 7%	543
	11th to 20th	Day	21% 6% 20% 25% 19% 9%	567
	21st to end	Day	20% 7% 19% 24% 19% 11%	617
June	1st to 10th	Day	16% 5% 16% 30% 22% 12%	570
	11th to 20th	Day	9% 5% 18% 29% 23% 16%	570
	21st to end	Day	10% 3 18% 33% 22% 15%	570
July	1st to 10th	Day	10% 2 10% 27% 29% 21%	565
	11th to 20th	Day	9% 3 8% 27% 29% 25%	564
	21st to end	Day	8% 2 9% 30% 29% 21%	620
August	1st to 10th	Day	20% 5% 13% 21% 23% 18%	566
	11th to 20th	Day	11% 4 9% 25% 34% 16%	559
	21st to end	Day	15% 4 10% 27% 28% 16%	627
September	1st to 10th	Day	11% 2 14% 28% 31% 14%	570
	11th to 20th	Day	17% 4 12% 24% 32% 11%	570
	21st to end	Day	19% 4 18% 28% 24% 7%	570
October	1st to 10th	Day	20% 4 18% 32% 18% 8%	570
	11th to 20th	Day	15% 6% 25% 32% 18% 3	542
	21st to end	Day	22% 7% 26% 28% 14% 3	583
November	1st to 10th	Day	22% 6% 31% 25% 13% 3	408
	11th to 20th	Day	20% 18% 34% 23% 5%	330
	21st to end	Day	18% 12% 37% 23% 8% 2	330
December	1st to 10th	Day	29% 15% 33% 18% 3 1	330
	11th to 20th	Day	27% 10% 38% 18% 5% 1	330
	21st to end	Day	34% 12% 31% 17% 5% 2	363
January	1st to 10th	Night	24% 11% 33% 26% 6%	840
	11th to 20th	Night	22% 11% 32% 28% 6%	840
	21st to end	Night	23% 11% 37% 26% 3	924
February	1st to 10th	Night	21% 9% 31% 34% 5%	840
	11th to 20th	Night	26% 13% 33% 25% 2	823
	21st to end	Night	23% 12% 35% 27% 3	692
March	1st to 10th	Night	21% 9% 30% 34% 5%	840
	11th to 20th	Night	20% 9% 35% 28% 8% 1	840
	21st to end	Night	20% 11% 28% 31% 9%	924
April	1st to 10th	Night	19% 11% 28% 32% 10%	840
	11th to 20th	Night	15% 9% 23% 36% 15% 1	672
	21st to end	Night	16% 5% 20% 37% 20% 2	630
May	1st to 10th	Night	15% 5% 25% 33% 22% 1	630
	11th to 20th	Night	20% 4 17% 32% 22% 5%	621
	21st to end	Night	17% 3 12% 29% 30% 9%	683
June	1st to 10th	Night	14% 3 11% 33% 32% 7%	630
	11th to 20th	Night	11% 2 10% 32% 31% 14%	630
	21st to end	Night	8% 3 8% 33% 41% 8%	630
July	1st to 10th	Night	13% 3 5% 22% 43% 13%	615
	11th to 20th	Night	13% 3 4 21% 44% 16%	612
	21st to end	Night	10% 2 7% 25% 44% 12%	690
August	1st to 10th	Night	19% 1 5% 23% 40% 12%	627
	11th to 20th	Night	17% 3 6% 24% 38% 11%	624
	21st to end	Night	13% 4 6% 27% 38% 12%	717
September	1st to 10th	Night	13% 3 9% 29% 38% 9%	840
	11th to 20th	Night	19% 4 11% 24% 35% 6%	840
	21st to end	Night	17% 3 12% 35% 29% 4	840
October	1st to 10th	Night	18% 4 14% 32% 25% 6%	840
	11th to 20th	Night	16% 4 19% 37% 20% 3	813
	21st to end	Night	18% 6% 20% 36% 17% 3	880
November	1st to 10th	Night	17% 6% 20% 36% 18% 3	820
	11th to 20th	Night	19% 8% 26% 33% 13% 1	840
	21st to end	Night	20% 6% 28% 33% 12% 1	840
December	1st to 10th	Night	26% 8% 26% 31% 7% 1	840
	11th to 20th	Night	22% 7% 28% 33% 9% 1	840
	21st to end	Night	29% 8% 24% 33% 6%	924

Page generated at 2026-10-11 05:06:29. Version ac07

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