Hobbs Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hobbs Observatory clear sky chart from 2005-11-06 to 2024-11-06.

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% 9% 3 8% 5% 4 4 4 5% 7% 37%	101635
	Night	14% 9% 4 8% 5% 4 4 3 5% 6% 38%	97537
Transparency	Day	46% 3 12% 26% 12% 1	105179
	Night	47% 3 11% 25% 13% 1	102133
Seeing	Day	17% 9% 29% 26% 14% 4	16021
	Night	18% 8% 31% 31% 11% 1	25873

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	11% 18% 8% 15% 6% 4 4 2 4 5% 23%	2527
	11th to 20th	Day	8% 12% 5% 16% 7% 9% 9% 8% 6% 3 17%	2530
	21st to end	Day	14% 18% 7% 13% 5% 4 4 3 4 6% 22%	2979
February	1st to 10th	Day	9% 11% 6% 10% 6% 5% 6% 4 5% 6% 32%	1710
	11th to 20th	Day	10% 10% 4 8% 6% 5% 4 4 6% 7% 35%	1664
	21st to end	Day	13% 11% 4 11% 5% 5% 4 4 4 7% 31%	1564
March	1st to 10th	Day	14% 9% 3 5% 4 3 3 2 3 5% 48%	3174
	11th to 20th	Day	10% 9% 3 9% 5% 5% 4 3 5% 7% 39%	3480
	21st to end	Day	22% 12% 3 12% 5% 4 4 2 5% 5% 27%	3995
April	1st to 10th	Day	17% 12% 3 8% 5% 4 4 3 5% 6% 33%	2280
	11th to 20th	Day	22% 10% 4 7% 5% 4 4 3 5% 5% 31%	2254
	21st to end	Day	21% 11% 3 7% 6% 4 4 4 4 6% 30%	2369
May	1st to 10th	Day	17% 7% 2 6% 4 4 4 3 5% 7% 41%	4399
	11th to 20th	Day	16% 6% 2 6% 4 5% 4 3 6% 7% 42%	4399
	21st to end	Day	19% 7% 2 6% 5% 4 4 4 5% 5% 38%	4824
June	1st to 10th	Day	14% 5% 2 6% 4 3 4 4 6% 8% 43%	2660
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 5% 9% 37%	2660
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 7% 9% 40%	2660
July	1st to 10th	Day	14% 4 2 6% 4 5% 6% 5% 8% 9% 38%	4440
	11th to 20th	Day	6% 3 1 4 4 4 4 4 6% 9% 55%	4440
	21st to end	Day	9% 5% 2 6% 5% 4 5% 4 5% 7% 47%	4813
August	1st to 10th	Day	14% 6% 2 6% 4 5% 4 4 6% 8% 42%	4267
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 6% 8% 46%	4041
	21st to end	Day	13% 6% 2 7% 4 5% 4 4 6% 8% 42%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 3 3 4 5% 7% 48%	2280
	11th to 20th	Day	13% 5% 3 6% 5% 4 4 3 5% 8% 46%	2280
	21st to end	Day	16% 6% 3 5% 4 4 4 4 5% 7% 43%	2018
October	1st to 10th	Day	16% 6% 3 6% 4 4 4 3 5% 6% 43%	1900
	11th to 20th	Day	17% 12% 3 7% 4 5% 5% 4 4 6% 35%	1900
	21st to end	Day	21% 12% 3 6% 4 3 3 2 4 5% 36%	1970
November	1st to 10th	Day	15% 9% 3 7% 5% 4 3 3 4 7% 39%	1717
	11th to 20th	Day	16% 14% 5% 10% 5% 5% 4 3 5% 5% 28%	1520
	21st to end	Day	15% 12% 4 7% 6% 3 3 3 6% 5% 36%	1520
December	1st to 10th	Day	10% 13% 5% 13% 8% 7% 6% 4 4 6% 24%	1520
	11th to 20th	Day	12% 15% 7% 11% 7% 5% 5% 3 4 4 26%	1918
	21st to end	Day	22% 20% 7% 14% 6% 4 3 2 3 3 19%	2783
January	1st to 10th	Night	10% 16% 8% 14% 5% 4 4 3 4 4 29%	4428
	11th to 20th	Night	9% 12% 6% 14% 7% 6% 8% 7% 6% 4 20%	4440
	21st to end	Night	14% 20% 7% 12% 6% 4 4 3 4 4 22%	4685
February	1st to 10th	Night	7% 12% 6% 11% 7% 6% 4 4 5% 5% 33%	2470
	11th to 20th	Night	8% 10% 4 9% 5% 5% 5% 4 5% 7% 38%	2403
	21st to end	Night	13% 11% 3 8% 7% 5% 4 3 5% 6% 34%	1889
March	1st to 10th	Night	10% 7% 3 6% 4 4 4 4 6% 8% 45%	3706
	11th to 20th	Night	9% 8% 3 9% 5% 5% 5% 3 6% 7% 39%	3480
	21st to end	Night	25% 11% 4 11% 5% 3 3 2 3 4 29%	3636
April	1st to 10th	Night	19% 11% 3 5% 4 3 4 4 5% 5% 36%	1900
	11th to 20th	Night	23% 8% 3 6% 4 3 4 3 5% 5% 35%	1875
	21st to end	Night	20% 9% 2 6% 4 3 3 3 5% 6% 36%	1808
May	1st to 10th	Night	18% 7% 2 7% 5% 5% 5% 3 5% 6% 38%	2506
	11th to 20th	Night	14% 5% 1 6% 3 3 3 2 4 7% 51%	2506
	21st to end	Night	15% 6% 2 7% 5% 3 5% 3 5% 7% 42%	2743
June	1st to 10th	Night	12% 6% 2 5% 3 4 4 4 6% 8% 46%	1520
	11th to 20th	Night	12% 5% 2 5% 4 4 5% 4 6% 8% 45%	1520
	21st to end	Night	11% 4 3 5% 4 4 4 4 7% 8% 47%	1520
July	1st to 10th	Night	14% 4 1 4 4 4 4 4 6% 8% 48%	2530
	11th to 20th	Night	5% 3 1 4 4 4 5% 4 5% 8% 58%	2530
	21st to end	Night	7% 3 2 5% 3 4 4 3 5% 8% 56%	2750
August	1st to 10th	Night	13% 5% 2 6% 4 4 4 4 6% 7% 46%	2670
	11th to 20th	Night	14% 5% 1 6% 4 4 4 3 5% 6% 50%	2798
	21st to end	Night	15% 5% 2 6% 4 4 4 3 4 6% 47%	3475
September	1st to 10th	Night	10% 4 2 6% 4 3 4 3 5% 6% 53%	1900
	11th to 20th	Night	12% 5% 2 4 4 4 3 3 5% 7% 52%	1900
	21st to end	Night	14% 4 2 6% 4 3 4 2 5% 7% 49%	2140
October	1st to 10th	Night	15% 5% 2 5% 3 4 3 3 5% 6% 50%	2280
	11th to 20th	Night	16% 9% 3 6% 4 4 4 3 5% 7% 40%	2280
	21st to end	Night	18% 11% 3 6% 4 4 4 3 4 5% 36%	2627
November	1st to 10th	Night	15% 11% 4 6% 3 3 3 3 5% 7% 40%	2483
	11th to 20th	Night	15% 11% 5% 9% 5% 4 4 4 4 6% 32%	2656
	21st to end	Night	15% 12% 4 9% 4 4 3 4 5% 5% 36%	2660
December	1st to 10th	Night	12% 14% 5% 11% 6% 4 4 3 5% 6% 30%	2660
	11th to 20th	Night	13% 16% 4 12% 6% 5% 4 3 4 5% 26%	3279
	21st to end	Night	25% 15% 5% 11% 4 4 3 3 4 4 21%	4884

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	65% 2 11% 17% 4	2528
	11th to 20th	Day	69% 2 7% 16% 7%	2530
	21st to end	Day	65% 2 13% 16% 4	2979
February	1st to 10th	Day	52% 3 13% 20% 11% 1	1710
	11th to 20th	Day	48% 4 12% 26% 9% 1	1673
	21st to end	Day	54% 3 10% 23% 9% 2	1564
March	1st to 10th	Day	42% 1 13% 25% 17% 2	3174
	11th to 20th	Day	45% 2 9% 30% 13% 1	3480
	21st to end	Day	62% 2 8% 21% 7% 1	3995
April	1st to 10th	Day	53% 3 9% 21% 13% 1	2280
	11th to 20th	Day	56% 2 8% 20% 12% 2	2254
	21st to end	Day	57% 3 11% 19% 10% 1	2369
May	1st to 10th	Day	46% 2 8% 29% 14% 1	4440
	11th to 20th	Day	43% 2 10% 30% 14% 1	4403
	21st to end	Day	49% 3 9% 24% 13% 2	4837
June	1st to 10th	Day	38% 3 13% 31% 13% 2	2660
	11th to 20th	Day	43% 4 13% 25% 13% 1	2660
	21st to end	Day	39% 5% 16% 28% 11% 2	2660
July	1st to 10th	Day	40% 5% 17% 27% 10% 1	4371
	11th to 20th	Day	25% 5% 16% 36% 17% 2	4365
	21st to end	Day	35% 5% 14% 27% 18% 1	4662
August	1st to 10th	Day	39% 5% 13% 28% 14% 1	4252
	11th to 20th	Day	37% 4 12% 36% 11%	4080
	21st to end	Day	40% 4 13% 30% 12% 1	4179
September	1st to 10th	Day	36% 4 13% 31% 15%	2280
	11th to 20th	Day	38% 4 16% 33% 8% 1	2280
	21st to end	Day	41% 3 12% 32% 11%	2018
October	1st to 10th	Day	29% 2 9% 39% 21%	3160
	11th to 20th	Day	42% 3 10% 26% 17% 1	3140
	21st to end	Day	45% 2 14% 30% 9%	3221
November	1st to 10th	Day	46% 3 13% 22% 14% 2	1717
	11th to 20th	Day	58% 3 12% 18% 8% 1	1520
	21st to end	Day	50% 3 16% 22% 7% 1	1520
December	1st to 10th	Day	62% 3 13% 17% 5%	1520
	11th to 20th	Day	61% 2 15% 15% 5% 2	1915
	21st to end	Day	74% 2 6% 14% 4	2783
January	1st to 10th	Night	61% 2 10% 21% 6% 1	4428
	11th to 20th	Night	66% 2 10% 15% 7%	4440
	21st to end	Night	67% 2 8% 17% 5% 1	4685
February	1st to 10th	Night	53% 3 10% 22% 10% 2	2470
	11th to 20th	Night	46% 4 12% 28% 9% 1	2404
	21st to end	Night	52% 2 12% 21% 11% 2	1889
March	1st to 10th	Night	39% 2 12% 32% 12% 2	3706
	11th to 20th	Night	47% 1 8% 29% 14% 2	3480
	21st to end	Night	63% 2 6% 20% 8% 1	3636
April	1st to 10th	Night	50% 3 8% 19% 18% 2	1900
	11th to 20th	Night	52% 2 7% 20% 16% 2	1875
	21st to end	Night	49% 2 9% 23% 16% 2	1808
May	1st to 10th	Night	48% 2 11% 18% 19% 1	2530
	11th to 20th	Night	36% 2 6% 33% 20% 3	2507
	21st to end	Night	44% 2 11% 25% 17% 1	2751
June	1st to 10th	Night	37% 5% 10% 30% 17% 1	1520
	11th to 20th	Night	36% 5% 13% 25% 19% 2	1520
	21st to end	Night	34% 4 14% 32% 14% 3	1520
July	1st to 10th	Night	35% 5% 18% 27% 14% 2	2490
	11th to 20th	Night	25% 4 13% 37% 20% 2	2482
	21st to end	Night	27% 5% 15% 30% 20% 3	2662
August	1st to 10th	Night	37% 5% 12% 28% 15% 2	2661
	11th to 20th	Night	35% 5% 14% 29% 15% 2	2825
	21st to end	Night	39% 4 15% 26% 14% 2	3475
September	1st to 10th	Night	32% 3 12% 33% 19% 1	1900
	11th to 20th	Night	33% 2 14% 35% 15%	1900
	21st to end	Night	36% 3 13% 34% 15% 1	2140
October	1st to 10th	Night	27% 1 6% 37% 25% 3	3800
	11th to 20th	Night	35% 3 10% 30% 21% 1	3779
	21st to end	Night	49% 3 10% 24% 14% 1	4326
November	1st to 10th	Night	45% 3 11% 25% 14% 1	2483
	11th to 20th	Night	53% 3 14% 17% 12% 1	2656
	21st to end	Night	50% 3 15% 24% 7% 1	2660
December	1st to 10th	Night	56% 3 14% 21% 5%	2660
	11th to 20th	Night	61% 3 12% 18% 6% 1	3281
	21st to end	Night	69% 2 8% 16% 5%	4884

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	16% 13% 32% 26% 11% 3	270
	11th to 20th	Day	19% 11% 39% 22% 7% 1	270
	21st to end	Day	21% 9% 34% 26% 8% 2	297
February	1st to 10th	Day	16% 14% 43% 19% 7% 2	270
	11th to 20th	Day	16% 19% 37% 20% 8%	270
	21st to end	Day	17% 15% 41% 26% 1	225
March	1st to 10th	Day	19% 14% 38% 19% 9% 1	270
	11th to 20th	Day	20% 11% 37% 20% 10% 2	270
	21st to end	Day	23% 12% 31% 22% 9% 3	401
April	1st to 10th	Day	26% 12% 33% 21% 6% 2	460
	11th to 20th	Day	28% 14% 26% 23% 8% 1	452
	21st to end	Day	27% 14% 24% 23% 9% 2	535
May	1st to 10th	Day	21% 11% 32% 25% 9% 2	653
	11th to 20th	Day	21% 11% 27% 25% 13% 4	675
	21st to end	Day	19% 9% 25% 28% 15% 4	734
June	1st to 10th	Day	14% 8% 25% 32% 17% 4	680
	11th to 20th	Day	16% 7% 34% 27% 13% 3	680
	21st to end	Day	15% 8% 28% 28% 15% 7%	680
July	1st to 10th	Day	10% 4 21% 28% 25% 12%	671
	11th to 20th	Day	10% 5% 24% 30% 22% 9%	668
	21st to end	Day	6% 4 24% 36% 22% 10%	739
August	1st to 10th	Day	11% 5% 22% 30% 24% 8%	676
	11th to 20th	Day	12% 5% 19% 28% 28% 8%	665
	21st to end	Day	14% 6% 22% 28% 23% 6%	539
September	1st to 10th	Day	16% 6% 25% 29% 20% 5%	490
	11th to 20th	Day	12% 6% 27% 32% 20% 4	490
	21st to end	Day	17% 9% 28% 28% 15% 4	399
October	1st to 10th	Day	18% 11% 28% 24% 14% 4	300
	11th to 20th	Day	21% 15% 36% 22% 6% 1	300
	21st to end	Day	26% 13% 35% 18% 5% 2	330
November	1st to 10th	Day	19% 11% 36% 24% 8% 2	285
	11th to 20th	Day	21% 17% 34% 23% 5%	270
	21st to end	Day	22% 13% 41% 17% 7%	270
December	1st to 10th	Day	15% 14% 36% 27% 7% 1	270
	11th to 20th	Day	19% 14% 38% 21% 8%	270
	21st to end	Day	28% 13% 40% 16% 3	297
January	1st to 10th	Night	15% 10% 36% 29% 9% 1	950
	11th to 20th	Night	18% 8% 36% 29% 7% 1	950
	21st to end	Night	20% 9% 32% 30% 8% 1	1045
February	1st to 10th	Night	12% 13% 37% 30% 7% 1	950
	11th to 20th	Night	13% 12% 39% 28% 7% 1	929
	21st to end	Night	19% 11% 34% 29% 6%	633
March	1st to 10th	Night	16% 11% 37% 27% 8% 1	746
	11th to 20th	Night	17% 11% 33% 32% 7% 1	570
	21st to end	Night	23% 8% 29% 28% 10% 2	627
April	1st to 10th	Night	25% 9% 36% 24% 6% 1	570
	11th to 20th	Night	27% 7% 29% 29% 7%	563
	21st to end	Night	23% 8% 31% 27% 10% 1	570
May	1st to 10th	Night	24% 6% 34% 30% 6% 1	570
	11th to 20th	Night	20% 6% 31% 32% 9% 2	561
	21st to end	Night	15% 7% 24% 37% 16% 1	617
June	1st to 10th	Night	13% 6% 28% 41% 12%	570
	11th to 20th	Night	13% 6% 28% 41% 11% 1	570
	21st to end	Night	12% 4 25% 43% 14% 2	570
July	1st to 10th	Night	8% 3 21% 40% 26% 3	555
	11th to 20th	Night	8% 4 23% 38% 24% 3	552
	21st to end	Night	6% 1 20% 46% 23% 3	624
August	1st to 10th	Night	9% 2 16% 47% 25% 1	567
	11th to 20th	Night	13% 3 17% 37% 28% 2	564
	21st to end	Night	15% 2 22% 36% 23% 2	627
September	1st to 10th	Night	11% 5% 22% 41% 18% 4	570
	11th to 20th	Night	13% 4 25% 37% 19% 3	570
	21st to end	Night	15% 7% 28% 32% 16% 2	722
October	1st to 10th	Night	17% 7% 27% 32% 15% 1	760
	11th to 20th	Night	19% 10% 34% 28% 9% 1	760
	21st to end	Night	24% 9% 29% 29% 9%	836
November	1st to 10th	Night	20% 10% 34% 29% 6% 1	764
	11th to 20th	Night	21% 12% 36% 24% 7%	946
	21st to end	Night	21% 13% 36% 23% 7%	950
December	1st to 10th	Night	20% 9% 36% 27% 8% 1	950
	11th to 20th	Night	22% 9% 35% 24% 7% 1	950
	21st to end	Night	28% 10% 31% 25% 6%	1045

Page generated at 2024-11-03 12:18:59. Version ac07

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