Onekama-DS-Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Onekama-DS-Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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% 11% 4 9% 5% 4 4 3 5% 6% 34%	101574
	Night	15% 14% 5% 11% 6% 4 4 3 4 5% 29%	97975
Transparency	Day	49% 6% 11% 21% 11% 1	105106
	Night	56% 5% 11% 18% 9% 1	102584
Seeing	Day	20% 14% 31% 22% 10% 3	16000
	Night	22% 12% 28% 27% 11% 1	25876

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	12% 28% 14% 19% 8% 4 3 1 2 2 6%	2527
	11th to 20th	Day	13% 20% 9% 23% 12% 9% 4 2 2 2 4	2530
	21st to end	Day	17% 24% 12% 15% 8% 5% 4 3 3 3 7%	2783
February	1st to 10th	Day	9% 17% 7% 18% 15% 6% 4 3 4 3 14%	1645
	11th to 20th	Day	12% 16% 8% 16% 12% 6% 5% 3 4 4 15%	1848
	21st to end	Day	12% 18% 6% 15% 9% 5% 5% 3 3 5% 19%	1570
March	1st to 10th	Day	12% 14% 5% 9% 6% 4 4 4 5% 6% 31%	3120
	11th to 20th	Day	11% 11% 8% 14% 5% 4 3 3 5% 6% 30%	3338
	21st to end	Day	19% 12% 7% 13% 5% 3 4 3 4 5% 24%	4032
April	1st to 10th	Day	18% 14% 4 8% 4 4 4 4 4 6% 30%	2280
	11th to 20th	Day	21% 12% 3 6% 3 4 4 3 5% 6% 34%	2306
	21st to end	Day	16% 11% 4 6% 5% 5% 4 3 6% 7% 34%	2470
May	1st to 10th	Day	14% 8% 2 7% 4 3 4 4 5% 7% 42%	4082
	11th to 20th	Day	11% 7% 2 5% 4 4 3 3 5% 7% 48%	4287
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 8% 44%	4824
June	1st to 10th	Day	12% 5% 1 5% 4 4 4 5% 5% 7% 46%	2660
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 9% 44%	2660
	21st to end	Day	13% 5% 2 6% 4 3 4 4 7% 9% 43%	2660
July	1st to 10th	Day	16% 6% 2 6% 3 4 4 3 6% 9% 40%	4440
	11th to 20th	Day	7% 3 1 3 3 3 4 4 6% 9% 57%	4440
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 9% 50%	4813
August	1st to 10th	Day	9% 6% 2 6% 4 5% 5% 4 7% 8% 43%	4298
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 7% 51%	4044
	21st to end	Day	12% 6% 2 6% 4 4 4 3 6% 7% 45%	4226
September	1st to 10th	Day	14% 5% 1 6% 5% 5% 4 4 5% 6% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 3 3 4 4 6% 9% 46%	2095
	21st to end	Day	15% 6% 3 7% 4 3 5% 4 7% 8% 39%	2090
October	1st to 10th	Day	17% 7% 3 7% 4 4 4 3 5% 7% 39%	2090
	11th to 20th	Day	23% 15% 4 9% 5% 5% 4 4 5% 6% 21%	1797
	21st to end	Day	25% 14% 4 10% 6% 4 3 4 5% 5% 21%	1881
November	1st to 10th	Day	18% 18% 4 6% 4 4 4 2 5% 7% 28%	1762
	11th to 20th	Day	16% 24% 6% 12% 5% 4 5% 3 4 6% 15%	1800
	21st to end	Day	19% 25% 8% 11% 5% 4 4 3 3 4 15%	1675
December	1st to 10th	Day	14% 27% 12% 18% 5% 4 4 3 2 3 9%	1520
	11th to 20th	Day	15% 24% 9% 18% 7% 5% 3 3 4 4 8%	1918
	21st to end	Day	21% 22% 10% 14% 7% 5% 3 3 3 4 8%	2783
January	1st to 10th	Night	14% 27% 9% 19% 8% 4 3 2 2 3 10%	4428
	11th to 20th	Night	11% 18% 9% 22% 13% 10% 3 2 2 2 7%	4440
	21st to end	Night	15% 24% 11% 19% 8% 6% 4 2 2 3 6%	4884
February	1st to 10th	Night	10% 19% 7% 17% 13% 6% 4 2 4 4 14%	2529
	11th to 20th	Night	12% 16% 6% 18% 10% 6% 5% 3 4 4 16%	2218
	21st to end	Night	15% 16% 6% 15% 7% 5% 4 3 5% 4 20%	1884
March	1st to 10th	Night	16% 11% 4 8% 5% 3 3 3 5% 6% 37%	3733
	11th to 20th	Night	8% 12% 4 11% 5% 5% 4 4 5% 7% 36%	3622
	21st to end	Night	16% 13% 4 13% 5% 4 4 3 4 6% 27%	3626
April	1st to 10th	Night	18% 11% 4 9% 5% 4 4 3 5% 6% 31%	1900
	11th to 20th	Night	21% 9% 3 7% 5% 4 4 3 4 6% 35%	1821
	21st to end	Night	17% 9% 4 7% 5% 4 4 4 4 6% 36%	1710
May	1st to 10th	Night	15% 7% 3 7% 4 4 5% 3 6% 6% 40%	2813
	11th to 20th	Night	13% 7% 2 7% 4 4 4 4 7% 7% 40%	2613
	21st to end	Night	19% 6% 2 6% 3 4 4 3 5% 7% 43%	2743
June	1st to 10th	Night	13% 7% 2 7% 4 4 4 4 6% 8% 41%	1520
	11th to 20th	Night	10% 7% 2 6% 5% 4 5% 5% 7% 8% 42%	1520
	21st to end	Night	12% 6% 2 6% 4 4 4 4 5% 8% 45%	1520
July	1st to 10th	Night	14% 8% 2 6% 4 5% 4 4 6% 7% 41%	2530
	11th to 20th	Night	6% 3 1 4 3 3 5% 4 5% 7% 57%	2530
	21st to end	Night	7% 6% 2 6% 4 5% 4 4 6% 8% 48%	2750
August	1st to 10th	Night	11% 6% 2 7% 4 5% 5% 3 6% 8% 43%	2635
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 7% 51%	2785
	21st to end	Night	9% 6% 2 7% 4 5% 4 4 5% 6% 48%	3426
September	1st to 10th	Night	11% 6% 2 5% 4 4 3 3 6% 6% 49%	1900
	11th to 20th	Night	11% 6% 2 5% 3 4 4 4 6% 7% 49%	2066
	21st to end	Night	15% 7% 2 7% 5% 5% 4 5% 5% 7% 39%	2090
October	1st to 10th	Night	18% 7% 3 6% 4 3 3 2 5% 6% 42%	2090
	11th to 20th	Night	24% 13% 4 7% 4 4 3 3 4 6% 27%	2378
	21st to end	Night	26% 14% 4 9% 4 4 4 3 4 5% 24%	2717
November	1st to 10th	Night	16% 17% 4 9% 5% 3 3 3 5% 6% 29%	2536
	11th to 20th	Night	16% 24% 7% 11% 5% 4 5% 3 3 4 19%	2600
	21st to end	Night	18% 23% 8% 12% 4 3 4 3 4 5% 16%	2595
December	1st to 10th	Night	15% 27% 11% 15% 6% 3 3 2 3 3 11%	2660
	11th to 20th	Night	15% 24% 9% 17% 7% 4 3 3 3 4 11%	3279
	21st to end	Night	23% 24% 9% 12% 6% 4 3 2 3 4 10%	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	88% 3 4 3 1	2528
	11th to 20th	Day	91% 3 3 3 1	2530
	21st to end	Day	84% 5% 7% 3 1	2783
February	1st to 10th	Day	76% 5% 7% 11% 1	1645
	11th to 20th	Day	74% 5% 8% 9% 4	1858
	21st to end	Day	68% 5% 9% 12% 4 1	1570
March	1st to 10th	Day	53% 5% 12% 20% 9%	3120
	11th to 20th	Day	53% 6% 14% 18% 8% 1	3338
	21st to end	Day	62% 6% 9% 17% 6% 1	4032
April	1st to 10th	Day	54% 6% 10% 19% 11%	2280
	11th to 20th	Day	51% 5% 8% 20% 15% 2	2306
	21st to end	Day	48% 6% 11% 18% 14% 2	2470
May	1st to 10th	Day	41% 5% 10% 25% 17% 2	4120
	11th to 20th	Day	36% 5% 10% 27% 19% 2	4291
	21st to end	Day	36% 7% 12% 23% 20% 2	4837
June	1st to 10th	Day	35% 7% 12% 28% 16% 2	2660
	11th to 20th	Day	35% 6% 14% 26% 18% 1	2660
	21st to end	Day	35% 7% 16% 27% 15% 1	2660
July	1st to 10th	Day	41% 6% 14% 25% 13% 2	4371
	11th to 20th	Day	24% 6% 16% 36% 17% 2	4365
	21st to end	Day	30% 6% 14% 28% 19% 2	4662
August	1st to 10th	Day	36% 6% 14% 30% 13% 1	4283
	11th to 20th	Day	34% 5% 14% 30% 16% 1	4083
	21st to end	Day	36% 7% 15% 29% 12% 1	4225
September	1st to 10th	Day	39% 6% 12% 28% 13% 1	2280
	11th to 20th	Day	34% 8% 14% 30% 13% 1	2095
	21st to end	Day	42% 7% 15% 27% 10%	2090
October	1st to 10th	Day	31% 4 9% 37% 19% 1	3480
	11th to 20th	Day	53% 6% 11% 20% 10%	2948
	21st to end	Day	61% 5% 14% 15% 5%	3081
November	1st to 10th	Day	57% 6% 9% 20% 8%	1762
	11th to 20th	Day	70% 6% 11% 10% 4	1800
	21st to end	Day	74% 5% 11% 8% 3	1675
December	1st to 10th	Day	83% 4 5% 7% 2	1520
	11th to 20th	Day	80% 5% 9% 5% 1	1915
	21st to end	Day	80% 6% 7% 5% 1	2783
January	1st to 10th	Night	82% 4 6% 7% 1	4428
	11th to 20th	Night	87% 3 5% 4 1	4440
	21st to end	Night	85% 5% 7% 3 1	4884
February	1st to 10th	Night	75% 5% 6% 10% 4	2529
	11th to 20th	Night	72% 4 8% 12% 4	2219
	21st to end	Night	68% 5% 10% 13% 4	1884
March	1st to 10th	Night	48% 5% 16% 22% 8%	3733
	11th to 20th	Night	47% 6% 13% 23% 9% 1	3622
	21st to end	Night	59% 5% 9% 19% 6% 1	3626
April	1st to 10th	Night	54% 6% 9% 20% 11% 1	1900
	11th to 20th	Night	51% 5% 9% 20% 13% 3	1821
	21st to end	Night	49% 4 10% 20% 13% 3	1710
May	1st to 10th	Night	43% 5% 13% 18% 16% 3	2840
	11th to 20th	Night	40% 7% 11% 25% 16% 2	2614
	21st to end	Night	41% 7% 12% 20% 16% 5%	2751
June	1st to 10th	Night	39% 7% 11% 26% 15% 2	1520
	11th to 20th	Night	36% 8% 11% 24% 19% 2	1520
	21st to end	Night	37% 7% 13% 26% 15% 2	1520
July	1st to 10th	Night	42% 7% 11% 22% 12% 6%	2490
	11th to 20th	Night	25% 6% 15% 33% 19% 2	2482
	21st to end	Night	33% 7% 12% 23% 22% 2	2662
August	1st to 10th	Night	38% 7% 14% 26% 13% 2	2626
	11th to 20th	Night	33% 5% 13% 31% 18%	2812
	21st to end	Night	35% 6% 13% 23% 22% 1	3426
September	1st to 10th	Night	34% 6% 12% 25% 21% 1	1900
	11th to 20th	Night	33% 8% 13% 31% 15% 1	2066
	21st to end	Night	44% 6% 13% 25% 11% 1	2090
October	1st to 10th	Night	38% 4 9% 35% 13%	3480
	11th to 20th	Night	50% 5% 9% 25% 11%	3966
	21st to end	Night	53% 4 14% 22% 7%	4467
November	1st to 10th	Night	56% 7% 10% 18% 8% 1	2536
	11th to 20th	Night	70% 4 10% 10% 5% 1	2600
	21st to end	Night	71% 6% 12% 9% 2	2595
December	1st to 10th	Night	80% 5% 7% 7% 2	2660
	11th to 20th	Night	79% 5% 9% 5% 2	3281
	21st to end	Night	79% 5% 11% 4 1	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	22% 21% 34% 15% 6% 1	270
	11th to 20th	Day	29% 17% 37% 14% 2	270
	21st to end	Day	25% 20% 33% 19% 2 1	297
February	1st to 10th	Day	21% 30% 32% 11% 4 1	270
	11th to 20th	Day	24% 27% 36% 12% 1	270
	21st to end	Day	25% 32% 37% 5% 1	225
March	1st to 10th	Day	24% 28% 35% 12% 1	270
	11th to 20th	Day	26% 16% 30% 19% 8%	370
	21st to end	Day	30% 17% 29% 17% 6% 1	506
April	1st to 10th	Day	27% 18% 34% 17% 4 1	460
	11th to 20th	Day	29% 20% 28% 14% 6% 3	452
	21st to end	Day	25% 17% 27% 21% 8% 1	460
May	1st to 10th	Day	21% 19% 36% 17% 7% 2	463
	11th to 20th	Day	17% 11% 38% 25% 7% 3	602
	21st to end	Day	14% 11% 33% 27% 12% 3	734
June	1st to 10th	Day	15% 12% 34% 26% 10% 3	680
	11th to 20th	Day	16% 10% 36% 27% 9% 3	680
	21st to end	Day	17% 9% 32% 26% 13% 3	680
July	1st to 10th	Day	9% 7% 31% 32% 15% 5%	671
	11th to 20th	Day	10% 9% 28% 34% 14% 5%	668
	21st to end	Day	10% 5% 33% 33% 15% 5%	739
August	1st to 10th	Day	10% 7% 26% 30% 19% 7%	603
	11th to 20th	Day	13% 6% 22% 30% 20% 9%	479
	21st to end	Day	16% 8% 25% 29% 18% 4	539
September	1st to 10th	Day	18% 9% 26% 26% 15% 6%	490
	11th to 20th	Day	11% 7% 26% 32% 18% 6%	490
	21st to end	Day	18% 12% 24% 27% 13% 5%	490
October	1st to 10th	Day	20% 17% 25% 22% 13% 3	490
	11th to 20th	Day	32% 15% 33% 17% 3	333
	21st to end	Day	37% 17% 31% 12% 4	330
November	1st to 10th	Day	33% 17% 30% 15% 5%	300
	11th to 20th	Day	28% 23% 35% 11% 3	300
	21st to end	Day	31% 24% 30% 12% 2	282
December	1st to 10th	Day	32% 20% 31% 13% 3 1	270
	11th to 20th	Day	31% 24% 31% 11% 3	270
	21st to end	Day	36% 23% 28% 10% 3	297
January	1st to 10th	Night	25% 19% 32% 18% 5% 1	950
	11th to 20th	Night	25% 17% 32% 20% 5%	950
	21st to end	Night	22% 13% 35% 23% 6%	1045
February	1st to 10th	Night	20% 16% 35% 24% 5%	876
	11th to 20th	Night	21% 19% 32% 22% 5%	743
	21st to end	Night	26% 17% 33% 20% 3	628
March	1st to 10th	Night	19% 14% 34% 24% 8% 1	760
	11th to 20th	Night	17% 15% 35% 26% 7%	760
	21st to end	Night	22% 12% 30% 28% 7% 1	722
April	1st to 10th	Night	25% 12% 34% 24% 6% 1	570
	11th to 20th	Night	26% 10% 31% 25% 7% 1	563
	21st to end	Night	21% 11% 31% 28% 9% 1	570
May	1st to 10th	Night	20% 8% 32% 31% 9% 1	570
	11th to 20th	Night	18% 7% 32% 29% 13% 1	561
	21st to end	Night	15% 6% 25% 35% 18% 1	617
June	1st to 10th	Night	15% 5% 28% 37% 14% 1	570
	11th to 20th	Night	12% 7% 26% 36% 16% 2	570
	21st to end	Night	14% 4 23% 40% 19% 1	570
July	1st to 10th	Night	12% 2 19% 42% 23% 2	555
	11th to 20th	Night	8% 4 22% 39% 25% 2	552
	21st to end	Night	8% 5% 21% 39% 25% 3	624
August	1st to 10th	Night	11% 2 16% 47% 22% 2	567
	11th to 20th	Night	11% 4 16% 36% 28% 5%	564
	21st to end	Night	13% 4 20% 40% 20% 2	627
September	1st to 10th	Night	13% 6% 21% 33% 23% 4	570
	11th to 20th	Night	13% 7% 20% 34% 22% 3	736
	21st to end	Night	18% 9% 19% 31% 19% 3	760
October	1st to 10th	Night	22% 10% 23% 30% 14% 1	760
	11th to 20th	Night	32% 12% 23% 26% 6% 1	760
	21st to end	Night	35% 12% 25% 22% 6% 1	836
November	1st to 10th	Night	27% 14% 30% 23% 6% 1	780
	11th to 20th	Night	30% 18% 30% 17% 4	800
	21st to end	Night	31% 16% 28% 21% 4	845
December	1st to 10th	Night	30% 20% 30% 17% 3	950
	11th to 20th	Night	30% 19% 31% 15% 4 1	950
	21st to end	Night	31% 16% 33% 17% 2	1045

Page generated at 2024-11-22 08:02:27. Version ac07

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