Oronoko Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oronoko Observatory clear sky chart from 2005-11-06 to 2024-10-20.

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	13% 10% 4 8% 5% 4 4 4 5% 7% 35%	101060
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 32%	97681
Transparency	Day	47% 7% 12% 21% 12% 1	100851
	Night	52% 7% 11% 18% 11% 1	97562
Seeing	Day	19% 13% 29% 23% 12% 4	15726
	Night	20% 11% 28% 28% 11% 1	25542

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	13% 23% 10% 13% 6% 5% 4 3 3 5% 14%	2527
	11th to 20th	Day	14% 18% 9% 16% 8% 8% 9% 3 3 3 8%	2530
	21st to end	Day	25% 23% 7% 12% 5% 3 4 3 3 4 11%	2783
February	1st to 10th	Day	15% 16% 6% 13% 10% 5% 4 4 5% 4 18%	1807
	11th to 20th	Day	15% 13% 6% 15% 9% 5% 4 2 5% 5% 22%	1848
	21st to end	Day	16% 16% 7% 12% 4 5% 5% 3 4 5% 23%	1570
March	1st to 10th	Day	18% 14% 6% 8% 6% 4 4 3 5% 6% 28%	3120
	11th to 20th	Day	11% 9% 7% 9% 6% 4 4 4 6% 8% 32%	3338
	21st to end	Day	19% 12% 6% 10% 6% 5% 4 3 5% 5% 24%	4029
April	1st to 10th	Day	16% 14% 4 8% 4 4 4 3 5% 6% 32%	2280
	11th to 20th	Day	16% 11% 3 6% 4 3 4 3 5% 7% 38%	2257
	21st to end	Day	19% 9% 3 7% 5% 4 4 3 5% 7% 34%	2470
May	1st to 10th	Day	17% 8% 2 6% 5% 4 5% 4 6% 8% 35%	4082
	11th to 20th	Day	14% 8% 3 6% 4 4 4 3 6% 8% 39%	4081
	21st to end	Day	10% 6% 2 6% 4 4 4 4 5% 9% 46%	4823
June	1st to 10th	Day	10% 5% 3 6% 5% 4 5% 3 6% 7% 46%	2660
	11th to 20th	Day	9% 5% 2 6% 5% 5% 4 4 6% 8% 46%	2660
	21st to end	Day	11% 7% 2 5% 4 5% 4 4 6% 9% 43%	2660
July	1st to 10th	Day	11% 7% 3 7% 5% 5% 6% 4 6% 8% 37%	4440
	11th to 20th	Day	7% 4 1 5% 4 4 4 4 7% 11% 49%	4440
	21st to end	Day	7% 6% 2 7% 5% 5% 5% 5% 6% 8% 44%	4813
August	1st to 10th	Day	9% 6% 2 6% 4 4 4 4 6% 8% 48%	4149
	11th to 20th	Day	9% 6% 2 6% 4 4 4 4 6% 8% 46%	3957
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 10% 47%	4180
September	1st to 10th	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 46%	2274
	11th to 20th	Day	12% 5% 1 5% 3 5% 5% 4 6% 9% 46%	2090
	21st to end	Day	14% 7% 2 6% 4 3 4 4 6% 8% 40%	2090
October	1st to 10th	Day	14% 7% 3 6% 5% 3 4 3 5% 6% 43%	2090
	11th to 20th	Day	20% 9% 2 7% 4 4 5% 4 5% 7% 32%	1860
	21st to end	Day	23% 13% 3 8% 5% 4 4 3 5% 6% 24%	1782
November	1st to 10th	Day	13% 12% 3 7% 4 4 4 4 6% 6% 36%	1672
	11th to 20th	Day	16% 19% 5% 9% 6% 4 3 4 5% 4 25%	1710
	21st to end	Day	20% 19% 5% 10% 5% 4 4 3 3 5% 23%	1710
December	1st to 10th	Day	15% 21% 9% 11% 6% 4 4 2 3 5% 20%	1577
	11th to 20th	Day	13% 22% 9% 13% 6% 5% 3 4 5% 5% 17%	1918
	21st to end	Day	21% 24% 7% 15% 6% 4 3 3 3 4 10%	2783
January	1st to 10th	Night	17% 22% 9% 14% 7% 5% 4 3 4 4 11%	4428
	11th to 20th	Night	15% 21% 9% 17% 7% 5% 7% 3 3 3 10%	4440
	21st to end	Night	24% 21% 10% 12% 6% 4 3 2 4 4 10%	4884
February	1st to 10th	Night	17% 16% 5% 11% 9% 5% 4 3 4 4 22%	2370
	11th to 20th	Night	13% 15% 6% 14% 6% 5% 4 3 5% 5% 24%	2218
	21st to end	Night	19% 15% 5% 12% 6% 4 3 3 4 5% 25%	1884
March	1st to 10th	Night	16% 12% 5% 9% 4 5% 4 3 4 5% 32%	3733
	11th to 20th	Night	10% 8% 5% 7% 5% 5% 5% 4 5% 6% 40%	3621
	21st to end	Night	19% 12% 5% 10% 4 3 4 3 4 6% 27%	3631
April	1st to 10th	Night	15% 11% 3 7% 4 5% 5% 4 5% 7% 34%	1900
	11th to 20th	Night	19% 11% 2 6% 4 4 3 4 5% 5% 36%	1870
	21st to end	Night	18% 8% 3 6% 5% 4 4 4 6% 5% 36%	1710
May	1st to 10th	Night	15% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	2813
	11th to 20th	Night	18% 8% 3 6% 4 4 3 3 5% 8% 39%	2798
	21st to end	Night	15% 7% 2 6% 4 4 4 3 5% 7% 42%	2743
June	1st to 10th	Night	8% 6% 2 5% 3 3 4 4 6% 10% 48%	1520
	11th to 20th	Night	9% 6% 2 5% 5% 5% 5% 4 6% 9% 44%	1520
	21st to end	Night	9% 5% 2 7% 5% 4 5% 4 8% 10% 40%	1520
July	1st to 10th	Night	9% 4 2 7% 5% 5% 5% 4 7% 9% 42%	2530
	11th to 20th	Night	7% 4 2 4 4 3 4 3 6% 8% 55%	2530
	21st to end	Night	6% 6% 2 6% 4 5% 5% 5% 7% 9% 45%	2750
August	1st to 10th	Night	8% 6% 3 6% 4 4 5% 4 6% 9% 44%	2781
	11th to 20th	Night	9% 4 2 5% 4 4 6% 4 6% 8% 49%	2869
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 5% 7% 49%	3476
September	1st to 10th	Night	10% 7% 2 6% 4 4 4 3 5% 7% 49%	1900
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 4 9% 54%	2076
	21st to end	Night	13% 6% 3 7% 4 4 4 3 5% 8% 42%	2090
October	1st to 10th	Night	15% 7% 2 5% 4 3 4 3 5% 6% 46%	2090
	11th to 20th	Night	19% 10% 3 8% 4 4 4 3 4 6% 36%	2303
	21st to end	Night	25% 10% 3 7% 5% 4 4 3 4 5% 31%	2574
November	1st to 10th	Night	14% 13% 3 8% 4 3 4 3 5% 5% 38%	2406
	11th to 20th	Night	15% 18% 4 11% 5% 4 4 3 5% 5% 26%	2470
	21st to end	Night	19% 18% 5% 8% 5% 4 4 2 4 5% 25%	2470
December	1st to 10th	Night	17% 23% 6% 11% 6% 4 4 3 4 5% 17%	2600
	11th to 20th	Night	15% 19% 8% 14% 7% 6% 5% 3 4 4 16%	3279
	21st to end	Night	25% 23% 6% 11% 5% 4 4 3 4 4 11%	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	72% 7% 10% 8% 2	2528
	11th to 20th	Day	80% 8% 7% 4 1	2530
	21st to end	Day	78% 5% 7% 8% 2	2783
February	1st to 10th	Day	68% 7% 9% 11% 5% 1	1807
	11th to 20th	Day	63% 5% 11% 13% 7%	1858
	21st to end	Day	62% 6% 12% 13% 6% 1	1570
March	1st to 10th	Day	55% 7% 11% 19% 8%	3120
	11th to 20th	Day	47% 7% 14% 25% 6% 1	3338
	21st to end	Day	60% 8% 10% 17% 4	4029
April	1st to 10th	Day	51% 6% 11% 20% 11%	2280
	11th to 20th	Day	45% 7% 10% 22% 13% 3	2257
	21st to end	Day	47% 7% 12% 19% 13% 2	2470
May	1st to 10th	Day	43% 9% 12% 25% 10% 1	4120
	11th to 20th	Day	39% 8% 14% 27% 11% 1	4085
	21st to end	Day	33% 8% 11% 23% 23% 1	4836
June	1st to 10th	Day	36% 7% 11% 25% 19% 2	2660
	11th to 20th	Day	34% 7% 13% 24% 19% 3	2660
	21st to end	Day	37% 9% 14% 22% 16% 3	2660
July	1st to 10th	Day	44% 5% 13% 20% 16% 3	4371
	11th to 20th	Day	28% 6% 17% 33% 16% 1	4365
	21st to end	Day	35% 7% 16% 19% 20% 3	4662
August	1st to 10th	Day	34% 6% 14% 30% 15% 1	4134
	11th to 20th	Day	33% 7% 13% 31% 15% 1	3996
	21st to end	Day	32% 6% 13% 26% 20% 3	4179
September	1st to 10th	Day	34% 7% 16% 23% 16% 3	2274
	11th to 20th	Day	33% 6% 12% 29% 18% 2	2090
	21st to end	Day	40% 7% 12% 23% 16% 1	2090
October	1st to 10th	Day	42% 6% 10% 25% 15% 2	2090
	11th to 20th	Day	49% 7% 12% 20% 11%	1860
	21st to end	Day	60% 6% 11% 15% 7% 1	1782
November	1st to 10th	Day	47% 8% 11% 20% 14% 1	1672
	11th to 20th	Day	61% 7% 9% 16% 6% 1	1710
	21st to end	Day	65% 5% 11% 15% 5%	1710
December	1st to 10th	Day	69% 4 11% 12% 4	1577
	11th to 20th	Day	69% 7% 12% 10% 2	1915
	21st to end	Day	79% 5% 7% 7% 2	2783
January	1st to 10th	Night	73% 8% 9% 8% 2	4428
	11th to 20th	Night	80% 6% 8% 4 2	4440
	21st to end	Night	78% 5% 10% 6% 1	4884
February	1st to 10th	Night	66% 6% 10% 12% 6% 1	2370
	11th to 20th	Night	62% 6% 10% 15% 7%	2219
	21st to end	Night	63% 5% 9% 14% 6% 2	1884
March	1st to 10th	Night	51% 8% 11% 22% 7%	3733
	11th to 20th	Night	42% 8% 13% 24% 13% 2	3621
	21st to end	Night	57% 7% 12% 17% 6% 1	3631
April	1st to 10th	Night	48% 7% 12% 20% 12% 1	1900
	11th to 20th	Night	48% 6% 8% 19% 16% 3	1870
	21st to end	Night	48% 7% 10% 18% 14% 2	1710
May	1st to 10th	Night	45% 8% 12% 22% 11% 1	2840
	11th to 20th	Night	41% 7% 13% 23% 15% 1	2799
	21st to end	Night	39% 8% 10% 18% 22% 2	2751
June	1st to 10th	Night	32% 6% 13% 29% 17% 3	1520
	11th to 20th	Night	35% 7% 14% 23% 19% 2	1520
	21st to end	Night	36% 9% 17% 22% 14% 2	1520
July	1st to 10th	Night	38% 6% 14% 24% 13% 6%	2490
	11th to 20th	Night	27% 6% 14% 24% 28% 2	2482
	21st to end	Night	34% 8% 16% 17% 23% 3	2662
August	1st to 10th	Night	35% 6% 13% 29% 16% 1	2772
	11th to 20th	Night	32% 7% 11% 29% 20% 1	2896
	21st to end	Night	34% 5% 10% 29% 20% 3	3476
September	1st to 10th	Night	35% 7% 12% 23% 19% 5%	1900
	11th to 20th	Night	29% 6% 8% 30% 25% 2	2076
	21st to end	Night	40% 6% 11% 25% 17% 2	2090
October	1st to 10th	Night	38% 7% 9% 26% 19% 1	2090
	11th to 20th	Night	50% 5% 10% 20% 13% 1	2303
	21st to end	Night	57% 6% 10% 19% 7% 1	2574
November	1st to 10th	Night	49% 6% 9% 20% 14% 1	2406
	11th to 20th	Night	60% 5% 11% 15% 7% 1	2470
	21st to end	Night	62% 6% 11% 16% 5%	2470
December	1st to 10th	Night	71% 5% 9% 10% 4	2600
	11th to 20th	Night	71% 7% 10% 9% 2	3281
	21st to end	Night	76% 7% 10% 6% 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	23% 20% 35% 17% 4 1	270
	11th to 20th	Day	24% 19% 37% 14% 4 1	270
	21st to end	Day	27% 20% 33% 17% 3	297
February	1st to 10th	Day	29% 20% 31% 15% 4	270
	11th to 20th	Day	27% 24% 33% 16%	270
	21st to end	Day	26% 30% 33% 8% 2	225
March	1st to 10th	Day	26% 24% 34% 13% 3	270
	11th to 20th	Day	28% 16% 33% 17% 5% 1	370
	21st to end	Day	32% 17% 28% 16% 6% 1	506
April	1st to 10th	Day	25% 21% 31% 19% 4 1	460
	11th to 20th	Day	24% 23% 27% 17% 7% 2	452
	21st to end	Day	27% 15% 31% 18% 7% 2	460
May	1st to 10th	Day	27% 15% 30% 18% 8% 2	463
	11th to 20th	Day	22% 12% 28% 25% 9% 4	487
	21st to end	Day	13% 11% 32% 26% 14% 4	733
June	1st to 10th	Day	12% 11% 31% 29% 13% 4	680
	11th to 20th	Day	13% 10% 30% 30% 14% 4	680
	21st to end	Day	14% 10% 32% 27% 13% 4	680
July	1st to 10th	Day	9% 5% 27% 26% 24% 9%	671
	11th to 20th	Day	10% 7% 30% 27% 19% 6%	668
	21st to end	Day	9% 4 25% 38% 18% 6%	739
August	1st to 10th	Day	10% 3 20% 31% 24% 12%	519
	11th to 20th	Day	11% 5% 25% 26% 26% 7%	479
	21st to end	Day	10% 4 22% 33% 23% 8%	539
September	1st to 10th	Day	13% 6% 23% 31% 20% 6%	490
	11th to 20th	Day	10% 6% 19% 29% 26% 11%	490
	21st to end	Day	19% 12% 20% 25% 16% 7%	490
October	1st to 10th	Day	18% 10% 28% 24% 17% 3	490
	11th to 20th	Day	26% 18% 28% 22% 5% 1	364
	21st to end	Day	35% 17% 31% 13% 3	297
November	1st to 10th	Day	19% 18% 36% 19% 7% 2	270
	11th to 20th	Day	26% 26% 28% 16% 4	270
	21st to end	Day	33% 17% 37% 12% 1	270
December	1st to 10th	Day	24% 30% 28% 11% 6% 1	270
	11th to 20th	Day	21% 30% 33% 13% 3 1	270
	21st to end	Day	25% 30% 33% 11% 1	297
January	1st to 10th	Night	24% 18% 34% 19% 5%	950
	11th to 20th	Night	26% 16% 34% 20% 3	950
	21st to end	Night	22% 16% 35% 22% 4	1045
February	1st to 10th	Night	27% 12% 36% 22% 3	797
	11th to 20th	Night	23% 16% 34% 23% 4	743
	21st to end	Night	27% 17% 35% 17% 3	628
March	1st to 10th	Night	22% 16% 32% 23% 7% 1	760
	11th to 20th	Night	18% 13% 37% 25% 6%	760
	21st to end	Night	24% 13% 28% 28% 6%	727
April	1st to 10th	Night	21% 14% 34% 24% 6% 1	570
	11th to 20th	Night	24% 12% 31% 25% 7% 1	563
	21st to end	Night	22% 11% 33% 25% 8% 1	570
May	1st to 10th	Night	20% 8% 31% 31% 9% 1	570
	11th to 20th	Night	20% 6% 26% 34% 13% 1	561
	21st to end	Night	14% 4 24% 39% 18% 1	617
June	1st to 10th	Night	11% 6% 24% 42% 17% 1	570
	11th to 20th	Night	12% 4 29% 39% 14% 1	570
	21st to end	Night	11% 5% 24% 39% 21% 1	570
July	1st to 10th	Night	8% 3 17% 40% 28% 3	555
	11th to 20th	Night	9% 3 20% 37% 27% 4	552
	21st to end	Night	8% 2 15% 44% 29% 2	624
August	1st to 10th	Night	8% 2 13% 46% 27% 3	567
	11th to 20th	Night	9% 3 16% 39% 29% 4	564
	21st to end	Night	9% 4 16% 39% 29% 3	627
September	1st to 10th	Night	13% 4 17% 39% 23% 4	570
	11th to 20th	Night	12% 5% 15% 37% 27% 4	746
	21st to end	Night	16% 8% 24% 31% 19% 3	760
October	1st to 10th	Night	20% 6% 26% 29% 19% 1	760
	11th to 20th	Night	26% 16% 25% 26% 7% 1	759
	21st to end	Night	32% 14% 28% 20% 5%	792
November	1st to 10th	Night	22% 14% 31% 22% 10% 1	740
	11th to 20th	Night	26% 19% 31% 21% 4 1	760
	21st to end	Night	29% 14% 32% 21% 4	760
December	1st to 10th	Night	27% 18% 35% 17% 4	890
	11th to 20th	Night	24% 16% 38% 18% 3	950
	21st to end	Night	31% 17% 34% 16% 1	1045

Page generated at 2024-10-17 13:09:40. Version ac07

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