Yanna Research Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yanna Research Station clear sky chart from 2005-11-06 to 2024-11-03.

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	13% 9% 3 7% 5% 4 4 4 5% 7% 38%	101446
	Night	14% 9% 3 7% 4 4 4 3 5% 6% 39%	97621
Transparency	Day	46% 4 12% 24% 13% 1	101234
	Night	46% 4 11% 23% 14% 2	97504
Seeing	Day	17% 10% 28% 25% 14% 5%	15884
	Night	17% 9% 30% 30% 12% 1	25722

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% 13% 10% 13% 4 5% 4 3 4 4 27%	2527
	11th to 20th	Day	11% 12% 5% 13% 5% 5% 5% 8% 7% 8% 20%	2530
	21st to end	Day	17% 18% 11% 11% 5% 3 3 2 4 5% 21%	2941
February	1st to 10th	Day	12% 13% 5% 10% 4 5% 5% 4 5% 6% 32%	1710
	11th to 20th	Day	13% 11% 4 8% 5% 4 5% 3 5% 6% 36%	1787
	21st to end	Day	12% 14% 4 11% 6% 4 3 3 5% 6% 32%	1570
March	1st to 10th	Day	14% 8% 3 6% 4 4 3 3 5% 7% 44%	3120
	11th to 20th	Day	11% 7% 3 8% 4 4 5% 4 6% 7% 43%	3370
	21st to end	Day	22% 13% 3 9% 5% 4 4 3 5% 5% 27%	4119
April	1st to 10th	Day	18% 13% 3 7% 5% 4 4 3 5% 6% 31%	2280
	11th to 20th	Day	17% 11% 3 7% 5% 3 4 3 5% 7% 34%	2254
	21st to end	Day	19% 10% 3 8% 5% 4 4 3 4 6% 34%	2334
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 4 4 6% 7% 37%	4207
	11th to 20th	Day	14% 6% 2 6% 5% 4 4 3 5% 6% 44%	4399
	21st to end	Day	13% 7% 3 6% 4 5% 5% 4 6% 8% 39%	4824
June	1st to 10th	Day	11% 4 2 6% 4 5% 5% 4 7% 8% 43%	2660
	11th to 20th	Day	12% 5% 2 6% 4 4 4 5% 7% 9% 42%	2660
	21st to end	Day	12% 7% 2 6% 5% 5% 5% 5% 6% 9% 38%	2660
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 10% 34%	4440
	11th to 20th	Day	5% 4 2 4 4 4 6% 4 6% 9% 52%	4440
	21st to end	Day	10% 6% 2 7% 4 5% 5% 4 6% 9% 42%	4813
August	1st to 10th	Day	10% 5% 2 7% 5% 5% 5% 4 7% 9% 41%	4337
	11th to 20th	Day	12% 5% 2 5% 4 5% 4 3 5% 7% 48%	3802
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 9% 46%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 6% 7% 46%	2280
	11th to 20th	Day	12% 4 2 5% 3 3 3 3 5% 8% 51%	2218
	21st to end	Day	12% 6% 3 7% 4 4 4 3 5% 7% 45%	2090
October	1st to 10th	Day	12% 6% 3 7% 3 3 3 3 4 7% 48%	1938
	11th to 20th	Day	19% 9% 3 7% 5% 4 3 3 4 6% 37%	1900
	21st to end	Day	19% 10% 2 7% 4 3 3 3 5% 5% 39%	1919
November	1st to 10th	Day	11% 8% 3 6% 4 3 4 3 4 7% 45%	1690
	11th to 20th	Day	14% 12% 4 9% 4 5% 4 3 6% 7% 33%	1706
	21st to end	Day	15% 12% 4 8% 5% 4 3 2 4 6% 37%	1520
December	1st to 10th	Day	14% 15% 5% 8% 6% 4 5% 3 5% 6% 31%	1520
	11th to 20th	Day	13% 14% 5% 10% 5% 4 4 3 5% 7% 29%	1918
	21st to end	Day	20% 21% 9% 11% 5% 4 3 4 4 4 15%	2783
January	1st to 10th	Night	12% 13% 8% 11% 6% 3 4 3 4 4 32%	4428
	11th to 20th	Night	13% 15% 7% 14% 6% 4 4 5% 6% 5% 21%	4440
	21st to end	Night	16% 19% 9% 10% 5% 4 4 3 3 4 23%	4724
February	1st to 10th	Night	12% 13% 4 9% 5% 5% 4 3 4 5% 34%	2470
	11th to 20th	Night	12% 11% 4 7% 5% 4 4 3 4 6% 40%	2279
	21st to end	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 35%	1884
March	1st to 10th	Night	17% 10% 2 6% 4 3 4 3 4 4 42%	3733
	11th to 20th	Night	10% 7% 2 6% 4 4 4 3 6% 8% 47%	3618
	21st to end	Night	24% 12% 4 10% 5% 4 4 2 3 5% 28%	3512
April	1st to 10th	Night	18% 10% 3 6% 4 3 4 4 4 7% 37%	1900
	11th to 20th	Night	19% 9% 3 6% 4 4 4 3 4 6% 37%	1875
	21st to end	Night	18% 8% 2 6% 3 4 5% 4 5% 7% 38%	1844
May	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 3 6% 7% 36%	2676
	11th to 20th	Night	14% 7% 2 7% 4 5% 5% 4 5% 6% 41%	2506
	21st to end	Night	10% 8% 2 6% 4 5% 4 5% 6% 8% 43%	2743
June	1st to 10th	Night	8% 5% 2 6% 4 5% 3 5% 6% 8% 48%	1520
	11th to 20th	Night	12% 5% 2 5% 4 3 4 3 5% 9% 47%	1520
	21st to end	Night	10% 6% 2 6% 4 4 4 4 4 6% 49%	1520
July	1st to 10th	Night	15% 6% 2 5% 4 4 5% 4 5% 8% 41%	2530
	11th to 20th	Night	5% 3 1 5% 4 3 4 4 6% 9% 56%	2530
	21st to end	Night	7% 4 2 6% 4 4 5% 4 7% 8% 48%	2750
August	1st to 10th	Night	9% 4 2 5% 4 4 4 4 6% 8% 50%	2601
	11th to 20th	Night	10% 5% 2 4 4 3 4 4 5% 7% 51%	3029
	21st to end	Night	11% 4 2 5% 3 4 4 4 6% 7% 51%	3476
September	1st to 10th	Night	9% 4 2 5% 3 4 4 2 5% 7% 54%	1900
	11th to 20th	Night	12% 4 2 4 3 3 4 3 5% 7% 53%	1942
	21st to end	Night	11% 5% 2 5% 4 4 4 3 5% 6% 50%	2090
October	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 5% 6% 51%	2237
	11th to 20th	Night	17% 7% 2 5% 4 4 3 3 4 5% 45%	2280
	21st to end	Night	18% 8% 3 6% 4 4 4 4 5% 7% 37%	2678
November	1st to 10th	Night	12% 8% 3 6% 4 3 4 2 4 5% 48%	2433
	11th to 20th	Night	14% 10% 3 9% 5% 5% 4 3 5% 5% 36%	2470
	21st to end	Night	18% 10% 3 6% 4 3 3 3 5% 6% 38%	2660
December	1st to 10th	Night	15% 12% 4 9% 5% 5% 5% 4 5% 6% 31%	2660
	11th to 20th	Night	16% 14% 5% 10% 5% 4 4 4 5% 5% 30%	3279
	21st to end	Night	20% 18% 6% 10% 5% 5% 4 3 5% 4 20%	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	61% 3 12% 17% 6%	2528
	11th to 20th	Day	60% 3 14% 14% 8%	2530
	21st to end	Day	67% 2 9% 16% 5%	2941
February	1st to 10th	Day	54% 3 11% 19% 12% 1	1710
	11th to 20th	Day	49% 3 11% 24% 10% 2	1796
	21st to end	Day	53% 3 10% 20% 12% 2	1570
March	1st to 10th	Day	42% 3 12% 29% 12% 3	3120
	11th to 20th	Day	41% 3 10% 32% 13% 1	3370
	21st to end	Day	60% 3 12% 17% 7% 1	4119
April	1st to 10th	Day	55% 4 10% 21% 11% 1	2280
	11th to 20th	Day	51% 3 10% 22% 12% 2	2254
	21st to end	Day	52% 4 11% 19% 13% 2	2334
May	1st to 10th	Day	47% 3 10% 23% 16% 1	4245
	11th to 20th	Day	42% 3 10% 31% 13%	4403
	21st to end	Day	43% 4 10% 24% 15% 3	4837
June	1st to 10th	Day	36% 6% 14% 27% 16% 1	2660
	11th to 20th	Day	36% 6% 14% 24% 18% 2	2660
	21st to end	Day	42% 6% 14% 23% 14% 2	2660
July	1st to 10th	Day	45% 5% 14% 26% 9% 2	4371
	11th to 20th	Day	28% 5% 17% 31% 18% 1	4365
	21st to end	Day	39% 5% 14% 21% 18% 2	4662
August	1st to 10th	Day	38% 5% 14% 29% 12% 1	4322
	11th to 20th	Day	36% 3 14% 32% 13% 1	3839
	21st to end	Day	35% 4 13% 30% 16% 1	4179
September	1st to 10th	Day	38% 4 11% 27% 20% 1	2280
	11th to 20th	Day	33% 4 11% 34% 17% 2	2218
	21st to end	Day	40% 3 9% 30% 16% 1	2090
October	1st to 10th	Day	38% 4 9% 31% 17% 1	1938
	11th to 20th	Day	49% 3 10% 24% 13% 1	1900
	21st to end	Day	48% 3 10% 24% 13% 1	1919
November	1st to 10th	Day	41% 3 14% 26% 14% 2	1690
	11th to 20th	Day	51% 3 14% 21% 10% 1	1706
	21st to end	Day	50% 4 15% 23% 7%	1520
December	1st to 10th	Day	55% 4 15% 17% 8% 1	1520
	11th to 20th	Day	56% 2 16% 16% 8% 3	1915
	21st to end	Day	75% 3 8% 10% 5%	2783
January	1st to 10th	Night	58% 3 9% 20% 9% 1	4428
	11th to 20th	Night	63% 3 9% 15% 9%	4440
	21st to end	Night	67% 2 9% 16% 5% 1	4724
February	1st to 10th	Night	53% 4 9% 20% 12% 2	2470
	11th to 20th	Night	47% 4 11% 23% 15% 1	2280
	21st to end	Night	50% 3 11% 20% 12% 3	1884
March	1st to 10th	Night	47% 3 12% 24% 10% 5%	3733
	11th to 20th	Night	36% 3 10% 31% 18% 2	3618
	21st to end	Night	62% 3 7% 18% 10% 1	3512
April	1st to 10th	Night	47% 4 10% 23% 14% 2	1900
	11th to 20th	Night	48% 4 6% 20% 18% 3	1875
	21st to end	Night	46% 4 12% 24% 13% 2	1844
May	1st to 10th	Night	47% 4 12% 17% 18% 2	2703
	11th to 20th	Night	44% 3 10% 27% 14% 1	2507
	21st to end	Night	38% 4 12% 21% 21% 4	2751
June	1st to 10th	Night	33% 6% 13% 27% 20% 1	1520
	11th to 20th	Night	34% 4 10% 25% 24% 2	1520
	21st to end	Night	35% 5% 15% 24% 19% 3	1520
July	1st to 10th	Night	42% 4 15% 23% 12% 3	2490
	11th to 20th	Night	26% 4 15% 35% 18% 2	2482
	21st to end	Night	31% 6% 17% 22% 20% 3	2662
August	1st to 10th	Night	33% 4 15% 28% 20% 2	2592
	11th to 20th	Night	33% 4 12% 33% 17% 1	3058
	21st to end	Night	33% 5% 13% 29% 18% 3	3476
September	1st to 10th	Night	30% 5% 11% 28% 24% 3	1900
	11th to 20th	Night	31% 4 11% 34% 19% 2	1942
	21st to end	Night	35% 3 10% 31% 20% 1	2090
October	1st to 10th	Night	35% 3 8% 30% 21% 2	2237
	11th to 20th	Night	42% 3 11% 25% 18% 1	2280
	21st to end	Night	48% 3 11% 25% 13% 1	2678
November	1st to 10th	Night	39% 3 10% 28% 18% 2	2433
	11th to 20th	Night	50% 3 12% 21% 11% 1	2470
	21st to end	Night	48% 3 13% 24% 10% 1	2660
December	1st to 10th	Night	54% 4 12% 21% 9% 1	2660
	11th to 20th	Night	57% 3 12% 18% 8% 1	3281
	21st to end	Night	69% 3 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	18% 14% 30% 29% 9% 1	270
	11th to 20th	Day	22% 15% 34% 23% 6% 1	270
	21st to end	Day	23% 14% 33% 24% 6%	297
February	1st to 10th	Day	14% 20% 41% 18% 6% 1	270
	11th to 20th	Day	23% 20% 34% 20% 3	270
	21st to end	Day	24% 17% 44% 14% 2	225
March	1st to 10th	Day	16% 21% 43% 16% 5%	270
	11th to 20th	Day	21% 20% 34% 16% 7% 2	270
	21st to end	Day	29% 13% 30% 19% 7% 2	473
April	1st to 10th	Day	25% 15% 34% 21% 5%	460
	11th to 20th	Day	26% 17% 26% 18% 10% 2	452
	21st to end	Day	24% 13% 29% 21% 10% 2	460
May	1st to 10th	Day	21% 11% 31% 26% 8% 2	536
	11th to 20th	Day	20% 9% 32% 22% 14% 3	675
	21st to end	Day	17% 9% 28% 23% 17% 7%	734
June	1st to 10th	Day	9% 7% 30% 30% 18% 6%	680
	11th to 20th	Day	13% 5% 30% 30% 15% 6%	680
	21st to end	Day	14% 8% 28% 30% 16% 4	680
July	1st to 10th	Day	10% 3 16% 32% 25% 13%	671
	11th to 20th	Day	9% 5% 25% 30% 22% 9%	668
	21st to end	Day	7% 4 22% 35% 22% 9%	739
August	1st to 10th	Day	8% 5% 17% 35% 25% 11%	676
	11th to 20th	Day	13% 4 20% 26% 23% 14%	528
	21st to end	Day	13% 6% 18% 30% 24% 9%	539
September	1st to 10th	Day	14% 6% 23% 26% 23% 8%	490
	11th to 20th	Day	11% 4 19% 31% 23% 10%	490
	21st to end	Day	14% 12% 26% 24% 16% 7%	490
October	1st to 10th	Day	16% 11% 28% 27% 16% 2	338
	11th to 20th	Day	24% 17% 33% 20% 7% 1	300
	21st to end	Day	26% 16% 31% 21% 5% 1	330
November	1st to 10th	Day	14% 15% 37% 22% 10% 1	276
	11th to 20th	Day	20% 19% 34% 16% 10%	270
	21st to end	Day	25% 11% 40% 19% 5%	270
December	1st to 10th	Day	19% 19% 36% 18% 7% 1	270
	11th to 20th	Day	19% 14% 38% 20% 8% 1	270
	21st to end	Day	25% 17% 38% 18% 2	297
January	1st to 10th	Night	17% 14% 37% 24% 7% 1	950
	11th to 20th	Night	20% 13% 37% 25% 5% 1	950
	21st to end	Night	20% 12% 35% 27% 6%	1045
February	1st to 10th	Night	19% 11% 38% 26% 6%	950
	11th to 20th	Night	16% 16% 37% 26% 4	804
	21st to end	Night	22% 14% 38% 22% 3	628
March	1st to 10th	Night	23% 11% 37% 23% 5% 1	760
	11th to 20th	Night	17% 13% 34% 28% 8%	656
	21st to end	Night	24% 11% 30% 27% 7% 1	627
April	1st to 10th	Night	22% 12% 37% 24% 5%	570
	11th to 20th	Night	23% 14% 28% 28% 6%	563
	21st to end	Night	21% 9% 33% 28% 8% 1	570
May	1st to 10th	Night	18% 8% 34% 31% 8%	570
	11th to 20th	Night	20% 7% 30% 33% 11%	561
	21st to end	Night	13% 4 28% 38% 16% 1	617
June	1st to 10th	Night	9% 5% 25% 46% 15% 1	570
	11th to 20th	Night	15% 4 30% 38% 13% 1	570
	21st to end	Night	12% 3 25% 42% 16% 1	570
July	1st to 10th	Night	8% 2 16% 38% 31% 4	555
	11th to 20th	Night	8% 3 21% 43% 23% 3	552
	21st to end	Night	7% 2 19% 45% 25% 2	624
August	1st to 10th	Night	6% 1 16% 47% 26% 3	567
	11th to 20th	Night	9% 2 14% 40% 29% 6%	564
	21st to end	Night	11% 2 16% 42% 27% 2	627
September	1st to 10th	Night	9% 3 23% 36% 24% 5%	570
	11th to 20th	Night	12% 3 22% 34% 26% 3	612
	21st to end	Night	13% 7% 24% 34% 20% 2	760
October	1st to 10th	Night	14% 6% 29% 32% 17% 1	760
	11th to 20th	Night	20% 11% 31% 27% 10% 1	760
	21st to end	Night	22% 12% 32% 27% 7% 1	836
November	1st to 10th	Night	15% 10% 37% 27% 10% 1	749
	11th to 20th	Night	20% 14% 36% 23% 7%	760
	21st to end	Night	23% 11% 35% 24% 7%	950
December	1st to 10th	Night	21% 13% 36% 23% 7%	950
	11th to 20th	Night	23% 11% 34% 26% 5% 1	950
	21st to end	Night	29% 13% 32% 23% 3	1045

Page generated at 2024-10-31 02:39:25. Version ac07

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