Sigoglin Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sigoglin Hills Observatory clear sky chart from 2005-11-06 to 2025-07-21.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	120649
	Night	14% 9% 3 8% 5% 4 4 3 5% 7% 38%	118487
Transparency	Day	45% 4 10% 24% 15% 2	124362
	Night	45% 4 10% 23% 16% 3	122898
Seeing	Day	17% 7% 23% 25% 19% 10%	16017
	Night	18% 6% 23% 32% 18% 2	25676

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	15% 15% 7% 9% 5% 4 4 4 5% 6% 27%	4056
	11th to 20th	Day	13% 12% 5% 15% 4 5% 3 2 3 5% 31%	4060
	21st to end	Day	21% 10% 6% 7% 5% 5% 4 3 4 6% 29%	4466
February	1st to 10th	Day	18% 12% 5% 9% 5% 4 3 3 4 6% 31%	1933
	11th to 20th	Day	18% 11% 4 8% 5% 4 5% 3 4 5% 32%	1948
	21st to end	Day	18% 11% 3 8% 5% 5% 3 4 6% 6% 32%	1650
March	1st to 10th	Day	17% 13% 3 8% 4 4 4 3 4 5% 35%	4540
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	4980
	21st to end	Day	15% 8% 3 7% 5% 5% 5% 4 5% 7% 37%	5465
April	1st to 10th	Day	15% 9% 3 6% 5% 4 4 4 5% 8% 38%	2340
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 5% 7% 39%	2414
	21st to end	Day	16% 8% 2 7% 5% 5% 5% 4 6% 7% 36%	2600
May	1st to 10th	Day	17% 8% 3 8% 5% 5% 6% 5% 7% 9% 26%	5862
	11th to 20th	Day	17% 9% 3 8% 5% 4 5% 4 7% 7% 32%	5861
	21st to end	Day	13% 6% 2 6% 5% 5% 6% 5% 8% 11% 32%	6433
June	1st to 10th	Day	11% 4 2 7% 5% 5% 5% 5% 6% 8% 42%	2600
	11th to 20th	Day	8% 5% 2 6% 5% 6% 5% 5% 7% 9% 42%	2636
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 8% 10% 41%	2800
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 7% 10% 39%	4515
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 5% 8% 10% 43%	4250
	21st to end	Day	13% 10% 3 10% 7% 7% 6% 4 7% 8% 25%	4466
August	1st to 10th	Day	7% 5% 2 6% 5% 4 5% 4 8% 10% 45%	4104
	11th to 20th	Day	7% 6% 2 6% 5% 5% 5% 5% 8% 11% 39%	4026
	21st to end	Day	5% 3 2 5% 3 4 5% 4 6% 9% 55%	4180
September	1st to 10th	Day	14% 5% 2 5% 5% 4 5% 4 6% 7% 43%	2151
	11th to 20th	Day	11% 5% 2 5% 5% 4 4 4 5% 7% 48%	2090
	21st to end	Day	14% 7% 2 6% 4 3 3 3 5% 7% 46%	2090
October	1st to 10th	Day	10% 5% 1 5% 4 4 4 3 5% 7% 53%	2090
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 5% 6% 49%	1938
	21st to end	Day	19% 6% 2 6% 4 3 3 3 6% 6% 43%	1974
November	1st to 10th	Day	13% 5% 2 5% 3 4 3 3 4 5% 54%	1762
	11th to 20th	Day	16% 10% 3 7% 4 4 3 3 4 6% 41%	1800
	21st to end	Day	17% 9% 3 8% 4 3 4 3 5% 6% 37%	1800
December	1st to 10th	Day	16% 11% 3 8% 4 4 4 3 4 4 40%	2930
	11th to 20th	Day	18% 12% 4 9% 6% 5% 5% 3 4 5% 29%	3373
	21st to end	Day	18% 16% 5% 11% 6% 5% 5% 4 4 5% 22%	4466
January	1st to 10th	Night	14% 14% 5% 16% 7% 5% 4 4 5% 6% 22%	5889
	11th to 20th	Night	17% 13% 5% 12% 6% 5% 4 3 4 4 28%	5900
	21st to end	Night	19% 10% 4 7% 5% 4 3 3 4 5% 35%	6490
February	1st to 10th	Night	21% 11% 5% 7% 4 5% 4 3 5% 6% 29%	2465
	11th to 20th	Night	19% 11% 4 9% 5% 5% 4 3 4 6% 31%	2338
	21st to end	Night	20% 13% 4 7% 5% 4 4 3 4 4 31%	1980
March	1st to 10th	Night	17% 13% 3 7% 4 4 4 3 4 5% 36%	5310
	11th to 20th	Night	13% 6% 2 5% 4 4 5% 3 5% 6% 47%	4980
	21st to end	Night	15% 9% 3 8% 6% 5% 5% 4 6% 7% 33%	5467
April	1st to 10th	Night	13% 5% 2 6% 6% 5% 5% 4 7% 7% 39%	2075
	11th to 20th	Night	14% 7% 2 7% 4 4 4 3 5% 6% 44%	1933
	21st to end	Night	15% 7% 3 6% 4 5% 5% 3 6% 7% 38%	1800
May	1st to 10th	Night	16% 9% 3 9% 6% 5% 5% 4 6% 7% 27%	4033
	11th to 20th	Night	16% 7% 3 8% 5% 5% 5% 5% 7% 8% 31%	4032
	21st to end	Night	11% 6% 3 7% 5% 6% 5% 4 7% 9% 38%	4421
June	1st to 10th	Night	8% 4 2 5% 4 5% 5% 4 6% 10% 47%	1800
	11th to 20th	Night	6% 4 2 6% 4 4 6% 5% 6% 10% 48%	1753
	21st to end	Night	7% 4 1 4 5% 5% 4 5% 8% 10% 46%	1600
July	1st to 10th	Night	7% 5% 2 7% 5% 5% 5% 4 5% 11% 44%	2664
	11th to 20th	Night	6% 4 2 6% 4 4 4 4 7% 10% 48%	2930
	21st to end	Night	12% 10% 4 9% 4 5% 5% 4 6% 8% 33%	3087
August	1st to 10th	Night	6% 5% 2 6% 5% 4 4 4 6% 10% 47%	2825
	11th to 20th	Night	6% 5% 2 7% 5% 5% 5% 5% 7% 9% 44%	2799
	21st to end	Night	4 3 1 4 3 3 3 3 6% 9% 61%	3476
September	1st to 10th	Night	12% 5% 2 4 3 4 4 2 6% 9% 49%	2009
	11th to 20th	Night	10% 5% 2 4 4 4 4 2 5% 7% 53%	2090
	21st to end	Night	14% 6% 1 6% 3 3 4 3 5% 6% 50%	2090
October	1st to 10th	Night	9% 4 2 5% 3 3 3 4 4 7% 57%	2090
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 48%	2242
	21st to end	Night	17% 6% 2 7% 4 4 3 3 4 6% 45%	2621
November	1st to 10th	Night	12% 5% 2 5% 5% 3 4 4 4 5% 50%	2536
	11th to 20th	Night	15% 8% 3 8% 4 4 4 3 5% 6% 42%	2600
	21st to end	Night	16% 10% 3 7% 5% 3 4 2 5% 6% 38%	2600
December	1st to 10th	Night	16% 12% 4 7% 4 4 4 3 4 4 38%	4250
	11th to 20th	Night	19% 10% 5% 8% 4 3 4 2 5% 7% 33%	4822
	21st to end	Night	18% 15% 6% 11% 6% 5% 5% 4 5% 6% 20%	6490

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	58% 3 9% 21% 9% 1	4057
	11th to 20th	Day	58% 2 6% 19% 13% 2	4060
	21st to end	Day	58% 2 7% 22% 7% 3	4466
February	1st to 10th	Day	56% 2 8% 21% 11% 2	1933
	11th to 20th	Day	56% 2 7% 19% 12% 3	1958
	21st to end	Day	53% 2 8% 23% 11% 3	1650
March	1st to 10th	Day	53% 2 5% 18% 15% 6%	4540
	11th to 20th	Day	39% 4 9% 27% 19% 2	4980
	21st to end	Day	47% 3 12% 24% 12% 1	5465
April	1st to 10th	Day	46% 3 11% 25% 13% 3	2340
	11th to 20th	Day	45% 3 8% 25% 15% 3	2414
	21st to end	Day	47% 4 11% 24% 12% 2	2600
May	1st to 10th	Day	52% 5% 13% 18% 10% 1	5897
	11th to 20th	Day	50% 4 12% 22% 10%	5865
	21st to end	Day	43% 6% 16% 20% 14% 1	6447
June	1st to 10th	Day	40% 4 10% 27% 18% 1	2600
	11th to 20th	Day	37% 5% 15% 25% 17% 2	2636
	21st to end	Day	37% 5% 14% 23% 17% 3	2800
July	1st to 10th	Day	39% 5% 14% 23% 18% 1	4447
	11th to 20th	Day	32% 6% 14% 33% 14% 1	4181
	21st to end	Day	55% 6% 11% 16% 10% 2	4324
August	1st to 10th	Day	31% 6% 15% 35% 12% 1	4091
	11th to 20th	Day	35% 6% 13% 29% 15% 1	4065
	21st to end	Day	26% 4 13% 33% 20% 3	4179
September	1st to 10th	Day	40% 3 10% 20% 20% 5%	2151
	11th to 20th	Day	36% 4 9% 25% 23% 3	2090
	21st to end	Day	39% 2 7% 28% 21% 3	2090
October	1st to 10th	Day	22% 3 6% 28% 39% 3	3480
	11th to 20th	Day	25% 3 10% 29% 31% 2	3204
	21st to end	Day	31% 2 9% 29% 23% 6%	3224
November	1st to 10th	Day	35% 2 7% 28% 24% 4	1762
	11th to 20th	Day	45% 2 8% 23% 19% 4	1800
	21st to end	Day	49% 2 7% 23% 18% 2	1800
December	1st to 10th	Day	50% 2 8% 23% 17% 1	2930
	11th to 20th	Day	60% 2 7% 18% 11% 1	3370
	21st to end	Day	65% 3 9% 16% 6% 1	4466
January	1st to 10th	Night	63% 2 7% 17% 10% 1	5889
	11th to 20th	Night	61% 3 6% 17% 10% 4	5900
	21st to end	Night	52% 2 7% 23% 13% 2	6490
February	1st to 10th	Night	56% 3 9% 21% 10% 1	2465
	11th to 20th	Night	57% 3 6% 21% 13% 1	2339
	21st to end	Night	57% 2 9% 16% 12% 3	1980
March	1st to 10th	Night	51% 2 5% 24% 14% 4	5310
	11th to 20th	Night	38% 3 9% 28% 21% 2	4980
	21st to end	Night	50% 3 8% 24% 13% 1	5467
April	1st to 10th	Night	42% 4 11% 24% 17% 2	2075
	11th to 20th	Night	42% 2 9% 22% 20% 6%	1933
	21st to end	Night	44% 3 11% 24% 15% 2	1800
May	1st to 10th	Night	54% 6% 10% 20% 8% 2	4060
	11th to 20th	Night	50% 6% 12% 23% 9% 1	4033
	21st to end	Night	41% 5% 16% 23% 13% 2	4429
June	1st to 10th	Night	32% 4 13% 29% 18% 4	1800
	11th to 20th	Night	32% 6% 15% 24% 20% 3	1753
	21st to end	Night	30% 6% 17% 24% 18% 5%	1600
July	1st to 10th	Night	36% 7% 12% 24% 18% 3	2623
	11th to 20th	Night	29% 7% 14% 32% 17% 2	2876
	21st to end	Night	47% 6% 11% 21% 13% 1	2988
August	1st to 10th	Night	30% 6% 16% 33% 13% 1	2814
	11th to 20th	Night	34% 6% 12% 30% 17% 1	2826
	21st to end	Night	20% 5% 14% 34% 22% 4	3476
September	1st to 10th	Night	33% 4 14% 23% 20% 7%	2009
	11th to 20th	Night	32% 3 9% 27% 26% 3	2090
	21st to end	Night	37% 3 7% 25% 24% 3	2090
October	1st to 10th	Night	22% 3 7% 23% 42% 3	3480
	11th to 20th	Night	26% 2 7% 26% 34% 5%	3715
	21st to end	Night	31% 2 7% 22% 30% 8%	4308
November	1st to 10th	Night	36% 3 7% 25% 24% 4	2536
	11th to 20th	Night	44% 2 7% 21% 22% 5%	2600
	21st to end	Night	48% 2 8% 25% 15% 2	2600
December	1st to 10th	Night	50% 3 10% 23% 13% 1	4250
	11th to 20th	Night	52% 3 11% 22% 12% 1	4824
	21st to end	Night	66% 3 9% 15% 7%	6490

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	21% 13% 37% 20% 9% 1	300
	11th to 20th	Day	25% 19% 32% 20% 3	300
	21st to end	Day	22% 15% 42% 15% 4 1	330
February	1st to 10th	Day	22% 12% 41% 19% 5%	300
	11th to 20th	Day	28% 16% 35% 16% 4 1	300
	21st to end	Day	28% 11% 41% 15% 4	249
March	1st to 10th	Day	23% 14% 35% 21% 7% 1	321
	11th to 20th	Day	20% 13% 37% 23% 6% 1	500
	21st to end	Day	23% 14% 34% 21% 7% 1	550
April	1st to 10th	Day	21% 13% 29% 23% 13% 2	500
	11th to 20th	Day	17% 12% 30% 24% 12% 5%	492
	21st to end	Day	20% 8% 29% 26% 12% 4	500
May	1st to 10th	Day	20% 7% 29% 25% 14% 5%	503
	11th to 20th	Day	18% 4 22% 28% 20% 9%	527
	21st to end	Day	13% 4 21% 26% 21% 16%	573
June	1st to 10th	Day	14% 3 16% 26% 26% 15%	530
	11th to 20th	Day	10% 2 16% 30% 28% 13%	566
	21st to end	Day	9% 4 15% 32% 25% 15%	730
July	1st to 10th	Day	16% 1 10% 22% 25% 25%	683
	11th to 20th	Day	9% 2 12% 26% 30% 21%	524
	21st to end	Day	13% 2 9% 26% 31% 20%	532
August	1st to 10th	Day	13% 1 9% 23% 29% 24%	486
	11th to 20th	Day	12% 1 8% 31% 31% 16%	479
	21st to end	Day	10% 1 8% 23% 35% 23%	539
September	1st to 10th	Day	16% 1 8% 26% 27% 21%	490
	11th to 20th	Day	13% 1 9% 23% 33% 21%	490
	21st to end	Day	17% 4 17% 22% 29% 10%	490
October	1st to 10th	Day	11% 2 16% 34% 26% 11%	490
	11th to 20th	Day	13% 8% 27% 29% 16% 6%	490
	21st to end	Day	21% 6% 28% 28% 13% 2	423
November	1st to 10th	Day	18% 4 29% 28% 15% 5%	300
	11th to 20th	Day	23% 8% 31% 25% 9% 3	300
	21st to end	Day	22% 9% 32% 27% 8% 2	300
December	1st to 10th	Day	23% 13% 31% 24% 8% 1	300
	11th to 20th	Day	19% 13% 37% 21% 10%	300
	21st to end	Day	25% 12% 36% 19% 7%	330
January	1st to 10th	Night	22% 11% 37% 25% 5%	800
	11th to 20th	Night	29% 12% 33% 22% 4	800
	21st to end	Night	24% 9% 35% 28% 4	880
February	1st to 10th	Night	28% 9% 34% 27% 3	800
	11th to 20th	Night	26% 11% 38% 24% 2	783
	21st to end	Night	27% 10% 37% 24% 2	660
March	1st to 10th	Night	22% 13% 30% 29% 6%	800
	11th to 20th	Night	23% 9% 32% 28% 7% 1	800
	21st to end	Night	20% 9% 32% 32% 8%	880
April	1st to 10th	Night	17% 9% 31% 35% 8%	675
	11th to 20th	Night	16% 7% 30% 33% 12% 1	593
	21st to end	Night	18% 4 31% 34% 11% 1	600
May	1st to 10th	Night	20% 3 25% 35% 15% 3	600
	11th to 20th	Night	17% 3 17% 39% 21% 2	591
	21st to end	Night	10% 2 15% 38% 29% 5%	650
June	1st to 10th	Night	11% 14% 45% 27% 3	600
	11th to 20th	Night	9% 2 11% 40% 34% 4	600
	21st to end	Night	8% 1 12% 43% 32% 4	600
July	1st to 10th	Night	12% 1 9% 31% 34% 12%	585
	11th to 20th	Night	8% 1 8% 36% 42% 5%	582
	21st to end	Night	11% 1 8% 37% 37% 6%	624
August	1st to 10th	Night	9% 1 5% 36% 43% 6%	567
	11th to 20th	Night	8% 1 6% 37% 41% 7%	564
	21st to end	Night	8% 4 34% 45% 8%	627
September	1st to 10th	Night	13% 1 7% 33% 40% 6%	679
	11th to 20th	Night	13% 2 9% 31% 39% 7%	760
	21st to end	Night	16% 3 15% 33% 30% 3	760
October	1st to 10th	Night	10% 3 17% 36% 29% 6%	760
	11th to 20th	Night	16% 4 25% 36% 18% 2	760
	21st to end	Night	21% 6% 26% 31% 14% 1	836
November	1st to 10th	Night	16% 6% 23% 35% 18% 2	780
	11th to 20th	Night	18% 7% 32% 31% 11% 1	800
	21st to end	Night	22% 8% 27% 31% 11% 1	800
December	1st to 10th	Night	25% 8% 31% 30% 6%	800
	11th to 20th	Night	25% 7% 32% 30% 6% 1	800
	21st to end	Night	27% 13% 30% 26% 4	880

Page generated at 2025-07-18 01:09:58. Version ac07

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