Kristina Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kristina Observatory clear sky chart from 2005-11-06 to 2026-01-02.

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	16% 7% 2 6% 4 4 4 4 5% 8% 41%	127173
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 42%	124190
Transparency	Day	40% 5% 12% 23% 17% 2	130713
	Night	42% 4 11% 23% 17% 3	128737
Seeing	Day	17% 5% 23% 32% 18% 4	16493
	Night	19% 8% 29% 29% 14% 2	25675

By Month

Percentage Cloud Cover NE (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% 6% 2 4 3 3 3 3 4 6% 53%	3605
	11th to 20th	Day	13% 8% 2 6% 4 4 4 3 4 6% 45%	3570
	21st to end	Day	19% 9% 3 6% 4 3 3 3 4 5% 40%	4280
February	1st to 10th	Day	16% 9% 2 6% 4 4 3 3 5% 7% 40%	1842
	11th to 20th	Day	15% 8% 3 7% 4 3 3 3 4 6% 43%	1948
	21st to end	Day	19% 7% 2 6% 4 3 4 3 5% 6% 39%	1650
March	1st to 10th	Day	21% 6% 2 4 3 3 3 3 4 6% 46%	4476
	11th to 20th	Day	12% 10% 2 6% 3 4 4 4 6% 7% 44%	4704
	21st to end	Day	17% 6% 2 5% 4 4 4 3 5% 6% 44%	5965
April	1st to 10th	Day	18% 8% 2 5% 4 4 4 3 5% 8% 40%	2400
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 6% 7% 42%	2374
	21st to end	Day	17% 6% 2 5% 4 4 4 4 7% 7% 41%	2439
May	1st to 10th	Day	26% 9% 3 6% 4 4 5% 3 6% 8% 28%	5886
	11th to 20th	Day	22% 9% 2 6% 4 3 3 3 4 6% 37%	6176
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 8% 36%	6949
June	1st to 10th	Day	16% 6% 2 5% 4 5% 4 4 7% 9% 38%	2800
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 6% 9% 40%	2800
	21st to end	Day	10% 6% 2 5% 4 5% 5% 4 6% 10% 44%	2800
July	1st to 10th	Day	9% 7% 3 8% 6% 5% 5% 4 6% 10% 37%	6360
	11th to 20th	Day	9% 7% 3 7% 5% 5% 6% 6% 8% 11% 33%	6360
	21st to end	Day	11% 7% 2 6% 4 5% 5% 4 6% 9% 42%	6926
August	1st to 10th	Day	16% 5% 3 7% 4 4 4 4 7% 9% 37%	4279
	11th to 20th	Day	13% 5% 2 5% 4 3 5% 4 6% 8% 45%	3850
	21st to end	Day	8% 4 2 4 4 4 4 4 6% 10% 49%	4312
September	1st to 10th	Day	12% 6% 2 6% 4 3 3 3 5% 9% 47%	2400
	11th to 20th	Day	12% 5% 1 4 3 3 4 3 5% 7% 53%	2295
	21st to end	Day	18% 7% 3 6% 4 3 4 4 6% 6% 39%	2200
October	1st to 10th	Day	18% 6% 2 6% 3 3 3 3 5% 6% 45%	2120
	11th to 20th	Day	16% 4 2 4 3 3 3 3 5% 8% 48%	2000
	21st to end	Day	17% 6% 2 6% 3 3 3 3 5% 7% 45%	2025
November	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 4 6% 52%	1851
	11th to 20th	Day	15% 5% 2 5% 3 3 3 3 5% 6% 48%	1890
	21st to end	Day	16% 6% 2 4 4 3 4 3 5% 7% 45%	1847
December	1st to 10th	Day	14% 7% 2 5% 4 3 4 3 5% 7% 45%	2680
	11th to 20th	Day	20% 8% 2 5% 3 2 3 2 3 6% 46%	3066
	21st to end	Day	17% 8% 3 6% 3 4 4 4 4 6% 40%	4048
January	1st to 10th	Night	14% 5% 2 5% 4 3 3 3 5% 7% 50%	6364
	11th to 20th	Night	15% 8% 3 5% 3 3 3 3 4 5% 47%	6315
	21st to end	Night	18% 10% 2 5% 4 3 5% 3 5% 6% 39%	6674
February	1st to 10th	Night	18% 8% 3 5% 4 3 4 3 5% 6% 40%	2556
	11th to 20th	Night	19% 8% 2 5% 4 4 4 3 5% 5% 41%	2338
	21st to end	Night	19% 7% 2 5% 3 3 4 3 5% 5% 42%	1980
March	1st to 10th	Night	18% 9% 3 5% 3 3 2 3 4 5% 45%	5364
	11th to 20th	Night	14% 11% 3 5% 4 3 4 3 4 6% 43%	5237
	21st to end	Night	19% 8% 3 7% 4 4 3 4 5% 5% 39%	4966
April	1st to 10th	Night	18% 8% 3 7% 4 4 4 3 5% 6% 38%	2000
	11th to 20th	Night	19% 7% 2 7% 4 3 4 3 5% 7% 40%	1975
	21st to end	Night	17% 7% 3 6% 4 4 4 3 4 7% 41%	1960
May	1st to 10th	Night	25% 11% 3 7% 4 4 4 3 5% 7% 27%	4054
	11th to 20th	Night	23% 9% 3 6% 4 4 3 3 4 5% 35%	3759
	21st to end	Night	22% 9% 2 6% 4 3 4 3 5% 7% 35%	3926
June	1st to 10th	Night	18% 7% 2 5% 3 4 3 4 7% 7% 40%	1600
	11th to 20th	Night	14% 6% 4 6% 3 4 4 4 7% 9% 39%	1600
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 5% 6% 9% 40%	1600
July	1st to 10th	Night	9% 10% 3 8% 5% 5% 5% 4 6% 8% 34%	3600
	11th to 20th	Night	13% 9% 3 8% 5% 5% 5% 4 7% 9% 32%	3600
	21st to end	Night	13% 6% 3 6% 4 4 4 4 6% 9% 41%	3926
August	1st to 10th	Night	21% 7% 2 7% 5% 4 5% 4 6% 8% 31%	2831
	11th to 20th	Night	14% 7% 2 7% 4 5% 5% 4 7% 8% 39%	3197
	21st to end	Night	9% 4 2 5% 4 4 4 3 5% 8% 52%	3586
September	1st to 10th	Night	14% 5% 2 6% 4 4 5% 4 5% 7% 43%	2000
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 5% 52%	2105
	21st to end	Night	18% 7% 3 7% 4 3 3 3 5% 7% 41%	2200
October	1st to 10th	Night	19% 6% 2 6% 4 4 3 3 4 5% 44%	2277
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 5% 6% 50%	2400
	21st to end	Night	20% 6% 2 6% 3 3 3 3 4 6% 43%	2814
November	1st to 10th	Night	12% 5% 2 5% 4 4 4 2 5% 6% 51%	2667
	11th to 20th	Night	18% 6% 2 5% 4 3 3 3 4 5% 48%	2730
	21st to end	Night	14% 5% 2 5% 4 4 4 3 4 7% 47%	2771
December	1st to 10th	Night	16% 7% 2 5% 3 3 4 3 4 6% 48%	4720
	11th to 20th	Night	25% 7% 2 4 3 3 3 3 4 5% 43%	5348
	21st to end	Night	18% 8% 3 6% 4 3 4 3 5% 5% 42%	7150

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	33% 2 7% 33% 22% 2	3606
	11th to 20th	Day	41% 3 9% 25% 17% 5%	3600
	21st to end	Day	48% 4 10% 24% 13% 1	4280
February	1st to 10th	Day	44% 4 13% 24% 13% 1	1842
	11th to 20th	Day	43% 4 9% 25% 17% 2	1957
	21st to end	Day	45% 4 10% 24% 13% 4	1650
March	1st to 10th	Day	40% 4 11% 21% 16% 8%	4479
	11th to 20th	Day	38% 5% 12% 28% 14% 3	4704
	21st to end	Day	41% 4 10% 15% 25% 5%	5965
April	1st to 10th	Day	42% 5% 11% 20% 17% 5%	2400
	11th to 20th	Day	40% 5% 12% 24% 17% 3	2374
	21st to end	Day	41% 5% 9% 22% 19% 4	2439
May	1st to 10th	Day	54% 6% 15% 15% 10% 1	5897
	11th to 20th	Day	49% 4 11% 21% 14% 1	6180
	21st to end	Day	46% 5% 10% 23% 14% 1	6949
June	1st to 10th	Day	41% 6% 13% 23% 16% 1	2800
	11th to 20th	Day	40% 7% 14% 25% 13% 2	2800
	21st to end	Day	34% 7% 16% 25% 16% 1	2800
July	1st to 10th	Day	43% 9% 12% 21% 15%	6290
	11th to 20th	Day	42% 8% 19% 20% 9% 1	6285
	21st to end	Day	38% 6% 12% 23% 20% 1	6728
August	1st to 10th	Day	43% 7% 17% 24% 9%	4265
	11th to 20th	Day	35% 6% 16% 32% 10% 1	3886
	21st to end	Day	29% 5% 13% 30% 21% 1	4312
September	1st to 10th	Day	35% 6% 13% 25% 20% 2	2400
	11th to 20th	Day	31% 4 12% 27% 24% 2	2295
	21st to end	Day	45% 4 11% 19% 19% 2	2200
October	1st to 10th	Day	32% 4 13% 23% 23% 5%	3458
	11th to 20th	Day	25% 3 12% 24% 32% 5%	3240
	21st to end	Day	29% 3 14% 27% 24% 3	3250
November	1st to 10th	Day	35% 3 13% 25% 20% 3	1851
	11th to 20th	Day	37% 3 11% 24% 22% 3	1890
	21st to end	Day	39% 4 15% 30% 11% 2	1847
December	1st to 10th	Day	40% 3 16% 27% 12% 1	2680
	11th to 20th	Day	42% 2 12% 25% 16% 3	3066
	21st to end	Day	44% 5% 10% 22% 16% 2	4048
January	1st to 10th	Night	35% 2 8% 26% 25% 3	6364
	11th to 20th	Night	40% 3 13% 23% 16% 6%	6360
	21st to end	Night	47% 3 8% 21% 17% 3	6674
February	1st to 10th	Night	44% 4 14% 24% 11% 2	2556
	11th to 20th	Night	45% 4 9% 21% 18% 4	2340
	21st to end	Night	45% 3 7% 24% 17% 4	1980
March	1st to 10th	Night	43% 3 9% 22% 13% 9%	5374
	11th to 20th	Night	43% 4 11% 25% 12% 5%	5238
	21st to end	Night	47% 4 6% 14% 23% 5%	4966
April	1st to 10th	Night	47% 4 9% 20% 17% 4	2000
	11th to 20th	Night	45% 4 9% 19% 22% 2	1975
	21st to end	Night	43% 5% 8% 21% 19% 5%	1960
May	1st to 10th	Night	56% 6% 12% 14% 10% 2	4060
	11th to 20th	Night	53% 4 12% 16% 14% 2	3760
	21st to end	Night	49% 5% 11% 21% 12% 2	3927
June	1st to 10th	Night	43% 5% 9% 22% 20% 1	1600
	11th to 20th	Night	41% 6% 15% 26% 11% 1	1600
	21st to end	Night	39% 7% 13% 25% 14% 2	1600
July	1st to 10th	Night	47% 7% 11% 21% 12% 1	3560
	11th to 20th	Night	47% 7% 14% 23% 9% 1	3552
	21st to end	Night	39% 5% 14% 23% 17% 1	3809
August	1st to 10th	Night	50% 7% 16% 17% 9% 1	2821
	11th to 20th	Night	40% 6% 14% 28% 10% 1	3227
	21st to end	Night	30% 5% 12% 32% 20% 1	3586
September	1st to 10th	Night	40% 5% 11% 24% 19% 2	2000
	11th to 20th	Night	34% 5% 10% 25% 24% 3	2105
	21st to end	Night	45% 4 8% 22% 19% 2	2200
October	1st to 10th	Night	38% 4 11% 24% 20% 3	3719
	11th to 20th	Night	25% 3 11% 27% 30% 4	3899
	21st to end	Night	31% 3 12% 30% 22% 3	4539
November	1st to 10th	Night	35% 4 11% 25% 21% 4	2667
	11th to 20th	Night	40% 3 9% 23% 21% 4	2730
	21st to end	Night	38% 4 12% 29% 16% 1	2771
December	1st to 10th	Night	39% 3 13% 29% 13% 2	4720
	11th to 20th	Night	45% 3 10% 24% 15% 3	5348
	21st to end	Night	44% 4 11% 20% 17% 4	7150

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	14% 14% 42% 20% 8% 1	202
	11th to 20th	Day	14% 15% 48% 19% 4 1	200
	21st to end	Day	20% 7% 39% 25% 8% 1	290
February	1st to 10th	Day	23% 7% 35% 29% 5%	342
	11th to 20th	Day	20% 13% 38% 26% 2	496
	21st to end	Day	22% 10% 34% 28% 5% 1	414
March	1st to 10th	Day	16% 10% 37% 30% 7%	500
	11th to 20th	Day	16% 6% 41% 29% 7% 1	500
	21st to end	Day	21% 6% 34% 29% 8% 1	550
April	1st to 10th	Day	22% 7% 32% 30% 9%	500
	11th to 20th	Day	19% 9% 24% 35% 11% 1	492
	21st to end	Day	20% 7% 27% 34% 11% 1	500
May	1st to 10th	Day	27% 5% 23% 32% 11% 2	503
	11th to 20th	Day	21% 2 20% 39% 15% 2	527
	21st to end	Day	19% 3 14% 31% 28% 5%	573
June	1st to 10th	Day	18% 2 17% 37% 23% 3	530
	11th to 20th	Day	16% 2 19% 38% 22% 4	530
	21st to end	Day	13% 2 14% 39% 28% 4	530
July	1st to 10th	Day	11% 3 9% 37% 33% 8%	525
	11th to 20th	Day	8% 2 9% 35% 36% 9%	524
	21st to end	Day	12% 2 11% 38% 33% 4	576
August	1st to 10th	Day	11% 2 8% 42% 31% 7%	526
	11th to 20th	Day	14% 2 8% 33% 36% 7%	519
	21st to end	Day	11% 2 12% 37% 28% 9%	583
September	1st to 10th	Day	16% 2 15% 32% 26% 10%	530
	11th to 20th	Day	14% 2 12% 34% 30% 9%	530
	21st to end	Day	23% 3 17% 34% 19% 5%	530
October	1st to 10th	Day	23% 3 16% 29% 23% 7%	530
	11th to 20th	Day	17% 5% 26% 29% 19% 4	530
	21st to end	Day	19% 7% 30% 26% 16% 3	487
November	1st to 10th	Day	14% 7% 26% 34% 16% 3	425
	11th to 20th	Day	15% 12% 36% 27% 10%	430
	21st to end	Day	19% 11% 34% 26% 10% 1	387
December	1st to 10th	Day	17% 8% 40% 25% 10%	220
	11th to 20th	Day	23% 15% 30% 24% 7%	220
	21st to end	Day	24% 10% 31% 22% 12%	242
January	1st to 10th	Night	18% 16% 42% 20% 4	805
	11th to 20th	Night	24% 13% 35% 24% 5%	800
	21st to end	Night	18% 14% 43% 22% 3	880
February	1st to 10th	Night	22% 13% 38% 25% 3	800
	11th to 20th	Night	22% 15% 40% 20% 1	783
	21st to end	Night	21% 12% 38% 25% 5%	660
March	1st to 10th	Night	20% 10% 40% 24% 6%	800
	11th to 20th	Night	20% 9% 37% 27% 7% 1	800
	21st to end	Night	20% 7% 36% 29% 7% 1	880
April	1st to 10th	Night	20% 7% 36% 29% 7% 1	800
	11th to 20th	Night	20% 6% 30% 35% 9%	791
	21st to end	Night	19% 4 29% 36% 10% 1	760
May	1st to 10th	Night	23% 6% 25% 32% 13% 2	600
	11th to 20th	Night	22% 3 26% 36% 12% 1	474
	21st to end	Night	20% 3 13% 34% 24% 5%	433
June	1st to 10th	Night	20% 3 15% 36% 23% 3	400
	11th to 20th	Night	16% 1 14% 43% 25% 2	400
	21st to end	Night	9% 2 16% 45% 26% 2	400
July	1st to 10th	Night	12% 4 12% 36% 33% 4	390
	11th to 20th	Night	11% 3 11% 35% 34% 6%	388
	21st to end	Night	10% 2 14% 39% 31% 3	438
August	1st to 10th	Night	12% 2 10% 40% 33% 3	539
	11th to 20th	Night	13% 2 12% 32% 35% 5%	790
	21st to end	Night	13% 2 12% 34% 32% 6%	880
September	1st to 10th	Night	17% 2 19% 32% 26% 5%	800
	11th to 20th	Night	16% 3 14% 34% 28% 7%	800
	21st to end	Night	22% 2 19% 33% 21% 3	800
October	1st to 10th	Night	22% 5% 22% 26% 20% 5%	800
	11th to 20th	Night	17% 9% 26% 33% 15% 2	800
	21st to end	Night	22% 7% 32% 27% 11% 1	880
November	1st to 10th	Night	14% 8% 32% 30% 13% 2	820
	11th to 20th	Night	19% 13% 33% 24% 10%	840
	21st to end	Night	16% 15% 35% 25% 8% 1	840
December	1st to 10th	Night	23% 14% 34% 21% 7% 1	840
	11th to 20th	Night	22% 12% 37% 25% 4	840
	21st to end	Night	22% 11% 39% 24% 4	924

Page generated at 2025-12-30 01:14:10. Version ac07

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