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 2024-11-12.

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 6% 8% 41%	101325
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 41%	97861
Transparency	Day	40% 5% 13% 24% 16% 2	104883
	Night	42% 5% 11% 23% 16% 2	102392
Seeing	Day	17% 5% 23% 32% 18% 4	15080
	Night	19% 7% 29% 29% 14% 2	24196

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	16% 7% 2 5% 4 3 3 3 4 5% 48%	2517
	11th to 20th	Day	15% 9% 2 6% 4 5% 4 3 4 8% 39%	2520
	21st to end	Day	22% 10% 3 7% 4 4 3 3 4 6% 34%	2994
February	1st to 10th	Day	17% 9% 2 5% 4 4 3 3 5% 7% 40%	1749
	11th to 20th	Day	14% 7% 3 7% 4 4 3 3 4 6% 44%	1848
	21st to end	Day	19% 7% 2 7% 5% 3 5% 3 5% 6% 38%	1570
March	1st to 10th	Day	27% 7% 2 4 3 2 2 3 4 6% 39%	3116
	11th to 20th	Day	9% 4 2 6% 3 4 5% 4 7% 8% 48%	3288
	21st to end	Day	20% 6% 2 5% 3 3 3 3 5% 5% 44%	4161
April	1st to 10th	Day	17% 8% 2 5% 4 4 4 3 5% 8% 41%	2280
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 6% 7% 43%	2254
	21st to end	Day	18% 6% 2 5% 4 4 4 4 7% 7% 41%	2317
May	1st to 10th	Day	26% 10% 3 6% 4 3 5% 3 5% 8% 28%	4106
	11th to 20th	Day	23% 8% 2 6% 4 4 4 3 5% 6% 34%	4298
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 10% 42%	4837
June	1st to 10th	Day	16% 6% 2 5% 4 4 4 4 7% 9% 38%	2660
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 4 6% 9% 40%	2660
	21st to end	Day	9% 6% 2 5% 4 4 5% 4 6% 10% 44%	2660
July	1st to 10th	Day	8% 8% 4 9% 6% 6% 5% 5% 6% 9% 36%	4440
	11th to 20th	Day	10% 6% 2 5% 5% 5% 6% 5% 8% 10% 38%	4440
	21st to end	Day	12% 8% 3 6% 5% 6% 6% 5% 7% 8% 35%	4814
August	1st to 10th	Day	16% 5% 3 7% 4 4 5% 4 7% 9% 36%	4148
	11th to 20th	Day	13% 5% 2 5% 4 3 5% 4 6% 8% 45%	3730
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 10% 49%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 3 3 3 5% 9% 46%	2280
	11th to 20th	Day	12% 5% 1 5% 3 3 4 3 5% 8% 52%	2180
	21st to end	Day	18% 7% 2 6% 4 2 4 4 6% 6% 40%	2090
October	1st to 10th	Day	19% 7% 2 6% 3 3 4 3 5% 6% 43%	2014
	11th to 20th	Day	15% 4 2 4 3 3 3 3 5% 8% 49%	1900
	21st to end	Day	17% 6% 2 6% 3 3 3 3 5% 7% 44%	1924
November	1st to 10th	Day	13% 6% 2 6% 3 3 3 3 4 6% 52%	1761
	11th to 20th	Day	16% 5% 2 5% 4 4 3 3 5% 6% 47%	1719
	21st to end	Day	15% 7% 2 4 5% 3 4 3 5% 7% 46%	1672
December	1st to 10th	Day	17% 8% 3 6% 4 4 4 4 6% 7% 38%	1520
	11th to 20th	Day	19% 8% 2 5% 4 2 3 2 4 6% 45%	1906
	21st to end	Day	18% 9% 3 6% 4 5% 5% 4 4 7% 34%	2772
January	1st to 10th	Night	18% 6% 2 5% 4 3 3 3 5% 7% 45%	4429
	11th to 20th	Night	18% 9% 3 6% 3 3 3 3 4 5% 43%	4440
	21st to end	Night	25% 11% 3 5% 3 3 4 3 4 5% 34%	4660
February	1st to 10th	Night	17% 8% 3 5% 4 3 4 3 5% 7% 41%	2429
	11th to 20th	Night	18% 9% 2 6% 4 4 4 3 4 5% 41%	2218
	21st to end	Night	20% 7% 2 5% 3 3 4 3 5% 5% 43%	1884
March	1st to 10th	Night	23% 10% 3 6% 4 3 2 3 4 5% 37%	3724
	11th to 20th	Night	12% 7% 3 5% 4 4 4 3 6% 7% 44%	3653
	21st to end	Night	22% 8% 2 6% 3 3 3 3 4 4 41%	3470
April	1st to 10th	Night	17% 8% 3 7% 4 4 4 3 5% 7% 38%	1900
	11th to 20th	Night	18% 8% 2 7% 4 3 4 3 5% 7% 40%	1875
	21st to end	Night	17% 7% 3 6% 4 4 4 3 4 7% 41%	1862
May	1st to 10th	Night	23% 12% 3 7% 4 4 4 3 5% 7% 28%	2834
	11th to 20th	Night	25% 9% 3 7% 4 4 3 3 4 5% 32%	2623
	21st to end	Night	16% 9% 2 6% 4 3 4 3 5% 9% 40%	2738
June	1st to 10th	Night	18% 7% 2 5% 3 4 3 4 6% 7% 40%	1520
	11th to 20th	Night	13% 5% 4 6% 3 4 4 4 7% 9% 40%	1520
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 5% 6% 10% 40%	1520
July	1st to 10th	Night	9% 11% 3 8% 5% 5% 5% 5% 7% 8% 34%	2520
	11th to 20th	Night	11% 7% 2 7% 5% 4 5% 5% 7% 10% 37%	2520
	21st to end	Night	17% 8% 3 6% 5% 4 4 4 6% 8% 34%	2739
August	1st to 10th	Night	21% 7% 2 7% 5% 5% 5% 4 6% 8% 31%	2744
	11th to 20th	Night	14% 7% 2 7% 4 5% 4 4 7% 8% 39%	3097
	21st to end	Night	9% 4 2 5% 4 4 4 3 5% 8% 52%	3476
September	1st to 10th	Night	15% 5% 2 6% 4 4 5% 4 5% 7% 43%	1900
	11th to 20th	Night	13% 6% 1 5% 3 3 3 3 5% 6% 53%	2000
	21st to end	Night	18% 7% 3 7% 3 3 3 3 5% 7% 41%	2090
October	1st to 10th	Night	20% 6% 2 6% 4 4 4 3 4 5% 42%	2163
	11th to 20th	Night	14% 5% 2 5% 3 3 4 3 5% 6% 50%	2280
	21st to end	Night	21% 6% 2 6% 3 3 3 3 4 6% 43%	2673
November	1st to 10th	Night	13% 5% 2 5% 4 4 4 2 4 6% 51%	2537
	11th to 20th	Night	19% 6% 2 5% 3 3 3 3 4 5% 47%	2484
	21st to end	Night	14% 5% 2 5% 4 4 4 4 5% 7% 47%	2507
December	1st to 10th	Night	21% 7% 2 6% 4 3 4 3 5% 6% 39%	2660
	11th to 20th	Night	19% 6% 2 4 4 3 4 4 5% 6% 42%	3288
	21st to end	Night	19% 8% 3 6% 5% 4 4 3 5% 5% 37%	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	40% 3 10% 30% 15% 2	2518
	11th to 20th	Day	45% 4 10% 26% 14% 1	2520
	21st to end	Day	53% 4 9% 23% 8% 2	2994
February	1st to 10th	Day	44% 4 13% 24% 13% 1	1749
	11th to 20th	Day	42% 4 9% 26% 17% 3	1857
	21st to end	Day	46% 5% 11% 22% 13% 4	1570
March	1st to 10th	Day	47% 5% 10% 25% 10% 2	3119
	11th to 20th	Day	31% 6% 13% 33% 15% 2	3288
	21st to end	Day	43% 4 8% 17% 23% 5%	4161
April	1st to 10th	Day	41% 5% 11% 21% 18% 5%	2280
	11th to 20th	Day	40% 5% 12% 24% 17% 3	2254
	21st to end	Day	41% 6% 10% 21% 19% 4	2317
May	1st to 10th	Day	55% 6% 12% 15% 11% 1	4120
	11th to 20th	Day	50% 5% 15% 20% 9% 1	4302
	21st to end	Day	37% 6% 12% 25% 17% 2	4837
June	1st to 10th	Day	40% 7% 13% 23% 15% 1	2660
	11th to 20th	Day	38% 8% 14% 25% 13% 2	2660
	21st to end	Day	34% 7% 16% 25% 16% 1	2660
July	1st to 10th	Day	44% 9% 11% 19% 17% 1	4370
	11th to 20th	Day	38% 8% 17% 23% 13% 1	4365
	21st to end	Day	44% 8% 13% 19% 15% 1	4661
August	1st to 10th	Day	43% 7% 17% 24% 9%	4134
	11th to 20th	Day	35% 6% 16% 33% 10% 1	3766
	21st to end	Day	30% 5% 14% 30% 20% 1	4180
September	1st to 10th	Day	35% 6% 13% 23% 20% 2	2280
	11th to 20th	Day	32% 5% 12% 27% 24% 2	2180
	21st to end	Day	44% 4 11% 19% 19% 2	2090
October	1st to 10th	Day	33% 4 13% 22% 23% 5%	3352
	11th to 20th	Day	24% 3 12% 24% 33% 5%	3140
	21st to end	Day	29% 3 15% 27% 23% 3	3149
November	1st to 10th	Day	35% 3 12% 26% 20% 3	1761
	11th to 20th	Day	38% 4 11% 24% 21% 2	1719
	21st to end	Day	38% 4 15% 30% 11% 2	1672
December	1st to 10th	Day	46% 3 16% 20% 14% 1	1520
	11th to 20th	Day	42% 3 14% 24% 16% 2	1906
	21st to end	Day	49% 6% 11% 24% 10%	2772
January	1st to 10th	Night	40% 3 10% 31% 12% 3	4429
	11th to 20th	Night	44% 4 12% 25% 13% 2	4440
	21st to end	Night	53% 3 7% 23% 12% 1	4660
February	1st to 10th	Night	44% 4 14% 24% 12% 2	2429
	11th to 20th	Night	45% 4 9% 20% 18% 4	2220
	21st to end	Night	45% 3 7% 24% 17% 4	1884
March	1st to 10th	Night	51% 4 8% 23% 11% 3	3734
	11th to 20th	Night	38% 5% 11% 26% 16% 3	3654
	21st to end	Night	47% 3 6% 16% 22% 6%	3470
April	1st to 10th	Night	46% 4 9% 20% 17% 4	1900
	11th to 20th	Night	44% 4 9% 20% 22% 1	1875
	21st to end	Night	43% 5% 8% 21% 18% 4	1862
May	1st to 10th	Night	55% 6% 11% 17% 10% 1	2840
	11th to 20th	Night	55% 5% 13% 16% 10% 1	2624
	21st to end	Night	42% 6% 12% 21% 16% 2	2739
June	1st to 10th	Night	43% 5% 10% 22% 19% 1	1520
	11th to 20th	Night	39% 6% 15% 27% 12% 1	1520
	21st to end	Night	38% 7% 13% 26% 14% 1	1520
July	1st to 10th	Night	47% 8% 13% 19% 12% 1	2480
	11th to 20th	Night	41% 7% 15% 26% 11% 1	2472
	21st to end	Night	47% 6% 14% 16% 16% 2	2651
August	1st to 10th	Night	51% 7% 17% 16% 8% 1	2734
	11th to 20th	Night	41% 6% 14% 28% 10% 1	3127
	21st to end	Night	30% 5% 12% 32% 20% 1	3476
September	1st to 10th	Night	40% 5% 11% 23% 19% 2	1900
	11th to 20th	Night	33% 5% 10% 25% 23% 3	2000
	21st to end	Night	44% 4 7% 22% 19% 2	2090
October	1st to 10th	Night	39% 4 11% 23% 20% 3	3605
	11th to 20th	Night	24% 3 11% 27% 31% 4	3779
	21st to end	Night	30% 3 12% 30% 22% 3	4398
November	1st to 10th	Night	35% 4 11% 25% 21% 4	2537
	11th to 20th	Night	41% 3 9% 23% 19% 4	2484
	21st to end	Night	37% 4 13% 29% 15% 2	2507
December	1st to 10th	Night	46% 4 14% 22% 13% 1	2660
	11th to 20th	Night	42% 4 13% 21% 18% 3	3288
	21st to end	Night	47% 5% 12% 23% 12% 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	15% 12% 41% 22% 9% 1	180
	11th to 20th	Day	14% 15% 48% 18% 4 1	180
	21st to end	Day	21% 7% 36% 25% 9% 2	261
February	1st to 10th	Day	24% 7% 34% 29% 6%	309
	11th to 20th	Day	19% 12% 39% 28% 3	456
	21st to end	Day	23% 11% 34% 27% 4 1	382
March	1st to 10th	Day	17% 10% 36% 30% 8%	460
	11th to 20th	Day	15% 6% 43% 28% 7% 2	460
	21st to end	Day	22% 6% 34% 28% 8% 1	506
April	1st to 10th	Day	21% 7% 32% 30% 9%	460
	11th to 20th	Day	19% 8% 23% 35% 12% 2	452
	21st to end	Day	21% 7% 28% 33% 10% 1	460
May	1st to 10th	Day	27% 5% 24% 32% 10% 2	463
	11th to 20th	Day	21% 2 21% 39% 15% 2	487
	21st to end	Day	18% 2 14% 31% 29% 6%	529
June	1st to 10th	Day	18% 2 17% 37% 23% 3	490
	11th to 20th	Day	13% 2 19% 38% 23% 4	490
	21st to end	Day	12% 2 15% 40% 28% 3	490
July	1st to 10th	Day	11% 3 9% 36% 32% 8%	485
	11th to 20th	Day	8% 2 9% 35% 36% 9%	484
	21st to end	Day	12% 2 11% 39% 31% 4	532
August	1st to 10th	Day	11% 1 8% 42% 31% 7%	486
	11th to 20th	Day	14% 2 9% 33% 36% 7%	479
	21st to end	Day	12% 1 13% 36% 29% 10%	539
September	1st to 10th	Day	16% 2 14% 32% 25% 10%	490
	11th to 20th	Day	13% 2 12% 33% 29% 10%	490
	21st to end	Day	24% 2 18% 33% 18% 5%	490
October	1st to 10th	Day	24% 3 16% 29% 22% 6%	490
	11th to 20th	Day	16% 5% 26% 29% 20% 4	490
	21st to end	Day	20% 7% 29% 26% 16% 3	452
November	1st to 10th	Day	14% 7% 25% 34% 16% 3	395
	11th to 20th	Day	17% 11% 36% 26% 9%	373
	21st to end	Day	18% 10% 32% 28% 11% 1	332
December	1st to 10th	Day	18% 8% 41% 22% 11%	180
	11th to 20th	Day	23% 17% 29% 26% 5% 1	180
	21st to end	Day	26% 9% 32% 21% 11% 1	198
January	1st to 10th	Night	19% 15% 42% 21% 4	760
	11th to 20th	Night	24% 13% 35% 24% 5%	760
	21st to end	Night	18% 14% 42% 22% 3	836
February	1st to 10th	Night	21% 13% 38% 26% 3	760
	11th to 20th	Night	22% 14% 42% 21% 1	743
	21st to end	Night	22% 12% 37% 24% 5%	628
March	1st to 10th	Night	20% 10% 40% 24% 6%	760
	11th to 20th	Night	19% 9% 38% 26% 6% 1	760
	21st to end	Night	20% 7% 36% 29% 7% 1	836
April	1st to 10th	Night	20% 6% 37% 29% 7% 1	760
	11th to 20th	Night	20% 6% 29% 36% 10%	751
	21st to end	Night	20% 4 30% 36% 10% 1	722
May	1st to 10th	Night	23% 5% 25% 32% 13% 2	570
	11th to 20th	Night	22% 3 27% 36% 12% 1	450
	21st to end	Night	19% 4 13% 34% 26% 6%	411
June	1st to 10th	Night	20% 3 15% 36% 23% 3	380
	11th to 20th	Night	15% 1 13% 43% 26% 2	380
	21st to end	Night	9% 2 16% 46% 26% 1	380
July	1st to 10th	Night	11% 4 12% 37% 32% 4	370
	11th to 20th	Night	10% 3 11% 37% 34% 6%	368
	21st to end	Night	11% 2 15% 39% 30% 3	416
August	1st to 10th	Night	11% 2 11% 41% 32% 3	512
	11th to 20th	Night	14% 2 12% 33% 34% 5%	750
	21st to end	Night	13% 2 12% 34% 32% 6%	836
September	1st to 10th	Night	17% 2 18% 32% 25% 6%	760
	11th to 20th	Night	16% 3 14% 34% 26% 7%	760
	21st to end	Night	22% 1 20% 33% 20% 4	760
October	1st to 10th	Night	23% 6% 23% 25% 19% 5%	760
	11th to 20th	Night	16% 8% 26% 34% 14% 2	760
	21st to end	Night	23% 6% 31% 27% 11% 1	836
November	1st to 10th	Night	14% 7% 33% 30% 13% 2	780
	11th to 20th	Night	21% 12% 32% 24% 11% 1	765
	21st to end	Night	15% 13% 37% 25% 9% 1	760
December	1st to 10th	Night	24% 13% 33% 22% 6% 1	760
	11th to 20th	Night	22% 11% 38% 25% 4	760
	21st to end	Night	22% 10% 40% 24% 4	836

Page generated at 2024-11-08 22:45:40. Version ac07

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