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 2024-01-14.

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	15% 6% 2 5% 5% 3 4 5% 6% 8% 42%	74778
	Night	17% 6% 3 5% 5% 3 4 4 5% 7% 42%	74969
Transparency	Day	40% 5% 13% 24% 16% 2	74483
	Night	42% 5% 11% 23% 16% 2	74798
Seeing	Day	18% 5% 24% 32% 18% 4	13925
	Night	19% 7% 29% 29% 14% 2	23170

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	14% 7% 3 4 5% 3 6% 4 6% 7% 43%	1517
	11th to 20th	Day	16% 8% 3 4 5% 4 5% 4 5% 9% 38%	1464
	21st to end	Day	15% 7% 2 5% 4 3 4 4 5% 8% 42%	1708
February	1st to 10th	Day	18% 8% 3 5% 4 3 4 4 5% 7% 39%	1657
	11th to 20th	Day	15% 7% 3 7% 5% 3 3 4 4 6% 44%	1748
	21st to end	Day	20% 7% 3 5% 5% 2 5% 4 5% 7% 38%	1480
March	1st to 10th	Day	14% 6% 3 5% 5% 2 4 4 5% 8% 46%	1797
	11th to 20th	Day	15% 6% 2 6% 4 3 4 5% 7% 8% 41%	1872
	21st to end	Day	19% 6% 3 6% 4 2 4 4 5% 5% 41%	2371
April	1st to 10th	Day	17% 7% 3 4 5% 2 4 4 5% 7% 42%	2160
	11th to 20th	Day	17% 5% 2 4 4 3 3 4 6% 7% 43%	2134
	21st to end	Day	18% 5% 2 4 4 3 5% 5% 6% 7% 40%	2195
May	1st to 10th	Day	22% 6% 3 4 4 3 5% 4 5% 7% 37%	2340
	11th to 20th	Day	19% 6% 2 4 4 3 4 5% 7% 8% 38%	2420
	21st to end	Day	15% 6% 2 4 4 3 4 5% 6% 10% 40%	2725
June	1st to 10th	Day	16% 6% 2 4 4 3 4 5% 7% 9% 38%	2520
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 5% 6% 9% 39%	2520
	21st to end	Day	10% 5% 2 4 5% 4 5% 5% 5% 10% 45%	2520
July	1st to 10th	Day	9% 5% 2 5% 6% 3 5% 6% 7% 10% 41%	2520
	11th to 20th	Day	9% 5% 2 4 5% 3 4 6% 8% 10% 44%	2520
	21st to end	Day	11% 5% 3 4 5% 3 6% 6% 7% 9% 41%	2744
August	1st to 10th	Day	9% 4 3 4 5% 3 4 5% 8% 10% 45%	2356
	11th to 20th	Day	12% 5% 2 4 4 3 5% 6% 6% 9% 45%	2126
	21st to end	Day	12% 5% 2 4 5% 3 4 6% 6% 8% 44%	2376
September	1st to 10th	Day	12% 6% 2 5% 5% 3 3 4 5% 9% 45%	2160
	11th to 20th	Day	12% 5% 2 4 4 2 3 3 4 8% 53%	2066
	21st to end	Day	17% 7% 2 5% 4 2 3 5% 6% 7% 42%	1980
October	1st to 10th	Day	20% 6% 2 5% 4 2 4 4 5% 6% 43%	1908
	11th to 20th	Day	16% 4 2 4 4 3 4 4 5% 8% 47%	1800
	21st to end	Day	18% 6% 2 5% 4 2 4 4 5% 7% 43%	1823
November	1st to 10th	Day	13% 6% 2 5% 4 2 3 4 4 5% 51%	1671
	11th to 20th	Day	17% 4 2 4 4 3 3 4 5% 6% 47%	1710
	21st to end	Day	15% 6% 2 3 4 3 4 4 5% 8% 46%	1672
December	1st to 10th	Day	18% 7% 3 5% 5% 2 5% 4 6% 7% 38%	1520
	11th to 20th	Day	20% 7% 3 4 4 2 3 3 4 6% 46%	1906
	21st to end	Day	18% 8% 3 5% 5% 4 6% 5% 4 7% 35%	2772
January	1st to 10th	Night	17% 7% 2 5% 4 2 3 4 5% 8% 43%	2649
	11th to 20th	Night	20% 7% 2 4 4 2 4 5% 5% 7% 39%	2569
	21st to end	Night	15% 7% 2 4 3 3 4 4 5% 7% 44%	2646
February	1st to 10th	Night	18% 8% 3 5% 5% 2 4 4 5% 7% 39%	2301
	11th to 20th	Night	19% 8% 2 5% 4 3 4 4 4 5% 41%	2098
	21st to end	Night	20% 6% 2 5% 4 2 4 4 4 5% 43%	1776
March	1st to 10th	Night	17% 6% 2 5% 4 2 3 3 4 7% 46%	2150
	11th to 20th	Night	18% 7% 2 4 4 3 5% 4 5% 7% 41%	2083
	21st to end	Night	19% 7% 3 5% 4 2 4 5% 4 6% 42%	1984
April	1st to 10th	Night	17% 7% 4 6% 4 3 4 4 5% 7% 39%	1800
	11th to 20th	Night	18% 7% 2 6% 5% 2 4 4 5% 7% 41%	1775
	21st to end	Night	18% 7% 4 6% 4 3 4 4 4 7% 40%	1764
May	1st to 10th	Night	21% 10% 3 6% 5% 3 5% 4 4 7% 34%	1620
	11th to 20th	Night	19% 8% 3 5% 5% 3 4 4 5% 6% 37%	1487
	21st to end	Night	16% 8% 2 5% 6% 2 4 5% 5% 8% 38%	1550
June	1st to 10th	Night	18% 6% 3 4 4 3 3 5% 6% 8% 39%	1440
	11th to 20th	Night	14% 5% 4 6% 4 2 5% 5% 7% 9% 39%	1440
	21st to end	Night	9% 6% 2 6% 6% 4 5% 6% 5% 10% 42%	1440
July	1st to 10th	Night	11% 7% 3 5% 6% 3 5% 6% 6% 9% 39%	1440
	11th to 20th	Night	10% 6% 2 5% 6% 4 5% 6% 6% 8% 41%	1440
	21st to end	Night	9% 5% 4 5% 6% 3 6% 6% 7% 10% 41%	1574
August	1st to 10th	Night	8% 5% 3 5% 6% 4 4 7% 6% 9% 42%	1558
	11th to 20th	Night	12% 5% 2 6% 5% 4 5% 6% 7% 9% 38%	1774
	21st to end	Night	13% 5% 3 5% 5% 3 4 6% 5% 8% 43%	1980
September	1st to 10th	Night	15% 5% 2 5% 5% 3 5% 5% 5% 7% 42%	1800
	11th to 20th	Night	13% 6% 2 4 4 2 3 4 4 5% 53%	1894
	21st to end	Night	17% 6% 3 6% 4 3 3 4 5% 7% 43%	1980
October	1st to 10th	Night	21% 6% 2 5% 5% 3 4 4 4 5% 42%	2049
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 5% 7% 48%	2160
	21st to end	Night	22% 6% 3 5% 4 3 3 4 4 6% 42%	2532
November	1st to 10th	Night	13% 5% 2 5% 5% 3 4 3 4 6% 50%	2407
	11th to 20th	Night	19% 5% 2 5% 4 2 3 4 4 5% 48%	2470
	21st to end	Night	14% 5% 2 5% 4 3 4 4 5% 7% 47%	2507
December	1st to 10th	Night	21% 7% 2 5% 4 2 4 4 5% 6% 39%	2660
	11th to 20th	Night	19% 6% 2 4 4 2 4 5% 5% 6% 43%	3288
	21st to end	Night	19% 8% 3 5% 5% 3 4 4 5% 6% 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	42% 3 12% 27% 14% 3	1518
	11th to 20th	Day	43% 5% 14% 24% 13% 2	1464
	21st to end	Day	42% 3 12% 28% 13% 3	1708
February	1st to 10th	Day	46% 4 13% 24% 13% 1	1657
	11th to 20th	Day	43% 4 9% 26% 16% 3	1757
	21st to end	Day	46% 4 10% 23% 14% 4	1480
March	1st to 10th	Day	37% 5% 14% 25% 15% 3	1800
	11th to 20th	Day	39% 5% 12% 26% 16% 2	1872
	21st to end	Day	45% 4 9% 20% 18% 4	2371
April	1st to 10th	Day	41% 5% 11% 21% 18% 5%	2160
	11th to 20th	Day	39% 5% 11% 25% 17% 3	2134
	21st to end	Day	42% 5% 10% 21% 18% 4	2195
May	1st to 10th	Day	47% 5% 10% 20% 15% 2	2340
	11th to 20th	Day	43% 5% 12% 22% 16% 2	2424
	21st to end	Day	40% 6% 18% 22% 13% 2	2725
June	1st to 10th	Day	41% 6% 14% 23% 15% 1	2520
	11th to 20th	Day	40% 8% 13% 24% 13% 2	2520
	21st to end	Day	34% 8% 16% 26% 16% 1	2520
July	1st to 10th	Day	37% 8% 14% 23% 17% 1	2450
	11th to 20th	Day	33% 7% 16% 28% 14% 2	2445
	21st to end	Day	36% 8% 12% 25% 17% 2	2591
August	1st to 10th	Day	31% 8% 17% 28% 14% 1	2342
	11th to 20th	Day	34% 8% 16% 26% 15% 2	2126
	21st to end	Day	36% 6% 14% 22% 20% 2	2376
September	1st to 10th	Day	36% 6% 14% 23% 19% 2	2160
	11th to 20th	Day	32% 5% 12% 26% 24% 2	2066
	21st to end	Day	42% 4 11% 20% 20% 2	1980
October	1st to 10th	Day	42% 5% 11% 23% 17% 2	1908
	11th to 20th	Day	36% 4 11% 27% 20% 1	1800
	21st to end	Day	42% 4 10% 24% 18% 3	1823
November	1st to 10th	Day	36% 4 12% 26% 19% 2	1671
	11th to 20th	Day	38% 4 11% 24% 21% 2	1710
	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	42% 3 11% 25% 16% 3	2649
	11th to 20th	Night	45% 5% 15% 24% 10% 2	2569
	21st to end	Night	41% 3 9% 26% 19% 2	2646
February	1st to 10th	Night	45% 4 14% 23% 11% 2	2301
	11th to 20th	Night	46% 4 9% 20% 16% 4	2100
	21st to end	Night	45% 3 7% 25% 17% 3	1776
March	1st to 10th	Night	40% 4 12% 25% 15% 4	2160
	11th to 20th	Night	43% 4 9% 23% 17% 5%	2084
	21st to end	Night	44% 4 8% 19% 19% 6%	1984
April	1st to 10th	Night	45% 4 9% 21% 17% 4	1800
	11th to 20th	Night	44% 4 9% 20% 22% 1	1775
	21st to end	Night	45% 5% 8% 20% 18% 5%	1764
May	1st to 10th	Night	50% 6% 9% 19% 14% 2	1620
	11th to 20th	Night	49% 5% 9% 17% 17% 3	1488
	21st to end	Night	44% 7% 14% 20% 13% 2	1551
June	1st to 10th	Night	44% 5% 10% 22% 18% 1	1440
	11th to 20th	Night	41% 6% 15% 26% 12% 1	1440
	21st to end	Night	37% 7% 13% 26% 15% 2	1440
July	1st to 10th	Night	42% 8% 13% 22% 14% 2	1400
	11th to 20th	Night	38% 7% 12% 28% 14% 2	1392
	21st to end	Night	35% 8% 15% 25% 15% 3	1486
August	1st to 10th	Night	35% 9% 18% 23% 14% 2	1548
	11th to 20th	Night	40% 7% 15% 26% 11% 1	1774
	21st to end	Night	38% 7% 14% 21% 18% 2	1980
September	1st to 10th	Night	41% 5% 12% 23% 17% 2	1800
	11th to 20th	Night	33% 5% 10% 25% 24% 3	1894
	21st to end	Night	43% 5% 7% 23% 20% 2	1980
October	1st to 10th	Night	46% 5% 10% 21% 15% 2	2049
	11th to 20th	Night	36% 4 14% 28% 17% 2	2160
	21st to end	Night	46% 3 10% 22% 17% 1	2532
November	1st to 10th	Night	37% 4 11% 24% 20% 4	2407
	11th to 20th	Night	41% 3 9% 23% 19% 4	2470
	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	13% 14% 48% 19% 4 1	166
	21st to end	Day	20% 7% 38% 25% 7% 2	232
February	1st to 10th	Day	26% 8% 34% 27% 4	277
	11th to 20th	Day	20% 11% 38% 28% 2	416
	21st to end	Day	24% 12% 34% 27% 4	346
March	1st to 10th	Day	14% 10% 39% 31% 7%	420
	11th to 20th	Day	17% 5% 42% 29% 5% 2	420
	21st to end	Day	23% 6% 34% 28% 8% 2	462
April	1st to 10th	Day	20% 8% 31% 31% 9%	420
	11th to 20th	Day	19% 7% 23% 36% 13% 2	412
	21st to end	Day	23% 6% 29% 32% 9% 1	420
May	1st to 10th	Day	28% 4 24% 31% 10% 2	423
	11th to 20th	Day	20% 2 21% 40% 14% 2	447
	21st to end	Day	19% 2 14% 29% 30% 6%	485
June	1st to 10th	Day	19% 2 17% 35% 24% 3	450
	11th to 20th	Day	14% 2 20% 39% 21% 4	450
	21st to end	Day	12% 2 15% 40% 28% 3	450
July	1st to 10th	Day	12% 3 9% 36% 32% 8%	445
	11th to 20th	Day	8% 2 9% 34% 37% 10%	444
	21st to end	Day	12% 2 12% 39% 31% 5%	488
August	1st to 10th	Day	10% 1 7% 42% 32% 7%	446
	11th to 20th	Day	14% 1 9% 33% 36% 6%	439
	21st to end	Day	13% 1 13% 35% 28% 10%	495
September	1st to 10th	Day	16% 2 15% 32% 25% 10%	450
	11th to 20th	Day	14% 2 14% 34% 27% 9%	450
	21st to end	Day	22% 2 19% 34% 18% 5%	450
October	1st to 10th	Day	25% 3 17% 28% 22% 5%	450
	11th to 20th	Day	17% 5% 25% 29% 20% 3	450
	21st to end	Day	21% 7% 31% 25% 14% 2	417
November	1st to 10th	Day	15% 8% 26% 32% 17% 3	365
	11th to 20th	Day	17% 11% 36% 26% 9%	370
	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% 11% 36% 24% 5%	735
	21st to end	Night	18% 14% 43% 22% 3	792
February	1st to 10th	Night	22% 13% 38% 25% 3	720
	11th to 20th	Night	22% 14% 42% 21% 2	703
	21st to end	Night	22% 12% 38% 24% 4	592
March	1st to 10th	Night	20% 10% 40% 23% 6%	720
	11th to 20th	Night	20% 8% 38% 27% 6% 1	720
	21st to end	Night	20% 6% 36% 30% 7% 1	792
April	1st to 10th	Night	20% 6% 37% 29% 7% 1	720
	11th to 20th	Night	20% 5% 28% 37% 10%	711
	21st to end	Night	20% 5% 30% 35% 10% 1	684
May	1st to 10th	Night	23% 5% 25% 31% 13% 2	540
	11th to 20th	Night	22% 3 27% 36% 12% 1	426
	21st to end	Night	19% 3 13% 33% 26% 6%	389
June	1st to 10th	Night	21% 3 15% 35% 23% 3	360
	11th to 20th	Night	16% 1 14% 43% 24% 2	360
	21st to end	Night	8% 2 14% 47% 27% 1	360
July	1st to 10th	Night	12% 4 13% 37% 31% 4	350
	11th to 20th	Night	10% 3 10% 36% 34% 6%	348
	21st to end	Night	10% 2 15% 39% 30% 4	394
August	1st to 10th	Night	10% 1 12% 42% 33% 3	484
	11th to 20th	Night	14% 2 12% 33% 35% 5%	710
	21st to end	Night	14% 2 12% 35% 31% 6%	792
September	1st to 10th	Night	18% 2 18% 32% 25% 6%	720
	11th to 20th	Night	17% 3 15% 35% 25% 7%	720
	21st to end	Night	22% 1 20% 33% 20% 4	720
October	1st to 10th	Night	23% 6% 23% 25% 19% 5%	720
	11th to 20th	Night	17% 8% 25% 34% 15% 1	720
	21st to end	Night	24% 7% 32% 26% 10% 1	792
November	1st to 10th	Night	15% 7% 33% 29% 13% 2	740
	11th to 20th	Night	20% 12% 32% 24% 11% 1	760
	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 2024-01-11 04:22:39. Version ac07

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