Comprix Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Comprix Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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% 10% 3 7% 5% 5% 5% 4 5% 7% 34%	101303
	Night	16% 10% 3 7% 5% 4 4 3 5% 6% 36%	97576
Transparency	Day	50% 4 11% 22% 12% 2	101115
	Night	49% 4 10% 23% 13% 2	97433
Seeing	Day	19% 8% 24% 24% 17% 8%	14973
	Night	19% 7% 25% 33% 16% 2	24899

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	19% 19% 6% 12% 5% 4 4 3 5% 5% 18%	2836
	11th to 20th	Day	16% 20% 6% 12% 7% 9% 5% 2 3 4 16%	2840
	21st to end	Day	27% 20% 8% 8% 6% 5% 3 2 3 4 12%	3124
February	1st to 10th	Day	22% 13% 4 10% 6% 4 4 3 4 5% 24%	1710
	11th to 20th	Day	17% 12% 5% 13% 6% 4 4 4 5% 6% 25%	1825
	21st to end	Day	20% 14% 5% 8% 4 4 4 2 4 5% 30%	1570
March	1st to 10th	Day	23% 16% 5% 9% 5% 3 4 3 4 6% 23%	3272
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 4 4 6% 38%	3480
	21st to end	Day	21% 8% 3 8% 5% 4 4 3 4 7% 33%	3815
April	1st to 10th	Day	15% 13% 3 7% 5% 4 5% 3 5% 6% 34%	2128
	11th to 20th	Day	18% 9% 3 7% 4 4 4 4 5% 6% 37%	2399
	21st to end	Day	18% 8% 3 7% 6% 5% 5% 4 6% 7% 33%	2470
May	1st to 10th	Day	22% 9% 3 7% 5% 5% 4 4 5% 7% 30%	4082
	11th to 20th	Day	22% 7% 3 6% 4 4 4 3 5% 7% 34%	4081
	21st to end	Day	12% 5% 2 7% 5% 5% 6% 5% 7% 10% 35%	4476
June	1st to 10th	Day	12% 6% 3 6% 5% 5% 5% 4 6% 9% 37%	2470
	11th to 20th	Day	12% 5% 2 8% 5% 4 4 5% 7% 9% 39%	2470
	21st to end	Day	11% 5% 2 6% 6% 5% 5% 5% 6% 11% 37%	2577
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	4158
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 5% 7% 10% 45%	4120
	21st to end	Day	11% 7% 2 6% 5% 5% 6% 5% 7% 9% 36%	4466
August	1st to 10th	Day	10% 5% 2 7% 5% 5% 5% 5% 7% 10% 39%	4104
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 10% 40%	4044
	21st to end	Day	6% 5% 1 5% 4 6% 6% 4 6% 9% 48%	4453
September	1st to 10th	Day	14% 5% 2 4 4 3 4 3 6% 6% 50%	2091
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 3 5% 7% 48%	2090
	21st to end	Day	19% 7% 2 6% 4 3 4 3 5% 5% 43%	2090
October	1st to 10th	Day	13% 6% 2 6% 4 5% 4 3 5% 8% 45%	2033
	11th to 20th	Day	14% 7% 2 6% 4 5% 4 4 5% 6% 43%	1900
	21st to end	Day	21% 8% 2 8% 4 4 3 3 5% 5% 36%	2041
November	1st to 10th	Day	10% 8% 2 6% 4 4 3 3 5% 6% 48%	1681
	11th to 20th	Day	16% 12% 3 6% 6% 5% 4 3 4 5% 34%	1710
	21st to end	Day	19% 11% 4 7% 5% 4 5% 4 4 6% 31%	1710
December	1st to 10th	Day	21% 17% 5% 11% 5% 4 5% 3 5% 5% 19%	1710
	11th to 20th	Day	19% 17% 5% 10% 5% 3 4 3 5% 5% 23%	2153
	21st to end	Day	24% 22% 6% 10% 5% 5% 4 4 4 5% 12%	3124
January	1st to 10th	Night	17% 18% 7% 13% 6% 5% 4 3 4 5% 19%	4109
	11th to 20th	Night	16% 17% 6% 15% 6% 6% 5% 3 4 5% 18%	4120
	21st to end	Night	27% 17% 8% 9% 6% 3 4 2 3 3 17%	4532
February	1st to 10th	Night	21% 13% 3 9% 6% 4 4 3 4 4 29%	2470
	11th to 20th	Night	19% 12% 3 9% 6% 5% 5% 3 5% 6% 27%	2237
	21st to end	Night	21% 13% 6% 9% 5% 4 3 3 4 5% 27%	1884
March	1st to 10th	Night	22% 12% 4 6% 4 3 3 3 4 6% 34%	3580
	11th to 20th	Night	14% 8% 2 5% 5% 4 4 4 5% 7% 40%	3480
	21st to end	Night	21% 8% 3 6% 4 3 4 3 4 5% 40%	3817
April	1st to 10th	Night	16% 9% 3 5% 5% 4 4 4 5% 6% 38%	2068
	11th to 20th	Night	15% 8% 2 7% 4 5% 4 4 6% 7% 38%	1730
	21st to end	Night	15% 8% 3 7% 5% 5% 4 3 6% 8% 37%	1710
May	1st to 10th	Night	28% 8% 3 7% 5% 3 5% 4 5% 6% 26%	2813
	11th to 20th	Night	19% 7% 2 5% 4 4 4 3 5% 8% 40%	2812
	21st to end	Night	11% 5% 2 6% 4 4 4 5% 6% 8% 45%	3079
June	1st to 10th	Night	9% 5% 3 5% 4 5% 5% 3 6% 8% 46%	1710
	11th to 20th	Night	8% 5% 2 5% 3 5% 6% 4 8% 11% 44%	1710
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 8% 10% 44%	1580
July	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 5% 7% 46%	2768
	11th to 20th	Night	9% 5% 1 5% 5% 4 4 5% 6% 8% 48%	2840
	21st to end	Night	9% 6% 3 7% 5% 5% 5% 5% 7% 7% 40%	3087
August	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 10% 37%	2825
	11th to 20th	Night	10% 7% 3 7% 5% 5% 4 2 6% 7% 44%	2785
	21st to end	Night	5% 3 2 6% 4 4 5% 4 6% 9% 51%	3186
September	1st to 10th	Night	14% 4 1 4 3 4 4 3 4 6% 53%	2068
	11th to 20th	Night	9% 4 1 5% 3 3 4 4 5% 7% 55%	2090
	21st to end	Night	16% 7% 2 6% 3 3 4 3 4 6% 47%	2090
October	1st to 10th	Night	10% 4 2 5% 4 4 4 4 5% 7% 50%	2146
	11th to 20th	Night	16% 8% 2 5% 3 3 4 3 5% 6% 45%	2280
	21st to end	Night	21% 7% 2 6% 4 3 4 3 5% 5% 39%	2555
November	1st to 10th	Night	14% 6% 2 6% 3 3 3 3 4 6% 49%	2431
	11th to 20th	Night	17% 10% 3 6% 6% 4 4 4 5% 6% 36%	2470
	21st to end	Night	20% 12% 3 7% 5% 4 4 3 6% 6% 30%	2470
December	1st to 10th	Night	22% 15% 5% 9% 5% 4 4 3 5% 5% 24%	2470
	11th to 20th	Night	18% 15% 6% 8% 5% 4 4 3 5% 6% 27%	3042
	21st to end	Night	25% 20% 5% 9% 5% 5% 3 3 4 5% 16%	4532

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	70% 3 9% 13% 5%	2837
	11th to 20th	Day	74% 3 10% 10% 3	2840
	21st to end	Day	78% 2 8% 8% 3	3124
February	1st to 10th	Day	63% 3 10% 15% 8%	1710
	11th to 20th	Day	61% 4 9% 18% 9%	1835
	21st to end	Day	59% 2 11% 19% 8% 1	1570
March	1st to 10th	Day	64% 2 9% 21% 4 1	3272
	11th to 20th	Day	49% 3 10% 28% 10% 1	3480
	21st to end	Day	53% 3 10% 24% 10%	3815
April	1st to 10th	Day	52% 3 11% 20% 12% 2	2128
	11th to 20th	Day	48% 4 11% 21% 14% 3	2399
	21st to end	Day	50% 5% 10% 21% 11% 2	2470
May	1st to 10th	Day	55% 3 11% 24% 7% 1	4120
	11th to 20th	Day	50% 4 12% 21% 12% 1	4085
	21st to end	Day	43% 5% 13% 22% 13% 3	4489
June	1st to 10th	Day	43% 5% 11% 25% 15% 2	2470
	11th to 20th	Day	40% 5% 16% 24% 15% 1	2470
	21st to end	Day	40% 5% 16% 21% 15% 3	2577
July	1st to 10th	Day	42% 4 12% 23% 16% 3	4093
	11th to 20th	Day	34% 4 11% 31% 19% 1	4051
	21st to end	Day	43% 4 13% 19% 18% 4	4324
August	1st to 10th	Day	40% 4 15% 29% 11% 1	4091
	11th to 20th	Day	38% 4 11% 31% 16% 1	4083
	21st to end	Day	32% 4 14% 32% 14% 3	4452
September	1st to 10th	Day	34% 5% 10% 24% 23% 4	2091
	11th to 20th	Day	35% 4 10% 27% 21% 3	2090
	21st to end	Day	44% 4 8% 23% 21% 1	2090
October	1st to 10th	Day	39% 4 9% 27% 20% 1	2033
	11th to 20th	Day	41% 4 10% 25% 18% 2	1900
	21st to end	Day	50% 3 11% 23% 11% 2	2041
November	1st to 10th	Day	37% 4 10% 27% 19% 3	1681
	11th to 20th	Day	52% 3 8% 22% 12% 3	1710
	21st to end	Day	55% 3 12% 20% 10% 1	1710
December	1st to 10th	Day	67% 3 10% 17% 3	1710
	11th to 20th	Day	63% 3 9% 18% 6%	2150
	21st to end	Day	77% 3 9% 8% 3	3124
January	1st to 10th	Night	68% 2 10% 15% 5%	4109
	11th to 20th	Night	70% 2 10% 14% 3	4120
	21st to end	Night	74% 2 8% 12% 3 1	4532
February	1st to 10th	Night	59% 4 9% 18% 8% 1	2470
	11th to 20th	Night	57% 3 10% 19% 10% 1	2238
	21st to end	Night	61% 2 10% 16% 8% 2	1884
March	1st to 10th	Night	53% 3 8% 26% 10% 1	3580
	11th to 20th	Night	43% 3 10% 31% 10% 1	3480
	21st to end	Night	47% 3 7% 29% 12% 1	3817
April	1st to 10th	Night	46% 4 11% 22% 14% 2	2068
	11th to 20th	Night	45% 4 11% 18% 18% 4	1730
	21st to end	Night	45% 4 11% 23% 15% 2	1710
May	1st to 10th	Night	58% 4 9% 20% 7% 1	2840
	11th to 20th	Night	44% 5% 12% 28% 10% 2	2813
	21st to end	Night	34% 6% 14% 30% 13% 3	3087
June	1st to 10th	Night	35% 6% 12% 24% 19% 3	1710
	11th to 20th	Night	32% 6% 15% 25% 17% 3	1710
	21st to end	Night	33% 7% 15% 24% 18% 3	1580
July	1st to 10th	Night	39% 3 11% 23% 18% 5%	2723
	11th to 20th	Night	34% 4 12% 31% 18% 1	2786
	21st to end	Night	41% 4 13% 21% 15% 5%	2988
August	1st to 10th	Night	42% 4 15% 26% 12% 1	2814
	11th to 20th	Night	40% 4 9% 27% 20% 1	2812
	21st to end	Night	29% 4 15% 30% 19% 3	3186
September	1st to 10th	Night	33% 4 12% 23% 21% 6%	2068
	11th to 20th	Night	29% 4 10% 27% 27% 4	2090
	21st to end	Night	40% 3 10% 21% 25% 1	2090
October	1st to 10th	Night	34% 5% 9% 28% 22% 2	2146
	11th to 20th	Night	40% 4 9% 26% 19% 2	2280
	21st to end	Night	47% 4 7% 24% 15% 2	2555
November	1st to 10th	Night	38% 3 11% 26% 20% 3	2431
	11th to 20th	Night	49% 3 8% 23% 15% 2	2470
	21st to end	Night	55% 2 12% 21% 9% 1	2470
December	1st to 10th	Night	63% 3 9% 19% 6%	2470
	11th to 20th	Night	59% 3 11% 21% 6%	3044
	21st to end	Night	73% 2 9% 13% 3	4532

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	26% 14% 34% 18% 5% 2	270
	11th to 20th	Day	26% 19% 36% 14% 4	270
	21st to end	Day	32% 14% 33% 15% 6%	297
February	1st to 10th	Day	30% 15% 32% 16% 6%	270
	11th to 20th	Day	27% 18% 36% 14% 3 1	270
	21st to end	Day	25% 17% 40% 16% 2	225
March	1st to 10th	Day	24% 16% 32% 22% 6%	357
	11th to 20th	Day	26% 13% 31% 23% 7% 1	460
	21st to end	Day	28% 12% 32% 21% 6%	506
April	1st to 10th	Day	23% 12% 31% 21% 11% 3	460
	11th to 20th	Day	21% 14% 28% 22% 10% 5%	452
	21st to end	Day	20% 10% 33% 25% 10% 2	460
May	1st to 10th	Day	26% 9% 27% 21% 13% 4	463
	11th to 20th	Day	21% 6% 24% 24% 19% 7%	487
	21st to end	Day	12% 6% 21% 28% 23% 11%	529
June	1st to 10th	Day	14% 4 20% 31% 21% 10%	490
	11th to 20th	Day	14% 4 17% 28% 27% 10%	490
	21st to end	Day	12% 5% 23% 28% 22% 9%	597
July	1st to 10th	Day	15% 4 10% 23% 24% 24%	510
	11th to 20th	Day	10% 3 16% 25% 29% 17%	484
	21st to end	Day	12% 2 10% 28% 30% 17%	532
August	1st to 10th	Day	11% 3 12% 22% 34% 19%	486
	11th to 20th	Day	14% 3 16% 29% 24% 15%	479
	21st to end	Day	8% 1 10% 28% 32% 21%	539
September	1st to 10th	Day	14% 3 12% 25% 29% 18%	490
	11th to 20th	Day	10% 2 9% 23% 36% 19%	490
	21st to end	Day	22% 7% 14% 27% 22% 10%	490
October	1st to 10th	Day	12% 5% 22% 30% 20% 11%	490
	11th to 20th	Day	14% 10% 29% 28% 15% 4	490
	21st to end	Day	22% 9% 31% 25% 12% 1	490
November	1st to 10th	Day	14% 11% 29% 28% 14% 4	273
	11th to 20th	Day	21% 19% 26% 19% 13% 2	270
	21st to end	Day	26% 10% 34% 23% 5% 1	270
December	1st to 10th	Day	27% 12% 32% 20% 7% 2	270
	11th to 20th	Day	23% 14% 39% 18% 6%	270
	21st to end	Day	31% 14% 29% 21% 5%	297
January	1st to 10th	Night	24% 13% 33% 25% 5%	760
	11th to 20th	Night	28% 11% 32% 23% 4	760
	21st to end	Night	26% 10% 32% 28% 4	836
February	1st to 10th	Night	28% 9% 29% 31% 3	760
	11th to 20th	Night	25% 10% 35% 27% 3	743
	21st to end	Night	25% 11% 37% 24% 2	628
March	1st to 10th	Night	22% 10% 32% 30% 6%	760
	11th to 20th	Night	21% 11% 34% 27% 7%	760
	21st to end	Night	25% 9% 30% 27% 8% 1	836
April	1st to 10th	Night	20% 9% 35% 28% 7%	738
	11th to 20th	Night	18% 7% 35% 28% 12% 1	563
	21st to end	Night	18% 6% 39% 30% 7% 1	570
May	1st to 10th	Night	19% 7% 29% 30% 14%	570
	11th to 20th	Night	20% 4 21% 37% 17% 1	561
	21st to end	Night	8% 4 17% 39% 29% 3	617
June	1st to 10th	Night	10% 4 19% 43% 23% 1	570
	11th to 20th	Night	11% 2 17% 42% 26% 2	570
	21st to end	Night	10% 3 17% 43% 25% 2	570
July	1st to 10th	Night	11% 3 10% 41% 29% 7%	555
	11th to 20th	Night	7% 2 10% 39% 36% 6%	552
	21st to end	Night	10% 2 9% 40% 36% 2	624
August	1st to 10th	Night	7% 1 9% 42% 36% 4	567
	11th to 20th	Night	11% 2 9% 41% 34% 4	564
	21st to end	Night	8% 1 9% 37% 37% 7%	627
September	1st to 10th	Night	16% 2 12% 33% 32% 5%	738
	11th to 20th	Night	10% 2 11% 37% 35% 6%	760
	21st to end	Night	19% 3 18% 34% 24% 2	760
October	1st to 10th	Night	11% 3 21% 38% 24% 3	760
	11th to 20th	Night	19% 6% 27% 33% 14% 1	760
	21st to end	Night	24% 7% 27% 32% 10%	836
November	1st to 10th	Night	18% 5% 25% 34% 17% 1	748
	11th to 20th	Night	21% 11% 29% 29% 10% 1	760
	21st to end	Night	25% 9% 27% 31% 8% 1	760
December	1st to 10th	Night	29% 8% 29% 29% 5%	760
	11th to 20th	Night	24% 8% 32% 29% 5% 1	760
	21st to end	Night	31% 10% 27% 28% 3	836

Page generated at 2024-10-30 13:19:25. Version ac07

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