C-Murrinsville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the C-Murrinsville clear sky chart from 2005-11-06 to 2025-03-12.

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% 12% 4 9% 5% 5% 4 4 5% 7% 29%	108896
	Night	16% 12% 5% 10% 5% 4 4 3 5% 6% 29%	110097
Transparency	Day	54% 5% 11% 19% 10% 1	112541
	Night	55% 5% 11% 18% 10% 1	114592
Seeing	Day	24% 16% 28% 19% 10% 4	14996
	Night	23% 14% 27% 24% 11% 1	24761

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% 21% 8% 23% 6% 4 3 2 3 4 12%	3901
	11th to 20th	Day	10% 22% 11% 20% 8% 7% 3 2 2 3 12%	4060
	21st to end	Day	19% 19% 8% 13% 8% 5% 4 3 3 4 14%	4466
February	1st to 10th	Day	17% 20% 5% 13% 8% 5% 3 3 3 4 20%	1800
	11th to 20th	Day	16% 14% 6% 15% 7% 5% 4 3 5% 5% 19%	1753
	21st to end	Day	19% 16% 4 11% 5% 4 5% 3 4 6% 23%	1628
March	1st to 10th	Day	20% 11% 6% 10% 5% 3 4 4 5% 6% 27%	3545
	11th to 20th	Day	12% 13% 5% 11% 7% 5% 4 3 4 5% 31%	3491
	21st to end	Day	20% 12% 3 7% 5% 4 3 3 5% 7% 31%	3815
April	1st to 10th	Day	15% 16% 3 8% 5% 4 4 4 5% 7% 30%	2204
	11th to 20th	Day	19% 12% 3 7% 5% 4 4 3 5% 5% 33%	2289
	21st to end	Day	21% 11% 3 6% 4 3 4 3 5% 6% 32%	2470
May	1st to 10th	Day	23% 10% 3 8% 5% 5% 4 3 5% 6% 28%	4082
	11th to 20th	Day	19% 10% 3 7% 5% 5% 5% 4 7% 7% 28%	4099
	21st to end	Day	12% 7% 3 6% 5% 5% 5% 5% 7% 8% 39%	4823
June	1st to 10th	Day	15% 8% 3 7% 6% 6% 5% 4 7% 8% 32%	2660
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 4 5% 9% 34%	2660
	21st to end	Day	15% 5% 2 6% 5% 5% 5% 4 7% 9% 37%	2660
July	1st to 10th	Day	9% 6% 2 7% 5% 6% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 10% 40%	4120
	21st to end	Day	11% 6% 2 7% 6% 6% 6% 4 6% 9% 37%	4466
August	1st to 10th	Day	17% 9% 3 8% 5% 5% 5% 4 6% 8% 30%	4104
	11th to 20th	Day	13% 7% 3 8% 5% 6% 6% 5% 8% 8% 32%	4044
	21st to end	Day	10% 6% 2 7% 5% 6% 6% 5% 7% 9% 38%	4317
September	1st to 10th	Day	15% 8% 3 5% 4 4 4 3 5% 7% 43%	2280
	11th to 20th	Day	12% 7% 3 6% 4 4 4 4 5% 8% 42%	2118
	21st to end	Day	20% 8% 3 7% 5% 4 5% 3 5% 7% 34%	2077
October	1st to 10th	Day	17% 8% 3 7% 5% 4 4 4 6% 8% 36%	1900
	11th to 20th	Day	20% 9% 2 8% 5% 6% 5% 3 5% 5% 32%	1900
	21st to end	Day	24% 10% 3 8% 4 4 4 3 5% 7% 29%	2090
November	1st to 10th	Day	12% 9% 3 8% 6% 5% 4 4 5% 6% 39%	1867
	11th to 20th	Day	17% 15% 4 7% 5% 5% 4 4 5% 5% 29%	1617
	21st to end	Day	18% 19% 6% 10% 5% 4 4 3 4 5% 20%	1600
December	1st to 10th	Day	19% 18% 9% 21% 5% 3 3 2 3 3 12%	2600
	11th to 20th	Day	22% 20% 6% 11% 5% 3 3 2 4 5% 20%	2990
	21st to end	Day	22% 25% 6% 12% 5% 4 3 3 3 4 13%	3960
January	1st to 10th	Night	14% 19% 9% 25% 5% 4 3 3 3 4 11%	6027
	11th to 20th	Night	12% 18% 9% 20% 9% 6% 5% 3 4 4 11%	5900
	21st to end	Night	20% 17% 7% 14% 7% 5% 5% 2 3 4 15%	6490
February	1st to 10th	Night	17% 16% 5% 13% 8% 6% 3 3 4 4 21%	2600
	11th to 20th	Night	18% 13% 4 13% 6% 6% 5% 4 4 5% 20%	2533
	21st to end	Night	20% 13% 5% 12% 6% 4 3 4 4 5% 23%	1995
March	1st to 10th	Night	21% 14% 4 7% 5% 4 3 3 4 5% 31%	3528
	11th to 20th	Night	17% 13% 7% 8% 5% 3 4 3 4 6% 31%	3498
	21st to end	Night	17% 11% 4 8% 5% 3 4 3 4 5% 37%	3817
April	1st to 10th	Night	17% 16% 3 7% 5% 4 3 3 5% 7% 30%	1974
	11th to 20th	Night	18% 10% 3 6% 4 4 5% 3 5% 6% 35%	1856
	21st to end	Night	15% 11% 4 7% 5% 4 4 3 5% 7% 35%	1710
May	1st to 10th	Night	26% 10% 3 7% 4 4 4 3 5% 6% 29%	2813
	11th to 20th	Night	17% 10% 4 7% 4 4 5% 4 5% 7% 34%	2790
	21st to end	Night	12% 6% 2 6% 3 4 4 4 6% 10% 43%	2732
June	1st to 10th	Night	9% 5% 2 6% 5% 5% 5% 5% 6% 8% 43%	1520
	11th to 20th	Night	11% 5% 3 7% 4 5% 5% 4 7% 8% 42%	1520
	21st to end	Night	11% 6% 3 6% 5% 3 6% 3 6% 9% 42%	1520
July	1st to 10th	Night	11% 8% 3 7% 5% 5% 4 4 5% 8% 40%	2520
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 6% 9% 45%	2835
	21st to end	Night	10% 7% 3 7% 4 4 5% 4 6% 7% 43%	3087
August	1st to 10th	Night	14% 9% 3 7% 5% 4 4 4 5% 6% 37%	2825
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 3 5% 6% 42%	2785
	21st to end	Night	8% 6% 2 6% 4 4 6% 5% 7% 9% 44%	3306
September	1st to 10th	Night	13% 5% 2 5% 5% 3 3 3 6% 6% 48%	1900
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 6% 8% 52%	2059
	21st to end	Night	18% 8% 3 6% 5% 4 5% 3 4 6% 37%	2102
October	1st to 10th	Night	15% 7% 2 6% 5% 4 4 4 5% 7% 43%	2280
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 38%	2280
	21st to end	Night	22% 10% 3 6% 5% 4 4 3 5% 6% 32%	2508
November	1st to 10th	Night	12% 10% 3 6% 4 5% 4 3 5% 7% 41%	2426
	11th to 20th	Night	17% 15% 3 8% 6% 4 4 4 5% 7% 27%	2780
	21st to end	Night	19% 16% 5% 8% 5% 5% 5% 3 4 6% 25%	2800
December	1st to 10th	Night	15% 18% 9% 17% 7% 4 4 3 5% 4 13%	4580
	11th to 20th	Night	21% 19% 7% 12% 4 4 3 3 3 5% 20%	5205
	21st to end	Night	22% 20% 6% 11% 5% 4 4 3 5% 5% 14%	6996

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	77% 3 7% 7% 4	3902
	11th to 20th	Day	80% 2 6% 9% 3 1	4060
	21st to end	Day	76% 3 8% 9% 4	4466
February	1st to 10th	Day	70% 3 9% 13% 6%	1800
	11th to 20th	Day	67% 4 9% 13% 6%	1762
	21st to end	Day	64% 4 11% 14% 6% 1	1628
March	1st to 10th	Day	57% 4 10% 23% 6%	3545
	11th to 20th	Day	56% 4 15% 19% 6% 1	3491
	21st to end	Day	54% 3 10% 20% 12% 1	3815
April	1st to 10th	Day	54% 4 12% 17% 12% 1	2204
	11th to 20th	Day	53% 4 10% 18% 13% 2	2289
	21st to end	Day	52% 5% 10% 20% 11% 2	2470
May	1st to 10th	Day	56% 5% 9% 21% 8% 1	4120
	11th to 20th	Day	54% 6% 11% 20% 8% 1	4103
	21st to end	Day	42% 6% 14% 23% 13% 3	4837
June	1st to 10th	Day	48% 6% 12% 22% 11% 1	2660
	11th to 20th	Day	46% 6% 14% 20% 13% 1	2660
	21st to end	Day	43% 6% 11% 27% 12% 1	2660
July	1st to 10th	Day	39% 8% 12% 23% 15% 2	4370
	11th to 20th	Day	38% 6% 13% 27% 16%	4051
	21st to end	Day	41% 8% 13% 21% 17% 1	4324
August	1st to 10th	Day	50% 7% 13% 22% 8%	4091
	11th to 20th	Day	44% 8% 13% 26% 8% 1	4083
	21st to end	Day	40% 7% 12% 27% 12% 1	4317
September	1st to 10th	Day	42% 6% 11% 22% 17% 3	2280
	11th to 20th	Day	39% 6% 13% 24% 16% 1	2118
	21st to end	Day	50% 5% 11% 22% 12%	2077
October	1st to 10th	Day	36% 5% 12% 28% 18% 1	3160
	11th to 20th	Day	45% 6% 11% 21% 13% 4	3140
	21st to end	Day	41% 4 13% 28% 13% 1	3428
November	1st to 10th	Day	46% 4 12% 20% 16% 2	1867
	11th to 20th	Day	56% 6% 11% 17% 8% 2	1617
	21st to end	Day	66% 4 10% 14% 5% 1	1600
December	1st to 10th	Day	78% 3 9% 7% 3	2600
	11th to 20th	Day	68% 4 9% 15% 4	2986
	21st to end	Day	77% 3 8% 9% 3	3960
January	1st to 10th	Night	77% 3 8% 9% 3	6027
	11th to 20th	Night	77% 4 8% 9% 2	5900
	21st to end	Night	74% 3 8% 10% 4 1	6490
February	1st to 10th	Night	68% 3 8% 15% 5%	2600
	11th to 20th	Night	65% 4 9% 15% 6%	2535
	21st to end	Night	63% 4 9% 14% 9% 1	1995
March	1st to 10th	Night	57% 3 10% 23% 7%	3528
	11th to 20th	Night	55% 4 14% 19% 7% 1	3498
	21st to end	Night	49% 4 9% 22% 14% 1	3817
April	1st to 10th	Night	54% 5% 9% 18% 13% 1	1974
	11th to 20th	Night	49% 5% 10% 18% 15% 3	1856
	21st to end	Night	48% 6% 11% 22% 12% 2	1710
May	1st to 10th	Night	56% 5% 8% 18% 11% 2	2840
	11th to 20th	Night	48% 6% 11% 24% 9% 1	2791
	21st to end	Night	36% 6% 14% 25% 15% 4	2739
June	1st to 10th	Night	37% 7% 14% 26% 15% 1	1520
	11th to 20th	Night	39% 6% 15% 24% 15% 2	1520
	21st to end	Night	38% 7% 14% 23% 17%	1520
July	1st to 10th	Night	42% 7% 10% 21% 18% 2	2480
	11th to 20th	Night	34% 7% 16% 27% 15% 1	2782
	21st to end	Night	39% 7% 11% 18% 23% 2	2988
August	1st to 10th	Night	45% 7% 13% 22% 11% 1	2814
	11th to 20th	Night	41% 6% 12% 31% 10% 1	2812
	21st to end	Night	33% 9% 15% 29% 13% 2	3306
September	1st to 10th	Night	37% 5% 12% 25% 19% 4	1900
	11th to 20th	Night	30% 5% 12% 28% 23% 1	2059
	21st to end	Night	48% 4 11% 20% 16% 1	2102
October	1st to 10th	Night	37% 4 10% 27% 22% 1	3800
	11th to 20th	Night	40% 6% 11% 21% 15% 7%	3779
	21st to end	Night	38% 5% 13% 26% 18% 1	4120
November	1st to 10th	Night	42% 4 12% 24% 15% 3	2426
	11th to 20th	Night	56% 5% 11% 17% 9% 3	2780
	21st to end	Night	60% 4 12% 18% 5% 1	2800
December	1st to 10th	Night	72% 6% 12% 7% 3	4580
	11th to 20th	Night	68% 4 11% 14% 3	5208
	21st to end	Night	71% 5% 10% 12% 2	6996

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	34% 28% 24% 10% 3 1	267
	11th to 20th	Day	34% 29% 28% 7% 1 1	300
	21st to end	Day	32% 29% 30% 7% 2	330
February	1st to 10th	Day	33% 28% 32% 6% 1	300
	11th to 20th	Day	40% 26% 28% 5% 1	300
	21st to end	Day	39% 28% 26% 7%	282
March	1st to 10th	Day	31% 23% 30% 13% 3	500
	11th to 20th	Day	33% 18% 34% 10% 3 2	464
	21st to end	Day	32% 21% 27% 14% 4 1	506
April	1st to 10th	Day	32% 20% 27% 16% 6% 1	460
	11th to 20th	Day	27% 20% 28% 13% 8% 3	452
	21st to end	Day	29% 18% 32% 15% 5% 2	460
May	1st to 10th	Day	29% 18% 28% 16% 6% 2	463
	11th to 20th	Day	25% 13% 32% 18% 9% 3	487
	21st to end	Day	16% 12% 27% 25% 13% 7%	529
June	1st to 10th	Day	16% 15% 30% 25% 11% 3	490
	11th to 20th	Day	19% 14% 24% 28% 12% 3	490
	21st to end	Day	17% 13% 33% 24% 11% 2	490
July	1st to 10th	Day	12% 7% 24% 28% 20% 9%	485
	11th to 20th	Day	13% 7% 29% 27% 17% 7%	484
	21st to end	Day	12% 7% 29% 29% 15% 8%	532
August	1st to 10th	Day	14% 7% 23% 27% 21% 7%	486
	11th to 20th	Day	15% 6% 25% 30% 15% 9%	479
	21st to end	Day	13% 5% 25% 29% 18% 9%	539
September	1st to 10th	Day	19% 7% 21% 26% 19% 7%	490
	11th to 20th	Day	12% 5% 23% 30% 19% 11%	490
	21st to end	Day	26% 10% 25% 22% 14% 3	490
October	1st to 10th	Day	17% 11% 29% 23% 17% 3	490
	11th to 20th	Day	26% 17% 27% 19% 8% 2	490
	21st to end	Day	31% 16% 29% 18% 6%	539
November	1st to 10th	Day	21% 19% 34% 15% 10% 2	405
	11th to 20th	Day	29% 24% 30% 13% 3 2	207
	21st to end	Day	24% 33% 35% 9% 1	200
December	1st to 10th	Day	35% 27% 27% 7% 3 2	200
	11th to 20th	Day	37% 20% 33% 8% 3	200
	21st to end	Day	35% 25% 28% 10% 1	220
January	1st to 10th	Night	30% 23% 33% 12% 2	800
	11th to 20th	Night	32% 22% 30% 14% 3	800
	21st to end	Night	28% 22% 33% 15% 2	880
February	1st to 10th	Night	32% 19% 28% 19% 1	800
	11th to 20th	Night	31% 22% 32% 13% 1	783
	21st to end	Night	31% 21% 31% 16% 2	660
March	1st to 10th	Night	26% 20% 33% 18% 3	800
	11th to 20th	Night	30% 18% 26% 19% 7%	767
	21st to end	Night	26% 16% 35% 19% 4	836
April	1st to 10th	Night	26% 16% 31% 20% 6%	760
	11th to 20th	Night	24% 15% 32% 20% 8% 1	732
	21st to end	Night	21% 12% 35% 26% 5% 1	570
May	1st to 10th	Night	23% 10% 24% 31% 11% 1	570
	11th to 20th	Night	19% 10% 28% 33% 10%	552
	21st to end	Night	10% 6% 27% 32% 22% 3	411
June	1st to 10th	Night	9% 5% 32% 37% 16% 1	380
	11th to 20th	Night	12% 7% 26% 39% 16%	380
	21st to end	Night	9% 9% 28% 36% 18% 1	380
July	1st to 10th	Night	11% 3 18% 44% 20% 5%	370
	11th to 20th	Night	11% 3 20% 37% 26% 4	548
	21st to end	Night	13% 3 14% 42% 26% 2	624
August	1st to 10th	Night	13% 2 15% 41% 25% 3	567
	11th to 20th	Night	12% 4 15% 38% 27% 4	564
	21st to end	Night	11% 4 21% 34% 25% 5%	731
September	1st to 10th	Night	16% 4 24% 30% 24% 3	760
	11th to 20th	Night	12% 5% 19% 32% 28% 4	760
	21st to end	Night	21% 10% 22% 26% 17% 4	760
October	1st to 10th	Night	19% 7% 25% 27% 20% 2	760
	11th to 20th	Night	21% 12% 33% 24% 8% 2	760
	21st to end	Night	28% 13% 29% 24% 6%	836
November	1st to 10th	Night	19% 13% 31% 27% 10% 1	780
	11th to 20th	Night	29% 17% 27% 19% 6% 1	800
	21st to end	Night	31% 17% 30% 18% 4	800
December	1st to 10th	Night	33% 22% 27% 15% 3	800
	11th to 20th	Night	30% 24% 26% 17% 3	800
	21st to end	Night	31% 20% 30% 18% 2	880

Page generated at 2025-03-09 08:08:45. Version ac07

Copyright © 2025 Attilla Danko.