Mole Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mole Hill Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	11% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	126100
	Night	13% 6% 2 6% 4 4 4 3 5% 8% 45%	123234
Transparency	Day	24% 40% 10% 14% 8% 4	129815
	Night	24% 39% 9% 13% 9% 5%	127569
Seeing	Day	11% 3 12% 26% 34% 14%	15812
	Night	14% 4 15% 30% 30% 7%	25653

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	21% 11% 3 7% 4 4 4 3 5% 5% 33%	4077
	11th to 20th	Day	16% 7% 3 4 3 3 3 4 6% 8% 43%	4080
	21st to end	Day	28% 8% 2 6% 4 3 4 4 5% 6% 31%	4649
February	1st to 10th	Day	19% 10% 3 7% 4 3 2 3 4 6% 38%	2000
	11th to 20th	Day	18% 9% 4 7% 4 3 3 3 4 5% 38%	1949
	21st to end	Day	20% 7% 2 6% 3 2 3 4 5% 6% 41%	1762
March	1st to 10th	Day	14% 7% 2 7% 4 4 5% 4 6% 8% 39%	4936
	11th to 20th	Day	13% 7% 3 7% 4 4 4 3 4 6% 45%	4980
	21st to end	Day	16% 7% 3 7% 4 4 4 3 4 6% 42%	5462
April	1st to 10th	Day	12% 8% 3 6% 4 4 5% 4 6% 9% 41%	2200
	11th to 20th	Day	14% 8% 3 6% 5% 5% 5% 4 5% 7% 38%	2210
	21st to end	Day	11% 7% 2 6% 5% 4 4 4 6% 8% 42%	2400
May	1st to 10th	Day	16% 8% 3 9% 6% 6% 7% 5% 6% 8% 27%	5712
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 5% 7% 10% 45%	5862
	21st to end	Day	7% 5% 3 7% 5% 6% 7% 6% 10% 12% 32%	6434
June	1st to 10th	Day	4 3 2 4 4 4 5% 5% 10% 13% 46%	2600
	11th to 20th	Day	5% 4 2 5% 5% 5% 6% 5% 9% 12% 41%	2600
	21st to end	Day	6% 5% 2 6% 6% 6% 6% 6% 11% 13% 34%	2600
July	1st to 10th	Day	7% 6% 2 7% 5% 6% 6% 5% 8% 10% 37%	5900
	11th to 20th	Day	4 5% 2 7% 6% 6% 6% 6% 8% 13% 35%	5900
	21st to end	Day	8% 6% 2 6% 5% 5% 5% 5% 8% 12% 39%	6422
August	1st to 10th	Day	1 2 1 2 3 3 4 3 6% 10% 65%	4234
	11th to 20th	Day	3 2 1 3 3 4 5% 5% 10% 15% 48%	3984
	21st to end	Day	5% 4 2 7% 5% 6% 7% 5% 9% 13% 38%	3949
September	1st to 10th	Day	8% 7% 3 8% 5% 7% 6% 5% 9% 11% 32%	2200
	11th to 20th	Day	10% 6% 2 6% 6% 5% 5% 5% 8% 9% 38%	2178
	21st to end	Day	8% 6% 2 5% 4 5% 6% 5% 7% 9% 44%	2090
October	1st to 10th	Day	5% 4 1 4 4 4 5% 4 7% 10% 51%	2068
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 5% 7% 50%	1900
	21st to end	Day	10% 5% 2 6% 3 4 4 3 5% 7% 52%	2090
November	1st to 10th	Day	9% 6% 3 6% 5% 4 5% 5% 6% 9% 42%	1958
	11th to 20th	Day	14% 5% 2 6% 4 4 4 4 4 6% 47%	2000
	21st to end	Day	16% 7% 2 6% 5% 5% 5% 3 4 6% 40%	1895
December	1st to 10th	Day	27% 11% 4 7% 5% 3 3 3 4 5% 29%	2940
	11th to 20th	Day	11% 7% 3 7% 5% 4 5% 4 6% 8% 40%	3391
	21st to end	Day	13% 6% 3 6% 3 4 4 3 5% 7% 47%	4488
January	1st to 10th	Night	22% 9% 3 7% 4 3 3 3 3 4 38%	5888
	11th to 20th	Night	14% 6% 2 6% 4 3 3 3 5% 7% 47%	5900
	21st to end	Night	28% 8% 3 7% 3 3 4 3 5% 5% 31%	6370
February	1st to 10th	Night	19% 9% 3 7% 4 3 4 3 4 6% 40%	2400
	11th to 20th	Night	18% 7% 2 5% 3 3 4 4 4 6% 43%	2338
	21st to end	Night	18% 9% 2 5% 5% 3 4 3 5% 5% 40%	1865
March	1st to 10th	Night	20% 9% 2 6% 3 3 4 3 5% 7% 39%	4919
	11th to 20th	Night	15% 8% 2 6% 4 4 3 3 4 5% 46%	4980
	21st to end	Night	17% 7% 2 5% 2 3 3 3 4 5% 48%	5467
April	1st to 10th	Night	14% 8% 3 6% 5% 3 5% 3 6% 8% 39%	2200
	11th to 20th	Night	16% 7% 3 5% 4 3 3 3 5% 7% 44%	2136
	21st to end	Night	14% 6% 2 7% 5% 4 5% 4 6% 7% 40%	2000
May	1st to 10th	Night	25% 9% 3 6% 4 4 4 3 6% 6% 29%	4192
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 9% 47%	4053
	21st to end	Night	13% 8% 3 7% 4 5% 4 5% 7% 11% 32%	4443
June	1st to 10th	Night	5% 3 1 4 3 3 4 4 8% 11% 54%	1800
	11th to 20th	Night	5% 4 1 4 3 4 5% 4 6% 12% 50%	1800
	21st to end	Night	5% 5% 2 5% 4 4 5% 6% 9% 13% 43%	1800
July	1st to 10th	Night	5% 5% 2 7% 5% 5% 6% 5% 7% 10% 43%	4078
	11th to 20th	Night	3 4 2 6% 5% 5% 6% 6% 7% 12% 43%	4077
	21st to end	Night	6% 5% 2 6% 4 5% 5% 4 7% 11% 44%	4449
August	1st to 10th	Night	1 1 2 1 2 2 2 4 8% 77%	2926
	11th to 20th	Night	2 2 1 3 3 3 4 4 7% 14% 59%	3062
	21st to end	Night	3 2 1 3 3 3 4 4 8% 13% 56%	3949
September	1st to 10th	Night	7% 4 3 7% 4 5% 5% 4 9% 11% 42%	2200
	11th to 20th	Night	9% 5% 2 7% 4 3 4 4 6% 9% 45%	2178
	21st to end	Night	6% 4 2 5% 4 4 4 4 6% 9% 52%	2090
October	1st to 10th	Night	4 3 2 5% 4 4 4 3 6% 8% 56%	2090
	11th to 20th	Night	9% 4 2 5% 2 3 3 2 4 7% 60%	2280
	21st to end	Night	8% 3 2 4 3 3 3 3 3 6% 61%	2508
November	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 5% 7% 53%	2340
	11th to 20th	Night	14% 6% 2 6% 3 4 3 3 4 5% 50%	2400
	21st to end	Night	15% 6% 2 6% 4 4 5% 3 4 7% 43%	2500
December	1st to 10th	Night	28% 11% 4 8% 4 3 2 2 3 4 29%	4250
	11th to 20th	Night	13% 7% 2 7% 4 4 5% 3 5% 6% 43%	4816
	21st to end	Night	12% 6% 3 6% 4 3 4 3 4 6% 49%	6490

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% 28% 5% 14% 6% 4	4078
	11th to 20th	Day	28% 32% 7% 14% 13% 5%	4080
	21st to end	Day	42% 29% 3 8% 11% 7%	4649
February	1st to 10th	Day	23% 62% 2 3 5% 5%	2000
	11th to 20th	Day	18% 61% 4 9% 5% 2	1959
	21st to end	Day	19% 63% 4 6% 5% 3	1762
March	1st to 10th	Day	34% 32% 9% 11% 3 11%	4936
	11th to 20th	Day	30% 31% 5% 10% 12% 13%	4980
	21st to end	Day	31% 31% 7% 15% 12% 4	5464
April	1st to 10th	Day	15% 63% 3 6% 8% 6%	2200
	11th to 20th	Day	16% 64% 5% 6% 5% 3	2210
	21st to end	Day	15% 63% 4 10% 5% 2	2400
May	1st to 10th	Day	39% 34% 10% 10% 6% 2	5748
	11th to 20th	Day	22% 31% 14% 16% 12% 4	5866
	21st to end	Day	28% 36% 12% 21% 2	6447
June	1st to 10th	Day	8% 64% 9% 14% 5%	2600
	11th to 20th	Day	12% 65% 6% 11% 5%	2600
	21st to end	Day	12% 64% 11% 11% 2	2600
July	1st to 10th	Day	27% 30% 27% 15% 1	5836
	11th to 20th	Day	27% 31% 27% 12% 2	5831
	21st to end	Day	27% 29% 18% 20% 5%	6240
August	1st to 10th	Day	5% 37% 12% 37% 9%	4220
	11th to 20th	Day	10% 39% 29% 20% 1	4023
	21st to end	Day	19% 41% 16% 18% 4 1	3948
September	1st to 10th	Day	15% 60% 8% 8% 7% 1	2200
	11th to 20th	Day	12% 60% 8% 13% 6% 1	2178
	21st to end	Day	14% 62% 8% 10% 3 2	2090
October	1st to 10th	Day	11% 38% 4 9% 16% 22%	3432
	11th to 20th	Day	12% 39% 7% 13% 21% 7%	3140
	21st to end	Day	17% 39% 5% 16% 20% 3	3428
November	1st to 10th	Day	21% 59% 8% 7% 4 2	1958
	11th to 20th	Day	21% 57% 4 8% 5% 5%	2000
	21st to end	Day	22% 58% 5% 7% 7% 2	1895
December	1st to 10th	Day	44% 36% 4 5% 9% 1	2940
	11th to 20th	Day	24% 35% 5% 16% 11% 8%	3389
	21st to end	Day	28% 28% 5% 16% 13% 10%	4488
January	1st to 10th	Night	41% 28% 5% 10% 9% 7%	5888
	11th to 20th	Night	28% 28% 6% 15% 17% 6%	5900
	21st to end	Night	41% 29% 5% 7% 11% 6%	6370
February	1st to 10th	Night	21% 62% 3 3 6% 6%	2400
	11th to 20th	Night	16% 62% 4 9% 6% 4	2338
	21st to end	Night	18% 63% 3 6% 6% 4	1865
March	1st to 10th	Night	35% 30% 7% 12% 7% 8%	4919
	11th to 20th	Night	31% 30% 4 8% 13% 14%	4980
	21st to end	Night	27% 29% 7% 15% 17% 4	5467
April	1st to 10th	Night	16% 62% 4 6% 7% 5%	2200
	11th to 20th	Night	16% 63% 5% 6% 5% 5%	2136
	21st to end	Night	16% 63% 5% 9% 5% 2	2000
May	1st to 10th	Night	43% 31% 9% 9% 6% 2	4221
	11th to 20th	Night	23% 31% 10% 21% 11% 4	4054
	21st to end	Night	31% 33% 15% 17% 3	4452
June	1st to 10th	Night	8% 63% 7% 16% 6%	1800
	11th to 20th	Night	13% 63% 5% 12% 6%	1800
	21st to end	Night	13% 63% 9% 14% 1	1800
July	1st to 10th	Night	26% 29% 25% 20% 1	4035
	11th to 20th	Night	23% 31% 29% 15% 2	4026
	21st to end	Night	25% 29% 19% 19% 7%	4320
August	1st to 10th	Night	3 36% 9% 42% 10%	2916
	11th to 20th	Night	8% 38% 28% 25% 1	3089
	21st to end	Night	10% 41% 20% 22% 6%	3949
September	1st to 10th	Night	12% 60% 11% 8% 7% 2	2200
	11th to 20th	Night	13% 59% 6% 13% 7% 1	2178
	21st to end	Night	14% 62% 6% 12% 3 2	2090
October	1st to 10th	Night	11% 38% 5% 8% 11% 26%	3480
	11th to 20th	Night	9% 37% 7% 14% 23% 10%	3779
	21st to end	Night	12% 38% 4 17% 24% 6%	4120
November	1st to 10th	Night	19% 58% 7% 8% 5% 3	2340
	11th to 20th	Night	22% 58% 4 7% 6% 4	2400
	21st to end	Night	21% 58% 4 8% 7% 3	2500
December	1st to 10th	Night	47% 36% 3 5% 7% 2	4250
	11th to 20th	Night	25% 34% 6% 14% 11% 10%	4817
	21st to end	Night	26% 29% 5% 14% 16% 10%	6490

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	22% 6% 23% 35% 14% 1	300
	11th to 20th	Day	22% 9% 24% 30% 15% 1	300
	21st to end	Day	20% 6% 29% 30% 14%	330
February	1st to 10th	Day	27% 9% 19% 28% 16% 2	300
	11th to 20th	Day	25% 8% 22% 31% 14% 1	300
	21st to end	Day	19% 8% 23% 41% 9%	249
March	1st to 10th	Day	19% 7% 22% 39% 12% 1	300
	11th to 20th	Day	19% 6% 25% 38% 11% 1	300
	21st to end	Day	14% 5% 25% 43% 12%	330
April	1st to 10th	Day	17% 5% 29% 33% 15%	300
	11th to 20th	Day	11% 9% 27% 34% 16% 2	328
	21st to end	Day	13% 5% 22% 41% 18% 1	500
May	1st to 10th	Day	12% 7% 20% 44% 16% 1	629
	11th to 20th	Day	11% 4 15% 42% 26% 3	725
	21st to end	Day	7% 3 12% 39% 36% 3	789
June	1st to 10th	Day	4 1 7% 29% 48% 11%	730
	11th to 20th	Day	6% 1 4 30% 48% 11%	730
	21st to end	Day	7% 1 5% 17% 50% 20%	730
July	1st to 10th	Day	8% 1 3 15% 47% 26%	721
	11th to 20th	Day	4 2 7% 58% 29%	718
	21st to end	Day	6% 1 2 9% 51% 32%	794
August	1st to 10th	Day	1 1 8% 51% 39%	726
	11th to 20th	Day	3 1 6% 48% 42%	606
	21st to end	Day	9% 1 2 7% 35% 46%	363
September	1st to 10th	Day	9% 1 4 12% 44% 31%	330
	11th to 20th	Day	8% 1 2 13% 40% 36%	324
	21st to end	Day	6% 3 14% 47% 31%	300
October	1st to 10th	Day	6% 1 6% 20% 48% 19%	300
	11th to 20th	Day	9% 2 9% 24% 38% 18%	300
	21st to end	Day	15% 5% 16% 23% 35% 7%	330
November	1st to 10th	Day	15% 3 8% 25% 40% 9%	300
	11th to 20th	Day	18% 3 13% 29% 31% 6%	300
	21st to end	Day	22% 6% 20% 30% 16% 6%	300
December	1st to 10th	Day	23% 6% 16% 28% 23% 4	300
	11th to 20th	Day	18% 5% 23% 32% 19% 2	300
	21st to end	Day	20% 5% 17% 36% 19% 2	330
January	1st to 10th	Night	22% 7% 25% 31% 15% 1	1000
	11th to 20th	Night	20% 8% 23% 37% 12% 1	1000
	21st to end	Night	21% 7% 25% 34% 12%	1045
February	1st to 10th	Night	25% 7% 22% 33% 13%	800
	11th to 20th	Night	23% 9% 19% 35% 13%	784
	21st to end	Night	21% 9% 24% 36% 10%	545
March	1st to 10th	Night	19% 7% 25% 35% 15%	600
	11th to 20th	Night	16% 7% 22% 42% 12%	600
	21st to end	Night	16% 6% 21% 41% 15% 1	660
April	1st to 10th	Night	16% 6% 25% 42% 12%	600
	11th to 20th	Night	18% 6% 23% 36% 17%	593
	21st to end	Night	16% 6% 22% 39% 16% 1	600
May	1st to 10th	Night	16% 4 20% 46% 14%	600
	11th to 20th	Night	10% 3 15% 47% 22% 2	591
	21st to end	Night	6% 2 13% 40% 37% 2	650
June	1st to 10th	Night	5% 1 5% 30% 54% 5%	600
	11th to 20th	Night	5% 1 3 34% 52% 4	600
	21st to end	Night	6% 1 6% 21% 50% 16%	600
July	1st to 10th	Night	6% 2 3 17% 54% 19%	585
	11th to 20th	Night	2 1 3 10% 58% 26%	582
	21st to end	Night	4 1 2 13% 59% 22%	657
August	1st to 10th	Night	1 1 8% 62% 29%	597
	11th to 20th	Night	3 1 6% 65% 25%	594
	21st to end	Night	5% 1 10% 51% 32%	660
September	1st to 10th	Night	9% 1 3 13% 53% 22%	600
	11th to 20th	Night	11% 1 4 14% 51% 20%	594
	21st to end	Night	7% 2 5% 19% 52% 14%	570
October	1st to 10th	Night	5% 1 5% 22% 52% 15%	570
	11th to 20th	Night	11% 2 8% 31% 41% 6%	760
	21st to end	Night	10% 3 15% 35% 33% 6%	836
November	1st to 10th	Night	12% 3 10% 31% 37% 7%	780
	11th to 20th	Night	16% 4 17% 30% 30% 3	800
	21st to end	Night	18% 5% 20% 35% 20% 2	900
December	1st to 10th	Night	22% 6% 19% 28% 23% 3	1000
	11th to 20th	Night	20% 9% 20% 32% 18% 2	1000
	21st to end	Night	21% 8% 21% 33% 16% 2	1100

Page generated at 2025-09-16 00:49:15. Version ac07

Copyright © 2025 Attilla Danko.