Lake Hamilton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Hamilton clear sky chart from 2005-11-06 to 2025-02-21.

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	14% 7% 2 6% 4 4 4 3 5% 7% 45%	108580
	Night	14% 6% 2 5% 3 3 3 3 4 6% 50%	110189
Transparency	Day	37% 6% 10% 22% 19% 6%	112226
	Night	34% 5% 9% 23% 22% 7%	114683
Seeing	Day	16% 8% 23% 26% 20% 6%	15642
	Night	16% 8% 24% 31% 18% 2	25610

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	18% 8% 3 5% 3 2 3 2 3 4 49%	4077
	11th to 20th	Day	12% 9% 2 5% 4 3 3 2 4 4 53%	4080
	21st to end	Day	24% 6% 2 3 2 1 1 2 3 5% 50%	4488
February	1st to 10th	Day	23% 9% 3 5% 3 4 5% 2 4 4 39%	1800
	11th to 20th	Day	20% 9% 2 5% 4 3 3 3 4 5% 41%	1853
	21st to end	Day	24% 9% 3 7% 4 4 3 2 4 4 37%	1679
March	1st to 10th	Day	22% 11% 3 6% 3 3 3 3 3 5% 38%	3436
	11th to 20th	Day	15% 8% 3 6% 4 4 4 4 5% 7% 41%	3480
	21st to end	Day	17% 9% 2 7% 4 3 3 3 4 6% 42%	3814
April	1st to 10th	Day	16% 7% 2 6% 4 3 3 3 5% 6% 46%	2239
	11th to 20th	Day	18% 5% 2 7% 4 4 3 3 4 6% 45%	2254
	21st to end	Day	15% 7% 4 6% 5% 4 4 3 5% 6% 41%	2280
May	1st to 10th	Day	21% 7% 2 6% 4 4 4 4 5% 7% 37%	3789
	11th to 20th	Day	13% 6% 2 7% 5% 4 4 4 6% 6% 42%	4082
	21st to end	Day	15% 8% 3 8% 6% 5% 6% 4 6% 7% 33%	4477
June	1st to 10th	Day	9% 5% 2 6% 4 5% 6% 4 7% 8% 43%	2470
	11th to 20th	Day	6% 5% 2 7% 5% 5% 5% 5% 7% 9% 45%	2470
	21st to end	Day	5% 4 2 5% 5% 5% 5% 5% 8% 10% 45%	2470
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 11% 40%	4120
	11th to 20th	Day	6% 4 2 4 4 4 4 4 6% 9% 54%	4120
	21st to end	Day	12% 8% 3 8% 5% 6% 5% 5% 7% 9% 31%	4465
August	1st to 10th	Day	3 2 1 3 4 4 4 4 6% 9% 60%	4104
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 10% 45%	3798
	21st to end	Day	4 3 2 6% 4 4 5% 5% 8% 8% 50%	4180
September	1st to 10th	Day	11% 6% 2 5% 4 5% 5% 3 5% 8% 47%	2280
	11th to 20th	Day	15% 5% 2 4 4 4 5% 4 6% 7% 44%	2219
	21st to end	Day	10% 4 2 4 4 4 4 3 5% 7% 52%	2009
October	1st to 10th	Day	8% 4 2 5% 3 4 3 3 6% 5% 57%	1900
	11th to 20th	Day	15% 5% 1 4 2 2 3 2 4 4 57%	1900
	21st to end	Day	19% 4 2 5% 3 3 3 3 4 5% 52%	2090
November	1st to 10th	Day	13% 7% 3 4 3 2 3 2 4 6% 53%	1958
	11th to 20th	Day	13% 5% 1 5% 3 3 3 2 4 6% 54%	2000
	21st to end	Day	20% 7% 2 4 3 3 3 3 4 5% 47%	1819
December	1st to 10th	Day	19% 8% 2 4 4 2 3 3 3 4 49%	2610
	11th to 20th	Day	20% 9% 3 6% 4 4 3 3 4 4 41%	3282
	21st to end	Day	21% 8% 2 6% 4 4 3 3 3 5% 40%	4488
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 5% 49%	5888
	11th to 20th	Night	13% 5% 1 3 3 2 2 2 3 4 61%	5900
	21st to end	Night	23% 9% 2 4 3 2 2 2 3 4 47%	6490
February	1st to 10th	Night	22% 8% 3 6% 3 3 4 2 4 4 42%	2600
	11th to 20th	Night	19% 9% 3 5% 4 3 3 2 4 5% 43%	2433
	21st to end	Night	22% 7% 2 4 3 3 4 2 3 5% 45%	1790
March	1st to 10th	Night	21% 8% 3 5% 3 4 3 3 5% 5% 40%	3419
	11th to 20th	Night	16% 7% 2 5% 4 3 3 2 4 5% 49%	3480
	21st to end	Night	12% 7% 3 7% 5% 4 4 3 5% 7% 43%	3817
April	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 5% 6% 50%	1939
	11th to 20th	Night	14% 4 2 5% 4 3 4 3 6% 6% 49%	1875
	21st to end	Night	13% 6% 2 5% 3 3 3 4 5% 7% 49%	1900
May	1st to 10th	Night	21% 7% 2 6% 4 4 4 4 5% 7% 37%	3102
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 5% 7% 44%	2823
	21st to end	Night	14% 7% 3 6% 5% 5% 4 3 5% 8% 41%	3090
June	1st to 10th	Night	7% 4 1 4 3 4 4 4 7% 10% 53%	1710
	11th to 20th	Night	4 5% 1 4 4 2 4 3 4 8% 59%	1710
	21st to end	Night	4 3 1 3 4 3 4 4 6% 9% 59%	1710
July	1st to 10th	Night	8% 4 2 5% 4 5% 5% 4 7% 10% 48%	2850
	11th to 20th	Night	4 3 1 4 2 2 3 3 6% 12% 59%	2850
	21st to end	Night	9% 5% 3 7% 5% 5% 4 4 7% 9% 41%	3098
August	1st to 10th	Night	2 2 1 3 2 2 2 2 4 8% 72%	2836
	11th to 20th	Night	5% 3 1 4 3 4 4 4 7% 10% 55%	3033
	21st to end	Night	3 3 1 4 3 4 5% 4 7% 9% 55%	3476
September	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 7% 55%	1900
	11th to 20th	Night	9% 6% 2 6% 4 3 5% 3 5% 7% 50%	1956
	21st to end	Night	8% 5% 1 4 3 3 3 3 4 6% 60%	2151
October	1st to 10th	Night	9% 3 1 4 3 3 3 3 4 6% 61%	2280
	11th to 20th	Night	11% 5% 2 4 3 2 2 2 3 5% 61%	2280
	21st to end	Night	16% 6% 2 5% 3 3 2 2 2 4 56%	2508
November	1st to 10th	Night	13% 5% 2 5% 3 3 2 3 4 4 57%	2340
	11th to 20th	Night	11% 5% 2 4 4 2 3 3 4 5% 57%	2400
	21st to end	Night	16% 7% 2 5% 2 2 3 3 3 5% 52%	2570
December	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 4 4 51%	4580
	11th to 20th	Night	19% 9% 3 7% 4 3 3 2 3 4 43%	4915
	21st to end	Night	19% 9% 3 6% 4 3 3 2 4 5% 44%	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	41% 3 8% 26% 19% 3	4078
	11th to 20th	Day	37% 4 7% 21% 26% 5%	4080
	21st to end	Day	40% 2 4 18% 24% 11%	4488
February	1st to 10th	Day	50% 3 7% 18% 17% 4	1800
	11th to 20th	Day	46% 5% 6% 20% 18% 6%	1862
	21st to end	Day	52% 3 6% 12% 18% 8%	1679
March	1st to 10th	Day	49% 5% 7% 12% 17% 9%	3436
	11th to 20th	Day	41% 6% 9% 21% 17% 6%	3480
	21st to end	Day	44% 5% 8% 21% 20% 1	3814
April	1st to 10th	Day	39% 5% 8% 22% 19% 6%	2239
	11th to 20th	Day	42% 4 8% 20% 20% 6%	2254
	21st to end	Day	42% 6% 10% 19% 20% 3	2280
May	1st to 10th	Day	46% 7% 10% 22% 13% 2	3824
	11th to 20th	Day	38% 9% 11% 25% 16% 1	4086
	21st to end	Day	46% 10% 13% 18% 9% 4	4489
June	1st to 10th	Day	36% 8% 14% 24% 15% 2	2470
	11th to 20th	Day	34% 7% 13% 25% 19% 2	2470
	21st to end	Day	29% 9% 15% 28% 17% 3	2470
July	1st to 10th	Day	35% 9% 18% 28% 10% 1	4056
	11th to 20th	Day	26% 6% 12% 32% 22% 2	4051
	21st to end	Day	47% 9% 14% 21% 9%	4325
August	1st to 10th	Day	20% 7% 16% 27% 26% 5%	4090
	11th to 20th	Day	34% 7% 16% 32% 10% 1	3835
	21st to end	Day	29% 8% 13% 27% 20% 2	4179
September	1st to 10th	Day	36% 7% 11% 19% 18% 8%	2280
	11th to 20th	Day	37% 7% 11% 17% 21% 6%	2219
	21st to end	Day	32% 6% 9% 19% 26% 9%	2009
October	1st to 10th	Day	16% 3 7% 12% 30% 32%	3160
	11th to 20th	Day	19% 3 3 18% 36% 20%	3140
	21st to end	Day	31% 4 5% 26% 28% 7%	3428
November	1st to 10th	Day	34% 4 8% 23% 23% 8%	1958
	11th to 20th	Day	31% 4 8% 18% 27% 11%	2000
	21st to end	Day	42% 3 6% 17% 26% 5%	1819
December	1st to 10th	Day	41% 3 6% 26% 19% 4	2610
	11th to 20th	Day	46% 4 4 20% 22% 4	3280
	21st to end	Day	46% 5% 7% 22% 17% 4	4488
January	1st to 10th	Night	37% 4 7% 27% 23% 2	5888
	11th to 20th	Night	29% 3 6% 21% 31% 9%	5900
	21st to end	Night	43% 3 7% 16% 24% 7%	6490
February	1st to 10th	Night	46% 3 7% 19% 18% 6%	2600
	11th to 20th	Night	45% 3 7% 19% 20% 6%	2434
	21st to end	Night	43% 4 7% 15% 22% 9%	1790
March	1st to 10th	Night	44% 7% 8% 12% 17% 11%	3419
	11th to 20th	Night	38% 6% 8% 24% 18% 7%	3480
	21st to end	Night	39% 6% 9% 22% 22% 2	3817
April	1st to 10th	Night	34% 5% 10% 21% 19% 11%	1939
	11th to 20th	Night	33% 5% 9% 22% 21% 10%	1875
	21st to end	Night	34% 6% 11% 23% 22% 3	1900
May	1st to 10th	Night	46% 8% 9% 21% 12% 4	3132
	11th to 20th	Night	39% 7% 12% 25% 15% 1	2824
	21st to end	Night	40% 9% 14% 22% 13% 2	3099
June	1st to 10th	Night	25% 8% 15% 29% 20% 2	1710
	11th to 20th	Night	24% 5% 12% 33% 22% 4	1710
	21st to end	Night	20% 7% 14% 30% 25% 4	1710
July	1st to 10th	Night	28% 9% 20% 29% 14% 1	2805
	11th to 20th	Night	18% 7% 13% 37% 23% 2	2796
	21st to end	Night	39% 8% 13% 25% 15% 1	2999
August	1st to 10th	Night	13% 4 16% 31% 29% 7%	2826
	11th to 20th	Night	23% 6% 19% 35% 15% 2	3062
	21st to end	Night	23% 7% 13% 28% 28% 2	3476
September	1st to 10th	Night	26% 8% 12% 23% 22% 9%	1900
	11th to 20th	Night	33% 6% 10% 22% 22% 7%	1956
	21st to end	Night	26% 5% 10% 21% 28% 11%	2151
October	1st to 10th	Night	16% 3 7% 13% 26% 35%	3800
	11th to 20th	Night	17% 2 4 16% 37% 25%	3779
	21st to end	Night	27% 3 4 23% 29% 13%	4120
November	1st to 10th	Night	32% 4 7% 20% 27% 10%	2340
	11th to 20th	Night	30% 4 7% 19% 27% 12%	2400
	21st to end	Night	37% 4 7% 18% 28% 6%	2570
December	1st to 10th	Night	37% 3 6% 30% 20% 5%	4580
	11th to 20th	Night	47% 3 5% 18% 20% 8%	4916
	21st to end	Night	43% 4 8% 23% 19% 3	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	27% 13% 37% 18% 4	300
	11th to 20th	Day	26% 17% 39% 15% 2 1	300
	21st to end	Day	24% 22% 35% 15% 4	330
February	1st to 10th	Day	33% 13% 33% 16% 5% 1	300
	11th to 20th	Day	30% 23% 33% 11% 3	300
	21st to end	Day	39% 20% 29% 10% 2	225
March	1st to 10th	Day	26% 14% 35% 20% 4 1	270
	11th to 20th	Day	29% 22% 31% 14% 4	270
	21st to end	Day	27% 19% 39% 13% 2	297
April	1st to 10th	Day	22% 18% 35% 14% 10%	419
	11th to 20th	Day	27% 13% 29% 22% 8% 1	452
	21st to end	Day	22% 11% 35% 20% 9% 2	460
May	1st to 10th	Day	20% 10% 31% 28% 9% 1	474
	11th to 20th	Day	15% 6% 32% 30% 14% 3	675
	21st to end	Day	11% 6% 28% 31% 17% 6%	734
June	1st to 10th	Day	12% 3 16% 32% 28% 9%	680
	11th to 20th	Day	7% 3 16% 38% 27% 9%	680
	21st to end	Day	5% 3 17% 38% 28% 8%	680
July	1st to 10th	Day	6% 2 14% 35% 32% 11%	671
	11th to 20th	Day	7% 2 9% 32% 38% 12%	668
	21st to end	Day	9% 2 9% 30% 37% 13%	739
August	1st to 10th	Day	7% 1 8% 38% 35% 11%	676
	11th to 20th	Day	15% 2 7% 31% 34% 11%	524
	21st to end	Day	10% 2 5% 26% 38% 19%	539
September	1st to 10th	Day	11% 2 10% 26% 37% 14%	490
	11th to 20th	Day	14% 2 12% 25% 34% 13%	429
	21st to end	Day	13% 5% 13% 40% 22% 7%	300
October	1st to 10th	Day	7% 2 28% 36% 23% 4	300
	11th to 20th	Day	15% 9% 35% 25% 14% 2	300
	21st to end	Day	24% 11% 30% 25% 8% 2	330
November	1st to 10th	Day	19% 12% 32% 22% 12% 3	300
	11th to 20th	Day	17% 12% 36% 26% 8% 1	300
	21st to end	Day	26% 15% 30% 21% 7% 1	300
December	1st to 10th	Day	24% 15% 33% 21% 6% 1	300
	11th to 20th	Day	29% 14% 34% 16% 6% 1	300
	21st to end	Day	30% 14% 38% 15% 3	330
January	1st to 10th	Night	24% 11% 30% 30% 4	1000
	11th to 20th	Night	23% 14% 33% 26% 4	1000
	21st to end	Night	22% 13% 35% 27% 4	1100
February	1st to 10th	Night	26% 14% 30% 25% 6%	1000
	11th to 20th	Night	24% 16% 35% 23% 2	879
	21st to end	Night	27% 14% 35% 21% 3	534
March	1st to 10th	Night	25% 9% 30% 31% 5%	570
	11th to 20th	Night	22% 13% 33% 28% 4	570
	21st to end	Night	18% 12% 36% 29% 5%	627
April	1st to 10th	Night	16% 13% 37% 26% 8%	570
	11th to 20th	Night	18% 11% 31% 29% 10% 1	563
	21st to end	Night	16% 8% 38% 28% 10%	570
May	1st to 10th	Night	16% 5% 28% 40% 10% 1	570
	11th to 20th	Night	16% 6% 27% 32% 17% 2	561
	21st to end	Night	10% 4 23% 35% 24% 3	617
June	1st to 10th	Night	7% 2 12% 38% 37% 4	570
	11th to 20th	Night	4 3 12% 42% 36% 4	570
	21st to end	Night	5% 1 10% 39% 38% 7%	570
July	1st to 10th	Night	5% 1 8% 37% 42% 7%	555
	11th to 20th	Night	4 1 6% 33% 47% 9%	552
	21st to end	Night	5% 1 4 33% 47% 10%	624
August	1st to 10th	Night	5% 2 5% 35% 45% 7%	567
	11th to 20th	Night	8% 2 4 36% 44% 6%	564
	21st to end	Night	8% 1 6% 32% 45% 8%	627
September	1st to 10th	Night	7% 2 8% 34% 42% 7%	570
	11th to 20th	Night	11% 1 11% 33% 39% 4	570
	21st to end	Night	10% 4 13% 32% 35% 5%	631
October	1st to 10th	Night	10% 3 15% 36% 33% 4	760
	11th to 20th	Night	14% 5% 23% 38% 19% 1	760
	21st to end	Night	20% 7% 26% 29% 17% 1	836
November	1st to 10th	Night	15% 6% 27% 34% 17% 1	780
	11th to 20th	Night	14% 10% 28% 36% 13%	800
	21st to end	Night	20% 10% 29% 29% 11% 1	873
December	1st to 10th	Night	22% 10% 31% 30% 6%	1000
	11th to 20th	Night	26% 9% 29% 31% 7%	1000
	21st to end	Night	24% 12% 29% 28% 6%	1100

Page generated at 2025-02-18 02:26:28. Version ac07

Copyright © 2025 Attilla Danko.