Hodgson Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hodgson Observatory clear sky chart from 2005-11-06 to 2025-01-07.

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	12% 7% 3 7% 4 4 4 3 5% 7% 42%	105017
	Night	10% 7% 3 7% 4 4 4 4 5% 7% 45%	104095
Transparency	Day	40% 6% 13% 25% 14% 2	108648
	Night	38% 6% 13% 25% 16% 2	108595
Seeing	Day	15% 10% 31% 29% 13% 3	16102
	Night	14% 9% 34% 34% 10% 1	26087

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	9% 13% 4 14% 8% 7% 7% 4 6% 5% 23%	2530
	11th to 20th	Day	7% 14% 5% 10% 6% 5% 8% 3 7% 9% 26%	2763
	21st to end	Day	6% 12% 5% 16% 9% 8% 6% 4 5% 6% 24%	3135
February	1st to 10th	Day	10% 11% 4 11% 7% 8% 7% 3 4 6% 29%	1710
	11th to 20th	Day	10% 11% 4 8% 6% 5% 4 3 6% 6% 37%	1692
	21st to end	Day	12% 11% 3 8% 7% 5% 4 3 6% 6% 35%	1570
March	1st to 10th	Day	12% 9% 4 8% 3 3 3 3 4 6% 44%	3316
	11th to 20th	Day	10% 9% 3 7% 4 4 4 3 4 7% 46%	3480
	21st to end	Day	25% 11% 4 11% 5% 4 4 3 4 5% 24%	3814
April	1st to 10th	Day	15% 9% 3 7% 5% 3 5% 3 6% 5% 39%	2137
	11th to 20th	Day	18% 10% 3 6% 4 4 4 3 5% 5% 38%	2441
	21st to end	Day	22% 7% 3 5% 3 4 4 4 4 6% 38%	2470
May	1st to 10th	Day	16% 7% 2 7% 4 5% 5% 4 6% 7% 36%	4082
	11th to 20th	Day	11% 6% 2 5% 4 4 3 3 4 7% 50%	4082
	21st to end	Day	17% 6% 2 6% 4 4 4 3 5% 7% 41%	4752
June	1st to 10th	Day	11% 5% 2 5% 4 3 4 4 6% 8% 49%	2705
	11th to 20th	Day	14% 5% 2 5% 4 4 5% 4 6% 7% 45%	2850
	21st to end	Day	9% 5% 1 5% 4 4 4 4 7% 9% 49%	2850
July	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 6% 10% 43%	4666
	11th to 20th	Day	7% 4 2 4 3 3 3 3 5% 7% 59%	4289
	21st to end	Day	4 3 1 5% 3 4 4 4 7% 10% 55%	4465
August	1st to 10th	Day	7% 5% 2 6% 4 4 4 4 6% 8% 48%	4104
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 6% 7% 39%	4041
	21st to end	Day	9% 5% 1 5% 3 4 4 3 5% 7% 53%	4532
September	1st to 10th	Day	14% 4 2 5% 3 4 3 3 4 6% 52%	2200
	11th to 20th	Day	10% 5% 2 5% 3 4 3 3 4 6% 55%	2090
	21st to end	Day	10% 4 2 5% 3 3 3 4 5% 6% 56%	2090
October	1st to 10th	Day	15% 5% 2 5% 3 4 3 2 4 5% 50%	1962
	11th to 20th	Day	13% 6% 2 4 3 2 3 3 4 6% 53%	1900
	21st to end	Day	16% 7% 2 7% 4 3 3 3 4 5% 47%	2024
November	1st to 10th	Day	10% 6% 3 6% 4 4 3 4 6% 6% 48%	1763
	11th to 20th	Day	8% 10% 2 9% 5% 4 4 3 4 6% 44%	1681
	21st to end	Day	11% 9% 3 8% 4 4 3 4 6% 7% 41%	1600
December	1st to 10th	Day	5% 7% 3 9% 6% 6% 5% 4 7% 7% 43%	2610
	11th to 20th	Day	9% 12% 4 11% 5% 6% 5% 5% 6% 6% 32%	3008
	21st to end	Day	14% 11% 4 14% 5% 5% 4 3 5% 8% 28%	3613
January	1st to 10th	Night	9% 12% 4 14% 9% 6% 6% 4 5% 6% 25%	4553
	11th to 20th	Night	5% 10% 4 9% 7% 5% 8% 5% 9% 7% 30%	4201
	21st to end	Night	6% 12% 7% 13% 5% 5% 5% 4 5% 7% 30%	4532
February	1st to 10th	Night	10% 11% 4 8% 5% 4 4 3 6% 6% 38%	2470
	11th to 20th	Night	9% 10% 4 8% 4 4 4 4 5% 6% 42%	2391
	21st to end	Night	9% 9% 3 6% 4 4 4 4 6% 6% 44%	1884
March	1st to 10th	Night	10% 6% 2 6% 4 3 3 3 4 6% 52%	3542
	11th to 20th	Night	10% 7% 3 5% 3 4 3 3 5% 7% 50%	3480
	21st to end	Night	22% 11% 3 9% 5% 5% 4 3 5% 6% 28%	3817
April	1st to 10th	Night	14% 7% 3 7% 4 4 4 3 6% 6% 41%	2041
	11th to 20th	Night	15% 9% 3 6% 4 3 3 3 6% 6% 43%	1689
	21st to end	Night	19% 7% 2 5% 3 4 4 3 5% 7% 41%	1710
May	1st to 10th	Night	18% 6% 2 5% 3 4 3 3 5% 6% 46%	2823
	11th to 20th	Night	9% 4 2 6% 4 3 4 4 5% 8% 50%	2823
	21st to end	Night	14% 5% 2 5% 5% 4 4 4 5% 7% 45%	2813
June	1st to 10th	Night	7% 5% 1 4 3 4 3 4 6% 9% 54%	1470
	11th to 20th	Night	9% 4 2 4 3 3 3 4 8% 8% 52%	1330
	21st to end	Night	8% 2 1 3 3 3 4 4 6% 9% 56%	1330
July	1st to 10th	Night	8% 5% 2 5% 4 4 3 3 5% 7% 53%	2300
	11th to 20th	Night	6% 3 1 2 3 2 3 3 6% 7% 65%	2664
	21st to end	Night	2 3 1 4 3 3 4 4 7% 10% 60%	3098
August	1st to 10th	Night	6% 5% 2 5% 4 4 4 4 6% 8% 50%	2836
	11th to 20th	Night	10% 5% 2 4 3 4 4 3 6% 8% 51%	2798
	21st to end	Night	7% 4 2 5% 3 3 4 3 6% 9% 54%	3135
September	1st to 10th	Night	9% 4 2 4 3 3 3 3 5% 6% 59%	1975
	11th to 20th	Night	9% 3 2 4 3 3 3 3 6% 7% 58%	2090
	21st to end	Night	9% 4 1 3 3 2 3 3 4 7% 60%	2090
October	1st to 10th	Night	17% 4 1 4 3 3 2 3 5% 4 54%	2199
	11th to 20th	Night	12% 6% 3 4 3 2 3 3 4 6% 54%	2280
	21st to end	Night	14% 6% 2 5% 3 3 4 3 4 6% 50%	2571
November	1st to 10th	Night	9% 5% 2 5% 4 3 4 3 6% 6% 53%	2535
	11th to 20th	Night	9% 6% 2 8% 4 3 4 4 5% 6% 49%	2715
	21st to end	Night	9% 8% 2 6% 4 4 4 4 6% 7% 48%	2800
December	1st to 10th	Night	5% 7% 4 8% 5% 4 4 4 5% 6% 46%	4580
	11th to 20th	Night	10% 8% 3 9% 8% 6% 5% 4 6% 7% 35%	5199
	21st to end	Night	15% 13% 4 14% 6% 4 4 3 5% 5% 28%	7331

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	62% 5% 13% 15% 6%	2531
	11th to 20th	Day	55% 4 10% 25% 6%	2763
	21st to end	Day	58% 8% 14% 13% 6%	3135
February	1st to 10th	Day	56% 5% 14% 16% 9%	1710
	11th to 20th	Day	47% 5% 14% 21% 11% 1	1701
	21st to end	Day	49% 6% 12% 21% 11% 2	1570
March	1st to 10th	Day	42% 6% 10% 32% 10% 1	3316
	11th to 20th	Day	39% 5% 9% 31% 12% 3	3480
	21st to end	Day	62% 6% 13% 14% 3 1	3814
April	1st to 10th	Day	46% 5% 12% 25% 11% 2	2137
	11th to 20th	Day	46% 5% 11% 21% 15% 2	2441
	21st to end	Day	47% 5% 11% 23% 12% 1	2470
May	1st to 10th	Day	44% 8% 11% 23% 14% 1	4120
	11th to 20th	Day	34% 6% 12% 28% 18% 3	4086
	21st to end	Day	42% 7% 11% 24% 15% 1	4765
June	1st to 10th	Day	32% 7% 15% 30% 13% 2	2705
	11th to 20th	Day	37% 7% 13% 24% 16% 3	2850
	21st to end	Day	31% 6% 15% 31% 13% 3	2850
July	1st to 10th	Day	35% 8% 18% 25% 13% 1	4594
	11th to 20th	Day	25% 6% 13% 34% 18% 4	4214
	21st to end	Day	22% 8% 17% 29% 21% 2	4325
August	1st to 10th	Day	33% 7% 14% 31% 15% 2	4090
	11th to 20th	Day	43% 7% 13% 27% 9%	4080
	21st to end	Day	30% 7% 15% 28% 17% 3	4531
September	1st to 10th	Day	34% 5% 9% 30% 19% 2	2200
	11th to 20th	Day	29% 6% 14% 32% 17% 1	2090
	21st to end	Day	28% 7% 11% 30% 22% 2	2090
October	1st to 10th	Day	24% 3 7% 26% 36% 4	3261
	11th to 20th	Day	27% 4 15% 27% 21% 6%	3140
	21st to end	Day	37% 4 13% 26% 17% 3	3317
November	1st to 10th	Day	35% 5% 17% 25% 15% 2	1763
	11th to 20th	Day	41% 5% 14% 24% 14% 1	1681
	21st to end	Day	42% 5% 16% 24% 14% 1	1600
December	1st to 10th	Day	38% 6% 17% 27% 10% 1	2610
	11th to 20th	Day	51% 7% 16% 19% 6%	3005
	21st to end	Day	54% 5% 13% 20% 6% 1	3613
January	1st to 10th	Night	58% 6% 11% 18% 7%	4553
	11th to 20th	Night	49% 5% 14% 22% 7% 2	4201
	21st to end	Night	52% 8% 14% 17% 8%	4532
February	1st to 10th	Night	47% 5% 13% 24% 11% 1	2470
	11th to 20th	Night	43% 5% 13% 24% 13% 3	2392
	21st to end	Night	40% 5% 13% 25% 14% 3	1884
March	1st to 10th	Night	34% 5% 11% 27% 22% 2	3542
	11th to 20th	Night	33% 5% 10% 29% 18% 4	3480
	21st to end	Night	57% 8% 15% 15% 5% 1	3817
April	1st to 10th	Night	42% 6% 13% 22% 15% 1	2041
	11th to 20th	Night	42% 5% 9% 25% 18% 2	1689
	21st to end	Night	43% 5% 12% 24% 14% 2	1710
May	1st to 10th	Night	38% 7% 12% 21% 20% 2	2850
	11th to 20th	Night	30% 7% 12% 26% 21% 4	2824
	21st to end	Night	38% 7% 11% 27% 16% 2	2821
June	1st to 10th	Night	25% 7% 16% 29% 18% 4	1470
	11th to 20th	Night	27% 6% 17% 25% 20% 5%	1330
	21st to end	Night	24% 7% 16% 30% 21% 3	1330
July	1st to 10th	Night	30% 7% 20% 28% 12% 3	2263
	11th to 20th	Night	19% 5% 14% 38% 20% 4	2616
	21st to end	Night	17% 8% 19% 30% 22% 4	2999
August	1st to 10th	Night	29% 7% 15% 31% 16% 3	2826
	11th to 20th	Night	31% 8% 17% 29% 14% 2	2825
	21st to end	Night	27% 7% 17% 24% 22% 4	3135
September	1st to 10th	Night	26% 5% 12% 28% 23% 5%	1975
	11th to 20th	Night	25% 6% 13% 33% 20% 2	2090
	21st to end	Night	24% 6% 9% 34% 24% 3	2090
October	1st to 10th	Night	21% 3 6% 21% 46% 3	3667
	11th to 20th	Night	24% 3 12% 31% 26% 4	3779
	21st to end	Night	37% 5% 12% 30% 16% 1	4232
November	1st to 10th	Night	30% 5% 15% 24% 21% 4	2535
	11th to 20th	Night	35% 5% 14% 25% 18% 2	2715
	21st to end	Night	34% 6% 15% 29% 16% 1	2800
December	1st to 10th	Night	37% 5% 15% 32% 10%	4580
	11th to 20th	Night	47% 6% 17% 23% 7%	5201
	21st to end	Night	57% 5% 11% 20% 7%	7331

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	14% 13% 33% 25% 11% 4	288
	11th to 20th	Day	19% 11% 33% 30% 7% 1	270
	21st to end	Day	14% 9% 36% 29% 11% 1	297
February	1st to 10th	Day	12% 19% 38% 29% 3	270
	11th to 20th	Day	15% 14% 39% 26% 5% 1	270
	21st to end	Day	20% 12% 41% 21% 6%	225
March	1st to 10th	Day	16% 16% 38% 26% 3 1	270
	11th to 20th	Day	20% 11% 37% 22% 8% 1	270
	21st to end	Day	29% 12% 38% 16% 4 1	297
April	1st to 10th	Day	24% 16% 38% 19% 4	317
	11th to 20th	Day	24% 16% 31% 22% 6%	639
	21st to end	Day	25% 14% 31% 20% 9% 2	650
May	1st to 10th	Day	20% 13% 30% 27% 8% 2	653
	11th to 20th	Day	20% 10% 29% 26% 13% 3	675
	21st to end	Day	20% 8% 30% 27% 11% 2	734
June	1st to 10th	Day	9% 7% 22% 36% 21% 4	680
	11th to 20th	Day	13% 6% 34% 30% 14% 2	680
	21st to end	Day	10% 8% 31% 34% 16% 2	680
July	1st to 10th	Day	7% 3 18% 39% 25% 7%	671
	11th to 20th	Day	8% 4 28% 35% 21% 4	668
	21st to end	Day	5% 3 26% 41% 22% 4	739
August	1st to 10th	Day	10% 4 22% 39% 21% 4	676
	11th to 20th	Day	13% 4 22% 34% 22% 5%	665
	21st to end	Day	8% 4 27% 35% 22% 4	748
September	1st to 10th	Day	16% 5% 27% 31% 15% 5%	410
	11th to 20th	Day	8% 4 37% 31% 16% 4	300
	21st to end	Day	14% 12% 34% 24% 12% 4	300
October	1st to 10th	Day	18% 8% 27% 29% 13% 4	300
	11th to 20th	Day	15% 18% 34% 23% 9% 1	300
	21st to end	Day	20% 15% 37% 21% 7%	330
November	1st to 10th	Day	19% 12% 32% 26% 8% 3	300
	11th to 20th	Day	15% 18% 40% 20% 6%	300
	21st to end	Day	18% 16% 32% 24% 9% 1	300
December	1st to 10th	Day	11% 11% 39% 27% 10% 1	300
	11th to 20th	Day	14% 16% 41% 23% 7%	300
	21st to end	Day	23% 13% 35% 24% 4	330
January	1st to 10th	Night	13% 10% 37% 30% 9% 1	981
	11th to 20th	Night	12% 13% 35% 33% 7% 1	950
	21st to end	Night	15% 10% 38% 29% 7%	1045
February	1st to 10th	Night	15% 10% 40% 29% 6%	950
	11th to 20th	Night	15% 12% 38% 29% 6%	917
	21st to end	Night	14% 9% 38% 31% 7% 1	628
March	1st to 10th	Night	13% 10% 39% 31% 7%	646
	11th to 20th	Night	17% 11% 37% 31% 5%	570
	21st to end	Night	20% 12% 36% 23% 7% 1	627
April	1st to 10th	Night	19% 14% 39% 26% 3	570
	11th to 20th	Night	20% 14% 35% 25% 5% 1	563
	21st to end	Night	22% 9% 33% 26% 8% 1	570
May	1st to 10th	Night	18% 8% 35% 31% 8% 1	570
	11th to 20th	Night	16% 9% 31% 33% 12%	561
	21st to end	Night	16% 6% 32% 35% 10%	617
June	1st to 10th	Night	8% 5% 26% 44% 15% 1	570
	11th to 20th	Night	11% 4 35% 38% 13%	570
	21st to end	Night	7% 4 27% 45% 16%	570
July	1st to 10th	Night	5% 3 20% 44% 27%	555
	11th to 20th	Night	4 2 23% 53% 18% 1	552
	21st to end	Night	4 2 21% 55% 18%	624
August	1st to 10th	Night	8% 3 22% 44% 22% 1	567
	11th to 20th	Night	7% 4 23% 43% 22% 1	564
	21st to end	Night	6% 2 27% 43% 19% 2	627
September	1st to 10th	Night	9% 5% 26% 42% 17% 1	570
	11th to 20th	Night	9% 6% 31% 40% 13% 2	570
	21st to end	Night	10% 5% 37% 34% 13% 1	570
October	1st to 10th	Night	18% 7% 32% 31% 11% 1	679
	11th to 20th	Night	15% 12% 35% 31% 6% 1	760
	21st to end	Night	17% 12% 32% 29% 9%	899
November	1st to 10th	Night	12% 10% 38% 31% 9% 1	975
	11th to 20th	Night	14% 11% 40% 29% 6%	1000
	21st to end	Night	12% 9% 37% 33% 8%	1000
December	1st to 10th	Night	14% 11% 38% 32% 6%	1000
	11th to 20th	Night	17% 7% 35% 32% 8% 1	1000
	21st to end	Night	21% 11% 35% 27% 6%	1100

Page generated at 2025-01-04 02:24:00. Version ac07

Copyright © 2025 Attilla Danko.