Just a Camp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Just a Camp Observatory clear sky chart from 2005-11-06 to 2026-06-01.

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% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	132086
	Night	17% 14% 5% 10% 6% 5% 4 3 4 5% 26%	131079
Transparency	Day	55% 6% 11% 19% 9% 1	135555
	Night	61% 5% 9% 16% 8% 1	135697
Seeing	Day	26% 17% 29% 19% 8% 2	16600
	Night	26% 14% 26% 24% 9% 1	25635

By Month

Percentage Cloud Cover NE (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	13% 18% 8% 17% 7% 6% 4 3 4 4 15%	4661
	11th to 20th	Day	10% 17% 8% 19% 8% 5% 5% 3 4 4 17%	4650
	21st to end	Day	11% 15% 6% 11% 9% 8% 6% 4 5% 5% 20%	5124
February	1st to 10th	Day	14% 14% 4 12% 8% 8% 5% 4 5% 5% 21%	1852
	11th to 20th	Day	12% 16% 6% 14% 7% 5% 5% 4 5% 6% 23%	1995
	21st to end	Day	16% 15% 5% 11% 7% 5% 4 3 5% 5% 24%	1730
March	1st to 10th	Day	20% 13% 5% 12% 6% 4 4 3 4 5% 24%	4576
	11th to 20th	Day	13% 16% 4 9% 5% 5% 5% 4 5% 5% 28%	4790
	21st to end	Day	19% 12% 4 9% 4 4 4 3 4 5% 31%	6102
April	1st to 10th	Day	20% 13% 3 8% 5% 5% 4 3 5% 6% 29%	2520
	11th to 20th	Day	18% 9% 3 8% 7% 5% 4 3 3 4 35%	2494
	21st to end	Day	21% 10% 4 6% 4 4 4 3 4 6% 33%	2689
May	1st to 10th	Day	28% 11% 3 9% 5% 5% 4 3 4 6% 22%	6249
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	6458
	21st to end	Day	19% 9% 3 6% 4 4 5% 4 6% 7% 31%	7103
June	1st to 10th	Day	22% 7% 2 6% 5% 5% 5% 4 7% 7% 30%	2800
	11th to 20th	Day	14% 6% 2 7% 4 4 4 5% 7% 9% 37%	2800
	21st to end	Day	19% 7% 3 8% 5% 5% 4 4 6% 8% 31%	2800
July	1st to 10th	Day	11% 6% 2 7% 6% 6% 6% 5% 8% 9% 33%	6360
	11th to 20th	Day	11% 6% 2 6% 4 5% 6% 5% 7% 10% 37%	6360
	21st to end	Day	13% 5% 2 5% 4 4 5% 4 6% 9% 42%	6926
August	1st to 10th	Day	14% 8% 3 7% 5% 5% 6% 4 7% 8% 33%	4563
	11th to 20th	Day	13% 7% 3 8% 5% 5% 5% 4 6% 7% 37%	4051
	21st to end	Day	13% 5% 2 7% 4 4 4 4 6% 9% 41%	4312
September	1st to 10th	Day	13% 6% 2 5% 4 4 3 4 6% 7% 46%	2400
	11th to 20th	Day	14% 6% 1 5% 4 4 4 3 4 6% 50%	2295
	21st to end	Day	15% 5% 3 6% 5% 5% 5% 3 6% 9% 40%	2200
October	1st to 10th	Day	20% 7% 3 7% 5% 5% 5% 3 5% 6% 34%	2100
	11th to 20th	Day	19% 9% 3 6% 6% 4 5% 4 6% 7% 32%	1950
	21st to end	Day	23% 13% 4 8% 5% 5% 4 3 4 4 26%	1980
November	1st to 10th	Day	19% 14% 3 8% 5% 4 4 3 5% 5% 29%	1851
	11th to 20th	Day	17% 16% 3 9% 6% 5% 4 4 4 5% 26%	1871
	21st to end	Day	19% 17% 5% 9% 6% 4 5% 4 5% 4 21%	1680
December	1st to 10th	Day	17% 19% 7% 15% 7% 6% 5% 3 5% 4 11%	2680
	11th to 20th	Day	18% 14% 4 11% 5% 5% 5% 4 5% 5% 23%	3066
	21st to end	Day	20% 15% 5% 11% 7% 4 5% 5% 5% 5% 16%	4048
January	1st to 10th	Night	13% 23% 10% 16% 6% 4 3 2 3 4 17%	8234
	11th to 20th	Night	12% 21% 9% 19% 8% 5% 4 3 4 3 13%	8235
	21st to end	Night	11% 16% 5% 14% 11% 7% 6% 3 4 5% 18%	9057
February	1st to 10th	Night	14% 15% 6% 15% 8% 6% 4 3 5% 4 20%	2767
	11th to 20th	Night	13% 15% 6% 14% 7% 6% 4 4 5% 4 22%	2511
	21st to end	Night	16% 16% 5% 12% 6% 4 3 3 4 4 27%	2076
March	1st to 10th	Night	19% 17% 5% 10% 6% 4 3 3 4 4 24%	5484
	11th to 20th	Night	16% 16% 4 9% 5% 4 4 3 5% 6% 28%	5387
	21st to end	Night	18% 18% 5% 11% 5% 4 4 3 3 3 27%	5072
April	1st to 10th	Night	21% 12% 5% 8% 5% 4 4 4 4 5% 27%	2100
	11th to 20th	Night	24% 13% 3 8% 5% 4 4 3 4 4 29%	2075
	21st to end	Night	20% 13% 3 7% 4 4 4 3 4 5% 34%	1929
May	1st to 10th	Night	26% 13% 4 8% 5% 4 4 3 4 6% 22%	3942
	11th to 20th	Night	20% 11% 4 9% 4 4 4 3 5% 6% 30%	3655
	21st to end	Night	19% 9% 3 8% 5% 5% 4 3 6% 7% 31%	4014
June	1st to 10th	Night	24% 8% 2 7% 4 4 4 4 5% 8% 31%	1600
	11th to 20th	Night	15% 7% 3 7% 5% 4 4 3 6% 10% 36%	1600
	21st to end	Night	18% 8% 2 7% 5% 4 6% 4 6% 7% 35%	1600
July	1st to 10th	Night	12% 7% 3 7% 5% 5% 5% 5% 7% 10% 34%	3600
	11th to 20th	Night	14% 6% 2 7% 5% 5% 5% 4 5% 7% 39%	3600
	21st to end	Night	11% 8% 2 8% 5% 4 6% 4 6% 7% 39%	3926
August	1st to 10th	Night	18% 7% 3 7% 5% 5% 3 3 6% 7% 36%	2586
	11th to 20th	Night	13% 8% 3 9% 6% 5% 5% 3 4 6% 37%	2961
	21st to end	Night	14% 6% 2 5% 4 4 5% 4 5% 8% 41%	3586
September	1st to 10th	Night	13% 6% 3 6% 5% 4 5% 4 5% 6% 44%	2000
	11th to 20th	Night	13% 6% 2 5% 4 4 3 3 5% 6% 49%	2105
	21st to end	Night	17% 6% 2 5% 4 3 5% 4 5% 6% 43%	2200
October	1st to 10th	Night	20% 8% 2 7% 5% 4 4 3 5% 7% 35%	2298
	11th to 20th	Night	22% 9% 3 7% 4 4 4 4 5% 6% 32%	2448
	21st to end	Night	24% 12% 3 8% 5% 4 5% 3 4 4 27%	2860
November	1st to 10th	Night	22% 10% 4 9% 4 4 4 3 4 5% 31%	2667
	11th to 20th	Night	18% 14% 4 9% 5% 4 4 4 3 6% 29%	2746
	21st to end	Night	20% 17% 5% 11% 5% 4 4 3 4 5% 21%	2940
December	1st to 10th	Night	18% 28% 8% 13% 5% 5% 3 3 4 3 12%	4720
	11th to 20th	Night	23% 18% 5% 11% 5% 5% 4 3 3 3 19%	5348
	21st to end	Night	21% 17% 7% 12% 6% 5% 5% 3 4 6% 15%	7150

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	74% 5% 8% 11% 2	4662
	11th to 20th	Day	72% 4 7% 10% 5% 1	4680
	21st to end	Day	68% 6% 7% 11% 8% 1	5124
February	1st to 10th	Day	65% 6% 7% 14% 6% 2	1852
	11th to 20th	Day	65% 6% 9% 15% 5%	2004
	21st to end	Day	65% 6% 8% 12% 8% 2	1730
March	1st to 10th	Day	65% 7% 7% 10% 7% 3	4579
	11th to 20th	Day	58% 5% 13% 13% 10% 1	4790
	21st to end	Day	58% 4 7% 13% 16% 2	6102
April	1st to 10th	Day	58% 5% 7% 18% 10% 2	2520
	11th to 20th	Day	54% 5% 7% 18% 14% 1	2494
	21st to end	Day	55% 5% 8% 18% 12% 2	2689
May	1st to 10th	Day	64% 7% 7% 15% 6% 1	6260
	11th to 20th	Day	52% 8% 13% 17% 9% 1	6462
	21st to end	Day	50% 8% 12% 22% 8% 1	7103
June	1st to 10th	Day	52% 9% 10% 17% 10% 1	2800
	11th to 20th	Day	44% 8% 12% 22% 12% 2	2800
	21st to end	Day	52% 8% 10% 20% 9% 1	2800
July	1st to 10th	Day	46% 4 15% 25% 10%	6290
	11th to 20th	Day	42% 6% 13% 29% 10%	6285
	21st to end	Day	40% 5% 11% 35% 8%	6728
August	1st to 10th	Day	48% 6% 14% 23% 8%	4549
	11th to 20th	Day	47% 7% 15% 24% 6%	4091
	21st to end	Day	40% 6% 17% 23% 14% 1	4312
September	1st to 10th	Day	37% 9% 10% 30% 13% 1	2400
	11th to 20th	Day	37% 6% 10% 32% 15% 1	2295
	21st to end	Day	43% 9% 14% 23% 10% 2	2200
October	1st to 10th	Day	46% 4 11% 29% 10%	3425
	11th to 20th	Day	49% 5% 14% 21% 10%	3153
	21st to end	Day	51% 5% 13% 24% 6% 1	3180
November	1st to 10th	Day	57% 7% 11% 17% 7%	1851
	11th to 20th	Day	61% 6% 10% 13% 8% 1	1871
	21st to end	Day	66% 7% 11% 11% 4	1680
December	1st to 10th	Day	79% 4 7% 7% 2	2680
	11th to 20th	Day	67% 5% 7% 16% 5%	3066
	21st to end	Day	69% 6% 7% 11% 6%	4048
January	1st to 10th	Night	75% 4 9% 8% 3	8234
	11th to 20th	Night	76% 5% 7% 7% 4 1	8280
	21st to end	Night	73% 4 6% 8% 8%	9057
February	1st to 10th	Night	69% 5% 7% 12% 5% 1	2767
	11th to 20th	Night	66% 5% 9% 13% 6%	2513
	21st to end	Night	63% 4 8% 15% 8% 1	2076
March	1st to 10th	Night	66% 4 8% 11% 10% 1	5494
	11th to 20th	Night	58% 4 14% 14% 8% 1	5388
	21st to end	Night	64% 3 5% 14% 13% 1	5072
April	1st to 10th	Night	60% 4 7% 16% 11% 1	2100
	11th to 20th	Night	59% 5% 8% 16% 12% 1	2075
	21st to end	Night	54% 5% 8% 16% 14% 3	1929
May	1st to 10th	Night	64% 6% 8% 14% 7% 1	3948
	11th to 20th	Night	55% 6% 10% 19% 9% 1	3656
	21st to end	Night	52% 7% 10% 19% 10% 1	4015
June	1st to 10th	Night	53% 8% 9% 19% 10% 1	1600
	11th to 20th	Night	46% 6% 12% 21% 12% 2	1600
	21st to end	Night	49% 9% 11% 20% 9% 1	1600
July	1st to 10th	Night	45% 4 18% 24% 9%	3560
	11th to 20th	Night	46% 4 12% 26% 11%	3552
	21st to end	Night	45% 5% 12% 28% 10%	3809
August	1st to 10th	Night	49% 6% 13% 23% 8%	2576
	11th to 20th	Night	48% 6% 15% 21% 9% 1	2987
	21st to end	Night	42% 5% 15% 24% 14% 1	3586
September	1st to 10th	Night	40% 8% 11% 28% 12% 1	2000
	11th to 20th	Night	37% 6% 13% 31% 13%	2105
	21st to end	Night	42% 8% 11% 24% 14% 2	2200
October	1st to 10th	Night	56% 4 8% 23% 10%	3753
	11th to 20th	Night	52% 4 11% 22% 11%	3984
	21st to end	Night	54% 4 11% 22% 8% 1	4610
November	1st to 10th	Night	56% 6% 11% 18% 8% 1	2667
	11th to 20th	Night	59% 6% 10% 15% 7% 2	2746
	21st to end	Night	66% 7% 11% 13% 3	2940
December	1st to 10th	Night	83% 3 6% 6% 1	4720
	11th to 20th	Night	71% 5% 7% 10% 7%	5348
	21st to end	Night	72% 5% 6% 11% 6%	7150

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% 23% 29% 18% 3	220
	11th to 20th	Day	31% 28% 30% 6% 3 1	220
	21st to end	Day	26% 23% 35% 12% 4	242
February	1st to 10th	Day	31% 29% 28% 10% 2	311
	11th to 20th	Day	27% 27% 34% 9% 2	483
	21st to end	Day	31% 21% 35% 11% 2	446
March	1st to 10th	Day	32% 19% 29% 16% 3	540
	11th to 20th	Day	29% 26% 28% 14% 4 1	540
	21st to end	Day	34% 22% 25% 12% 6% 1	594
April	1st to 10th	Day	37% 19% 24% 15% 5% 1	540
	11th to 20th	Day	35% 23% 20% 13% 6% 2	532
	21st to end	Day	30% 21% 28% 13% 6% 1	540
May	1st to 10th	Day	32% 18% 26% 15% 7% 1	543
	11th to 20th	Day	23% 16% 32% 22% 7% 1	567
	21st to end	Day	21% 18% 32% 20% 8% 1	617
June	1st to 10th	Day	28% 13% 32% 20% 7% 1	530
	11th to 20th	Day	19% 15% 34% 21% 9% 2	530
	21st to end	Day	23% 15% 32% 21% 8% 1	530
July	1st to 10th	Day	17% 10% 31% 29% 11% 3	525
	11th to 20th	Day	14% 9% 34% 29% 12% 2	524
	21st to end	Day	19% 7% 34% 30% 10% 1	576
August	1st to 10th	Day	15% 9% 28% 28% 17% 2	526
	11th to 20th	Day	18% 9% 24% 29% 14% 5%	519
	21st to end	Day	16% 14% 28% 26% 11% 5%	583
September	1st to 10th	Day	17% 14% 29% 23% 12% 5%	530
	11th to 20th	Day	16% 13% 20% 23% 20% 8%	530
	21st to end	Day	16% 14% 30% 22% 14% 5%	530
October	1st to 10th	Day	26% 13% 26% 17% 15% 4	530
	11th to 20th	Day	29% 16% 26% 20% 7% 1	502
	21st to end	Day	38% 16% 25% 17% 3	462
November	1st to 10th	Day	34% 18% 26% 16% 5%	425
	11th to 20th	Day	32% 25% 22% 14% 6% 1	411
	21st to end	Day	39% 21% 27% 12% 1	220
December	1st to 10th	Day	28% 25% 29% 17% 2	220
	11th to 20th	Day	31% 27% 31% 9% 1	220
	21st to end	Day	29% 26% 30% 12% 3	242
January	1st to 10th	Night	29% 20% 32% 16% 3	840
	11th to 20th	Night	31% 19% 29% 17% 4	840
	21st to end	Night	23% 18% 31% 24% 5% 1	924
February	1st to 10th	Night	23% 17% 34% 23% 3	840
	11th to 20th	Night	26% 19% 33% 19% 3	823
	21st to end	Night	27% 18% 29% 21% 5%	692
March	1st to 10th	Night	30% 16% 27% 23% 3	840
	11th to 20th	Night	28% 22% 25% 19% 5%	840
	21st to end	Night	32% 16% 25% 19% 7% 1	924
April	1st to 10th	Night	30% 15% 26% 24% 4	840
	11th to 20th	Night	33% 17% 22% 21% 7%	831
	21st to end	Night	27% 18% 26% 21% 7%	669
May	1st to 10th	Night	31% 11% 25% 24% 8% 1	545
	11th to 20th	Night	24% 9% 33% 24% 8% 1	414
	21st to end	Night	20% 9% 28% 33% 10% 1	455
June	1st to 10th	Night	27% 7% 27% 31% 8% 1	400
	11th to 20th	Night	19% 7% 28% 33% 13% 1	400
	21st to end	Night	22% 5% 26% 37% 10% 1	400
July	1st to 10th	Night	16% 3 23% 43% 15% 1	390
	11th to 20th	Night	12% 4 23% 42% 18% 2	388
	21st to end	Night	16% 6% 21% 42% 15%	438
August	1st to 10th	Night	16% 4 17% 41% 22% 1	398
	11th to 20th	Night	18% 4 20% 33% 23% 3	640
	21st to end	Night	16% 7% 23% 32% 21% 1	880
September	1st to 10th	Night	17% 8% 24% 34% 16% 2	800
	11th to 20th	Night	18% 8% 17% 30% 23% 4	800
	21st to end	Night	21% 9% 27% 25% 17% 2	800
October	1st to 10th	Night	28% 11% 20% 25% 15% 1	800
	11th to 20th	Night	31% 11% 23% 26% 8% 1	800
	21st to end	Night	32% 15% 27% 21% 5%	880
November	1st to 10th	Night	31% 17% 25% 20% 6% 1	820
	11th to 20th	Night	31% 16% 27% 17% 8% 1	840
	21st to end	Night	33% 20% 26% 17% 4 1	840
December	1st to 10th	Night	34% 19% 28% 14% 4	840
	11th to 20th	Night	29% 22% 28% 17% 4	840
	21st to end	Night	33% 17% 29% 17% 3	924

Page generated at 2026-05-29 01:53:30. Version ac07

Copyright © 2026 Attilla Danko.