Spring Hope Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spring Hope Observing Site clear sky chart from 2005-11-06 to 2026-09-14.

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% 6% 2 6% 4 4 5% 4 6% 8% 42%	147802
	Night	13% 7% 2 6% 4 4 4 4 5% 7% 44%	143264
Transparency	Day	38% 6% 13% 21% 17% 5%	151404
	Night	39% 6% 11% 20% 19% 6%	147734
Seeing	Day	17% 11% 26% 25% 16% 6%	17789
	Night	16% 9% 28% 30% 15% 2	27821

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	14% 5% 2 5% 3 3 2 2 3 6% 54%	5258
	11th to 20th	Day	13% 6% 2 5% 3 2 2 2 3 4 59%	5280
	21st to end	Day	15% 8% 3 6% 4 4 4 3 5% 5% 44%	5780
February	1st to 10th	Day	14% 6% 3 6% 4 4 4 3 5% 6% 45%	1890
	11th to 20th	Day	21% 6% 2 4 4 3 3 3 4 5% 44%	1904
	21st to end	Day	17% 7% 3 6% 4 3 3 3 4 7% 41%	1824
March	1st to 10th	Day	20% 8% 2 6% 4 4 4 4 5% 6% 39%	5045
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 4 7% 54%	5090
	21st to end	Day	14% 5% 2 5% 4 4 5% 3 5% 6% 47%	5586
April	1st to 10th	Day	11% 4 2 5% 3 4 4 3 6% 7% 52%	2483
	11th to 20th	Day	10% 4 2 5% 4 4 4 4 6% 9% 50%	2494
	21st to end	Day	13% 5% 3 6% 4 3 4 3 6% 8% 45%	2520
May	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 4 7% 10% 37%	7355
	11th to 20th	Day	15% 6% 2 7% 4 4 4 4 5% 8% 40%	7626
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 6% 9% 38%	8391
June	1st to 10th	Day	9% 6% 2 6% 5% 5% 6% 5% 7% 10% 40%	2882
	11th to 20th	Day	8% 4 2 6% 5% 5% 5% 5% 8% 10% 43%	2940
	21st to end	Day	7% 5% 2 5% 5% 6% 6% 4 8% 11% 40%	2764
July	1st to 10th	Day	7% 5% 2 6% 5% 6% 6% 6% 9% 13% 35%	7680
	11th to 20th	Day	11% 7% 2 7% 6% 6% 6% 6% 8% 13% 29%	7680
	21st to end	Day	12% 7% 2 7% 5% 6% 5% 5% 8% 11% 32%	8340
August	1st to 10th	Day	16% 9% 3 9% 5% 6% 6% 6% 9% 11% 20%	6014
	11th to 20th	Day	7% 5% 2 7% 5% 6% 6% 5% 8% 13% 36%	5656
	21st to end	Day	8% 6% 2 6% 4 4 4 4 6% 10% 44%	6080
September	1st to 10th	Day	9% 6% 2 5% 5% 4 6% 4 5% 9% 45%	2520
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 3 6% 7% 41%	2375
	21st to end	Day	19% 7% 3 7% 4 4 4 3 5% 7% 36%	2116
October	1st to 10th	Day	14% 6% 2 6% 4 3 3 3 4 6% 48%	2000
	11th to 20th	Day	13% 5% 2 4 3 3 4 3 4 5% 55%	2000
	21st to end	Day	11% 6% 2 6% 3 4 3 2 4 4 56%	2200
November	1st to 10th	Day	13% 5% 2 4 3 3 3 2 4 6% 54%	2057
	11th to 20th	Day	13% 6% 2 4 4 3 3 3 5% 6% 52%	2047
	21st to end	Day	13% 4 2 5% 4 3 3 3 5% 5% 52%	1727
December	1st to 10th	Day	13% 5% 2 6% 4 3 4 3 4 5% 51%	2680
	11th to 20th	Day	15% 6% 3 6% 4 4 4 3 4 5% 46%	3070
	21st to end	Day	14% 7% 2 6% 3 3 4 3 5% 7% 46%	4448
January	1st to 10th	Night	11% 6% 2 6% 3 3 3 3 5% 6% 52%	7635
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 3 4 56%	7680
	21st to end	Night	17% 7% 2 6% 3 3 3 3 4 5% 46%	8401
February	1st to 10th	Night	17% 6% 2 5% 4 3 4 3 5% 5% 45%	2730
	11th to 20th	Night	20% 6% 3 6% 4 3 4 3 4 5% 42%	2600
	21st to end	Night	15% 7% 2 4 3 3 3 4 6% 6% 46%	1977
March	1st to 10th	Night	18% 8% 2 6% 4 4 4 3 4 5% 42%	5028
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 6% 53%	5090
	21st to end	Night	13% 5% 2 4 3 4 4 3 5% 7% 50%	5588
April	1st to 10th	Night	13% 6% 2 5% 4 4 3 3 6% 7% 49%	2137
	11th to 20th	Night	12% 5% 1 4 4 3 3 3 6% 7% 51%	2075
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 6% 6% 48%	2100
May	1st to 10th	Night	11% 8% 2 8% 5% 5% 5% 4 6% 8% 38%	5539
	11th to 20th	Night	16% 7% 3 7% 4 4 4 3 5% 6% 43%	5234
	21st to end	Night	20% 7% 3 6% 4 4 5% 4 6% 8% 35%	5761
June	1st to 10th	Night	9% 5% 2 6% 6% 5% 6% 7% 7% 9% 40%	1727
	11th to 20th	Night	9% 6% 3 7% 5% 4 5% 5% 7% 9% 39%	1680
	21st to end	Night	7% 5% 2 6% 5% 5% 6% 5% 8% 11% 40%	1843
July	1st to 10th	Night	9% 6% 3 8% 5% 5% 6% 5% 8% 11% 35%	5278
	11th to 20th	Night	14% 8% 3 9% 5% 5% 6% 5% 7% 11% 27%	5277
	21st to end	Night	14% 8% 3 8% 5% 5% 5% 4 7% 10% 30%	5736
August	1st to 10th	Night	18% 9% 3 8% 5% 5% 5% 5% 8% 11% 23%	4135
	11th to 20th	Night	7% 6% 3 8% 6% 6% 6% 5% 8% 11% 35%	4329
	21st to end	Night	9% 7% 2 7% 4 4 5% 3 6% 10% 43%	5045
September	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 6% 9% 48%	2100
	11th to 20th	Night	12% 7% 3 8% 4 4 5% 3 5% 7% 43%	2087
	21st to end	Night	20% 8% 3 7% 4 4 4 4 5% 6% 35%	2282
October	1st to 10th	Night	14% 6% 2 6% 3 4 3 4 5% 5% 48%	2400
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 5% 55%	2400
	21st to end	Night	12% 4 2 5% 3 3 3 2 4 6% 55%	2640
November	1st to 10th	Night	13% 6% 2 5% 3 3 4 3 4 5% 51%	2461
	11th to 20th	Night	13% 5% 2 4 4 3 4 3 5% 6% 50%	2568
	21st to end	Night	12% 5% 2 5% 4 3 4 3 5% 6% 52%	2891
December	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 4 4 52%	4720
	11th to 20th	Night	17% 7% 3 8% 5% 4 3 4 5% 4 40%	5345
	21st to end	Night	13% 6% 2 5% 3 3 4 3 5% 7% 48%	6745

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	35% 2 11% 20% 26% 6%	5259
	11th to 20th	Day	31% 2 4 14% 37% 11%	5280
	21st to end	Day	43% 3 5% 23% 18% 8%	5780
February	1st to 10th	Day	39% 4 11% 21% 19% 5%	1890
	11th to 20th	Day	44% 4 7% 18% 22% 6%	1913
	21st to end	Day	43% 5% 10% 16% 21% 5%	1824
March	1st to 10th	Day	45% 4 7% 17% 16% 10%	5045
	11th to 20th	Day	32% 4 8% 19% 23% 14%	5090
	21st to end	Day	38% 5% 11% 22% 19% 6%	5586
April	1st to 10th	Day	31% 5% 10% 25% 22% 7%	2483
	11th to 20th	Day	32% 5% 13% 23% 21% 5%	2494
	21st to end	Day	38% 5% 13% 23% 17% 4	2520
May	1st to 10th	Day	41% 7% 17% 21% 12% 2	7387
	11th to 20th	Day	42% 6% 12% 25% 15% 1	7630
	21st to end	Day	42% 7% 13% 21% 15% 2	8405
June	1st to 10th	Day	37% 8% 15% 21% 17% 2	2882
	11th to 20th	Day	33% 10% 17% 25% 13% 1	2940
	21st to end	Day	34% 9% 17% 23% 15% 1	2764
July	1st to 10th	Day	36% 10% 19% 26% 7% 2	7615
	11th to 20th	Day	44% 11% 23% 14% 6% 1	7611
	21st to end	Day	44% 9% 16% 19% 12%	8156
August	1st to 10th	Day	53% 12% 21% 11% 3	6001
	11th to 20th	Day	36% 9% 23% 24% 7% 1	5695
	21st to end	Day	34% 7% 14% 31% 13% 1	6080
September	1st to 10th	Day	35% 7% 15% 20% 19% 4	2520
	11th to 20th	Day	41% 6% 11% 20% 19% 3	2375
	21st to end	Day	47% 5% 11% 20% 13% 4	2116
October	1st to 10th	Day	34% 4 10% 21% 25% 7%	3260
	11th to 20th	Day	22% 3 5% 20% 29% 22%	3240
	21st to end	Day	25% 3 7% 25% 27% 14%	3538
November	1st to 10th	Day	33% 4 8% 22% 27% 6%	2057
	11th to 20th	Day	34% 3 10% 21% 25% 7%	2047
	21st to end	Day	34% 4 8% 23% 26% 6%	1727
December	1st to 10th	Day	36% 4 7% 22% 23% 7%	2680
	11th to 20th	Day	42% 4 10% 20% 19% 6%	3066
	21st to end	Day	39% 4 12% 25% 19% 1	4448
January	1st to 10th	Night	33% 3 10% 21% 24% 9%	7636
	11th to 20th	Night	34% 3 5% 16% 34% 10%	7680
	21st to end	Night	42% 3 5% 18% 24% 8%	8401
February	1st to 10th	Night	41% 4 9% 20% 21% 5%	2730
	11th to 20th	Night	45% 4 8% 17% 20% 6%	2602
	21st to end	Night	37% 5% 9% 20% 21% 8%	1977
March	1st to 10th	Night	45% 4 7% 13% 20% 10%	5028
	11th to 20th	Night	33% 4 8% 14% 24% 17%	5090
	21st to end	Night	35% 4 9% 24% 22% 6%	5588
April	1st to 10th	Night	35% 5% 11% 19% 24% 7%	2137
	11th to 20th	Night	32% 5% 11% 23% 22% 6%	2075
	21st to end	Night	34% 7% 11% 26% 18% 4	2100
May	1st to 10th	Night	43% 6% 16% 21% 13% 2	5569
	11th to 20th	Night	42% 5% 11% 22% 18% 1	5235
	21st to end	Night	47% 6% 13% 20% 13% 1	5771
June	1st to 10th	Night	36% 9% 17% 20% 16% 2	1727
	11th to 20th	Night	39% 9% 16% 19% 15% 2	1680
	21st to end	Night	35% 11% 15% 23% 14% 2	1843
July	1st to 10th	Night	40% 11% 17% 22% 9% 1	5235
	11th to 20th	Night	50% 12% 19% 12% 7% 1	5226
	21st to end	Night	47% 9% 15% 17% 11% 1	5606
August	1st to 10th	Night	53% 12% 18% 14% 3	4124
	11th to 20th	Night	40% 10% 21% 23% 6% 1	4356
	21st to end	Night	37% 6% 12% 27% 17% 2	5045
September	1st to 10th	Night	33% 9% 15% 24% 16% 4	2100
	11th to 20th	Night	40% 7% 12% 18% 20% 2	2087
	21st to end	Night	49% 6% 12% 16% 15% 3	2282
October	1st to 10th	Night	39% 4 7% 21% 25% 5%	3920
	11th to 20th	Night	25% 3 6% 17% 27% 21%	3899
	21st to end	Night	23% 3 7% 28% 23% 16%	4252
November	1st to 10th	Night	36% 4 8% 20% 28% 6%	2461
	11th to 20th	Night	34% 5% 8% 17% 25% 11%	2568
	21st to end	Night	33% 4 8% 23% 25% 7%	2891
December	1st to 10th	Night	37% 3 6% 19% 28% 8%	4720
	11th to 20th	Night	46% 4 9% 16% 17% 7%	5348
	21st to end	Night	36% 4 12% 26% 20% 2	6745

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	25% 23% 34% 15% 3	330
	11th to 20th	Day	26% 27% 32% 12% 3	330
	21st to end	Day	21% 23% 41% 13% 2	363
February	1st to 10th	Day	20% 21% 41% 15% 3	330
	11th to 20th	Day	35% 21% 32% 11% 1	391
	21st to end	Day	25% 21% 31% 17% 5%	446
March	1st to 10th	Day	21% 17% 35% 21% 5% 1	540
	11th to 20th	Day	23% 18% 35% 17% 6% 1	540
	21st to end	Day	21% 16% 39% 17% 5% 1	594
April	1st to 10th	Day	19% 17% 35% 22% 6% 1	540
	11th to 20th	Day	14% 17% 32% 26% 10% 2	532
	21st to end	Day	16% 11% 30% 28% 14% 1	540
May	1st to 10th	Day	15% 13% 35% 24% 11% 2	543
	11th to 20th	Day	18% 8% 28% 27% 17% 3	567
	21st to end	Day	19% 7% 23% 23% 21% 8%	617
June	1st to 10th	Day	11% 5% 22% 34% 21% 7%	570
	11th to 20th	Day	9% 4 20% 34% 24% 9%	570
	21st to end	Day	8% 3 18% 35% 29% 7%	570
July	1st to 10th	Day	10% 2 9% 31% 35% 13%	565
	11th to 20th	Day	9% 1 11% 30% 35% 13%	564
	21st to end	Day	10% 2 16% 33% 30% 10%	620
August	1st to 10th	Day	16% 4 15% 30% 25% 10%	566
	11th to 20th	Day	11% 2 17% 29% 28% 14%	559
	21st to end	Day	10% 3 13% 32% 26% 16%	627
September	1st to 10th	Day	13% 2 17% 28% 25% 15%	570
	11th to 20th	Day	16% 7% 13% 32% 20% 13%	542
	21st to end	Day	24% 6% 25% 25% 16% 4	530
October	1st to 10th	Day	16% 6% 22% 24% 23% 9%	530
	11th to 20th	Day	14% 10% 27% 28% 17% 4	530
	21st to end	Day	14% 12% 25% 29% 16% 5%	583
November	1st to 10th	Day	18% 10% 30% 26% 13% 4	535
	11th to 20th	Day	18% 14% 32% 26% 9% 1	512
	21st to end	Day	21% 16% 26% 22% 12% 2	267
December	1st to 10th	Day	22% 20% 39% 13% 6%	220
	11th to 20th	Day	20% 16% 35% 22% 6% 1	220
	21st to end	Day	23% 18% 32% 16% 10%	336
January	1st to 10th	Night	19% 17% 36% 22% 5%	840
	11th to 20th	Night	22% 14% 36% 24% 5%	840
	21st to end	Night	20% 13% 39% 25% 3	924
February	1st to 10th	Night	22% 12% 38% 25% 3	840
	11th to 20th	Night	25% 18% 39% 17% 1	823
	21st to end	Night	18% 17% 37% 25% 3	692
March	1st to 10th	Night	17% 15% 34% 28% 5%	840
	11th to 20th	Night	21% 12% 37% 23% 7%	840
	21st to end	Night	17% 12% 43% 22% 5%	924
April	1st to 10th	Night	17% 17% 35% 26% 5%	840
	11th to 20th	Night	16% 13% 35% 28% 9%	831
	21st to end	Night	13% 8% 36% 34% 8%	840
May	1st to 10th	Night	11% 11% 36% 32% 9%	740
	11th to 20th	Night	16% 6% 26% 38% 14% 1	621
	21st to end	Night	15% 3 20% 36% 25% 2	683
June	1st to 10th	Night	10% 3 23% 40% 24%	467
	11th to 20th	Night	11% 2 21% 41% 22% 3	420
	21st to end	Night	8% 2 16% 44% 27% 3	583
July	1st to 10th	Night	10% 1 11% 39% 35% 4	615
	11th to 20th	Night	9% 2 9% 39% 36% 6%	612
	21st to end	Night	9% 3 14% 39% 32% 4	690
August	1st to 10th	Night	13% 4 11% 40% 29% 3	627
	11th to 20th	Night	11% 3 12% 33% 37% 5%	728
	21st to end	Night	12% 3 12% 34% 32% 7%	924
September	1st to 10th	Night	13% 2 12% 34% 33% 5%	840
	11th to 20th	Night	16% 4 15% 34% 28% 4	813
	21st to end	Night	24% 4 19% 32% 21% 1	800
October	1st to 10th	Night	16% 3 21% 30% 25% 4	800
	11th to 20th	Night	16% 8% 25% 32% 18% 2	800
	21st to end	Night	15% 7% 27% 30% 20% 2	880
November	1st to 10th	Night	16% 8% 30% 31% 14% 2	820
	11th to 20th	Night	15% 12% 31% 31% 11%	840
	21st to end	Night	14% 11% 31% 30% 13% 1	840
December	1st to 10th	Night	22% 11% 34% 26% 8%	840
	11th to 20th	Night	19% 10% 32% 32% 7%	840
	21st to end	Night	19% 12% 33% 29% 7% 1	924

Page generated at 2026-09-11 04:11:57. Version ac07

Copyright © 2026 Attilla Danko.