My-Spot West Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the My-Spot West Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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	5% 6% 2 5% 5% 3 5% 6% 7% 9% 48%	75000
	Night	4 6% 2 5% 5% 3 4 5% 6% 9% 52%	74749
Transparency	Day	31% 8% 16% 24% 16% 5%	74710
	Night	27% 8% 17% 26% 17% 5%	74562
Seeing	Day	9% 13% 36% 30% 11% 2	14636
	Night	7% 7% 37% 36% 12% 1	24563

By Month

Percentage Cloud Cover SW (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	1 5% 3 5% 4 3 6% 5% 7% 11% 50%	1518
	11th to 20th	Day	1 4 3 6% 5% 3 4 6% 7% 11% 52%	1542
	21st to end	Day	1 6% 3 7% 6% 2 4 5% 7% 10% 48%	1782
February	1st to 10th	Day	1 5% 4 8% 7% 3 5% 6% 7% 10% 44%	1620
	11th to 20th	Day	1 6% 3 9% 7% 4 5% 5% 5% 8% 46%	1575
	21st to end	Day	1 6% 4 6% 7% 4 5% 6% 7% 10% 44%	1354
March	1st to 10th	Day	1 5% 3 6% 4 4 5% 5% 7% 13% 47%	1970
	11th to 20th	Day	2 7% 3 6% 6% 3 5% 6% 7% 10% 45%	1980
	21st to end	Day	5% 8% 4 8% 8% 4 5% 7% 7% 9% 35%	2178
April	1st to 10th	Day	5% 10% 3 7% 4 3 6% 5% 7% 11% 38%	2144
	11th to 20th	Day	6% 10% 5% 7% 6% 4 6% 7% 6% 8% 36%	2177
	21st to end	Day	10% 10% 4 7% 6% 3 5% 6% 6% 9% 34%	2340
May	1st to 10th	Day	9% 9% 3 6% 6% 4 6% 7% 6% 8% 35%	2371
	11th to 20th	Day	13% 8% 3 5% 5% 4 5% 6% 8% 8% 35%	2478
	21st to end	Day	14% 8% 3 6% 6% 4 6% 7% 8% 9% 29%	2724
June	1st to 10th	Day	8% 5% 2 5% 5% 4 6% 7% 8% 9% 40%	2520
	11th to 20th	Day	7% 5% 2 5% 5% 3 6% 6% 7% 10% 45%	2546
	21st to end	Day	3 3 1 3 4 3 5% 6% 7% 9% 57%	2700
July	1st to 10th	Day	3 2 1 3 5% 3 6% 6% 9% 10% 53%	2606
	11th to 20th	Day	2 2 1 2 4 3 4 5% 7% 9% 61%	2520
	21st to end	Day	3 3 2 4 4 3 5% 5% 7% 8% 56%	2628
August	1st to 10th	Day	5% 4 2 4 5% 3 5% 6% 7% 9% 49%	2328
	11th to 20th	Day	4 3 1 4 5% 4 4 6% 7% 7% 55%	2299
	21st to end	Day	4 3 1 4 4 3 5% 5% 5% 7% 58%	2494
September	1st to 10th	Day	5% 3 1 4 4 2 3 5% 5% 7% 60%	2160
	11th to 20th	Day	7% 3 1 4 4 2 3 5% 5% 6% 60%	2077
	21st to end	Day	7% 4 2 4 4 2 4 4 4 8% 57%	1944
October	1st to 10th	Day	10% 7% 3 6% 4 3 4 5% 4 7% 48%	1800
	11th to 20th	Day	6% 6% 2 3 4 3 4 5% 5% 7% 56%	1800
	21st to end	Day	3 8% 2 6% 5% 3 4 4 6% 8% 51%	1980
November	1st to 10th	Day	3 6% 2 6% 6% 3 6% 6% 7% 7% 48%	1565
	11th to 20th	Day	1 6% 3 5% 5% 3 5% 5% 6% 10% 51%	1520
	21st to end	Day	2 7% 3 7% 5% 2 4 4 5% 9% 52%	1520
December	1st to 10th	Day	1 4 2 7% 5% 3 5% 5% 7% 9% 52%	1520
	11th to 20th	Day	1 4 2 5% 5% 3 4 6% 8% 10% 51%	1926
	21st to end	Day	2 6% 2 5% 5% 3 4 5% 6% 8% 55%	2794
January	1st to 10th	Night	3 2 5% 5% 3 5% 6% 6% 10% 54%	2647
	11th to 20th	Night	1 5% 3 6% 6% 3 5% 5% 6% 8% 53%	2491
	21st to end	Night	1 7% 3 6% 6% 3 4 4 5% 9% 51%	2574
February	1st to 10th	Night	1 4 3 9% 6% 4 5% 7% 6% 8% 47%	2340
	11th to 20th	Night	1 6% 4 7% 6% 4 5% 5% 7% 8% 46%	2272
	21st to end	Night	5% 4 8% 5% 3 5% 6% 7% 8% 49%	1900
March	1st to 10th	Night	1 6% 2 6% 5% 3 5% 5% 6% 10% 51%	1986
	11th to 20th	Night	2 5% 2 4 4 3 4 5% 6% 11% 54%	1980
	21st to end	Night	5% 8% 4 7% 5% 3 5% 6% 6% 9% 42%	2178
April	1st to 10th	Night	5% 9% 4 6% 4 3 6% 4 7% 8% 44%	1815
	11th to 20th	Night	6% 11% 4 6% 7% 3 4 5% 6% 8% 40%	1726
	21st to end	Night	8% 11% 3 6% 6% 4 4 4 6% 9% 41%	1620
May	1st to 10th	Night	10% 10% 2 4 4 3 5% 5% 6% 7% 45%	1589
	11th to 20th	Night	10% 8% 2 6% 4 3 4 5% 6% 8% 44%	1417
	21st to end	Night	14% 7% 3 5% 5% 3 6% 5% 8% 10% 34%	1552
June	1st to 10th	Night	7% 5% 2 5% 4 3 6% 6% 6% 9% 46%	1440
	11th to 20th	Night	6% 4 1 4 4 3 5% 5% 5% 9% 52%	1404
	21st to end	Night	2 3 2 3 4 2 4 4 6% 6% 64%	1260
July	1st to 10th	Night	2 2 2 3 2 3 5% 6% 11% 63%	1349
	11th to 20th	Night	2 1 1 1 2 2 4 4 6% 10% 68%	1440
	21st to end	Night	3 2 1 3 2 1 4 3 7% 8% 66%	1687
August	1st to 10th	Night	3 3 1 3 4 3 4 6% 7% 9% 56%	1611
	11th to 20th	Night	4 3 1 3 3 1 3 4 5% 9% 63%	1602
	21st to end	Night	4 3 2 3 4 2 4 4 7% 7% 61%	1862
September	1st to 10th	Night	5% 3 1 3 3 2 3 4 4 8% 64%	1800
	11th to 20th	Night	6% 4 2 3 3 2 3 4 5% 7% 62%	1880
	21st to end	Night	9% 5% 2 3 3 2 3 2 4 6% 60%	2014
October	1st to 10th	Night	10% 7% 2 5% 4 2 4 3 6% 8% 49%	2160
	11th to 20th	Night	5% 7% 3 4 4 3 4 4 4 6% 56%	2160
	21st to end	Night	4 7% 3 5% 5% 2 4 5% 6% 8% 52%	2376
November	1st to 10th	Night	3 5% 2 5% 4 3 4 5% 6% 10% 52%	2493
	11th to 20th	Night	2 6% 3 5% 4 3 4 5% 7% 10% 51%	2660
	21st to end	Night	3 7% 3 4 5% 3 4 5% 6% 10% 50%	2660
December	1st to 10th	Night	1 5% 3 6% 6% 3 4 5% 8% 10% 50%	2660
	11th to 20th	Night	1 4 3 5% 4 3 4 5% 7% 12% 52%	3271
	21st to end	Night	1 6% 2 6% 5% 3 4 5% 6% 9% 53%	4873

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	27% 9% 21% 29% 12% 2	1519
	11th to 20th	Day	24% 10% 22% 26% 15% 3	1542
	21st to end	Day	29% 8% 20% 26% 14% 2	1782
February	1st to 10th	Day	32% 10% 21% 26% 10% 1	1620
	11th to 20th	Day	36% 8% 20% 22% 12% 3	1584
	21st to end	Day	33% 9% 17% 22% 14% 5%	1354
March	1st to 10th	Day	27% 9% 20% 31% 12% 1	1970
	11th to 20th	Day	31% 9% 21% 25% 11% 2	1980
	21st to end	Day	42% 11% 19% 22% 6% 1	2178
April	1st to 10th	Day	39% 9% 17% 24% 10% 1	2144
	11th to 20th	Day	44% 8% 19% 22% 7% 1	2180
	21st to end	Day	47% 8% 15% 22% 8%	2340
May	1st to 10th	Day	44% 10% 15% 21% 9% 1	2371
	11th to 20th	Day	41% 12% 16% 24% 7%	2482
	21st to end	Day	47% 12% 18% 17% 6%	2724
June	1st to 10th	Day	35% 11% 20% 21% 11% 2	2520
	11th to 20th	Day	32% 11% 16% 19% 18% 5%	2546
	21st to end	Day	21% 8% 13% 26% 20% 12%	2700
July	1st to 10th	Day	23% 9% 13% 24% 21% 10%	2537
	11th to 20th	Day	17% 6% 11% 21% 24% 20%	2445
	21st to end	Day	23% 7% 10% 18% 26% 16%	2482
August	1st to 10th	Day	28% 8% 11% 22% 20% 10%	2313
	11th to 20th	Day	26% 6% 12% 24% 23% 9%	2299
	21st to end	Day	23% 6% 11% 20% 27% 14%	2494
September	1st to 10th	Day	23% 5% 8% 20% 30% 14%	2160
	11th to 20th	Day	24% 5% 10% 26% 27% 8%	2077
	21st to end	Day	27% 5% 11% 28% 24% 5%	1944
October	1st to 10th	Day	37% 7% 13% 22% 17% 4	1800
	11th to 20th	Day	28% 7% 15% 29% 15% 6%	1800
	21st to end	Day	30% 6% 17% 28% 17% 3	1980
November	1st to 10th	Day	32% 9% 16% 22% 19% 3	1565
	11th to 20th	Day	28% 9% 19% 25% 17% 3	1520
	21st to end	Day	29% 7% 17% 26% 18% 2	1520
December	1st to 10th	Day	26% 9% 20% 25% 15% 4	1520
	11th to 20th	Day	22% 10% 26% 30% 11% 1	1924
	21st to end	Day	26% 6% 13% 26% 20% 9%	2794
January	1st to 10th	Night	23% 10% 22% 29% 15% 1	2647
	11th to 20th	Night	28% 8% 22% 24% 15% 4	2491
	21st to end	Night	29% 7% 19% 27% 15% 3	2574
February	1st to 10th	Night	31% 9% 21% 28% 9% 2	2340
	11th to 20th	Night	33% 9% 19% 23% 13% 3	2273
	21st to end	Night	30% 8% 18% 23% 17% 3	1900
March	1st to 10th	Night	27% 8% 20% 29% 16% 2	1986
	11th to 20th	Night	24% 8% 22% 30% 14% 2	1980
	21st to end	Night	36% 9% 19% 26% 8% 1	2178
April	1st to 10th	Night	36% 9% 21% 22% 11% 2	1815
	11th to 20th	Night	41% 8% 19% 23% 9% 1	1726
	21st to end	Night	40% 7% 15% 29% 8%	1620
May	1st to 10th	Night	38% 7% 15% 27% 11% 2	1589
	11th to 20th	Night	36% 10% 19% 28% 7% 1	1418
	21st to end	Night	41% 10% 22% 19% 7%	1552
June	1st to 10th	Night	32% 10% 20% 22% 15% 1	1440
	11th to 20th	Night	26% 8% 20% 24% 15% 7%	1404
	21st to end	Night	19% 6% 13% 30% 21% 11%	1260
July	1st to 10th	Night	15% 6% 14% 30% 25% 11%	1310
	11th to 20th	Night	11% 4 10% 27% 27% 20%	1392
	21st to end	Night	15% 5% 11% 20% 32% 18%	1593
August	1st to 10th	Night	21% 7% 13% 24% 23% 11%	1602
	11th to 20th	Night	17% 5% 11% 30% 24% 12%	1602
	21st to end	Night	20% 5% 11% 24% 26% 15%	1862
September	1st to 10th	Night	20% 5% 10% 21% 31% 14%	1800
	11th to 20th	Night	21% 5% 12% 26% 25% 10%	1880
	21st to end	Night	26% 4 10% 28% 27% 4	2014
October	1st to 10th	Night	34% 7% 12% 28% 15% 4	2160
	11th to 20th	Night	28% 6% 14% 31% 17% 4	2160
	21st to end	Night	28% 8% 16% 27% 17% 3	2376
November	1st to 10th	Night	27% 10% 17% 26% 16% 3	2493
	11th to 20th	Night	26% 8% 21% 28% 15% 2	2660
	21st to end	Night	29% 6% 18% 27% 17% 3	2660
December	1st to 10th	Night	26% 8% 23% 25% 15% 4	2660
	11th to 20th	Night	23% 10% 23% 31% 13% 1	3272
	21st to end	Night	26% 8% 14% 26% 16% 10%	4873

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	7% 12% 37% 29% 13% 2	270
	11th to 20th	Day	3 11% 47% 24% 11% 5%	246
	21st to end	Day	7% 14% 46% 27% 5% 2	264
February	1st to 10th	Day	6% 23% 54% 16%	240
	11th to 20th	Day	6% 25% 41% 22% 6%	240
	21st to end	Day	6% 20% 42% 23% 9%	198
March	1st to 10th	Day	6% 22% 47% 23% 2	410
	11th to 20th	Day	7% 20% 44% 23% 5% 1	420
	21st to end	Day	13% 18% 37% 25% 5%	462
April	1st to 10th	Day	13% 23% 38% 23% 3	420
	11th to 20th	Day	15% 22% 39% 21% 4	412
	21st to end	Day	19% 18% 31% 24% 7% 1	420
May	1st to 10th	Day	13% 15% 33% 24% 12% 2	454
	11th to 20th	Day	18% 10% 26% 31% 13% 2	625
	21st to end	Day	17% 10% 28% 27% 16% 3	679
June	1st to 10th	Day	7% 12% 30% 32% 16% 3	630
	11th to 20th	Day	10% 15% 33% 31% 9% 1	630
	21st to end	Day	4 9% 33% 37% 16% 2	630
July	1st to 10th	Day	4 6% 28% 36% 23% 4	621
	11th to 20th	Day	3 6% 33% 43% 15% 1	618
	21st to end	Day	4 5% 37% 36% 17% 2	570
August	1st to 10th	Day	8% 6% 37% 36% 11% 2	447
	11th to 20th	Day	4 6% 30% 40% 16% 4	437
	21st to end	Day	5% 8% 34% 37% 13% 2	495
September	1st to 10th	Day	7% 9% 38% 34% 11% 2	450
	11th to 20th	Day	10% 10% 34% 31% 12% 4	450
	21st to end	Day	9% 14% 34% 29% 11% 2	414
October	1st to 10th	Day	10% 14% 27% 33% 14% 3	270
	11th to 20th	Day	13% 14% 31% 29% 10% 3	270
	21st to end	Day	10% 19% 38% 26% 6% 1	297
November	1st to 10th	Day	9% 17% 41% 22% 8% 3	270
	11th to 20th	Day	11% 13% 40% 28% 6% 1	270
	21st to end	Day	10% 13% 40% 31% 4	270
December	1st to 10th	Day	4 15% 46% 24% 9% 1	270
	11th to 20th	Day	7% 14% 48% 27% 4	270
	21st to end	Day	5% 12% 48% 24% 10% 1	297
January	1st to 10th	Night	3 11% 42% 35% 8% 1	950
	11th to 20th	Night	4 10% 51% 23% 9% 3	845
	21st to end	Night	4 8% 52% 29% 6% 1	792
February	1st to 10th	Night	5% 8% 54% 27% 6%	720
	11th to 20th	Night	6% 9% 47% 29% 9% 1	704
	21st to end	Night	2 12% 46% 32% 8% 1	592
March	1st to 10th	Night	4 10% 43% 33% 8%	720
	11th to 20th	Night	5% 8% 44% 35% 9%	720
	21st to end	Night	8% 8% 38% 39% 6% 1	792
April	1st to 10th	Night	9% 8% 44% 31% 8%	555
	11th to 20th	Night	12% 9% 41% 31% 6% 1	533
	21st to end	Night	13% 7% 34% 33% 13% 1	540
May	1st to 10th	Night	15% 7% 25% 37% 16%	540
	11th to 20th	Night	15% 6% 20% 41% 18% 1	531
	21st to end	Night	18% 6% 21% 38% 16% 1	584
June	1st to 10th	Night	8% 6% 25% 39% 20% 2	540
	11th to 20th	Night	7% 8% 34% 40% 11%	504
	21st to end	Night	4 2 20% 51% 22% 1	360
July	1st to 10th	Night	3 1 15% 52% 28% 1	435
	11th to 20th	Night	1 3 24% 54% 18%	522
	21st to end	Night	2 2 20% 53% 23% 1	591
August	1st to 10th	Night	4 2 16% 57% 21%	537
	11th to 20th	Night	4 3 14% 55% 23% 1	534
	21st to end	Night	5% 2 24% 44% 23% 2	594
September	1st to 10th	Night	6% 2 25% 46% 18% 2	540
	11th to 20th	Night	7% 4 23% 47% 16% 4	620
	21st to end	Night	12% 3 26% 40% 17% 3	720
October	1st to 10th	Night	14% 4 28% 38% 14% 2	720
	11th to 20th	Night	8% 7% 39% 31% 14% 2	720
	21st to end	Night	7% 6% 45% 33% 9% 2	792
November	1st to 10th	Night	7% 8% 44% 32% 8% 1	871
	11th to 20th	Night	6% 11% 49% 30% 4 1	950
	21st to end	Night	7% 8% 42% 36% 6%	950
December	1st to 10th	Night	4 11% 47% 30% 7% 1	950
	11th to 20th	Night	3 9% 50% 31% 7% 1	950
	21st to end	Night	4 8% 50% 30% 7% 1	1045

Page generated at 2024-01-10 08:16:08. Version ac07

Copyright 2024 Attilla Danko