Telescope Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Telescope Park clear sky chart from 2005-11-06 to 2024-02-10.

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	18% 7% 3 5% 5% 3 4 4 5% 7% 40%	77864
	Night	19% 8% 3 5% 5% 3 4 4 5% 6% 39%	81072
Transparency	Day	44% 6% 12% 22% 14% 2	77571
	Night	46% 5% 11% 22% 14% 2	80901
Seeing	Day	21% 12% 31% 25% 10% 2	14240
	Night	22% 11% 29% 26% 10% 1	23116

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	17% 7% 3 5% 6% 3 4 3 5% 6% 42%	2517
	11th to 20th	Day	19% 6% 2 5% 5% 3 4 4 5% 6% 43%	2520
	21st to end	Day	18% 11% 3 5% 4 2 4 4 4 5% 39%	2774
February	1st to 10th	Day	18% 9% 2 5% 5% 3 5% 4 5% 6% 37%	1701
	11th to 20th	Day	14% 10% 3 6% 6% 3 5% 5% 5% 6% 38%	1726
	21st to end	Day	15% 12% 3 5% 4 4 5% 4 5% 6% 36%	1480
March	1st to 10th	Day	17% 9% 3 5% 5% 3 4 4 5% 7% 38%	1797
	11th to 20th	Day	17% 6% 3 5% 5% 3 4 3 4 6% 44%	1962
	21st to end	Day	18% 7% 3 5% 5% 3 4 4 4 5% 42%	2199
April	1st to 10th	Day	21% 9% 3 5% 5% 3 5% 4 5% 6% 36%	2160
	11th to 20th	Day	19% 6% 2 5% 4 2 4 4 5% 7% 41%	2246
	21st to end	Day	23% 7% 3 6% 5% 3 4 4 5% 6% 34%	2340
May	1st to 10th	Day	24% 7% 3 6% 6% 3 4 4 4 6% 33%	2340
	11th to 20th	Day	20% 7% 3 6% 5% 2 3 4 5% 6% 39%	2301
	21st to end	Day	19% 7% 3 4 5% 2 4 5% 6% 8% 37%	2720
June	1st to 10th	Day	22% 6% 3 6% 5% 2 4 4 6% 8% 33%	2574
	11th to 20th	Day	19% 6% 2 5% 4 3 4 5% 5% 7% 40%	2700
	21st to end	Day	23% 6% 3 6% 5% 3 5% 5% 4 9% 33%	2551
July	1st to 10th	Day	17% 5% 3 5% 5% 2 5% 4 6% 9% 39%	2520
	11th to 20th	Day	14% 6% 3 5% 4 3 5% 6% 7% 9% 39%	2520
	21st to end	Day	14% 4 2 5% 6% 3 5% 6% 7% 9% 40%	2726
August	1st to 10th	Day	13% 5% 2 5% 4 3 5% 6% 7% 9% 41%	2327
	11th to 20th	Day	14% 6% 2 5% 5% 3 5% 5% 6% 9% 40%	2304
	21st to end	Day	12% 5% 2 4 4 3 5% 5% 6% 8% 47%	2502
September	1st to 10th	Day	13% 5% 2 4 4 3 4 5% 5% 7% 48%	2098
	11th to 20th	Day	12% 6% 2 4 4 2 3 3 4 6% 55%	1980
	21st to end	Day	17% 6% 2 4 4 2 4 3 4 6% 46%	1980
October	1st to 10th	Day	18% 7% 3 6% 5% 3 4 4 4 6% 41%	1970
	11th to 20th	Day	19% 6% 2 5% 5% 3 4 4 3 6% 43%	1756
	21st to end	Day	23% 8% 2 4 4 2 3 4 4 5% 39%	1782
November	1st to 10th	Day	17% 5% 3 4 4 2 3 4 4 5% 48%	1671
	11th to 20th	Day	21% 4 2 4 4 2 3 4 4 7% 45%	1710
	21st to end	Day	22% 7% 3 5% 3 2 3 3 4 5% 43%	1630
December	1st to 10th	Day	22% 8% 3 5% 5% 3 3 4 4 5% 38%	1397
	11th to 20th	Day	23% 8% 3 4 3 2 3 4 3 5% 41%	1668
	21st to end	Day	26% 9% 3 6% 5% 3 4 4 4 6% 30%	2715
January	1st to 10th	Night	16% 9% 3 5% 4 2 4 3 4 7% 42%	4429
	11th to 20th	Night	14% 8% 4 8% 6% 3 5% 4 5% 6% 37%	4440
	21st to end	Night	19% 11% 4 6% 5% 3 4 4 4 5% 35%	4880
February	1st to 10th	Night	17% 9% 3 5% 6% 3 5% 5% 4 6% 36%	2464
	11th to 20th	Night	14% 9% 4 6% 5% 3 5% 4 5% 5% 39%	2120
	21st to end	Night	15% 9% 3 6% 5% 3 3 3 4 6% 41%	1776
March	1st to 10th	Night	16% 11% 3 5% 5% 3 4 4 5% 5% 40%	2150
	11th to 20th	Night	18% 7% 3 6% 5% 3 4 5% 5% 7% 36%	1997
	21st to end	Night	19% 8% 3 5% 4 2 4 3 4 6% 42%	2155
April	1st to 10th	Night	23% 8% 2 5% 6% 2 5% 4 4 6% 36%	1800
	11th to 20th	Night	19% 7% 2 5% 4 3 5% 4 6% 7% 39%	1661
	21st to end	Night	24% 7% 3 5% 4 3 5% 5% 4 7% 33%	1620
May	1st to 10th	Night	21% 9% 3 6% 5% 2 5% 6% 5% 7% 30%	1620
	11th to 20th	Night	22% 7% 3 6% 6% 3 4 6% 6% 7% 31%	1593
	21st to end	Night	21% 10% 4 6% 5% 2 4 4 4 7% 35%	1569
June	1st to 10th	Night	24% 8% 2 6% 5% 3 6% 4 5% 6% 32%	1378
	11th to 20th	Night	17% 7% 3 6% 4 3 5% 5% 5% 7% 38%	1260
	21st to end	Night	25% 8% 3 4 4 2 5% 5% 5% 7% 31%	1397
July	1st to 10th	Night	17% 7% 3 5% 5% 3 5% 5% 6% 8% 36%	1440
	11th to 20th	Night	17% 8% 3 5% 5% 2 5% 4 6% 9% 35%	1440
	21st to end	Night	16% 5% 2 5% 5% 4 5% 5% 7% 9% 36%	1574
August	1st to 10th	Night	13% 8% 3 5% 5% 3 5% 5% 5% 8% 41%	1609
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 6% 6% 8% 37%	1596
	21st to end	Night	14% 6% 2 4 4 2 5% 4 4 7% 48%	1850
September	1st to 10th	Night	13% 6% 2 4 4 3 5% 4 5% 7% 47%	1862
	11th to 20th	Night	14% 7% 2 4 3 2 3 3 3 6% 51%	1980
	21st to end	Night	16% 5% 2 4 4 2 4 3 5% 6% 47%	1980
October	1st to 10th	Night	19% 7% 3 4 5% 3 4 4 6% 6% 40%	1989
	11th to 20th	Night	18% 7% 2 5% 5% 3 4 4 5% 6% 42%	2203
	21st to end	Night	25% 7% 2 5% 4 3 4 3 4 5% 37%	2574
November	1st to 10th	Night	18% 6% 2 5% 4 3 4 4 4 5% 45%	2407
	11th to 20th	Night	19% 5% 2 4 4 3 5% 5% 4 6% 43%	2470
	21st to end	Night	16% 7% 3 4 5% 3 4 5% 4 6% 42%	2546
December	1st to 10th	Night	23% 8% 3 5% 5% 3 4 4 4 5% 36%	2778
	11th to 20th	Night	23% 6% 2 3 4 3 3 4 5% 6% 42%	3531
	21st to end	Night	25% 9% 3 5% 4 3 3 4 4 5% 35%	4934

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	44% 5% 13% 26% 11% 1	2518
	11th to 20th	Day	43% 5% 13% 24% 13% 2	2520
	21st to end	Day	48% 5% 12% 22% 13% 1	2774
February	1st to 10th	Day	47% 6% 11% 19% 14% 2	1701
	11th to 20th	Day	46% 6% 13% 19% 13% 3	1735
	21st to end	Day	49% 4 10% 20% 13% 4	1480
March	1st to 10th	Day	46% 4 13% 18% 15% 4	1800
	11th to 20th	Day	43% 4 10% 22% 17% 5%	1962
	21st to end	Day	44% 5% 8% 18% 18% 6%	2199
April	1st to 10th	Day	49% 4 9% 18% 15% 4	2160
	11th to 20th	Day	44% 4 10% 24% 15% 3	2246
	21st to end	Day	51% 5% 8% 19% 14% 4	2340
May	1st to 10th	Day	52% 5% 8% 20% 14% 2	2340
	11th to 20th	Day	45% 5% 9% 21% 17% 3	2305
	21st to end	Day	45% 8% 13% 20% 12% 2	2720
June	1st to 10th	Day	50% 6% 13% 22% 9%	2574
	11th to 20th	Day	43% 7% 10% 21% 16% 2	2700
	21st to end	Day	50% 8% 11% 21% 9% 1	2551
July	1st to 10th	Day	40% 9% 12% 24% 14%	2450
	11th to 20th	Day	41% 7% 14% 25% 11% 1	2445
	21st to end	Day	38% 9% 17% 24% 12% 1	2574
August	1st to 10th	Day	36% 8% 18% 27% 10%	2314
	11th to 20th	Day	39% 8% 16% 25% 12% 1	2304
	21st to end	Day	34% 7% 14% 25% 18% 2	2502
September	1st to 10th	Day	34% 7% 14% 28% 17% 1	2098
	11th to 20th	Day	32% 7% 10% 27% 22% 2	1980
	21st to end	Day	41% 6% 8% 27% 18% 1	1980
October	1st to 10th	Day	45% 5% 10% 24% 15% 2	1970
	11th to 20th	Day	43% 4 14% 27% 11% 1	1756
	21st to end	Day	48% 4 11% 21% 14% 2	1782
November	1st to 10th	Day	39% 4 13% 25% 17% 2	1671
	11th to 20th	Day	40% 5% 10% 23% 19% 3	1710
	21st to end	Day	44% 4 17% 22% 13% 1	1630
December	1st to 10th	Day	51% 4 10% 21% 13% 1	1397
	11th to 20th	Day	46% 5% 8% 21% 15% 4	1668
	21st to end	Day	55% 7% 10% 17% 9% 3	2715
January	1st to 10th	Night	43% 5% 11% 29% 10% 2	4429
	11th to 20th	Night	47% 5% 13% 20% 12% 2	4440
	21st to end	Night	51% 5% 10% 21% 11% 1	4880
February	1st to 10th	Night	49% 5% 11% 19% 13% 3	2464
	11th to 20th	Night	48% 5% 8% 21% 16% 3	2122
	21st to end	Night	45% 4 10% 22% 15% 4	1776
March	1st to 10th	Night	48% 4 7% 21% 17% 3	2160
	11th to 20th	Night	48% 4 11% 18% 15% 5%	1998
	21st to end	Night	44% 4 8% 19% 20% 5%	2155
April	1st to 10th	Night	51% 3 7% 17% 16% 4	1800
	11th to 20th	Night	45% 4 9% 23% 17% 1	1661
	21st to end	Night	52% 5% 10% 18% 12% 4	1620
May	1st to 10th	Night	52% 6% 8% 18% 14% 2	1620
	11th to 20th	Night	52% 6% 8% 18% 13% 3	1594
	21st to end	Night	51% 6% 10% 18% 13% 1	1570
June	1st to 10th	Night	54% 5% 10% 21% 9% 1	1378
	11th to 20th	Night	45% 7% 12% 19% 15% 2	1260
	21st to end	Night	52% 6% 12% 20% 10% 1	1397
July	1st to 10th	Night	45% 8% 13% 20% 14% 1	1400
	11th to 20th	Night	45% 6% 13% 26% 10%	1392
	21st to end	Night	41% 8% 16% 24% 10% 1	1486
August	1st to 10th	Night	41% 8% 14% 26% 10% 1	1598
	11th to 20th	Night	44% 8% 13% 22% 13%	1596
	21st to end	Night	36% 7% 10% 28% 18% 1	1850
September	1st to 10th	Night	36% 6% 11% 28% 17% 1	1862
	11th to 20th	Night	36% 4 10% 27% 21% 2	1980
	21st to end	Night	38% 6% 9% 29% 16% 2	1980
October	1st to 10th	Night	45% 5% 10% 24% 14% 2	1989
	11th to 20th	Night	42% 5% 12% 27% 13% 1	2203
	21st to end	Night	49% 5% 10% 20% 14% 2	2574
November	1st to 10th	Night	42% 6% 10% 26% 15% 2	2407
	11th to 20th	Night	42% 5% 10% 23% 18% 2	2470
	21st to end	Night	43% 6% 14% 21% 15% 2	2546
December	1st to 10th	Night	51% 4 10% 21% 13% 1	2778
	11th to 20th	Night	45% 5% 11% 21% 17% 1	3532
	21st to end	Night	52% 5% 11% 18% 13% 1	4934

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	24% 23% 28% 19% 6%	180
	11th to 20th	Day	26% 20% 29% 20% 4 1	180
	21st to end	Day	18% 19% 33% 24% 7%	200
February	1st to 10th	Day	25% 18% 32% 21% 3	367
	11th to 20th	Day	21% 21% 39% 16% 2	406
	21st to end	Day	21% 17% 37% 20% 5%	346
March	1st to 10th	Day	23% 14% 41% 19% 4	420
	11th to 20th	Day	18% 21% 39% 18% 4	420
	21st to end	Day	23% 19% 33% 15% 8% 3	462
April	1st to 10th	Day	27% 18% 31% 16% 6% 2	420
	11th to 20th	Day	24% 13% 37% 17% 7% 1	412
	21st to end	Day	29% 10% 35% 20% 4 1	420
May	1st to 10th	Day	27% 14% 32% 20% 6% 1	423
	11th to 20th	Day	19% 13% 39% 19% 9% 2	447
	21st to end	Day	21% 10% 34% 26% 7% 2	485
June	1st to 10th	Day	21% 7% 29% 31% 9% 2	504
	11th to 20th	Day	21% 8% 29% 27% 13% 3	630
	21st to end	Day	22% 5% 28% 30% 12% 2	481
July	1st to 10th	Day	20% 6% 25% 34% 13% 2	445
	11th to 20th	Day	16% 5% 27% 33% 17% 3	444
	21st to end	Day	14% 4 25% 38% 15% 3	488
August	1st to 10th	Day	13% 4 26% 36% 18% 3	446
	11th to 20th	Day	16% 4 27% 33% 15% 6%	439
	21st to end	Day	13% 7% 24% 36% 17% 3	495
September	1st to 10th	Day	16% 5% 25% 35% 16% 3	450
	11th to 20th	Day	16% 10% 28% 27% 14% 6%	450
	21st to end	Day	18% 9% 31% 22% 15% 5%	450
October	1st to 10th	Day	21% 12% 21% 28% 14% 3	444
	11th to 20th	Day	21% 12% 29% 25% 10% 4	360
	21st to end	Day	31% 10% 28% 22% 8% 1	396
November	1st to 10th	Day	20% 15% 29% 24% 9% 2	365
	11th to 20th	Day	25% 15% 30% 21% 8% 1	370
	21st to end	Day	24% 20% 28% 20% 7% 1	370
December	1st to 10th	Day	25% 12% 38% 17% 6% 1	247
	11th to 20th	Day	25% 24% 33% 14% 4 1	180
	21st to end	Day	28% 20% 31% 14% 6% 1	198
January	1st to 10th	Night	21% 20% 36% 20% 4	760
	11th to 20th	Night	25% 20% 34% 17% 4	760
	21st to end	Night	20% 21% 36% 19% 4 1	836
February	1st to 10th	Night	22% 18% 35% 20% 4	759
	11th to 20th	Night	21% 20% 37% 18% 3	703
	21st to end	Night	20% 16% 39% 20% 6%	592
March	1st to 10th	Night	22% 17% 36% 22% 3	720
	11th to 20th	Night	22% 15% 33% 22% 8% 1	720
	21st to end	Night	23% 13% 34% 23% 6% 1	792
April	1st to 10th	Night	28% 13% 33% 20% 6% 1	720
	11th to 20th	Night	22% 9% 32% 28% 8% 1	597
	21st to end	Night	30% 6% 26% 28% 8% 1	540
May	1st to 10th	Night	26% 4 29% 29% 11% 2	540
	11th to 20th	Night	26% 5% 31% 29% 9% 1	532
	21st to end	Night	27% 3 22% 32% 14% 1	408
June	1st to 10th	Night	25% 4 21% 34% 13% 3	360
	11th to 20th	Night	21% 5% 18% 39% 16% 2	360
	21st to end	Night	27% 4 16% 39% 13% 1	360
July	1st to 10th	Night	22% 2 13% 42% 20% 1	350
	11th to 20th	Night	21% 2 14% 39% 22% 1	348
	21st to end	Night	18% 3 15% 41% 22% 2	394
August	1st to 10th	Night	16% 3 16% 43% 21% 1	535
	11th to 20th	Night	15% 3 17% 40% 23% 2	532
	21st to end	Night	16% 3 17% 36% 25% 3	662
September	1st to 10th	Night	16% 2 21% 36% 22% 2	720
	11th to 20th	Night	18% 5% 24% 27% 21% 4	720
	21st to end	Night	17% 6% 24% 32% 19% 3	720
October	1st to 10th	Night	22% 8% 22% 29% 18% 2	720
	11th to 20th	Night	20% 10% 30% 26% 11% 3	720
	21st to end	Night	29% 10% 30% 24% 6% 1	792
November	1st to 10th	Night	21% 10% 32% 26% 9% 1	740
	11th to 20th	Night	22% 15% 32% 23% 7% 1	760
	21st to end	Night	20% 19% 34% 21% 6%	796
December	1st to 10th	Night	28% 12% 38% 16% 6%	850
	11th to 20th	Night	24% 17% 35% 19% 3	850
	21st to end	Night	29% 15% 34% 18% 4	848

Page generated at 2024-02-07 06:11:58. Version ac07

Copyright 2024 Attilla Danko