Holgate
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Holgate clear sky chart from 2005-11-06 to 2024-01-16.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
40%
23320
13%
74633
8%
23281
47%
23281
13%
56339

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
22%
760
15%
2649
6%
757
35%
757
10%
1983
January11th to 20thNight
26%
744
12%
2599
5%
744
36%
744
9%
2019
January21st to endNight
24%
792
15%
2574
6%
792
35%
792
12%
1919
February1st to 10thNight
23%
720
12%
2306
4%
720
33%
720
11%
1741
February11th to 20thNight
17%
703
13%
2098
4%
699
30%
699
12%
1635
February21st to endNight
24%
592
18%
1776
7%
592
38%
592
13%
1343
March1st to 10thNight
28%
720
15%
2160
8%
720
38%
720
15%
1578
March11th to 20thNight
31%
720
13%
2044
8%
720
38%
720
12%
1620
March21st to endNight
33%
792
15%
2009
6%
792
39%
792
15%
1602
April1st to 10thNight
32%
720
14%
1800
5%
720
37%
720
16%
1408
April11th to 20thNight
43%
711
15%
1775
6%
711
46%
711
17%
1387
April21st to endNight
41%
720
14%
1800
6%
720
44%
720
16%
1426
May1st to 10thNight
42%
565
12%
1645
7%
565
45%
565
12%
1311
May11th to 20thNight
43%
432
14%
1494
11%
432
47%
432
12%
1165
May21st to endNight
54%
388
10%
1551
12%
388
56%
388
10%
1182
June1st to 10thNight
53%
360
11%
1440
15%
360
54%
360
10%
1096
June11th to 20thNight
60%
360
11%
1440
14%
360
62%
360
11%
1079
June21st to endNight
67%
360
12%
1440
16%
360
69%
360
13%
1037
July1st to 10thNight
63%
350
10%
1400
13%
350
64%
350
10%
1065
July11th to 20thNight
68%
348
11%
1392
13%
348
69%
348
12%
990
July21st to endNight
65%
394
13%
1486
14%
372
69%
372
12%
1085
August1st to 10thNight
65%
571
10%
1635
8%
569
65%
569
15%
1269
August11th to 20thNight
64%
710
13%
1774
7%
710
65%
710
18%
1376
August21st to endNight
65%
792
8%
1980
4%
792
66%
792
16%
1585
September1st to 10thNight
56%
720
16%
1800
9%
720
59%
720
19%
1394
September11th to 20thNight
63%
720
20%
1872
14%
720
65%
720
21%
1380
September21st to endNight
48%
720
13%
1980
10%
720
52%
720
14%
1563
October1st to 10thNight
46%
720
13%
2078
9%
720
50%
720
16%
1581
October11th to 20thNight
45%
720
15%
2160
11%
720
51%
720
15%
1634
October21st to endNight
35%
792
14%
2482
9%
792
43%
792
13%
1894
November1st to 10thNight
40%
740
16%
2407
10%
740
49%
740
15%
1726
November11th to 20thNight
34%
760
16%
2470
10%
760
43%
760
11%
1875
November21st to endNight
33%
760
14%
2493
8%
760
42%
760
12%
1871
December1st to 10thNight
24%
760
13%
2660
4%
760
35%
760
10%
2010
December11th to 20thNight
23%
760
15%
3175
5%
759
34%
759
8%
2275
December21st to endNight
27%
824
8%
4789
4%
817
37%
817
6%
3235

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 ForecastData
Points
Cloud CoverDay
14%6%25%5%345%6%8%43%
74781
Night
15%7%35%5%3445%7%42%
75014
TransparencyDay
26%37%8%16%10%2
74486
Night
28%37%8%15%11%2
74843
SeeingDay
17%6%21%31%21%4
13993
Night
19%8%25%30%16%3
23333

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
13%7%36%4235%6%8%42%
1517
11th to 20thDay
15%7%24425%45%7%44%
1486
21st to endDay
16%8%345%3435%7%42%
1782
February1st to 10thDay
16%8%36%4345%6%8%37%
1652
11th to 20thDay
18%7%35%434445%43%
1748
21st to endDay
18%8%36%4335%6%7%38%
1480
March1st to 10thDay
13%6%25%434436%49%
1797
11th to 20thDay
16%6%25%5%35%5%5%8%41%
1912
21st to endDay
19%6%35%5%3445%6%40%
2346
April1st to 10thDay
16%8%36%43435%7%42%
2160
11th to 20thDay
14%6%35%5%2445%6%46%
2134
21st to endDay
17%6%35%5%345%6%7%39%
2160
May1st to 10thDay
18%7%35%5%35%5%6%7%37%
2312
11th to 20thDay
18%7%25%5%35%45%7%39%
2414
21st to endDay
13%8%35%425%5%6%8%41%
2725
June1st to 10thDay
13%7%25%5%346%7%9%39%
2520
11th to 20thDay
12%5%25%5%35%6%7%11%39%
2520
21st to endDay
8%3345%35%7%8%10%45%
2520
July1st to 10thDay
8%5%26%5%35%6%7%11%43%
2520
11th to 20thDay
5%4245%35%6%7%12%45%
2520
21st to endDay
9%5%25%5%36%6%8%10%41%
2744
August1st to 10thDay
8%5%25%5%35%5%6%10%45%
2269
11th to 20thDay
11%5%245%45%5%5%9%43%
2126
21st to endDay
10%6%35%5%345%6%8%45%
2376
September1st to 10thDay
15%5%2443445%7%48%
2160
11th to 20thDay
10%6%26%434447%50%
2088
21st to endDay
18%7%25%6%3445%7%40%
1980
October1st to 10thDay
18%6%25%43345%6%44%
1879
11th to 20thDay
16%5%24423446%51%
1800
21st to endDay
17%5%244345%46%43%
1872
November1st to 10thDay
15%6%24424447%49%
1671
11th to 20thDay
15%436%5%25%346%47%
1710
21st to endDay
15%4245%3435%8%46%
1683
December1st to 10thDay
18%7%244345%5%7%39%
1520
11th to 20thDay
17%7%25%423445%46%
1906
21st to endDay
15%7%36%435%5%6%7%40%
2772
January1st to 10thNight
17%6%24424447%44%
2649
11th to 20thNight
19%6%36%5%2336%6%41%
2599
21st to endNight
15%7%35%42445%6%45%
2574
February1st to 10thNight
18%7%345%3345%6%41%
2306
11th to 20thNight
19%7%25%43345%6%40%
2098
21st to endNight
18%7%26%333445%44%
1776
March1st to 10thNight
16%6%2442435%7%48%
2150
11th to 20thNight
17%7%35%434345%44%
2043
21st to endNight
18%7%36%5%3443442%
2009
April1st to 10thNight
17%8%35%42445%6%41%
1800
11th to 20thNight
15%7%36%5%33346%45%
1775
21st to endNight
18%7%34435%5%5%7%39%
1800
May1st to 10thNight
18%9%47%5%35%45%6%34%
1645
11th to 20thNight
18%7%46%435%448%36%
1493
21st to endNight
17%9%37%425%45%7%36%
1550
June1st to 10thNight
16%7%36%6%35%45%7%38%
1440
11th to 20thNight
12%6%35%7%35%5%6%8%41%
1440
21st to endNight
8%5%25%6%35%6%7%11%42%
1440
July1st to 10thNight
8%6%38%7%5%5%6%7%9%38%
1440
11th to 20thNight
5%5%36%6%46%6%7%10%43%
1440
21st to endNight
8%5%26%7%46%6%6%8%41%
1574
August1st to 10thNight
8%5%25%7%46%6%6%10%41%
1645
11th to 20thNight
9%6%35%6%45%5%6%8%43%
1774
21st to endNight
10%6%26%5%35%5%7%9%43%
1980
September1st to 10thNight
15%6%35%5%3445%7%43%
1800
11th to 20thNight
12%5%25%22446%8%49%
1872
21st to endNight
19%7%35%43446%6%39%
1980
October1st to 10thNight
20%6%25%4345%45%41%
2078
11th to 20thNight
18%5%1432345%6%49%
2160
21st to endNight
18%7%25%42445%6%43%
2482
November1st to 10thNight
13%6%25%423447%50%
2407
11th to 20thNight
16%6%25%434345%46%
2470
21st to endNight
13%5%2443445%7%47%
2493
December1st to 10thNight
18%8%35%5%3445%6%40%
2660
11th to 20thNight
17%5%25%5%345%5%8%41%
3288
21st to endNight
14%8%36%435%5%6%7%39%
4884

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
25%39%8%17%10%1
1518
11th to 20thDay
27%40%9%13%9%1
1486
21st to endDay
28%37%7%17%9%2
1782
February1st to 10thDay
28%36%7%19%11%1
1652
11th to 20thDay
29%36%7%17%9%2
1757
21st to endDay
29%37%6%16%9%3
1480
March1st to 10thDay
23%36%9%20%11%1
1800
11th to 20thDay
28%36%7%17%10%3
1912
21st to endDay
30%36%6%15%10%2
2346
April1st to 10thDay
27%36%7%13%11%5%
2160
11th to 20thDay
27%36%8%15%11%3
2134
21st to endDay
28%37%7%13%11%4
2160
May1st to 10thDay
29%37%8%15%9%2
2312
11th to 20thDay
30%38%7%13%10%2
2418
21st to endDay
26%39%9%16%9%1
2725
June1st to 10thDay
24%39%11%16%8%1
2520
11th to 20thDay
26%39%11%17%6%2
2520
21st to endDay
22%40%11%16%9%1
2520
July1st to 10thDay
23%40%11%15%9%1
2450
11th to 20thDay
20%40%10%20%9%2
2445
21st to endDay
23%41%9%17%9%
2591
August1st to 10thDay
23%39%11%18%8%
2255
11th to 20thDay
27%36%9%17%10%1
2126
21st to endDay
28%38%10%12%9%2
2376
September1st to 10thDay
23%37%9%16%13%3
2160
11th to 20thDay
22%37%6%17%16%2
2088
21st to endDay
30%37%5%12%14%2
1980
October1st to 10thDay
26%36%7%17%13%1
1879
11th to 20thDay
26%36%7%17%12%2
1800
21st to endDay
27%38%6%15%11%1
1872
November1st to 10thDay
22%40%7%19%12%1
1671
11th to 20thDay
25%39%8%14%13%1
1710
21st to endDay
26%40%8%16%9%1
1683
December1st to 10thDay
25%40%10%15%9%
1520
11th to 20thDay
30%32%6%20%12%1
1906
21st to endDay
30%29%11%19%11%
2772
January1st to 10thNight
26%39%7%16%10%1
2649
11th to 20thNight
29%40%9%15%7%1
2599
21st to endNight
27%37%6%19%11%1
2574
February1st to 10thNight
29%35%7%16%12%
2306
11th to 20thNight
29%37%6%14%10%3
2100
21st to endNight
28%35%5%16%13%3
1776
March1st to 10thNight
24%36%8%17%13%2
2160
11th to 20thNight
31%36%6%13%10%3
2044
21st to endNight
31%36%6%13%11%4
2009
April1st to 10thNight
28%36%7%13%12%4
1800
11th to 20thNight
29%35%5%13%14%4
1775
21st to endNight
28%37%6%12%13%4
1800
May1st to 10thNight
32%37%5%13%10%2
1645
11th to 20thNight
31%37%6%10%14%2
1494
21st to endNight
30%38%9%13%9%1
1551
June1st to 10thNight
30%38%7%13%10%1
1440
11th to 20thNight
28%38%9%16%7%2
1440
21st to endNight
25%38%11%16%9%2
1440
July1st to 10thNight
28%40%9%16%5%2
1400
11th to 20thNight
22%40%11%16%10%1
1392
21st to endNight
23%40%9%15%11%1
1486
August1st to 10thNight
26%39%12%15%8%
1635
11th to 20thNight
27%36%9%16%10%1
1774
21st to endNight
27%39%10%12%9%2
1980
September1st to 10thNight
27%36%8%14%13%3
1800
11th to 20thNight
21%36%8%17%15%2
1872
21st to endNight
31%36%412%14%2
1980
October1st to 10thNight
27%37%6%15%14%1
2078
11th to 20thNight
27%36%8%17%10%1
2160
21st to endNight
28%37%6%16%12%1
2482
November1st to 10thNight
19%40%7%17%15%2
2407
11th to 20thNight
26%40%6%15%12%1
2470
21st to endNight
25%39%9%15%12%1
2493
December1st to 10thNight
27%39%8%14%10%1
2660
11th to 20thNight
29%33%8%13%15%2
3288
21st to endNight
34%27%12%19%8%
4884

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
14%12%36%29%8%1
180
11th to 20thDay
17%15%37%26%5%1
172
21st to endDay
23%8%36%22%11%1
264
February1st to 10thDay
22%10%32%29%7%
272
11th to 20thDay
25%12%35%25%4
416
21st to endDay
24%10%34%27%5%
346
March1st to 10thDay
16%10%36%30%8%
420
11th to 20thDay
18%8%32%34%6%2
420
21st to endDay
22%7%31%31%8%1
462
April1st to 10thDay
22%8%32%26%11%1
420
11th to 20thDay
17%5%26%40%11%1
412
21st to endDay
22%6%24%35%11%1
420
May1st to 10thDay
25%424%34%11%2
423
11th to 20thDay
22%318%37%18%2
447
21st to endDay
20%312%27%32%7%
485
June1st to 10thDay
18%213%34%28%6%
450
11th to 20thDay
11%312%41%27%5%
450
21st to endDay
10%210%42%32%4
450
July1st to 10thDay
10%37%31%38%12%
445
11th to 20thDay
426%34%43%11%
444
21st to endDay
11%210%39%33%5%
488
August1st to 10thDay
11%28%37%35%7%
446
11th to 20thDay
14%18%29%38%10%
439
21st to endDay
11%49%32%31%13%
495
September1st to 10thDay
16%214%26%30%13%
450
11th to 20thDay
13%311%32%32%9%
450
21st to endDay
22%6%15%32%21%3
450
October1st to 10thDay
24%414%27%24%7%
450
11th to 20thDay
19%6%18%29%25%4
450
21st to endDay
20%7%26%28%16%3
441
November1st to 10thDay
17%8%24%25%21%4
365
11th to 20thDay
15%12%31%29%12%1
370
21st to endDay
15%12%28%29%15%1
343
December1st to 10thDay
24%9%33%22%11%1
180
11th to 20thDay
23%10%33%25%9%1
180
21st to endDay
20%9%30%25%14%2
198
January1st to 10thNight
20%16%36%22%6%
760
11th to 20thNight
23%14%32%24%6%
744
21st to endNight
19%15%37%25%31
792
February1st to 10thNight
23%13%36%25%4
720
11th to 20thNight
24%13%41%20%2
703
21st to endNight
23%12%35%26%4
592
March1st to 10thNight
19%13%36%26%6%
720
11th to 20thNight
21%9%31%30%8%2
720
21st to endNight
21%6%32%31%8%1
792
April1st to 10thNight
21%10%30%30%8%1
720
11th to 20thNight
18%5%25%38%14%
711
21st to endNight
22%5%26%34%12%1
720
May1st to 10thNight
19%422%38%13%4
565
11th to 20thNight
21%321%41%12%3
432
21st to endNight
19%212%28%34%6%
389
June1st to 10thNight
21%213%32%30%3
360
11th to 20thNight
13%312%41%28%3
360
21st to endNight
9%110%45%31%5%
360
July1st to 10thNight
12%28%39%33%6%
350
11th to 20thNight
7%27%33%44%7%
348
21st to endNight
10%211%36%38%4
394
August1st to 10thNight
11%28%34%40%5%
571
11th to 20thNight
11%110%35%33%9%
710
21st to endNight
12%28%32%36%10%
792
September1st to 10thNight
17%313%28%31%9%
720
11th to 20thNight
16%211%30%33%8%
720
21st to endNight
22%317%31%23%4
720
October1st to 10thNight
23%420%24%21%8%
720
11th to 20thNight
19%8%21%32%18%1
720
21st to endNight
22%10%28%28%11%2
792
November1st to 10thNight
17%9%27%29%14%4
740
11th to 20thNight
19%16%24%29%11%1
760
21st to endNight
15%14%33%27%10%1
760
December1st to 10thNight
23%15%32%22%7%2
760
11th to 20thNight
19%14%37%23%6%1
760
21st to endNight
20%11%35%28%6%
836
Page generated at 2024-01-13 19:28:27. Version ac07

Copyright 2024 Attilla Danko


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