Fair Haven
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fair Haven clear sky chart from 2005-11-05 to 2018-03-21.

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
27%
15561
12%
49246
8%
15530
33%
15530
14%
36369

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 15thNight
9%
780
6%
2716
3%
776
13%
776
4%
2354
January16th to endNight
9%
832
6%
2772
2%
832
15%
832
5%
2371
February1st to 15thNight
7%
764
6%
2482
1%
761
15%
761
5%
2087
February16th to endNight
15%
683
8%
2113
5%
683
20%
683
8%
1712
March1st to 15thNight
16%
780
10%
2226
4%
780
22%
780
11%
1769
March16th to endNight
26%
792
18%
2127
8%
792
34%
792
17%
1552
April1st to 15thNight
23%
718
12%
1796
4%
718
27%
718
17%
1387
April16th to endNight
34%
684
18%
1764
8%
684
39%
684
26%
1202
May1st to 15thNight
38%
394
17%
1474
14%
394
45%
394
17%
966
May16th to endNight
41%
374
17%
1497
16%
374
50%
374
23%
872
June1st to 15thNight
40%
360
13%
1440
12%
360
50%
360
18%
913
June16th to endNight
45%
360
13%
1440
16%
360
53%
360
22%
855
July1st to 15thNight
57%
340
15%
1360
21%
340
61%
340
27%
753
July16th to endNight
57%
376
16%
1418
20%
354
60%
354
28%
778
August1st to 15thNight
52%
536
16%
1607
11%
534
56%
534
31%
987
August16th to endNight
55%
711
22%
1857
12%
711
59%
711
35%
1172
September1st to 15thNight
49%
720
18%
1800
9%
720
52%
720
30%
1214
September16th to endNight
51%
717
24%
1968
18%
717
55%
717
30%
1280
October1st to 15thNight
32%
720
15%
2160
12%
720
38%
720
17%
1543
October16th to endNight
19%
768
9%
2343
5%
768
25%
768
10%
1845
November1st to 15thNight
22%
760
14%
2514
11%
760
29%
760
12%
1848
November16th to endNight
18%
780
12%
2730
8%
780
24%
780
10%
2073
December1st to 15thNight
9%
780
5%
2730
1%
780
14%
780
5%
2282
December16th to endNight
7%
832
4%
2912
0%
832
11%
832
3%
2554

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
16%9%47%6%3445%6%31%
49608
Night
18%12%48%6%34445%26%
49416
Cloud CoverDay
17%9%47%6%3445%6%31%
49618
Night
18%11%48%6%34445%27%
49421
TransparencyDay
53%311%20%9%
49297
Night
58%310%18%9%
49246
SeeingDay
22%14%28%19%10%4
6067
Night
25%15%24%21%11%1
15562

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 15thDay
17%19%7%11%10%5%6%33311%
1552
16th to endDay
15%16%8%14%10%5%5%5%3311%
1804
February1st to 15thDay
17%15%8%15%9%35%43313%
1710
16th to endDay
20%14%6%10%9%35%44416%
1645
March1st to 15thDay
19%15%6%11%6%4433419%
2049
16th to endDay
18%9%36%42335%5%35%
2225
April1st to 15thDay
21%8%36%414346%35%
2152
16th to endDay
17%8%25%424345%41%
2206
May1st to 15thDay
14%7%36%5%35%5%46%38%
2475
16th to endDay
13%5%245%35%46%7%41%
2618
June1st to 15thDay
19%6%25%3345%5%7%37%
2520
16th to endDay
12%4245%35%5%6%9%40%
2520
July1st to 15thDay
10%415%5%35%45%8%44%
2520
16th to endDay
11%325%5%35%5%7%8%40%
2654
August1st to 15thDay
10%425%6%345%6%8%41%
2340
16th to endDay
12%4245%35%5%6%8%42%
2333
September1st to 15thDay
17%5%25%32445%7%41%
2160
16th to endDay
14%7%245%3445%6%42%
1989
October1st to 15thDay
21%8%345%24446%33%
1800
16th to endDay
26%10%36%5%34445%24%
1879
November1st to 15thDay
16%12%38%6%35%5%46%26%
1673
16th to endDay
21%17%6%8%5%23335%20%
1560
December1st to 15thDay
21%21%6%10%6%35%33413%
1560
16th to endDay
21%22%9%12%7%333249%
1664
January1st to 15thNight
20%20%8%12%9%4433410%
2716
16th to endNight
16%18%8%13%10%45%33411%
2772
February1st to 15thNight
17%16%8%16%7%35%33313%
2480
16th to endNight
18%14%7%12%7%35%335%17%
2113
March1st to 15thNight
22%13%6%8%7%3433422%
2214
16th to endNight
19%11%37%42434434%
2127
April1st to 15thNight
22%11%45%5%34346%28%
1796
16th to endNight
18%7%24434446%40%
1764
May1st to 15thNight
18%7%35%5%245%5%6%35%
1474
16th to endNight
13%5%25%4345%6%6%42%
1495
June1st to 15thNight
16%9%26%4245%6%8%34%
1440
16th to endNight
12%425%6%446%5%9%39%
1440
July1st to 15thNight
7%5%25%445%46%7%45%
1440
16th to endNight
10%3244245%6%8%45%
1514
August1st to 15thNight
9%5%25%5%35%5%6%8%41%
1617
16th to endNight
11%4245%2446%8%44%
1857
September1st to 15thNight
17%5%25%324445%42%
1800
16th to endNight
15%5%244345%5%7%42%
1968
October1st to 15thNight
24%8%35%5%33446%30%
2160
16th to endNight
32%10%26%5%25%445%20%
2343
November1st to 15thNight
21%13%47%5%2444426%
2514
16th to endNight
21%17%5%7%5%34446%19%
2730
December1st to 15thNight
23%19%7%11%7%2344412%
2730
16th to endNight
24%22%7%10%8%333339%
2912

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%18%8%13%10%5%5%33311%
1552
16th to endDay
14%17%8%13%9%5%5%44312%
1804
February1st to 15thDay
17%15%8%15%10%35%33313%
1710
16th to endDay
20%13%6%11%10%3334416%
1645
March1st to 15thDay
19%16%6%11%6%35%33319%
2060
16th to endDay
18%10%46%423346%34%
2224
April1st to 15thDay
21%9%35%423347%33%
2152
16th to endDay
18%8%24423345%40%
2206
May1st to 15thDay
15%7%36%5%35%446%37%
2475
16th to endDay
13%5%24425%5%5%7%40%
2618
June1st to 15thDay
20%5%144235%5%7%36%
2520
16th to endDay
13%424435%5%6%9%38%
2520
July1st to 15thDay
10%5%25%5%245%6%7%43%
2520
16th to endDay
11%325%5%35%5%6%9%39%
2654
August1st to 15thDay
11%5%25%5%445%6%9%39%
2340
16th to endDay
12%425%5%35%5%6%8%41%
2333
September1st to 15thDay
18%5%2442445%7%41%
2160
16th to endDay
14%5%25%5%35%45%6%42%
1989
October1st to 15thDay
22%7%35%425%446%32%
1800
16th to endDay
25%10%37%5%3445%5%24%
1879
November1st to 15thDay
17%12%48%6%35%5%5%5%26%
1673
16th to endDay
21%17%5%8%5%24345%20%
1560
December1st to 15thDay
20%21%6%10%6%35%34413%
1560
16th to endDay
21%21%8%13%7%334249%
1664
January1st to 15thNight
19%19%7%12%9%4433410%
2716
16th to endNight
16%18%8%13%10%45%33412%
2772
February1st to 15thNight
17%15%8%15%8%3433413%
2473
16th to endNight
17%15%7%11%9%25%345%17%
2113
March1st to 15thNight
22%13%5%9%6%3323422%
2226
16th to endNight
19%11%47%5%23345%33%
2127
April1st to 15thNight
22%11%46%5%34346%28%
1796
16th to endNight
18%7%245%33446%40%
1764
May1st to 15thNight
19%6%26%5%245%5%6%34%
1474
16th to endNight
12%5%35%4345%6%6%42%
1495
June1st to 15thNight
17%6%35%4245%5%7%35%
1440
16th to endNight
12%5%345%45%5%5%8%40%
1440
July1st to 15thNight
7%5%25%5%35%5%6%7%45%
1440
16th to endNight
11%425%4245%6%8%45%
1514
August1st to 15thNight
9%415%6%35%5%6%9%41%
1617
16th to endNight
11%4245%2445%9%45%
1857
September1st to 15thNight
17%6%24434446%42%
1800
16th to endNight
15%5%14425%5%47%43%
1968
October1st to 15thNight
24%7%26%5%2335%6%30%
2160
16th to endNight
30%11%26%5%34445%21%
2343
November1st to 15thNight
20%14%36%5%34345%27%
2514
16th to endNight
20%16%5%7%5%23446%21%
2730
December1st to 15thNight
23%18%6%11%6%2434314%
2730
16th to endNight
23%21%7%11%7%3333410%
2912

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 15thDay
79%25%9%3
1553
16th to endDay
76%39%7%2
1804
February1st to 15thDay
76%26%11%2
1712
16th to endDay
70%38%13%4
1645
March1st to 15thDay
70%210%11%4
2060
16th to endDay
52%29%21%13%
2225
April1st to 15thDay
51%310%20%12%1
2152
16th to endDay
45%37%24%16%2
2206
May1st to 15thDay
47%410%23%13%1
2475
16th to endDay
41%415%24%13%1
2622
June1st to 15thDay
45%413%24%12%
2520
16th to endDay
40%5%14%25%13%1
2520
July1st to 15thDay
37%5%9%31%15%1
2371
16th to endDay
39%5%16%26%11%
2487
August1st to 15thDay
39%416%26%11%
2327
16th to endDay
39%411%31%11%
2333
September1st to 15thDay
41%410%28%14%
2160
16th to endDay
42%310%29%14%
1989
October1st to 15thDay
51%310%23%10%
1800
16th to endDay
61%314%15%5%
1879
November1st to 15thDay
57%411%17%7%1
1673
16th to endDay
66%210%16%3
1560
December1st to 15thDay
74%310%9%1
1560
16th to endDay
79%37%6%2
1664
January1st to 15thNight
78%25%8%4
2716
16th to endNight
75%38%10%2
2772
February1st to 15thNight
75%27%11%3
2482
16th to endNight
69%210%12%5%
2113
March1st to 15thNight
66%210%14%5%
2226
16th to endNight
53%38%19%12%1
2127
April1st to 15thNight
58%28%18%10%1
1796
16th to endNight
44%39%21%18%2
1764
May1st to 15thNight
49%39%19%14%2
1474
16th to endNight
39%413%26%13%2
1497
June1st to 15thNight
46%411%25%11%
1440
16th to endNight
40%413%22%18%
1440
July1st to 15thNight
34%5%12%27%18%2
1360
16th to endNight
35%413%27%16%2
1418
August1st to 15thNight
37%415%30%10%
1607
16th to endNight
36%312%31%14%1
1857
September1st to 15thNight
42%412%25%15%1
1800
16th to endNight
39%49%29%15%1
1968
October1st to 15thNight
53%39%20%12%
2160
16th to endNight
65%212%13%5%
2343
November1st to 15thNight
59%210%16%8%1
2514
16th to endNight
63%212%16%5%
2730
December1st to 15thNight
74%310%9%2
2730
16th to endNight
79%27%7%1
2912

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 15thDay
21%33%32%8%31
90
16th to endDay
32%25%35%6%
128
February1st to 15thDay
26%39%28%5%
135
16th to endDay
28%27%31%10%2
226
March1st to 15thDay
30%22%26%15%3
330
16th to endDay
25%21%30%16%5%
311
April1st to 15thDay
28%20%29%15%5%1
270
16th to endDay
23%15%27%16%11%5%
270
May1st to 15thDay
25%15%25%18%11%3
288
16th to endDay
19%11%32%21%13%3
331
June1st to 15thDay
23%6%30%25%10%2
315
16th to endDay
15%11%34%25%9%2
315
July1st to 15thDay
14%6%27%32%15%3
305
16th to endDay
13%5%30%26%17%6%
326
August1st to 15thDay
14%5%29%26%14%9%
313
16th to endDay
13%6%26%25%13%14%
332
September1st to 15thDay
17%6%24%23%15%12%
315
16th to endDay
13%9%23%25%15%13%
314
October1st to 15thDay
26%8%24%19%16%4
315
16th to endDay
31%17%30%14%6%
325
November1st to 15thDay
28%17%23%21%8%
237
16th to endDay
26%26%34%11%1
90
December1st to 15thDay
27%26%25%13%6%
90
16th to endDay
36%36%22%4
96
January1st to 15thNight
30%26%27%11%3
780
16th to endNight
26%25%28%16%4
832
February1st to 15thNight
28%24%32%12%2
764
16th to endNight
26%23%30%16%3
683
March1st to 15thNight
29%21%26%18%3
780
16th to endNight
23%20%25%21%8%
792
April1st to 15thNight
27%17%27%23%3
718
16th to endNight
22%14%25%24%12%1
684
May1st to 15thNight
24%5%22%32%13%
394
16th to endNight
14%6%30%30%16%1
375
June1st to 15thNight
19%7%21%30%18%1
360
16th to endNight
13%5%27%39%13%1
360
July1st to 15thNight
9%320%38%25%1
340
16th to endNight
10%221%39%23%2
376
August1st to 15thNight
11%223%35%23%3
536
16th to endNight
14%419%32%26%2
711
September1st to 15thNight
20%5%18%26%26%2
720
16th to endNight
17%8%17%24%25%6%
717
October1st to 15thNight
30%9%19%21%17%1
720
16th to endNight
37%14%24%19%4
768
November1st to 15thNight
28%16%25%19%9%
760
16th to endNight
30%20%24%15%7%1
780
December1st to 15thNight
36%22%25%11%2
780
16th to endNight
35%24%26%11%2
832
Page generated at 2018-03-22 11:34:27. Version ac04

Copyright 2018 A. Danko


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