Troy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Troy 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 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
50%
23629
23%
74456
16%
23573
57%
23573
27%
45820

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
29%
760
23%
2459
10%
757
46%
757
23%
1504
January11th to 20thNight
33%
732
27%
2288
14%
732
47%
732
23%
1419
January21st to endNight
26%
792
28%
2376
11%
792
42%
792
24%
1510
February1st to 10thNight
31%
720
23%
2160
11%
720
42%
720
24%
1401
February11th to 20thNight
31%
702
23%
2099
10%
700
42%
700
25%
1308
February21st to endNight
26%
592
24%
1776
10%
592
38%
592
24%
1149
March1st to 10thNight
34%
720
26%
2160
14%
720
44%
720
29%
1300
March11th to 20thNight
34%
720
22%
2012
11%
720
43%
720
27%
1296
March21st to endNight
37%
792
25%
2178
12%
792
47%
792
30%
1341
April1st to 10thNight
42%
545
26%
1805
20%
545
52%
545
26%
1067
April11th to 20thNight
41%
533
26%
1775
19%
533
53%
533
31%
1012
April21st to endNight
52%
540
31%
1800
24%
540
64%
540
39%
931
May1st to 10thNight
55%
540
27%
1648
18%
540
64%
540
38%
908
May11th to 20thNight
57%
531
18%
1592
14%
531
60%
531
29%
1004
May21st to endNight
69%
582
22%
1744
18%
582
72%
582
33%
1048
June1st to 10thNight
64%
540
15%
1620
14%
540
65%
540
25%
1090
June11th to 20thNight
75%
540
18%
1620
16%
540
76%
540
34%
976
June21st to endNight
71%
540
15%
1620
12%
540
72%
540
25%
1087
July1st to 10thNight
69%
525
8%
1575
8%
525
69%
525
20%
1129
July11th to 20thNight
76%
522
12%
1566
12%
522
76%
522
25%
1063
July21st to endNight
78%
591
15%
1727
16%
558
78%
558
28%
1108
August1st to 10thNight
73%
537
9%
1778
11%
534
73%
534
21%
1203
August11th to 20thNight
70%
534
13%
1776
16%
534
71%
534
21%
1210
August21st to endNight
65%
594
17%
1980
20%
594
66%
594
20%
1372
September1st to 10thNight
67%
623
18%
1883
18%
623
68%
623
25%
1256
September11th to 20thNight
61%
720
19%
1980
14%
720
63%
720
28%
1310
September21st to endNight
65%
720
28%
1980
22%
720
68%
720
33%
1230
October1st to 10thNight
57%
720
28%
1980
21%
720
63%
720
41%
1134
October11th to 20thNight
57%
720
36%
1980
26%
720
66%
720
42%
1107
October21st to endNight
51%
792
32%
2388
27%
792
59%
792
36%
1337
November1st to 10thNight
55%
740
30%
2406
26%
740
64%
740
38%
1257
November11th to 20thNight
44%
760
31%
2470
23%
760
57%
760
34%
1347
November21st to endNight
41%
760
26%
2470
19%
760
53%
760
28%
1463
December1st to 10thNight
40%
760
26%
2470
18%
760
52%
760
26%
1480
December11th to 20thNight
35%
759
24%
2909
15%
758
45%
758
20%
1772
December21st to endNight
32%
831
16%
4406
14%
817
43%
817
13%
2691

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
11%6%35%5%45%5%6%8%41%
74822
Night
11%6%25%5%345%6%8%45%
74927
TransparencyDay
39%7%11%18%18%6%
74549
Night
37%7%11%17%20%8%
74719
SeeingDay
14%8%21%24%21%12%
13593
Night
14%8%22%29%22%5%
23638

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
17%7%35%42335%7%45%
1706
11th to 20thDay
13%7%35%434446%46%
1730
21st to endDay
16%7%36%42435%5%45%
1980
February1st to 10thDay
15%8%36%5%35%45%5%40%
1800
11th to 20thDay
17%7%35%32346%7%43%
1748
21st to endDay
16%7%36%5%35%5%5%7%38%
1480
March1st to 10thDay
12%6%35%6%24446%49%
1800
11th to 20thDay
14%6%36%5%35%5%5%8%40%
1947
21st to endDay
13%5%25%6%35%46%7%45%
2186
April1st to 10thDay
12%5%36%43445%7%46%
2160
11th to 20thDay
11%6%25%6%3445%7%47%
2134
21st to endDay
7%425%435%45%7%55%
2160
May1st to 10thDay
8%435%5%3446%7%52%
2309
11th to 20thDay
6%5%26%6%5%6%6%8%10%41%
2301
21st to endDay
8%5%25%6%46%6%7%10%43%
2531
June1st to 10thDay
8%6%47%6%5%7%7%9%10%32%
2340
11th to 20thDay
7%325%7%46%8%9%11%37%
2340
21st to endDay
6%5%37%8%6%9%8%9%10%30%
2340
July1st to 10thDay
9%5%37%8%6%8%9%9%11%25%
2340
11th to 20thDay
10%6%36%6%6%8%8%9%10%28%
2340
21st to endDay
6%436%8%5%7%8%9%14%30%
2485
August1st to 10thDay
7%5%35%7%6%8%9%9%13%28%
2148
11th to 20thDay
10%7%47%8%5%7%7%8%9%29%
2125
21st to endDay
10%7%46%7%5%8%7%8%8%30%
2376
September1st to 10thDay
10%6%36%6%5%6%8%8%9%34%
2057
11th to 20thDay
12%7%26%5%36%6%6%9%38%
1980
21st to endDay
10%426%5%45%5%5%8%46%
1980
October1st to 10thDay
9%5%25%435%45%6%52%
1980
11th to 20thDay
11%42342335%8%54%
1980
21st to endDay
10%5%24425%446%54%
1960
November1st to 10thDay
10%5%25%424446%55%
1672
11th to 20thDay
12%6%24324436%54%
1710
21st to endDay
14%6%34425%35%7%47%
1710
December1st to 10thDay
14%5%35%5%245%5%6%45%
1710
11th to 20thDay
16%8%36%5%33435%42%
2153
21st to endDay
20%7%35%434435%42%
3124
January1st to 10thNight
14%8%245%23445%47%
2459
11th to 20thNight
14%9%35%33435%6%45%
2288
21st to endNight
15%8%35%423345%45%
2376
February1st to 10thNight
16%8%36%43445%6%42%
2160
11th to 20thNight
18%7%24333345%49%
2098
21st to endNight
15%8%35%5%3445%6%42%
1776
March1st to 10thNight
11%6%36%42345%6%50%
2160
11th to 20thNight
11%6%36%5%3446%8%43%
2012
21st to endNight
11%6%3443445%7%49%
2178
April1st to 10thNight
12%5%25%5%25%5%5%7%47%
1805
11th to 20thNight
11%6%25%42446%9%48%
1775
21st to endNight
7%323425%46%7%57%
1800
May1st to 10thNight
6%4245%2445%8%55%
1648
11th to 20thNight
7%5%26%6%45%6%7%9%43%
1592
21st to endNight
7%425%5%36%6%7%10%45%
1744
June1st to 10thNight
9%6%36%6%5%6%5%8%10%35%
1620
11th to 20thNight
5%425%446%5%8%13%45%
1620
21st to endNight
5%437%7%5%7%7%9%12%35%
1620
July1st to 10thNight
6%5%27%7%48%9%11%15%28%
1620
11th to 20thNight
7%425%6%46%6%9%14%37%
1620
21st to endNight
4425%5%47%7%8%14%39%
1829
August1st to 10thNight
6%5%36%6%5%7%9%10%14%29%
1790
11th to 20thNight
7%7%26%6%5%7%7%9%11%33%
1776
21st to endNight
11%6%36%6%46%6%7%9%35%
1980
September1st to 10thNight
8%6%45%6%46%6%9%10%36%
1883
11th to 20thNight
11%6%26%6%35%6%5%8%42%
1980
21st to endNight
7%6%25%5%35%5%6%7%48%
1980
October1st to 10thNight
7%5%24433447%57%
1980
11th to 20thNight
9%42342445%6%58%
1980
21st to endNight
11%5%24423335%56%
2388
November1st to 10thNight
9%413324446%59%
2406
11th to 20thNight
12%5%14323346%56%
2470
21st to endNight
13%5%25%5%3445%5%49%
2470
December1st to 10thNight
14%7%25%42345%8%47%
2470
11th to 20thNight
16%6%35%5%23445%46%
3042
21st to endNight
18%8%36%5%345%5%6%39%
4532

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
40%46%17%27%7%
1707
11th to 20thDay
39%5%7%15%24%9%
1730
21st to endDay
42%46%16%24%9%
1980
February1st to 10thDay
46%5%7%15%19%9%
1800
11th to 20thDay
42%46%17%23%9%
1758
21st to endDay
45%5%7%17%17%10%
1480
March1st to 10thDay
37%47%19%22%11%
1800
11th to 20thDay
42%7%10%15%19%8%
1947
21st to endDay
37%5%9%20%21%7%
2186
April1st to 10thDay
38%6%9%21%17%10%
2160
11th to 20thDay
37%48%20%22%9%
2134
21st to endDay
28%6%9%25%27%5%
2160
May1st to 10thDay
30%6%9%25%24%6%
2309
11th to 20thDay
35%10%14%21%19%2
2305
21st to endDay
35%8%12%23%19%3
2531
June1st to 10thDay
43%9%15%21%10%2
2340
11th to 20thDay
36%10%19%21%12%2
2340
21st to endDay
43%12%17%17%9%2
2340
July1st to 10thDay
47%14%19%14%6%1
2275
11th to 20thDay
44%14%21%15%5%1
2271
21st to endDay
39%12%22%20%6%
2346
August1st to 10thDay
42%12%21%21%4
2136
11th to 20thDay
47%11%19%14%8%1
2125
21st to endDay
47%11%17%14%9%2
2376
September1st to 10thDay
42%11%16%13%14%4
2057
11th to 20thDay
43%8%12%16%17%5%
1980
21st to endDay
36%7%10%18%23%6%
1980
October1st to 10thDay
32%5%10%19%22%12%
1980
11th to 20thDay
29%47%21%27%11%
1980
21st to endDay
32%36%13%30%17%
1960
November1st to 10thDay
31%47%17%27%14%
1672
11th to 20thDay
33%47%15%27%14%
1710
21st to endDay
37%49%18%21%11%
1710
December1st to 10thDay
40%5%11%16%21%7%
1710
11th to 20thDay
47%4415%23%8%
2150
21st to endDay
45%4420%21%5%
3124
January1st to 10thNight
40%47%16%24%9%
2459
11th to 20thNight
41%46%16%25%8%
2288
21st to endNight
42%35%13%27%10%
2376
February1st to 10thNight
43%47%16%19%11%
2160
11th to 20thNight
40%46%14%23%13%
2099
21st to endNight
43%48%17%15%13%
1776
March1st to 10thNight
36%47%17%22%14%
2160
11th to 20thNight
40%5%12%15%18%10%
2012
21st to endNight
35%5%9%20%23%9%
2178
April1st to 10thNight
36%5%9%16%21%12%
1805
11th to 20thNight
34%49%20%23%10%
1775
21st to endNight
26%48%28%25%9%
1800
May1st to 10thNight
28%6%11%20%27%8%
1648
11th to 20thNight
35%9%16%17%17%6%
1593
21st to endNight
30%10%16%20%19%5%
1745
June1st to 10thNight
40%10%16%20%14%1
1620
11th to 20thNight
30%9%22%24%13%2
1620
21st to endNight
37%13%17%20%10%3
1620
July1st to 10thNight
38%19%23%13%5%1
1575
11th to 20thNight
35%16%27%15%6%1
1566
21st to endNight
31%15%24%23%7%
1727
August1st to 10thNight
36%17%23%21%21
1778
11th to 20thNight
41%13%21%15%8%3
1776
21st to endNight
44%11%16%15%10%3
1980
September1st to 10thNight
40%10%17%14%13%7%
1883
11th to 20thNight
39%8%13%17%16%6%
1980
21st to endNight
34%7%11%17%22%9%
1980
October1st to 10thNight
28%5%11%18%24%14%
1980
11th to 20thNight
27%48%19%30%12%
1980
21st to endNight
32%35%15%26%19%
2388
November1st to 10thNight
28%37%19%25%18%
2406
11th to 20thNight
31%36%15%31%14%
2470
21st to endNight
37%47%18%21%13%
2470
December1st to 10thNight
37%5%9%19%23%6%
2470
11th to 20thNight
42%46%12%29%8%
3044
21st to endNight
45%5%6%18%22%4
4532

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
23%17%39%17%4
270
11th to 20thDay
19%17%36%18%8%2
248
21st to endDay
22%23%38%13%31
264
February1st to 10thDay
28%22%30%18%3
240
11th to 20thDay
28%20%36%13%2
240
21st to endDay
18%22%45%13%2
198
March1st to 10thDay
18%21%38%19%5%
240
11th to 20thDay
18%16%35%21%9%1
387
21st to endDay
17%18%31%25%9%1
462
April1st to 10thDay
18%16%27%24%13%2
420
11th to 20thDay
15%11%35%22%13%3
412
21st to endDay
10%10%28%32%15%5%
420
May1st to 10thDay
9%9%26%28%23%5%
423
11th to 20thDay
8%320%34%24%11%
447
21st to endDay
11%414%29%23%19%
485
June1st to 10thDay
11%311%32%28%16%
450
11th to 20thDay
10%310%27%32%19%
450
21st to endDay
6%214%25%30%23%
450
July1st to 10thDay
8%27%20%36%27%
445
11th to 20thDay
7%25%16%36%34%
444
21st to endDay
326%23%36%31%
488
August1st to 10thDay
10%26%17%34%31%
446
11th to 20thDay
10%16%20%36%28%
439
21st to endDay
10%39%23%31%23%
495
September1st to 10thDay
12%29%22%35%21%
450
11th to 20thDay
16%210%30%30%13%
450
21st to endDay
11%115%29%32%12%
450
October1st to 10thDay
12%5%24%32%21%6%
450
11th to 20thDay
13%5%20%32%23%7%
450
21st to endDay
16%10%25%27%20%3
433
November1st to 10thDay
18%8%25%32%12%4
270
11th to 20thDay
16%13%37%24%9%1
270
21st to endDay
14%16%36%26%7%1
270
December1st to 10thDay
22%14%34%23%7%1
270
11th to 20thDay
30%17%30%19%4
270
21st to endDay
26%11%32%24%6%1
297
January1st to 10thNight
20%16%31%27%6%1
760
11th to 20thNight
18%16%28%28%9%
732
21st to endNight
20%14%36%26%4
792
February1st to 10thNight
21%12%31%29%7%
720
11th to 20thNight
22%13%31%27%7%
703
21st to endNight
19%14%37%28%3
592
March1st to 10thNight
13%14%35%32%6%
720
11th to 20thNight
13%13%35%26%13%
720
21st to endNight
15%13%31%29%11%
792
April1st to 10thNight
15%11%28%32%14%1
545
11th to 20thNight
13%10%32%25%18%2
533
21st to endNight
7%7%28%36%21%1
540
May1st to 10thNight
9%427%32%25%4
540
11th to 20thNight
8%421%34%29%5%
531
21st to endNight
9%111%35%38%6%
584
June1st to 10thNight
12%210%34%34%9%
540
11th to 20thNight
6%29%32%40%12%
540
21st to endNight
5%18%30%44%11%
540
July1st to 10thNight
8%25%22%47%17%
525
11th to 20thNight
8%1320%44%22%
522
21st to endNight
415%27%48%15%
591
August1st to 10thNight
9%1425%38%24%
537
11th to 20thNight
9%35%20%51%12%
534
21st to endNight
12%37%24%38%16%
594
September1st to 10thNight
11%18%26%41%13%
623
11th to 20thNight
14%210%35%32%7%
720
21st to endNight
11%213%31%37%6%
720
October1st to 10thNight
8%323%37%24%4
720
11th to 20thNight
11%5%22%31%28%3
720
21st to endNight
14%6%23%33%21%2
792
November1st to 10thNight
11%6%24%36%22%3
740
11th to 20thNight
14%10%28%32%15%1
760
21st to endNight
17%10%27%30%14%1
760
December1st to 10thNight
17%11%28%31%12%1
760
11th to 20thNight
21%8%31%29%10%1
760
21st to endNight
25%11%27%28%9%
836
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