https://www.merriam-webster.com/dictionary/noctilucent%20cloud
NOCTILUCENT CLOUD Definition & Meaning - Merriam-Webster
The meaning of NOCTILUCENT CLOUD is a luminous thin usually colored cloud seen especially at twilight at a height of about 50 miles (80 kilometers).
noctilucent clouddefinitionmeaningmerriamwebster
https://www.spaceweather.com/nlcs/gallery2011_page4.htm
Noctilucent Cloud Photo Gallery -- Summer 2011: Page 4
cloud photo gallerysummer 2011noctilucent4
https://www.spaceweather.com/nlcs/gallery2006_page1.htm?PHPSESSID=elntv2qdoqonsqirsijd1dbi43&PHPSESSID=dqfgb3fttdbf8vpknr6op6d0m2
Noctilucent Cloud Gallery -- Summer 2006: Page 1
noctilucent cloudsummer 2006gallery1
https://www.spaceweather.com/nlcs/gallery2008_page12.htm?PHPSESSID=elntv2qdoqonsqirsijd1dbi43&PHPSESSID=hg1vfm70fgtphmp20mo23saeu0
Noctilucent Cloud Photo Gallery -- Summer 2008: Page 12
cloud photo gallerysummer 2008noctilucent12
https://www.spaceweather.com/nlcs/gallery2008_page10.htm?PHPSESSID=ur83r4f2j6sev54jr38ktq1jc1
Noctilucent Cloud Photo Gallery -- Summer 2008: Page 10
cloud photo gallerysummer 2008noctilucent10
https://www.spaceweather.com/nlcs/gallery2011.htm?PHPSESSID=elntv2qdoqonsqirsijd1dbi43&PHPSESSID=hg1vfm70fgtphmp20mo23saeu0
Noctilucent Cloud Photo Gallery -- Summer 2011: Page 1
cloud photo gallerysummer 2011noctilucent
https://spaceweather.com/nlcs/gallery2004_page1.html
Spaceweather.com: Noctilucent Cloud Gallery: 2004
noctilucent cloudspaceweathergallery2004
https://www.spaceweather.com/nlcs/gallery2007_page7.htm
Noctilucent Cloud Gallery -- Summer 2007: Page 6
noctilucent cloudsummer 2007gallery6
https://www.spaceweather.com/nlcs/gallery2004_page1.html?PHPSESSID=elntv2qdoqonsqirsijd1dbi43&PHPSESSID=hg1vfm70fgtphmp20mo23saeu0
Spaceweather.com: Noctilucent Cloud Gallery: 2004
noctilucent cloudspaceweathergallery2004