07-02-2017, 01:17 AM
Rumata had posted this question on another thread but I've moved and made a specific thread for his question as follows;
Gentlemen, I have a question regarding planning for twilight phenomena observation. But before some wordy stuff, sorry.
The situation: In a morning I plan for sunset phenomena observation. I understand that below is the way to do it.:
1. From NA find LMT for sunset, civil and nautical based on the MOST RECENT FIX OR DR LATITUDE. ( emphasize by caps).
2. Find GMT by converting most recent fix or DR longitude into time and add/subtract it to LMT
3. Find from NA GHA of Aries for this GMT and calculate LHA of Aries
4. Pub.249 gives a list of stars as a function of LHA Aries and latitude OF THE MOST RECENT FIX OR DR.
i think that more correct approach would be:
1. Calculate assumed distance travelled considering time of civil twilight as the time of a new DR ( v* (time of last fix/DR - time of civil twilight).
2. Plot it and find latitude and longitude at the new assumed DR.
3. Using these latitude and longitude do items 1-4 from the paragraph above.
I suppose that in this case latitude and longitude would really correspond to the twilight phenomena and to LHA Aries than the values taken at the current location, presumably 10 hours earlier.
There is my question: does my guess make some sense?
Thank you
Gentlemen, I have a question regarding planning for twilight phenomena observation. But before some wordy stuff, sorry.
The situation: In a morning I plan for sunset phenomena observation. I understand that below is the way to do it.:
1. From NA find LMT for sunset, civil and nautical based on the MOST RECENT FIX OR DR LATITUDE. ( emphasize by caps).
2. Find GMT by converting most recent fix or DR longitude into time and add/subtract it to LMT
3. Find from NA GHA of Aries for this GMT and calculate LHA of Aries
4. Pub.249 gives a list of stars as a function of LHA Aries and latitude OF THE MOST RECENT FIX OR DR.
i think that more correct approach would be:
1. Calculate assumed distance travelled considering time of civil twilight as the time of a new DR ( v* (time of last fix/DR - time of civil twilight).
2. Plot it and find latitude and longitude at the new assumed DR.
3. Using these latitude and longitude do items 1-4 from the paragraph above.
I suppose that in this case latitude and longitude would really correspond to the twilight phenomena and to LHA Aries than the values taken at the current location, presumably 10 hours earlier.
There is my question: does my guess make some sense?
Thank you