Moons crescent phase orientation tilts from 2:00 to 4:00 direction in just 2 hours | |
Invisible light User ID: 72741226 ![]() 08/30/2017 11:59 PM Report Abusive Post Report Copyright Violation | |
Anonymous Coward User ID: 75461152 ![]() 08/31/2017 07:02 AM Report Abusive Post Report Copyright Violation | Interesting observation: explain to me as if I were 5 please? Quoting: Invisible light 72741226 I understand what you are talking about but the details are fuzzy for me. Idk if i could say it any simpler. After 2 more hours it was pointing in the 5 oclock position, that is, take the crescent, divide it hy half, the exact middle is what im talking about where its pointing. Like you were rotating a black and white half moon cookie on a clock. |
Hydra User ID: 32557845 ![]() 08/31/2017 07:07 AM Report Abusive Post Report Copyright Violation | The lit portion of the moon tilts from 2 oclock when the sun is setting, pointing away from where the suns direction is coming from mind you, to 4 oclock where the sun then sets from our perspectivd after about 2 hours later. Quoting: Anonymous Coward 74336040 Been seeing this happen consistently for several days now. Can anybody explain this? Search term of the day: moon field rotation . :ase26122019: Annular Solar Eclipse - December 26, 2019 - Kannur, Kerala, India |
Anonymous Coward User ID: 73146479 ![]() 08/31/2017 07:10 AM Report Abusive Post Report Copyright Violation | |
Anonymous Coward User ID: 75461152 ![]() 08/31/2017 07:15 AM Report Abusive Post Report Copyright Violation | The lit portion of the moon tilts from 2 oclock when the sun is setting, pointing away from where the suns direction is coming from mind you, to 4 oclock where the sun then sets from our perspectivd after about 2 hours later. Quoting: Anonymous Coward 74336040 Been seeing this happen consistently for several days now. Can anybody explain this? Search term of the day: moon field rotation . Thought this only applies to cameras with an az mount, whereas we can just easily turn our heads. "Im not saying its field rotation, but its field rotation" |
Anonymous Coward User ID: 75461152 ![]() 08/31/2017 07:15 AM Report Abusive Post Report Copyright Violation | |
poor richard User ID: 75463450 ![]() 08/31/2017 07:23 AM Report Abusive Post Report Copyright Violation | |
Hydra User ID: 32557845 ![]() 08/31/2017 07:51 AM Report Abusive Post Report Copyright Violation | The lit portion of the moon tilts from 2 oclock when the sun is setting, pointing away from where the suns direction is coming from mind you, to 4 oclock where the sun then sets from our perspectivd after about 2 hours later. Quoting: Anonymous Coward 74336040 Been seeing this happen consistently for several days now. Can anybody explain this? Search term of the day: moon field rotation Thought this only applies to cameras with an az mount, whereas we can just easily turn our heads. "Im not saying its field rotation, but its field rotation" Did you turn your head during your observation in the way an EQ mount would turn? Or stayed the horizon horizontal during your observation in the way an AZ mount would move? . :ase26122019: Annular Solar Eclipse - December 26, 2019 - Kannur, Kerala, India |
Hydra User ID: 32557845 ![]() 08/31/2017 08:05 AM Report Abusive Post Report Copyright Violation | Earth is rotating on all 3 Axis since 03/11/11 9.1 earthquake. Sorry Quoting: Anonymous Coward 73146479 What's about the mag 9.5 on Mai 22, 1960? Or the mag 9.2 on March 28, 1964? The mag 9.1 on December 26, 2004? How do you come to the conclusion that Earth started "rotating on all 3 Axis" just after the Japan earthquake? . :ase26122019: Annular Solar Eclipse - December 26, 2019 - Kannur, Kerala, India |
Anonymous Coward User ID: 74729691 ![]() 08/31/2017 08:08 AM Report Abusive Post Report Copyright Violation | The lit portion of the moon tilts from 2 oclock when the sun is setting, pointing away from where the suns direction is coming from mind you, to 4 oclock where the sun then sets from our perspectivd after about 2 hours later. Quoting: Anonymous Coward 74336040 Been seeing this happen consistently for several days now. Can anybody explain this? Search term of the day: moon field rotation Thought this only applies to cameras with an az mount, whereas we can just easily turn our heads. "Im not saying its field rotation, but its field rotation" Did you turn your head during your observation in the way an EQ mount would turn? Or stayed the horizon horizontal during your observation in the way an AZ mount would move? . The latter im assuming since i just look at it, im not tilting my head thats for sure. But labeling a phenomenon doesnt explain it, it just names it. For example, the earth has gravity. Okay but wth is it? |
The Gentle Astromut![]() Senior Forum Moderator 08/31/2017 08:18 AM ![]() Report Abusive Post Report Copyright Violation | Thought this only applies to cameras with an az mount, whereas we can just easily turn our heads. "Im not saying its field rotation, but its field rotation" Did you turn your head during your observation in the way an EQ mount would turn? Or stayed the horizon horizontal during your observation in the way an AZ mount would move? . The latter im assuming since i just look at it, im not tilting my head thats for sure. But labeling a phenomenon doesnt explain it, it just names it. For example, the earth has gravity. Okay but wth is it? Field rotation is a natural consequence of viewing the Moon from a non-polar aligned perspective. It's demanded by the geometry of the situation and simple math shows that it is quite normal. Take the equatorial coordinates and add .25 degrees to declination (approximate radius of the moon). This will give you the equatorial coordinates of both the center point of the moon and the north point of the moon on the equatorial grid. Then calculate the position angle of the moon's bright limb relative to the north equatorial point. This is given by the following equation: X = arctan((cos(declination of the sun)*Sin(right ascension of the sun - right ascension of the moon))/(cos(declination of the moon)*sin(declination of the sun)-sin(declination of the moon)*cos(declination of the sun)*cos(right ascension of the sun - right ascension of the moon))) Then to calculate for field rotation, convert the equatorial coordinates of both the center point and the north point to horizon coordinates. This is given by the following formulae. For azimuth, the formula is: tan(az)=(-sin(Hour angle in degrees +delta)*cos(declination))/(sin(declination)*cos(latitude)-cosnope(declination)*sin(latitude)*cos(hour angle in degrees+delta)) where delta is: tan(delta)=(p*cos(theta')*sin(hour angle in degrees))/((distance of moon in km/6378.14)*cos(declination)-p*cos(theta')*cos(hour angle in degrees)) For altitude the formula is: sin(altitude)=(sin(declination)*sin(latitude))/(cos(declinatinopeon)*cos(latitude)*cos(hour angle in degrees)) Now once you have converted both the center point and north point to altitude and azimuth, take the difference of each (altitude and azimuth) between the north and center points to find delta alt and delta az. From there, calculate the angle of the line from the center point to north point relative to the horizon: arctan(delta alt/delta az) Then add the position angle of the moon. In order to express the resulting orientation angle of the moon relative to the horizon as I have (as an angle expressed as degrees from vertical from 0 to 90 degrees) follow these directions: angle1 = arctan(delta alt/delta az) If angle1 > 360, then take angle-360 = angle2, otherwise angle1 = angle2. If angle2 >90 and less than or equal to 180, then take (90-angle2)+90 = angle3, otherwise angle2 = angle3. If angle2 = angle3 and angle2 > 180 and less than or equal to 270, then take the absolute value of (180-angle2) = angle4, otherwise angle3 = angle4. Finally, if angle4 = angle2 and angle 2 > 270, then take (90-(angle2-180)+90) = angle5, otherwise angle4 = angle5. Angle5 is the final answer and the apparent orientation of the moon relative to the horizon expressed as the angle from 0 to +90 degrees from vertical. Last Edited by Astromut on 08/31/2017 08:18 AM ![]() |
Aman User ID: 75399635 ![]() 08/31/2017 09:38 AM Report Abusive Post Report Copyright Violation | put string around them and pull the two ends forming an isosceles acute triangle (pyramid) with the string between the two fingers as the base; ensure the two sides are the same length and the pinnacle of the pyramid should be centered on the base string. line that base line up with the moons terminator line ensuring the pinnacle of the string-pyramid is centered with the moons center and the base string center: does the pinnacle of the string-pyramid point to the center of the sun? |