2021-09-28, 03:33 PM
One downside of the CNEOS list is objects drop from the list after close approach. A bright object might still be visible after close approach although it won't be moving as fast. I looked at the Mean Daily Motion field, but it doesn't seem to correspond to the really rapid motion that occurs at close approach. Check out 2021 RG19 & 2021 RM5. 2021 RM5 has n=0.73°/day, but moves 11"/min at close approach, while 2021 RG19 has n=0.21°/day, but moved at ~120"/min. Approach distance plays a big factor too. Lots of factors affect the apparent motion. High relative velocity + small Re = Fast Motion.
An alternative approach to calculating an ephemeris in ST4 would be to open the Object Information dialog at the time of close approach & see how fast it's moving. As BMD has noted, brightness is affected by phase angle which changes rapidly during the pass, so brightness can drop just when the MP is closest to earth. Frustrating.
Good luck hunting,
Phil S.
An alternative approach to calculating an ephemeris in ST4 would be to open the Object Information dialog at the time of close approach & see how fast it's moving. As BMD has noted, brightness is affected by phase angle which changes rapidly during the pass, so brightness can drop just when the MP is closest to earth. Frustrating.
Good luck hunting,
Phil S.