Nereid, the third largest of Neptune’s moons (mag. 18.69) and Minor Planet Christophe

[theskyhound]

I have overlaid Screen Captures from SkyTools 4 Imaging to show some of the field stars as well as the lucky catch of the Minor Planet (1698) Christophe at mag. 16.63 (Diameter: 10 - 31 km). Perihelion Distance is 2.8 AU, Aphelion Distance is 3.5 AU. I haven't updated the Minor Planet database for a few months and wonder if this has led to the slight discrepancy?


When I set the capture time in ST4, the plotted position of Christophe did not match the actual trail in my series of images. In ST4 it seems that Christophe was “behind” the recorded position by 2 or 3 hours? ST4 is set for my back garden location in Brisbane and the Win 10 PC clock was synchronised with the Time Server.

Cheers

Dennis

Hello Dennis,

Nice image! I'm glad to see that Nereid is plotting in the correct position. Osculating elements are only truly accurate for about 40 days or so, and start to lose accuracy after that. So it is important to update your elements if you expect the positions to match closely, especially for asteroids near opposition, where the errors are magnified. Unfortunately, it's not as easy as it once was to obtain accurate and timely orbital elements. The Minor Planet Center has slowly been making changes that has degraded the accuracy of elements, especially for minor planets that do not pass close to the earth. Unfortunately one could write a book on this subject! But there are ways to obtain more up to date elements. For starters I suggest using ASTORB to obtain your elements, and filtering so that you don't add hundreds of thousands of very faint asteroids.