Mon, 05/17/2021 - 03:23
I recently took the exoplanet transit course and captured some data of my own to try. I "think" I did things right, but a darn spreadsheet formula led me to stop imaging too early. DOH! User error.
My question however is why would the predicted ingress/egress still be so far off? Is this typical? Would be great to get some thoughts. See attached info. Thanks so much!
LINK to files
Jeff
Hi Jeff,
Where/how did you obtain the predicted ingress/egress points? NASA's Exoplanet Archive transit prediction service shows that for KPS-1b at McDonald Observatory in Texas (not sure where you are located, but this is also in the Central time zone), the only predicted transits during the month of May are on 5/18, 5/25, and 5/30.
Dennis Conti
Chair, AAVSO Exoplanet Section
Hi Dennis, thanks for responding.
I got the ingress/egress points from the NASA Exoplanet Archive (see screenshot). The transit I was trying to observe occurred on 5/13 UT (from Lake Mills, WI 43.0814° N, -88.9118° E). I mistakenly stopped imaging too soon, but even if I force the predicted ingress/egress points from the NASA Archive on the plot they are off significantly.
Object RA 165.167198 DEC 64.963845
Long/Lat: 43.0814° N, -88.9118° E
Using the online UTC-to-BJD_TBD online converter:
Ingress: 05/13/2021 05:12UT translates to 2459347.716834657 BJD_TBD
Egress: 05/13/2021 06:53UT translates to 2459347.786970445 BJD_TBD
Here's a link to my .plotcfg file and measurements file.
The only thing I can think of is either I'm translating the ingress/egress points wrong or my system clock was off. But I am using Dimension4 to sync my clock precisely.
Any ideas I really appreciate. Of course it's been cloudy or too windy since to try again. I'm eager to give it another go! Thanks!
Jeff
Hi Jeff,
The uncertainty in KPS-1b's period could account for the discrepancy in times.
Dennis