Ingress/Egress predicted points off?

Affiliation
American Association of Variable Star Observers (AAVSO)
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

Affiliation
American Association of Variable Star Observers (AAVSO)
Ingress/Egress predicted points

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

Affiliation
American Association of Variable Star Observers (AAVSO)
NASA Archive

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