Kepler Amateur Blue-Spike (KABS) Observations
Webmaster: Bruce Gary, 2014 Jul 29

This web site lists Kepler candidates needing 2-color observations of transit light curves for the purpose of helping to distinguish between the "exoplanet" interpretation and the "blended eclipsing binary" interpretation for Kepler transit candidates. These two interpretations can be recognized due to the fact that ingress and egress shapes differ due to stellar limb darkening that causes a small transiting object to block more red light near 1st and 4th contacts compared to the smaller effect by a large transiting object (as first demonstrated by Tingley et al, 2014, and described as a theoretical possibility by Rosenblatt, 1971). Differencing the g' and z' magnitudes, for example, produces a "blue spike" just after 1st contact (and just before 4th contact) that can be ~1 mmag. This web page lists Kepler candidates that are most likely to exhibit the "blue spike" effect if the transiting object is an exoplanet (while showing minimal effect if the transiting object is a grazing star). Only advanced amateurs with apertures of 12 inches or greater should attempt such observations. (Anyone who hasn't read this web page before should begin by reading the Introduction section, below.)
Recent Updates: 

Jul 29: Uploaded a list of Kepler candidates needing 2-color transit observations

Feasibility Chart:


Figure 1. Guidance for assessing feasibility of providing useful 2-color transit shape information, based on the star's brightness, transit depth and telescope aperture. The area above the trace is "feasible." For example, a 14-inch telescope observing a star with V-mag = 9.5 can provide "useable" transit observations when transit depth > 10 mmag. This assumes sufficient pre-ingress and post-egress data are available, and the light curve quality is good in other respects. (This graph will be revised as more feasibility observations are obtained.)

Currently Active List(light curves are at KABS LCs)

Figure 2. The "Currently Active List" above is for Kepler candidates with small impact parameter, long period and transit depth > 4 mmag. An approximate correction for BJD-JD has been applied, and all times are UT (i.e., JD).

List of Submitted Observations - Individual LCs are at KABS LCs [not supported yet]   

ymdd K00410.01 P= 07.22 d  Observer: Comments (this is a placeholder line sincve no observations have been submitted yet)

KABS Observed Candidates & Blue-Spike Status

The table below summarizes KABS results (as of 2014.07.28).

[No table here yet]

The "Event" column can be either "tr" for full transit, "ing" for ingress only, "egr" for egress only, "oot" for out-of-transit, and "no sho" for no show.
The "D" column shows depth in mmag.
The "dt" column shows observed mid-transit time minus Kepler ephemeris predicted transit time, in minutes.
The "L" column shows transit length (ingress to egress), in hours.
The "dt/se" column is self evident.
The "bands" column shows which two filters were used
The "color" column is the difference in magnitude after ingress or before egress (short wavelength magnitude minus long wavelength magnitude)
The "Notes" column has miscellaneous info. All "false positives" should be disregarded.


This observing project is "ambitious." In other words, it isn't feasible for most advanced amateurs, and it may not even be feasible for any observers.  This is mostly due to the need for large apertures, which few amateurs have. The purpose for creating it is to find out, empirically, whether amateurs are capable of contributing to the measurement of the "blue spike" feature. 

Submission Instructions

You may send a text file (JD and magnitude columns) to Bruce Gary using the following e-mail address: 


If  you send an attached text file I'll process it to produce a LC, and if it's good quality I'll post it on another web page (KABS LCs) [not supported yet].

Sample LCs

Here are a couple examples of transit quality using typical amateur hardware. The first one is for a 45 mmag deep transit (probably a blended EB) using a 14-inch aperture telescope with g' and i' filters. It's a good example of what we can expect from modest size telescopes observing a single Kepler candidate with a deep transit. The g'-i' magnitude plot exhibits a noise level of ~ 1 mmag per 15 minute average.

Figure 3.  This is an example of what a modest aperture telescope can do with a bright Kepler candidate for a single transit.


Tingley, B. et al, A & A, 2014,
Rosenblatt, F., 1971, Icarus, 14, 71.
NASA Exoplanet Archive, Kepler 5465 List:
Kepler mission home page:
Exoplanet Observing for Amateurs (free book, PDF, or $2 eBook at


WebMaster: B. GaryNothing on this web page is copyrighted. This site opened:  July 29, 2014