LOTIS Planetary Transit Search Project

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Spectral Instruments model 800 with EV2 CCD. Linearity regime 0-80% of full well (16bit, so 80%=52k). QE is 85% in V, 80% in R, and 70% in I, roughly.

Use ECU on Dell laptop to get alt's at critical times, using UTC from Greg's email. Format submission line using KPNO local time = PDT.

ClearSkyClock for KPNO

Send me an email to Grant Williams (gwilliams as.arizona.edu) providing a formatted observing queue entry. The format per target is just a space separated line with the following information:

hr min ra dec epoch exp(sec) nimages/filter filters(VRIH) : object

and an example line is:

03 30 153914.0 -001400.0 2000.0 30 5 VRI : SA107

Note that the time is local (Arizona) time, RA has the format hhmmss.s and Dec has the format +/-ddmmss.s and you can include more than one filter. The object name should have no spaces (use underscores).

The overhead per target for reading out the image and writing to disk is currently 15 seconds. That value is currently hardwired into the scheduler although the actual readout and write is probably closer to 7 seconds.

The system obtains flats, biases and darks in the evening so your request should not be scheduled for any earlier than 18 degree twilight.

Finally, because several research groups are submitting to the queue it will be very much appreciated if you provide a brief statement about how time critical your observations are. Obviously for transits the time and day are crucial but the total observing time may be adjustable; I'd appreciate knowing that so that I can ensure everyone's observations get completed and are useful. Occasionally two observations conflict and in that case I'll usually contact both groups to try to work something out.

Observations posted at: http://slotis.kpno.noao.edu/~slotis/data/ and log of what was observed is here: http://slotis.kpno.noao.edu/logs/observations/

Our Transit Observations:

Oct 12/13 2009: CoRot-2 in R (for testing software). (star is saturated though. Here's CoRoT-2 parameters)

Oct 13/14 2009: TrES-2 in R (for testing software)

Jan 12/13 2010: SAO's for pointing acc testing

Jan 13/14 2010: SAO's for pointing acc testing

Jan 14/15 2010: SAO's for pointing acc testing

Jan 15/16 2010: SAO's for pointing acc testing

Jan 16/17 2010; SAO's for pointing acc testing

sLOTIS magnitude accuracy vs magnitude. Points are variance in actual stars, Curve is theoretical. From Blake etal (2002)

Using a 108 angstrom wide filter in the blue


Software pipe line sources:

Pietrukowicz etal "Millimag Photometry for Transiting ExoPlanets Candidates V."

Difference Image Analysis Package DIAPL

from Pietrukowicz etal, 8.2m scope and 16bit CCD saturate at 15 sec for V=15.4 under ideal seeing. 0.6m scope has 1/187 of the light gathering power, so requires 2802 sec to reach saturation at same plate scale. But LOTIS pixels are 5.94 times the area of the VIMOS pixels on the sky, so that cuts the time to saturation to 472 sec for V=15.4 star, or 47 sec for V=10.4 star. Now that's for equivalent seeing. But the seeing at Paranal is 1.0" this decade, so at KPNO the star light is spread over another (2.0/1.0)**2 = 4x the area, so saturation would be 4x longer or 188sec. 80% saturation is upper limit of linearity, so 150 sec is max.

80% full well reached at ~150sec for V=10.4 on LOTIS assuming same QE as VIMOS on VLT. NO! this is too long by x18. Saturation reached on CoRoT-2 before 60 sec and it's R=12.01, V=12.57. Source of error? Probably very different gain settings on VIMOS vs. our chip.


Basic photometry equations , color indices vs. spectral type


IDL Language

NASA Goddard IDL library functions

a Free IDL: GDL

Systemic Link on Greg's site

The ExtraSolar Planets Encyclopedia


Everett and Howell "A Technique of Ultra High Precision UBVRI Photometry", PASP 2001 (pdf)

Pepper and Gaudi "Toward the Detection of Transiting Hot Earths and Hot Neptunes in Open Clusters", Acta Astronomica 2006 (ref max efficiency of transit detection in I-band)

Hartman etal (2005) "Pushing the Limits of Ground-Based Photometric Precision -- Sub-Millimagnitude Time-Series Photometry of the Open Cluster NGC 6791"

Pepper and Gaudi "Searching for Transiting Planets in Stellar Systems", 2005 ApJ 631,581

Free C++ compilers: http://www.thefreecountry.com/compilers/cpp.shtml

Google Stella 2 Photometry, top link

ISIS Photometry package: http://ascl.net/isis.html

For modelling transiting planet parameters: Mandel and Agol (2002)

Error estimation in transits - "Rosemary Bead" method: Bouchy etal (2005)