Hi Folks:
I've been working my way through the learning materials and have completed the photometry phase with the 'sample images' that Dennis has provided. Before I begin the 'Transit Modeling' phase, I'm hoping some of you experienced folks could help with some questions I've encountered along the way ... in no particular order:
1. I carefully set the apertures on the Target and 3 Comp stars but after I ran the photometry routine I noticed that the something had shifted and the stars were all closer to the aperture boundaries than when I placed them. Is there something I need to be doing 'as I place the apertures', to ensure that they stay in place close to the star centroids?
2. When I initiated the photometry, a window opened saying "unable to parse date" followed by the JD. Does this indicate that I did something incorrectly or is it a glitch in the application? Does this imply that the resulting Measurements Table is invalidated?
3. I'm curious what the meaning is of the alphanumeric string that appears after the 'T' and 'C's', eg. TI=5.734E5. It appears to be an exponent number but it doesn't seem to relate to any of the Measurements Table numbers for T1.
4. Is there anywhere in the process where we enter the magnitudes of the comp stars or is all based on the differentials? I realize we need to know the magnitudes when selecting comp stars, but wasnt sure if there was anywhere in the multitudinous windows where that data gets entered.
I'll stop with these 4 and look forward to any responses to keep me crawling up the learning curve.
Thank you!
Gary
Hi Gary,
I will try to answer your questions:
1. Make sure that you have "centroiding" enabled on the Image Display before you place the apertures (it is one of the icons on top of the image that when you hover your cursor it says "centroid apertures."
2. It is not a problem with AIJ - it probably means that the JD keyword in your FITS header is messed up. Please send me a sample .fits file to dennis@astrodennis.com and I will take a look.
3. It is the integrated counts of T1 - namely after subtracting out the contribution of sky background and should relate to Source-Sky counts in the measurement table.
4. No need to enter magnitudes of comps - AIJ uses the flux measurements.
Dennis
Hi Dennis:
1. I had centroiding enabled before I placed the apertures. I'll try again but it will be the third attempt to try and get the apertures to stay put.
2. I'm assuming you want the entire image and the embedded Fits Header. These are your sample files but I did the image reductions and updated the Fits Header per the 'Cookbook' section B.7. If I can't attach the image, I'll send a screenshot of the Fits Header.
3. Understood.
4. Understood.
Thank you Dennis
Gary