17P/Holmes - Photometry


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The Photometry of my comet images is made with MaxIm DL Version 3.22. This program offers a quite good possibility to easily perform the photometry of a series of images.

First I select some reference stars with a magnitude around the comet's mag using TheSky level VI. Only USNO magnitudes are used. The Aperture Radius of the photometry area depends on the size of the inner coma of the comet. In the case of comet 17P/Holmes I selected the aperture of 4. The Gap Width is selected to its maximum size of 10. The Annulus Thickness is set to 5, not too much. The stars should have no neighbors around.

17P (Holmes) � by David Bender, Germany


The result of the photometry made by MaxIm DL is the following graph:

Photometry of 17P (Holmes) � by Bernhard H�usler, Germany

Photometry performed by Bernhard H�usler, Germany

It shows the performed photometry data of all selected reference stars and of the comet. The program is automatically snaping the "moving" comet on all images, no manual work has to be done. Finally I save the data on a .CSV file and load them into an excel sheet.

In this case the photometry curve of the comet seemed to have a regular frequency of  around half an hour with peaks every 45 minutes. Maybe this is an indication of a rotation period. More investigation is necessary.

T (JD)

Ref1

Ref2

Ref3

Ref4

Ref5

Obj1

245.483.138.365

13.976

16.225

17.032

18.594

15.782

17.771

245.483.138.729

13.731

16.040

16.807

19.503

15.528

17.853

245.483.139.094

14.066

16.405

16.986

18.289

15.864

17.990

245.483.139.461

13.819

16.126

16.911

19.139

15.615

18.193

 

 

 

 

 

 

 

average

 

 

 

 

 

17.952

In excel I compute the average values of the object and use the computed value of 17.952 mag for the comet.

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Copyright: The author of NEO Planner and all sites of this web is Bernhard Haeusler, Dettelbach, Germany, all rights reserved