Last night I had another go at gathering some data for X Herculis, using the Canon 500D DSLR on the Skywatcher 80ED Pro. This time it was much more successful. Suitable settings to collect useable data from stars in the range 6 - 9 Visual magnitude are:
400 iso
30 second exposure
Telescope focussed , then defocussed by 75 % of a turn of the fine focusser
Together with suitable flats, bias and dark frames, I processed the images in IRIS (from AAVSO):
The screenshot above shows the calibrated and registered image of X Herculis having its instrumental magnitude being measured. The annulus around the star is used to measure the 'darkness', compared with the inner ring, the star. The same is done for a number of comparison stars and the difference between 'instrumental' magnitudes is added to the magnitude of a star of known magnitude to find the estimated photometric magnitude.
Problems this time:
The field of view for this target is too wide for my telescope, so I need to find a variable star with comparison stars within a 2 degree FOV.
400 iso
30 second exposure
Telescope focussed , then defocussed by 75 % of a turn of the fine focusser
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X Herculis in centre of field
|
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| IRIS data being processed |
The screenshot above shows the calibrated and registered image of X Herculis having its instrumental magnitude being measured. The annulus around the star is used to measure the 'darkness', compared with the inner ring, the star. The same is done for a number of comparison stars and the difference between 'instrumental' magnitudes is added to the magnitude of a star of known magnitude to find the estimated photometric magnitude.
Problems this time:
The field of view for this target is too wide for my telescope, so I need to find a variable star with comparison stars within a 2 degree FOV.
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