Using a DSLR to Study Variable Stars

Canon 450D - linear over a magnitudeusing RAW images with a specific setting

Canon 85 mm fixed lens-can be used to do precise estimates down to magnitude 8 ( undriven ).

Canon 200 mm fixed lens-can be used to do precise estimates down to magnitude 10 ( undriven ).

Precision Photometry

Eye: +/- 0.1 mStandard DSLR Photometry:

+/-0.03mPrecise DSLR Photometry:

+/- 0.01m

Precision Photometry

The right settings for the right signal to noise ratio

(SNR -100)

Precision PhotometryEpsilon Aurigae & 85 mm lens:

Exposure 5 secs,ISO 200, f5Exposure 5 secs, ISO 200, f4.5Exposure 5 secs:ISO 200. f4.

Precision Photometry

Centered target starsThe effect of wind

Remote SwitchCareful FocusLong ExposureDark Frames

Standard DSLR Photometry+/- 0.03m

ten images analysed

200 mm lens - exposure 3.2 secs, f2.8, ISO 800

images every ten/fifteen minutes

85 mm lens, exp 5 secs,

f3.5, ISO 800

200 mm lens - exposure 2.5 secs, f2.8, ISO 800

Variations of 0.2/0.3 magnitude -a new world of variables

Precision DSLR Photometry+/- 0.01m

thirty/ fifty images analysed

Estimates of the 20/2/10JD: 2455248.367

Camera Settings with an 85 mm lens: Exposure-5 seconds, ISO 200, f4.

5 sets of ten images:Analysed with AIP4WIN v2.1.10

(1) 3.776V(2) 3.777V(3) 3.774V(4) 3.769V(5) 3.781V

Average = 3.775V Standard Deviation = 0.004

AIP4WIN - analysis ofRAW images

Dark framesFlat Fields

Multi-image deep sky stacking procedure - 30

minutes to analyse 50 images

V PhotometryGreen Channel Images

Transformation Co-efficient

Estimates of the 10/3/10JD: 2455266.327

Camera Settings with an 85 mm lens: Exposure-5 seconds, ISO 200, f4.

5 sets of ten images:Analysed with AIP4WIN v2.1.10

(1) 3.769V(2) 3.760V(3) 3.776V(4) 3.764V(5) 3.758V

Average = 3.765V Standard Deviation = 0.007

Deciphering Epsilon Aurigae

Presentation of estimates

DSLR Cameras - not as sensitive as CCD cameras

because they are not cooled -but yield just as good results

down to mag 10.5

desloughney@blueyonder.co.uk