DayStar Filters CALCIUM QUARK Manuel - Sayfa 10

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Exposure time:

Imaging solar vs. nighttime astrophotography is very different. Dark sky

imaging requires long exposure times to capture enough light. Solar

imaging offers ample light, so exposures should be very short.

fluctuations in seeing dictate that short <1/10 second frame rates will be

better, as seeing cells move quickly to distort the image and can come

and go during a long exposure.

•

Short exposure webcam imagers are better than long exposure

CCD cameras when imaging the sun.

•

Because the sun has a range of brightnesses, automatic

exposure doesn't work well. A software interface that allows the

user to control the exposure settings manually is very important.

Exposures for prominences taken through a DayStar with a webcam

style camera might be about 1/15 – 1/100

surface detail would be even shorter exposure with about 1/300 to

1/500

of a second.

Bit depth:

Solar activity encompasses a wide dynamic brightness range from bright

solar flares to faint eruptive or floating prominences quite a distance from

the solar limb. In order to capture all these features, we recommend the

use of 12 bit or 16 bit cameras. Normal 8 bit cameras can be used, but

will typically only be able to image either the surface or prominences,

necessitating

recombination in a computer. 12 bit or 16 bit cameras enable capturing

these features in the same exposure, simplifying the image processing.

Focal reducers:

Because of the long effective focal length at the output of the Quark, the

image scale will be quite large and small (1/2" or below) image sensors

will only capture a fraction of the whole solar disk in one frame. Large

pixel sizes (9 microns and above) will enable a larger field of view.

Alternatively, a focal reducer can be employed

between the Quark and the camera. Simple 1.25"

screw in focal reducers can be attached to the

camera nosepiece to allow a wider field of view with

small (1/2", 1/3", ¼") sensor cameras.

distance between the focal reducer and camera

surface will result in more focal reduction and larger field of view.

multiple

bracketed

of a second. Exposures for

exposures

and

Plus,

subsequent