Specifications

● Focus image properly. Almost unnoticeable focuser shift affects

star diameter. Focusing, especially on fast telescopes, is critical for

sharp images. Electrical focuser is a huge advantage, because it

allows focusing without shaking the telescope by hand and with

precision surpassing the manual focusing.

Keep on mind that the star images are affected not only by

focusing, but also by seeing. Star images will be considerably

bigger in the night of poor seeing, no matter how carefully you

focus.

● Master image calibration (dark frame subtraction and flat fielding)

and carefully calibrate all images. Various artifacts (thermal noise,

hot pixels, gradients, telescope/lens vignettation, dust particles on

filters etc.) degrade the image and properly calibrated image

always looks better. Take care to obtain dark frames and flat fields

for all filters used, for all resolutions/binnings etc.

● If the image is processed to be as aesthetic as possible, other

processing than basic calibration can significantly improve its

appearance. Nonlinear stretching (called “curves” in some image-

editing packages), special filters (hot/cold pixels removal, noise

reduction etc.) and other processing (e.g. deconvolution) enhances

the image.

Warning:

Never perform these enhancing filters on images intended for data

reduction processing. It is always good idea to store original image

and to enhance only its copy. Scientific information can be

significantly degraded by various noise filters, deconvolution etc.

If for instance the image of some galaxy contains newly

discovered supernova, photometric reduction of the original image

can be scientifically very important.

● A common saying “there is a science in every astronomical

picture” is especially true for CCD images. Examine your images

carefully, blink them with older images of the same object or field.

There is always a chance some new variable star, new asteroid,

new nova or supernova appear in the image.

● Be patient. Although many advertisements proclaim “capture

images like these your first night out”, they probably mean your