Cameras and Processing

CCD CAMERAS USED

1. Starlight ExPress MX5-C single shot color camera.

2. SBIG ST237 w/ color filter wheel.

3. SBIG ST4 autoguider/imager

4. SBIG ST402me CCD camera

CCD PROCESSING

MX5C Camera- On the MX5 the general procedure is to expose a series of shots at 5 to 10 minutes duration using the 510x290 resolution and StarExpress software  to collect up enough  time to get a well exposed image in color. The images will be later added to produce the final result. Then a series of shots is made using the 510x585 resolution obtained using Astroart sortware. From this a high resolution luminence(monochrome) only extraction is made and co-added to the color images to produce the finished full resolution result.

ST237 Camera-  On the SBIG camera a series of images are made at the 640x480 resolution to obtain data for the final luminence frame. These durations may be anywhere from 20 seconds to 10 minutes depending on the object and other factors such as light pollution level, seeing and telescope tracking . Then a set of color frames with red, green and blue filters is exposed, usually with a duration of 10 minutes each . The color filtered frames are made at the 2x2 binned half resolution. This is done to allow a quick accumulation of light through the filters since the color information does not need to be at high resolution. Dark frames(no light in) are obtained to allow subtracting the camera's electronic noise and flat field frames taken against a white background are obtained to allow subtraction of uneven response of the CCD chip.

ST402 Camera- This newer camera operates much like the ST237 model except it has greatly improved noise and recording capability.

FILM CAMERAS

Various SLR type film cameras are used including:  Olympus OM-1, Pentax K1000, and Nikon Nikkormat. The Om-1 has interchangeable focus screens and a Beattie Intenscreen is used for astro photos, a great help in composing and focusing. The film used for much of the astrophotography was Fuji 400 and 800 speed. The response of these films was good for the astro objects being imaged and were fairly fine grained. Off the shelf fresh film was used with no hypersensitizing. An occasional use of Kodak 200 or 400 was used for lunar or planetary shots. It appears that starting sometime in the year 2000 Fuji modified their print film to reduce redness. The effect on astrophotos was to greatly reduce the recording of red nebulae. Kodak E200 slide film push processed 2 stops to ASA 800 is a good choice today. The general procedure for film astrophotos is to expose 2 or more frames of the object on the same nite one after the other. For piggyback shots using 50mm  lenses at f2 -f4 2 to 16 minutes exposures are made. 100mm to 350 mm telephoto shots are made at f4 to f5.6 and are 15 to 45 minutes in duration. Prime focus shots on the C8 telescope are made using an off axis guider system and are 20 to 45 minutes in duration. These limits allow reasonable image depth on the film and  some relaxation of polar alinement accuracy. The key to all of this is digitizing the film into computer format using an HP scanner and overlaying the images in software such as Picture Window Pro. This allows strengthing the image depth and reducing out some of the grain effects.