Digital Camera Astrophotography

The recent advent of low cost point & shoot digital cameras has heralded a new era in solar system astrophotography. Whereas film cameras excel for extended deep sky imaging, they are particularly vulnerable to atmospheric distortion using the greater magnifications and exposure times required to image the sun, moon, and planets. The digital camera, on the other hand allows you to shoot a great many exposures at a very low cost compared to film thus increasing the chances of an undistorted image. The other main advantage is that you have the image for processing immediately.

The minimum camera requirements would be at least a 2 megapixel image capability along with a self timer, optical zoom and view screen for final shot composition.

Using a digital point & shoot camera must be done using the afocal method… the eyepiece is focused as for visual observing and the camera is held at the eyepiece usually focused at infinity allowing projection of the image onto the CCD. Eyepieces between 35mm and 10mm focal length generally give the best results. Use the view screen to preview the shot. The flash on the camera must be turned off and the self timer used to make the exposure to avoid vibration.

While the camera can be handheld to the eyepiece for low power wide field shots, there are two methods of holding the camera to the eyepiece so that no vibration is transferred to the telescope. If you have a camera that has filter threads on the lens housing then adapters are available from Televue, Scopetronics and others to directly attach the camera to the eyepiece utilizing these threads. Otherwise it is best to use a universal adapter shown below that can attach virtually any camera to the telescope.

Universal Adapter

This method of imaging the solar system requires very good seeing conditions as in any other form of imaging. Most point and shoot cameras have an equivalent ISO of about 200 and can extend exposures to about ½ second. This allows sufficient latitude for imaging the brightest solar system objects as most lunar and planetary film imaging is done on 400 to 800 ISO film at 1/8 to 1 second. The most challenging part is obtaining a sharp focus and preventing any vibration of the setup during the exposure. The autofocus in the digital camera will bring the image into sharp focus and the optical zoom can be employed to further increase the magnification. Due not use the digital zoom as it magnifies a portion of the pixels and tends to degrade the image. The distance of the camera lens from the eyepiece can be adjusted to avoid any vignetting of the image and to allow the eyepiece view to fill as much of the image frame as possible.

Examples:

Images can be taken in RGB color or greyscale and subjected to basic processing in any graphics or photo editing software to enhance contrast and sharpness. The advantage of being able to access images the same night they are taken allows special events such as eclipses, transits, occultations to be recorded and the images can be sent to any agencies that host amateur image uploads, a prime example being the International Marswatch program for this year’s Mars opposition. So if you have a digital camera, team it up with your telescope and see what you can do, I know I am excited by what I have been able to accomplish so far and look forward to much more enjoyable, easy and productive digital imaging through the telescope.

Olympus C740Z

Olympus C-740 Ultra Zoom 3.2 MegaPixel camera.

Having recently obtained an Olympus C-740 digital camera that has full manual shutter aperture and speed control as well as 10X optical zoom I have set out to use this camera for digital planetary imaging. First results have been encouraging on Saturn and Jupiter using the EZE-PIX bracket from Scoptronix and I have just received the eyepiece afocal adapter for close afocal coupling. This coupling device makes afocal imaging much easier. Coupling an eyepiece such as a 25mm to 40mm plossl alone or with a 2X or 3X barlow covers the complete range of planetary diameters.

Scopetronix adapter for Olympus C series.

Scopetronix Digi T system

Planetary afocal setup.

Wide field afocal setup with or without powermate.

Setup for lunar or solar imaging, stills or video.

Technique involves shooting sets of sequential frames using the self timer to allow vibrations to damp out using a mode that allows proper exposure time and speed along with optimal resolution, and then handpicking the best shots in Photoshop and lightly processing with unsharp mask and cropping for stacking and processing in Registax. The method allows for a few frames at best seeing to be recorded and then combined for final processing, much like webcam imaging. With this particular camera, it can be set in HQ mode which is still fairly high resolution and the drive method set at sequential frames (11 per 1.4 seconds) and the optimum speed and exposure set in manual. This is an ongoing learning process as these cameras have multiple features that can be used to advantage by the amateur.

Saturn, iso 400, 1/4 sec. exposure at camera f/4, stack of 4 in Registax, single frame shots.

Jupiter, iso 400, 1/15 sec. exposure at camera f/3.7 macro mode, stack of 12 in Registax, single frame shots.

Clavius, iso 400, 1/25 sec. exposure at camera f/3.7 macro mode, stack of 2 in Registax, single frame shots.

Afocal Astrophotography

Using the camera for movies

Setup for planetary imaging, in video.

Set up the camera in afocal projection mode as for still shooting except that the shooting mode is in 'movie'. I find it useful to use the lcd screen for framing and monitoring shots. Shoot 100 seconds of video which is about 2400 frames and repeat for up to 7 files on a 256 MB flash card.

After downloading to the PC, use a conversion program to convert the Quicktime .mov files to .avi files.

I find that VideoZilla is an excellent conversion utility.

Process the .avi in Registax or K3ccdtools and finish the jpeg in Photoshop and mount in frame.

Finished in PhotoShop with greyscale enhancement.

Further enhancements with Radian projection and RegiStax version 4,

Pentax istDs Digital SLR

The next step...

sun

July 9th, 2005, 150mm refractor Pentax istDs digital camera, Glass type 2 visual solar filter. Eyepiece projection f/20, 1/250 sec. iso 200, RAW format. Seeing 5/5, transparency 4/5. AR786 central, AR783 disappearing around solar limb.