Use of Olympus C-2020 Z Digital Camera for Astrophotography

by Greg Konkel, Edmonds, Washington

Introduction:

This web page describes a system I worked out for interfacing my Olympus C-2020 Zoom digital camera to my Celestron CG-9.25 Schmidt-Cassegrain telescope for obtaining images of bright astronomical objects, such as the moon and planets.  As you can see from the images obtained during my first few sessions with this system, the results are very promising and open up many possibilities for digital astrophotography without resorting to expensive astronomical CCD cameras.

(Note: This web page describing my equipment and techniques, which previously received about 1,000 visits as a stand-alone page, is now a sub-page under my personal web site.  I've accumulated more than 50 decent lunar images and have set up a separate Astro Images page.  Only a few example images will remain on this page to demonstrate the capabilities of this camera/telescope configuration.   I plan to acquire many more images over the next several months and post the best ones on my Astro Images page.  I eventually hope to have a fairly complete coverage of the moon in both waxing and waning phases at a consistent scale and resolution.  I'm also hoping for some good results using this setup to obtain images of Jupiter, Saturn, Venus, and Mars.)

Equipment:

The Celestron CG-9.25 telescope with German equatorial mount that I own is pictured at left.  I've made a number of modifications to it, including the addition of a larger 9x50 finder scope, a Telrad, and an Astro Pier installed in my backyard.  I also worked out a way to reinforce the flimsy tripod that it comes with, which I'll address on another web page.

At right is the Olympus C-2020 Zoom 2.1 megapixel digital camera that I purchased a about a year ago.  This model is no longer available, but similar models, including the C-3000, C-3030, and C-2040, can be purchased for $700 or less through mail order or the Internet.   This versatile camera has native file formats that include both JPEG and TIFF ranging from 640x480 to 1600x1200 pixel resolution with 24-bit color depth.  The camera has an optical zoom lens equivalent to a range of 35-105mm on a 35mm camera film camera.  In addition, it has a 2.5X digital zoom.  Other features include true manual focus; macro mode; white balance; black and white grayscale and sepia modes; shutter-preferred, aperture preferred, and fully manual exposure ranging up to 16 seconds; a 1.8-inch LCD for a "through-the-lens" view; video out with slide show mode; a wireless remote control; and an on-screen menu system.  Two other interesting features, which I've yet to use, are panorama mode and QuickTime movie shooting mode, capturing 15fps (at 320 x 240 pixels) or 60fps (at 160 x 120 pixels) video clips.  The camera uses a SmartMedia card that comes in different storage capacities from 8MB to 64MB.

The interface I worked out for attaching this camera to the telescope includes the following components: a 41-49mm (filter thread) step-up ring, a 49mm to T-mount adapter, and a variable power tele-extender (pictured below).  The Olympus digicam has a 41mm filter thread around the lens opening and the tele-extender threads directly onto a standard SCT visual back (at right).  Also pictured is a Celestron 26mm Plössl eyepiece, which works ideally with this interface, providing a wide range of magnification in conjunction with the camera's zoom lens.   When the camera is zoomed in fully, the image nearly fills the camera's frame with only a slight vignetting in the corners.  Eyepiece projection is the only way to use this camera for astrophotography since it has a non-removable lens.   Another component that can be used (not pictured here) is an f/6.3 focal reducer/field flattener, which goes in front of the visual back.  This has the effect of increasing brightness, reducing exposure time by a factor of 3, and widening the field of view.

Here's a list of the three interface components, including source, part number, and price:

These prices do not include applicable sales tax or shipping and handling.  Potential sources for the Olympus digicam include Camera World of Oregon, Focus Camera & Video, and BUY.COM.  Pictured below is what these components, including eyepiece and visual back,  look like when they're assembled.

One very important consideration in making this arrangement work is the eyepiece to camera lens distance, which must be within a few millimeters and must be adjusted very precisely to find the optimum distance for each eyepiece and correct problems with vignetting and blackout.  I found that, when I first obtained the variable tele-extender, it was too long at its shortest setting for any but the longest eyepieces.  I was able to modify it without too much trouble to work ideally for this application by cutting 1.125 inches off the unthreaded end of the inside sleeve (see photo below).  I did this by using a miter box and a fine-toothed saw, since it's made of anodized aluminum and is fairly easy to cut.  After cutting, I laid a piece of medium-fine 3M wet or dry sandpaper face up on a flat surface and dragged the cut end of the sleeve back and forth until is was smooth.  Then I beveled the edges slightly with a file and painted it with some flat black spray paint I had in the garage.  In addition to shortening the length range of the tele-extender, cutting off part of the inside sleeve resulted in the two set screws no longer sliding within the slots.  This is actually an advantage since you can easily rotate the outer sleeve of the modified tele-extender and align the camera field in relation to the astronomical object being photographed, e.g., making sure that south is straight up when photographing the moon.

Pictured below is the camera with the step-up ring and Xtend-a-Scope adapter attached and the power turned on so that the lens is fully extended.  As you can see, the lens extends about one quarter inch beyond the adapter.  The photo at right shows the 26mm Plössl inside the visual back and variable tele-extender.  By comparing these two photos you can see that the lens-eyepiece distance is very close when the T-mount is threaded on.

Pros and Cons:

Using a digital camera like the Olympus C-2020 Zoom has some real advantages for astrophotography.  You can use the LCD screen to center the object in the field of view, to pan and zoom using the telescope drive and the power zoom on the camera, and to check for approximate focus.  The wireless remote and the electronic shutter mean vibration is virtually eliminated when recording images.  The on-screen menu is visible in the dark, enabling you to change camera settings easily.  Probably the biggest advantage is that you get nearly instant feedback in seeing the results of your work.  If you have a laptop computer, you can transfer images directly to the computer on-site, or (as I do) run back and forth with the SmartMedia card to the desktop computer in the house.  If focus is slightly off or exposure is not quite right, just try again.  Another way to use a laptop is to run the video out from the camera directly into the computer's video-in port.  The computer screen then becomes a live monitor for the CCD image, which should help with framing and focusing shots.   In lieu of a laptop computer, you can also use an external video monitor.  Another big advantage is the generous pixel resolution of the newer digicams.  I find that 1600x1200 is more than adequate and actually allows me some editing room to eliminate vignetting or more carefully compose the final image.  I usually record at the full resolution and then clip out 1024x768 portions of the raw image using Corel Photo-Paint.   These relatively large images take on a spaciousness that makes them quite impressive as compared to others produced with astronomical CCD cameras, which—except for the most expensive—have a smaller image size.

There are a couple of disadvantages of this setup over an astronomical CCD camera.   Even though exposures of up to 16 seconds are possible, this is far too short a time for most deep sky objects.  Also, the CCD chip in this camera is not designed for long exposures and begins accumulating noise after about one second.  However, this setup is well-suited for solar, lunar, and planetary photography.  Another small problem is that the batteries run out fairly quickly if the LCD screen is used for an extended period of time.  However, there's plenty of life in fully charged NiCad batteries to complete one lunar photography session and an A/C adapter is available for the camera.  Another consideration, which may or may not be a disadvantage, is whether the camera's autofocus actually works with this setup.  It seems to at times, but I'm not completely convinced that it does all the time.  I'm unable to use a knife-edge focuser with this setup, as I do with my Olympus OM-1 film camera, so I need to rely on the LCD, the telescope's focus knob, and the camera's focusing capabilities to achieve focus.  I've been refining my photographic techniques, including camera settings, exposure, and focus, and I plan to include more if this information here in the future.  Another problem noted in my initial use of this setup is the chromatic aberration that's visible around the limb of the moon and near the terminator.   This is either an artifact of the camera electronics or the optical configuration... I'm not sure which.  After the first month or so of experimentation, I made the decision to take all lunar images using the camera's intrinsic black and white mode.  Another problem with this setup is that the variable tele-extender is too narrow inside for many eyepieces and, even with the modification, is too long for Plössl eyepieces shorter than about 17mm.  One final note of caution: it's very easy to have a collision between the camera lens and the eyepiece when the set screws on the variable tele-extender are loose.  You should become intimately familiar with the range of movement within the optimum camera lens-eyepiece distance for each eyepiece that you use.  This will enable you to make adjustments, such as rotating the camera or eliminating blackout, in the dark without fear of damaging the coatings on the camera lens or eyepiece.  I accept no responsibility for damage to either camera or eyepiece resulting from the use this setup.

Configuration Options:

The 17mm, 20mm, and 26mm Celestron Plössl eyepieces work well with this setup and, when used with or without the f6.3 reducer/corrector and in conjunction with the camera's power zoom, offer a fairly wide range of options for magnification and field width.  I'm talking about the black Plössls with red writing that have been around for years.  The new NexStar Plössls are thicker and won't work with this setup.   To make the 17mm eyepiece work, I had to tape an extension onto the barrel that inserts into the visual back using a barrel borrowed from another eyepiece.   To get the 20mm to work, I don't insert it all the way into the visual back...  I let it stick out as far as possible and still tighten the set screw.   The Celestron Plössl eyepieces longer than 26mm are too thick to fit inside the tele-extender, however, the old Silvertop Plössls do fit.  I've tested it with the 36mm and 45mm Silvertops and both work fine.  The problem with the Silvertop eyepieces is that they're as rare as hen's teeth.  Other, longer-focal-length eyepieces that work include the 32mm Meade Series 4000 Super Plössl and the 40mm Meade MA.  I just purchased the latter, but haven't had a chance to test it yet.

The Results:

Here are some examples of what you can do with this digital camera/telescope setup.   The thumbnails below enlarge to 1024x768 images, unless otherwise indicated.   Most of these images were taken during the April and May 2000 lunar cycles.  A brief description is given for each image, including a few of the more prominent lunar features.  The 26mm eyepiece and f/6.3 reducer/corrector were used unless otherwise stated.  Most of the images have been converted to monochrome to eliminate chromatic aberration.

All images Copyright © 2000 by Greg Konkel.   All rights reserved.

Links:

Arpad Kovacsy shows some nice lunar and other astrophotos taken with his Nikon Coolpix 950 digital camera through the eyepiece of his Celestron CR150HD achromatic refractor.

Peter Wolf describes a less-expensive solution to interfacing the Olympus C-2020 Z with a telescope using PVC tubing.  Without a variable tele-extender, it lacks the ability to accommodate different eyepieces and precisely adjust camera-eyepiece distance, but, measured carefully for a specific eyepiece, it should work just fine.

Wesley Chuen provides a step-by-step method for attaching the Nikon Coolpix digicam to a telescope.

Other relevant links are located on my Links page.

Comments Please:

Let me know if this information is helpful to you and if you have anything more to add.   I would appreciate hearing from fellow amateur astronomers who have experience using digital cameras for astrophotography.  I'm still in the experimental stage myself and I'm looking forward to trying this setup on Jupiter and Saturn later this summer.

Your questions and comments are welcome gkonkel@nwgis.com

This page was last updated on February 24, 2004.