Last updated: 25 March 2002
Subject: Hybrid Astrophotography Sent: Saturday, March 23, 2002 15:34:10 From: firstname.lastname@example.org (Vance Green) First, Mike, I just gotta be the 1,000,001th person to compliment you on your great site.Whatta lifesaver! My wife got me a ETX-60 for Xmas (the COSTCO $128.00 deal). As a kid, I spent hours up on the roof of my parents' house with a cheap imported 2.4" alt/az refractor laboriously tracking down objects with star charts and a lotta luck.the ETX found in a half-hour via GO-TO's what it took a ten-year-old many tens of nights the "old-fashioned" way, and tracked them too! Pretty amazing what $130 can buy-and the image quality is there as well. As a techie from way back (1st computer was an Ohio Scientific C1P back in ' 78 - anyone remember those?), I quickly became intrigued with the digital astrophotography aspects of this scope-I already have a Nikon 990-and bought the Digitronix Digi-T adapter after several handheld "experiments" of holding the 990 up to the eyepiece. Took some pretty good shots via the use-the-self-timer-as-a shutter-release method, but being somewhat annoyed by the need to make several button pushes on the 990 each time I took a shot (no fun when it's cold out), I started searching for a better way. I knew about the various remote control programs for the 990 such as PhotoPC (http://www.math.ualberta.ca/imaging/ ), and being no stranger to the command-line, set about experimenting with it. (Prof. Bowman, the owner of the site, went way beyond the call of duty when a particular version of PhotoPC would not talk via USB to my camera-he knows his stuff). More info available at: http://www.charliex.net/cpix/cpix.htm as well. The GUI's available for PhotoPC offer WAY too many options necessary to use the 990 for astrophotography and just get in the way, so I wrote a little VisualBasic 3.0 app that shells out to PhotoPC with a command entered in a text box-not very elegant, but it gets the job done. (VB users-read up on the SHELL command on how to do this) Now, I was able to take shots with the 990 WITHOUT needing to fiddle with the camera between each. The next phase of the overall project dealt with focusing-the LCD on the back of the 990 is just TOO small to allow for fine focusing of planets, although it's fine for larger objects like the Moon, where there's enough detail to see the results. There was always a small difference in the 'scope focus between finding the object in the eyepiece and attaching the same eyepiece to the 990 (set for infinity) and fitting it to the ETX, making most planetary shots nothing more than fuzzy discs. Technology to the rescue, again. An often overlooked fact of most digicams is that they continuously output video through the VIDEO OUT port whenever they're turned on. This signal should be able to be used to focus with if displayed on a TV. My initial try at this was with an el-cheapo Taiwanese B/W portable TV I had laying around.this worked, but added more bulky electronic stuff to the (already) pretty cluttered setup. Next try was with one of the TV to USB converters available-I reasoned that with a USB HUB, I should be able to keep a real-time video window of the camera preview open on the laptop as well as operate the E990 remotely. They 're cheap-under $100-and would be worth it if this worked.besides the "real" uses of the thing (watching TV on the laptop when you're supposed to be working!). This setup works EXTREMELY well. I settled on the ATI TV-WONDER (USB edition-$84.95 on the 'Net) after trying the AverMedia unit and giving up on it (unstable operation under W2K). The ATI will preview input video at 640 x 480 on my laptop-allowing for MUCH better focusing of the ETX with the Nikon attached before taking a shot. And the whole mess is more or less "integrated" on the laptop screen-I suppose if I wanted to I could even run the remote 'scope control software there as well-but I have to buy the overpriced 506 cable first ;) Attached is an image of the cabling setup, and a screenshot of the whole works while operating. The target in the preview window is my neighbor's HAM antenna as seen by the ETX. Also a few "quick and dirty" images of Jupiter and Saturn (no post-processing except crop/resample to smaller size) from the 990.
Photo PC has the ability to remotely download the shot you just took, so you can see what you're doing wrong in just a few seconds on the laptop screen (I use PaintShopPro for image viewing/manipulating), rather than try to figure out what to do on the teeny-tiny 990 LCD. Another bonus-you can capture the video from the camera with the ATI (albeit in a smaller resolution) and/or take 640 x 480 single-frame captures, but the image quality of the 990 is far superior to these. Watching the video can be enlightening, though, and also works well for terrestrial observations. Some gotchas with this setup: You can't set the camera ISO remotely. If you want to set the camera for the highest ISO (more light sensitivity), you have to do it in Manual mode, then plug the camera's USB cable into the hub. The ISO setting will "stick" while you use the other remote functions. You can't go digital zoom over 2.5X remotely. If you want to set digital zoom higher, do it on the camera and then plug in the USB cable, whatever it was set to will "stick". You can't use a cheap "unpowered" USB hub. The ATI wants 450mA off the USB interface to run and unpowered hubs can't do this. I'm using a Belkin F5U101 personally. You can't go over 8 sec. exposure duration using PhotoPC. Longer seems to only be doable with the Nikon remote shutter release, the "B" setting and your finger, or the self-timer (and only on the 995-or so I hear). Occasional strange camera lockups WILL occur during remote operation. This is discussed on the PhotoPC site and seems to be due to lack on information from Nikon on the camera communication protocol. Just unplug the USB cable to regain control-there seems to be no permanent camera damage. USB control of the 995 is apparently still being worked on according to the PhotoPC site. Serial control is the only option right now (requires expensive or homemade cable). READ and UNDERSTAND the information on the PhotoPC site- specific issues related to device driver problems are discussed there. Pay special attention to the instructions on what order you turn on power, then plug in the USB cable. Get everything else up and going, turn on your digicam, wait until the display is settled and normal, and THEN (and only then) plug the USB cable in. The object you're trying to image is never in the field of view AFTER you remove the eyepiece you used to find it, screw it to the camera, and remount it-this is due to the added weight of the camera. I've been toying with the idea of a counterweight for this problem, but am open to other suggestions.finding the object again can be very time consuming (and frustrating). While the above setup SHOULD work with other cameras, I'm a Nikon type of guy, and can't speak to that. PhotoPC apparently will work with a number of digicams based on a specific chipset-see the site for details. And, as always, remote operation of any digicam is probably "outside" manufacturer's specs and may void your warranty- YMMV. It helps to create a "astrophotography" user profile on the controlling laptop that uses a black desktop background with as few icons or other bright stuff on it so as to not kill off your night vision. Hope others have as much fun with this rig as I have-it's a gadget lover's dream! Vance Green Tempe, Arizona
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