Last updated: 30 November 2008
Sent: Saturday, November 29, 2008 10:58:58 From: Nohr Tillman (firstname.lastname@example.org) This might be worth posting in your Helpful Information - Astrophotography gallery. It's a slight refinement of the "hat trick" for avoiding shutter-shake when photographing through a telescope. I made this one big enough for an ETX-125, but the concept could be applied to any telephoto lens. I made it from a sheet of construction foam from the local craft store. I cut the shapes using the lens cap as a guide. It's bolted together with a nylon license plate bolt and nut with the black nylon washers from an automotive battery hold-down kit. Shutter in the folded up position for transport. Paddles are open, ready for some old-fashioned SLR photography. In Position One. At this point, the camera shutter is opened (set to B or Bulb to hold the shutter open) with a cable release. Then wait a few seconds to let all the vibrations settle out. The wrist has rotated the paddle-shutter to Position Two. At this point, the camera cable is released and the exposure is done. I made this thing to use rather than the hat trick for a couple of reasons. First, I typically don't wear hats, unless it's cold out and it's a woven cap, and then I wouldn't want to take it off to use as a shutter. Second, with both paddles moving in the same direction uncovering then re-covering the lens, the film "sees" the image appear and disappear in the same motion, similar to the real shutter inside the camera. It think works better than hat-down, hat-up because the film is exposed evenly. For long exposures, this would matter less but for short moon exposures I think it makes a difference. Lastly, I think the exposure time can be better adjusted by changing the angle between the paddles. My experience with a Pentax MX SLR 64-T-mounted to an ETX-125 shows that the Moon likes an exposure of 1/125 to 1/250 second. The moon phase does not seem to matter, nor does ASA200 or ASA 800. However, the high power of the ETX makes camera shake very pronounced even at those fast speeds. This paddle-thing seems like it should get me out of shutter shake, and near-fast shutter speeds. I'll send some empirical results if I get the chance in the next month (grey, socked-in winter is upon us here) Nohr Tillman Troy, MIMike here: I use a 8" diameter piece of stiff black cardboard. But this "shutter" looks really good.
Thanks for the compliment! I was on a quest to find black cardboard, and ran across this foam stuff instead. Folded up, it fits in the ETX-Backpack nicely. Sorry to fill your inbox, but thought you and others might benefit from some experimenting I've been doing. In-series, I am sending three pictures with my analysis. I'll try to keep it brief. All three pictures taken with ETX-125 set to lunar tracking, polar aligned (and doing beautifully I might add). Very clear inbetween rounds of clouds, Moon about 50 deg Alt. Film is Kodak Max 800, developed and scanned at local department store. Cable release was used, but it is an old mechanical camera with mirror and shutter shake. ETX-125 - 64-T short tube - Pentax MX - 1/250 sec - ASA800 Film Craters are sharp, but picture is slightly underexposed and the sky not so black. ETX-125 - 64-T short tube - Pentax MX - 1/125 sec - ASA800 Film Sky is dark and black, craters not as sharp as at 1/250 second. Surface color is good. Starting to pick up camera shake. ETX-125 - 64-T short tube - Pentax MX - 1/60 sec - ASA800 Film Color and exposure good for the moon surface and dark night sky. Losing even more sharpness of the craters because of camera/high power optics shake. After each shot, could see a second or two worth of visible vibration in the viewfinder. It damped out very quickly, but the vibration had already started by the time the film shutter opened. While the Pentax MX is very compact and light (and pairs nicely with ETX-125 and ETX-90) it is mechanical and does not feature a true mirror-lock up that would help with this problem. Perhaps something to add to the Pentax Camera section? Another thing to note about the Pentax MX: I have achieved perfect focus with the ETX-90 and ETX-125 using all three T-adapters from Meade: 64-T short tube and long tube combination and the 64-ST which puts it right at the back of the scope. The longer the tube used, the larger the image. At least with the Moon, I have not noticed any viginetting. Could be I'm just not noticing it. Next batch will be of the Jupiter/Venus/Moon collection using my paddle-shutter trick. Thanks again for your time and the great site! Nohr Tillman Troy, MI
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