ASTROPHOTO CAMERA PADDLE SHUTTER Last updated: 30 November 2008

Sent:	Saturday, November 29, 2008 10:58:58
From:	Nohr Tillman (ntillm01@yahoo.com)
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, MI

And:

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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