ASTROPHOTOGRAPHY WITH MEADE LPI Last updated: 15 February 2007

Subject:	Meade LPI - the plastic case is not light tight.
Sent:	Thursday, February 15, 2007 05:43:42
From:	Lothar METZNER (lotharmetzner@optusnet.com.au)
I enjoyed reading the various stories on the Meade LPI, and thought I
would let you know of my recent discovery.

I purchased an LPI in 2005, with an 8" LX200, and have taken many
reasonable shots, but often thought there was something unpredictable
about the quality of the results; sometime giving poor contrast, lots of
moise, etc.

I could not image the sun recently (with a filter), when spot 930 was
visible. The exposure kept varying, but at the time I did not tweak to
why.

Whilst taking photos of the recent McNaught comet, I again noticed that
the exposure settings were changing 'as I was moving around' the rear of
the LPI. I realised that the LPI's black plastic case is not light
tight.

To test this, I took a dark frame inside the house, with the barrel
blocked off, and then played a torch beam across the back of the case.
The dark frame image on the PC lit up like a christmas tree.  Even if
you hold the case up to a bright light, it will shine through.

I also found that the red L.E.D. power indicator inside the LPI case
made a small difference to one side of the dark frame, as it shines
straight over the top of the back of the CMOS chip.

I have now painted the inside of the case black, and stuck adhesive foil
on the outside, blocking all light, and I relocated the LED to the back
of the case, just on top of the USB connector, plus installed light
baffels inside the case and another on top of the chip.

Shining a 55watt headlight on the outside rear of the case now makes no
difference to the dark frame at all.

I haven't actually used it yet for astro imaging, but I thought you
might want to advise other LPI users of this. Of course, this is not a
problem if you only use it in a very dark location, but I often image
near my house, and always felt it was reasonable to have some lights on
behind the scope...

Oh well, only 30 yars to wait for another bright comet.
 
Regards,
Lothar METZNER.
lotharmetzner@optusnet.com.au
 
P.S.  the comet photo was taken with the LPI mounted on a 70mm Minolta
SLR (35mm film) lens, I had siting around. This is a single frame.

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