ETX-80 FLEXIFOCUS Last updated: 22 August 2007

Subject:	Adding a Flexi Focus to the ETX 80 article
Sent:	Wednesday, August 22, 2007 10:19:36
From:	Alexander W. Hobson (alexander.hobson@chumamfm.com)
I am having a ball with my Meade ETX80AT and thought I'd send you a fast
article  about what I have found in the way of accessories which really
work with the ETX 80 and what I made to help focus. It might help if you
posted it to your site.  I am on your site almost every day looking for
tips. I think this will be of great help to your web viewers as I have
had to search all over for this info and purchased some of the stuff not
knowing if it would actually work.

My travel scope is the Meade ETX 80 AT and I am almost finished
outfitting it.  I found there were several things I wanted in the scope
which were not included or not available and there was some confusion
about some accessories on the internet.

First, I wanted a more stable power supply, so purchased the Meade 546
AC Adapter which is definitely the correct power supply for the Meade
ETX 80.

Next I wanted a viewfinder scope as I wanted to be able to use the scope
in manual mode so I purchased the  Meade #827 -  8 X 25MM RA Viewfinder
model which fits perfectly and is also the correct viewfinder for the
ETX 80.

Now I needed to think about dew protection and since there is not a dew
shield for this scope at Meade, I settled on a Kendrick dew shield which
was custom made and Velcros' together.  I am lucky to live near Kendrick
in Toronto and they do mail order.  It was made while I stood in the
store waiting for 10 minutes one day, it works great and the customer
service is outstanding!  There are several places in the US which make
this type of shield as well.

Next I purchased a Smart-Astronomy Smart Case hand control cover with
dew heater which will keep the Autostar controller from getting muck on
it, especially snow in the winter!

Finally, and this may be of most interest, I found that focusing the
unit, especially when switching between eyepieces, was a bit of a
problem.  So many revolutions of the focus dial were needed, that the
scope would move a lot, so focus and keeping the scope pointed was a
real pain.  I wanted to focus the unit without moving the scope wildly
about so I looked into the Flexi-Focus and found that there wasn't one
made for the ETX 80.  After taking the small screw out of the back of
the plastic cover of the ETX 80 beside the focus mechanism, I discovered
that the focus knob was not removable.  It is all one piece, pressed in
place onto the shaft of the focus mechanism.  So I had to make an
adapter if I wanted to use a flexi focus.  Since I couldn't find one
available on the net, I decided to design and make one.  I purchased a
flexi focus made for the ETX 90 and by adding an adapter, which I show
in the photos, am able to focus in a flash while viewing by eye or
imaging with my LPI!   No more jiggling or shifting, or at least
minimal.

Here's how I made the adapter. Actually, before I start, if you are
going to try this, safety is your #1 concern.  Make sure you use safety
glasses and lung protection doing this project.  If you don't think you
can work safely, don't attempt this, have someone make it for you who
has experience.  I assume no responsibility for injuries you incur or
inflict while trying this project.  OK now on to the fun!  Metal work is
intrinsically dangerous, so be careful and go slowly.  First I made a
fast pencil drawing to get the sizes and to see if it would fit around
all the edges of the scope leaving room to turn the focus knob.  See the
diagram I sent.  I looked at the size of the flexi focus end and
determined that it needed a piece of metal about 3/16" round X 3/16"
high to screw onto.  I also measured the focus knob of the scope and
noticed it to be about " in diameter.  So I would need to make an
adapter to slip over the focus knob and have a small nipple on the top
to attach the flexi focus to.

I looked up "Metal" in the yellow pages and found a local store which
sold metal cut to any size and length.  This adapter was cut from a
small piece of " solid round aluminum rod which I purchased.  I chose
aluminum because it is corrosion resistant, is light, easy to work with
and looks like the rest of the gear on the EXT 80.  I have access to a
small lathe, drill press, tap set and other tools needed, but this could
be made just as easily with a file, hacksaw, hand drill and some
patience.  The size of the adapter will be about " X ".  First, I cut
off a small piece of the " stock rod with a hack saw and chucked the bar
in the lathe.  I trued the rod and milled out two small ends 3/16" wide,
by over 3/16" long, (I needed a little space to cut the adapter off the
rest of the bar later), along the shaft.  I made sure there was at least
9/16" in between these ends so that I could make the body of the adapter
from these pieces.  I made two at a time in case I screwed something up
on one of them.  I cut the adapter so it was 9/16" long with the 3/16"
nipple sticking out.  I put the nipple into a small vice and centre
punched the opposite end.  I then drilled, with a small 1/8" bit, in the
centre and down to where I would leave approximately 1/8" or so of metal
on the top by the nipple, effectively making a little hat which would
fit over the focus knob of the telescope, with the nipple sticking out
to attach to the flexi focus.  I continued drilling with consecutively
larger bits, until I reach a " bit.  Then I removed the adapter from the
vice checked for fit, re-drilled by jiggling the bit around and checked
until it fit perfectly.  Then I re-positioned it on it's side and
drilled a small hole about  way down the tube which was then tapped to
accept a 6/32 set screw which I purchased at Home Depot.  This would
hold the adapter onto the telescope focus knob.  In the picture, there
is a separate adapter to show what it looks like by itself and another
adapter is already screwed to the flexi focus.  All that is left to do
is to sand the adapter and slip the adapter over the focus knob of the
scope and tighten the set screw and there you go, one ETX 80 with flexi
focus.

I went on to make an adapter entirely by hand with only the hand tools I
mentioned to be sure anyone with a minimum of tools and or experience
could do this.  First I hack sawed a piece of rod to ".  Then I used a
file to file the saw marks out of the top and bottom.  Next I marked out
the 3/16" nipple on the top and sides of the piece with a sharp pencil
and put the piece in a small vice. You could use a clamp or just
something to hold it down while you cut down around the top part of the
nipple, down to a fraction above the 3/16" mark on the side.  Turn the
piece over and cut around the rod until you meet up with the small cuts
around the top.  Use a file to clean up the top and make the nipple more
round in shape.  Use the flexi focus end as a guide to make sure you
don't take too much off.  Once you are satisfied with the end and it
fits the flexi focus, mark the centre of the other end of the adapter
and use a nail or punch to leave a mark in the aluminum so the drill
does not slip.  Use a small drill bit, about 1/8" or so to drill a pilot
hole to the depth you want.  Take your time to make it straight.  To
keep the depth correct, a good trick is to hold the bit against the
outside of the adapter and mark the depth you want with a piece of
masking tape wrapped around the bit to the depth required.  After
drilling the hole down to the masking tape, use larger bits until you
reach a 1/2 "sized hole.  Go slow! The top of the focus knob is actually
slightly larger than this so you will need to wiggle the bit a bit to
enlarge it slightly until it fits.  Keep trying the adapter on the focus
knob until it fits perfectly, then make the small hole in the side of
the adapter for the set screw and away you go.  I drilled the hole just
a bit smaller than the set screw and pushed the set screw while turning
it into the hole, effectively tapping the hole as it went. Because set
screws are a bit tapered, this worked fairly well and the set screw
held.

Aluminum is easy to work with because it is a fairly soft metal and can
be sanded like wood to a smooth finish.  Make sure you use a mask so you
don't get any aluminum particles in your lungs! And while I'm speaking
about safety, make sure you use safety glasses and be careful cutting. 
I take my projects down to about 600 grit wet/dry sandpaper for a smooth
satin like finish.  Make sure to sand the edges so they are not sharp
and countersink the holes you make a tiny bit so the adapter is smooth
and will not catch on anything.  I slipped the adapter into the end of a
small hand drill and spun it slowly while holding the sandpaper against
it.  Works like a charm.  Start with about 220 paper and work your way
down to the finish you like.  It's a great and easy project for someone
with a little metal working experience which should only take a few
hours to complete, but will really help with the focus.

I was going to put on an electric focuser as I could have made an
adapter to fit over the focus knob and accept one of the commercial
units, but after seeing many people recommending the flexi focus, I
decided to try the flexi focus first and wow does it work well!  If I
find I want to use an electric focuser later, I'll make up an adapter
for that and let you know how I made it.  Hope this article helps and
work safely.  I can't assume any responsibly for any injuries caused by
trying this project or damage to your telescope. The set screw will
leave a mark on the focus knob.  I don't plan to ever take mine off so
if you plan to remove it, you may want to take steps to make the main
hole larger, and use something like a small piece of plastic or nylon on
the focus shaft to protect it from damage.  Just be really careful!.

Any questions, I am on the net at hobsonaw@aol.com

Thanks again Mike for helping us all!
 
Alexander W. Hobson

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