Re: Balancing the declination axis

Joe Zeglinski


An after thought.

Rather than drilling the two rearward holes for the back ring, right away,
can you get one or two Vice Grips or C-Clamps to fix the rear OTA ring to the
plate temporarily, and see if it helps the balancing act. That way you aren't
committed to more holes and making Swiss cheese out of the plate. The front
ring will still provide solid support as you test the "optimum position" of
the temporarily sliding rear OTA ring position.

Too bad you can't find a nice clearing "between the ribs" of the plate,
for all the screws, of an alternate displaced DEC axle hole pattern.

Best of luck,


----- Original Message -----
From: "Gavin Bray" <gavbray@...>
To: <ap-gto@...>
Sent: Tuesday, July 03, 2007 6:06 PM
Subject: [ap-gto] Re: Balancing the declination axis


Actually you're right - I misread what you said. Sorry about that
and thanks for persisting.

What I will do is drill some more holes for the back ring as close
to the plate's attachments holes as possible. This will allow me to
overhang the front of the OTA and hopefully go a long way to solving
the balancing issue. I'll do this this weekend and will let the
group know.

I'm afraid your second suggestion about drilling new plate
attachment holes isn't feasible due to the plate's ribbing.

Also, someone suggested using the AP 15" ribbed mounting plate
rather than the 24" as the 15"'s attachment holes are apparently off
center. I'll look into this too.

What would be really nice is if AP made a 24" plate that's off
center. :-}


--- In ap-gto@..., "Joseph Zeglinski" <J.Zeglinski@...>

Hi Gavin,

I'm not sure if you got what I meant by "moving the OTA rings
The idea is that by reducing the spacing "between" the rings, you
might be
able to slide the OTA more forward (since the back end ring is
then closer to
the front one). That could give you a few more inches of leverage,
as the OTA
now overhangs the front of the plate more.

The other approach - can you drill plate attachment holes in
it, "shifted
off centre of the plate", closer to the rear of the plate? In
essence, you are
now moving the entire OTA and rings forward as well.
This was AP's approach in their recent DOVELM2 dovetail attachment
to the
AP900 DEC axle head. Actually, they shifted their pattern "forward
of centre",
since they wanted to accommodate refractors with heavy lenses, so
the entire
dovetail block ended up being shifted downward. You want the
reverse of this,
I believe.

Actually, I found it necessary to drill my own DOVELM2 pattern
as a mirror
of the AP pattern position, since my Questar-7 balance and
procedure required it. If it had been a Losmandy G11 saddle, I
would not have
to do that, but the AP saddle is grooved on just one side, so
rotating my
DOVELM2 to shift the hole pattern in the opposite direction, would
not have
worked properly.

Perhaps a combination of (1) and (2) above might be necessary, if
imbalance is really bad - hopefully not.


----- Original Message -----
From: "Gavin Bray" <gavbray@...>
To: <ap-gto@...>
Sent: Tuesday, July 03, 2007 3:24 AM
Subject: [ap-gto] Re: Balancing the declination axis

Hi Joe

Yes, I've drilled new holes and have the rings and tube as far
forward as possible without the tube overhanging the mounting
too much.

I think I need something where the backend of the tube is a lot
closer to the dec axis.


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