----- Original Message -----
Sent: Sunday, November 04, 2001 5:21 PM
Subject: Re: [M]: Remote focusing via JMI?


> Roger,
>
> What is interesting is that Technical Innovations claims that with a
Robo-Focus
> on the main focus knob that net image shift was only 10 arc-sec!
Doesn't sound
> like you've seen this reduction in image shift. I would really like to
> eliminate the need for the NGF exactly for the reason you've mentioned
along
> with others.
Important to understand that there are different types of image shift.
RoboFocus allmost totally eliminates the image shift associated with
focussing - watching on a focus window, you see the star move sideways as
the focusser operates, then return to allmost exactly it's starting
point - better than 10 arc seconds, I see only perhaps one or two pixels,
running scaled at about 1.6 arc seconds/pixel. However it has no effect on
the other type of shift, which is where the main mirror 'rocks' as you
pass the meridian. This is avoidable by being careful where you are
imaging, but cannot be removed on a simple 'tube over tube' main mirror
mount. With the NGF-S, you can remove this too, by using a locking bolt in
the shipping hole, and applying some torque to the mount, which reduces
this shift to practically zero.
I like the RoboFocus. If is remarkably accurate (when you consider how
small the main mirror movements are for focussing), and seems very
repeatable.
One 'caveat' I have about it, is that I have a variety of devices using
these power connectors, and some are US/English designs (tip +ve), while
others are Japanese units (tip -ve). Of all the units, the RoboFocus, is
the _only_ one I have that does not have a protection diode if you
accidentally reverse the power connection. I have modified the unit, and
added a 3A Schottky barrier diode (low voltage drop), in the wire between
the power connector and the PCB, after having a 'scare' of this type with
another piece of equipment borrowed from a friend. I think this is a
modification that the units should have....

Best Wishes

> >
> > ----- Original Message -----
> > Sent: Sunday, November 04, 2001 4:25 AM
> > Subject: Re: [M]: Remote focusing via JMI?
> >
> >
> > > John,
> > > You're running into the same problem that I have now except I don't
have
> > > my NGF focuser but I do have MaxinDL-CCD and SkyMap Pro. (Mine is a
> > > LX200 10" f6.3 but that should make no difference)
> > > Heres what I've learned so far.
> > > 1. MaximDL out of the box only supports only three digital focus
> > > controls. RoboFocus is one that is a 'bolt' on stepper but I can't
seem
> > > to find any info on the net about it, dealer etc. RoboFocus requires
a
> > > separate serial port independent from the telescope and camera
control.
> > > MaximDL makes no mention of running any analog focus control drivers
> > such
> > > as the Meade. My intention was to adapt the Meade motor to the JMI
> > > focuser if I can get a driver for MaxinDL. They (MaximDL) do
mention
> > > that they will provide information about a focus driver if you
contact
> > > them. I will in the next week or so if I can adapt the motor etc.
> > > 2. MaximDL does not support SkyMap Pro but rather The Sky by Bisque.
I
> > > have both and much prefer SkyMap Pro because of the database
options.
> > > Maybe if enough people contact them, they might. I also have a
E-mail
> > in
> > > the people at SkyMap Pro.
> > >
> > > If I go the way of modifying a Meade motor to the JMI focuser, I
need to
> > > buy one more USB to Serial converter and a USB hub for my laptop to
> > cover
> > > all of the ports. Not a big problem here other than $$$.
> > >
> > > If anyone out there has any insight on what we are trying to do,
please
> > > respond.
> > Data about 'Robo-focus' is at:
> > http://www.homedome.com/robofoc1.htm
> > If you include the hyphen, a web search will find it.
> > Robo-Focus, can 'share' it's port with a telescope (don't know if you
can
> > do this in Maxim, but in AstroArt, it works). All you do is deselect
the
> > telescope application, and run the focus application. When you have
got
> > your focus 'right', turn off the focus application, and reselect the
> > telescope. Works for me with a LX200.
> > Robo-Focus, can be fitted to just about any focus knob, with a bit of
> > metalwork. I have ended up removing my NGF-S, and running Robo-Focus
on
> > the scopes own knob. Though this re-introduces the mirror-shift
problems
> > (Robo-Focus can correct for backlash), I was finding that the total
> > 'optical' length was so great, when wanting to use a focal compressor,
> > that spherical abberation was starting to get unacceptable, so
removing
> > the extra length of the NGF-S, was worthwhile...
> > I hope the new LX200-GPS, has the 'optimal' correction distance set
for a
> > longer optical length at the rear of the scope, to allow for it's
extra
> > focusser there.
> >
> > > On Fri, 2 Nov 2001 21:31:00 -0800 (PST) John Teel
> > > writes:
> > > > I'm currently using a JMI NGF-SE non-motorized focuser on my 12"
> > > > LX200. I'm
> > > > now planning on getting into CCD imaging and will be doing most of
> > > > my imaging
> > > > remotely (either from my observatory's control room or from my
> > > > house). Can I
> > > > add a focus motor to this manual NGF focuser? If so, how do I
focus
> > > > remotely?
> > > > Do I need to run a cable for a hand controller or can I plug the
> > > > motor into the
> > > > LX200 focus port and then run the focus from the computer that is
> > > > connected
> > > > into the LX200's serial port? Thus far I've only used the serial
> > > > port to
> > > > control the scope from SkyMap Pro. I will be using MaximDL to
> > > > control the CCD.
> > > > How do I focus from the computer?
> > > >
> > > > Thanks,
> > > >
> > > > John Teel
> > The LX200 focus port is 'dumb', only comprising a motor
forward/reverse
> > signal. You can fit a simple motor to this, if you only want a simple
> > 'movement' control, but something like the Robo-Focus, adds more,
allowing
> > you to 'GOTO' a particular focus setting for various setups, and even
if
> > required to compensate for temperature variations.
> >
> > Best Wishes

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