Off Topic: NGF-S Focuser
Stephen M. Brincat
Hello to All,
As I've seen some contributions mentioning the JMI NGF-S focuser, I wish
to ask a question that I hav'nt yet found an answer for.
I intend to couple my Meade equatorially mounted SCT(on LXD 650 mount) to
a CCD Camera. There are two NGF-S focusers available from JMI. As I will
be using a CCD ,I thought that the NGF-S MINI(1 1/4) would be enough for
my needs as my field will be limited. Do I really need the standard NGF-S
or the mini version is enough?(I do not have any 2" eyepieces). Thanks in
advance.
Stephen M. Brincat
sbri...@maltanet.omnes.net
Richard G. DAVIS
IF YOU EXPECT TO USE A BARLOW WITH THE FOCUSER, THEN YOU SHOULD BUY THE NGF-S
MODEL, WHICH WILL LET THE EXTENDED TUBE OF THE BARLOW FIT UP THROUGH THE
FOCUSER BODY.
The 'mini' focuser won't allow the barlow to be seated up into the eye-piece
holder.
The mini, in its defense, does offer a much longer range of motion. With the
NGF-S, I have to achieve rough focus with the main focus knob, and then refine
the focus with the NGF-S. That's not a problem, just a difference in the
methods of use for the two designs.
DBake...@aol.com
Someone please explain to me the advantage to using a NGF-S Focuser over an
OEM electric focuser from Meade.
Thanks!!!
DBaker1047
Stewart Squires
The OEM electric focuser slides over the focusing knob and still moves the
mirror. The JMI focuser is a crayford style that mounts in between the
diagonal and the backplate of the scope. You still focus with the focusing
knob, but only to close focus. Then move the tail piece in and out to fine
focus with the JMI. Both plug into the drive base for power although the JMI
has a hand controller too; it also works with an LX200 handset.
I have a NGF-S on my LX200 Mak and lots (relatively speaking) of image shift
that no long bother me at all!
-
Stew Squires
... islands lie behind the sun that I shall raise ere day is done.
Bilbo's Last Song, J.R.R. Tolkien
Frank Loch
On May 10th Steven Brincat wrote:
> Hello to All,
> As I've seen some contributions mentioning the JMI NGF-S focuser, I wish
> to ask a question that I hav'nt yet found an answer for.
>
> I intend to couple my Meade equatorially mounted SCT(on LXD 650 mount) to
> a CCD Camera. There are two NGF-S focusers available from JMI. As I will
> be using a CCD ,I thought that the NGF-S MINI(1 1/4) would be enough for
> my needs as my field will be limited. Do I really need the standard NGF-S
> or the mini version is enough?(I do not have any 2" eyepieces). Thanks in
> advance.
>
Steve -- It may depend on the size of your scope. For 10" and larger
JMI offers a Non-Vignetting adapter for the sct backplate. I'm using
this with my 12" lx200 with the standard NGF-s and an sbig st7 with a
2" adapter. Thus my entire system (including filters) is 2". My
philosophy for this is to keep the whole system as large as possible
to eliminate Vignetting as much as possible. Hey, some day you might
want to stick a 35mm Panoptic in there also <g>.
Frank Loch -- fl...@prolog.net
Kal Krishnan
The Mini has the advantage of giving you greater focus travel. But, it has
a limited weight bearing capacity. You may want to give JMI a call. They
are nice folks, and will help you out.
----------
From: Stephen M. Brincat[SMTP:sbri...@maltanet.omnes.net]
Sent: Friday, May 10, 1996 9:19 AM
To: ma...@shore.net
Subject: Off Topic: NGF-S Focuser
Hello to All,
As I've seen some contributions mentioning the JMI NGF-S focuser, I wish
to ask a question that I hav'nt yet found an answer for.
I intend to couple my Meade equatorially mounted SCT(on LXD 650 mount) to
a CCD Camera. There are two NGF-S focusers available from JMI. As I will
be using a CCD ,I thought that the NGF-S MINI(1 1/4) would be enough for
my needs as my field will be limited. Do I really need the standard NGF-S
or the mini version is enough?(I do not have any 2" eyepieces). Thanks in
advance.
Stephen M. Brincat
sbri...@maltanet.omnes.net
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Frank Loch
On May 10th D Baker wrote:
> Someone please explain to me the advantage to using a NGF-S Focuser over an
> OEM electric focuser from Meade.
The Mead electric focuser simply mounts on and turns your normal
focus knob with all of its inherent shortcommings including image
shift.
The NGF-s attaches to your scope backplate instead of the 90 degree
diagonal. You then insert your eyepieces or CCD or diagonal into it.
The electric motor then moves these devices into or out of focus
without moving the mirror with very fine adjustment movements.
To guild the lily a bit more you can also attach the JMI DFC to the Mead
focus knob for a digital record of your focus positions (very
repeatable) and add the JMI DRO to the NGF-s for electronic digital
readout of the NGF-s focus positions.
Frank Loch -- fl...@prolog.net
Kal Krishnan
The Meade focusser simply replaces the existing focusser. Hence it has all
the problems including backlash, image shift etc. At higher magnifications,
this is extremely annoying.
The NGF moves the eyepiece (or camera), not the mirror; so, it has none of
the problems of the regular focusser. However, its focussing range is quite
limited.
You could actually get both, (if you have mucho $$$!) and use one for rough
focus, and the other for fine focus.
----------
From: DBake...@aol.com[SMTP:DBake...@aol.com]
Sent: Friday, May 10, 1996 7:08 AM
To: ma...@shore.net
Subject: Re: Off Topic: NGF-S Focuser
Someone please explain to me the advantage to using a NGF-S Focuser over an
OEM electric focuser from Meade.
Thanks!!!
DBaker1047
Stewart Squires
Another thought - There is a larger travel distance in the 1.25" focuser than
the 2", 1.5"? vs .5", respectively.
Stephen M. Brincat
Hello to all,
Thank you very much for illuminating me to what NGF-S I should
get. I think I should get the mini version as the CCD I will be using
have a chip as large as the ST7 and weight is not much a problem. Focus
travel gets priority as I maybe using it with an F6.3 Focal Reducer
making my system to f4 from f6.3.
Stephen M. Brincat
sbri...@maltanet.omnes.net
>From the Island of Malta.