Re: [MaxImDL] remote focuser?


Apr 11, 2002

 


----------------------------

#2061 Apr 11, 2002

I need a recommendation on a focusing gizmo for the C14. It would have

to work with Maxim and have temperature compensation. I am using an ST8e

with CFW. I'm looking for the best interface with both software and

hardware. Forgetting about costs (for the moment) should I be looking at

the kind that just turns the focusing knob, or the kind that works like

it's own rack and pinion focuser on the back of the C14? I also want to

be able to sit inside the cozy astronomy cabin and work it.

Help!



--

==

Greg Mueller Port Gamble, Washington

Amateur Astronomer, Machinist, Filmnut



Tech Tools and Astronomer's Gizmos

www.muellersatomics.com/

==



----------------------------

#2063 Apr 11, 2002

--- In MaxImDL@y..., Greg Mueller mueller@s...> wrote: > I need a recommendation on a focusing gizmo for the C14. It would

have > to work with Maxim and have temperature compensation. I am using an

ST8e > with CFW. I'm looking for the best interface with both software and

> hardware. Forgetting about costs (for the moment) should I be

looking at > the kind that just turns the focusing knob, or the kind that works

like > it's own rack and pinion focuser on the back of the C14? I also

want to > be able to sit inside the cozy astronomy cabin and work it.

> Help!

>

> --

> ==

> Greg Mueller Port Gamble, Washington

> Amateur Astronomer, Machinist, Filmnut

>

> www.muellersatomics.com/

> ==

> Tech Tools and Astronomer's Gizmos



Greg,



I use the Optec TCF-S in my observatory (a Meade 12 inch LX200)

which is controlled from my home about 70 feet of cable away. I have

no problems running it with Maxim or FocusMax and I have it wired up

with the hand control at my computer in the house, so I can also use

it manually if needed (you can also leave the hand control in the

observatory and run it with a pc in house if desired).



Frank Zoltowski...



----------------------------

#2064 Apr 11, 2002

I would recommend either the RoboFocus www.homedome.com or the Optec TCF-S www.optecinc.com . I have both on my 8 inch LX-200 and both are fine products. They both have temperature compensation and both work with the MaxIm DL/CCD V 3 internal autofocus or you can use them with MaxIm and the FocusMax autofocus software available as freeware at www.focusmax.org . I always use them from the comfort of my warm room!



Larry Weber







----- Original Message -----

From: "Greg Mueller" mueller@...>

To: MaxImDL@yahoogroups.com>

Sent: Thursday, April 11, 2002 5:06 PM

Subject: [MaxImDL] remote focuser?





> I need a recommendation on a focusing gizmo for the C14. It would have

> to work with Maxim and have temperature compensation. I am using an ST8e

> with CFW. I'm looking for the best interface with both software and

> hardware. Forgetting about costs (for the moment) should I be looking at

> the kind that just turns the focusing knob, or the kind that works like

> it's own rack and pinion focuser on the back of the C14? I also want to

> be able to sit inside the cozy astronomy cabin and work it.

> Help!

>

> --

> ==

> Greg Mueller Port Gamble, Washington

> Amateur Astronomer, Machinist, Filmnut

>

> Tech Tools and Astronomer's Gizmos

> www.muellersatomics.com/

> ==



----------------------------

#2065 Apr 11, 2002

I'm very happy with RoboFocus, especially since FocusMax.

(For some reason no one would answer my plea as to whether I should

install it to my LX200GPS when it comes.) -turgut





-----

Turgut Kalfaoglu: www.kalfaoglu.com

EgeNet Internet Services: www.egenet.com.tr



----------------------------

#2067 Apr 11, 2002

There are advantages and disadvantages to either approach. If you drive the focus knob, you can't lock your mirror, and have the possibility of image shift during focusing, but you also have a system that can be focused absolutely, so that you can completely change around your optical configuration and always have the ability to go directly to the proper focus position. If you use an external focuser, you can lock the mirror and be certain that there will be no shift during focusing, but you will still need to use the knob when you change your equipment around, and then recalibrate your focuser.



The choice will depend on the performance of your scope, and the kind of imaging you do. If you don't normally make single images longer than 10 minutes or so, then mirror flop shouldn't be an issue (even less so when using the ST8 to guide), and a good focuser like the RoboFocus pretty much eliminates shift. I am very happy with the performance of my 12" LX200/RoboFocus combination, and particularly like the ease with which I can switch between visual and CCD without losing my focus calibration. I do most of my imaging remotely, and RoboFocus works great for that.



Chris Peterson

www.cloudbait.com



----- Original Message -----

From: "Greg Mueller" mueller@...>

To: MaxImDL@yahoogroups.com>

Sent: Thursday, April 11, 2002 3:06 PM

Subject: [MaxImDL] remote focuser?





> I need a recommendation on a focusing gizmo for the C14. It would have

> to work with Maxim and have temperature compensation. I am using an ST8e

> with CFW. I'm looking for the best interface with both software and

> hardware. Forgetting about costs (for the moment) should I be looking at

> the kind that just turns the focusing knob, or the kind that works like

> it's own rack and pinion focuser on the back of the C14? I also want to

> be able to sit inside the cozy astronomy cabin and work it.

> Help!







----------------------------

#2069 Apr 12, 2002

I need a recommendation on a focusing gizmo for the C14. It would have

> to work with Maxim and have temperature compensation. I am using an ST8e

> with CFW. I'm looking for the best interface with both software and

> hardware. Forgetting about costs (for the moment) should I be looking at

> the kind that just turns the focusing knob, or the kind that works like

> it's own rack and pinion focuser on the back of the C14? I also want to

> be able to sit inside the cozy astronomy cabin and work it.

> Help!

Hopefully not a 'rack and pinion', but something a lot smoother...

The 'answer' depends on what you want to do. The first type of focusser,

is something like the 'RoboFocus'. This can be an excellent solution. The

problems of this, are that you retain the mirror shift associated with the

SCT, when you cross the meridian (the shift when focussing, is concealed

by the software, applying a 'backlash' correction). The unit allows the

full range of the SCT focus (useful if you want to use multiple optical

configurations), and provides an 'absolute' GoTo capability for the

focussing (so you can switch to a different optical setup, and tell it to

go to the setting for this configuration, and after a few minutes while it

moves the focusser - it is _slow_ -, the system is allmost in focus

straight away.

The Crayford style focusser (Optec or JMI type unit), has the disadvantage

that if is not 'absolute', but dependant on the setting of the primary

focusser. However if you fit a mirror lock, it gives the smoothest focus,

with 99% removal of the mirror shift (nearly 100%, but nothing is

perfect...). However it does not give enough focus range to do anything

much beyond focussing one specific instrument configuration, and increases

the length of optical configuration at the rear of the scope significantly

(can give increased spherical aberation).

So the first solution is 'better' if you are likely to be changing the

optical configuration. The second solution, gives finer focus, and solves

the mirror shift problem, and is better for a 'fixed' configuration. You

can also use the same 'hardware' (the RoboFocus motor and software), on a

JMI style focusser, which then gives (provided the primary mirror remains

locked), the same 'absolute' GoTo ability, over a limited range.

Maxim directly drives the RoboFocus, or Optec units (and the RCOS system),

and the 'interface' is basically the same in all of them when used this

way.



Best Wishes



----------------------------

#2072 Apr 12, 2002

A solution that I use to solve the "change configuration", "SCT mirror

flop" and "absolute focus position" problems is to use the JMI turns

counter on the SCT mirror focuser to obtain repeatable instrument

configurations, then lock down the mirror after setting this focuser. My

TCF-S can then be calibrated and has plenty of travel to compensate for the

small errors in resetting the SCT mirror position using the turns counter.

So, my procedure is to install the instruments I want to use, turn the knob

with the JMI counter to the correct number (it goes 1-1000), lock down the

mirror with a thumb nut, then do a normal Auto-Focus with the TCFS (or

Robofocus). Quick, simple and works!



Richard













At 09:40 PM 4/11/2002 -0600, you wrote: >There are advantages and disadvantages to either approach. If you drive

>the focus knob, you can't lock your mirror, and have the possibility of

>image shift during focusing, but you also have a system that can be

>focused absolutely, so that you can completely change around your optical

>configuration and always have the ability to go directly to the proper

>focus position. If you use an external focuser, you can lock the mirror

>and be certain that there will be no shift during focusing, but you will

>still need to use the knob when you change your equipment around, and then

>recalibrate your focuser.

>

>The choice will depend on the performance of your scope, and the kind of

>imaging you do. If you don't normally make single images longer than 10

>minutes or so, then mirror flop shouldn't be an issue (even less so when

>using the ST8 to guide), and a good focuser like the RoboFocus pretty much

>eliminates shift. I am very happy with the performance of my 12"

>LX200/RoboFocus combination, and particularly like the ease with which I

>can switch between visual and CCD without losing my focus calibration. I

>do most of my imaging remotely, and RoboFocus works great for that.

>

>Chris Peterson

>www.cloudbait.com

>

>

>----- Original Message -----

>From: "Greg Mueller" mueller@...>

>To: MaxImDL@yahoogroups.com>

>Sent: Thursday, April 11, 2002 3:06 PM

>Subject: [MaxImDL] remote focuser?

>

>

> > I need a recommendation on a focusing gizmo for the C14. It would have

> > to work with Maxim and have temperature compensation. I am using an ST8e

> > with CFW. I'm looking for the best interface with both software and

> > hardware. Forgetting about costs (for the moment) should I be looking at

> > the kind that just turns the focusing knob, or the kind that works like

> > it's own rack and pinion focuser on the back of the C14? I also want to

> > be able to sit inside the cozy astronomy cabin and work it.

> > Help!

>

>

>

>

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>

>

>

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