Re: [ap-ug] "Motorized" Focuser


Feb 17 2:58 PM

 


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#15503 Feb 17 2:58 PM

This may be a bit off-topic for the AP group, but we have a lot of

knowledgeable people here.....



I have never like motorized focusers. It's always push the button - oops, I

went a little past - push the other button - oops, and so on. They always

seem to make zeroing in on perfect focus a difficult chore, and I always

cringe when someone hands me one of those two button control boxes after I

sit down at the telescope.



The TEC MC at WSP had a very slick motorized focuser. There was a shaft you

turned, much like that at an old fashioned potentiometer. The focuser moved

in response to how far you turned it, and the focuser position seemed to

correspond exactly to the rotational positioning of the shaft. It made

zeroing in on a precise focus very easy and very slick. I want one!



How is something like this done, and where do I need to look to figure out

how to build one of my own?



Thanks!



Clear skies, Alan



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#15506 Feb 17 3:19 PM

The TEC MC at WSP had a very slick motorized focuser. > How is

something like this done, and where do I need to look to figure out > how to build one of my own?



Contact Yuri, he would be your best source of info on that focuser.



Thanks,

Vahe



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#15517 Feb 17 4:24 PM

Hi Alan,



Did the shaft rotation of the focuser keep up with your rotational

movements or was there lag time when you reversed direction ?



Joe





Alan French wrote: >

> This may be a bit off-topic for the AP group, but we have a lot of

> knowledgeable people here.....

>

> I have never like motorized focusers. It's always push the button - oops, I

> went a little past - push the other button - oops, and so on. They always

> seem to make zeroing in on perfect focus a difficult chore, and I always









> cringe when someone hands me one of those two button control boxes after I

> sit down at the telescope.

>

> The TEC MC at WSP had a very slick motorized focuser. There was a shaft you

> turned, much like that at an old fashioned potentiometer. The focuser moved

> in response to how far you turned it, and the focuser position seemed to

> correspond exactly to the rotational positioning of the shaft. It made

> zeroing in on a precise focus very easy and very slick. I want one!

>

> How is something like this done, and where do I need to look to figure out

> how to build one of my own?

>

> Thanks!

>

> Clear skies, Alan

>

> To UNSUBSCRIBE, or for general information on the ap-ug list

> see groups.yahoo.com/group/ap-ug

>

> Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/



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#15526 Feb 17 5:30 PM

Mark,



Your not too far off! We dont use the cookie sheet or

grease just some lead flux, great for the lungs almost

as good as a cigar.



BTW: Did you guys have our famous Key West Rum Cigars?



Tim





--- Mark Jenkins markj@...> wrote: > Mix ingredients on low speed, spread on a lightly

> greased cookie sheet

> and bake at 350 degrees for 2 to 4 programmer weeks

> (or 6 man months)

>

> ;-)

>

> Mark

>

> On Monday, Feb 17, 2003, at 18:36 America/Chicago,

> Tim Khan wrote:

>

> > As for making one, you need a control processor,

> > driver chip for motor, a motor and reduction unit,

> > optical encoder, and some programming.

>

>

>

> To UNSUBSCRIBE, or for general information on the

> ap-ug list

> see groups.yahoo.com/group/ap-ug

>

> Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>





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

#15527 Feb 17 5:32 PM

In a message dated 2/17/2003 7:03:14 PM Central Standard Time,

adfrench@... writes:



> Thanks. Sounds like some work, but it could be interesting. I guess it

> will have to go after finishing up rebuilding the two 8" Newts, a new tube

> for the refractor, and finishing my square for the NYS Breeding Bird Atlas.

> Perhaps a project for next winter.

>



I did build something similar for the 9.25" FastMax. It used a simple stepper

motor driven by an Erickson chip. The input was from a 20 position rotary

switch which produced the pulses, which were then converted to stepper pulses

in half step mode. The motor was geared down somewhat so that one step was a

very small movement of perhaps .0002 inches. It took about 5 steps to see a

change in focus at the eyepiece, so it was essentially seamless. The motor

went forward or backward depending on which way you turned the switch. The

switch itself had very smooth motion so it almost felt like a potentiometer.

It felt just like turning a focus knob. There was no noticeable delay with

this system. On the control box, we added a 10X switch so that each switch

pulse would send 10 pulses to the stepper. This gave us fast motions for

quick focus.



The main disadvantage was that without the encoder on the motor shaft, there

was no way to repeat any particular focus setting when the power was removed.

This made it less useful for imaging, but would have no effect on visual

focusing. The nice thing about steppers is that with the power removed, you

can turn the knob manually for fast manual focusing.



Roland Christen





[Non-text portions of this message have been removed]







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#15529 Feb 17 5:41 PM

Alan,



Sound like you got some nice projects going too.



Tim



BTW: what is a NYS Bird Atlas?



--- Alan French adfrench@...> wrote: > Tim,

>

> I didn't notice the lag, but now that I know it is

> there g>.....

>

> Thanks. Sounds like some work, but it could be

> interesting. I guess it

> will have to go after finishing up rebuilding the

> two 8" Newts, a new tube

> for the refractor, and finishing my square for the

> NYS Breeding Bird Atlas.

> Perhaps a project for next winter.

>

> Clear skies, Alan

> >

> > As for making one, you need a control processor,

> > driver chip for motor, a motor and reduction unit,

> > optical encoder, and some programming.

>

>

>

> To UNSUBSCRIBE, or for general information on the

> ap-ug list

> see groups.yahoo.com/group/ap-ug

>

> Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>





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Yahoo! Shopping - Send Flowers for Valentine's Day

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

#15530 Feb 17 5:56 PM

Tim,



Alas, most of them have been taking far too long.



The NYS Breeding Bird Atlas is a survey to find out what birds are nesting

in NY State, and compare the results to the previous atlas. Each volunteer

has a square or squares to monitor, and monitoring involves watching for

signs of breeding (mating behavior, claiming territory, nest buiding,

nesting, eggs, fledglings, and so on).



Clear skies, Alan

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

From: "Tim Khan" timkhan@...>

To: ap-ug@yahoogroups.com>

Sent: Monday, February 17, 2003 8:41 PM

Subject: Re: [ap-ug] "Motorized" Focuser





> Alan,

>

> Sound like you got some nice projects going too.

>

> Tim

>

> BTW: what is a NYS Bird Atlas?

>

> --- Alan French adfrench@...> wrote:

> > Tim,

> >

> > I didn't notice the lag, but now that I know it is

> > there g>.....

> >

> > Thanks. Sounds like some work, but it could be

> > interesting. I guess it

> > will have to go after finishing up rebuilding the

> > two 8" Newts, a new tube

> > for the refractor, and finishing my square for the

> > NYS Breeding Bird Atlas.

> > Perhaps a project for next winter.

> >

> > Clear skies, Alan

> > >

> > > As for making one, you need a control processor,

> > > driver chip for motor, a motor and reduction unit,

> > > optical encoder, and some programming.

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the

> > ap-ug list

> > see groups.yahoo.com/group/ap-ug

> >

> > Your use of Yahoo! Groups is subject to

> > docs.yahoo.com/info/terms/

> >

> >

>

>

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

> Do you Yahoo!?

> Yahoo! Shopping - Send Flowers for Valentine's Day

> shopping.yahoo.com

>

>

> To UNSUBSCRIBE, or for general information on the ap-ug list

> see groups.yahoo.com/group/ap-ug

>

> Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>

>



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

#15535 Feb 17 6:31 PM

--- chris1011@... wrote: > The main disadvantage was that without the encoder

> on the motor shaft, there

> was no way to repeat any particular focus setting

> when the power was removed.

> This made it less useful for imaging, but would have

> no effect on visual

> focusing. The nice thing about steppers is that with

> the power removed, you

> can turn the knob manually for fast manual focusing.

>

>

> Roland Christen

>

Hi Roland,



Yes very true, must have an encoder, especially when

you de-energize the coils after 1 sec as is in our

case. We do this for two reasons. No 1, keeping the

coils energized produces heat. No 2, a side effect is

manual focus.



Currently we have two speed setting on the focuser,

the fine setting is microstepped, and the course is

full step. If I recall correctly Yuri calculated 4-5

full steps inside the focus tolerance at (.ooo12" x

0.60) per step with their focus mechanism on the 12"

Mak. Anyways, most people found the course focus gave

the best feel. Did you get to try out both speeds?



Tim



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

#15536 Feb 17 6:55 PM

In a message dated 2/17/2003 8:33:51 PM Central Standard Time,

timkhan@... writes:



> Anyways, most people found the course focus gave

> the best feel. Did you get to try out both speeds?

>



I don't know what speed it was set at, but it had a nice feel to it.



Roland Christen





[Non-text portions of this message have been removed]






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