Skywatcher DC Motor drive for PST etalon.

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Merlin66
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Re: Skywatcher DC Motor drive for PST etalon.

Post by Merlin66 »

Looks promising....
How does it perform in real life?
What about a solar video shows the tuning/ de tuning??


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Re: Skywatcher DC Motor drive for PST etalon.

Post by marktownley »

Good result!


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Re: Skywatcher DC Motor drive for PST etalon.

Post by Rusted »

marktownley wrote: Wed Dec 18, 2019 6:22 am Good result!
Thank you Mark.
Sorry it took so long to complete the project after my initial posts.
I really thought it would only be a couple of days for the belts to arrive.
But I was at the mercy of 18th Century European postal speeds!
With regular stops for fresh draw horses for the 2mph narrow boats along the British canal system. :roll:

Anybody who can lay their hands on the simple materials shown in this thread can have a motorised etalon.
Without requiring any machining, special manual skills or expensive parts.
Despite any attached label or increased price, all of these DC focuser motor clones look identical.

The worst part is freeing up the etalon rotation to allow the little motor to easily drive the knurled band.
I am still hoping to find an everyday replacement for the original O-rings somewhere in the 1.4-1.5mm Ø range.
It may end up needing heavy, sea fishing monofilament but the motor drive belt system doesn't care about a bit of "slop."

The "packing" line material really doesn't have to be in the form of closed, rubber rings.
It is only a means of support for the etalon outer shell and its "knurled" rubber band.

A length of solid monofilament line, cut just short of the circumference of the etalon housing grooves, is all it needs.
Again I thought it would be simple to find such a line in common weed trimmers but found only 1.3, 1.6, 1.65 and 2mm Ø.
The 1.3mm is slightly too small and causes a floppy etalon band. All the others are just too large and jam the etalon movement.


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H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Skywatcher DC Motor drive for PST etalon.

Post by Rusted »

The cloud was a real teaser today but I managed a few, short trials with the etalon tuning motor.

P1400455 rsz.JPG
P1400455 rsz.JPG (138.33 KiB) Viewed 3541 times


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H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Skywatcher DC Motor drive for PST etalon.

Post by Rusted »

A small update: A slightly shorter 240mm timing belt arrived in the post.
This meant I could have a lower profile on the etalon drive motor than with the 250mm belt.
I had to use the heavier of the two motor support brackets supplied in the focuser motor kit.

The bracket is too long and both the support bracket and motor plate need a curve filed on their ends.
Best to remove the motor plate to avoid getting metal dust in the motor/gearbox from filing.
[Remove the two, tiny, black, cross-head screws.] File and de-burr, then clean the plate carefully before refitting.

P1400488 rsz 600.jpg
P1400488 rsz 600.jpg (88.54 KiB) Viewed 3505 times


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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