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Author Topic: PST Extension Tube Removal  (Read 19424 times)

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Offline DigitalSky

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PST Extension Tube Removal
« on: 11:54:18, 04 May, 2006 »
Ok - not had a lot of time to do this what with the Sun being visible during the day and stars sometimes visible at night!

It's a start though...

http://www.digitalsky.org.uk/PST/PST-mod.html

The third image down is the one that hides the brute force needed to unscrew the Locktite'd extension tube from the PST body. You'll get the idea though - I'm sure  ;)

Offline NickH

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Re: PST Extension Tube Removal
« Reply #1 on: 12:12:33, 04 May, 2006 »
Indeed...

Get those Boa constrictor orders in now...

Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline DigitalSky

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Re: PST Extension Tube Removal
« Reply #2 on: 22:18:40, 06 May, 2006 »
Get us some share options Rob2 - the constrictors are going to be in big demand...   :D

Offline LAWMAN

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Re: PST Extension Tube Removal
« Reply #3 on: 22:33:34, 07 May, 2006 »
Maybe use the larger boa constrictor as the small one snapped on me when removing it.
lol the chap that made the Boa probally seen sales go up since the mod was found.  lol
Ian

Nice work Pete sure it will help folk out.  Nice one
Tak Mewlon-180
PST, TV85,
EQ6 Pro

Offline swac3

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Re: PST Extension Tube Removal A Warning
« Reply #4 on: 15:31:34, 26 May, 2006 »
* A word of caution *

I had a play today with my pst removing  the pesky spacer. A ton of threadlock stuff
finally gave way with some superficial scrapes to the spacer. (no big deal to me)

However, what i did notice was how high up in the body of the Pst the large prism
gets at one end of its travel and how deep the BF looked to go in the body of the pst
when screwed fully home. So a little measuring before reassembly reveals...

With the spacer removed and the BF portion screwed fully down turning the focusser
fully one way will cause the prism to touch the bottom of the BF holder.


in use i'd doubt you would damage the prism unless your a bit of a gorilla with the focus knob
but its worth moving the prism lower when screwing the BF tube into the pst as there's potential for
chipping the edge of the prism or damaging the focus mechanism.

All done now here and ready for testing with a camera, just a shame its raining :(Â  



 
Gary. 
 Megrez 80 II FD : TV60 : PST Ha+CaK
 Vixen gpdx - ss2k Goto : Toucam  Pro2  :Canon 350d :ASTSC1BW
 Clouds: various types, free to uplift.
  http://www.aukq21.dsl.pipex.com/

Offline NickH

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Re: PST Extension Tube Removal
« Reply #5 on: 16:51:27, 26 May, 2006 »
The one bonus I found was the the PST extention tube fitted perfectly into the thread on my Sony TRV camcorder... :-) (Happy days..as it saved me a few quid)

What I think is needed is some form of low profile spacer to replace the PST one (BCF are you watching/listening AE engineering) which would get around the prism crunch issue (not that I have seen it yet), and a helical or better focuser mechanism built in to it, which would (IMHO) be a big improvement on the one on the PST's

Just my 2cents

Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline DaveS

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Re: PST Extension Tube Removal
« Reply #6 on: 17:43:01, 26 May, 2006 »

What I think is needed is some form of low profile spacer to replace the PST one (BCF are you watching/listening AE engineering) which would get around the prism crunch issue (not that I have seen it yet), and a helical or better focuser mechanism built in to it, which would (IMHO) be a big improvement on the one on the PST's


Sounds like a good option Nick, and it would be quite easy to make.

I've made a number of extensions/spacers etc on my little hobby lathe, and something like this would be simplicity in itself for Arthur, if there was enough demand of course.

Don't have the need for one one myself, as my re-housed SPC900NC reaches focus on the PST without any problem, and I've no plans to 'hang' anything else on the PST at the moment.

Dave
Dave

Offline NickH

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Re: PST Extension Tube Removal
« Reply #7 on: 19:17:23, 26 May, 2006 »
Dave

Great that is promising to hear that it should be easy to make. The PST focuser is one of it's weak points, and some form of helical/finer focus I would personally love to get hold of.

Let's see if anyone takes up the challenge

Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline swac3

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Re: PST Extension Tube Removal
« Reply #8 on: 22:34:34, 29 May, 2006 »
Anyone know what the thread is on the spacer/Bf ?
Gary. 
 Megrez 80 II FD : TV60 : PST Ha+CaK
 Vixen gpdx - ss2k Goto : Toucam  Pro2  :Canon 350d :ASTSC1BW
 Clouds: various types, free to uplift.
  http://www.aukq21.dsl.pipex.com/

Offline DigitalSky

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Re: PST Extension Tube Removal
« Reply #9 on: 22:22:53, 01 June, 2006 »
One chap I was talking to today has reported an extension tube with an addional energy rejection filter in place. Anyone know if Coronado changed the design at some point and from which serial number? Odd, my extension tube is completely hollow.

I would hold off doing the mod until this is clarified.

Offline NickH

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Re: PST Extension Tube Removal
« Reply #10 on: 22:57:56, 01 June, 2006 »
Pete

That was Ian Pass. I know him, and I will try to clarify it tomorrow with him, asd he lives nearby and is a member of Wiltshire Astro soc. I have seen a limited run of PST's witha gold objective, due to this cement issue with the objectives "fogging up" (200 units I heard have the gold front) Possible coronado have implemented a second ERF on those ones. He had it picked up from the states last week, so it is possible.

Will let you know

ATB

Nick
Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline DigitalSky

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Re: PST Extension Tube Removal
« Reply #11 on: 08:52:49, 02 June, 2006 »
Cheers Nick, I'd like to know what's been done and whether it will image with the extension piece removed still. I guess it will but it's probably not safe for visual work. You'd thin with all of the imaging work being carried out with these little scopes and the fact that pictures are great adverts for Coronado, the company would be falling over themselves to clarify the situation here and possibly even supply alternative eyepiece holders.

Offline NickH

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Re: PST Extension Tube Removal
« Reply #12 on: 18:01:00, 02 June, 2006 »
So an update

They HAVE changed them, looks like they have added a second ERF and changed the tube by the look of the images Ian (chap who Pete was talking to) has sent me.

SO ANYONE THINKING OF doing this mod,  be careful, as it may...repeat may...

A: Damage the PST far easier, or the filter

B: it may transpire that this second filter is essential for visual use, removal could seriously damage your eyesight..that is the most worrying aspect. Nothing so far is documented by Coronado as to the nature of the changes.

The images are blurry , so I may be wrong, didn't see Ian today. It may be that the second filter is in fact some form of correcting lens to allow proper focus..who knows,,juat be careful, the old spacer was just a hollow tube...this one is not..

I would (as Iguess would Pete) recommend that you check before trying the mole grips/boa constrictor.

Hopefully this is a good thing, hopefully they have added some glass to allow DSLR and standard webcam focus...

Hopefully!



[attachment deleted by admin]
Celestron C11: DSI-C/Toucam Pro 2 ICX mod and SC1.5 mod/ Meade LPI/EOS300D/ED80/WO80ZS/Shoestring guider. PST/PST CaK/ART285

No time....always bloomin cloudy...need to build the Obsy..

Offline number26

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Re: PST Extension Tube Removal
« Reply #13 on: 20:53:50, 02 June, 2006 »
Hi Nick, is the upshot of this that the PST does not come to focus (I have a Canon 20D) without the mod. And that in the new versions the mod may be unsafe and therefore imaging with a DSLR is not an option?

I was thinking of investing but am very keen to image with the 20D without having to muck around with the scope.

Thanks
Mark.
Mark

LXD75 6N, Revelation 80, a VERY old C8, Coronado PST, NexImage, Canon 20D

Offline Dogman

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Re: PST Extension Tube Removal
« Reply #14 on: 02:40:37, 03 June, 2006 »
Thanks for the heads up .....

a) can you tell if the extra filter is in without taking them apart?
b) will an ordinary Toucam focus - ie is it just DSLR's that have a problem?

I just went for the Kansas Power deal - they should be here next week - I'll be a bit miffed if I can't image through them!!!!

Cheers
Dunc

Meade LX200 12" Classic, ED80 Pro, PST Ha and PST CaK
Artemis 285 + TrueTech Filter Wheel + Astronomik Filters
MX7C + STAR 2000, Toucam(s)
http://www.dmiller.demon.co.uk/astronomy.htm
MPC Obs Code J68

 

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