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PST Prism Alignment problem - assistance please if possible

Posted: Sat Dec 17, 2016 6:26 am
by Sungrazer
Hi All

my Pst has decided to put itself out of alignment - and I don't mean the parallel to the top alignment that people often talk about.

The prism seems to have shifted internally such that it moves from forward to back - i.e it is rocking left to right while in the slider. (I have not dropped it, but it does get a lot of use - long prom timelapse is my fav. thing to do as you may know - so maybe it is a wear problem)

I have attached the photos of the sun I get as a result of the prism being misaligned as well as a short video here https://vimeo.com/196057192 showing the alignment problem.

What i know so far is:"
The PST cover plate pushes the prism into alignment when it is screwed back in place - my problem is that when it is screwed back in place it pushes it back into the the 'out of alignment' position.
Obviously I have opened it up to look at it but I don't know how to detach the focusing screw to get a closer look and I don't want to do that in case I make the repair job harder for a professional. So far all i have done is take the cover plate off.

My question is - (outside of the obviously professional lads at Bintel in Sydney) has anyone seen this thing happen before? and does anyone in the forum have experience repairing this kind of problem. Do you place something behind the prism to prevent the cover pushing it out of alignment, or has something broken or worn out? (nothing fell out when i took off the cover plate). is it easy to repair?

Thanks so much in advance.

cheers
Karen

Re: PST Prism Alignment problem - assistance please if possible

Posted: Sat Dec 17, 2016 7:12 am
by marktownley
Post a pic with the side of the box off Karen

Re: PST Prism Alignment problem - assistance please if possible

Posted: Sat Dec 17, 2016 10:12 am
by Sungrazer
Hi Mark

thanks
this is the only pic of it I have plus a screengrab - though the video does show the whole mechanism moving.

Re: PST Prism Alignment problem - assistance please if possible

Posted: Sun Dec 18, 2016 10:19 pm
by marktownley
Difficult to see what is going on there, even in the video. I personally wouldn't want to suggest anything to try for fear of damaging further. You need a boffin to look at it first hand.

Re: PST Prism Alignment problem - assistance please if possible

Posted: Mon Dec 19, 2016 10:15 am
by Montana
Honestly I am not the right person to listen too but I know that when folks do PST mods they remove the gold tube from the front and have the body left over as a spare part. Would it be possible to buy or get for free this spare body part to screw your gold tube on to, then the problem would be fixed?

Alexandra

Re: PST Prism Alignment problem - assistance please if possible

Posted: Mon Dec 19, 2016 12:14 pm
by marktownley
That's a good cunning plan Alexandra!

Re: PST Prism Alignment problem - assistance please if possible

Posted: Mon Dec 19, 2016 2:22 pm
by Merlin66
Karen,
I can probably help you.
Drop me a PM or email and we can arrange a phone call/ skype.
Ken

Re: PST Prism Alignment problem - assistance please if possible

Posted: Tue Dec 20, 2016 9:48 am
by Sungrazer
Montana wrote:Honestly I am not the right person to listen too but I know that when folks do PST mods they remove the gold tube from the front and have the body left over as a spare part. Would it be possible to buy or get for free this spare body part to screw your gold tube on to, then the problem would be fixed?

Alexandra
yes that's a good plan B. :-)

I have the Clubs spare PST ATM which had a rusted out gold front lens so I have that up my sleeve - I have started the mod :-) so the gold tube is off and the screw in from telescop Austria is now attached. The plan was however to be able to use that back end on occasion with the ED80 and use my PST as a guider for long timelapse sequences. So ideally I would like both scopes working. Plus it is the clubs equipment and someone else may want to use it as well.

I will post pics of the mod as soon as I can get focus :-)
K

Re: PST Prism Alignment problem - assistance please if possible

Posted: Tue Dec 20, 2016 9:48 am
by Sungrazer
Merlin66 wrote:Karen,
I can probably help you.
Drop me a PM or email and we can arrange a phone call/ skype.
Ken
thanks Ken
will do
Karen

Re: PST Prism Alignment problem - assistance please if possible

Posted: Mon Dec 26, 2016 5:10 am
by axlefoley
I have 2 black boxes somewhere in my shed if you are interested in one.

Make me an offer.

I'm in Townsville Australia

alan_lorraine@yahoo.com.au

Alan