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Newer Coronado PST with older SM40 double stack?!

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#1 Bogglman

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Posted 19 April 2013 - 11:52 AM

Hi all, I have a newer Mexican made PST and have a US made SM40 double stack which doesn't thread onto the newer PST. They both have different thread pitches. Anyone have a go at this before or if someone knows the thread type of the PST and SM40? :confused:

#2 Howlt

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Posted 23 April 2013 - 11:51 AM

I asked a Meade rep at NEAF if the threads were the same on the new filters because I have an older PST and was wondering if I could doublestack with a new filter. He said the 40mm, 60mm, and the 90mm were the same and that I wouldn't have to worry about matching filters "like they did in the old days" since the new filters rotate.

#3 Bogglman

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Posted 23 April 2013 - 02:10 PM

He's possibly correct. But if you want to use the t-max tuner from the USA era it will not thread onto the PST. Simply screwing on another filter onto the PST tube will yield minimal results. Must be able to tweak while you peek ;)

#4 marktownley

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Posted 25 April 2013 - 03:42 AM

I think it is a 55-52mm step down ring that you will need, which if you get of fleabay or somewhere like that are really cheap. I would recommend a metal one not plastic.

#5 Bogglman

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Posted 26 April 2013 - 01:32 AM

Thanks Mark ! I went to a few local places and none could help... :undecided: I'll have go at the step down ring.

#6 BYoesle

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Posted 26 April 2013 - 08:30 AM

If that doesn't work I've had good results from http://www.preciseparts.com

#7 Bogglman

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Posted 06 May 2013 - 02:03 PM

Step down rings were a no go. It appears to be a thread pitch issue. A 49mm will only give 1/2 turn then tighten.. Almost like the new PST is standard thread?!

#8 Eclipse

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Posted 22 May 2013 - 09:21 AM

I was a little concerned when I first read this thread. Being the owner of a US -made PST and having recently ordered the latest - and presumably Mexico-made - SME-40 double stack.
But no problem - they screw together beautifully as if they were made for each other - which of course they were !!
So is there any real issue here?






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