Coronado PST Double Stack Filter question

[04Stefan07 (Stefan)]

Does anyone know how much these filters go for? I know they are expensive but having trouble finding an Australian shop who stock it.

Wonder if a second hand one can be picked up.

Is it worth the money to upgrade it?

[OICURMT]

I've never seen the SM40 used for less than U$400... you may get lucky, but I seriously doubt it.

As for upgrade, you'll have to define it. The PST is a fine grab&go solar, double stacked would be even better... wish I had an SM40 for mine.

OIC!

[casstony]

There's a large increase in contrast with the double stack - light grey filaments turn black. It's definitely worth double stacking the pst.

[GUS.K (Ivan)]

Bought one from Bintel about 3 years ago,for $700, I'm not sure if they still sell them. I personally didn't find the view that much better, that justified the cost.

GUS.K

[SteveInNZ]

I have a PST and have been bitten by the bug too. I'm not really sure what is the best upgrade path but I did put some numbers together.
The figures are list US$.
Double stack the PST $600
Double stack the PST with a 10mm blocking filter $1100
Mod the PST etalon etc into a 70mm f/11 refractor $900
Buy a 60mm Lunt or Solarmax $1500 (less sale of PST)
Buy a 60mm Lunt or Solarmax double stack $2300 (less sale of PST)
Daystar Quark $1000

Most of the bits can be bought from optcorp.com or telescopes.net

Hope that's of some help.

Steve.

[sungrazer (Karen)]

Hi
I have a double stack pst
Got mine at bintel
Totally worth the money for the double
Cheers karen

[UniPol]

I recall a few years back having a PST and SM40 . The SM40 etalon screwed directly onto the PST hence a double stacked arrangement. The problem I found was that there were double images, ghosting and flaring owing to the fact that the two units are tuned separately so that a fair bit of fiddling was necessary to tune the image. The final image was much darker however surface features were evident but prominences were almost lost.

Perhaps somebody may correct me but I thought double stacked scopes units were supposed to be tuned at the factory? at least pre Meade Coronado's said this in their advertising some years ago. I get the impression that anybody who buys a dedicated double stacked set up don't appear to have any issues.

[casstony]

PSTs and pressure tuned Lunts don't require factory matching since the etalon is perpendicular to the incoming light so adding a tilt-tune double stack is very unlikely to result in ghost images. It's possible to get a more ideal match with the factory testing different filters but non-factory matching rarely results in problems.

Even two tilt-tune etalons won't give ghost images if the primary filter comes 'on band' with minimal tilt and the second filter (double stack) comes on band with more tilt.

Ghost images happen when the two etalons have the same amount of tilt when tuned.

[Merlin66 (Ken)]

None of the double stacked etalon arrangements need "factory setting" - that was marketing hype.....
I regularly used a pair of Coronado SM60 etalons double stacked on an ED80. The initial set-up is a bit of a PITA but certainly achievable.
The concept is to have both external filters tuned together "on band" then always move them as a co-joined pair.
Were you have a combination of an external and internal filter, they must both be tuned independently to achieve an "on-band" setting.
This is easily by finding when there is a slight image brightness increase.

I have an SM60 external filter fitted to a 102mm PST mod and the results are almost as good as the original double SM60. Majic.

[sungrazer (Karen)]

Hi

Yes there is ghosting and double images on a double stacked pst
I tune them out so they aren't a real problem but I did think something was wrong initially.


I have good proms with the double stack and actually prefer now to image with the double on rather than without. It's personal taste really.


I take quite good images and now timelapse with this arrangement. Best thing to do is get a look at someone's set up


Cheers
Karen