Lunt B1200 with PST stage 1 how to adapt

[moriniboy]

I'm considering getting a Lunt B1200 as it will apparently work with the Coronado PST stage 1 conversion I have just finished.

I assume it is just a matter of adapting the BF5 ep holder to accept the B1200, has anyone got photos of their modded item or did you follow a different route.

Like the idea of a 12mm BF instead of the 10mm BF at more or less the same price.

Thanks all.

[Peter Drew]

I'm sure your assuption is correct and that's all you have to do to swap the BF's, exactly how will depend on the relative fits.

[michael.h.f.wilkinson]

The Lunt B1200 can be used both in 1.25" and 2" focusers, and its nose-piece can be unscrewed and replaced to alter the fit. I think the filter assembly in the diagonal has a T2 thread (male, if memory serves, I can check at home).

[allcart]

To be honest, if you are getting a BF1200 you might just as well go for a semistage 2 and dump the black box and replace with a proper focuser like JamesF did. Search for jamesF's stage 0.5 mod and you will get the idea.

[JamesF]

It's here:

http://stargazerslounge.com/topic/187570-pst-stage-05-mod/

James

[moriniboy]

Thanks for the link, looks good.

One concern l have is that everything hangs off the etalon, l wonder what the weight difference is between the black box and a 2" focuser.

When Coronado developed the PST just the gold ota and objective required the etalon for support. Perhaps i'm overthinking this?

[Peter Drew]

Not much weight difference I would have thought. As far as loading is concerned, just think of the force that is sometimes applied to dismantle some of these components, the only items that I can recall having been broken are the boa straps.

[JamesF]

Thanks for the link, looks good.

One concern l have is that everything hangs off the etalon, l wonder what the weight difference is between the black box and a 2" focuser.

When Coronado developed the PST just the gold ota and objective required the etalon for support. Perhaps i'm overthinking this?

If you look at the picture in this post:

http://stargazerslounge.com/topic/187570-pst-stage-05-mod/#entry1955886

What you can't see very well is that the dovetail is actually (just) in contact with the new adaptor. I admit that it was more of a happy accident than by design. I was thinking I'd probably have to put a spacer between the two before I found the rings and they just happened to work out right. I've not put a screw through the two, but there's no reason that couldn't be done. That would mean that the etalon isn't solely supporting the weight of the focuser.

James

[moriniboy]

Happy times.

[allcart]

Don't fret too much about it. That little etalon is very well made and is pretty damned strong. i have seen many variations of components that hang on the back of the etalon. Some even include binoviewers, all without problems.