Fitting a quart into a pint pot - need ideas please?

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DJD
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Fitting a quart into a pint pot - need ideas please?

Post by DJD »

Dear All,
On my Tal/PST mod I have a back end that I take out to the scope,plug into the scope
and am ready to viewing or imaging via a flip mirror.
It is all spaced out so that if I use my Tal focuser the visual and CCD image are just about con-focal. I have no need for
a secondary focuser.
All works nicely and has done for a few years.
ImagePSTrig by David Dench, on Flickr
I now want to throw a big spanner in the works and want to ( if the brief seeing allows ) image at a larger image
scale, by making a quick change.
The imaging arm that is on the straight through path of the flip mirror is the15mm Blocking Filter ( adapted 1.25" eyepiece holder )
followed by the camera assembly ( T to C adapter and PGR camera ).
I want a quick way to slip in some image multiplier quickly that does not require me to dissemble the arrangement and
rebuild it every time.
I have available a 2x Glasspath Corrector that I removed from a Baader amici prism. It is basically a 1.25" fit barrel that I fixed inside
a 15mm TS optics T extension tube. I also have a 1.25x Baader GPC that I have mounted inside a Baader T to 1.25" nosepiece.
I have from the distant past a 1.8x nosepiece barlow.
The simplest way and would give maximum leeway for adapters is to remove the flip mirror ( gives an extra 60mm ), but
ideally I would like to just make the change post blocking filter.
I have played with my GPCs without getting anywhere, I can't find a way that moves the focus point out without requiring some inwards
movement to achieve a sensible focus.
Anyone know enough about GPC spacings to suggest an obvious solution with the constraints ?
Best wishes,
David


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Re: Fitting a quart into a pint pot - need ideas please?

Post by marktownley »

Great mod David! I've thought about using a flip mirror a couple of times now for different things. Not familiar with the glasspaths to give specific advice, my approach would be to just experiment...


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Re: Fitting a quart into a pint pot - need ideas please?

Post by DJD »

OK, I am about to admit defeat.
I have found that my 1.8x nose piece barlow "works" within my constraints but I am not impressed
by its results.
Can anyone recommend a screw-in barlow in the range 1.5x to 2x that is working well for you ?
Many thanks,
David


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Re: Fitting a quart into a pint pot - need ideas please?

Post by marktownley »

Just use a cheap skywatcher barlow, they have the screw on nose and adjust the spacing of it until you get the magnification factor you're after David.


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Re: Fitting a quart into a pint pot - need ideas please?

Post by DJD »

Some good news and some bad news ....
Last week I bought myself a Baader Q-Barlow to use the 1.3x nosepiece part.
The good news - I played with it on a secondary scope and got some very sharp views with it at about 2x mag.
The bad news, I unscrewed it out of the 1.25" nosepiece and only the retaining ring ( the only piece visible when inserted )
came out on its own leaving the rest of the barlow inserted , allowing the three component lenses to fall out on to the carpet.
I have no idea how to re-arrange the three lenses into the correct order and orientation.
A bit of a design flaw unfortunately. Can anyone help?
Thanks,
David


Making the possible difficult and the difficult impossible.
Photos : https://www.flickr.com/photos/daviddench/albums/
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