I may be incorrect about the image difference between a refractor &
reflector. I **should** know, but I would need to check.
In any event matching the alignment of the TTL extension with the O-GPS1
attached (to the telescope tube, presumeably) would add another
complication (possibility for error in precise alignment) that may or may
not be successfully overcome. For example the O-GPS1 doesn’t like being
near metal, and how do you gyrate the telescope with TTL/O-GPS1 attached to
perform the precise calibration?

Hope this helps.

Darren Addy
Kearney, NE

On Sat, Jun 9, 2018 at 10:10 AM Darren Addy <pixelsmi...@gmail.com> wrote:

> Your TTL idea would be unnecessary on a refractor, so you must be thinking
> of using a Newtonian design. In that case I don’t think it would work
> because the image is reversed. I think the program in the O-GPS would be
> designed to shift the sensor in only one direction (the one that work with
> ordinary camera lenses of a refractor-sort of design). Not sure though.
>
> Also, keep in mind that the maximum exposure time possible with the
> O-GPS/AstroTrack gets shorter and shorter as the focal length gets longer.
> A shorter exposure time with a longer focal ratio is the opposite of what
> you want for catching photons in astrophotography.
>
> Respectfully,
> Darren Addy
>
> On Fri, Jun 8, 2018 at 3:15 PM luiz felipe <luiz.fel...@techmit.com.br>
> wrote:
>
>> pretty much divided between the Vixen Polarie and the O-GPS 1. just
>> because if I get to use a small newtonian reflex, the camera will be
>> pointed at 90 degrees from the subject, and I don't think de astro
>> function of the O-GPS 1 can handle that.
>>
>> the Vixen Polarie is small, and seems able to handle both the APS
>> Pentaxes and a small reflex telescope - and as long as it's properly
>> aligned, the pics should be ok.
>>
>> as far as money goes, it's one OR the other, and that's why I'm looking
>> for advice. building a barn door star tracker is the third option, but
>> I'm not really with time to make a proper unit. toughts? ideas?
>>
>> thanks!!!
>>
>> --
>> luiz felipe
>> luiz.felipe at luizfelipe.fot.br
>>
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> --
> “The Earth is Art, The Photographer is only a Witness ”
> ― Yann Arthus-Bertrand, Earth from Above
>
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