Kowa TSN773/883 with 1.25" star diagonal? (1 Viewer)

[iseegeorgesstar]

Hello,

I know there are threads about the kowa and astro EP use with the adapter. I'm wondering if one could, or if anyone has tried, using a 1.25" star diagonal with the astro adapter and then an EP? Is focus an issue due to the kowa short f ratio or focuser?

Would adding a diagonal make focusing more difficult or help the optical path?

The spotting scope shows a "correct" image so would a star diagonal reverse this? It would be upside down?

The reason I'm asking is because I've been mulling over the idea of whether to go straight-thru or angled. And it occurred to me that with as astro adapter one could use a diagonal in a straight-thru model thus have best of both worlds in a small way. I was looking at the smaller models of Kowa but only the larger ones seem to accept the astro adapter.

Thanks for your thoughts and experience.

 

[Tringa45]

The spotting scope shows a "correct" image so would a star diagonal reverse this? It would be upside down?

The image would be upside down and you would not be able to get anywhere near infinity focus because of the additional light path.

John

 

[DRodrigues]

The most probable way of reaching focus with a diagonal is using TSN-PS1 and even so you probably need the shortest light path diagonal available that is Baader T2 Prim Diagonal 32 - don't know if the Kowa accessory still is produced since didn't found it in the Kowa web-page...

 

[iseegeorgesstar]

I guess that's why small refractors are still in vogue.

Thank you for the links and information. I had seen straight thru adapters to get refractors into infinity focus. The camera adapter is a novel idea.

Thank you both.

 

[jring]

Hi,

in general spotting scopes with their internal focus drive have very limited focus travel as compared to most astro refractors so even if there is a way to mount 1.25" astro EPs usually not all will come to infinity focus - with the big body Kowas, there are two adapters - the one with the grub screw trades some ease of use for a millimeter or two of backfocus - which might be just what your favourite EP needs to come to infinity focus...

So forget about anything that gives extra optical path... unless you also want to use a barlow - that might bring the focal plane out enough for your experiments... but then you must hope that you were lucky in the objective lottery to supprt the higher magnification (remember - insanely fast ED refractor... tricky to get right and will show every bit of aberration very well).

Joachim, who thinks that this is not feasible

 

[iseegeorgesstar]

Thank you for the comments. I'm reminded of a picture I saw on CN which was also shared here of someone bringing I think it was an ethos EP to focus in a TSN-883 with a long form barlow. Take about long optical chain.