Not at all. Mine is in the same shape as yours.
Ciao
Lorenzo
andrea tasselli · Mar 31, 2026, 05:36 PM
I just received my "first" OAG, bought used from eBay. It's the Antlia one with filter drawer and sports a 12x12mm prism. Upon inspecting the gizmo I found that the edge of the prism was chipped, as a roughly triangular shaped 2mm per side is missing on the side with reflective coating. While I'll try to get a refund (obviously) would the missing bit impact the useability of the OAG? I could paint it black but not sure this is a viable option.
Thanks for your thoughts
It may give you strange stray reflections from an irregular chip. That would be my concern
Lorenzo Siciliano:
Not at all. Mine is in the same shape as yours.
Ciao
Lorenzo
No issues neither here with a chipped prism
andrea tasselli · Mar 31, 2026, 10:07 PM
Lorenzo Siciliano:
Not at all. Mine is in the same shape as yours.
Ciao
Lorenzo
Ciao Lorenzo,
Voi dire che anche il tuo prisma e' scheggiato?
Sì Andrea. In un angolino vicino al suo sostegno. Dimensioni della scheggiatura più o meno come la tua.
Onestamente, mai notato nulla di anomalo durante la guida. È solo un “disturbo” estetico, ma non incide sulla funzionalità.
Ciao
Lorenzo
Grazie Lorenzo.
With so many variables that can wrong, I would still consider eliminating this possible issue, no matter how miniscule it might be.
Someone earlier mentioned it might cause some unwanted internal reflections…
If it was not advertised as having a little chip, or showing minor damage, you should consider asking for a partial refund or consider returning it.
In all likelihood it will probably guide ok, and you will not notice anything wrong, but with all the issues we face with OAg and imaging, like not finding a star, reflections in your flats , or stray light causing reflections in your images, you will always think and wonder….is it because of the 2mm chip on my OAG’s prism?
Dont know if this would be helpful but, my own (askar) oag prism has some chipped areas across it and cracks inside it, and I still guide very well and can do 10+ minute exposures on an AVX
Best guiding is usually around 0.40” total rms. 1.86”/px main cam pixel scale.