Asa 3" 0.73x corrector

[giocasi]

Goodevening.

I'm italian guy, i buoght a 3" 0.73x corrector used from a austrian guy. while I was taking the measurements to make the fittings I realized that they were different from the specifications.  I have attached photos of the corrector and the pdf with the specifications of the corrector ... even the real length of the corrector is different!  have different models been made?  Thanks for your help.  Giovanni.Corr_3Zoll_Reducer.pdf

[giocasi]

as you can see, the measure of diameter on the pdf is 79.5mm while in reality it is 81mm

[MarkS]

I have an ASA 0.73 Reducer, and its dimensions are exactly as per the ASA drawing. Are you sure what you have is an ASA reducer?

Mark

[Christophe]

Good evening,

I have recently bought also an ASA 3" 0.73 reducer from an astronomer and I have exactly the same observation than Giovanni. I have measured external diameters of 81 mm instead of 79.5mm and 76mm instead of 76.2mm. I have also measured a total length of 73mm instead of 69.53mm. Have you been able to solve your problem.

Even if the dimensions are slightly different, my main question is : can I trust with the backfocus values given by ASA ? Moreover just to be sure, for the values of backfocus given by ASA in the table, the f-ratio is the initial ratio of the telescope or it takes into account the 0.73x reducer ?

Thank you very much for your help.