Re: [ATM] Loveday alternative to Cassegrain

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Donald Good wrote:

>
>> How does this change the original complaint about the Loveday, i.e.:
>> the ratio of the light diameter at the second pass
>> into/to/upto the secondary to the secondary is roughly
>> limited by the ratio of the secondary shadow on the primary
>> to the primary?
>>
> Do you mean diameters (D) for hole (h), primary (p), and secondary (s) are
> related by:
> Dh/Ds ~= Ds/Dp
> ??
>
Roughly, yes:

    Dh/Ds < Ds/Dp

was the requirement.

The umbral shadow of the secondary must cover the hole or light would go
directly from the middle'ish part of the primary into the hole and hit
the sensor.  If the cone of light from the primary matches the secondary,
the part that matches the shadow of the secondary was approximated as
proportional ( (Ds/Dp)*Ds is the size of the shadow )


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