Ad Astra Observatory

Art Morton wrote:
> You hit the cruxes of the matter, the secondary size. The other thing
> I remember battling was f/ and being able to see the secondary when
> focusing at low f/s.
>
> Sounds to me you have that all work out, and with a little more
> testing you will have it solved.

Either solved, or unsolvable with a workaround. Either way is OK with
me. I like shooting flats with the lightbox. Rain, rain, go away. Or not. (:

J
> On Feb 24, 2009, at 11:24 PM, Jimbo S. Harris wrote:
>
>>
>> On Feb 24, 2009, at 4:16 PM, Art Morton wrote:
>>
>>

>>> Refectories and Maks are notorious for hot spots as the f/ goes down
>>> to 3 or so…..
>>
>> My particular Newt came with a 2.1” secondary (or was it .1.8”?) and
>> I replaced it with a larger secondary (the size usually found in 12”

>> scopes), which was the size that NEWT suggested would be large enough
>> to evenly illuminate a field at least 30mm across.
>>
>> So I have it more or less narrowed down to 3 culprits:
>> – The focuser drawtube (2” is sufficient, but a longer drawtube means
>> that the light cone is chopped to 2” further from the focal plane…)

>> – The MPCC (my most likely culprit, but my biggest fear)
>> – the T-ring (only 1.45” in diameter, but very close (within 2”) of
>> the focal plane, so possible but unlikely)