Re: f-stop question

"goodnigh" <goodnigh1@xxxxxxxxxxxxxx> wrote in
news:hshii.3073$Od7.0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx:


"Llanzlan Klazmon the 15th" <Klazmon@xxxxxxxxxxxxxxxx> wrote in message
news:Xns99619AA737883Klazmonllurdiaxorbgo@xxxxxxxxxxxxxx
"goodnigh" <goodnigh1@xxxxxxxxxxxxxx> wrote in news:DRYhi.3032$tj6.44
@newsread4.news.pas.earthlink.net:

Will be buying a 10 inch 1200mm f4.5 Dob.
After experimenting with inexpensive GoTo scopes,
I have decided to "GoTo" basic star hopping.
Somewhere I read there is an issue with fast scopes.
Just can't remember what they are.

mike

In the case of a newtonian like this a faster f ratio implies more off
axis
coma and greater sensitivity to accurate collimation. Exit pupil might
be a
problem if you plan to use 30mm or greater fl eyepieces.

Klazmon

Ok, Thanks. There was something about fast scopes.
You can see more, but it won't be as clear as my 90x1000mm
Vixen refractor at f11.
Not a huge problem for casual observing.

mike


Remember that coma is only an issue off axis and a 10" scope will show a
heap more than a 3.5". If the coma bothers you, you can buy a Televue
Paracorr coma corrector although they are fairly pricey.





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Relevant Pages

  • Re: f-stop question
    ... After experimenting with inexpensive GoTo scopes, ... I have decided to "GoTo" basic star hopping. ... Somewhere I read there is an issue with fast scopes. ...
    (sci.astro.amateur)
  • Re: f-stop question
    ... After experimenting with inexpensive GoTo scopes, ... I have decided to "GoTo" basic star hopping. ... Somewhere I read there is an issue with fast scopes. ...
    (sci.astro.amateur)