Posts Made By: Daniel Soderstrom

I'm just ordering all the bibs and bobs I need to do Astrophotography with my Sky 90. I've ordered the field flatener, adaptors etc. I have some questions;

1. I've been told I need a ronchi or something to focus? Where do I get one suitable?
2. Will I have a nice round circle in the middle of the 645 film or will it cover the whole film?
3. I have rolls of E100GX in the fridge. Will that be ok?
4. I do not have a guide scope at the moment, but the p2z has a periodic error 8 (+-4). This review ;

http://www.astrosurf.com/carreira/comentario_tak_p2z_eng.html

here suggests I could do exposures unguided for a few minutes. Will this be enough at f/4.5 to take a photo? How long do I need the exposures to be? I realise if you get into the magnitude counting game its hours.

Daniel.

Well, its a funny comparison, since the Tak is part of a system. Your supposed to use an extender-Q with it for visual use and a flattener for astrophotography. It gives you a "two scopes in one" type of package.

Sky 90 + Extender Q = f/7 (like your WO)
Sky 90 + Flattener = f/4.5

or with a small loss in quality you can use it at f/5.6.

I'm not sure the value of the comparison of the Sky 90 to your WO at higher powers without the extender Q. It wasn't intended to be used that way.

Daniel.

PS. If there is anyone in Perth Australia who'd like to compare the WO (or Skywatcher) to the Sky 90 w/Extender-Q I'd love to.