Re: (IAAC) f/6.3 focal reducer (was eyepiece suggestions)


With the 12" LX200 f/10 and the previously mentioned configuration (f/6.3 focal reducer & 40mm Super Wide) I have had no deterioration at the edges of the field. However, with my 10" LX200 f/6.3 and the f/6.3 focal reducer (which makes for an insanely fast f/4 SCT) astigmatic deterioration is quite apparent at the edges of the image. A couple of years back I had owned a 16" f/4.5 Newtonian, and I did experience comatic distortion when using a 40mm Super Wide. At the time I didn't experiment too much with different eyepieces, but I don't seem to remember getting any noticeable astigmatism. I found that a 14mm Ultra Wide gave me the best resolution for deep sky observing and the combination of a 40mm Super Plossl & a Telenegative Barlow Lens worked superbly for planetary observing. My experience with Newtonians is limited, but I'm guessing that your experiencing coma due to the fast focal ratio of your Newtonian in combination with the Super Wide.


Dave Mitsky wrote:


How is the edge of field performance of the 40mm Meade SWA when the f/6.3 focal reducer is in use?

I have a 32mm SWA and I notice astigmatism with an f/6.5 Newtonian.

Dave Mitsky

Matthew Wilder wrote:

If you are looking to do any deepsky observing or in particular any astrophotography, your next consideration for purchase may be the f/6.3 focal reducer (the 12" is only offered in f/10) for an indescribably detailed image and short exposure times. Try one out if you can, and you'll see just how much this reducer can bring out the potential and optical quality of this instrument.

I don't know which manufacturer's eyepieces you are currently considering, but I would suggest both the wide field and the high power eyepieces if at all possible (for versatility). If that is not possible, consider purchasing the 40mm Meade Super Wide 2" eyepiece and use it in conjunction with the f/6.3 for a field of view that is 60% greater than the standard f/10 and more than twice as bright.