tmb planetary with standard barlow

[Buzz Lightyear]

Hi,

If I had for example an 8mm TMB EP and I wanted to double its mag to x250 with the standard barlow that was shipped with my 200p scope, would the image quality be bad, even if it was well within the limits of the scope.

Or would it be best to get a 4mm EP?

cheers.

Paul.

[John]

250x maybe well within the theoretical limits of the scope but it's often right at the edge of the viewing conditions will allow which is the real limiting factor 95% of the time.

To preserve image quality you would need to get a decent quality barlow lens - the TAL ones are generally good for their price (£35 or so) but the Celestron Ultima 2x / Orion Shorty Plus 2x or Tele Vue 2x are better, but more £'s of course. You may find investing in a 4mm TMB Planetary eyepiece the most cost effective approach and will probably offer slightly better performance.

Edit: To answer your question on the barlow supplied with your scope - I don't think it's going to give you decent image quality to be honest.

[Buzz Lightyear]

thanks john,

thats what i expected, i have the feeling my scope will start to lose quality past x200, should i go for a maximum mag of x200 with a 5mm instead of a 4.

i am trying to fill the gap that i have in my ep range, this is what i have.

x32

x43 barlow off my hyperion

x77

x108 fine tuning ring

x166

i am mainly interested in DS objects and not too bothered about planets.

Do i need another eye piece? I may just get a UHC filter instead to see the nebulas better, what do you think?

Paul.