Erm...Flextube 350P is f/4.5...Coma corrector required perhaps?

[emadmoussa]

I think at this focal ratio coma will start to show a lot unless the eyepiece is super corrected. Even with high end EPS I expect to see a degree of coma. I'm just assuming considering an f/4.5 scope is more on the fast side. I stand corrected.

I'm starting to think if I'm taking the plunge for a similar scope, a CC would be a sound investment?! Which brings me to the question on the effectiveness of the Baader multi-purpose corrector...

[Mike73]

I have a f/4.5.

Coma never bothered me with my 26mm Nagler, it was there but for me it wasnt too bad so I sold the Paracorr (which I hated anyway).

Unfortunately I had to sell the Nagler but a few months later bought a 28mm 68˚ ES to replace it which wasnt so good at correcting coma so I bought a Baader mk3 CC which has done an amazing job at cleaning the views up in the ES.

The Baader is great but its really only practical to use with one EP.

For me this isnt a problem as I go from that 28mm 68˚ down to a 17.3mm Delos, If you like 82˚ or 100˚ then I think its best to get a Paracorr.

[John]

Just a point of clarity. Eyepieces don't generally produce or correct coma, regardless of their quality. I know I sound like a stuck record on this but it can lead to some confusing threads !

From the many threads on this subject recently it seems as if coma and astigmatism (you can blame eyepieces for the latter one) bothers some people more than others.

Coma is going to be there though, in an F/4.5 newtonian.

[Daniel-K]

i dont use a CC in mine, i noticed it more in the 28MM Maxvision but alot less in the 18MM 82 ES. im yet to try out my televues but i suspect they will show it less than my other EP's i had. i dont mind it right on the edge of the FOV

[Kropster]

It will make a big difference for AP.

Not sure for visual as presumably, what you are observing is central in the FOV where coma isn't a problem.

[emadmoussa]

Yep, most my eyepieces are ES 100-deg...so you're saying the Baader CC won't be effective with such EPs?

[John]

i dont use a CC in mine, i noticed it more in the 28MM Maxvision but alot less in the 18MM 82 ES. im yet to try out my televues but i suspect they will show it less than my other EP's i had. i dont mind it right on the edge of the FOV

The TV's may actually show more coma because they lack the astigmatism that can mask it. 

[emadmoussa]

Was about to say..you beat me to it, John.

[AlexB67]

i dont use a CC in mine, i noticed it more in the 28MM Maxvision but alot less in the 18MM 82 ES. im yet to try out my televues but i suspect they will show it less than my other EP's i had. i dont mind it right on the edge of the FOV

As John said. TV or not, it makes no diff, you may find that an ES will show a bit more astigmatism perhaps and mask coma a bit more.  In the end of the day coma is the same in a X degree eyepiece of Y focal length from any manufacturer,

Coma as such can exist in eyepieces too, but it is eliminated by design and easy to control, therefore we don't talk about coma caused by eyepieces and purely by the mirror, and as I was typing John beat me to it. dho

as for the Baader CC, it really gets some positive  reviews on the whole, don't confuse it with the older Baader CC which suffered a bit more form speherical aberration after correction and less suitable for visual use.

From all that I read on them for visual use if it was a toss up on a budget I would go for this one or the GSO CC.  if you want to splash out get the paracorr, or perhaps the ES, but I have not heard a huge amount about  it, no doubt it would work well with ES eyepieces in mind perhaps. 

In any case don't forget the few extra you need like extension rings etc.  see attachment for several configs with the baader or the GSO the same applies.  The baader is somewhat a bit more hassle free as it supposedly work in pretty much all focusers, the paracorr and GSO need to SW focuser modded for example as they'll not sink deep enough.  The baader is also very light, no effective focal ratio change, the paracorr will push it up by 1.15 and the GSO by 1.1 if that bothers you and they are quite a bit heavier 

mpcc_e.pdf

[AlexB67]

I should clarify about hassle free comment, the paracorr is least hassle free with eyepieces with the tunable top to configure, I meant with regard to fitting in most focusers the baader has some advantages without having to fear to mod the focuser or replace it for that matter.  Plenty threads around on that anyway on CN as well. 

[RikM]

I've tried the Baader MPCC type II with my ES28/68° and it was really quite nice but I only have one MPCC and use it for AP where it is essential. I may get another at some point for visual use but at f/4.7 it doesn't bother me that much, so it's at the back of the queue.

[swamp thing]

I have the SIPS focuser in my larger scope. This puts the CC before the focuser once adjusted never needs to be touched again. It corrects coma in my TV Naglers but it can't correct astigmatism in cheaper designs. For me this is the way forward with coma correction and focuser design.

[Moonshane]

you don't need a CC on any newt unless imaging. if you want to make the best of a fast scope (<f5) then you can do this with good collimation, good eyepieces and a good CC but the views of objects will still be what the aperture brings. if coma in the field (increasing the wider the field/lower the mag. the faster the scope) bothers you then a CC will sort it out. if not then it's not essential. you'll only really know when you try the scope. would I recommend one? yes, most certainly with scopes <f5. which one? personally a paracorr is the best I've used but the GSO one is very good for the price. it's about as hard to change the settings on a paracorr as it is to change an eyepiece.