Coma Correction

[fwm891]

I'm a recent convert to visual astronomy but like imaging the fov suffers (f5 16 inch) at the edges and I think a coma corrector is needed. Just going onto FLO's site there are a number there that are purely photographic so easily discounted but of the others I'm unsure as to which is better than another FOR VISUAL USE.

My scope is a home built 16 inch f5 newtonian with Nichol mirrors. I have all Tele Vue ep's (Panoptic: 15, 19, 24 and 35mm) and a Delite 13mm.

My skies are a reasonable Bortle 4 even if the amount of sky is restricted due to buildings and trees.

Looking for recommendations to look at (or avoid) please.

Clear skies

Francis

[Piero]

The TeleVue paracorr2 is the best one out there. I wouldn't use my dob without it! As you already use TV eyepieces, choosing a TV coma corrector would make sense. Here are the specs with eyepiece settings: https://www.televue.com/pdf/literature/Pacacorr%20Type-2%20Instructions.pdf

The ES version might also work okay, but it requires much more inward travel (if I remember correctly, this is 35mm).

Given the design of the Baader, I would consider this for imaging applications, but not for visual.

Edited October 31, 2021 by Piero

[jetstream]

Another vote for the Televue PCII and you have the perfect eyepieces for it. It is very easy to use in the dark, no need to look at the settings except for the initial one.

Edited October 31, 2021 by jetstream

[fwm891]

Many thanks. My feelings were/are the same. Time to start saving… (or Christmas isn’t that far away)

[Piero]

I believe you are already aware that the TV PC2 also has a minor barlow effect (1.15x), so your f/5 telescope will become f/5.75 when used with the PC2. This barlow effect was added in order to minimise the additional inward travel usually required by coma correctors.

Personally, I am actually happy about that minor barlow effect, but those observers interested in observing at very low power (e.g. IFN, etc) do not like it much. 

Anyway, just a comment.

[Paz]

+1 for the TV Paracorr 2. I've used that with my f4.6 reflector for years and don't observe without it.

There is also the feathertouch sips which I have heard good things about but I have not used one of those myself so can't comment on those from experience.

[estwing]

The sips is fantastic in the feather light focuser but I personally use the paracorr 2...both highly recommended 

[fwm891]

The TV Paracorr II seems to be the tool needed. I think at present I’m going to get more visual experience with both my two visual scopes (16 inch dob and 4 inch frac), possibly borrow a coma corrector to make sure I do actually need one.

Thanks all for your input on this, great help and needed guidance.

Francis

 

[Captain Scarlet]

14 hours ago, Paz said:

+1 for the TV Paracorr 2. I've used that with my f4.6 reflector for years and don't observe without it.

There is also the feathertouch sips which I have heard good things about but I have not used one of those myself so can't comment on those from experience.

Another satisfied pc2 user here.

Revthe Feathertouch sips, it is simply a pc2 integrated into their focuser.