will i need a coma corrector

[Earl]

i have picked up a 10 inch dob, my son and me can set it up, i would of liked a 12 but im not strong enough.... i digress.

i have a 35mm 2" panoptic i plan to use, will coma be an issue?

[YKSE]

Maybe it's best that you have go without CC first to find out? Coma sensitivity is kind of personal as I understand.

My guess is though that you're like to need one, especially if your 10" is a F4.7 SkyWatcher alike, and 35mm EP might turn out to give too large exit pupil, resulting in washed out sky.

[ronin]

I suspect you will if it bothers you much.

As we tend to put things in the centre and if the effect that will be primarily at the edge doesn't bother you (or son) then leave it.

For visual it is one of those things like CA, it drives some people to distraction and others wonder what all the fuss is about.

When you get the scope check it out for collimation and then use it a few times.

Likely coma will be present but how it impacts on you is really the question.

If after the first couple of uses you want a coma corrector then look around for one.

I suppose like most items there are costly and not so costly ones.

[Moonshane]

need no but will the view be better with? Yes.

in truth I'd suck it and see and you may well be quite happy without.

[Dude_with_the_tube]

i had a skywatcher f4.8 dob before upgraded to 14" and coma didnt bother me on that one.again its to each individual.I kinda doubt that with 68 deg Pan coma will be a real issue(coma will be there but nothing drastic).It is more evident in UWA ranges in likes of 82 or 100 deg.Give one session a go with your 35mm Pan and see how it looks.If you do have a friend with a coma corrector,see if you could borrow it for a comparison.

[RikM]

I don't use one with my Skyliner 10". My widest field eyepiece is a 28mm 68° though shows quite a bit less than your 35mm Pan. As above, I would say give it a try and see how you feel. The view will be better with a CC, but whether it is worth the outlay / inconvenience is going to be down to how you feel about the view.

[Earl]

ok, ill wait and see

[Tinker1947]

I never needed one with my 10" Skywatcher P-DS when viewing, if your going to plug a camera in then it will need one......

[AndyWB]

Ditto what Rik said. I find my 28mm 68 degree eyepiece does actually show some coma - just it's right at the edge and doesn't bother me much. Others, I'm sure, would be driven nuts by it.

[faulksy]

it never bothered me much in my 4.6fl , then i fitted the sips(coma corrector) and couldnt believe the difference, but i say dont use a coma corrector or you will regret it, bit like if you look through a ethos you will have to get one

[estwing]

Below F4.8 it creeps in...atF3.9 it's there but not to the point that it's unusable...just why have a mirror that fast and not correct it?

[alan potts]

Personally If I had a Newt, which I don't BTW, and went to the expense of Televues eyepieces for sharp to the edge performance, I would want the FOV to be sharp so would buy one.

Alan

[Mr Spock]

Try it first. I had a 10" f4.7 and the 22mm Nagler definitely needed a coma corrector, for me anyway. Coma annoyance in Newts is a personal thing, much like some people who can tollerate CA in refractors.

[John]

it never bothered me much in my 4.6fl , then i fitted the sips(coma corrector) and couldnt believe the difference, but i say dont use a coma corrector or you will regret it, bit like if you look through a ethos you will have to get one

Thats how it is with a number of these issues, coma, astigmatism, chromatic aberration, etc, etc. They are not necessarily intrusive until you try some kit that does not show them and then, somehow, they get on your nerves a bit more   

[swamp thing]

it never bothered me much in my 4.6fl , then i fitted the sips(coma corrector) and couldnt believe the difference, but i say dont use a coma corrector or you will regret it, bit like if you look through a ethos you will have to get one

What utter rubbish. I've looked through many an ethos and I'm not going to buy one.

[astronymonkey]

Steve may be pinocio ..... but thanks to my glasses I binned any thoughts of wanting an ethos when I couldnt see the full field due to the eye relief. This hasnt stopped me buying delos and naglers though !

As for coma, I dont use a corrector at f4.5, but im not going to try one either ..... just in case I get bitten by the bug.

[faulksy]

What utter rubbish. I've looked through many an ethos and I'm not going to buy one.

i could tell you was lying because your lips were moving

[swamp thing]

i could tell you was lying because your lips were moving

mieow! Saucer of milk with that

[Don Pensack]

Well, the 35 Panoptic has a 38.7mm field stop and a slightly curved focal plane.

The coma-free zone in the center of the field in an f/5 dob is 2.22-2.75mm (depending on whose standard is used), so the vast majority of the field will have comatic stars.

Add to that the slight defocusing of star images at the edge (due to the slight field curvature), and you may well see coma (even slightly exaggerated by defocus) in the outer field.

The same combination of eyepiece and a 12.5" f/5 dob was what convinced me to get a coma corrector many years ago.

You can mitigate the defocus and reduce the impact of coma by focusing about half-way from center to edge.  That works really well with the 35 Pan and should reduce the visibility of coma a bit.

As others have recommended, I'd try it first without a coma corrector.  But don't be surprised if it leads you to want a coma corrector.

[russ.will]

You can mitigate the defocus and reduce the impact of coma by focusing about half-way from center to edge.  That works really well with the 35 Pan and should reduce the visibility of coma a bit.

As others have recommended, I'd try it first without a coma corrector.  But don't be surprised if it leads you to want a coma corrector.

The half-way-house focus method is what I do, being as I stupidly sold my CC a while ago. That and generally try and stick to using my 24mm SWA or shorter, after using the longer FL EPs as finders.

At the time, I'd gone from a 305mm F4.9 SW Dob, back to a 200mm F6 OOUK Newt on EQ which, for the most part, rendered the use of the CC moot. Then ES delivered the UL Dobs (we're not quite so blessed - on this side of the pond - with cheap portable designs) and I had to admit to myself, I couldn't live without the extra aperture. 1/10th wave mirrors are nice, but 8" is still only 8". For what I got for the CC, I now realize it was on of those 'buy once and just keep it for when you next need it' purchases.

As such, I'd say to the OP that yes, of course you can live without a CC, but once you have one, it's not likely that you would want to.

Russell