Skywatcher dobs and coma correctors

[strongmanmike]

I've just ordered a 12" F4.9 skywatcher flex tube GOTO dob ..yes a miracle :eyepop: I haven't had a usable visual scope since 2006

The scope will be purely for casual visual observations and I was wondering how necessary a coma corrector is with this model and if you think it is necessary which one do people use or recommend?

Cheers

Mike

[raymo]

Everyone has his or her own opinion on this matter. For visual, coma
has never worried me. Just try it and see. Save you a fair bit of money
if it doesn't bother you.
raymo

[Allan_L]

Hi Mike,
Welcome back from the Dark Side :welcome:
I have the same scope, good choice!
The answer, as Raymo pointed out, depends...

Firstly, with a tracking DOB, it is not generally noticeable.
(with a non tracking DOB, you tend to put your object into one side of the eyepiece, and watch it drift across the field of view. So changes due to coma may be obvious on the outer edges).

Also, coma is more noticeable with the more widefield eyepieces.

TeleVue says:


I have a TeleVue Paracorr, but it does add a bit of weight (especially with an Ethos eyepiece) and I don't always use it.

Some people have looked through my scope (without Paracorr) and said they could not detect any coma (eg astropolak) others have said it makes a noticeable difference (eg Rick Petrie).

Why don't you duck up to Bretti this week and have a look through mine at a very Dark site. Or as Raymo says, just try it first.

[Camelopardalis]

All I can say is...don't go looking for it :lol: :lol:

It only leads to the expense of the coma corrector and THEN the expense of all the wide AFOV eyepieces to justify the corrector ;)

[MattT]

:lol:
All I can say is I see coma big time and being a refratorholic it bothers me so much with 68º eyepieces, I had to get a CC. Lovely viewing with a CC, not worth looking without a CC. The ESHR coma corrector is a permanent fixture in my 10" f4.8 Newt...only comes out when the bino's go in.
My 2 bobs worth
Matt

[Camelopardalis]

Yeah my issue was with a C8...apparently the coma is similar to a f/5 newt. Once I'd seen it, I couldn't "unsee" it and I like the wider AFOV experiences. Ended up with a Edge HD model :D

[rustigsmed]

Great scope :thumbsup:

I wouldn't say it's necessary especially with goto, but it is definitely way better with one especially when enjoying a wide vista. I have the MPCC III which has done a nice job.

I went digging for a shot I had taken on the [same] goto dobbie before I got my coma corrector, https://www.flickr.com/photos/80336656@N07/8260374701/in/photostream/lightbox/
you get an idea on the top right and left corners, it may have a slight crop but not much.

Cheers,

Rusty

[strongmanmike]

Hey thanks so much guys :thumbsup:

I think I will wait and evaluate it, I certainly get the benifit of a tracking dob now as it will keep the object in the centre of the view, I can see how drifting from one side of the FOV to the other would make any coma annoyingly more obvious.

Mike