coma corrector

[seven_legs]

Hi all

I use a skywatcher 14" dob and wonder if a coma corrector for visual use is worth having?

Tony

[ronin]

I suspect the answer is yes IF you want flatter/rounder stars over the full view of your eyepieces.

Then comes the cost - is the benefit going to be worthwhile. Seems there is a fair spread of costs hopefully someone will appear and say that a particular one is beneficial and not too costly.

The aspect about the full view is that I bought an eyepiece (40mm plossl) for a wide field, I literally just wanted WIDE, stars could be any shape, I didn't care, just wanted wide. It was for getting the first alignment star in view on a small goto Mak. I didn't how good it was just that it was somewhere.

[Tinker1947]

I have a CC but its purly for Imagine the 300P does seem to suffer from and deformed star, but that could be my old eye's.....

[John]

If you intend to use good quality wide field eyepieces then I think you will really appreciate a coma corrector. You probably won't be getting good value from expensive, well corrected eyepieces in an F/4.5 newtonian if you don't use a coma corrector. 

[Moonshane]

I see coma correctors in fast newts as in the same bracket as a decent dual speed focuser, good finder or star map. They all enhance your experience with all objects and therefore give better value for money. You can get by without them but why do so if you can afford one. I use a type one Televue paracorr which cost less than some of my eyepieces so to me it's well worth it

[Paul73]

My scope is on the brink at f4.7. I have a Paracorr which cleans up the CA nicely. But, I don't find it to be that intrusive so don't use it that often. They do cut down the FOV a bit. I would give it a try without and then decide to buy a good one if you feel the need.

Paul

[estwing]

I see coma correctors in fast newts as in the same bracket as a decent dual speed focuser, good finder or star map. They all enhance your experience with all objects and therefore give better value for money. You can get by without them but why do so if you can afford one. I use a type one Televue paracorr which cost less than some of my eyepieces so to me it's well worth it

+1

[mdstuart]

You do lose a small amount of light throughput with them for very faint objects..

[jetstream]

They also add some form of distortion or aberration in small amounts, but most see the benefits outweigh the cons I think. Lots of cash these things....

[Charic]

.......while were talking about correctors, baadar Planetarium state their MPCC (Multi Purpose Coma Corrector) does not change the focal ratio of the telescope in any way!  Can I therefore assume that other coma correctors may have an effect on the focal ratio, and should this be something else to consider, with possible  side effects?

Often, it seems whatever you throw at your telescope in what appears to be a positive way, can result in some other negative issue, not known prior to the upgrade?

Example: The Barlow effect on focal length increases the magnification of the eyepiece inserted by the factor of the Barlow, this also effects the focal ratio of the said scope. A 2x Barlow on my scope equates to My Skyliner becoming an F-2400 f/12 when the Barlow is inserted, not the same scope! But prior to my purchasing a Barlow, I did not know it would change the focal ratio, just the fact that I could double my eyepiece collection, without really knowing why back then.

So, does fitting a coma corrector, apart from correcting the field of view, change any other parameters, that would be of interest to the end user.

Finally to Tony, If coma does not effect or bother you for visual use, then no, not worth having or the expense to upgrade, but If you see coma, and it effects you, then by all means do something about it. I'm sure I can see some disturbance, if I look  at the extreme edges in my 8" system, but the edges are not so important to me for visual use, as  I just keep centring the scope,  I also blame my  old eyes for any imperfections?

[seven_legs]

Thanks all

Some good info