Comma Corrector for Skywatcher 16" Dobsonian

[bluesilver]

Hi,  I have a Skywatcher 16" Dobsonian.

According to the specs,  it tells me it is around the f5  some specs say f4.8,  so just going with f5

Funny enough,  i have just only been hearing about comma correctors for Newtonians as i am in the process of looking at a Skywatcher 300/150 Black Diamond.

Is it worth while looking at getting a coma corrector for the 16" Dobsonian?

It is mainly always used for visual use.

Will the comma corrector make much of a visual difference for star clusters, nebula e.t.c,  and will it also make any difference when viewing planets?

I was possibly looking at the Skywatcher f5 comma corrector if it is worth while look into.

Any advice would be appreciated.

Cheers.

 

 

[AstroKeith]

At f5 it's marginal. Big question - have you noticed any coma?

If not save your money.

Some eyepieces (ie 2" wide AFOV) will be more susceptible. 

[John]

If it is the Skywatcher Skyliner 16 inch (the 400P model) then it has a focal length of 1800mm and the focal ratio is F/4.4.

If you are using wide angle eyepieces with the scope, coma, will be an issue in the outer parts of the field of view so a coma corrector would make sense in such a scope.

Planets are generally observed in the central part of the field of view so coma is probably not going to be an issue there. For star clusters and other more extended targets coma is likely to be seen and can be distracting. Some people are more tolerant of it than others.

 

 

[Louis D]

I use a GSO CC in my GSO 150mm f/5 Newt.  It gets the job done with wide field eyepieces.  For Orthos and Plossls, the difference might not matter much to most observers.  Because it imparts some spherical aberration on axis, I remove it for high power viewing of planets to get the sharpest image possible.

[Guest]

I second the gso coma corrector as well.  I use it in my 10 inch f5 dob.  I have not had it in my 16 inch yet, but i will be trying it at some point.  Worst case you try it and send it back. 

[Mr Spock]

In my 12" f5, when I use the 30mm UFF, I can't see any coma at all.

[bluesilver]

Appreciate the replies,

It is the collapsible version of the Skywatcher Dobsonian,  and just looking back at the place where i originally got it from,  it is indeed listed as a f4.4

so my mistake there.

 

I will have to look into this comma a bit more,  I am thinking i may not possibly have any, but then again,  i only just recently heard about comma correctors and haven't noticed any weird shaped stars,  but as mentioned i haven't really been looking for it either.

I am mainly just using the standard 20mm eye piece that came with it and occasionally swap it out for e televue 10mm Delos

I will have to take another closer look next time i get it back out.

 

 

[John]

14 hours ago, bluesilver said:

Appreciate the replies,

It is the collapsible version of the Skywatcher Dobsonian,  and just looking back at the place where i originally got it from,  it is indeed listed as a f4.4

so my mistake there.

 

I will have to look into this comma a bit more,  I am thinking i may not possibly have any, but then again,  i only just recently heard about comma correctors and haven't noticed any weird shaped stars,  but as mentioned i haven't really been looking for it either.

I am mainly just using the standard 20mm eye piece that came with it and occasionally swap it out for e televue 10mm Delos

I will have to take another closer look next time i get it back out.

 

 

At F/4.4 coma will be there but may not be too noticeable depending on what eyepieces you are using and how hard you look for it. It does not affect the central part of the field of view. Toward the edges of the field you might notice stars take on a shape like small comets with their "tails" pointing away from the centre of the field of view. On the other hand, if you are not noticing it then it's probably not an issue that bothers you.

 

 

Edited March 11, 2023 by John