Coma corrector recommendation

[Anthony1979]

Can anyone recommend a good coma corrector for my skywatcher 150p please 

[bottletopburly]

Baader cc  mk3 use on a sw200pds works a treat I’m sure it’s compaible with the 150p others will confirm 

https://www.firstlightoptics.com/coma-correctors/baader-mpcc.html

Edited May 22, 2020 by bottletopburly

[Tommohawk]

16 hours ago, Anthony1979 said:

Can anyone recommend a good coma corrector for my skywatcher 150p please 

There's a great assessment of coma correctors here.

It doesn't include all types/makes though, and doesnt rate the basic Skywatcher 0.9x CC which is a shame because it seems to work really well with F5 scopes - it's what I use and I cant really see any issues with it.  That said it I tried it with an F4 scope and it seemed very poor - surprisingly so given the good performance at F5. It connects nicely via an M48 thread.

Be aware that CCs vary in terms of image size. The SW offering is 0.9x so gives you an F4.5 with increased FOV, but some others are 1x or 1.1x. 

For £119 I'd say its a good buy, but if you're thinking of going to F4 you may need something else.

BTW I'm just posted an image done with this CC here. not the best and slightly cropped but gives an idea.

[Paul M]

57 minutes ago, Tommohawk said:

It doesn't include all types/makes though, and doesnt rate the basic Skywatcher 0.9x CC which is a shame because it seems to work really well with F5 scopes - it's what I use and I cant really see any issues with it

I have one sat in a shopping cart at FLO waiting for me to pull the trigger (still weighing up the other items), so I am pleased to read your assessment and look at your linked image. Thanks.

 

[Starflyer]

I had both the Baader MK3 and the Skywatcher 0.9x CC, both gave good star shapes with my f/4.8 OO newt, but I gave up on the Skywatcher due to pretty bad reflections.

[Adam J]

If you want the best get the Explore Scientific Coma Corrector. If you want one that just gets it done without been too expensive the Baader. But the ES one is much better. 

Adam 

[alacant]

On 22/05/2020 at 02:54, Anthony1979 said:

good coma corrector

Hands on...

OK : good : best

Baader : SW 0.9 : GPU

Cheers

 

[Adam J]

16 minutes ago, alacant said:

Hands on...

OK : good : best

Baader : SW 0.9 : GPU

Cheers

 

Yeah the GPU is a step up too but for my money the ES CC is better.

[rnobleeddy]

Assuming I've understood correctly and a 0.9x coma corrector causes problems with the focus tube on the 130PDS, is that a reason to get a 1x coma (such as Baader Mark-III MPCC or the GPU) for that telescope?

[Tommohawk]

11 minutes ago, rnobleeddy said:

Assuming I've understood correctly and a 0.9x coma corrector causes problems with the focus tube on the 130PDS, is that a reason to get a 1x coma (such as Baader Mark-III MPCC or the GPU) for that telescope?

Not sure what problem youre referring to. It maybe that because its 0.9x it has to focus further inwards, and there may not be enough inward travel. You  might be able to fix this by moving the primary further up the tube with the standard collimation adjustment, or by modifying (lenghthening) the primary collimation screws. 

The other potential problem is that with smaller newtonians the coma corrector protudes more into the light path; you can minimise this be using a shorter coma corrector, but in my experience the shorter coma correctors tend to be more compromised in terms of optical design.

not sure that helps much though!

[alacant]

1 hour ago, rnobleeddy said:

 0.9x coma corrector causes problems with the focus tube on the 130PDS

With a dslr attached, at focus with coma corrector or not, the focus tube will protrude into the light path and so cause irregularly shaped stars. 

The easiest remedy is to cut the end of the focus tube. a 20 minute job with a hacksaw.

HTH

[Anthony1979]

6 minutes ago, alacant said:

With a dslr attached, at focus with coma corrector or not, the focus tube will protrude into the light path and so cause irregularly shaped stars. 

The easiest remedy is to cut the end of the focus tube. a 20 minute job with a hacksaw.

HTH

Isnt the pds versions made for imaging so you dont have to cut the tube

[carastro]

Quote

Isnt the pds versions made for imaging so you dont have to cut the tube

Correct, but they are talking about the focusser tube, not the main tube itself.  I had a 130PDS and had to cut the focusser tube because when in focus the part of the focusser inside the tube protruded into the light path too much and took a bite out of my stars.

Carole 

[Anthony1979]

29 minutes ago, carastro said:

Correct, but they are talking about the focusser tube, not the main tube itself.  I had a 130PDS and had to cut the focusser tube because when in focus the part of the focusser inside the tube protruded into the light path too much and took a bite out of my stars.

Carole 

Thats what i mean... Arnt they designed so you dont have to do this.... Ive got a 130pds coming on monday and this is the last thing i wanted to do

[Dan13]

1 minute ago, Anthony1979 said:

Thats what i mean... Arnt they designed so you dont have to do this.... Ive got a 130pds coming on monday and this is the last thing i wanted to do

if you get the non reducing CC for the 130pds theres no cutting needed. this one here https://www.rothervalleyoptics.co.uk/skywatcher-2-coma-corrector.html

[carastro]

Might depend on your camera and your coma corrector. 

this was the shape of my defocussed star before I chopped the end off the focusser.

[Anthony1979]

2 minutes ago, carastro said:

Might depend on your camera and your coma corrector. 

this was the shape of my defocussed star before I chopped the end off the focusser.

I use a dlsr for my imaging 

[Dan13]

11 minutes ago, carastro said:

Might depend on your camera and your coma corrector. 

this was the shape of my defocussed star before I chopped the end off the focusser.

Hi, im guessing your using the x0.9 one? the one i linked about actually wants you to back focus a little more so a lot better

[carastro]

I used the Baader MPCC Coma corrector and an Atik CCD camera.

Carole 

[alacant]

1 hour ago, Anthony1979 said:

pds versions made for imaging

According to SkyWatcher, yes. In reality however, they need modifying before imaging if you want round stars. 

if you want a telescope to image out of the box, you're looking at a lot more financial investment;)

Edited May 30, 2020 by alacant

[spillage]

I could be really wrong here but in the back of my head I am thinking you do not need as much focus travel with a dslr, so the op should be okay?

[alacant]

2 minutes ago, spillage said:

the op should be okay

Unless the OP has the GSO or the ES coma corrector, the focus tube will intrude into the light path with a dslr attached.

HTH

[spillage]

Out with the hacksaw then....You can just take a large part out of the focus tube as this will also leave you with the part that stops the tube falling out if wound out.

[Anthony1979]

1 hour ago, spillage said:

I could be really wrong here but in the back of my head I am thinking you do not need as much focus travel with a dslr, so the op should be okay?

I wont be using the 150p for imaging when the 130pds arrives... So will the dlsr be ok without chopped it up... Last thing i want to do

[alacant]

1 hour ago, Anthony1979 said:

will the dlsr be ok without chopped up

On 22/05/2020 at 02:54, Anthony1979 said:

 

Hi

It depends which cc you choose and if you want round stars.

The SW 0.9, Baader and gpu will need the tube chopped. The ES and the GSO won't.

HTH