Coma Corrector For SW200P & Nikon D90?

[KingAndromeda]

Hey guys, I've taken a look online but are not too sure on the coma corrector I will be using on the sky watcher 200P regular speed. I'm not too sure if it's needed but the camera it will be used with is the Nikon D90. Will I be able to focus with the camera with the corrector on?

Sorry for being rather brief my iPads lagging intensely and it's taking a while to type

Thanks - Alex

Oh and when I said 'regular speed' i ment that it was the normal one; not the P-DS

[Lonestar70]

Hi Alex,

The correct coma corrector for the SW200P is this one

Skywatcher 0.9x Coma Corrector

You will also require the M48 camera adaptor for the Nikon.

Skywatcher DSLR-M48 Ring Adapter

Both are available from FLO.

It is arguable whether you can reach focus with the standard 200p focuser, as you may find that it has insufficient inward travel. especially since the coma corrector also works as a focal reducer (0.9x)... this will make the focus point somewhat closer to the scope. (opposite effect of using a Barlow)

You could certainly find focus using a Barlow inserted into the focuser and with the coma corrector fitted into this, however the net result would be a much longer focal length (not recommended).

The only other method would involve moving the main mirror cell up the OTA tube to bring it a little closer to the secondary... this will move the focus point further out on the focuser.

This may not be a good option since it may effect the warranty on a new scope.

If you have not already got the 200P (reference your question in another thread) then you would be better off saving a little more and going for the SW200P DS since this has been modified for DSLR photography and will certainly reach focus without the Barlow. It also has the low profile dual speed x 10 focuser fitted, which will be much better for fine focussing.

I hope this answers you question.

Best regards,

[Rustysplit]

The 0.9x reducer comes with a new focuser tube end ring which will allow to reach focus with the single speed focuser. I use it on my 200p with a nikon d5000 and it is fine.

[KingAndromeda]

Thanks a lot, you've bothe helped a lot

[KingAndromeda]

Both*