MPCC spacing

[tooth_dr]

I have the MPCC fitted to my SW 250PX, and spaced at 55.5mm from the sensor of the 2600MC.  Does it look like it needs more spacing as the stars are all elongated towards the centre.  Maybe collimation, although I checked it yesterday and it looks ok.

 

Cheers

Adam.

[AbsolutelyN]

I'd try 56mm ... seems to work perfect for my Skywatcher 0.9 coma corrector on same scope. Just got a f4 Aplanatic Coma Corrector and hoping it is exactly the same as hate fiddling with stuff like that. 

Edited April 21, 2022 by AbsolutelyN

[tooth_dr]

6 minutes ago, AbsolutelyN said:

I'd try 56mm ... seems to work perfect for my Skywatcher 0.9 coma corrector on same scope. Just got a f4 Aplanatic Coma Corrector and hoping it is exactly the same as hate fiddling with stuff like that. 

Thanks Tristan, I think I've a couple of 1mm shims here.

[ONIKKINEN]

Top right corner looks noticeably better than the others, so i would say you have collimation/tilt issues that need to be dealt with first before you can get the spacing right.

For my TS Maxfield corrector the spacing is not that important (i think ive read many newt coma correctors are also not that strict), i can be between 54 and 56mm and there is really no noticeable difference compared to tilt/collimation which is impossible to not notice in the corners. Your MPCC might be more strict with the spacing of course, but i would look towards fixing the mechanical problems first.

[tooth_dr]

36 minutes ago, ONIKKINEN said:

Top right corner looks noticeably better than the others, so i would say you have collimation/tilt issues that need to be dealt with first before you can get the spacing right

I replaced the focuser last year with a returned one from FLO and it does look like someone may have adjusted the base of it. I added two mm to the spacing last night and it was definitely better. 

[michael8554]

The MPCC spacing depends on how you have attached it, could be 57.5 +/- 1mm:

[tooth_dr]

On 22/04/2022 at 13:29, michael8554 said:

The MPCC spacing depends on how you have attached it, could be 57.5 +/- 1mm:

Hi Michael, many thanks, you are right it was actually 57.5 I needed.  I added 2mm and it seems better, but I could probably add another 1mm.  Problem I have is that I cannot get enough in-travel if I add any more spacing!  I've everything maxed out, primary pushed forward as far as possible, with the addition of a Baader clicklock I can 'just' achieve focus.  I use this for galaxies only so a small crop of the edges is acceptable here for me, otherwise I'm going to have to lathe off a bit off the clicklock or replacing the mounting bolts of the primary etc.