Baader MPCC coma corrector and Explore Scientific 82 degree 18 mm eyepiece

[DHEB]

I am the happy owner of an ES 82 degree 18 mm eyepiece that I use together with a Baader MPCC coma corrector on my SW 200 mm f/5 Newtonian. Until now I have been using the CC directly attached to the filter thread of the eyepiece, which I know is not correct. I now wish to buy the corresponding spacers so to be able to use the optical system correctly, but this is seemingly more difficult than I first supposed.

According to the CC specifications, the distance between the flat surface and the focal plane (camera or eyepiece) should be 55 mm. I have verified this when using the CC photographically and that worked fine. If one removes the T-2 adapter and uses the M48 thread instead, as I do for use with the eyepiece, this distance becomes 57.5 mm. Thanks to this table in a post in Cloudy Nights I was able to figure out that I need a spacing of 32.5 mm between the coma corrector and the eyepiece. The post includes some references to spacers, but aside from the Baader ones (28 and 14 mm, see here) I am having trouble to find suitable spacers in European retailers that would add up to 32.5 mm.

This is why I would like to ask you for help. Has anyone solved this problem before? If so, how? Where can I buy spacers suitable for adding 4.5 mm optical path to a system with 2", M48 threads?

Thanks in advance and clear skies!

[Louis D]

I wouldn't sweat it too much.  Visually, 5mm on either side of perfect should be good enough.  Agena and OPT sell spacers here in the states in many sizes.  They might ship to Sweden.

[Dave In Vermont]

4 hours ago, Louis D said:

I wouldn't sweat it too much.  Visually, 5mm on either side of perfect should be good enough.  Agena and OPT sell spacers here in the states in many sizes.  They might ship to Sweden.

I can't vouch for OPT (Oceanside Photo & Telescope). But I know AgenaAstro does. And they're to be preffered for their excellent and speedy service. Here's a link to their front-door:

http://agenaastro.com/

Have fun -

Dave

[Louis D]

5 hours ago, Dave In Vermont said:

I can't vouch for OPT (Oceanside Photo & Telescope). But I know AgenaAstro does. And they're to be preffered for their excellent and speedy service. Here's a link to their front-door:

http://agenaastro.com/

Have fun -

Dave

I have bought spacers from both, and OPT is slightly cheaper even when paying for shipping with them (Agena has free shipping in the US).  Quality wise, they seem identical.  Speed and quality of service was similar.  No complaints with either.

[DHEB]

Thanks @Louis D and @Dave In Vermont for the info. The retailers you mention do indeed have these spacers, but the cost of shipping is just too high. I will wait a bit to see if I can get any used, otherwise I will live with this for a while. It is not that bad, actually, 2/3 of the field is OK, is just the 1/3 outer part that shows signs of coma.

Clear skies!

[Coco]

How did you get on with this?   I'm looking for a similar setup as I have a spare MPCC III lying around and want to attach it to my 2" Moonfish wide field eyepiece and liitle VX6, if it works I'll buy something more exotic 

[Louis D]

17 minutes ago, Coco said:

How did you get on with this?   I'm looking for a similar setup as I have a spare MPCC III lying around and want to attach it to my 2" Moonfish wide field eyepiece and liitle VX6, if it works I'll buy something more exotic 

I have a version of that 30mm 80 degree eyepiece, and even when coma corrected, there's still plenty of astigmatism and field curvature in the outer field.  Coma from the scope is the least of the issues with this eyepiece.

[Coco]

17 hours ago, Louis D said:

I have a version of that 30mm 80 degree eyepiece, and even when coma corrected, there's still plenty of astigmatism and field curvature in the outer field.  Coma from the scope is the least of the issues with this eyepiece.

Well I suppose mine is 10 years+ old 

[DHEB]

On 2017-10-04 at 17:42, Coco said:

How did you get on with this?   I'm looking for a similar setup as I have a spare MPCC III lying around and want to attach it to my 2" Moonfish wide field eyepiece and liitle VX6, if it works I'll buy something more exotic 

Hi, I just did nothing about this. I can certainly live with these small aberrations.