Mak, visual back and plan of attack

[Pixies]

Hi,

Now I've become familiar with Newtonians, I get a Mak to start the learning process all over again.

It's only a wee one - Skymax-90. A quick look at Mars last night between the clouds and I'm hoping to get a little more use out of it this weekend (weather permitting). I have the eyepieces from the current 8" dob.

I believe it has a M44.5x1.0 Maksutov thread on the back plate and a visual back that allows for a 1.25" star diagonal to be fitted. The actual hole in the back plate is only 18mm diameter (the internal circumference of the end of the baffle tube):

Now - I realise that this is a small Mak, but the thread on the back isn't much different from an SCT thread size, I understand, and adapters are available. I have the chance to get a reasonable 2" star diagonal. Is this appropriate for a little Mak like this? Would it just be a waste and would 2" EPs just suffer from vignetting?

I know it might be overkill, 2" attachments on this scope. But I would hope that anything I get would transfer to other scopes later. Perhaps the 2" diagonal with a 1.25" adapter and stick with 1.25" EPs would be fine?

 

Cheers

[Cosmic Geoff]

I really don't see the point of using 2" attachments on a small Mak with a 18mm hole in the backplate.  I would expect the vignetting to be severe. I don't use any 2" kit even with my 127mm Mak and 203mm SCT.  2" eyepieces come with a premium price tag.

What 1.25" diagonal do you have already?  According to reports, more expensive diagonals give an improvement in build quality, coating life etc rather than any improvement visible through the eyepiece. 

[johninderby]

The Skymax90 has vignetting problems with wider 1.25” eyepieces let alone 2” eyepieces. 

Fitting a better 1.25” diagonal is good upgrade though.

[John]

I put one of the Skywatcher 1.25" dielectric diagonals on the Mak 90 that I had. That worked well:

https://www.firstlightoptics.com/diagonals/SWdiagonal-20967.html

or in StellaMira branding:

https://www.firstlightoptics.com/diagonals/stellamira-1-25-90-di-electric-diagonal.html

With a max AFoV 1.25 inch eyepiece I could get approx 1.3 degrees (minus any vignetting) which is about as much as I could hope for from a scope which is never going to be a wide field instrument.

 

 

[johninderby]

Has anyone tried a Baader prism in the 90?  Should work well bit a bit expensive for a liitle mak though.

[Pixies]

Thanks all. I had found an Altair 2" Dielectric with 1.25" adapter going secondhand for not too much. Thought it would work here with 1.25" EPs but also a keeper for future scopes.

The diagonal with the scope is the cheapy plastic one that everyone recommends is replaced.