MN190 Owners, Read This

[glend (Glen)]

I have received another private message from a member of the Cloudy Nights forum, concerning the collimation of the MN190. Basically, this guy thought he would use a Newtonian approach to collimation on a Mak-Newt, without doing any research first.
The MN190 secondary is attached to the rear of the corrector plate, and the optical path (specifically the Offset) cannot, and should not, ever be altered.. The guy in question moved the offset and messed up his scope optical path. He is not the first and will not be the last, I am pretty sure the MN190 manual stated that the offset cannot be changed.
So owners please be aware. Even if you remove the corrector for cleaning of the inside (a subject that I have covered in the past) do not disturb the secondary relationship with the corrector. If you do remove the corrector from its factory set position, you must use alignment witness marks before you remove it, as this will insure the correct rotational position of the corrector and thus the secondary is maintained on reassembly.

Finally, be cautious about buying any second hand MN190, and ask lots of questions, and if possible demand a trial before you settle the purchase. Focuser upgrades are another area to be very cautious about, as only the Moonlight focuser with the MN190 adaptor provider by Moonlight (and designed by me) provides the range of forward movement necessary to centre the drawtube correctly over the secondary. Never move the offset to suit the focuser, the focuser must be able to match the secondary position.

The MN190 is a great scope, and I am not trying to scare people off owning one, but they demand a duty of care.
GD

[peterl]

Just saw this...


Thanks for this info Glen.
I have had this scope for a while now and never touched the corrector plate or secondary. This scope holds collimation extremely well. Only check alignment every now and then. Still using the standard focusser with a Zwo asi533 color camera. As long as you tighten locking screws properly the focusser works well with pinpoint stars across the field. 1000mm focal length and a great all round scope.. This scope is a keeper.


Peter Langdown

Tinonee Observatory.

[toc (Tim)]

There is so much FUD about collimation of the MN190 - this thread has me very confused:
https://www.cloudynights.com/topic/8...0-collimation/

I replaced the stock focuser with a Moonlite and just used a cheshire to get the secondary mirror aligned. Am I missing something?

[glend (Glen)]

Originally Posted by toc

There is so much FUD about collimation of the MN190 - this thread has me very confused:
https://www.cloudynights.com/topic/8...0-collimation/

I replaced the stock focuser with a Moonlite and just used a cheshire to get the secondary mirror aligned. Am I missing something?

Did you buy the MN190 Moonlight adaptor? If so your probably fine. The alignment applies to the focuser draw tube, not the secondary. You want the draw tube of the focuser perfectly positioned above the secondary, which means it has to be far enough forward to achieve that alignment, which is what the adaptor gives you.

[toc (Tim)]

Originally Posted by glend

Did you buy the MN190 Moonlight adaptor? If so your probably fine. The alignment applies to the focuser draw tube, not the secondary. You want the draw tube of the focuser perfectly positioned above the secondary, which means it has to be far enough forward to achieve that alignment, which is what the adaptor gives you.

Indeed - got the adaptor - It has enough adjustment that I was able to centre it with a cheshire.