I would like to share some tips for 190MN after using it for 3 years.
Who this scope is intended for: Overall this is an amazing piece of equipment which, in my opinion, targets whoever is looking for cost/benefit in big aperture without diffraction spikes in the 1000mm range.
This is a heavy and expensive scope (compared to a regular newtonian), if you like or don't mind diffraction spikes just do yourself a favor and buy a regular newtonian. You can buy a bigger and faster newtonian spending less money. Now if you hate diffraction spikes this scope is an amazing option.
Biggest issue: Like most equipment in this hobby there are some details that can be improved, in this case is the focuser.
1- Collimation
Whatever you do: do not change Secondary height or Focuser alignment.
* "Official guide": You can search for the old manual ("Orion® Premium 190mm f/5.3 Maksutov-Newtonian Astrograph") and follow the instructions.
* What I do: I use a "HoTech 2" & 1.25" SCA Laser Collimator - Crosshair", that is enough. After collimating, if the secondary does not look "round" when looking at the front of the telescope then you need to fix its rotation (and collimate again)
2- Focuser
Most problems of this scope are caused by the original focuser which will cause tilt in your rig. Having that said, it is possible to use it.
If you are going to use the original focuser:
* Your scope orientation needs to be in a way that the focuser points to the floor (so it is not affected by lateral gravity too much).
* Do not extend the focuser, you need to add spacers to your camera rig and use the focuser in a way that it moves as little as possible (to avoid tilt).
* Use an adapter like "HoTech 2" SCA T-Adapter" to make sure your camera is centered in the focuser. Do not use the original focuser clamp, it will cause tilt.
* Using an electronic focuser as ZWO EAF helps to achieve focus without messing with the focuser too much but keep in mind that the original focuser (and the ZWO EAF) has some backslash, you will have to calculate it.
If you are changing the original focuser:
* The easiest way is to use a new focuser that will connect to the original focuser plate (so you don't mess with the collimation). If you need to change the plate, I suggest fully collimate the scope with a laser, change the focuser and achieve collimation by just repositioning (sliding) the focuser plate.
* In my case, after 2 years of using the original focuser with ZWO EAF I replaced it with a Essato 2". I built a custom adapter to attach it to the original focuser plate (3D printed a test prototype then custom ordered an aluminum 6061 version). I had fun and success with the original focuser but changing it was a huge improvement to the telescope.
3- Dew
I use a heated Dew Shield in the front (mandatory) + a dew heater strip in the back (primary).
4- Cooling
I 3D printed an adapter and attached a static pressure optimized fan with a dust filter on the back of the scope. I only use it before imaging for 30 to 40 minutes and keep it off for the whole night, it is enough in my case.
5- Vignetting vs rotators
Biggest sensor you can use is an APS-C and you will have some vignetting. The vignetting is not uniform so if you use a rotator you will need to take flats for all rotations you plan using during the night.
hope that helps
Who this scope is intended for: Overall this is an amazing piece of equipment which, in my opinion, targets whoever is looking for cost/benefit in big aperture without diffraction spikes in the 1000mm range.
This is a heavy and expensive scope (compared to a regular newtonian), if you like or don't mind diffraction spikes just do yourself a favor and buy a regular newtonian. You can buy a bigger and faster newtonian spending less money. Now if you hate diffraction spikes this scope is an amazing option.
Biggest issue: Like most equipment in this hobby there are some details that can be improved, in this case is the focuser.
1- Collimation
Whatever you do: do not change Secondary height or Focuser alignment.
* "Official guide": You can search for the old manual ("Orion® Premium 190mm f/5.3 Maksutov-Newtonian Astrograph") and follow the instructions.
* What I do: I use a "HoTech 2" & 1.25" SCA Laser Collimator - Crosshair", that is enough. After collimating, if the secondary does not look "round" when looking at the front of the telescope then you need to fix its rotation (and collimate again)
2- Focuser
Most problems of this scope are caused by the original focuser which will cause tilt in your rig. Having that said, it is possible to use it.
If you are going to use the original focuser:
* Your scope orientation needs to be in a way that the focuser points to the floor (so it is not affected by lateral gravity too much).
* Do not extend the focuser, you need to add spacers to your camera rig and use the focuser in a way that it moves as little as possible (to avoid tilt).
* Use an adapter like "HoTech 2" SCA T-Adapter" to make sure your camera is centered in the focuser. Do not use the original focuser clamp, it will cause tilt.
* Using an electronic focuser as ZWO EAF helps to achieve focus without messing with the focuser too much but keep in mind that the original focuser (and the ZWO EAF) has some backslash, you will have to calculate it.
If you are changing the original focuser:
* The easiest way is to use a new focuser that will connect to the original focuser plate (so you don't mess with the collimation). If you need to change the plate, I suggest fully collimate the scope with a laser, change the focuser and achieve collimation by just repositioning (sliding) the focuser plate.
* In my case, after 2 years of using the original focuser with ZWO EAF I replaced it with a Essato 2". I built a custom adapter to attach it to the original focuser plate (3D printed a test prototype then custom ordered an aluminum 6061 version). I had fun and success with the original focuser but changing it was a huge improvement to the telescope.
3- Dew
I use a heated Dew Shield in the front (mandatory) + a dew heater strip in the back (primary).
4- Cooling
I 3D printed an adapter and attached a static pressure optimized fan with a dust filter on the back of the scope. I only use it before imaging for 30 to 40 minutes and keep it off for the whole night, it is enough in my case.
5- Vignetting vs rotators
Biggest sensor you can use is an APS-C and you will have some vignetting. The vignetting is not uniform so if you use a rotator you will need to take flats for all rotations you plan using during the night.
hope that helps
