SkyWatcher 190MN Maksutov-Newtonian: A Stellar Performer
The SkyWatcher 190MN is a unique telescope that blends the strengths of Maksutov and Newtonian designs. This hybrid approach aims to deliver sharp images with a wide field of view, making it a compelling option for both visual astronomy and astrophotography.
Here’s a breakdown of the key features and potential:
Pros:
- Excellent Optics: The Maksutov corrector lens minimizes spherical aberration and coma, resulting in pinpoint stars across the field. This translates to crisp, high-contrast views of planets, deep-sky objects, and even stunning wide-field shots.
- No Diffraction Spikes: One of the reasons most astrophotographers choose refractors is due to the elimination of diffractions spikes. Diffraction spikes occur with reflectors that have a spider vane holding the secondary mirror. Most newtonians and SCTs have this issue. You can see the spike on bright stars for all Hubble Telescope images due to this design.
This image was processed from three monochrome images using Siril and then edited in GIMP. The raw data is from the Hubble Space Telescope. Note the diffraction spikes around the bright images. - Versatile Performance: The design excels in both visual astronomy and astrophotography. Its wide field of view is a significant advantage for capturing large celestial objects.
Cons:
- Heavy: The weight can be a challenge for some users, especially for extended observing sessions or for those with limited mobility. You will need a heavy duty mount to handle the load. The scope itself weighs 29lbs and will be more with cameras, guide scopes and other accessories. For this reason, I bought a Skywatcher EQ6R-Pro which is large enough to handle this scope.
- Collimation Sensitivity: While generally more stable than open Newtonians, the 190MN still requires occasional collimation checks, especially after transportation.
The Masksutov-Newtonian Design
The Maksutov-Newtonian telescope is a unique hybrid design that combines elements of two classic telescope types: the Maksutov and the Newtonian.1
Here’s a breakdown:
Maksutov Component:
- At the front of the telescope, there’s a thick, meniscus-shaped lens.2 This lens, often made of glass, has a slight curve and corrects for spherical aberration, a common optical flaw in telescopes.3
- The inner surface of this lens is typically curved to act as a secondary mirror, reflecting light back towards the primary mirror.
Newtonian Component:
- The core of the telescope is a large, concave primary mirror at the base. This mirror reflects the incoming light back up the tube.
- Instead of a traditional Newtonian diagonal mirror, the Maksutov-Newtonian uses the curved inner surface of the meniscus lens as a mounting point for the secondary mirror. Since the meniscus is permanently mounted, no spider vanes are required to hold the secondary mirror.
How it Works:
- Light enters: Light from a celestial object enters the telescope through the meniscus lens.
- First Reflection: This lens corrects for some optical errors and then reflects the light towards the primary mirror.
- Second Reflection: The primary mirror reflects the light back up the tube to the secondary mirror.
- Focusing: The light is then focused by the combined action of the meniscus lens and the primary mirror, and finally reaches the eyepiece for viewing.
Key Advantages:
- Sharp Images: The meniscus lens effectively corrects for spherical aberration, resulting in very sharp and clear images.
What You Get Out of The Box
The telescope is sold as an OTA and includes the following:
- Telescope
- 10 to 1 2″ Crayford focuser
- 2 telescope rings
- One dovetail bar
- 9×50 right angle correct image finder scope
As with most Newtonian designs, the focuser does not have a camera angle adapter. You will need to upgrade this yourself. I’m going to buy the new ZWO CAA which was just released.
Why I Chose To Buy It
Aperature matters. The bigger the aperature, the higher the image resolution. A higher resolution telescope allows you to see or photograph finer details. The Maksutov Newtonian performs like an APO refractor, but it can do it for a fraction of the cost. To get a refractor with a 7.5″ aperature, you would need to spend $7,000 to $10,000. That’s a lot of money and I don’t recall winning the lottery lately.
On sale you might find this telescope for around $1,800 which is quite a deal compared to a similar refractor.
It’s Fast
Out of the box, this is an F5.3 scope. That’s pretty fast but not quite as fast as an F4 imaging newtonian. My refractor I’m using now is an F7 but I added a focal reducer to bring it down to F5.7 which is a bit slower than the Sky-Watcher Mak Newtonian.
The faster the scope, the less time you need imaging. Although a bit slower than the F4 Newtonians, this scope has pinpoint stars across the entire field and does not require a coma corrector or field flatner. That’s a cool feature for sure.
1000 mm Focal Length
My current refractor with focal reducer is at 440mm which is wide field. I’m often frustrated because I just don’t have enough reach for smaller galaxies and objects. Therefore, I need a bit more magnification and 1000mm is just about perfect.
At 1000mm I can see Jupiter and Saturn but is still wide enough for a large number of galaxies and nebula. If I get a target that is just too large, I can switch to my refractor or create a mosaic with my new Mak Newtonian.
Overall:
The SkyWatcher 190MN is a high-performance telescope that offers a compelling blend of optical quality, portability, and versatility. If you’re seeking a telescope that excels in both visual and imaging applications, and are willing to invest in a premium option, the 190MN is definitely worth considering.
