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Orion StarSeeker IV 150mm Reflector Telescope Review

Orion’s StarSeeker IV 150mm Reflector (not to be confused with their 150mm Maksutov-Cassegrain) has a number of features that I applaud. However, some of the design elements are questionable, or at least unproven. This being said, it is still a pretty nice telescope.

Note: This same telescope is sold as the Sky-Watcher Star Discovery 150P outside the US, and has the same features Orion StarSeeker IV 150mm Reflector Telescopeand flaws as described in this review – with the exception of including slightly different eyepieces and a Barlow lens.

The Optical Tube Of StarSeeker  IV

The StarSeeker IV 150mm Reflector is a 6” f/5 Newtonian with a 750mm focal length. These are fairly common scopes, especially for beginning visual users or astro-imagers. However, the scope deviates from most of the common 6” Newtonians out there in the form of the primary and secondary mirror supports.

The secondary mirror is held in place by a spider made of ABS plastic, with rods instead of spider vanes. On a 4” scope this would be acceptable, but with a 6” f/5 these rods are of such a size that they introduce additional, unnecessary diffraction to the telescope and smear the image slightly more than regular spider vanes, slightly reducing contrast. The secondary mirror is still collimatable, however, so you shouldn’t have to worry about much else with regards to the plastic spider.

The bigger problem, however, is the primary mirror cell. The primary cell is made entirely of plastic and has a closed back so the mirror cannot cool down as quickly as a regular, open cell. But more seriously, there are no collimation adjustments of any kind. This means that if your scope is out of collimation, there is really nothing that can be done about it. There are some DIY solutions to fix the collimation using the screws holding the cell to the tube walls, but these will only work for minor tweaking and are not convenient in the field. It seems that the scope does a decent job holding collimation, but buyer beware.

Despite all this, the views are pretty good – no different from any other mass-produced 6” f/5 Newtonian. If I didn’t know about the odd secondary spider and primary cell and was looking through it I’d probably tell you there was nothing unusual about the optics.

The focuser on the StarSeeker IV 150mm Reflector is a 1.25” unit, made almost if not entirely of plastic. It works acceptably, though it will present some wiggle if you attach a heavy camera or eyepiece. Replacing it with a quality Crayford focuser requires some comfort with making modifications to the telescope and removing the optics, but can be done relatively easily.

The StarSeeker IV 150mm Reflector optical tube attaches to the StarSeeker IV mount with a short Vixen-style dovetail.


The StarSeeker IV scopes all come with 23mm and 10mm aspheric eyepieces with a 62-degree apparent field of view, providing 33x and 75x respectively. These eyepieces use two glass lens elements and an aspheric plastic lens element. Surprisingly, they actually work really well (particularly the 23mm) and are actually a cut above the cheap Kellners or plastic Plossls supplied with many entry-level scopes. However, the scope would certainly benefit from real Plossl or wide-angle eyepieces like Baader Hyperions or Meade Series 5000 UWAs.

The scope also includes a standard red-dot finder for aligning the SynScan GoTo system. It attaches to the optical tube with a standard Vixen/Synta-style shoe, so most finderscopes can be installed in its place should you find the need to do so.


The StarSeeker IV mount is fairly standard as far as cheap altazimuth GoTo mounts these days go – internals with gears that may or may not be plastic, simple motors, an 8-AA battery power pack, and stainless steel legs. However, the StarSeeker IV mount adds a notable improvement with its dual optical encoders. Orion simply refers to them as dual optical encoders, but Sky-Watcher brands them with the flashier name of “FreedomFind technology”. Regardless of what you prefer to call it, these encoders allow you to move the scope manually without ruining the GoTo alignment. This is great if you or someone else accidentally move the telescope, if you just want to move around the sky manually, or if you want to save power by manually moving the scope to the general area of sky you are observing in next and using the GoTo to fine-tune your pointing. This same tech is used on Orion and Sky-Watcher’s GoTo Dobsonians and I find it to be a fantastic convenience.

Setting up the StarSeeker IV mount is relatively simple, though I dislike that as with many of the cheaper Celestron NexStar units the SynScan controller has no internal clock. 6” of aperture does show you enough visually interesting deep-sky objects to justify the slightly tedious setup process, however. The SynScan database has 42,900 targets – maybe a couple thousand of which are viewable and a few hundred of which are interesting with a 6” telescope – additionally, some of these targets will be permanently below the horizon depending on which hemisphere you live in.


To put it mildly, the plastic mirror cell and spider construction and non-collimatable primary mirror in the StarSeeker IV 150mm Reflector concern me. However, there isn’t much evidence that the plastic parts cause any significant issues.

I can recommend this telescope with confidence, but I do advise caution if you plan on transporting the telescope regularly as this is more likely to lead to loss of collimation.

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