Orion OD300L

Background

I have been an observing amateur astronomer for around five years, my first purchase being a very neat and intriguing-looking etx90/autostar seen in a camera shop. This provided fascinating views of the moon and planets along with the brighter Messiers (some were not detectable from my back garden) and some other objects. The ocasionally erratic behaviour of the goto system was a source of frustation. I believe they have improved since then. Next came a Meade LX10 8inch SCT. This provided dramatically clearer views of the Messiers. I particularly remember my first looks at M11 and M37 after getting this scope. The Leo Messier galaxies were now obvious from my site. Also more was visible on the moon and planets. Perhaps the view of some objects was aesthetically less pleasing, but the etx now got little use and was eventually replaced with a Megrez 80 giving the possibility of widefield views. In addition to my own scopes, I have viewed through various instruments including Newtonians up to 20 inches and apos up to 7 inches.

Purchase

And so on to the subject of this review. The OTA was purchased second-hand initially on an eq6 mount. Since I was unhappy with the condition of the mirror, I approached Orion UK. For an agreed price, Barry and John Pemberton at Orion reworked the mirror to not quite 1/8 wave (0.141 wave p-v Strehl 0.984) and recoated with Orion's Hilux enhanced coatings. They also serviced the eq6, their own preference being for the vixen series mounts. I quickly found the (early model) eq6 cumbersome to use with this scope. The eyepiece ends up at very odd angles and at a wide variety of heights. I came to the conclusion that large equatorial Newtonians should have rotating rings. A low pier would have also helped. The mount drives also seem to induce HF vibration visible as a slight but significant blurring detectable by switching off the drive at high power under good seeing. This is probably a result of the lack of microstepping in the motor controller. For these reasons I sold the eq6, having explained my reservations to the purchaser. In it's place I bought Orion's new aluminium Dobsonian mount. The scope I am reviewing is therefore equivalent to Orion's OD300L with HiLux upgrade and 1/6 to 1/8 wave optics. If bought from Orion as a package, it comes with a pair of plossl eyepieces. I believe a crayford focusser is an option, I purchased this at the same time as having the mirror reworked. The rack and pinion focusser used by Orion is of high quality.

Optics

I have found the performance of the scope to be extremely pleasing. The results on a variety of objects are in a different league to the smaller sct. Even my wife readily concurs with this! With a focal length of 1600mm there is also the possibility of a bigger true field, the sct giving an effective focal length of around 2250mm with a 2in back and diagonal. I have always found globulars to be highly dependant on seeing as well as transparency. I tend to go for pleasingly crisp views rather than teasing out the last bit of detail and I don't push magnification when I've got an interesting view. On M13 the image at 100X with a 16mm Nagler is beautiful. Stars of various magnitudes are resolved across the core of the cluster. The two 'crab claw' stellar arcs stand out clearly. Similarly pleasing is nearby M92. Iota Cass splits beautifully. The colours are nicely vivid on various doubles. The contrast with the backdrop of space is superb. Earlier in the year Jupiter with the same eyepiece barlowed showed sharply-etched cloud band detail and delicately defined festoons. Shading is visible within the GRS as well as numerous lighter pockets in the GRS turbulence wake. Jupiter's moons and their shadows are cleanly circular. Lunar crater terraces are crisp edged. The definition on rilles and the straight wall scarp is very satisfying. Overall the Moon is again a new experience both in terms of detail crispness and colour/contrast. Back to Deep Sky. With a 31mm Nagler fitted the field is pretty sharp edge to edge and I feel no need to consider a paracorr with this F5.3 scope. Fold back the eyecup and there is a lovely panaramic effect, with a good sense of 'immersion' in the field. With this eyepiece fitted the double cluster looks magnificent with both clusters nicely sharp and a true fov of around 1.6 degrees. Other showpiece clusters such as M44,46,47,34-38 also look very nice in the 31, with plenty of 'room' around them but good resolution of the cluster. Edge of field defintition compared to the sct is not a problem. I was anticipating this being worse with the Naglers and the faster scope, but this is not the case at all. Another of your recent contributors, Nick Koiza and myself both think we detected part of Stephen's Quintet from Kelling Heath, adjacent to clearly-visible NGC7331. I have noticed, contrary to some opinion, that the results with this scope improve noticeably with freshly cleaned mirrors.

Mount

The Dobsonian mount works nicely overall. A good ebonystar mount has less stiction (initial resistance to motion prior to steady-state friction) but the motions are easily controlled and very well damped. The scope can be put into the car in 3 minutes and set up in the same time. It splits into base plus tube in only the time it takes to lift one part from the other. Being made entirely of aluminium it is virtually indestructable. The five aluminium plates used are nicely cut and finished. The lower floorstanding section is a compact three-spoke item. This really needs flat and firm ground for best results. The tube rings allow the OTA to be repositioned rotationally and balance-wise. With the F5.3 tube there is not much movement available to re-balance the tube for heavy focusser loads.

Competition and Delivery

The scope faces strong competition from various bargain basement dobs from Chinese builders. I have not done comparisons and have heard good things about some of these scopes. However I would be suprised if the optical results on demanding objects under good seeing are as good as with the Orion UK mirror. The bases can also show signs of wear and tear fairly quickly.

Many of Orion UK's products are built to order and delivery time for the mount was around 4 weeks from receipt of order. Incidentally Orion are happy to show visitors around their production and test facilities.

Summary

As you can see I am pleased with this scope. Practically speaking, if you have space to store it, it is quick and straightforward to set up, operate and travel with by medium-sized car, assuming you have folding seats. It's performance has no negative points compared to it's predecessor other than the lack of tracking. This is not that much of an issue up to 200X especially with an ultrawide type eypiece. At lower powers you often don't think about it, it becomes second nature to nudge. Optically everything is improved. My recent trip to Kelling Heath Star Party proved conclusively that I need a solution for secondary dewing, but otherwise the scope is straightforward and satisfying to use. I have no relation with Orion Optics other than as a customer.