Explore Scientific AR 102
Feb 09 2016 10:10 AM by phxbird
Review: davejlec's Paralellogram Mount
Feb 08 2016 11:26 AM by tlriedel
Annals of the Deep Sky, Volumes One and Two
Feb 08 2016 10:03 AM by twatson
Discovery 17.5” Split Tube Dobsonian Telescope
Feb 07 2016 09:20 AM by clay1022
REVIEW OF SUMERIAN OPTICS ALKAID 16” TRAVEL SCOPE
Nov 26 2015 05:38 AM by alexvh
Astrotrac TP3065 Pier Review
Nov 20 2015 08:03 AM by James Waters
Apo-tmosphere: Gutekunst ADC Review
Sep 23 2015 11:18 AM by pbsastro
Optolong LRGB Filter Testing and Comparison wit...
Sep 22 2015 01:41 PM by turbo399
The Unsung Hero
Discuss this article in our forums
The Unsung Hero
by Malcolm Bird
What’s got everyone’s attention these days? Well, it seems to me that it’s an 80-100mm class APO refractor… The drawing cards being color free performance, excellent images, quick cool down and portability.
Of course, the down side is the price – you’re looking at anywhere from $900-$3000 ++depending on brand…. and you don’t get a mount, and very often no diagonal, finder or eyepieces either for that price.
So what if I was to tell you that you could have 75-80% of the performance of one of these high end APO’s for about $100….. That’s right, and if you look around, that price will also get you a serviceable mount, finder scope and a couple of generic Plossl EPs too!!
So what is this mystery APO killer?
Well, it’s the ubiquitous 114mmF8 Newtonian reflector sold by virtually every mfr. and department store in the world under a plethora of names – Galaxy Quest, Planet Buster, Lunar Rover – you name it – all promising that you’ll discover your own planet, if not galaxy..
It can be found on Ebay or Kijiji for a pittance –people having succumbed to the glitzy advertising and promises, and then not being able to make sense of the equatorial mount, know nothing about collimation, disappointed that the computer mount didn’t perform as advertised, or it was just a gift that didn’t work out.
But here’s the thing. These scopes use spherical primary mirrors and by now they’re very good at making them, with excellent polishes and smooth figures – not hard on mass produced spherical optics... Their F8 focal ratio puts them within 1/4W of a theoretically perfect parabola, so they offer ‘diffraction limited performance’ and they are 100% apochromatic – being a mirror only system. They are very light (ie: portable) and the open tube allows for a relatively quick cool down. They are arguably more comfortable to use with their eyepiece location near the front of the tube instead of the rear, and the fact that you don’t have to extend the tripod as high to use them as you do for a refractor means you’ll get a more stable platform.
Seeing is very often the limiting factor in our hobby, and often, our gazillion dollar wunderscopes are limited to a pedestrian 150X or less – a magnification range that these 114mm scopes operate quite comfortably in – that being only ~30Xper inch of aperture.
And given reasonable collimation (which is not overly critical on an F8 Newtonian anyway) , these 114mm Newtonians with their small secondary obstruction will give a high end APO a very sobering run for its money..
I know, I know, I can hear the cries of foul from the four corners of the universe. Of course it has better resolution and brighter images - it has more aperture. Of course it has no false color, it ‘s a mirror only system. Of course you don’t need a $200 dielectric diagonal – it’s a Newtonian. Of course it’s more comfortable to use when you don’t have to get on your knees in the grass …..well, duhhh!
I have a Meade Taiawanese made 114mm Newtonian in my Astrojunk pile. I do question the mirror to diagonal spacing as the focuser needs to be racked wayyyyy out to focus, which means it’s probably not fielding the full light cone from the primary, but despite this, the scope throws up bright, crisp images that equal my excellent Celestron C5 SCT..(125mm).
They are reasonably put together and all come with some sort of clamshell than can be easily adapted to a Vixen rail if you just want to use the OTA on your own mount.
Well, these scopes are built to a ‘Wal-Mart’ price point, which means they have skimped wherever they could. The focusers are plastic, the tube is rolled/seamed steel and the CG1 mounts could be sturdier. The finder and eyepieces, while serviceable, are not the best quality– but what do you want for $100? Many people spend more than this on a finderscope or a single eyepiece….
It’s not sexy and it’s not cutting edge, but if all you care about is what you see in the eyepiece, then you can’t get better bang for your buck.
So next time you Takahashi and Televue jocks thumb your noses at that guy with the lowly 114mm Newtonian, you may want to take a peak thru it, and then do the value/analysis math.
And having said all that, I confess to owning a TV-85 – who says advertising doesn’t pay….
- SherwoodL likes this