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The Guan Sheng Optical 10" f/4 Newtonian Reflector
Submitted: Monday, 22nd August 2011 by Graham Stevens
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The Guan Sheng Optical 10" f/4 Newtonian Reflector

Specifications

Here is the product as advertised:

  • 10" f/4,
  • 3" M-LRN Imaging-optimised OTA reflector features GSO's extra-heavy duty LINEAR 10:1 microfocuser,
  • primary mirror cooling fan, 8x50 finderscope and large collimation knobs. 
  • 250mm x 1000mm
  • Has strong and smooth 3" diameter linear focuser! 
  • Includes new, wide, cast tube rings with guide scope mounting points

Introduction

Let me start by clarifying one point. I am no reflector expert. Prior to this one I have only owned one previous reflector - a TAL Russian reflector that I purchased on a whim from the Sunday papers in the UK. This was years ago and that scope gave me my first planetary glimpse as well as my first astrophoto.

Since then I have owned SCT’s and refractors. I have nothing against Newts, but the other scopes suited me better.

Since moving to Oz and having more space I have dedicated more time to this hobby and consequently when I saw an advertisement for a relatively cheap 10” f4 refractor I was very tempted.

I was looking actually to get a 10” Dob, but after talking to a few vendors, and after a few days of awaiting some details, I convinced myself that an approx’ 15-16Kg OTA would be the ducks nuts on an EQ 6 pro.

Knowing bugger all about collimation the f4 bit didn’t put me off and within six days my package had arrived - and what a package! The carton was about the size of a small boat and weighed in at approx 18kg.  It did fit across the back seat of my car though.

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The 10" f/4 in the carton

Packaging and Setup

The scope itself was well packaged, so much so that it took hernia type effort to extricate it from the box. There were no instructions but after all it was an OTA with a guide scope and a couple of adaptors, so not exactly IKEA level confusion. I opted for a right angle guide scope as this is my preference but the standard was a straight through jobby.

The scope comes with a 12V primary mirror cooling fan with a battery case and lead, I work it quite well with a standard 12v adaptor- lucky really as it takes a handful of AA batteries.

The focuser is a three speed Crayford on a 3” barrel.  It comes with 2” to 1.25” adaptor and an extension tube.  More on that later

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3 speed crayford focuser

The tube itself felt well constructed and feels quality. The collimation knobs on the primary mirror are quite big and the secondary has screw adjustments.  The primary is centre-spotted.

After hefting it about (it feels so – well, frankly, gravitational after using SCT’s and short tube refractors) I managed with considerable ease to attach it with a dovetail plate onto my EQ 6 Pro.

Balancing needed some extra weights from Big W gym section stuffed between the EQ weights

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Balanced on the EQ6

First Light

Well it was a shemozzle, I could not get a focus on anything. I felt the heat rising in my cheeks and the sundry swear words with Newt  attached were forefront on the sweating cranium.

See - that’s what collimation is for! I have since learnt that most vendors/manufacturers loosen the collimation screws so there is not so much tension on the mirrors when transported.  I might as well have been looking through a steamy pub window, which would have been warmer as well as more rewarding.

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Cooling Fan and Collimation Screws

A few days later I managed to collimate using a cheaper variety laser, some internet instructions and some sofa cushions plus the polystyrene packaging from the box.

Second Light

Well it was an incredible experience.

I had my small (80mm) refractor set up at the same time so I could compare views.

Omega Centauri with the 80mm visually is a nice starry blob with possibilities. With the 10” I found I was making out different coloured stars and the central mass looked like crazy stellar paving. It gave a three dimensional feel to it. It was wonderful.

Eta Carina is a hint of magnificence in the former- maybe more so now that I have taken some time to adapt eye (and shutter) to it, with the 10”- I loved the extra nebula around the keyhole seen without averting the pupil.

Imaging

I tried both planetary and DSO with a DFK camera and an unmodified DSLR.

Saturn was easy to find, I had to use the extension tube to focus the DFK mono camera. Once on the chip the planet stayed put and in focus. I really need to try this with a 2x powermate I think.

Apart from needing a giraffe’s neck to see the eyepiece, it was lovely and I think worthy of further views with higher mags.

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Omega Centauri with the 10" and a Canon 450D

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The Trifid with the 10" and a Canon 450D

With an unmodified Canon DSLR I didn’t need the extension tube but I found I could only focus with a camera to 2” adaptor. My notes say that I couldn’t get focus with my 1.25” adaptor which is a tad longer.  Maybe that was my error.

I have since only used the camera straight to 2” adaptor so haven’t investigated.

DSO imaging was a treat - for me the diffraction spikes of a Newt gave that little bit extra, plus I was pulling in more photons with the extra aperture. I really liked the photon pulling power of the aperture even at shorter exposures.

The focuser stayed where it was put so not unduly dismayed with it, however there is some machining tightness going on so every time I have taken the extension tube out there are some fine metal shavings inside the focus barrel. Not a disaster but worth noting.

Conclusion

I love this scope even though I don’t think I have got the best out of it yet:

  • A better focuser (motorised) and some more knowledge of collimation would make this scope a cheap fantastic option for imagers.
  • My EQ 6 pro doesn’t groan unseemingly with it and my camera/finder scopes attached etc. but I haven’t really pushed it for longer exposures or guiding yet.
  • My feelings are, don’t be scared by the f4, and go for it. I am looking forward to stretching this scope and getting much more out of it.

All in all a good value fast Newt with big aperture. A reasonable alternative to a Dob for those interested in imaging.

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10" Newt on the EQ6

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10" Newt
Review by Graham Stevens (graham.hobart). Discuss this review on the IceInSpace Forum.
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