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  #1  
Old 25-04-2006, 07:41 PM
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Starkler (Geoff)
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Vixen Porta mount and R130 newtonian

In my search for a grab and go scope of reasonable aperture and portability I came to a decision to purchase a Vixen Porta mount bundled with a Vixen R130sf newtonian. A few weeks later it finally arrived last Friday giving me a new toy to play with for the weekend

Porta mount.
As can be seen its a single arm alt-azimuth mount on an alumium tripod. This mount can be manually pushed in both axis with adjustable tension and has full 360 degree slow motion controls. It accepts a standard Vixen or Synta dovetail.

Underneath the rubber pad in the base the included allen keys needed to adjust and dissassemble this mount are held by small magnets.
The Portas' height at full extension is sufficient that the little newt had an ideal standing eyepiece height for me, and a little too tall for my observing friends last night. Im am 6ft 2"

What can I say, this mount performs beautifully and is clearly a cut and a half above over cheaper offerings like the AZ-3. Tracking Saturn in this scope at 162x with a 4mm ortho was a breeze using the slow motion controls with the stability of this mount at full extension a nice surprise, with damping time of about two seconds. Everybody in our observing party last night was very impressed with this mounts smoothness, ease of use and stability. It has a real "premium feel" to it.

If you are looking for an alt-az mount for a small scope, say a 100mm refractor, they dont come much nicer than this There are limits and the geometry of the arm means ota size is limited to about 170mm diameter without hitting the ota at zenith.

R130sf Newtonian

The R130sf is a 130mm f5 newtonian of Chinese manufacture. Unlike most other small newtonians, this one has a real metal spider and fairly decent components including a collimatable mirror cell with hex grub lock screws.
The exception is the focuser, being entirely made of plastic, which lets down the general quality of this scope.
The scope came with two silvertop plossls, 20mm and a 6.5mm. They both work very well in this scope and amongst cheap plossls, I quite like the silvertops so these were a nice surprise

First light star testing showed astigmatism from a pinched primary, so it was time to strip down the scope and loosen off the mirror clamping blocks. I also took the opportunity to centre spot the mirror.

After sorting out the collimation, the optics were found to perform quite well for the size and price of this scope. On Saturn, cassini was well visible with banding visible on the planets globe. Later on details were visible on the equatorial belts of Jupiter at 162x and still I was limited by the seeing.
Not too bad for a small rich field newt

About the focuser and design of this scope, you can see that it sticks out a long way from the ota. The design is such that you use the extension tube for visual, or remove it with the focusers top being threaded, designed to take a camera fitting. This might even work with a binoviewer ( I wish Steve was there ).
The plastic focuser does flex when you put heavy eyepieces into it and the image shifts as you adjust focus. It is annoying when trying to focus at high power and this focuser is certainly the weak point of this scope.

The secondary is quite large at 45mm, giving a 35% central obstruction. The dual role photograpic/visual design of this scope with the focal point so far out of the ota means that the secondary is so close to the primary to only just catch the light cone. I am tossing up whether to get a new ota tube made so that I can push the primary back, or to just mount a better focuser on a high self made adapter.

To put all this in perspective, the OTA including two plossl eyepieces, dovetail and tube rings (nice I might add) only added about $240 over the price of a Porta mount on its own. Considering its optical performance, I still reckon I got a good deal

As it is, it's a great grab and go package. If I get a better focuser, it will be close to perfect for my needs as a lightweight grab and go travelscope

Many thanks to Steve at http://www.myastroshop.com.au
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Last edited by Starkler; 25-04-2006 at 08:04 PM.
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  #2  
Old 25-04-2006, 10:14 PM
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janoskiss (Steve H)
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Sounds pretty damn good Geoff. Just upgrade the focuser and add a barrel extension if necessary.
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  #3  
Old 25-04-2006, 10:49 PM
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Starkler (Geoff)
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Just been checking out Joop in it again and the jewell box is something else with pinpoint stars with little diffraction rings around them. The seeing is great tonight, who needs a refractor

Last edited by Starkler; 25-04-2006 at 11:41 PM.
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  #4  
Old 26-04-2006, 10:52 AM
dhumpie
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Hey Geoff,

Nice purchase You say that the OTA is of chinese manufacture??? I though it was of Japanese origin????

Anyway....

Darren

p/s: How heavy is the whole assembly? Looks pretty light....
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  #5  
Old 26-04-2006, 01:32 PM
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Starkler (Geoff)
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Quote:
Originally Posted by dhumpie
Nice purchase You say that the OTA is of chinese manufacture??? I though it was of Japanese origin????

p/s: How heavy is the whole assembly? Looks pretty light....
I have been told that model numbers containing an S or F are of Chinese make. Anyway the Chinese glue-grease in the focuser is a dead giveaway I'll try cleaning and regreasing it and see if that helps.

Yes it is very light easily picked up and carried around. Total weight is 9.5kg.
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  #6  
Old 26-04-2006, 04:33 PM
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Dave47tuc (David)
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Very nice Geoff.
My thoughts were what a great set up. After using the porta mount and looking into the scope I say you are on a winner.
The mount was very easy to use, a big plus. Tracking was very smooth even with the 4 mm Ortho.
The scope itself was a big surprise. Images nice and sharp and Saturn in the 4 mm very good. Yes the focuser was itís only down fall. Fix that and you got a great scope there.
Well done mate on a great purchase. I hope to look through it again soon.
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  #7  
Old 01-05-2006, 01:14 PM
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h0ughy (David)
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you could get one of those bintel or andrews crayford focusers for $140 odd dollars, nice setup!
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  #8  
Old 01-05-2006, 01:56 PM
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iceman (Mike)
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Sounds great! That would fit in the back of the car on family holidays.. something my 10" dob certainly can't do right now.
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  #9  
Old 04-05-2006, 11:37 PM
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Starkler (Geoff)
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Quote:
Originally Posted by h0ughy
you could get one of those bintel or andrews crayford focusers for $140 odd dollars, nice setup!
I upgraded the crayford on my dob to a new one with 10:1 fine focus control, so the old crayford is going on the R130
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Old 05-05-2006, 05:08 AM
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iceman (Mike)
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Nice one Geoff.. add it to the review!
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Old 12-06-2006, 04:53 PM
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Starkler (Geoff)
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Quote:
Originally Posted by Starkler
I upgraded the crayford on my dob to a new one with 10:1 fine focus control, so the old crayford is going on the R130
Done and maybe looking a bit silly

On this rather lightweight scope the gso crayford is a big heavy thing.
Its mounted on whats basically a wooden box of a suitable height to get the right focus range for the eyepiece combinations that I use.

I started by covering the old focuser hole with a piece of paper with a small centred hole to aid alignment with a laser. I marked the point geometrically opposite on the wall of the ota with a small dot of white paint .

Then came a lot of work with a dremel and sandpaper to get the feet of the wooden box square so that the laser lined up and the new focuser square.

I did some other mods relating to the spider assembly. The collimation screws as supplied had a conical tip with a small hole in the middle designed to bite into the metal , which is exactly the opposite of what is desired.
These screws had made divots in the aluminium secondary holder, making it impossible to rotate the secondary to fine tune collimation.

I rounded off the edges of these screws with the dremel, and I made up a washer made of thin steel which sits between the collimation screws and the secondary holder. Much nicer

I also added flocking material opposite the focuser and around the bottom end of the ota. You can pick it in the second photo.
So does this focuser look like an overkill or what?
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  #12  
Old 12-06-2006, 06:10 PM
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Striker (Tony)
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Not an overkill at all Geoff...I just dont know which has more aperture...the focuser or the Newt....lol
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Old 12-06-2006, 07:35 PM
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Astroman (Andrew Wall)
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So when you putting the ED80 on it for a finder scope?

That certainly looks impressive.
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Old 12-06-2006, 09:44 PM
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Whack in the 31mm nagler and then we"ll see if its a overkill nice mods/setup
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  #15  
Old 12-06-2006, 10:17 PM
stringscope (Ian)
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Hey Geoff, assuming the secondary is large enough, I calculate the 31 Nagler should give you just under 4 degrees TFoV. Wow, not bad
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Old 13-06-2006, 08:31 AM
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janoskiss (Steve H)
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Yeah Geoff, drop that 31mm Nagler in and take a photo!
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Old 13-06-2006, 10:58 AM
dhumpie
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Holy cow Geoff. The focuser looks bigger than the whole scope

Darren

p/s: and yea do what Steve suggest and drop the 31 nagler in...lol
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  #18  
Old 13-06-2006, 05:09 PM
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Dave47tuc (David)
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Better still put the 2" Barlow then the 31 mm Nag in

Looks funny but I hope it works a treat.
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Old 13-06-2006, 05:20 PM
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Then anyone trying to look through the back of the primary mirror instead of the eyepiece would be excused!
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Old 13-06-2006, 06:15 PM
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Starkler (Geoff)
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Do I win the prize for the widest field newtonian on IIS ?

Quote:
So when you putting the ED80 on it for a finder scope?
I sold the ED80 after buying this one and seeing how much brighter it was
The R130 kills the ed80 as a visual scope.

Quote:
Hey Geoff, assuming the secondary is large enough, I calculate the 31 Nagler should give you just under 4 degrees TFoV. Wow, not bad
Yep the 31 nagler has been in it, but Im sorry to report that such a wide fov on an f5 scope comes at an unfortunate cost of excessive coma

My 24mm panoptic gives a 2.5 degree view which is enough, so the ideal would be a nice 1.25" focuser, but do you think I can find a suitable one?
I was considering the JMI 1.25" crayford which was for sale here, but the problem with that is that the drawtube is 3 inches long, and the inner diameter is 1.25" and not bigger, meaning that Im going to get vignetting
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