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De-Dobbing a 250px and upgrading.


Polar Bear

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I recently purchased and gave a quick first light review on the Skywatcher 250px here http://stargazerslounge.com/topic/230860-skywatcher-skyliner-250px-dobsonian-review-first-light/

Noted were the inadequacies of the mount to which I fitted a Azimuth bearing  http://stargazerslounge.com/topic/231510-ultra-simple-dob-azimuth-bearing-upgrade-no-machining-no-drilling/

But I was still unhappy with it having been spoiled with the smoothness of motorised EQ and fork mounts so decided to address this. 

Also the finder was terrible so this was attended to along with an Astro Engineering QR ball socket mount for mounting a Smartphone. 

First up the Skytee 2. After much deliberation ( and SGL reviews) I decided to go for this mount due to its payload and what others had said about it. 

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The 250px OTA (with the mods) is now around 15Kg so the Skytee required an upgrade to a new ADM Vixen saddle along with a 12" SW / Vixen

dovetail and secondhand SW tube rings from UKABS. Tube ring threads were re-cut using stainless M6 Flat Head Allen bolts. 

Losmandy items would have been better (and more expensive) but I have several lighter scopes with Vixen dovetails that I will be using with this mount.

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As the OTA weighs around 15kg I decided to attach a handle to the tube rings. Simple square section steel tube from B&Q, pipe insulation,

spacers are hard plastic doorstops that were lurking in the shed and it is held together with M6 allen bolts.

This helps when mounting and removing the OTA,  is also good for moving the scope about when observing and doubles up as a carry handle. 

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Easy bit was upgrading the finder. Thanks to SGL  (Mark at Beaufort) I purchased a Stellarview 80mm finder.

The shoe is a direct replacement for the SW one with the same hole spacing. 

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Next up the Smartphone mount. I sourced an Astro Engineering 10" SCT bracket and ball head with a QR plate from Astroboot. 

The bracket required a little splaying out to the right radius and then simply marked up, 2 holes drilled and bolted up again with M6 Allen bolts. 

This now holds my Nokia 1020 on which I have several 'point to the sky apps' to assist with my way around the night sky.

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post-7793-0-41673200-1419188843.jpg 

The focuser tube has had the file treatment to the running surface which has made it much smoother. 

I am just awaiting a 2" screw in EP holder instead of the dreadful SW adapter. 

OK, the mods have cost a bit but I am very impressed with the Skytee 2 and when correctly balanced with the clutches off it is a joy to push around. 

The 250px is a great tube for this mount. The EP position is really comfortable and my 5' 10" has no problem with viewing the zenith. 

The mount does however need a counterweight with this 15Kg scope on it. I have a 7Kg one on order. It will handle the scope but feels a little precarious to me. 

The Stellarview finder is probably the best you can have. It is actually better than some scopes I have had and with the prism gives right way viewing that is very easy to use. 

Just hoping for some clear skies now......

Paul 

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The skytee is a superb alt az mount, i am working on a project to get motor tracking on my one

Keep us updated as I would be interested also. My only gripe with the Skytee is the backlash in the slow-mo controls, however it is that good when balanced correctly I cannot see me needing them.

Paul 

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Nice job, but what is the advantage of an alt-az mount over an equatorial with a scope this size?

Is it the comfort thing?

Comfort, weight capacity and smoothness, the EP and Finder stay in the same place (no rotation) hence the OTA never needs to be moved (rotated) in the rings.  

For visual this feels much more natural than an EQ mount. Also the Skytee can take up to 15kg per side so there is the possibility of mounting a big frac or SCT for planetary visual. 

To do this with an EQ mount would be cost prohibitive. The smoothness is a huge improvement on a traditional dob mount. 

Paul 

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Last few 'bits' came today.

A 7Kg Meade weight and a 2" screw in EP holder with a brass compression ring. 

post-7793-0-66366000-1419376819.jpg   post-7793-0-19744200-1419376840.jpg

The weight has made a huge difference to the stability of the mount. I am really happy with this setup and consider it money wisely spent.

All I need now is to be able to see the sky which has currently been under a blanket of cloud for over a week.

Maybe a Lyra 102mm F11 or a Skymax 180Pro  would compliment the 250px and give me a great DSO and Planetary set-up  :icon_idea:

:icon_rendeer:  Merry Christmas  :icon_santa:

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  • 4 weeks later...

Looks like a great set-up.

paul any chance of some more pics of the AE bracket

Here we go. It is a substantial little unit made from ali and steel and the head has a QR plate. It would hold a substantial DSLR but I use it for my smartphone running Skymap.

The bracket just needed a little persuasion to match the tube radius. It is an Astroboot item so I not sure if they are still available 

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Looks like a great set-up.

It is growing on me, and surprisingly quick to set up if you can man-handle a 10" tube.

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