Sky-Watcher EvoGuide ED50

[DRT]

I recently had cause to part with my beloved TV-60 which I used as a travel scope and as a bling finder on my OOUK VX12 Dob. When I saw the new Sky-Watcher EvoGuide ED50 I immediately saw the opportunity for a much less expensive replacement so picked one up from Rother Valley Optics earlier this week.

My first impression is that this is a quality piece of kit - very solidly put together and with a stylish livery. My only initial grump is that the EP holder and extension tube have screw fitting rather than a compression rings. I would willingly pay another few pounds to bring that feature up to the same level of quality as the rest of the package.

My intention is to use this for visual observing, not guiding, so some sort of diagonal is required. This is where it gets difficult. So far the only way I have been able to reach focus with my Baader 45 degree Amici Prism is by adding a 2.5x Powermate, which results in this becoming an f12 mini planet killer rather than a wide field scope. I still need to try a simple prism diagonal to see if I can eliminate (or at least have the option of eliminating) the Powermate but I don't currently have one.

I have replaced the stock extension tube with a slightly shorter TS Optics 35mm T2 eyepiece holder so that gives me a compression ring to hold my Powermate. I have also bolted the mounting plate onto a Vixen dovetail so that I can attach the scope to a mount rather than a finder shoe. It its intended use it will be attached to a mini Giro rather than an Ercole as shown in the pictures.

 

I will report back later once I get the chance to point it at the sky...

 

Edited May 19, 2018 by DRT

[Timebandit]

 

Its a shame Derek that it does not come into focus with the diagonal as intended. Hopefully with a bit of experimenting and trial and error you will find a solution that works for you.

I personally really like the colour scheme that SW have adopted with the Green. But I think its a bit like Marmite, love or hate it. 

 

 

[LukeSkywatcher]

They really are beautiful. I'm pondering on one. I'm just unsure how to mount it on my Horizon 8115 tripod.

[DRT]

Just now, Timebandit said:

Its a shame Derek that it does not come into focus with the diagonal as intended. Hopefully with a bit of experimenting and trial and error you will find a solution that works for you.

I personally really like the colour scheme that SW have adopted with the Green. But I think its a bit like Marmite, love or hate it. 

I think a simple prism might be the answer to the focus problem. As for the green trimmings - I just assume it was designed to go well with Tele Vue accessories  

[Stu]

It’s definitely a very nice piece of kit. Hopefully you can find some way around the problem, how about one of the T2 Baader prisms? Is there a T2 thread on it?

[DRT]

1 hour ago, Stu said:

It’s definitely a very nice piece of kit. Hopefully you can find some way around the problem, how about one of the T2 Baader prisms? Is there a T2 thread on it?

That's exactly what I am planning, Stu, as soon as I forget that I'm supposed to be saving money and cutting down on expensive glass  

[DRT]

Good news - I just caught a lovely view of the new Moon through the ED50. Unsurprisingly it showed a bit less detail than the ED120 next to it but it was certainly a satisfying view from such a small scope. 

Waiting for Jupiter...

[DRT]

I've just had a look at Jupiter and although the disk and the moons were clear and in focus there were two rather distracting horizontal diffraction spikes shooting out across the FOV. I wonder if this is caused by the Amici Prism?

I think this is the first time I have used this prism for nighttime viewing. Perhaps it is intended for daytime use in a spotting scope?

 

[Chris]

2 minutes ago, DRT said:

I wonder if this is caused by the Amici Prism?

Yes, I've had the same issue with some prisms, although it's usually cheaper ones.

[DRT]

Thanks, Chris. 

I need to try a simple prism. 

[Chris]

5 minutes ago, DRT said:

Thanks, Chris. 

I need to try a simple prism. 

All I can say is I've tried Synta simple prisms and they were terrible for spikes, but the Tak prism's I've owned were really clean. I've heard good things about the WO prisms, and I'm about to buy one to find out for myself. 

[AndyH]

If a Tak prism(90 deg refersed like a mirror) doesn't work, probably nothing will. It uses up about 62-63mm of focus. it's the shortest i can think of. The various forms of amici or the rarer penta use up much more focus. Possibly more than a mirror type which can vary 'tween 73-85mm, depending on the manufacturer.

Andy.

[nicoscy]

I wonder what the threading on the back of the OTA is.. if it’s something “sensible”, possibly a Borg helical focuser could go there and really reduce the length of the finderscope, permitting the use of a diagonal without a Barlow....

[DRT]

1 hour ago, nicoscy said:

I wonder what the threading on the back of the OTA is.. if it’s something “sensible”, possibly a Borg helical focuser could go there and really reduce the length of the finderscope, permitting the use of a diagonal without a Barlow....

I had a look at the OTA yesterday and can't see a way of removing the focuser. I have a Lunt helical focuser and wanted to see if that would fit but the stock focuser and the plate it is attached to just don't want to budge.

[DRT]

I managed to shorten the light path of a cheap mirror diagonal so can now reach focus on terrestrial objects with about 8mm of inward focus to spare to hopefully reach focus on infinity when the sun goes down.

I’ve also bought a Meade Prism from a member here which I will try later this week. 

If the Meade works the long term solution is likely to be the Baader T2 Prism with a twist-lock EP holder the same as the one I use on my Lunt 50...

Edited May 20, 2018 by DRT

[DRT]

I’m off for a few days on a narrow boat this week so I have put this little travel case together to combine with a TV Telepod tripod and GR-2 Mini Giro ?

The Stella has been poured simply to give a sense of perspective in terms of the size of the flight case ?

Edited May 20, 2018 by DRT

[DRT]

I have now managed to focus on the Moon with the butchered diagonal and a TV 32mm Plossl. 

I still have a few mm of Travel to play with so hopefully infinity won’t be a problem. 

[happy-kat]

I like that and will look into if I can shorten my already almost there star diagonal. (though an erect image diagonal would be better for day time)

[DRT]

If the Meade diagonal that I have bought works I will spend money on a Baader equivalent because I’m a sucker for style over substance. 

If you are more sensible than me and you want a cheap prism for yours wait a week and I’ll sell you the Meade for what I paid ?

[happy-kat]

That a great thought.

It would be interesting to know what the chromatic aberration is like with the prism as that was what my prism experience has been so far.

[Peter Drew]

I'm seriously considering making a straight through or 90 degree astro binocular from a pair of these so any performance feedback is of great interest.  

[Rick_It]

There is a single screw before the focuser, the first screw after the end of the white tube.

What's for? To remove the focuser section?

Because, if the focuser section can be removed, then someone with a machine shop can cut about 1cm of tube and solve once for all the diagonal problem. I'm also interested on that scope, but it needs to work with a diagonal.

PS: I really cannot understand why SW has not made the tube 1cm shorter and the extension tube 1cm longer.

[happy-kat]

The screw locks the focuser from turning .

[DRT]

The butchered mirror diagonal and 32mm TV Plossl reach focus on the night sky but there are a few issues that are probably down to the very poor quality and nature of the diagonal so I will leave any judgement until I get a better piece of kit in its place. 

[nightfisher]

On 19/05/2018 at 19:39, DRT said:

I think a simple prism might be the answer to the focus problem. As for the green trimmings - I just assume it was designed to go well with Tele Vue accessories  

Derek, if you wish to try a prism, i can loan you a circle T 1.25 prism, i would require it back at some stage