Advice for diagonal requested

[SNT]

Hi all

I was recently given a Bresser AR102/1000 f/10 reflector, which I'm VERY happy with, but the supplied diagonal is a horrible cheap plastic thing and I have no confidence in it being (a) any good optically and (b) robust enough to take any eyepiece much more substantial than the supplied 26mm Plössl.

I'm afraid I've ended up somewhat paralysed by the choice of replacements and was hoping that your good selves could give some advice.

My budget would be about £100 or so (and then only as long as i can keep SWMBO ignorant... :-)

I'm tending towards the Baader T2 (non-Zeiss) prism - does anyone have anything good or bad to say about it?

Or, what else should I be looking at?

Thanks for any and all advice or comments...

 

A very confused Shane

 

[Cosmic Geoff]

Counter to intuition, even the cheap diagonals have adequate optical quality. By 'robust' I imagine you are thinking in terms of heavy and bulky high-end eyepieces. Without seeing the diagonal in question I can't comment.

However I note that your telescope is a f10, so the compact and lightweight Plossl eyepiece type should serve you well unless your requirements are particularly exacting.

Prism diagonals are good for long focal ratios e.g. f10.  However I suggest you have no pressing need to rush into a purchase before exploring all options.

If you are thinking of extra low power eyepieces, you'll want a 2" diagonal if your telescope will take them.

[SNT]

Hi Geoff

Thanks for the comments.

The supplied diagonal flexes somewhat even with the Plössl, so I figured I need something a bit better - I have to wear specs to observe so will need eyepieces with better eye relief than Plössls at the shorter focal length end, which will presumably be somewhat heavier, although I appreciate that at f/10 I won't need hand grenades.

The scope does have a 2" focuser, along with a T mount thread.

 

[rwilkey]

Hi Shane, welcome to SGL.  In my opinion, the Sky Watcher Dielectric Diagonal is about as good and robust as it gets, and takes my 30mm ES82 (1410g) with ease: https://www.firstlightoptics.com/diagonals/skywatcher-di-electric-star-diagonal.html

[SNT]

Hi rwilkey

Thanks for the recommendation - much appreciated.  It's well within budget as well, which is always a bonus!

[Mr Spock]

I use a Revelation Quartz Dielectric and optically, it's as good as anything out there. Solid build too.

[SonnyE]

I have a William's Diagonal. Super nice, but over your budget at 135.

But I looked it up so here is the link at FLO.

[SNT]

More great recommendations and good food for thought. Thanks!

[Grotemobile]

https://www.firstlightoptics.com/diagonals/william-optics-125-dura-bright-dielectric-diagonal.html

I find that the 2" diagonal is a bit of a lump. This 1.25 diagonal will take 2" Eps . £92.   

[John]

16 minutes ago, Grotemobile said:

https://www.firstlightoptics.com/diagonals/william-optics-125-dura-bright-dielectric-diagonal.html

I find that the 2" diagonal is a bit of a lump. This 1.25 diagonal will take 2" Eps . £92.   

How will a 1.25" diagonal take 2" eyepieces Steve ?

I agree with Mr Spock that the Revelation Quartz is very good indeed and about the lightest (still robust though) 2" diagonal around as well.

My current diagonals are Tele Vue Everbrights and Astro Physics Maxbright in the 2" size and a Baader T2 Zeiss for 1.25". All superb but the Revelation Quartz is blooming close for the £'s it costs

The stock Bresser is poor build quality but the mirror is, surprisingly, OK.

 

 

[domstar]

As for quality, I read on this forum that you can check out an object with the same eyepiece but with or without the diagonal (focus allowing). I tried it with my cheap Bresser and didn't notice any difference in image quality so I scratched a new one off my Christmas list. I still use it with my 100ed sometimes as my q-turret doesn't focus with my 2 inch diagonal. Robustness is another issue, though.

[SNT]

Hi all

It wasn't (quite) so much the optical quality I was concerned about so much as the Bresser diagonal seems to be made of something not much more substantial than stale cheese!

On a (somewhat) related note, does anyone know what sort of load the Bresser focuser can handle? Just in case I decide I can't live without a wide angle hand grenade.... :-)

[Ricochet]

If it's the newer model with the hexafoc you won't have any worries about overloading it. The low profile 2" eyepiece clamp is the worst part of the focuser though and is likely to tilt any 2" nosepiece at an angle so I suggest getting a diagonal with a smooth sided nosepiece if possible. 

[SNT]

Hi Richocet

Yes, it's the hexafoc version, so I'm glad to hear that I don't have to worry about it.. Thanks also for the info about the clamp - that's very useful to know

[YKSE]

22 hours ago, John said:

How will a 1.25" diagonal take 2" eyepieces Steve ?

That diagonal looks having 2" eyepiece clamp, as to how TFOV turns to be with a 2" eyepiece, it may very well depending on how large the clear aperture of this diagonal is, which regretablyno info about it.

Here's my test with baader T2 prism (32mm clear aperture) on daytime target:

1. 24mm MV with 27mm field stop:

2. 31mm Baader aspheric with 38mm field stop:

31mm showed noticeable larger TFOV than 24mm with T2 diagonal, but clearly less TFOV than 31mm in 2" diagonal, so the T2 diagonal 32mm seems to be the limiting factor for TFOV, it introduces noticeable colour fringe in the edge and eye placement difficulty comparing to in 2" diagonal.

To OP's question, as a large handgranade is in plan, a true 2" diagonal is the right way to go.

[SNT]

To be honest, when I started this thread I figured I'd never be able to afford a true UWA long(ish) FL eyepiece and so the extra few mm clear aperture of the T2 diagonal would be more than enough, allowing me, say, a 25 mm 68°.  Then I discovered the Skywatcher Nirvana eyepieces - a 28 mm 82° eyepiece for £185 does sound VERY tempting, especially since a number of people here say that the Nirvanas are nearly as good as Naglers in slower scopes.

It looks like my overall budget for diagonal, eyepieces etc is now totally shot to hell!

As Oscar Wilde said, I can resist anything except temptation...

[SonnyE]

 

15 hours ago, YKSE said:

1. 24mm MV with 27mm field stop:

 

That 24 mm looks big enough to use both eyes at the same time!

[Cosmic Geoff]

22 hours ago, SNT said:

 Then I discovered the Skywatcher Nirvana eyepieces - a 28 mm 82° eyepiece for £185 does sound VERY tempting, especially since a number of people here say that the Nirvanas are nearly as good as Naglers in slower scopes.

It looks like my overall budget for diagonal, eyepieces etc is now totally shot to hell!

It's your money, but if you desire wide-field you could just buy a short focal length 102mm refractor like the Sky-watcher Startravel for this kind of expenditure. Perhaps harder to hide from the Missus though.

[Grotemobile]

On ‎21‎/‎05‎/‎2017 at 11:33, John said:

How will a 1.25" diagonal take 2" eyepieces Steve ?

I agree with Mr Spock that the Revelation Quartz is very good indeed and about the lightest (still robust though) 2" diagonal around as well.

My current diagonals are Tele Vue Everbrights and Astro Physics Maxbright in the 2" size and a Baader T2 Zeiss for 1.25". All superb but the Revelation Quartz is blooming close for the £'s it costs

The stock Bresser is poor build quality but the mirror is, surprisingly, OK.

 

 

Hi . Have a read of the link I gave U . U will see it will take both size eps. The end that goes in the scope is 1.25. The other end is 2"
• Compression rings (both on diagonal and adapter) to prevent barrels from marring.
• Internal safety stop prevents 2" barrels from hitting the mirror.
• Designed for high-end scopes.

Is what it says . So I think this means it will take 2" EPs.

[SNT]

2 hours ago, Cosmic Geoff said:

It's your money, but if you desire wide-field you could just buy a short focal length 102mm refractor like the Sky-watcher Startravel for this kind of expenditure. Perhaps harder to hide from the Missus though.

I hadn't thought of that as a possibility. It could be the best way forward, but I'll never get another scope past the beloved wife at the moment! It would make a nice addition at some point though...

More to the point, it has made me decide that once I upgrade the diagonal, it will be to a 2" one, even if I don't actually get a 2" eyepiece for a while.

Thanks for your comments

[Sirius Starwatcher]

On 23 May 2017 at 11:41, SNT said:

I hadn't thought of that as a possibility. It could be the best way forward, but I'll never get another scope past the beloved wife at the moment! It would make a nice addition at some point though...

More to the point, it has made me decide that once I upgrade the diagonal, it will be to a 2" one, even if I don't actually get a 2" eyepiece for a while.

Thanks for your comments

Morning SNT, where in North Wales Are you? I have the Williams 2 inch Diaganol as well and you would be welcome to come over to have a look and try it before you commit to spending the hard earned cash.