What diagonal is any good?

[gazmass]

Hi

I have recently got a Celestron C8-SGT and thought i would upgrade my eyepieces. I have a relelation eyepiece set of 9mm, 12mm, 15mm, 20mm and 32mm and barlow. I have a meade 4000 6.7mm and a televue zoom 8-24mm with loads of filters.

I was going to get a moonfish 30mm after the sky at night review and then saw I need a new diagonal as mine only fits 1.25 inch. I saw the meade one is highly recommended but is 130 and was wondering is there that much difference? Is there any others i should get or should i pay the money. Or should I go for something else altogther? Please feel free to say what you think i should get. It is my birthday tomorrow and my girlfriend has given me 120 to spend. If it costs more still tell me then i can save up.

All advice is welcome and sorry for the long email

Gareth

[John]

Diagonals are one area where spending loads of money does not seem to deliver really noticable peformance improvements IMHO. There are 2 ways you can go, i) get a 2" diagonal with an SCT screw type fitting or ii) get a sct - 2" push fit adaptor and use a standard 2" push fit diagonal. I think the 2nd route is a bit more flexible unless you use, or intend to use a focal reducer when option i) is best.

Whichever option you go for the Antares 2" diagonals are good quality for their cost. Here is a link to the SCT one:

Antares Antares 2" mirror star diagonal for Meade & Celestron SCTs

If you choose to order from that supplier I'd phone the order in - they seem to work better that way !.

[Space Bat]

I can heartily recommend the William Optics 2" Dielectric Diagonal - it come with a 1 1/4" insert as well

Diagonals - William optics 2" Dielectric Diagonal with SCT Adaptor

I got mine without the SCT adaptor as I had one already - got it for £75 from Widescreen center at Astrofest - very pleased with it, much improved.

Chris

[NickH]

William optics for me too...found the Antares stuff to be quite awful quality.. IMHO

[John]

William optics for me too...found the Antares stuff to be quite awful quality.. IMHO

I guess thats the issue with lower cost stuff - variable quality. The Antares 2" I tried was pretty good.

I agree that the William Optics 2" is very nice though. My current 2" diagonals are an older, Japanese made Meade and a Tele Vue Everbright. Both excellent

[michael.h.f.wilkinson]

I second NickH, I am very pleased with my WO 2" dielectric. I replaced the rear end of my SCT by a 2" holder for use with a Vixen flip-mirror, and anyway, this will allow me to use the same diagonal on a different type of scope, as John suggested.

[glowjet]

I think some of the higher quality 2" diagonals come from the same stable, I have a 2" Astro Tech/TMB, it has a 1/10 wave BK7 optical glass substrate with 46-layer coatings, 99% reflectivity and all brass compression rings, won Sky&Telescopes hot product 2007, comes from the USA and is identical to the Williams optics and some of the others, Moonfish etc. Astro Tech is available through SCS Astro of Somerset around the £99 mark, does it make any difference?, supposed to give more light throughput, it could be, but it is very nice quality just like the Williams, and you can use 2" filters etc. you pays your money and takes your choice.

John.

[david o]

Hi Gareth,

I asked the same question a while back and was recommended the Revelation 2" diagonal from Telescope House.

It's also available with an SCT fitting: Diagonal Dielectric 99% Quartz LX.

Mine works fine and, to this newbies' eyes at least , shows no problems.

It's a solid, hefty bit of kit and the fit 'n' finish of it is very good.

At 80 quid it's good value for money with its' cost lying between that of the Antares and the WO diagonals.

HTH

[johninderby]

The William Optics 2" dielectric diagonal is very good. Although the bodies of the various brands of 2" diagonals may be similar it doesn't necessarily mean that the mirror inside is the same and meets the same specs. In particular does the 1/10PV refer to the mirror before the dielectric coatings are applied or after, and does it apply to the entire mirror surface? Although when used with 1.25" eyepieces the centre of the cheaper mirrors will be flat enough so that the difference might not be too noticeable.

Anyway the diagonal in the photo just arrived in the post and I'm looking forward to seeing if it's as good as it's supposed to be.

John

[Bigwings]

Hi,

You dont say why you want to go Moonfish. If you want wide views you might consider getting an f6.3 focal reducer which will give you wide views with the option of using it with ALL your EPs. I have the Nexstar 8" Celestron and I love it with the focal reducer and my 20mm & 40mm EP's. Like having a second scope.

Dont forget a long focal length SCT just isnt that fussy about EPs.

Just food for thought.

A reducer will cost £60-£70 second hand here or on fleabay.

Clear Skies

Mike

[michael.h.f.wilkinson]

I used to use a focal reducer on my C8, together with my 36mm Plossl. This I used quite happily for years. I since converted to using 2" EPs and use a 40mm Paragon instead. The latter combination gives a bigger true field of view (1.4deg vs 1.28deg) at a larger magnification (50x vs 35x). This is a huge advantage. You could reach more-or less the same effect using a 24mm wide angle EP (say the Baader Hyperion 24mm) and the focal reducer, but the extra glass will reduce throughput. I am also not entirely sure that there will be no vignetting at the extreme edge of the FOV.

[Ogri]

There's a couple of cheap diagonals in the scopes 'n skies bargain bin Second User Bargains - Scopes'n'skies

I bought one (the £35 2" mirror star diagonal) to tide me over until I can afford to get a dielectric (is it worth going to a dielectric?). The way I misplace stuff, it'll be handy as a spare anyway (I put the 45 deg one that came with the 'scope 'somewhere safe' - yeah right, it's now somewhere beyond an event horizon ). Eventually I'll probably need a spare in every room. lol!

I'm using a 1.25" prism star diagonal on the ST120 at the moment, and it leaves a bit to be desired tbh (though fair play I grabbed a quick look at the rather dim, beautifully orange coloured moon behind thin cloud as it cleared the horizon last night with the 40mm Meade 1.25", and the view was very nice indeed).

It's got shipped today, and conditions permitting, I will be able to give a bit of feedback on it soon (it does look like the normal Antares?). Fingers crossed it's an ok one anyway.

[NickH]

Shipped today from S&S...?

Good luck

[Ogri]

Shipped today from S&S...?

Good luck

Yes it arrived today.

One broken and one badly bent barrel screw which obviously happened before shipping (no bits in the inner bag). The 1.25" reducer just about fits but is obstructed by the end of the broken off screw just interfering on the inner surface.

Never mind, I'll never deal with them again.

The mirror 'does' look good though, and the construction is solid (apart from the ridiculously over flimsy grip screws).

I'll get a friend to drill out the broken piece, plus drill out the hole in the other to match, and retap the threads to something better.

The focuser end needs blackening internally too, but it all comes apart ok to be worked on by the look of it.

Might pay me to put an ad in the wanted section, to see if I can get a push in tube and a reducer tube, from a diagonal with a broken mirror section (I'm assuming the threads are the same?).

eta: still, every cloud has a silver lining, while looking for my watchmakers screwdrivers to see if I could get purchase on the broken screw, I found the 45 deg erecting diagonal I had lost by putting it in a safe place. lol!

[John]

Yes it arrived today.

One broken and one badly bent barrel screw which obviously happened before shipping (no bits in the inner bag). The 1.25" reducer just about fits but is obstructed by the end of the broken off screw just interfering on the inner surface.

Never mind, I'll never deal with them again.

The mirror 'does' look good though, and the construction is solid (apart from the ridiculously over flimsy grip screws).

I'll get a friend to drill out the broken piece, plus drill out the hole in the other to match, and retap the threads to something better.

The focuser end needs blackening internally too, but it all comes apart ok to be worked on by the look of it.

Might pay me to put an ad in the wanted section, to see if I can get a push in tube and a reducer tube, from a diagonal with a broken mirror section (I'm assuming the threads are the same?).

eta: still, every cloud has a silver lining, while looking for my watchmakers screwdrivers to see if I could get purchase on the broken screw, I found the 45 deg erecting diagonal I had lost by putting it in a safe place. lol!

Alternatively pick up the phone to them and demand a replacement - even though it was in the bargain section the thing should be in good working order, which yours is patently not.

I really wish I'd not posted the link to that outfit earlier in this thread - what a shower

Sorry you have had this lousy service Ogri.

[Ogri]

Ah no worries John, not your fault, the answer is to make it even better. The fundamentals really are pretty good.

I can't do stress any more and phoning them would be instantly doing stress, plus it was only a temporary fix until I could afford to get something from FLO (pity they don't do a budget one really).

[johninderby]

I bought a diagonal from them a while ago as I needed something fairly inexpensive to go with a small scope I was selling and guess what....it arrived with the barrel screw broken off. Fortunately there was about a mm of it still sticking out and I was able to get it out and replace it with another screw.

John

[Doug]

Gareth

agree with Dave O

Reverlation Astro 2", I have a Meade LX90 8" ACF and find it great

and only £80

Doug

Essex

[russ]

I have the WO, it's a great diagonal. Had it a year now and no complaints. But i'm with John on this one. I bought the WO to replace a standard Antares 2" push fit and i honestly could not see a difference between the two. I've had this happen in the past when i've pushed out the boat for a nice diagonal only to find the difference is so small it's impossible to detect. Last time was a Stellarvue dielectric to replace the standard Meade diagonal on the LX90. Never been so disappointed. That time i kept the Meade and put the Stellarvue up for immediate sale.

Russ

[michael.h.f.wilkinson]

When I bought my WO 2" it replaced the old 1.25" Celestron, and the difference was clearly noticeable in the 1.25" EPs (the centre of the mirror has the best correction, so an over-sized mirror helps), but I never compared to other diagonals.