Diagonal Dilemma

[Jim Steele]

I'm having a bit of a quandry about which 2" diagonal to get for my Tal100RS.

I was looking at the Opticron one however its no longer availiable from my prefered supplier, FLO.

I can pick up a basic Skywatcher one for around the £30 mark, but it doesnt have dielectric coatings or look like it has brass compression rings to protect the eyepiece barrels.

Is it worth spending the extra on something like the Revelation one for £80, or william optics one for £120.

I guess with all these things you get what you pay for in terms of build. Im also keen not to have to replace it a few years down the line.

I would appreciate the advice,

Cheers,

Ben

[AndyH]

If it were me, I'd go for the one with the 'lowest profile' as possible. ie: not one with a 2"-1.25" adapter that protrudes 10mm above the diagonals 2" opening. You can get some that have a very low profile adapter with a cut out in the side to let the adapters locking thumbscrew slide and fit into.

Reason being is that some users of the crayford focuser 100RS reported some difficulty getting to focus with certain eyepieces. I reckon many 2" diagonals use up about 108mm of focuser travel plus 10mm when using the adapter. You can check how much inward travel you'll have left, by using the supplied Tal 1.25" diagonal, if you have it. If memory serves it uses 72mm plus the thickness of the 2"-1.25" adapter between it and the focuser. Measure how much inward travel you have left by focusing at infinity using a 25mm plossl. Fluffy clouds are handy to use in daytime.

Andy.

[AndyH]

If the Revelation 2" is the same one as I had a look at, then it has a very low profile adapter, which is handy. The specs look pretty decent too.

Perhaps 100RS users will chip in and report my stuff above as guff, but I'm positive some folk had probs with certain eyepieces using certain diagonals.

[Fozzie]

I think the Revelation is 1/10th and the WO (might be) 1/15th if its the durabright version.. I was looking a few weeks back at the same two, before I got an opticron of ABS.

I think there are a few other on ABS as we speak..

FLO do the skywatcher 2" that is used with the pro series apo's for a similar price to the Revelation..

I found the below quite useful when I was looking..

http://stargazerslounge.com/topic/125721-revelation-quartz-dielectric-diagonal-2-inch/

Hope this helps in some way..

Ta

Fozzie

[Fozzie]

Oh and I almost pushed the button on the revelation 2" before I bought second hand..  I have the 1.25mm left from a smaller frac and it's very good for the money, but doesn't have the compression ring... can't recall if the 2" does.. I think so, but not 100% sure...

[Fozzie]

What am I talking about, of course the 2" has a compression ring!

It's been a long day so far!

[AndyH]

Oh and I almost pushed the button on the revelation 2" before I bought second hand..  I have the 1.25mm left from a smaller frac and it's very good for the money, but doesn't have the compression ring... can't recall if the 2" does.. I think so, but not 100% sure...

I remember being quite surprised that the 1.25" revelation didn't have a compression ring. It was well built and couldn't quite figure out why they didn't go 'the whole hog' and machine a small groove n add a brass ring. Looks like the 2" version is sorted going by the pics of it.

Andy.

[rwilkey]

I have the SW Dielectric from FLO , and can highly recommend it here: http://www.firstlightoptics.com/diagonals/skywatcher-di-electric-star-diagonal.html  The price has been reduced quite a bit, I paid £102 for it a couple of years ago.

[damnut]

I was fortunate enough to get two Opticrons second hand, they are excellent. Else have the Meade UHTC and two SW, to be frank the standard SW 2"diag is pretty darn good.

[Jim Steele]

If the Revelation 2" is the same one as I had a look at, then it has a very low profile adapter, which is handy. The specs look pretty decent too.

Perhaps 100RS users will chip in and report my stuff above as guff, but I'm positive some folk had probs with certain eyepieces using certain diagonals.

Thanks Andy that's a very good point. I only have the stock eyepieces so have had no problems with them but I'm sure once I move away from the stock ones I may struggle with in focus.

It's a relatively new version bought last year, though the makers mark gives 2011 if that helps...

I have the tal diagonal I'll try and measure it. If memory serves baaeder do pretty short focal length diagonals but these cost pretty much as much as the tal ota.

[AndyH]

 I've had a look at some pics of measurements on an Italian astro forum regarding the 100RS and it's crayford focuser. I reckon the lower profile type, like the revelation 2" diagonal i mentioned before, should bring eyepieces to focus, unless they need exceptional amounts of infocus. The only ones I can think of that are like that, are certain members of the Antares Speers Waler 82° ultra wides.

 They mention using a Williams Optics 2", with it's 10mm thick adapter, not quite coming to focus with 1.25" eyepieces.

Hope this is of some help and do let us know how you get on.

Cheers,

Andy.

[Jim Steele]

Thanks Andy, I do have the stock diagonal so I'm not too fussed if it doesn't bring some 1.25" eps to focus. I do think the Revelation is the one to go with and it matches the 42 mm that arrived in the post today so my ocd is happy

[Jim Steele]

Well I didn't expect that to happen.. Just bought a William Optics one from Abs for £65. I'm a little concearned about infocus but sure I can recoup the cash if it doesn't suit...

Photos and first light will follow in n new post if the clouds ever go away..

[Dave In Vermont]

Well I didn't expect that to happen.. Just bought a William Optics one from Abs for £65. I'm a little concearned about infocus but sure I can recoup the cash if it doesn't suit...

Photos and first light will follow in n new post if the clouds ever go away..

I hope it works well for you. I have the Williams Optic di-electric, and they are/were beautifully made. Now they have a carbon-fiber body whereas mine are metal. I like them so much, in fact, that I have 3 of them. They work fine in the LX90/LX200 SCT's, as well as my F/9.3 achromatic refractor.

They all fit like a glove!

Clear Skies,

Dave