sob sob.. my revelation diagonal..

[Piero]

Sob Sob!  

Yesterday evening I was doing some terrestrial observation (and testing my new second hand Nagler 3.5mm eh eh!  - it works wonderfully - thanks Lee), when the eyepiece holding screw of my revelation dielectric diagonal got stuck. Fortunately no eyepiece was placed at the moment, but the screw stop rotating inward or outward. 

I finally managed to unscrew it, by using a piece of cloth. The thread in the end is damaged and does not allow the screw to enter. 

I do not know whether this is a single unlucky case, but I think that the mechanism should be much more solid that this. Particularly since that diagonal was less than 6 months old.. 

Dunno, many people like it. I think the mirror is works well, but the mechanics (at least for the one I got) does not seem to be well built..

So, now I have a diagonal which cannot lock the eyepiece.. scary..

I know it costs more, but I will replace it with an TV everbrite. At least I can be sure that every single item passed a severe quality control. 

[Dude_with_the_tube]

i am personally not a fan of diagonals or prisms with screw fitting for eye pieces.Not that the screw can jam or get lost,but purely because it leaves marks on eye piece barrels or on barrels of other equipment you use in diagonal if you over tighten them.

Try to get a diagonal/prism with compression ring as your next purchase.

[Piero]

My revelation diagonal has the compression ring, but you need to screw to compress the ring. 

It is this one: Revelation Dielectric 99% Quartz 1.25 Diagonal

[YKSE]

Sorry to hear that, Piero.

I'd recommend you to take a serious look at Baader diagonals, prism or mirror. The ones I have (prism and heschel wedge) are of excellent quality, the SC thread or T2 thread connections open a whole world of oppotunity for other adaptions like binoviewer, Clicklock clamp etc. and they are very price-worthy IMHO.

[Piero]

Thanks YKSE for your suggestion! Most products seem to be for 2". Could you post the links for yours, please? 

I will need a 1.25" on both sides for the TV60..

[JamesF]

I'd be tempted to tap the hole out to a slightly larger thread and use a different screw.

James

[Piero]

I'd be tempted to throw it away ! 

Just kidding! Yes, I think it can be repaired in the way you suggested. You would need to make a new thread and use a slightly larger screw. 

Feel ashamed to admit though that I don't have the tools and practice to do that..  I will check whether there is a place where these things can be done though. 

Thanks for your advise James 

[YKSE]

Here's a page in TS about the Baader diagonals they have:

http://www.teleskop-express.de/shop/index.php/language/en/manufacturers_id/5/filter_id/9/astro/Baader.html

The ones with T2 connections work for 1.25" eyepieces without reducer. Here's a Baaders schema for T2 system

http://www.baader-planetarium.de/sektion/s08/download/t2-system-grafik-en.pdf

To my eyes, the T2 and SC connection systems are the beauties of excellent engineering work.

[Piero]

They definitely know the meaning of versatility! 

Thanks for the links YKSE! I will consider it those too!

[faulksy]

i had the revalations diagonal with quartz glass and found it good, i then changed to the baader click lock that was amazing. nothing between the views but a lot more secure and it centralises the ep.

[triton1]

I agree with jamesf tap it out bigger and replace with thumb screw also smooth off end to minimalize any marks on ep

[Moonshane]

If you want me to do the repair, sent me a pm and as long as you cover postage both ways I will do it for you. It's a 10 minute job.

[Piero]

Thanks so much everybody for your suggestions and help! 

@Moonshane: VERY kind of you to offer your help

I see if I can repair it here in Cambridge and then decide what to do. 

p.s. this community is just great!

[Piero]

An quick update about this. 

In my last trip to Italy, I found and bought a Tele Vue Diagonal Everbrite 1.25". 

My Revelation Diagonal Quartz 1.25" is in Italy now and will be repaired in the future. 

I just thought to give a quick comparison between the two. 

1) Cost. Well this is quick. The TV everbrite costs 3 times more. 

2) Optics. As far as I can tell, and reported by many other, I don't see any difference between the two. I knew this already and optical quality was not the reason why I decided to buy this diagonal. 

3) Mechanics. The TV Everbrite body is built from a unique block of aluminium. To me, it seems slightly lighter than the Revelation diagonal. Anyway, the body of the TV Everbrite seems to me much more solid and designed to last. The screw and the screw hole are also well made. Tele Vue quality is there as expected. 

4. Something that I thought about quite a lot and eventually made me opt for the TV Everbrite rather than repair my Revelation, is the different length of the eyepiece barrel holder. Between these two models, the TV Everbrite has a much longer path than the Revelation diagonal (about 1cm). If a barlow/telextender, such as Bresser SA 2x, is used with the TV60, a relatively long in-ward refocusing is required. Unfortunately, this is longer than the length of the TV60 precise helical focuser, obliging to re-focus with the coarse focuser. The higher the telescope is pointing, the more problematic this action is, due to the weight of the combo diagonal+barlow+eyepiece. With the TV Everbrite, the Bresser SA 2x enters almost completely making the eyepiece+barlow almost parfocal to the eyepiece only. Of course this might be a specific problem when using this setup with the TV60. In any case, this issue is solved by the TV Everbrite. 

Due to points 3 and 4, I have to say that I am very happy with it. I only regret I did not buy one last year, although it happens to replace part of our equipment with something better. 

[michael.h.f.wilkinson]

I do not think you will regret your choice. Machining the diagonal and barrels out of a single piece of aluminium means that the 1.25" push fit barrel attaching the diagonal to the focuser cannot unscrew. I have seen the latter happen with diagonals with a barrel which is screwed into the mirror housing. That can result in nasty accidents with heavy EPs crashing to the ground

[John]

I had just the issue that Michael describes happen not too long ago. Fortunately I spotted it before an expensive eyepiece was dumped on the ground. I have a couple of TV Everbrights now.

I'm sure you will enjoy using yours Piero.

[Stub Mandrel]

A tap to tidy up the crossed thread won't cost you much.

[russ.will]

But it shouldn't cross thread and Jam. My 1.25" Rev did and TH replaced it under warranty. This one has been flawless.

Russell

[djhartist]

Exactly the same thing happened to my rev 1.25 quartz diagonal a few days ago, screw got jammed for some reason though it was working a few nights before ok. Now it's broken like the OPs.

Quite frustrating and am using eyepieces loose in it. Not ideal certainly as it's a few months old and not used that regularly. It's interesting to note that it has occurred to other folk, I think I'll get in touch with TH first, then consider retapping if necessary.

Have had a minor eyepiece spree recently and need to replace mount sometime soon, so don't really want to have to buy a new diagonal just because of a silly screw - even tho the TV could b nice, having just got my first couple of TV plossls and realizing what the fuss is about re quality!

No complaints about the optical quality of the revelation diagonal tho.

( Sometimes it just seems to me that some mechanical parts of various equipment aren't as well made as could be, presumably to keep costs down and production up, but that's another debate!)

Sent from my HTC Desire 500 using Tapatalk

[Piero]

Sure, the damage of the screw thread can be repaired relatively easily. 

However, if you put expensive eyepieces into your diagonal and this gets damaged so easily and without a bad use, you quickly lose confidence about the quality of this piece of equipment. 

Personally, I do not trust it. I might have been unlucky of course, or maybe the 2 inches model is better built (I don't know), but I do not feel comfortable with the idea that one of my eyepiece could fall on the ground because of a potential fault in the diagonal. I prefer to spend a bit more and don't bother about these issues. Of course this is only my opinion.

The longer eyepiece barrel supporter of the TV everbrite 1.25" is generally not considered as a factor by people, but it should, especially if one is using it with a barlow/tele-extender. Another strength is the design from a unique block of aluminium preventing the diagonal barrel to unscrew when fitted in the focuser as Michael reported. 

Again, to me, there is no point in investing in high quality / expensive eyepieces and saving money in what holds them. 

Good optics are important, possibly crucial, but a good supporter, whether this is a mount, diagonal or a focuser, is important too. 

Having said this, I do not want people to think that they need an everbrite because their revelation diagonal is faulty. This is not true. The optics of a revelation diagonal are really good to me and I actually cannot spot any difference against an everbrite (with my limited experience of course!). I only hope that with this thread people are aware of the pros and cons of this diagonal in order to make their own sensible choice. 

If I used lighter and cheaper eyepieces (<£80-100) and did not use a long barlow, tele-extender, or powermate, I would possibly repair mine and continue using it.

[Stub Mandrel]

I wasn't justifying it, just thinking the OP might want a cheaper solution than a new diagonal,

FWIW cross threading is almost always caused by a screw going into a threaded hole at an angle, stripping of the thread is usually caused by overtightening but can be caused by the thread form being too shallow or not engaging correctly.

If these diagonals are consistently stripping then that probably means the holes are being tapped with an oversize tap OR being drilled too large before tapping. Alternatively the screws have either a too fine thread (fine threads in alloy strip easily) or too coarse a thread (not enough turns of thread for security).

A temporary fix can be putting a bit of PTFE tape on the screw. Permanent fix is to retap properly for a larger screw or tap for the original screw in a new place, noting that ideally any replacement screw should have a similar pitch to the original screw.

[Dave In Vermont]

May I make a suggestion to all? Try Nylon-screws instead if you're using a diagonal without a compression-ring. Nylon won't mundge your EP-barrels.

My personal favorite diagonals are the dielectric 2" William Optics. I better prefer them - I have three of 'em. For a 1.25" diagonal, I got a GSO dielectric with compression-ring. It's a sweet little thing, and the price is quite agreeable. Can't find Nylon screws? Drop me a pm and I'll give you a link.

No Chiropractor needed,

Dave

[Stub Mandrel]

I got 10 nylon M6 screws off the 'bay for my home-made guide-scope mount for about £3.50. I saw smaller sizes while searching.

[Dave In Vermont]

ScopeStuff is located in Texas. If it's weird, something you never knew existed, or something you can't live without:

http://www.scopestuff.com/

As for Nylon screws:

http://www.scopestuff.com/ss_nscr1.htm In inches.

http://www.scopestuff.com/ss_nscr2.htm in metric.

Beware: You can easily spend days wandering around in this site.

Best -

Dave

[Dave In Vermont]

That's odd. Let's try those links again....Metric:

http://www.scopestuff.com/ss_nscr2.htm

And inches:

http://www.scopestuff.com/ss_nscr1.htm

Dave

P.S. Phew!