Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Dielectric diagonal - worth the upgrade?


scoobymike

Recommended Posts

Hi,

I have a skywatcher 127 MakCass, and am waiting on some new EP's and finderscope to arrive. So, as you do, I've been looking at what else I can buy for my 'let's go cheap and see how I get on with it' starter scope :) I can pick one up for around 60 quid, from several different manufacturers. Not sure the variety will make much difference?

So my question is would it be worth buying a spangly new dielectric diagonal (after all, the blurb says 99% vs 90% light transmission, and I believe everything I read :icon_scratch:), or is this really money NOT well spent? I am planning on keeping the scope regardless of whether I end up getting a bigger aperature later, so it is long term, but I'm unsure as to whether there really is any benefit. Anyone have one?

Conjecture as welcome as actual experience!

Mike

Link to comment
Share on other sites

Some may argue that they can't really see the difference optically but it's about the build quality as well. A better quality diagonal with it's higher build quality should be properly collimated and have a brass compression ring for clamping the eyepiece. The quality of the the cheap standard diagonal (particularly the mounting of the mirror) is a bit variable so you may get a good one or maybe not. Also the dielectric coatings last a lot longer and are tough enough to stand up to frequent cleaning. BTW If you have a prism diagonal they aren't too good at higher magnifications.

I did notice a a bit brighter image using the dielectric diagonal.

John

My 127 Mak with William Optics dielectric 1.25" diagonal.

Link to comment
Share on other sites

Thanks John,

My current diagonal seems to be ok, but I guess it's a question of 'pimp my ride' :icon_scratch: I'm in Surrey and LP is bad, so it's a drive to a darker site and portability limits my choice in terms of outright OTA size. Ergo gotta get the best from what I have. Maybe I should order one and return if not happy (long distance selling regs et al)?

BTW nice pic of your set up. What's the dew shield made from? I asked in a previous post and most common solution was a camping mat rolled up which is easy, but yours doesn't look like it's one of those..

Mike

ps Your gnomes appear to have made a run for it.... :)

Link to comment
Share on other sites

I bought one mainly because it offered me some reassurance when I need to clean it that I won't be damaging it in the process. Optically is it worth it? Well in astronomy there is a view that 'every little extra helps' though you might have to pay a disproportionate amount extra to secure this slight improvement and it's the same when considering eyepieces.

Like a lot of people, I have been seduced by a certain 2" carbon fibre version which I bought out of vanity and not for technical reasons. To that end I would say that if you were to buy one, I do not believe that 99% reflectivity of a top end manufacturer is any better than 99% reflectivity of a cheaper brand (...the carbon fibre look is a bit moorish! :)) so I WOULD buy one but don't pay anymore than you have to.

James

Link to comment
Share on other sites

I've tended to upgrade diagonals from the standard ones to dielectrics, preferably 2" ones, on the basis that "every little counts". Having now moved to heavy eyepieces (Ethos + Naglers) I feel more secure when the eyepieces are retained in a solidly built diagonal as well. I currently have Tele Vue Everbright and Revelation Dielectric Quartz 2" diagonals. The optical performance is very similar but the Everbright is a little better engineered than the Revelation, being machined from a single block of alloy. Both seem to be secure places for my heavy eyepieces though :)

Link to comment
Share on other sites

Ive been using Everbrights for some time now, and found them to be markedly better than the orignal prism that I had. Solid, well bult, and never come out of algnment (unlke a prism). One of my better purchases.

Link to comment
Share on other sites

I have the Sky Watcher one and confirm that the build quality is usually much better, especially if you use heavier ep's as I do, the compression rings are also a boon if you have an expensive ep on the mount. Link: First Light Optics - Skywatcher 2" Deluxe Di-Electric Star Diagonal

This diagonal is cracking quality and feels like it. Comes with a 1.25" convertor as well, not obvious from the photo.

Link to comment
Share on other sites

The William Optics 1.25" Diagonal has a thick safety stop that vignets some eyepieces, plus it has some internal reflections which I felt were troublesome. I bought the Revelation Quartz Dielectric 2" which blew me away with its quality - that one's a keeper for sure.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.