What Diagonal?..

[Paul73]

Hi Guys

I’ve just “accidentally” bought a Skywatcher ED 72mm APO. Having just collected 3 ES 82° eyepieces, today is a good day!???. However, this little lovely doesn’t come with a diagonal, so I need to buy one.

I’ve never bought a diagonal before. It will be visual only, using 1.25” and 2” eyepieces and shouldn’t cost the earth. Any recommendations for a good budget item that would fit the bill?

Paul

[Piero]

I love my bbhs but that is not cheap. 

s/h TV Eventbrite?

[Louis D]

I like the GSO (Revelation) dielectric 2" diagonal so much, I have two of them.

[Ruud]

I have two 2" diagonals, a TeleVue a William Optics, and I can't see the difference. I also have two 1.25" ones by William Optics, and they seem just as fine.

Dielectric diagonals have my preference. You really don't have to worry about cleaning: there is no delicate coating that you have to be careful with.

A dielectric layer is very hard, scratch resistant and will not dull after repeated cleaning.

 

[Doc]

The Baader ClickLock 2" DiElectric Star Diagonal is an awesome piece of kit and you will love the ease of the clicklock.

[Ben the Ignorant]

For a semi-apo this violet-reducing diagonal is best optically but it's currently out of stock:

 

 

https://www.365astronomy.com/365Astronomy-2-99-Dielectric-Deluxe-Mirror-Diagonal.html

I don't know if your optical tube was delivered with a 1.25" adapter; if it's not the diagonal can be had with that adapter for 10€ more. However you might insist on a click-lock system or a particular look; so the others are good choices, too, especially if the 365 diagonal can't be restocked soon. The APM equivalent does have a standard click-lock attachment but they charge a lot more.

https://www.apm-telescopes.de/de/optisches-zubehoer/zenitspiegel--prismen/apm-2-zoll-zenitspiegel-schnellverschluss-99--di-elektrischer-verspiegelung.html

[Paul73]

I’ve just Googled ‘Dielectric’. I’m really none the wiser. 

Does anyone know the difference between Dielectric and Non-Dielectric?

Paul

[Doc]

The newer dielectric diagonals have a harder surface so the mirror doesn't deteriorate like the older versions did. It also is meant to produce less light scatter.             

[Prador]

This Wikipedia page explains different applications for dielectric coatings:

https://en.wikipedia.org/wiki/Optical_coating

I've learned something new today  

[Paul73]

8 minutes ago, Prador said:

I've learned something new today  

Me to! Thanks.

Dielectric all the way!

[Green12]

I use Antares 2inch  twist lock dielectric diagonal from RVO. Comes with 1.25 adaptor about £90

[Louis D]

35 minutes ago, Paul73 said:

Does anyone know the difference between Dielectric and Non-Dielectric?

Non-dielectric include aluminum, enhanced aluminum, and silver mirrored surfaces.  Then there are the prism based diagonals which don't use a mirror at all.

[Ruud]

Dielectric mirrors do not use reflective materials. No aluminium, silver or whatever.

They rely on constructive interference from many thin, transparent layers. Fifty or more transparent layers.

Reflectivity is typically 99%.

 

[Sunshine]

My william optics dielectric 1.25 is great and, it doesn't break the bank.

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