Star Diagonal?

[Syzygy2011]

I have the Celestron CPC 9.25. It came with a bog standard 1.25" star Diagonal # 94115-A. I've just recently purchased a new Baader Mk III Hyperion 8-24mm Zoom eyepiece.

Seems the Star Diagonal and Hyperion clash when it comes to fitment? When the Hyperion is inserted into the Diagonal, the tightening screws of the Diagonal fit against the body of the eyepiece making it really difficult to tighten.

I've decided to start looking for a new Star Diagonal, one that is 1.25" and 2" compatible. I've about £150 budget to purchase one, and there seems so many out there?

Any suggestions what would be good value for money in that price range? Also bearing in mind I don't encounter the same problem with the tightening down?

Thanks!

[aussi skywatcher]

Hi, I had the same problem with the Hyperion Zoom the screw on the diagonal just caught on the edge of the locking ring of the eyepiece. I looked around my gear and found a screw that was a bit longer then the original and I then very carefully ground a taper running back from the threads to approx half the length of the knurled part - this worked fine - am happy to post a photo if you wish

Cheers Paul

[Syzygy2011]

Hi Paul!

Yes if you could please... Then I can see what needs to be done. I can then use this Star diagonal for the 1.25" 's and save me having to change things round all the time as I have some eyepieces that are only 1.25"

Cheers mate!

[michael.h.f.wilkinson]

I put a Baader 2" visual back on my C8, and added a WO 2" diagonal (99% dielectric, for 99 euro). Well worth the investment.

[Syzygy2011]

That's a good price Michael... I assume it's the non quartz? I've been looking at the WO 2"... is there a lot of difference between the two? (apart from the price?) !!

[michael.h.f.wilkinson]

It is the non quartz. The quartz will have the lower thermal coefficient of expansion, but I do not know what the impact of that is on visual observing. The optical accuracy of the surface may be higher, but I must say I am very happy with the one I got. Incidentally, there are now much cheaper 2" visual backs floating around (Teleskop Service has one). I have seen them as cheap as 29 euros.

[Syzygy2011]

The One I have been looking at is at FLO... It already has the SCT adaptor included at £115. The quartz WO is a bit pricey at £229... a big difference in price! As for difference in visual observing I guess some of that is mostly in the hands of nature!

[johninderby]

I use the Baader 2" visual back on my C8 and can highly recommend it. The cheap visual backs do work but they don't clamp as well as the Baader which uses higher quality materials (the clamping ring is much thicker and made from a stronger material). The Baader also seems to clamp every diagonal I tried in it perfectly. Some of the cheaper visual backs don't clamp the diagonals with a "WO" type tapered nosepiece as well.

I picked up a new unused SkyWatcher 99% dielectric 2" diagonal for £40.00 on Astrobuysell so you can get lucky and find some real bargains occasionally. Seems to work as well as a WO one.

John

[Syzygy2011]

Hi John,

I shall need a 2" Baader Visual Back for the WO 2" Diagonal I have decided to purchase? Just Googled and Looked in the online stores for one... can't seem to find one? Are they rare as hens teeth or will I need to import?

[johninderby]

Here you go.

http://www.firstlightoptics.com/adaptors/baader-sct-to-2-inch-adapter.html

John

[great_bear]

The Revelation(GSO) Quartz Dielectric 2" Diagonal - at under £100 - is a top-quality bit of kit which made a genuine difference to the quality of my views.

[Syzygy2011]

Thanks John,

Is this the new design, the one I was looking for is this one in the picture?

Cheers!

[johninderby]

I see the one in your pic is the 2" Clicklock. as here.

http://www.365astronomy.com/2-clicklock-clsc-eyepiece-clamp-for-sc-telescopes-p-1911.html

Actually I prefer the standard one I mentioned earlier. I have one of the 2" Clicklocks on my Baader Hershel wedge and I'm seriously thinking of replacing it with the standard one. I prefer the more controllable clamping action of the standard one and I just don't like the way the Clicklock can suddenly unlock if you accidentally bump it.

And also there's the price difference.

John

[Syzygy2011]

I see your point John, I'm clumsy at the best of times... even worse in the dark!

Thanks for all your advice..(and that includes everyone!)

I shall go have a cup of tea... and give all this some deep thought before i decide!

Gerry.

[Syzygy2011]

The Revelation(GSO) Quartz Dielectric 2" Diagonal - at under £100 - is a top-quality bit of kit which made a genuine difference to the quality of my views.

Thanks great_Bear... another one to ponder over. I'm kind of edging toward the quartz mirror.... as Michael posted something to do with the lower thermal coefficient of expansion.. giving greater optical accuracy?

Gerry.

[johninderby]

I've compared the WO and the Rev Quartz and they are very, very similar in performance, although the WO seemed to be a bit better made. I couldn't detect any difference in the "thermal stability" of the Rev quartz compared to the WO. They're both great choices in a diagonal.

It's worth reading this thread on Cloudynights.

http://www.cloudynights.com/ubbarchive/showflat.php/Cat/0/Number/1887153/page/23/view/collapsed/sb/5/o/all/fpart/1

John

[Syzygy2011]

I would tend to agree john. The Rev Quartz is milled out of a solid block of Aircraft grade aluminum, whereas the WO is carbon Fibre and made from several parts? I guess it would be easier cleaning with the WO's not sure about the Rev's (there seems to be access points via the scewed base??) but I think I will go for that and a filter too!

[johninderby]

The Rev is not made from one piece of aluminium. You're not going to see that at this price level. The nosepiece and eyepiece holder are separate parts that screw into the body. As proof they sell replacement nosepieces to fit the Quartz diagonal.

http://agenaastro.com/gso-chrome-barrel.html

The WO is also made from aluminum and then the CF side plates are screwed onto the side so the CF parts are only decorative.

BTW I've never needed to remove the side plates or botomplate of a 2" diagonal for cleaning as there's enough access through the nosepiece and eyepiece holder to clean the mirror.

John

[Syzygy2011]

The Rev is not made from one piece of aluminium. You're not going to see that at this price level. The nosepiece and eyepiece holder are separate parts that screw into the body. As proof they sell replacement nosepieces to fit the Quartz diagonal.

http://agenaastro.com/gso-chrome-barrel.html

The WO is also made from aluminum and then the CF side plates are screwed onto the side so the CF parts are only decorative.

BTW I've never needed to remove the side plates or botomplate of a 2" diagonal for cleaning as there's enough access through the nosepiece and eyepiece holder to clean the mirror.

John

OK Thanks.... I've read so many reviews this afternoon, not sure whether I'm on Planet Earth or Mars! Lol..

[great_bear]

I clean my Rev (albeit very rarely) by unscrewing the base. The mirror comes out as a beautiful solid glass block. I can then look really low across the surface to ensure there's no grit or other nasties before giving the surface a single, gentle wipe across the whole surface in one go.

You'll be impressed with the both the build and performance of the Rev /GSO diagonal.

(and for the price - it's amazing!)

[Syzygy2011]

I clean my Rev (albeit very rarely) by unscrewing the base. The mirror comes out as a beautiful solid glass block. I can then look really low across the surface to ensure there's no grit or other nasties before giving the surface a single, gentle wipe across the whole surface in one go.

You'll be impressed with the both the build and performance of the Rev /GSO diagonal.

(and for the price - it's amazing!)

Received the Rev 2" this morning! Very impressed... made a right Boo Boo though! The fitment for my CPC on the Diagonal goes straight on the back of the scope, and I have ordered the Baader 2" Deluxe Clamping eyepiece holder which the Rev fitment won't go into!!

Revelation (GSO) 2" Quartz SCT fit deluxe CNC mirror star diagonal

I should have ordered the Rev 2" with the push in chrome tube like this one....

Revelation (GSO) 2" fit deluxe CNC mirror star diagonal

If anyone has a chrome tube they don't use that will fit the 2" Diagonal...please let me know, as I would much rather use the Diagonal with the Baader Clamping eyepiece?

I am told that you cannot buy these chrome tubes separately??

Cheers!

[johninderby]

Don't know of anyone selling the replacement push fit nosepieces here in the UK but Agena Astro in the US sells them.

http://agenaastro.com/gso-chrome-barrel.html

John

[great_bear]

I am told that you cannot buy these chrome tubes separately?

Well you can - but it would be cheaper to just return the diagonal for replacement with the other one.

You're legally entitled to do so. SnS won't object. Phone them first though!

[m.tweedy]

why do you not just screw the diagonal into the back of the tube. That is what the one you have is designed to do. It cuts out the middle man of the visual back.

[Syzygy2011]

why do you not just screw the diagonal into the back of the tube. That is what the one you have is designed to do. It cuts out the middle man of the visual back.

I could, but.. for ease of use and storage If I use the Diagonal attachment it means having to unscrew it every time when I am finished and it is very fiddly considering the weight of the Diagonal?

Whereas, if the Baader Clamping eye piece was left in place, all I do is slacken off the two pressure screws remove the Diagonal and just place a dust cap over it and then it can be left in place permanently?