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Three diagonals - which will triumph?


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That is unfortunate but one slips past QC occasionally.

A few years ago I decided to purchase my first premium diagonal. For almost € 400 I got a lump of metal that was unusable. 

The lines you see in the image go across the entire mirror. It serves as a expensive dust plug for my 150 mm f/8

 

IMG_5131.jpg

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I sent it back to the company for inspection and it was returned to me with a note saying it was within specifications.

I do not think they bothered to look through it, if they had they could not have missed all the scatter from it. 

 

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1 hour ago, happy-kat said:

@ags does the eyepiece holder end of the celestron erect diagonal unscrew please? 

No, seems to be fixed. Which I like.

59 minutes ago, Mr Spock said:

Shame about the screw position. You are never going to get wide body eyepieces to fit without an extension tube.

I can solve this with the right screw heads.

41 minutes ago, johninderby said:

Have one of the Omegon amici prisms. An excellent bit of kit.

https://www.omegon.eu/amici-prisms-90d/omegon-1-25-amici-prism-90d/p,14172

Looks nice, I think FLO also sell this under StellaSomething branding.

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I had another look last night. No time for side by side views with the mirror diagonals, but I got an excellent view of M57 and Albireo. I also confirmed the double split on Epsilon Lyrae and the absence of false color when slightly defocused (versus the strong false color seen with the mirrors). Star fields were very sharp when browsing 2.2° fields. 

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The Omegon prisim works great when used with my Lumicon Superfinder. So much better than one of those standard prisms. 👍🏻

Can highy recommend the Omegon or StellaMira prisms.

ACBFA2F9-ACEF-4FC5-AA5E-05B60B74C983.jpeg

Edited by johninderby
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Didn't think the one Ags got was erecting but a regular prism? 

The erecting one that came with the LT70 starsense was awful and a round plastic body rather than a prism shaped metal one with prism clamp set screws in the sides.

edit: ah looking at the FLO listing ok, erects but L-R reversed, fair enough

Edited by DaveL59
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1 hour ago, FLO said:

StellaMira 1.25" 90º Erecting Prism Diagonal

Looks interesting - might have to think about one. It would make double star observing in the 102mm better. My impression is that it is a RACI prism.

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Posted (edited)

I find I can flip left-right when looking at a double, but not when looking in a finder scope. I suppose with the double, I know what I am looking at, but in the finder I  am trying to recognize star patterns and flipping and rotation is too much math... So my finder is a RACI but the main scope has a simple prism not an amici. Not a fan by the way of the diffraction spikes caused by an amici, which would be very visible at higher magnification.

Edited by Ags
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3 hours ago, FLO said:

 

StellaMira 🙂 

StellaMira 1.25" 90º Prism Diagonal

Steve

Is StellMira your house brand for Long Perng products while StellaLyra is your house brand for GSO products?  You've got to admit that using two such similar sounding names is a bit confusing.  Did the two companies object to making products using the same branding, so you had to come up with two different brands?

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28 minutes ago, Louis D said:

Is StellMira your house brand for Long Perng products while StellaLyra is your house brand for GSO products?  You've got to admit that using two such similar sounding names is a bit confusing.  Did the two companies object to making products using the same branding, so you had to come up with two different brands?

We have several in-house brands. 

StellaLyra telescopes are mirror-based (CC, RC, Newtonians & Dobsonians) so manufactured by Guan Sheng Optical (GSO). 

StellaMira telescopes are refractors so manufactured for us by Long Perng or United Optics. 

For SL and SM accessories and eyepieces we source from the same three manufacturers. (The StellaMira prism diagonal mentioned earlier in this discussion is manufactured by Long Perng). 

We are open and transparent regarding manufacturers. Here at SGL we credit the manufacturer whenever we introduce a SL or SM telescope. It is not a secret and we don't pretend to be an optical designer or telescope manufacturer 😇

We have good relations with all three manufacturers. They and we are delighted with progress. No objections of any kind 🤗

HTH, 

Steve 

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4 hours ago, Franklin said:

Is not this just the standard Celestron 1.25" Prism diagonal? 

Yes. Sorry. We have updated the product title 🙂

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1 hour ago, FLO said:

We have good relations with all three manufacturers. They and we are delighted with progress. No objections of any kind 🤗

Absolutely top notch manufacturers.  I have a lot of gear from all of them under various brand names and have been very satisfied with all of it.

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11 hours ago, Ags said:

Not a fan by the way of the diffraction spikes caused by an amici, which would be very visible at higher magnification.

Amici is ok for low/medium power terrestrial viewing. Best option is to learn yoga and observe Japanese style with nothing between the objective and eyepiece. I've been doing this up to about 35deg elevation with the Vixen flip mirror straight through. As soon as my neck starts to strain I switch the eyepiece over and flip the mirror. This way I can observe from horizon to zenith without adjusting my observing chair at all. I'm quite pleased I've actually found a use for the flip-mirror now, as I don't do imaging and have never tried it before because of this.

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Many years ago, I was looking for the best quality 1.25" diagonal I could find for a 5" Maksutov, and tried the Celestron prism star diagonal,

along with TeleVue, Lumicon, Takahashi, and GSO offerings, all 1.25".

It was a fairly recent version, with a multi-coated prism and a full clear aperture all the way through.

I was surprised to learn it was the optical equal of the very best dielectric mirror diagonals--indistinguishable in brightness, sharpness, or contrast.

Yet, it was 1/3 to 1/6 the price of the others.

I didn't go with it only because some of my eyepieces wouldn't fully insert in the diagonal--they were blocked by the prism.

But, in terms of optics, that one was a real bargain.

 

I'm not sure whether I could trust the plastic prism housing to hold a 1-1/2 pound eyepiece without breaking in the long run, but for lighter eyepieces, it is STILL a bargain.

Is the one from FLO threaded for filters?

Edited by Don Pensack
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  • 2 weeks later...
On 25/06/2022 at 02:03, Ags said:

Today I became the owner of three diagonals after a cheap Celestron 1.25” prism diagonal joined my TS dielectric diagonal and a SkyWatcher starter diagonal that came with a Skymax 102 (both 1.25” diagonals). 

Hi, I'm new to this hobby, I bought a telescope with a very cheap and poorly made diagnoal (?) that is made of plastic, it's the celestron dx102az. I was told I should upgrade it to get better result, someone tipped me about your post. Is the diagnoal you got similar to these ones?

Celestron 90° Star Diagonal (1.25") 94115-A B&H Photo Video (bhphotovideo.com)

Teleskop-Express: Celestron 1,25" 90° diagonal prism for refractors and cassegrains

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