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Olivon T55 spotting scope.

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#1 Adun

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Posted 12 January 2020 - 04:48 PM

This is an odd question:

 

* It's about daytime use (birding)

* It's about a budget conscious purchase (odd for the refractor forum)

 

So here it is:

 

This chart has been posted here often, about achromats:

post-2597-14073834301145_thumb.jpg

 

I'm looking for a lightweight spotting scope for birding, and I don't have deep pockets. No Swarovskis / Zeiss for me, please. Heck, not even celestron regals. ... Which is hard in a world where even the $300 Celestron Hummingbird ED gets bad performance reviews. See: it's tough being F4, whether ED or not.

 

My C90 is both too heavy to take to the field, and too high power to use on my balcony. My only refractor (F4.4 80mm achromat) is lightweight but has terrible CA for daytime use (I tried). Hence, the search for a decent budget spotting scope.

 

I have found something attractive: Olivon makes a $129 spotting scope called the T55, with a 55mm objective, and apparently 380mm FL (which makes it F7). It comes with 18x-54x zoom (7-21mm), but it also takes normal astro 1.25 eyepieces.

 

olivon_olt55_us_t_55_angled_spotting_sco

 

So it's a little odd for a spotting scope, see: it's still quite light, despite being somewhat long compared to the Celestron Hummingbird or the typical ~50mm to 60mm spotting scopes.

 

But I see potential in it:

* Being F7, perhaps CA is not much of an issue, despite the lack of ED glass, specially for a 55mm aperture. The table above suggests so.

* Supporting 1.25" astro eyepieces let's me worry less about the quality of the included zoom. If needed for better performance or wider fields, my Baader or Celestron zooms could  be called to help, as would my other eyepieces.

 

- One big con is that its not Waterproof / Nitrogen sealed, no not fogproof either, which I've come to value on my birding binos, but for the planned use case, this wouldn't be a problem.

 

So, I'm thinking about pulling the trigger on this $129 spotter. It's a lot more appealing than a $100 Chinese 

 

If refractor aficionados can enjoy the planets with F11 achromats, maybe I can enjoy birds with an F7 !

 

 

... Unless, there's something I'm missing, which is why I'm posting this: Perhaps you can advise me better... Show me the error of my ways, and the holes in my reasoning!


Edited by Adun, 12 January 2020 - 04:53 PM.

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#2 junomike

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Posted 12 January 2020 - 05:33 PM

One thing that might help with CA also is the use of a Prism. Being 1.25" compatible is nice however some EP's may not reach focus. 

For the cost It looks like a decent option/



#3 gene 4181

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Posted 13 January 2020 - 01:23 AM

   Get it !    You'll need a tripod  though 


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#4 Jon Isaacs

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Posted 13 January 2020 - 07:50 AM

So, I'm thinking about pulling the trigger on this $129 spotter. It's a lot more appealing than a $100 Chinese

 

 

For what it's worth:  I think Olivon is made in China. 

 

I've had a few entry level spotting scopes.  Generally they do quite well and the chromatic aberration is only noticeable under certain high contrast situations, a black bird or power wide against a bright blue sky, the CA is visible.  Otherwise it's masked by the surrounding field.  I had a Tasco 60mm, it did OK.  

 

But here's a thought, your 80mm is F/4.4, that means it has a 350mm focal length.  It has a chromatic ratio of 1.4, lots of false color.  

 

But if make a 55 mm aperture mask for it, it will have a chromatic ratio of 3.0, very similar to the Olivon. You could even make a 40mm aperture mask and and the chromatic ratio would be about 5.5, very apo-like.  

 

It might be just a test to see how the Olivon would work but it also might be a solution to your spotting scope needs.

 

Jon


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#5 Adun

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Posted 13 January 2020 - 08:54 PM

   Get it !    You'll need a tripod  though 

 

I already have an Orion Tritech II that'd work great!

 

 

 

But here's a thought, your 80mm is F/4.4, that means it has a 350mm focal length.  It has a chromatic ratio of 1.4, lots of false color.  

 

But if make a 55 mm aperture mask for it, it will have a chromatic ratio of 3.0, very similar to the Olivon. You could even make a 40mm aperture mask and and the chromatic ratio would be about 5.5, very apo-like.  

 

It might be just a test to see how the Olivon would work but it also might be a solution to your spotting scope needs.

 

 

Good idea. I wouldn't be able to bird with it because the diagonal is astro 90° (inverted view) and it has an odd visual back (Orion GoScope) that won't take other diagonals.

 

But it would allow me to test how ~55mm F7 looks like, and decide whether I like it enough.



#6 russty55

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Posted 13 January 2020 - 09:56 PM

I have one, I use it as my spotting scope in my sport of target shooting. Absolutely satisfied with the sharpness and clarity this 'scope provides.


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#7 Jon Isaacs

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Posted 13 January 2020 - 10:40 PM

I already have an Orion Tritech II that'd work great!

 

 

 

 

Good idea. I wouldn't be able to bird with it because the diagonal is astro 90° (inverted view) and it has an odd visual back (Orion GoScope) that won't take other diagonals.

 

But it would allow me to test how ~55mm F7 looks like, and decide whether I like it enough.

 

I do my birding with star diagonals.. 90° , correct up and down, reversed left to right. It's no biggie.

 

Jon


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#8 Adun

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Posted 15 January 2020 - 12:30 PM

I do my birding with star diagonals.. 90° , correct up and down, reversed left to right. It's no biggie.

 

Interestingly, I did feel kid of odd when I checked my C90 with the erecting diagonal on the balcony. Something about left-right movement feels odd, probably because I've gotten used to astro movements, so I get what you mean.

 

 

However, my wife would be using this at least half of the time, and I'd rather give her erect "natural" views.

 

I just ordered this, so once I get it (which will take a while), and have had some time with it, I'll be posting my opinions.



#9 Adun

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Posted 23 February 2020 - 11:10 AM

I finally got hold of the Olivon T-55.

 

First the bad news: contrary to what's stated on bhphotovideo.com, it does not accept regular 1.25" eyepieces, which is a big let down. I'd consider returning it, if I wasn't an international customer.

 

Luckily, if I remove the 1.25" barrel of my Baader zoom, it's inner barrel does fit somewhat snuggly, although there is no way to secure it in this setup, so not really suitable for carrying on birding hikes. No other eyepiece I own fits.

 

I just tried it on daylight with the Baader zoom, and I like the color rendition of the T-55, which was a major concern for the birding intended use. A dark leaf against a white background is very sharp and no CA at the lower half of the Baader zoom's power. The higher half of the zoom, as it approaches 68° AFoV while depth of field shrinks, the edges start showing field curvature (to be expected at this 380mm FL), plus a hint of CA (yellow to me) in the outer 15% of the FoV, although the center remains good. At highest power, between the ~1mm exit pupil, shallower depth of field and the dimmer image, the overall impression is "Not as tack sharp" as low power, but I found it to be reasonably good. 

 

The included eyepiece is a tiny & lightweight 7-21mm zoom. The same daylight test shows a slight reddish edge of field brightening at 18x right at the edge of the field stop, which disappears at around 35x. It's not bothersome to me, but it's there. It is quite parfocal throughout the whole range, which was very pleasing. The eye relief is super comfortable at lowest power (18x) but shrinks as you zoom, and above ~30x I have to remove my glasses to see the whole AFoV, and to even use it at 54x.

 

That FoV is very narrow. 30° at 18x and 43° at 54x. Using it right after the Baader makes the narrowness of it's field of view quite apparent, but I have to admit I like this tiny zoom more than I expected I would. 

 

Overall, this F7 55mm refractor is definitely a better birding scope than my C90, and for half the price of a Baader zoom, Olivon has assembled a neat package, kudos to them.

 

Thumbs down to bhphoto for falsely advertising that "If the included eyepiece is unsuitable for the viewing task, a 1.25-inch eyepiece mount allows the observer to use almost any astronomy eyepiece". As a matter of fact, it does not.


Edited by Adun, 23 February 2020 - 11:29 AM.



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