Tecnosky 125/975 F7.8 FPL-53 Doublet APO - First Look

[JeremyS]

Great image John 👍🏻

[johninderby]

16 minutes ago, JeremyS said:

Great image John 👍🏻

If only it was mine. 😢

[johninderby]

Waiting for the moon to clear the big tree at the end of the garden.

[johninderby]

So much for the clear skies. Lots of cloud around earlier but now just very hazy so not much to look at except for the moon. Had chance to try a variety of eyepiecehs and a Baader prism and a WO diagonal. Seemed to be a tie between the diagonals. 

However views of the moon were very impressive. Very sharp and contrasty images and showed a lot of detail. Tried the Vixen HR 3.4 and and very impressed. Definitely the most detail and contrast compared to the other eyepieces thatI tried. Think I could do with the 2.4 HR. 😁

With the 3.4 floaters were a slight problem but not a big deal.

Early days yet but very impressed with the scope. Not the slightest trace of CA which is what I expected though.

 

Edited February 25, 2021 by johninderby

[Voyager 3]

How are the ergonomics of the scope mounted on the mount John ? Is it a bit on the heavy side ? Finish looks awesome 👍 .

[johninderby]

The scope isn’t heavy for a 125mm APO really. Only 7.6 kg without diag so easy to carry and fit to the mount. Easy to balance the scope on the AZ100 mount which is capable of handling a far bigger scope than the 125. Fitting a carry handle is a good idea though. All scopes should come with a handle.🙂

Edited February 26, 2021 by johninderby

[alex_stars]

First review from first light yesterday night which was a success.

First off, maybe a word on what is my baseline to compare. I worked a lot with a Skymax 180 the last year and had a William Optics Fluoro Star 110mm f/7 Triplet Apo for a few weeks now borrowed from a friend (to get into APO mood). The 127 mm TS/Tecnosky is a Doublet with FPL-53 / Lanthan and I don't know the glass types of the WO. All mounted on a Celestron AVX with two counterweights. All observations below were done with a TS 1.25" diagonal (99% reflection - 1/12 lambda)

Seeing was rather good early in the night and got a bit worse later on (as you will see which double stars I managed to split). Sahara dust was mostly gone from the air and it did not bother the observations.

First I took a close look at the moon, magnifications between 65x to 305x. For an overview I took my 15 mm Vixen SLV in which the moon fits nicely at 65x. What a crisp picture with high contrast, even early in the evening. Motivated by that I took a closer look with my Hyperflex Zoom/Hyperion Barlow combo. The scope took the max 305x very well and I got very good views, even though the seeing did not really allow crisp views at that magnification. I was searching for CA but did not find any signs of it, 👍. I have to be honest I did expect some, given that the scope is a Doublet, but as @johninderby pointed out, no signs of it.

Next up was Rigel. Seeing was pretty good at that point and I managed to split Rigel and its companion (about 9.4" separation) at 219x (Hyperflex/Hyperion at 10 mm). Amazing!

Then I took a look at M45 - Pleiades with my 32 mm Plössl. They fit nicely into the view at 30.5x. A beautiful view. Swing over to M42 (Orion Nebula) to test the basic Deep Sky capabilities 😀. For a 5" scope I got very satisfying views. It's not meant to be a dedicated DS scope but it has its capabilities. Now that is not my field of observations, so I stick planets and double stars.

Mars was a lovely view, small but well defined. I tested the Hyperflex/Hyperion combo as well as my SLV 6 mm. All in all very satisfying views (seeing permitted). I instantly saw the potential for planets with this scope. Looking forward to the upcoming planet season.

Back to Rigel, but the seeing got worse, no way of splitting it now. So I went for Meissa. No problem there at 163x with the 6mm SLV. This EP will be my Jupiter setup and testing at Meissa (and earlier on Mars), the views very really nice. The SLVs have a wider view that the Hyperflex, that's why I keep those as my fixed FL EPs.

Motivated by @John recent post, I went for Sirius. Unfortunately the seeing was not as good as it was when I first went for Rigel earlier so no chance of splitting the "Pup". I ramped up magnification and looked for CA. Hard to tell with the seeing conditions but maybe a hint at 305x. That is with the HYperflex/Hyperion combo. Hmm. Either way, the possible CA was sooo minor that I would not worry a second about it. I want to re-check in better seeing conditions before I would dare a definitive statement. Took the chance and checked for collimation. Spot on. As expected. So I placed my virtual "Collimation OK" sticker on the scope to keep up with @johninderby scope. Have to say though that my scope was selected for me by my trusted dealer, so no surprise there. Still very satisfying.

To close the night I though I follow @Johns suggestion and had a go at Beta Monocerotis. At 163x (SLV 6mm) a prefect split of all three stars and a very worthwhile view. Satisfying finish of the evening.

To sum it up (after one night out!):

• Very solid mechanical built, focuser and all.
• The AVX carries it nicely for visual observations. I use a second counterweight though, that's more convenient.
• Did not find any signs of CA, so I am more than happy with my new doublet and that without a prism, TS diagonal just fine. So this graph (https://stargazerslounge.com/topic/371948-how-do-i-interpret-takahashi-diagrams/?do=findComment&comment=4038693) is basically telling me my scope is awesome.
• Very sharp, high contrast views, as expected.
• Magnifications up to 305x no problem at all. Maybe I should start considering shorter FL EPs (SLV down to 2.5? well at least down to 4).
• At 125mm it has enough punch to do some DS, but I have the scope for planets and double stars.
• I already really enjoy this scope...

That's all from the first night. More to come and looking forward read @johninderby first extensive report.

[johninderby]

Nice teport. 👍🏻

Pity the weather last night wasn’t good where I am. So much haze couldn’t even see Mars at all. 🤬 Hopefully will be better tonight. 🙏🏼

But despite the weather the moon was impressive particularly with the Vixen HR 3.4mm eyepiece. 

Was reading a German report on the scope that pointed out one interesting characteristic. Apparently these doublet optics are designed to optimise the green and blue wavelengths rather than the red as the eye is least sensative to red. However this can cause minor red fringing on bright stars and reduce contrast on Mars. Testing showed that by using a prism diagonal (Baader T2) which refracts red differently to blue and green it can cancel out the differences and get rid of any red fringing and increase contrast on Mars. Apparently the light path length of the prisim is important. Not sure how noticeable this would be in the real world but interesting nonetheless. Will have to compare views of Mars with a prism diagonal and mirror diagonal to see if there is any noticeable difference. 🤔.

Edited February 26, 2021 by johninderby

[alex_stars]

40 minutes ago, johninderby said:

Was reading a German report on the scope that pointed out one interesting characteristic. Apparently these doublet optics are designed to optimise the green and blue wavelengths rather than the red as the eye is least sensative to red. However this can cause minor red fringing on bright stars and reduce contrast on Mars. Testing showed that by using a prism diagonal (Baader T2) which refracts red differently to blue and green it can cancel out the differences and get rid of any red fringing and increase contrast on Mars. Apparently the light path length of the prisim is important. Not sure how noticeable this would be in the real world but interesting nonetheless. Will have to compare views of Mars with a prism diagonal and mirror diagonal to see if there is any noticeable difference. 🤔.

That's right and here is the original link: http://www.astrotreff.de/topic.asp?TOPIC_ID=230296&whichpage=4. I summed this up once (https://stargazerslounge.com/topic/371104-refractor-for-planets-mostly-visual-4-or-5/?do=findComment&comment=4031965), but basically it boils down to this:

• That's right, the 125 mm f/7.8 from TS/Tecnosky is optimized towards blue wavelength and not red.
• That is actually good news as one can correct/optimize that for visual use by adding some extra glass into the light path (like a prism or bino-viewer
• Gerd Düring (probably the guy behind Gerd-2 in the post) has calculated our doublet with correct design and glass types and came up with the optimal light-path-length to add glass to optimize the view
• If you add 65 mm you get an optimal PolyStrehl of 0.95, which is awesome
• Unfortunately there is no prism with exact 65 mm, but any added to the light path would make it better (even though it is already very good!)

[alex_stars]

a yes and good luck for tonight @johninderby. Fingers crossed.

[johninderby]

Tested the 125 on my lightweight tripod setup and actually will be usable if not aimed too high. A slow wobble that settles down in a couple of seconds if touched but not enough to affect focusing. So usable for a quick look and the whole setup can be carried outside with one hand. 👍🏻

[Telescope40]

9 minutes ago, johninderby said:

Tested the 125 on my lightweight tripod setup and actually will be usable if not aimed too high. A slow wobble that settles down in a couple of seconds if touched but not enough to affect focusing. So usable for a quick look and the whole setup can be carried outside with one hand. 👍🏻

Hello John. Each time I read your updates on this scope it sounds like an excellent purchase in more ways than one. 
That tripod isn’t your BB 212 tho, is it. Look forward to any further comments you have. 
John 

[johninderby]

Yes it is the Report 212 tripod. 🙂

Perhaps would work better with a Giro or similar mount with the 125.

 

Edited February 28, 2021 by johninderby

[Acrab67]

Hi,

Finally my curiosity piqued me, and I joined club. Yesterday, I order one of these optical tubes from APM's Markus Ludes (TS version).

[johninderby]

Hey that’s great. 👍🏻

So far I’ve been really impressed despite the limited observing I’ve been able to do. 

[Acrab67]

Hi,

Waiting for the first light when the weather permits.Does anyone know where to get a carry handle that fits this tube? I also have to change the knurled screws on the focus group, both of them have been bent inside the transport case.

[johninderby]

Are you going to change the dovetail bar? 

This handle would do but the stock dovetail bar doesn’t allow for moving the tube rings to fit the handle.

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10280_TS-Optics-Tube-Handle-and-Carrying-Handle-for-your-Telescope.html

Which screws exactly. A photo would help.

Edited March 17, 2021 by johninderby

[Acrab67]

Thanks for answering. The distance between the fixing holes of the handle would be 225mm with the standard dovetail. It's going to be difficult to get. The screws are the ones used for locking 2 "and 1 1/4" eyepieces. They are literally butter.

[johninderby]

One of dovetails like the ADM ones with slots in them would be useful as then you can move the rings to suit the handle spacing.

https://www.firstlightoptics.com/adm-vixen-type-v-series/adm-vixen-style-universal-dovetail-bars.html

I’m wondering how the screws could have been bent in shipping as they are well protected in the foam in the shipping box. Perhaps damaged while the scope was being packed.? 🤔

 

 

Edited March 17, 2021 by johninderby

[Acrab67]

Well, the screws must have bent when I put the tube in the box. The truth is that I noticed that it just entered, but from there to bend ... I do not explain it either. What does a couple of quality screws cost to put such rubbish in anyway?

[johninderby]

Fortunately easy to find stainless steel ones on eBay or Amazon.

[alex_stars]

@Acrab67 congrats on the new scope! Looking forward to read how you like it.

As @johninderby pointed out, I also have wondered how these screws could have been bent in shipping. Mine came like Johns, very very well packed and in perfect condition.

Anyhow, two screws can be changes, no problem there.

Fingers crossed for first light soon.

CS,

Alex

Edited March 17, 2021 by alex_stars
spello

[Acrab67]

Thank you,

I also received it in perfect condition and well packaged. I have bent the screws when I put the tube back in the box, don't ask me how. Anyway I already have a couple of new orders. It has been a minor thing

[Acrab67]

Last night I had the opportunity to test it a bit. In general the mechanical construction is excellent for the price we are talking about. Optically I could not evaluate it as I would have liked because the seeing was not accompanied, but being acclimatized and looking at the star test, I could not find signs of decolimation, punctured optics, or notable astigmatism. A bit of chromaticism with the star slightly out of focus, but nothing in focus. I remember observing the Moon with the SW 120ED and the Baader Morpheus 6'5mm, a subtle bluish line would appear. I didn't see a trace on the TS. Detailed lunar details with seeing in mind, with the Baader 6.5mm and Fujiyama Orthos 5 and 4mm. Point stars with good focus. Let's see if I have a good night later.

[johninderby]

Positive teport despite the poor seeing. 👍🏻

I’ve found the Vixen HR 3.4mm works extremely well in this scope and have not  seen even the slightest trace of CA on the moon.

Edited March 19, 2021 by johninderby