Tecnosky 80/480 APO FPL53 Triplet OWL Series - Review

[endless-sky]

I have been waiting for this telescope for almost five months. Since May, 19th, to be precise. The day I went to the TS Italia store and saw for the first time the SLD model, model now discontinued. I even missed the last available piece just for a few days, once I finally placed my order, June, 25th. It was to be replaced by a newer model, available at the end of the Summer.

Boy, am I glad I did miss it. The wait was definitely worth it. The new and improved model is simply beautiful. I fell in love with it as soon as I saw it on the Tecnosky website a few weeks ago, when they posted the product sheet. But in person, it's even more beautiful.

So, the people from the store emailed me Friday, October the 2nd, telling me that it was finally available for pickup. I read the message only a whole hour later and it was soon going to be closing time. I started calling at 4:30 PM and I finally managed to get my phone call through at around 5:05 PM. The store closes at 6:00 PM and doesn't reopen until Monday. And it's 40 minutes away from where I live. I made it there in 35. There was no way I was going to have to wait till Monday, knowing my scope was only a few minutes away.

So, here's the pre-unboxing picture:

- top left, brown box, behind: Vixen clamp for guide-scope

- top right, white box: 60mm f/4 guide-scope

- top left, white boxes: T2 Nikon ring, 30mm spacer, adjustable spacer

- center, behind white boxes: Optolong L-Pro 2" filter

- right of filter: spacers mounted and already calibrated for 55mm backfocus, for eventual use of the ZWO ASI 224MC camera with the refractor

- top right, Bahtinov mask

- underneath the white boxes, top left: Losmandy bar to attach telescope to my NEQ6 Losmandy saddle

- big box underneath all of the above: Tecnosky 80mm f/6 FPL-53 OWL Triplet, with carrying case and 0.8x 4 elements flattener/reducer

- ZWO black case: ZWO ASI 224MC guide-camera / planetary camera

- front left: Talisker 57° North and two glasses (don't mind the shape of the glasses, they are the closest to Whisky suitable glasses that I currently own...) ready for me and my wife to celebrate the end of the wait

- front right: box for the aforementioned Whisky

I actually waited for yesterday (Saturday, the 3rd) for the unboxing, because I wanted my best friend Omar to be present and help me with filming and taking pictures. We have been friends since we went to kindergarten and we always have had astronomy as a common interest.

It just so happens, to my immense surprise, that my telescope is actually SN. 0001, so I own the first telescope ever produced of this new series. The certificate is also very promising, with a Strehl ratio of 0.974 and a Ronchi test that seems very well behaved. I like a little less the red edges on the lenses, but I guess only time and a proper visual - and astrophotographic - session will be able to tell.

Obviously the "new equipment curse" didn't help, but we got almost a whole hour with clear sky patches and obviously I couldn't pass up the opportunity. I quickly setup with the bare minimum necessities for a visual observation and me, my wife and my best friend Omar - who helped with the staging, recording and directing of the unboxing event - took a quick look at the Moon, Saturn, Mars, M31 and Perseus Double Cluster.

I can definitely understand now, even if the seeing wasn't perfect, and my eyepieces didn't offer enough magnification (25mm and 10mm give me 80x and 200x, with my C8, but with a native focal length of 480mm, even with a Barlow 2x, we could only achieve about 38x and 96x, respectively), what people mean when they say that an apochromatic refractor brings out the objects from the background sky. The contrast was stunning, the stars were absolute points, pinpoint, small and sharp (with my C8 they always have kind of a "blob" feeling), the contrast on the Moon was fantastic and I could see many details, despite it being almost full, and only at 48-96x. I think it passed the visual test with honors. I was also very happy to be able to see the Double Cluster all in the same field of view for the first time. Saturn was well defined, could clearly make out the rings - don't recall, in all the excitement, rush and cycling between me, my wife and my friend, if I saw the Cassini division, but I'll definitely try again next clear sky night. Mars was also beautiful, could clearly see its rusty red color, the polar cap and some darker, black features on the surface.

I really can say it's a beautiful telescope, very well made and machined. The attention to details is really of another level, the paint finish is very nice and matte. Also very lovely all the different red and black anodized surfaces, they really give it a nice finish and personality. The focuser is also the best I have ever had on a telescope. Very smooth, precise, with no backlash. Coming from a C8 where every touch of the focuser throws off the image all over the place and the backlash is quite significant, I really appreciated how easy it was to fine tune focusing with a proper focuser, especially with the 10:1 focusing knob.

I can't wait to be able to take the first pictures of some star field, to check if even photographically the telescope lives up to my expectations. I hope to get pinpoint stars corner to corner and that the backfocus won't be something too hard to make perfect.

Here's some accessories.

Optolong L-Pro 2" filter, Bahtinov mask, Losmandy dovetail to replace the Vixen one the telescope comes with, Nikon T2 ring and spacers to use the ASI 224MC with the correct backfocus directly on the telescope, instead of a guide-camera.

Here's the 60mm f/4 guide-scome, with Vixen clamp.

And the ZWO ASI 224MC guide-camera.

Here's the mandatory celebration beer, at Corte dell'Orso (the Bear's Courtyard).

It's a Belgian sour beer, lambic style. Oudbeitje by Hanssens Artisanaal, with added strawberries. A very nice beer, sour, tart and fruity. Could definitely taste the strawberries.

Cheers!

Here's a couple of pictures of the full setup, with everything mounted on my Sky-Watcher NEQ6 Pro.

The setup is in its astrophotographic configuration: mount, telescope, guide-scope, guide-camera, filter, flattener/reducer and at the end the Nikon D5300 astromodified. All controlled by Astroberry on my Raspberry Pi 4 4GB, conveniently mounted on a bar across the two telescope rings.

And finally a close up of the rig.

Edited October 4, 2020 by endlessky

[teoria_del_big_bang]

Some very nice gear there I hope some clear skies are not far away.

Thanks for comprehensive write up and pictures and for sharing 🙂 

I am pretty sure the scotch is an essential item of equipment, it sure helps n the UK on the long cold winter nights.

Steve

[endless-sky]

Thank you, Steve! I can't wait for some clear skies to start testing it properly.

I'll post some pictures here as soon as I'll be able to get first light.

The Whisky sure was a necessity. I like Scotch, especially those with a smoky taste. The beer was also very good, if you like sour beers. If you haven't ever tried one, definitely worth the experience. I'd suggest to start with the fruity ones, since the plain ones tend to be very sour and tart, and if you don't expect it, they could ruin the experience.

Edited October 4, 2020 by endlessky

[teoria_del_big_bang]

1 hour ago, endlessky said:

The Whisky sure was a necessity. I like Scotch, especially those with a smoky taste. The beer was also very good, if you like sour beers. If you haven't ever tried one, definitely worth the experience. I'd suggest to start with the fruity ones, since the plain ones tend to be very sour and tart, and if you don't expect it, they could ruin the experience.

Can't say I have tried the sour beers, I do like a lot of Belgium beers including the fruity ones so I will look out for the sour one and give it a go, no harm in trying it 🙂 

Steve

[endless-sky]

Last night, October, 5th, I took out my rig for the first "real" testing of the OWL in its astrophotographic configuration.

Here's a picture of the whole setup, taken just a few moments after setting everything up.

I started setting up around 7:30 PM and was ready a while before astronomical darkness, around 8:00. I started tearing down and bringing back inside my gear at around 1:00 AM, so I spent a good 5 hours out there testing things.

First thing I did was a rough polar alignment, using an app on my phone and eyeballing Polaris in my polar scope.

Clouds were constantly rolling in, so I had to "chase" the clear sky patches, never settling on one particular zone for more than 5-15 minutes.

I used the Bahtinov mask for focusing and was extremely surprised on how easy it was to judge and adjust focusing, even if I couldn't do it "live" with the DSLR, but I had to take a picture, adjust, take another one, adjust again, and so forth. After a few minutes, I decided the focus was pretty spot on, removed the mask, and took a 10s test shot. I was immediately amazed by how small, tight and round the stars were - to my standards, of course, coming from a 70-300mm kit zoom lens that is more useful as a paper weight than for taking astro pictures...

I took a few short pictures here and there, with the focal reducer/flattener and the L-Pro light pollution filter installed.

I even tried guiding, first with PHD2, then with EKOS internal guider. I was glad that the calibration procedure worked and successfully completed, in both cases. With my first PHD2 guiding, using the default settings and algorithms, I was able to go under 1" RMS (0.75-0.85") and was quite happy. Can be better, but nothing to complain about for my first automated guiding ever. I later tried with EKOS, using multi-star guiding and predictive PEC, but the guiding actually got worse (around 1.25-1.5"). My mount period is around 480s, and I never managed to guide for longer than 5 minutes, before having to move to a different spot in the sky and restarting the guiding process all over, so I hope it's just a case of not giving the guider enough time to "learn" the periodic error and adjust for it. Definitely have to try this again with more stable weather.

Another thing that baffled me was focusing the ASI 224MC through the 60mm f/4 guide-scope. The focus always appeared "soft", even when the light source was a small as possible. What I didn't try was using my smaller Bahtinov mask and try to focus with it. I did, however, try to focus directly on the Moon. No matter what kind of gain and exposure time I used, the "best" focusing I could achieve was the Moon disc, with hints of its surface different areas, the maria definitely visible (with a different color than the rest, so the exposure was fine), but nothing crispy, no detail whatsoever. It didn't even matter what type of bit settings I chose. Is this expected behavior with a guide-scope? I don't think there's a backfocus distance to be respected when using a guide-camera / guide-scope combination, since there's no flattener/reducer attached. Right?

Other problems encountered: with a guide-camera I thought I could finally take advantage of better polar alignment tools, since with a single-shot DSLR is pretty much impossible. So I did both EKOS and PHD2 static polar alignment routines. They work pretty much the same. For both, you point the telescope at Polaris, in the home position. With EKOS, it takes three static pictures, one in the home position, one after rotating the AR 30°, and another one at 60°. With PHD2 it uses the guide-camera and does this "live" by rotating the AR axis and monitoring the movement of a chosen reference star (I chose Polaris just to make sure I didn't input the wrong star) in the guide window. At the end they both give you an error and a vector for where Polaris is supposed to be. With EKOS I got around 9', with PHD2, 80'... So, I don't know how much I can trust these. What I didn't try was drift polar alignment, which I am sure will work much better and reliably. I will definitely do that next session.

What else to say... Time for some first lights.

The only processing the following pictures have consists in this:

- AutomaticBackgroundExtractor

- ColorCalibration

- Stretch

Here we have a 90s shot of M31, with L-Pro filter and 0.8x flattener/reducer.

What I do like, as I said above:

- tightest, smallest, roundest stars I have gotten since I started doing astrophotography at the end of January

What I don't like:

- star shape not consistent in all areas of the image

- residual chromatic aberration, especially on stars that are not round: there's clearly some red and blue edges visible

I didn't expect this from an apochromatic refractor, but maybe it's just because the stars are kinda "smeared", so not all light is focused at the same spot? I don't see this around the center of the image. Maybe I have some tilting in my imaging train/sensor?

Here's a mosaic generated with the AberrationInspector script.

Here we have a 95s shot of Capella and surrounding star field, with L-Pro filter and 0.8x flattener/reducer.

What I like and don't like - same as above.

And here's the mosaic.

[david_taurus83]

The guide scope is an achromat by the looks so it will have lots of bloat. I added a cheap IR/UV cut filter to my last guide camera and it tightened up the focus nicely.

Your star shapes don't look too bad either for a DSLR. You could try experiment with spacers etc but that way, madness lies..

[endless-sky]

Thanks for the tips. I must say I pondered the idea of the "lack of focusing" being due to the fact that I have no filter in front of the 224MC and that it's a camera very sensitive to IR.

I guess I'll try the 224MC paired with the APO and see how it goes. It should give me better focusing and also prove if the star shape is due to the spacing of the DSLR, as you suggested. I know star shape depends on how close to the correct backfocus you are, and if I need to go further than where I am now, I see no problem (I can always add). But if I needed to go closer, I don't know how I will be able to achieve this. The Nikon T2 ring plus the distance between the front of the camera and the sensor already give me 55mm, and I don't see how I could reduce that distance...

[endless-sky]

So, I took the rig out last night (October, 7th) for another session. I removed the L-Pro filter, to have less variables in the mix.

I also took four pictures of the same star field and same exposure time, rotating the camera (D5300) - using the telescope built in camera rotator. I started with the camera at 0°, then 90°, then 180° and finally 270°.

I even tried doing the same tests with the D90, and got pretty much the same results. So, it seems camera independent.

I feel I can rule out tilting, since the star shape stays pretty much the same in the corners, independently of camera rotation (for example, same top left corner for all for images present same star shape, and so forth for the other corners). The star shape is also more consistent, and they all look elongated in an orientation perpendicular to radial. To me it's quite possible that the camera sensor is a little too far from the flattener/reducer, meaning I should somehow shorten the distance.

I also don't think the filter had any fault in the way the first pictures turned out, since the star shapes in the pictures without filter and in the pictures with filter are pretty much identical.

I emailed the store where I bought it describing my concerns. I will see what they suggest to do.

I tried calling, but my call got redirected to another Tecnosky store and I spoke with somebody else that wasn't the person that have been following me for all these months. He suggested to try adding distance, first, and see if that works - since at the moment I have no way of removing distance, other than buying a low profile T2 Nikon ring.

As for guiding, I run Guiding Assistant and optimized the settings, with its suggestions. It also gave me a polar alignment error of 3.4 arc-min, after I let it run for 5 minutes. I must admit polar aligning was very easy last night, since by the time I was ready to polar align, the app showed me that Polaris needed to be almost exactly at the 9 o'clock position as seen from the polar scope.

I did a 2 hour session on the Heart Nebula, and guiding stayed well below 1" RMS for the whole duration (excluding the dithering peaks, the RMS was between 0.65" and 0.85"). After a while I wondered if I could make it even better, so I remembered the "east heavy" rule. I stopped the imaging session, slid the counterweight a few centimeters down from where it was, and sure enough, after I resumed guiding and imaging, the RMS was now between 0.45" and 0.65" - more than a good 25% less, just by moving a counterweight. Amazing!

I'll post it after I finish some processing. If in the next couple of nights it's clear, I would like to add more data to it, as well.