ATX sample variation? (1 Viewer)

Hi,

In what percentage is sample variation present in Swaro’s ATX line?
I’m a very happy owner of a 95ATX for a couple of years and there are others I know, who also own one. It happened a few times, someone told me they thought mine seemed a little better than the one a friend owns.

Now I purchased a 65mm objective modul and I’m not impressed at all.
I feel it lacks some sharpness, always searching for the right focus.
Above 40x feels to much, while with my 95, the view stays sharp, even at 70x (if not touching the scope)
I remember looking through one a year ago thinking that it was very nice and when comparing with my 95, I thought it was not much behind in lower magnifications. I don’t feel the same way with my example.
Should expected more from the ‘best’ 65mm scope available.
Not sure what to do, maybe some side by side with another to see..
I don’t believe mine is the standard, if it is, I like to see something else like a Kowa tsn or something. I’ll bet money it’s better.

A star test and resolution test should help.
Sounds like it is not the best example.

In such cases I have presented my findings direct to the makers and they have sorted a specially tested and picked replacement.

Regards,
B.

Hi Nivado,

I think nobody (except maybe Swaro themselves) have enough data to do a serious statistic on the optical quality of their scopes.

Also even with perfect instruments, a 65mm instrument will exhibit a quite noticeably lower resolution than a 95mm one. That being said, both of those perfect instruments will be quite fine at 60x or thereabouts.

For what it's worth, I have seen a few quite different samples of ATX scopes - one 95mm is still remembered as really bad with a not very happy owner after comparing but two others were average at best too.
Otoh I lately also saw a real cherry 95mm with an extender and BTX at 60x which was really stunning after you had the IPD and diopter settings sorted out. It's owner also used a 2nd extender and said it was still quite usable with two extenders stacked and I believe this.

I would also recommend a star test, preferably using a bright real star in the sky and thus at infinity focus (artificial ones need to have a quite tiny pinhole and enough distance, otherwise even a perfect scope will show flaws introduced by the to close viewing distance).

You normally need to use the highest magnification possible for a spotting scope - for astro instruments the rule of thumb is to use the focal ratio of the instrument as the eyepiece focal length in mm.
Since the ATX65 is probably about 460mm and thus probably has f7 or so, one would use a 7mm EP (preferably a fairly simple and high quality one, like an orthoscopic) for a magnification of 65x - so the 60x top end is close enough...

You then aim the scope at a bright star and ever so slightly defocus the star in both directions. Ideally you should see identical images of well defined, round and concentric diffraction rings inside and outside of focus.

In reality the form, concentricity and sharpness of the rings can tell an experienced observer a lot about different optical flaws of the instrument.
Good online literature is https://www.telescope-optics.net/star_testing_telescope.htm with images (you want the unobstructed ones) or of course in-depth and comprehensive the canonical H.R. Suiters, Star Testing Optical Telescopes 2nd ed, Willman Bell, 2009.

Or try to make some usable images slightly inside and outside of focus and post them with a nice plea for assistance either here or probably better in the refractor formum at cloudynights.

Joachim

Does anyone know of a quick, approximate real-world way - carried out in an optics store during the day (one with an outside viewing area) - that you can get an idea of whether a scope is a good or problematic example? (i.e. a way of evaluating a potential scope that you want to purchase.)

I have used a metallic, globe-shaped Christmas tree decoration with reflected light from an LED light source to "simulate" a star test when no other method was viable! I guess you could place one on a car outside and hope to pick up a reflection of the sun.

Or you can get yourself one of these to carry around:

http://www.hubbleoptics.com/artificial-stars.html



Pete

Thx for the replies..
I’ll try to do a startest tonight if the sky is clear.
I’m not an optics specialist and I don’t understand everything in the link, so I’ll probably try to make some pics thru Iphone via Swaro adapter. But It seems all to do with the shape of the rings.
Today it performed better at first sight, but the sun is shining.. All optics become better on sun-shining-days.

Grtz

The star needs to be quite high to reduce atmospheric turbulence. Polaris is a good choice as it doesn't move.
The Seeing or steadiness of the atmosphere needs to be good and hopefully fairly transparent or clear air.

Over grass, vegetation, not over buildings, concrete/asphalt.

However, one can have good star images and not very good resolution, so a resolution test is also needed.

I would just look at Jupiter and know if the scope is good or not.
Unfortunately Jupiter is very low now at 50 degree north latitude, so this doesn't work at the moment.
It would work O.K. at latitude 30N. Or in Australia.

I can do that with looking at a magazine on a distance.
Then I can compare with my 95 but that might not be entirely fair.
Should have another 65 to do a side by side comparison, so I’m able to see if there’s any difference between the 2.

pete_gamby said:

I have used a metallic, globe-shaped Christmas tree decoration with reflected light from an LED light source to "simulate" a star test when no other method was viable! I guess you could place one on a car outside and hope to pick up a reflection of the sun.

Or you can get yourself one of these to carry around:

http://www.hubbleoptics.com/artificial-stars.html



Pete

Click to expand...

Cheers Pete. I guess I was hoping for a good simple test that didn't involve artificial stars (I don't trust my ability to interpret the results I might get)!

I suppose that cranking the zoom up full and trying to read some distant print might be a more-workable start. If you then compared two versions of the same scope and noticed a difference at least you could pick the best example... (Is my assumption that testing at the highest possible mag is more likely to pick up any issues - so in the case of an ATX trying with the 1.8x adapter on would be a good idea?)

I share your thoughts Grando. When doing so, I think it’s a simple way to see if there’s any difference.
Probably also because of a lack of knowledge about it (at least in my case).

I just did a quick test with both 65 and 95mm next to each other. I couldn’t change quick between the two, since I always had to change the oculair module. But I could see.. well, something different.

First of all, I’ve putted the two objectives (both on decent tripods) at a distance of around 35-40meters.
Than I placed a magazine with text’s whereof the letters were between 1 and 2 milimeters. So, small enough.

What did I saw? Well, the 95 outperformed the 65.. wich is logical.
Through the 95 I could read every word at 40x. At 30x, I couldn’t really.. and didn’t tried inbetween.
Without wind and without touching, it was actually very easy to read and it became more easy at 50x and so on to 70x. At 70x it was still a joy to see how good it performed at such a high magnification.
With the 65 it was all a little less ‘sparkling’. At 40x, Reading was difficult, at 50x It was better but at 60x, the difference seemed rather small. Remarkable was that It seemed that Reading at 40x with 95 was more easily than at 50-60x with 65. Or does this has something to do with the langer exit pupil?
I didn’t thought the 65 was bad but I’d like see how it would perform to another 65.

Nivado, you should make a 65mm mask from black cardboard maybe for the 95mm.
Then compare the two 65mm scopes.

However, this isn't entirely fair, as the 95mm scope has a longer focal length and bigger focal ratio when stopped down to 65mm.
So the 95mm will be better even if they both are optically excellent.

If you had access to another known excellent 65mm scope that would be fairer, but again, the eyepieces would be different and of different qualities. Same with the prisms.

I suspect that your 65mm module is not the very best.

Hi,

the test with a resolution chart or magazine in a pinch can of course give an indication that one example is better that the other - but without comparison it gets tricky. And also you can only see that the image is soft but not really why - which the star test can tell an experienced observer (or those with good imaging skills and a community to ask).

You can of course use an artificial star - commercial or diy (reflection of sun or led light in mirrored sphere like bearing ball or xmas ornament or a tiny pinhole in aluminium foil in front of a led light) .
The important thing is to use enough distance - for small scopes like spotting scopes 30m or so should be ok, for larger astro scopes it can get a bit difficult to find a large enough open area...
If you are too close, you will see spherical aberration that is not there in reality, if the pinhole is not round, you will see astigmatism or pinching which is not real etc.

Looking forward to some images...

Joachim

It’s cloudy tonight so I only had a look at some stars at a moment the sky was clear without having time to see if I could make a picture. I’ll try again tomorrow.
This was my first time doing a startest so I’m not sure wat I just saw.
It seemed like the view over focus looked a lot like the outside focus under ‘Turned down edge’ in this link

http://www.company7.com/books/products/testing.html

Under focus, it was quiet the same but more hazy.
No idea what it ‘can’ mean, need to make decent picture.

Hi,

well, the images in your link are for obstructed scopes like Newtonians, Cassegrains and the like, which makes things look a little different than for unobstructed.
Also turned down edge is a term from mirror grinding, but of course a lens can also have problems near the edge which look kinda similar.

In that case masking off the outside 5mm or so of the objective with a perfectly circular mask should fix the issue - or show different problems which were hidden by the one just eliminated...

Joachim

Still hadn’t got the chance to try and make some pics of stars under clear sky.

Did some viewing today in a little brighter weatherconditions than before, back then, when it was dull and dark.
I may have been a bit hard on them cause today they did quite well, even at higher magnifications.
Was able to see some nice feather patterns on male Gadwalls at a distance of a 100m away and I had the idea of it keeping the image sharper on higher power than before. So I guess they just need the sunlight to perform decent..
Although I still think this is not the best example, and maybe I can do some side by side with an APO Televid 65 in 2 weeks.
Makes me very curious about what differences I will see.
In the mean time, I will take them with me to my trip to Africa where I hopefully can take some starimages.

Grtz

"Although I still think this is not the best example, and maybe I can do some side by side with an APO Televid 65 in 2 weeks..."

Please do post a follow up to this if and when you can.

So far, from using 95mm and 65mm on STX and BTX, the scopes is sharp throughout its zoom range. I have also tried others 85mm and 65mm, it also exhibited great sharpness.

Here are some starpictures through the ATX65.
Not sure of them to be ideal but that's all I could do with my Iphone digiscoped.
I have to add that there seemed to be a little bit of a mist in front of the moon, but it was only visible when looking at the moon, so I don't know how it influenced the images.

First is past focus, second before focus en third is in focus.

If I can do the comparison with the Leica APO televid 65, I will post the result.
Maybe this week.

Not a star picture, but a bright light in ~5km distance in my Zeiss DiaScope85. It's not a truly Airy-disk, I know…

Manfred