Opinions on the Svbony SV503 ED 70mm "quadruplet" telescope
« Part 1 »
I am pleased to express my personal opinion on this product, which I currently own and have had the opportunity to analyze and test.
Passed, deferred or failed tests ?
It might come as a shock, but let me give you my personal conclusion right away ... :
Failed, no excuses.
I would like to remind you that AstroKMan’s reviews are independent and have no partnership ties with any manufacturer, producer or retailer.
My reviews are free from any constraints and reflect personal opinions that anyone is free to question, therefore, do not view them as definitive or infallible.
They are the result of years of experience in this hobby but remain personal assessments and, as we know, personal assessments are subjective and open to debate.
It starts with a focuser locking mechanism that doesn't work, a missing hex screw on the black focus knob, visible internal reflections during flat field imaging and pronounced chromatic aberration, even for an achromatic telescope like this one.
Furthermore, I observed coma at the center of the field of view, while the stars appear as perfect pinpoints at the edges of the image.
Even worse, the focuser assembly unscrews itself from the telescope tube as the temperature changes.
It is truly a great way to waste money, especially for anyone buying this telescope with the intention of doing long exposure imaging.
Before judging this review too strict, I want to give you an example.
If you go to the supermarket and try to save money by buying cheaper products, that's not why what you buy doesn't have to work like it should, if it didn't maybe a knife will not have a wooden handle and the blade will never be sharp like a high quality knife but the knife must still be able to cut the food sufficiently well.
So when you buy an achromatic refractor telescope with a field flattener you don't expect that it offers perfect images but it should at least guarantee mechanical stability, above all especially if it is advertised as a strength and the field leveled thanks to the new optical scheme should be a further confirmation on the type of use of those who buy this telescope.
If the focuser loses its focus and if the optics introduces reflections of spurious light and if the lenses introduce coma that in a refractor is not a good sign then this is not a good telescope although cheap.
The telescope does not keep the promise of being a deep sky observation.
How can you partially resolve these issues if you are determined not to choose a different telescope?
I am sharing the hardware upgrades I made to the telescope, while noting that Svbony has always shown itself to be responsive to the problems I encountered.
First, I installed the missing hex screw on the knob.
It is interesting to note that the focuser shaft has only one flat side, yet there are two hex screws.
One hex screw locks the focusing shaft so the knob cannot slip (flat side), while the other secures directly to the shaft itself (round side), providing greater resistance to mechanical torque.
Unfortunately, this does not solve the problem with the locking mechanism on my unit, even after tightening the hex screws on the focuser assembly.
So, I decided to install a motorized focuser.
The telescope is a "budget" model, it would have been a real shame to spend extra money on a higher quality "name" brand version.
The GEMINI electronic focuser, is perfect.
It offers great value for money and I haven't encountered any issues whatsoever during assembly or use.
If you have the necessary skills to work with the ASCOM software system, I highly recommend this focuser.
The quality to price ratio is truly excellent.
Just a reminder that if you click on the photos, you will see them at full size.
The focuser drawtube no longer slips because the electronic focuser motor has good torque and endurance, even under the weight of a DSLR camera, which is certainly heavier than a CCD camera.
I turned a problem into an advantage, after degreasing the focuser's sliding tube, which had been saturated with excess grease of questionable quality, grease that was extremely runny.
I hate to say it, but personally, I don't consider the mechanics of these focusers to be among the best, even compared to other budget models of this type, despite the inclusion of the two corrector elements designed to flatten the field of view.
Perhaps better quality control from the manufacturer is needed here, but these are just my personal observations.
This is how I resolved the mechanical issues with the focuser assembly, it is a bit pricey for someone looking to buy this telescope and immediately start long exposure deep sky astrophotography but I believe it is a hardware upgrade worth making regardless of any existing problems.
An electronic focuser is always a great asset for astrophotography.
And now, what do we do about the other problems that were found ... ?!
A quick extra note :
to improve the telescope's mechanical stability I spaced the mounting rings further apart.
This meant sacrificing the use of the retractable dew shield which must now remain permanently extended and locked in place to prevent the tube from slipping within the tight rings due to temperature fluctuations (heat/cold).
To further enhance mechanical stability and reduce stress during slow positional changes I added an Svbony handle.
Beyond improving stability this also gives you the option (if desired) to mount a guide scope without overburdening the setup with extra adapters and accessories.
In theory, using an off-axis guider system, which is even lighter, would be even better but that is a topic for another article.
Okay, now let's address the issues of chromatic aberration, coma in the central field of view, and internal reflections within the optical tube.
I already have some ideas about this but I’ll only know the truth which I’ll share with you after running some practical tests.
To deal with such pronounced chromatic aberration, I’ve decided to follow the approach recommended by Svbony: using their 2-inch SV231 filter mounted directly onto a 50mm (2-inch) extension tube, which is necessary to achieve proper focus with CCD cameras (and potentially DSLRs).
We will see how effectively this filter reduces the chromatic aberration of the SV503 ED 70mm (second/flat version), a non apochromatic quadruplet.
And now, the time has come for practical tests ... with one final small note.
I replaced the telescope's standard Vixen-style bar with a longer aftermarket one, giving me more room to shift the telescope for proper balancing on the mount.
I strongly get the impression that this telescope cannot be recommended to people with no experience in the hobby and no means to spend extra money to put together a functional setup, though I hope I am wrong, as these are merely my own personal and debatable opinions.
Waiting for a few nights free from clouds, toxic smoke pollution drifting in from Canada, rain, meteorites, and natural disasters ... considering it has been nearly a month without a single good night for stargazing.
A little patience, and you’ll get the hands-on test of this telescope ... Part 2
Astro KMan
