Skywatcher Evostar 90mm Refractor Review

[Alkaid]

Introduction

I bought this telescope as a present for my Mother. I’ve been into Astronomy for a few years now, and take my TAL to her house when visiting. Of course, she developed an interest and recently joined a club. I knew I had to get her a scope, but which one?

The Evostar 90 / EQ2 package fitted the bill. Lightweight, virtually zero maintenance (no collimation), and should be good enough on easy to find objects. Plus it did not break the bank. The box arrived at my home and it would be another couple of weeks before I would go to Mum’s. I decided to assemble it for her and test it. How would it perform?

Incredibly, I was lucky enough to have two clear nights within one week.

First Light – Messing About

First light was conducted from right outside my house, streetlights galore, with the intention of a quick look at the moon to see if the eyepieces actually worked. The moon was at 1st quarter, my favourite phase of observation. The OTA was retrieved from a cold cellar, so not much acclimatising was needed. It must also be remembered that your eyepieces also need to acclimatise in order to get the best from your scope, so these were quickly popped outside and left to cool off whilst I set up. Set up is an absolute breeze due to the light weight of this system, no huffing and puffing moving this equipment outside. In order to get the eyepiece at a convenient height, the mount legs were fully extended. With eyepieces also cooled off, it was time to start.

Using the 25mm eyepiece giving x36 the perfect half-moon snapped into focus. It was a very nice image indeed. I then used the stock Barlow and image remained very sharp, the complete half orb now filling the entire field of view. I was looking hard for Chromatic Aberration but at this lowish power of x72, there was none whatsoever. Time to increase the power using the 10mm eyepiece.

I have had a very poor experience with this eyepiece in the past used on a short focal ratio Skywatcher reflector. But in this longer focal ratio refractor, I was pleased to see that the image was clean and crisp. A faint blue line of CA now hugged the moon’s edge, but I had to look for it and it was not at all troublesome. To give you an idea of the CA at this power ( x90), it was like someone had drawn a very thin blue line on the Lunar edge with a very sharp light blue pencil.

Ok, the penultimate test, barlowing the 10mm eyepiece to give a power of 50x per inch of aperture, x180 in this telescope. I was not expecting miracles, but it would seem that I got one. The image was still sharp! The CA was amplified slightly; the blue hue at the Lunar edge was now slightly thicker but not by much. It did not trouble me at all.

So – all stock eyepieces work, and they work rather well in this F10 ratio refractor.

The next test was a star test. I went straight for Capella in Auriga. Still using the highest power eyepiece combination and racking the focuser in and out, I saw nice clean concentric diffraction rings, perfectly circular, except that on the outer most ring there were three tiny ‘bumps’, each spaced 120 degrees apart. These didn’t go away when I changed down to the next power. Puzzled, I shone a torch down the OTA and saw that the lense has three tiny square ‘stickers’, evenly spaced at 120 degrees, which sit right at the edge of the lense. I have no idea what these are for, possibly to allow easy alignment during construction. These jut out ever so slightly into the light path, causing the three tiny bumps to appear in the outermost diffraction ring. I was not too annoyed at this, as the other diffraction rings were perfectly concentric and therefore thankfully this was not an issue with the lense figure itself. Judging from my earlier very positive experience at 50x per inch magnification on the moon, I was happy that I had been supplied a decent optic and would hope that this is consistent for others who chose this model.

2nd Light

2nd light was conducted away from streetlights, but still in an area of horrendous light pollution. A small pocket of countryside between Leeds and Bradford enables one to attempt to escape the sideways glare, but the overhead orange is un-escapable without driving 30 miles or so. I put the mount head, eyepieces and other equipment (planisphere etc) into a rucksack and headed off down a bridleway which I know well. I carried the tripod in one hand, the OTA in the other. The light weight of the equipment made the 300 yard walk to the bottom of the bridleway easy. Points definitely gained for portability with this set-up. It was almost a full moon so the sky was quite washed out. But as I am a solar system enthusiast foremost, that didn’t matter. Jupiter, Venus and Mars all out tonight, the former two descending slowly in the West, the latter red planet high in the sky.

I started with Venus and went straight for the 10mm eyepiece (x90). The shape was un-mistakable, with the gibbous phase clearly seen. The seeing was a bit iffy; the planet was at a low altitude and rippled gently. There was a little blue colour around the planet, but un-troubling to my eye. It may be troublesome to others though. However, I would expect this to diminish slightly with the use of high quality eyepieces. Cranking up to x180 resulted in even more blue hue around the planet, but the shape and phase still reasonably crisp. The C.A. was completely expected, but I was pleased that at least the image was quite sharp. The problem with Venus is that there is not much to see, other than the phase. I noted the phase and drew a rough sketch.

Next, to Jupiter. This was slightly higher in the sky than Venus (though not by much) and I was hoping that the seeing would be a bit better. It was roughly the same, the disc rippling gently. However I could clearly see four belts, not just two main ones (NEB & SEB). The Galilean moons were nice pinpoints and not the tiny ‘shards’ of light I seem to see through my reflector. I have read that refractors are better at ‘punching through’ turbulent air and the image of Jupiter was far more stable than I have seen before. I came away from the eyepiece thinking that if the diagonal and eyepieces were upgraded then during favourable seeing conditions the GRS could be a target for this scope. I couldn’t try for it myself as it was on the other side of the planet at that time.

Mars beckoned, the only planet high up. It was about 14 arc seconds across and I have found it a tough target in the past with small reflectors. I got a shock - at x90 I could clearly see dark markings – and a polar cap! I couldn’t believe it. Going to the highest power provided a pretty good view, polar cap now blatantly obvious. The high altitude helped immensely, the ripple effect of the seeing had slackened and a crisp image floated across the field of view. Very pleasing!

Next, some DSO’s. These were not as good, though my location certainly did not help and the almost full moon was never far away…

M42 – ok, but regretfully nothing special from my light polluted site. Trapezium razor sharp though.

M45 – Very nice, always a good view wherever I am.

M35 – A sprinkling of stars against the sky, a lovely cluster.

Double Cluster – Always nice. Individual star colours seen, some red, some yellow, some white.

Double Stars

Due to the washed out sky, I then decided to test the optics again by going for some doubles. First up was the nice and easy Alcor & Mizor in Ursa Major, not really a test but just having a look as it were. This was easy, Mizar’s 14 arc second pair with miles of dark space between them. My next target was Castor in Gemini. At 2.5” separation this is a good test for small scopes and the Evostar split the pair very cleanly at x72. Cranking up the magnification to x90 revealed a deep void of space between the pair. They looked sharp and pinpointy, with slight airy discs around them and I came away from the eyepiece feeling rather pleased. Finally I had a look at Algieba in Leo, this pair had a slightly wider separation at 4.3” and both orange components looked good. Overall a rather decent performance.

Lunar

Last of all, I turned to the object that was reflecting all the light – the moon. Normally one of my favourite objects to observe, it was about 95% illuminated and would be no-where near as good as observing at 1st quarter but I decided to have a look anyway.

Starting near the terminator on the western side, at x90 I got a great view of the Valley Schroteri, this magnificent Lunar grand canyon snaking through higher terrain. Of course, I upped the power (I’m prone to doing this!) and the image remained sharp with much detail present.

Then I turned to the craters on the far western limb, those where the terminator was edging its way towards full moon. What became apparent at the limb was an increase in blue chromatic aberration, more than what I had seen when observing at 1st quarter. After thinking about this, I realised that C.A. is more visible in achromatic refractors when looking at bright objects, the brighter the object the more C.A. one will see. Of course with the moon being almost full, far more light was being reflected, hence the increase in the blue hue which hugged the Lunar limb. I tried an experiment and chose to point the instrument at the craters Hevelius and Caverlerius, right on the edge of the terminator. I noted what detail I could see – small bumps and ridges within the larger Hevelius and a rough little mountain peak in the centre of Caverlerius. The slight blue hue was present within the craters. Then I took hold of the refractor’s lense cap and popped out the central piece, leaving a 60mm hole. Putting the lense cap back on now resulted in a 60mm F15 instrument. Returning to the crater pair, I saw that all the C.A. had gone. Completely. There was not a blue hue in sight, just grey and ink black. The large craters themselves were also slightly sharper, not by much but enough to notice with my eye. But the trade off was this – the fine detail I had seen within the craters had now also disappeared, not surprising since resolution is dependent upon aperture. The small bumps and ridges within Hevelius were replaced with a flat monochrome surface. The little mountain peak within Caverlius was still there, but the roughness had gone. It was now smooth sided.

So to sum up, the Lunar viewing was very good. At first quarter or when the moon is not that bright, the full 90mm aperture delivers without excess colour. When at its brightest, you will see more colour but the detail is still there to see. And when you only wish to observe larger Lunar features that a 60mm objective will happily cope with, stop the objective down and enjoy the sharper colour free views.

Summary

I only had the Evostar for two weeks before I could deliver it to my Mother, so I would not call this a conclusive evaluation. But in the short time I had it, I was impressed with one major attribute. Value for money. I wanted a beginner scope for my Mum, one that would actually work and not cause disappointment. Many budget scopes are sadly garbage. This basic package works. The optics are pretty good. It surprised me when I looked at Mars and performance on the moon was also very good. I suspect that from dark skies it would deliver very nice views of open star clusters.

It is a telescope that will develop someone’s interest in Astronomy, not kill it. And if a seasoned observer wanted a lightweight grab ‘n’ go to have a quick look instead of setting up the 12” monster, then it would also do quite well in this capacity. I paid £140 plus shipping for the Evostar 90 - a very reasonable price to pay for a package that does what it says on the tin. I’m also pleased to report that my Mother loves it. The reason I know this is because my Father is not allowed anywhere near it!

Steve Gold

Here is a quick vid of the scope:

http://youtu.be/MysbcPzjyiQ

And here are some pics too:

[John]

Thats a very comprehensive review - thanks for posting it. I would have given a lot for a decent 3.5" refractor when I was starting out but they seem to be available at a very reasonable price now.

The three small "bumps" or "stickers" that you see in the objective lens are actually foil spacers to separate the lens elements. The lens design is called an air-spaced doublet and is very commonly found - both my ED refractors have them.

[Alkaid]

Many thanks for your comments John, I now see exactly what you mean regarding the air spacing. Thanks for pointing this out -it will be helpful to others reading this.

BR - Steve

[bollah]

Great review thanks Steve,

I was just wondering if you've had a chance at testing the scope out with any higher quality EPs?

It sounds like a good first scope but I'm keen to know if it has room for upgrade.

Thanks

Adam

[tony4563]

That's an excellent review Steve.

Great reading

[Alkaid]

Great review thanks Steve,

I was just wondering if you've had a chance at testing the scope out with any higher quality EPs?

It sounds like a good first scope but I'm keen to know if it has room for upgrade.

Thanks

Adam

Hi Adam,

I'm afraid I haven't had a chance to try it with quality eyepieces yet. But I reckon it would be pretty good, with reduced CA on the brighter objects. The scope doesn't have a 2" facility, but I suppose that's due to it's price range. This doesn't put me off though, the argument being that most refractor targets tend to be solar system ones and don't need a wide field of view. Although even with the 1.25" 25mm eyepiece I could still fit the Double Cluster into the full field.

I think that this scope could get Jupiter's GRS with an upgraded 1.25" diagonal and high power eyepiece.

When I get the chance to try I will certainly let you know.

BR - Steve

[MidnightMinstrel]

How big approximately was the view of Mars and Jupitar ?

[Alkaid]

How big approximately was the view of Mars and Jupitar ?

Jupiter looks like a large pea at arms length. Mars looks like a small pea. Regretfully observing from the UK does limit the magnification of most scopes to about 200 times due to seeing conditions. Not much difference between that and 180 times with the Evo.

[Alkaid]

That's an excellent review Steve.

Great reading

Many thanks Tony. Fancy a shootout with your 120 ED? Just kidding ha ha! That's one beautiful refractor I aspire to own one day.

Steve

[tony4563]

Hey, maybe one day mate .... or night!

I'm not far from you. I live in the Bradford area

[MidnightMinstrel]

Jupiter looks like a large pea at arms length. Mars looks like a small pea. Regretfully observing from the UK does limit the magnification of most scopes to about 200 times due to seeing conditions. Not much difference between that and 180 times with the Evo.

Hmm, so there would be little point say, buying an 8inch reflector scope over a 4 or a 6 if the size of the view is going to be the same.......same thing with a refracter then, i.e no point spending over a grand if it it's going to give me the same view as one only costing a few hundred pounds. Makes me wonder how the views on YouTube from various scopes look so big, they must manipulate them through a computer or something. My eyes arn't so good to be honest, I may have to have think about a decent webcam to hook it up to a computer as well then, sigh!

[rory]

Hmm, so there would be little point say, buying an 8inch reflector scope over a 4 or a 6 if the size of the view is going to be the same.......same thing with a refracter then, i.e no point spending over a grand if it it's going to give me the same view as one only costing a few hundred pounds. Makes me wonder how the views on YouTube from various scopes look so big, they must manipulate them through a computer or something. My eyes arn't so good to be honest, I may have to have think about a decent webcam to hook it up to a computer as well then, sigh!

the size of appeture does not make an image bigger at all,what it does do is make an image brighter. so for astronomers looking to observe deep sky objects(dso's) like nebula and galaxies this makes alot of difference.

for instance an average galaxy in my 90mm telescope from my back garden would appear nothing more than a small grey smudge at best. the same galaxy in say a 10 or 12 " telescope may well show dark lanes and spiral arms.

of course also as larger appeture collects more light it means you can usually add magnification without losing to much contrast. with a small scope high mag will often appear fainter or washed out and you lose sharpness.

hope that helps. ( and hope im right)

[Alkaid]

Hmm, so there would be little point say, buying an 8inch reflector scope over a 4 or a 6 if the size of the view is going to be the same.......same thing with a refracter then, i.e no point spending over a grand if it it's going to give me the same view as one only costing a few hundred pounds. Makes me wonder how the views on YouTube from various scopes look so big, they must manipulate them through a computer or something. My eyes arn't so good to be honest, I may have to have think about a decent webcam to hook it up to a computer as well then, sigh!

Imagine putting the 90mm refractor against an 8" (200mm) scope. Both scopes are pointed at Jupiter, at the same magnification. So the image is the same size in both scopes.

The 200mm scope collects around 5 times as much light as the 90mm scope. This means that the 200mm scope can pick out details on the planet's disc which are 5 times fainter than the 90mm. So although the image appears the same size in both scopes, the 200mm will show a lot more detail.

But we have to remember that large scopes are more effected by seeing conditions. The 200mm may show this fine detail once every 10 seconds or so due to the turbulence in the atmosphere. I found the image in the 90mm scope to be very stable, the detail that the scope could resolve stayed in view constantly, as smaller scopes can tolerate bad seeing better than larger scopes.

Hope this helps.

Steve

[MidnightMinstrel]

Ok, beginning to understand things a bit clearer now....so does that mean some of those larger images we see in YouTube have been enlarged by a computer then?

[Alkaid]

Ok, beginning to understand things a bit clearer now....so does that mean some of those larger images we see in YouTube have been enlarged by a computer then?

Sorry for an absurdly late reply.

I am not am imager, so someone please correct me if I am wrong. I think that when a webcam is used, the image is amplified anyway by the nature of the webcam. So the vids on YouTube tend to have a barlow in there, then the webcam. That might result in a 2x or 3x amplification from the barlow, then the amplification of the image through the webcam on top. I think that's how they get the planets looking like tennis balls.

[jaqob]

Thanks for a great review

[TonyD]

Thanks for such a great review, Steve. I am in such a quandary about what scope to get. A few days ago I was totally focused (probably very old pun intended!) on a refractor like the TAL-100R or SkyWatcher Evostar 120. But the portability aspect of this smaller scope has got me thinking. I know myself - if the kit is too large or cumbersome to set up or get out then I will tend to avoid using it. Ahhh well. I'm in no hurry. I think with the excellent knowledge base one can acquire through excellent reports like yours, the one mistake I can make is buy the wrong type of quality scope, as opposed to a poorly-constructed model of the right type of scope from a disruputable manufacturer.

Tony

[camoscato]

I have an Evostar 90, and I can confirm everything Steve wrote in his excellent review. I'm new to astronomy, and this scope has been great for starting out.

I know myself - if the kit is too large or cumbersome to set up or get out then I will tend to avoid using it.

I leave mine set up in the garage, so it only takes me a couple of minutes to get going. Even if I had to take it down between sessions, getting it set up would take no more than 5 minutes to get it onto the mount and aligned. The whole thing doesn't weigh very much; one person can easily move it around.

Hope that helps.

[TonyD]

Thanks camoscato - it certainly does help. Out of interest, what mount do you use with it?

Tony

[John]

Thanks camoscato - it certainly does help. Out of interest, what mount do you use with it?

Tony

According to camoscato's signature the scope is on a Skywatcher EQ2 equatorial mount Tony.

[TonyD]

According to camoscato's signature the scope is on a Skywatcher EQ2 equatorial mount Tony.

Ah yes. Thanks John! Missed that one.

Tony

[Alkaid]

Hi TonyD, thanks for reading! I do like the Evostar, it's very portable, delivers good views and is very good value.

The scope is still residing at my Mum's house, but as I often use it when I visit she said I could part own it, so it now appears in my signature. It excels when one is short on time and just wants a 30 minute look at the moon or planets. Set up within 5 min, cooled within another 5 min, then you're away....

We (me, my wife and our son) are visiting my parents for Christmas....I am hoping to get some use from the Evostar during the next few days....will let everyone how In got on, weather conditions pending.

Merry Christmas all!

Steve

[andrew63]

Thanks for the review - a 3 to 4" refractor is a great telescope to use - especially with the weather we have - you can always get some observing in.

andrew

[TonyD]

Thanks for the reply, Steve.

Your comments above have been very helpful.

Convenience factor is going to be a major thing that informs my choice.

Good luck with your stargazing this holiday!

Merry Christmas

- Tony

[Catweazel]

Thanks for that solid review Steve.

I have the 120 Evostar, and it's a lovely scope. The 90mm has the benefit of being much more portable; I mentioned on another thread that the scope I use the most is my Megez 72 APO, for just that reason! Out of interest, how did you find the EQ2 mount with the scope, I wondered how stable it seemed? I might be looking for a low cost mount for the Megrez in the new year, rather than using it with the EQ5 for visual.