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Which cheap refractor would you choose?

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#1 neccoboy

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Posted 07 December 2018 - 10:28 AM

Hi, I'm looking for a little help choosing a refractor. I've been going back and forth on which of these two refractors I'd like to purchase. Mostly visual, and maybe try some AP (but I'll most likely be using an Alt/Az mount which will most likely limit that). This scope will be more of a grab and go I can setup on my lunch at work. They are both cheap Achromat's. 

 

Both are Visionking's

 

90mm f/5.6 500mm

 

https://www.ebay.com...353.m1438.l2649

 

or 

 

80mm f/7.5 600mm

 

https://www.ebay.com...353.m1438.l2649

 

I've been trying to find more information, but there are not many people buying these I guess lol. Now I'm guessing they will both have CA, but will the 90mm have more? I'd be more after DSO's. I really don't want to spend a lot as you can probably tell. Any help or advice would be greatly appreciated

 

 



#2 JGass

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Posted 07 December 2018 - 10:39 AM

All other things being equal, the faster f ratio scope (the 90mm) will show more CA.  That's because of the greater dispersion of the incoming light due to stronger curvature of the lens.


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#3 cheesified

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Posted 07 December 2018 - 10:46 AM

you could try searching for Meades on Aliexpress



#4 neccoboy

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Posted 07 December 2018 - 10:47 AM

Would the 90mm be better for DSO viewing/AP due to aperture?

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#5 donniesoprano

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Posted 07 December 2018 - 10:59 AM

Lots of people are going to tell you to get a Dob, many will try to steer you away from a refractor for a multitude of reasons, I won't do either.  I think a refractor is an excellent scope, first or companion to others.

 

Just curious, but why are you considering these two, in particular?  Based on your 'ClearSkyClock', you're in MA, so there's plenty of options that are stateside.

 

I'm not trying to sway you away from your choices, however, these are both achromats, as you've said.  The mechanical build quality may be nice but the 'guts' of the optical train are still going to be a relatively inexpensive achromat.

 

I would consider an inexpensive 80mm f/5 like the Meade Adventure Scope or something similar.  It's going to be measurably lighter and thus easier to mount in a stable manner.

 

That said, if you're going to buy one of the ones you've listed, I'd suggest getting the one that will least tax the mount you plan to use.  Nothing ruins a viewing experience, for me, as much as inadequate mounting.  I can't speak to VK's quality control, but CA will be an issue in both.  Probably won't matter for your use (DSO), thus I would consider the mounting more than the false color.

 

ds



#6 MalVeauX

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Posted 07 December 2018 - 11:21 AM

Those seem quite expensive for achromatic doublets.

 

DSO is best with a larger aperture. The difference between the 80mm & 90mm is not a big difference, but the focal-length can matter a lot and the focal-ratio with respect to what you can view and at what powers with various eyepieces. In general, the longer focal-ratio refractors perform better. They also tend to be physically long, heavier, etc.

 

I would suggest you look for an Orion 120mm F5 achromatic refractor, in those price ranges, for DSO. With a 2" focuser, you have a lot of nice wide field options with this scope. With a 2" 38mm 70 degree, you get a 4.4 degree FOV with a 7.6mm exit pupil. Lots of light, very bright, wide field. With a 1.25" 24mm 68 degree FOV eyepiece, you get 25x magnification, 2.7 degree FOV and 4.8mm exit pupil, very nice for sweeping DSO. And a 6mm or 8mm would be very complimentary to view specific DSO at higher magnification in the 75x and 100x ranges.

 

Very best,


Edited by MalVeauX, 07 December 2018 - 11:38 AM.

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#7 gene 4181

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Posted 07 December 2018 - 11:30 AM

  Either looks  nice  ,  flip a quarter  and decide .   SO what if it has a bit of color ,   smile.gif  .   



#8 sg6

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Posted 07 December 2018 - 12:12 PM

Where are you located?

Really helps when asking something like this.

 

My cheap refractor was a Bresser 102/600. So 102mm aperture better for DSO's and at f/6 not great for CA but not that bad.

 

Have you got a mount? A scope on it's own is pretty useless.

 

The 90/500 will be a rebrand, someone has written StarSky on the side, sometimes they write ES on the side and an assortment of other names.

The 80/600 will be a rebrand but not sure who else sells an 80/600, ES have an 80/640.

 

Both say they are located in China, so it will likely be considered an import and that could cause unwanted problems.

 

Main question is back to where are you?

Reason: The 90/500 you link to is $270, the ES 90/500 here:

https://explorescien...ts/fl-ar90500az

is $85.

 

The ES 80/640 here: https://explorescien...ts/fl-ar80640tn

is $150

 

The Visionking scopes seem a high cost by comparison with very similar scopes. Agree that focusers may be different/better.

 

Neither are really good for photography, immaterial of what is printed in the description.


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#9 vtornado

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Posted 07 December 2018 - 12:37 PM

Hello neccoboy and welcome to cloudy nights.

 

First there is a rule of thumb called the chromatic abberation ratio, here is a chart.

https://www.cloudyni...erration-chart/

In general green is good, yellow is tolerable and red has problems.

 

To find it, change the aperture of the scope to inches, then divide the f ratio  by that.

For example a 90mm f.5.6 is  5.6 / (90/25.4) = 1.58

The 80 7.5 = 7.5/(80/25.4) = 2.38.

 

Now that being said ...

There are lots of variables in this number.

In general CA becomes more of an issue when the power of the scope is rasied.

If you are using low power on dim objects it is not a problem.

Where it becomes bothersome is if you want to look at planets, or split double stars.

 

For planets,  I would not go lower than 2 on the chart.

I also find that the moon can tolerate higher CA and not have details washed out.

 

One issue to be raised is that both of the scopes your are looking at are sourced directly from China.

I know just about all scopes come from China, but if there is an issue with yours, you are going to

be out of luck.  I bought some electornics accidently through ebay directly from China and the thing did not

work.  After rounds of useless help from the help desk I asked for a refund, and shipping the thing back

was more that the item was worth, so I just threw it away.

 

Do you have dark skies?  If you don't, viewing many DSO's is going to be underwhelming.

Only a hand full of brighter ones will be available to you.  And in order to get good views,

the more aperture the better.  In general 100-120mm for a refractor is the sweet spot.

where price, performance, and portablility are optimized for visual.

 

For AP most people start out with a small ED refractor.



#10 SeaBee1

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Posted 07 December 2018 - 12:40 PM

The main thing to keep in mind is the aperture/goal quotient you are presenting. There are some bright DSOs that either of those scopes will give you a look, but many... maybe most, will be large and diffuse... in other words - DIM. Add in light pollution and the dim ones basically are a non starter. Think nebulae and galaxies. Granted, some will be visible, but most are gonna be tough.

 

Where I think those apertures will be usable is looking at open clusters and some of your wider doubles. The wide field of view will capture open clusters nicely, though you will not pick up the dimmer members of the target. Some observers appreciate this kind of view. CA will not be an issue on these targets.

 

Mind you, GIANT aperture is not necessary for viewing a lot of DSOs, but at the apertures you are considering, I think you will be disappointed. IMHO...



#11 PNW

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Posted 07 December 2018 - 01:01 PM

I really enjoy my Infinity 102, and at around $200 it's hard to beat for an entry level scope.


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#12 Sequimite

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Posted 07 December 2018 - 01:24 PM

What I actually did buy in that price range was a Tele Vue Ranger. The $350 price included TV diagonal, TV 20mm Plossl and case. I put it on a heavy duty aluminum video tripod which was $6 at Goodwill.


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#13 sg6

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Posted 07 December 2018 - 01:34 PM

Just as a follow up I found an 80/600, sold by TS Optics:

https://www.teleskop...t-Schellen.html

 

It is 114 Euro so $100 or a bit less.

That Visionking range is looking like high cost items. More the double is a bit much.

 

When I display the items here the seller is given as visionking-uk, price is US$'s, site is the US ebay one and the location of the items is SHENZHEN, China.

 

Is it just me or is it a bit odd?


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#14 Voyageur

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Posted 07 December 2018 - 02:24 PM

Just as a follow up I found an 80/600, sold by TS Optics:

https://www.teleskop...t-Schellen.html

 

It is 114 Euro so $100 or a bit less.

That Visionking range is looking like high cost items. More the double is a bit much.

 

When I display the items here the seller is given as visionking-uk, price is US$'s, site is the US ebay one and the location of the items is SHENZHEN, China.

 

Is it just me or is it a bit odd?

Red flag to me, too. eBay says the seller is based in China, so “uk” is meaningless and misleading. I wouldn’t order an expensive item to be shipped from China.



#15 epee

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Posted 07 December 2018 - 02:43 PM

They look cool and high quality but I seriously doubt they will serve you any better than an Orion, Meade, or Celestron of the same quality. If you shop hard you might even find one in that price range that comes with a decent mount.

 

 

 

 

Well, that wasn't hard.

 

Here's a super beginner scope, by a very esteemed company, and well known, highly regarded vendor on a highly praised mount for just $50 more than the "mystery/maybe" scopes you were looking at....

Not meaning to sound harsh, but this is just SUCH a better way to go.

 

https://optcorp.com/...4-refractor-ota


Edited by epee, 07 December 2018 - 02:52 PM.


#16 sickfish

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Posted 07 December 2018 - 03:21 PM

If he is from the north east,   buy from a dealer in the U .S.

There are plenty.

 

For a scope suggestion, maybe something like a Starblast 4.5

Not for AP but good all round 

AP is a different rabbit hole to go down.


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#17 sickfish

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Posted 07 December 2018 - 03:28 PM

I know it's not a refractor but it gives more aperture.



#18 Mountaineer370

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Posted 07 December 2018 - 03:31 PM

If you're open to buying used, there are a few nice refractor options in the classifieds right now, in the 80mm to 100mm range, well within your price range.  If you're set on new, there are a lot of well-regarded dealers here in the US.  I would never be comfortable buying a telescope on eBay that's being shipped from China. 



#19 mic1970

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Posted 07 December 2018 - 03:52 PM

I would look here on the classifieds also.  Might find a good scope in your area.  I really like my Orion I got used.  New ones are in the same price range and you have support to call.



#20 neccoboy

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Posted 07 December 2018 - 04:55 PM

Thank you all for the help. Instead of addressing everyone's replies in quotes, I'll just try and sum it up

 

I'm from MA. I'm going to be using this scope on lunch at work mostly, so it would have to be fairly quick to setup. I work around Boston, so the skies are not good

 

I own a Orion 8" f/3.9 Newtonian that I have used on my Celestron CGEM.

 

I'm new to refractors although I've owned a few. One used Vixen 80ED, a new Orion ST120, and a Altair Astro 80mm super triplet. I used the Vixen once and ended up selling it. Bought the Orion and Altair, never used ether sold both at used prices. 

 

So I'm not completely new, just don't have much experience with refractors. One thing that kind of bothers me with refractors is a fixed dew shield, for me it needs to be retractable. I have a Celestron GT Alt/Az mount. I think the wieght limit is 6lbs?

 

The Meade adventure scope only has a 400mm focal length, for some reason that just doesn't seem good to me. The TS Optics scope seems ok, even with the fixed dew shield :p but the focuser looks cheap. The Vixen is an f11, so not so great if I want to dable in AP. I appreciate the suggestions

 

I did order the VK 90/500 early this morning, and about an hour later I changed my mind. The seller cancelled my order with out issue. Looking for more insight, I decided to post here. I had thought these scopes were reasonably priced since they come with some of the higher end features? Now the quality of these features is the question. For instance the dual speed crawford focuser

 

I think I'd be better off with the VK 80/600 f7.5, but may wait to see if something turns up on classifieds. I prefer not to buy used



#21 Rock22

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Posted 07 December 2018 - 05:20 PM

I bought a Visionking 80mm apo triplet (f/7) for just under $400 on e-Bay.  It is built like a tank, has a very functional retractable dew shield, came with a pretty good 2" diagonal, and gives very good views (through 2 convex FK-61 ED crown lenses, 1 concave H-LaF2 flint glass lens).  It is the same as the Barska Magnus 80mm apo triplet, and I took the gamble after reading about it on CN.  The price has been going up, and I think it's the lesser known brand name and that the scopes ship directly from China that makes buyers think twice about getting one.

 

There is a thread about the scopes the OP is looking at, and the reviews are mostly positive, though there is still much skepticism.  And for good reason in my experience..

 

The 2" focuser, while seemingly solid, came with a bent focuser axle making the fine focuser knob useless. I read this happened to others who got the Barska version.  I e-mailed Visionking and sent them pictures.  They sent me a new knob unit, and the focuser works well now.

 

The focuser set screws (to lock and tighten the drawtube) have been known to arrive damaged, and this was my case as well.  I replaced them with nylon set screws and the drawtube works well now.  Still, I replaced the focuser with a 2" Crayford from Lunt (using a Celestron 80ED focuser adapter) because the stock focuser could not handle the weight of my heavy 2" eyepieces or DSLR, though it could handle other eyepieces or a USB camera very securely.

 

I also added rings and a dovetail bar.  Altogether, the scope cost me $550, but still significantly less than the triplets of better known brands.  Since this is my only apo triplet experience, I can't say that the Visionking scope I have is great, but I can say the views are clear and color free, like my mak.

 

Nonetheless, the views are way better than those in my ST80s.  There is no CA, except when using a 3.5mm eyepiece.  (Does anyone know why this might be the case?)  Stars look clear with no false color, and the moon has no yellow or purple fringing. I am very pleased with the Visionking scope I have.  If the OP does buy one, get it from Visionking directly to be safe.  They were very responsive.

 

Not sure, though, that I would shell out $270 for an 80 or 90mm achromat with tube rings and a dovetail bar (but no diagonal?).  Might as well go with the Visionking apo in that case.  Like others above mentioned, why not get a Meade, Orion, Celestron, ES, Skywatcher, or AstroTech for that amount of money?


Edited by Rock22, 07 December 2018 - 05:25 PM.


#22 neccoboy

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Posted 07 December 2018 - 05:31 PM

Thanks for the input. I've followed the Barska thread throughout. Those APO's are around $430 now, and the focuser upgrade from what I've read is a necessity for those scopes. More money than I can currently dish out, I'm trying to keep this under the wife radar. The links I listed were the higher end prices for those scopes. The lower end price of the VK 80/600 is $200. I'm pretty sure that the VK seller on ebay is the actual producer of the scopes. At least thats what one of the ads mentioned



#23 rogeriomagellan

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Posted Yesterday, 06:38 AM

While I was reading Tim's posts, I remembered the Gskyer refractors right off the bat. One of the advantages is that they come with an Alt-Az mount and they can be ordered straight from Amazon. 

 

https://www.amazon.c...y/dp/B00XQLV11M

 

https://www.amazon.c...2_t1_B00XQLV11M

 

In terms of optical quality, I have no idea if they outperform or not any of the VK refractors mentioned in post #1. What I know is that they are cheaper and may be free from shipping costs. The 80mm is really portable but the 90mm also has a focal ratio that is still within the idea of rich field/wide field telescope. 

 

Frankly, I'm totally pro three-digit aperture size refractors. Now that being said, my minimum favorite aperture is 4" (102mm). Aside from the ES AR102, the other achromat that appeals a lot to me is the Bresser Messier AR102 f/5.9. Many guys like the latter more just because of the smaller dew shield. It's been on my radar screen for a sometime now. To my way of thinking, it is perfect for a carryall bag. The whole issue is that it is seldom available for sale in U.S. soil. 

 

https://www.teleskop...00-mm--OTA.html

 

However, since you are looking for a fast achromatic refractor because you want to set it up on your lunchtime at work, a fast 80mm refractor makes a lot sense. Your primary aim seems to pick just a very small number of objects. 

 

Just pondering here. If you want a fast response and be able to read more reviews on CN, maybe you should consider one of the mass-produced U.S. brand achromats. 

 

On the other hand, one of the features that lured my attention about those links posted by you is that those tubes come with a 2" Crayford-style focuser which is regarded as a must by most guys. Could only this particular feature tip the balance in its favor? 

 

By the way, do any of those VK refractors come with a 2" dielectric diagonal mirror? 




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