Refractor for planetary observation.

[tico]

Hello,
I'm looking for advice on which refractor model can give better results in planetary observation, I'm looking for one between 3 "and 4" in diameter ... I don't know if an achromatic with a long focal length is better or if one with ED or APO lenses. ..
I would be delighted to hear your opinions and advice.
PS: I have ever observed by some Newton or SC and the images are very unstable, very shaky, they lack as contrast ...
Thank you very much.
Tico.

[johninderby]

Leaving out Tak for the moment in the more affodable range here are a few suggestions.

ScopTech 80 / F/15. Japanese made long focal lengrh scope that  gives great views for the money.

https://www.firstlightoptics.com/scopetech-telescopes/scopetech-stl-80a-maxi-80mm-f15-classical-refractor.html

Skywatcher ED100. Nice doublet ED scope. Could do with a focuser upgrade though.

https://www.firstlightoptics.com/pro-series/skywatcher-evostar-100ed-ds-pro-outfit.html

StellaMira 80 ED F/10 . Much better build quality than the SW ED100 and great optics with no noticeable CA and a nice focuser.

https://www.firstlightoptics.com/stellamira-telescopes/stellamira-80mm-ed-f10-refractor-telescope.html

Edited September 15, 2020 by johninderby

[John]

The advantage of the ED doublets is that they can have good colour correction in a tube length that can be handled by a more modest mount.

An F/7 ED doublet should have similar or better colour correction than an F/12 achromat of the same aperture.

 

 

[John]

This topic might get more input if I move it to the scope discussion section, leaving a link here.

Would you like me to do that ?

[tico]

Yes, thank you John!!

Tico

[HollyHound]

On 15/09/2020 at 16:40, johninderby said:

StellaMira 80 ED F/10 . Much better build quality than the SW ED100 and great optics with no noticeable CA and a nice focuser.

https://www.firstlightoptics.com/stellamira-telescopes/stellamira-80mm-ed-f10-refractor-telescope.html

I can certainly also vouch for the StellaMira as giving fantastic, clean, contrasty planetary views, but have no experience with those other scopes mentioned by @johninderby

[John]

I had one of the very early Skywatcher ED100's. Blue tube back then. It was an excellent scope. Roger Vine is a very experienced observer and reviewer - see what he says on the ED100 on his "best buys" section (bottom of page):

http://www.scopeviews.co.uk/BestBuys2020.htm

 

 

[SiriusB]

Depending on your budget... A 4" Achro or Apo,will be much more satisfying than a 3" apo for planets. IMO

I've found an 80mm ED very close to a 4" achro on deep sky, but for planets, i'd pick even the 4" Achro every time,(resolution)

So much the better if you can stretch to the 100ED previously mentioned.

 

 

 

 

 

[RobertI]

Something like this might be an excellent compromise - ED glass, manageble focal length, well specced, well made and nice price. TS do an identical version. I can confirm the practicality of a 4" F7 scope!

[mikeDnight]

I'd aim for an ED rather than an achromat and I wouldn't be too fussed about which one. I'm a firm believer that a good observer will get more out of a lower cost ED than a medeocre observer will get from a high end refractor. In reality, the performance gap between say a 4" fpl53 ED and a 4" fluorite apo has narrowed dramatically over the last 20 years, and definitely not worth losing sleep over. Just aim for the best you can afford, but bear in mind that a good quality diagonal and good quality eyepiece will make it sing. 

[SiriusB]

22 hours ago, mikeDnight said:

I'd aim for an ED rather than an achromat and I wouldn't be too fussed about which one. I'm a firm believer that a good observer will get more out of a lower cost ED than a medeocre observer will get from a high end refractor. In reality, the performance gap between say a 4" fpl53 ED and a 4" fluorite apo has narrowed dramatically over the last 20 years, and definitely not worth losing sleep over. Just aim for the best you can afford, but bear in mind that a good quality diagonal and good quality eyepiece will make it sing. 

But, Mike, Would you choose a 3" ED over a 4" Achro ~for planetary, if you were on a tight budget?

Just curious, seeing as how you magic great sketches out of modest aperture i'm not going to argue.

[mikeDnight]

2 hours ago, SiriusB said:

But, Mike, Would you choose a 3" ED over a 4" Achro ~for planetary, if you were on a tight budget?

Just curious, seeing as how you magic great sketches out of modest aperture i'm not going to argue.

Unless the 4" achromat with long focal length and of very good quality, I'd probably choose a good 80ED.  I used to own a very nice 80mm Equinox that was a remarkable little scope. Often I'd take it out for just a quick few minutes observing before bedtime and still find myself sat on a frosty garden bench an hour later. I've attached a pic of the 80ED I owned and some quick sketches I'd made, (I used the inside of a roll of selotape as a template hence the poor outline). As you can see from the second sketch of Jupiter, the Great Red Spot was easily seen. Not shown on the sketch but still very memorable to me were the jet black shadow transits that at times crossed the disk. Even the subtle wispy cloud tops of Venus revealed themselves. 

Edited September 17, 2020 by mikeDnight

[Highburymark]

I’d back up Mike’s comments about the Equinox 80 - even though it’s a relatively fast F/6.25, it’s a very capable planetary performer (though does show limited CA on bright objects), and Mike’s planetary sketches are an accurate depiction of what I saw with mine under excellent seeing conditions. 
But the market’s changed a bit since I paid £550 for my 80ED new In 2014 (as Mike said, you also need to factor in a decent diagonal). You can now get a 102ED for £465 - that’s a very competitive price for a 4” semi apo. Over 60% more light capture than an 80mm. 

[A McEwan]

OP probably has read these suggestions now, and generally the recommendation is for a 3-4" ED or achromat. 

I agree, but I'd suggest going for as large an aperture within the budget that you set yourself, whether it be ED or achro.

If going for an achro, don't go for a "shorty" fast f-ratio one: stick to something like f8 or more.

There are sometimes 100mm f11 achros available (like the Lyra one I used to have) which are excellent, or a 100mm f9 ED Skywatcher.

If you can afford it, a 120mm achro f8.3 is a good value for money scope but yes it will show some false colour. The 120mm f7.5 ED version has very good optics and is a great planetary scope.

It's probably one of the most discussed topics of conversation in Astronomy, so there will be plenty of opinions on it online!  

Good hunting!

[nfotis]

On paper, the Sky-watcher 100ED looks like a good refractor telescope for planetary observation (the focuser problem mentioned on the FLO link is a bit worrying, though).

What's the mount load limit and the budget limit?

N.F.