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Achro vs ed vs Apo and a quark. Any comparisons?

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#1 NorthernlatAK

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Posted 24 February 2020 - 11:49 PM

I am trying to decide what scope to get with a quark. Is it worth getting an ed or an apo over an achro? My choices are either an 80mm ed or a 100mm achro. I will probably get a cg4 for a mount and this is for strictly visual. Direct comparisons are preferable. Perhaps even better would be 100mm ed f7 vs 100mm achro f7.

Edited by NorthernlatAK, 25 February 2020 - 12:38 AM.


#2 MalVeauX

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Posted 25 February 2020 - 08:00 AM

Heya,

 

It won't matter hardly a bit, optically. It's focusing a single wavelength of light, so the correction isn't doing anything there. The bigger picture is the overall figure and things like SA. Lots of HA scopes are singlets because again you're not needing to correct several wavelengths of light. That said, a good achromatic doublet is going to be a safe bet. A good ED doublet will also be a safe bet, and cost more, but you likely will not necessarily gain anything special. I will say that most inexpensive achromats these days have poor focusers, and for a heavy train including a Quark & Binos for example you'd want a much better focuser. Most entry ED doublets at least come with better focusers in general (though still maybe not superb). It's also worth noting that an achromatic doublet can be superior to an ED doublet for this, again, with better figuring. A long achromatic doublet for example will have better figure & SA than a short, fast ED doublet when it comes to single wavelength performance like this in a lot of instances. Almost all the solar scopes you can buy are using achromatic doublets, very few are using ED configurations other than the upcoming modular Lunt's (brand new). For a Quark's purpose, an ED element has no advantage in and of itself (again figure and SA control is more important).

 

So instead of splitting hairs on achromat vs ED, I would instead suggest you look at the overall scope build and specifically consider the focuser quality (even if you have to upgrade it) in terms of cost.

 

I would look at a Celestron Omni XLT 102mm F9.8 achromatic doublet with an upgraded focuser, or something like a T.S. 102mm F11 ED (because it comes with a great focuser and is modular for bino use and would be excellent at night too). Otherwise, look into a SkyWatcher 100ED F9 with an ok focuser and/or perhaps an AstroTech 102mm F7 ED as they have ok focusers too. Just depends on budget and if you want to have double duty at night or not. If this is for dedicated solar use, I would just get a good achromatic doublet with the best focuser you can get on it (even if you have to upgrade it yourself).

 

And I highly recommend a pair of binoviewers with 25~32mm eyepieces. You won't need a corrector to use them with the Quark, so focus won't be a problem either. It's a stunning view with both eyes.

 

Very best,


Edited by MalVeauX, 25 February 2020 - 01:59 PM.

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#3 AposkiiLola

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Posted 25 February 2020 - 04:34 PM

Dont spend more money for an APO or ED telescope unless you plan on doing some other serious visual observation of the moon planets and stars,  put more money into your mount and focuser.   This is what matters most in all aspects of telescope ownership.

 

100mm x 1000mm is a great start for the quark, but after 30 days you will want 150mm.

 

Get the explore scientific first light 127mm achromat to use with your quark, and  you will be at the comfort zone for at least a year.   (put a better focuser on it and your golden)

 

 

My two cents,  In terms of optics Strehl ratio is all that matters and most companies do not publish that data,  thats what you are paying the big bucks for. Higher strehl..

 

http://www.rfroyce.com/standards.htm


Edited by AposkiiLola, 25 February 2020 - 04:59 PM.

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#4 NorthernlatAK

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Posted 12 March 2020 - 03:50 PM

Thank you guys for saving me some money. I just ordered the Celestron 102 Omni XLT with cg4 mount and a gso crayford 96mm dual speed focuser to start. I have my eye out for a used quark, and also need a decent diagonal. Any suggestions for a good mid-priced diagonal?

#5 cptbobrfh

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Posted 12 March 2020 - 04:35 PM

Di-electric diagonals are very good for using on your Celestron 102 Omni XLT.They are relatively inexpensive.You dont need a high end,expensive one.You can use it with your scope for nightime star observing,and daytime solar observing. They are much better quality than the standard/stock diagonals you usually get from the manufacturer. IMHO,start with a basic 1"1/4 " di-electric diagonal,and if you get the Quark,use 1"1/4" 25mm and 32mm Plossl eyepieces. Good luck and enjoy!

Bob



#6 NorthernlatAK

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Posted 14 March 2020 - 03:14 PM

I ended up ordering a wo dielectric dura bright 1.25 carbon fiber diagonal. The scope should be here by the end of the month. Now I just need that one last critical component...


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