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would would i get for investing in a higher quality APO?

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#1 mantrain

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Posted 13 June 2018 - 03:25 PM

I keep thinking about a high quality refractor,and I feel that this is just an emotional appeal of something that I like but I am not sure it is grounded in any objective rationale. if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think you said your lower premium APO is 95% of the higher premium scope? What do you think I would notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to Newtonians?

if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think Don Pensack indicated that his lower premium APO is 95% of the higher premium scope? What do you one might  notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to larger aperture Newtonians?
Are refractors more sensitive to transparency, or seeing conditions?

Thank you



#2 hfjacinto

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Posted 13 June 2018 - 03:39 PM

I have a lower priced refractor and have looked through higher priced ones side by side, in typical NJ seeing and light pollution all I noticed was the guy with the more expensive refractor had a much lighter wallet. BUT this is in NJ, here the moon is a faint fuzzy, in places with better seeing and darker skies you will notice smaller stars and generally images with more contrast not to mention a superbly built scope with generally top notch focuser, but for me I can't see paying that much, all in all I'm happy with my lower cost scopes (and I use them for AP)

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#3 nicoledoula

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Posted 13 June 2018 - 03:40 PM

ES AR series or higher end ES ? If you have an AR 127 now you'll see a TON of difference when looking at planets and other bright objects. More aperture sees more messier's (answers all your messier questions, 3mm doesn't really count but might). Refractors are better when conditions are bad. Smaller refractors. When conditions are bad most peruse this forum or tend to life's other details instead.



#4 mantrain

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Posted 13 June 2018 - 03:45 PM

ES AR series or higher end ES ? If you have an AR 127 now you'll see a TON of difference when looking at planets and other bright objects. More aperture sees more messier's (answers all your messier questions, 3mm doesn't really count but might). Refractors are better when conditions are bad. Smaller refractors. When conditions are bad most peruse this forum or tend to life's other details instead.

I am talking triplets (APO). 



#5 OleCuss

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Posted 13 June 2018 - 03:56 PM

Get a good Stellarvue, William Optics, a Sky-Watcher Esprit, or maybe the FCD100 or FPL-53 lines from Explore Scientific and you may not really be able to tell the difference between them and the much more costly instrument.

 

You might be able to tell, but some of these very high-end instruments just aren't clearly all that much better.

 

I'd get one, however, that has a matched field flattener.  No matching field flattener would be a deal-breaker for me if my goal were to compete with the best of instruments.

 

Anyway, that's how I see it.  Those who are smarter and wiser than myself may see it differently.


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#6 mantrain

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Posted 13 June 2018 - 04:00 PM

Get a good Stellarvue, William Optics, a Sky-Watcher Esprit, or maybe the FCD100 or FPL-53 lines from Explore Scientific and you may not really be able to tell the difference between them and the much more costly instrument.

 

You might be able to tell, but some of these very high-end instruments just aren't clearly all that much better.

 

I'd get one, however, that has a matched field flattener.  No matching field flattener would be a deal-breaker for me if my goal were to compete with the best of instruments.

 

Anyway, that's how I see it.  Those who are smarter and wiser than myself may see it differently.

How does one get a matching field flattener? Is that something I can add on to my ES 127 APO?

 

Edit: My impression is field flatteners are for AP, but not fir visual...


Edited by mantrain, 13 June 2018 - 04:01 PM.


#7 hfjacinto

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Posted 13 June 2018 - 04:04 PM

You don't need a "matching field flatner", they are just for imaging. Several non OEM field flatners work as well. The most important part of the flatner is the spacing between the camera chip and the flatner lens. In my case I need 55MM, when I accidently changed it to 56.5 (a 1.5MM spacing difference) I noticed it in the edge stars (see below)

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#8 AndrewXnn

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Posted 13 June 2018 - 04:04 PM

It seems like that guys that are serious about visual, consistently have the larger Dobs.

 

12-14" for the portability; but 18-36" for ultimate visual.


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#9 hfjacinto

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Posted 13 June 2018 - 04:05 PM

Here is another image when I corrected the spacing.

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#10 Astrojensen

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Posted 13 June 2018 - 04:06 PM

I keep thinking about a high quality refractor,and I feel that this is just an emotional appeal of something that I like but I am not sure it is grounded in any objective rationale. if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think you said your lower premium APO is 95% of the higher premium scope? What do you think I would notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to Newtonians?

if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think Don Pensack indicated that his lower premium APO is 95% of the higher premium scope? What do you one might  notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to larger aperture Newtonians?
Are refractors more sensitive to transparency, or seeing conditions?

Thank you

Except when it comes to wide field, a 12" dob of reasonable quality will completely trash any 5" apochromat on deep-sky objects. All the globulars will show FAR more stars and the galaxies will show much more detail. That is not to say you can't have fun on deep-sky with a 5", of course you can, but one must also be realistic here.

 

 

Clear skies!
Thomas, Denmark


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#11 jay.i

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Posted 13 June 2018 - 04:18 PM

If you have an ES 127 Essential FCD-1 triplet, you'll get better CA control and a smoother figure by buying something like a Takahashi or LZOS or CFF or A-P, but you'll obviously spend much more, up to triple or quadruple the price for the same amount of aperture. Depending on your local climate, this might make sense. If you get clear skies a lot, with relatively low fluctuation in temperature throughout the night, and can leave the scope set up, even in the garage, then a big Newt makes a lot of sense IMO. If you must store a scope indoors with no garage, and have to set up the rig every time you go out, then a quality refractor makes a little more sense due to its ability to cool down quickly (generally, if you stay at 130mm or lower). Doublets are better than triplets in this regard. As for being "affected" by sky conditions, refractors acclimate faster and are not really subject to tube currents, but they aren't really "better" in bad seeing. The only way they are better is that they have less aperture and so you stay at lower magnifications where the atmospheric conditions are less apparent. That is my understanding when people say big apertures are "more affected" by bad seeing, but I could be wrong.

 

The ES127ED FCD-1 triplet is a good scope from what I have read, but if something is nagging at the back of your mind, wondering what it would be like to have even better optical performance, and you have the (financial) means to find out, you might as well give in. Buy used to save yourself some money in case you decide to re-sell and upgrade even further. Premium scopes are already very expensive on the used market, but even more so when purchased new. If you want to step it up and not mess around with any more buying and selling, grab a used TSA-120, log off of CN for a few months, and just enjoy it. If you have a beefy mount and don't want to downgrade your aperture, then save up a few more buckaroos and get a used TEC140ED. You could be very happy with either of these two scopes and I think they would show you that there is definitely a lot to be gained in upgrading from (still decent) mass-made Chinese optics.



#12 mantrain

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Posted 13 June 2018 - 04:25 PM

If you have an ES 127 Essential FCD-1 triplet, you'll get better CA control and a smoother figure by buying something like a Takahashi or LZOS or CFF or A-P, but you'll obviously spend much more, up to triple or quadruple the price for the same amount of aperture. Depending on your local climate, this might make sense. If you get clear skies a lot, with relatively low fluctuation in temperature throughout the night, and can leave the scope set up, even in the garage, then a big Newt makes a lot of sense IMO. If you must store a scope indoors with no garage, and have to set up the rig every time you go out, then a quality refractor makes a little more sense due to its ability to cool down quickly (generally, if you stay at 130mm or lower). Doublets are better than triplets in this regard. As for being "affected" by sky conditions, refractors acclimate faster and are not really subject to tube currents, but they aren't really "better" in bad seeing. The only way they are better is that they have less aperture and so you stay at lower magnifications where the atmospheric conditions are less apparent. That is my understanding when people say big apertures are "more affected" by bad seeing, but I could be wrong.

 

The ES127ED FCD-1 triplet is a good scope from what I have read, but if something is nagging at the back of your mind, wondering what it would be like to have even better optical performance, and you have the (financial) means to find out, you might as well give in. Buy used to save yourself some money in case you decide to re-sell and upgrade even further. Premium scopes are already very expensive on the used market, but even more so when purchased new. If you want to step it up and not mess around with any more buying and selling, grab a used TSA-120, log off of CN for a few months, and just enjoy it. If you have a beefy mount and don't want to downgrade your aperture, then save up a few more buckaroos and get a used TEC140ED. You could be very happy with either of these two scopes and I think they would show you that there is definitely a lot to be gained in upgrading from (still decent) mass-made Chinese optics.

Thank you,

the mount I have is AVX. I already have a big dob.



#13 Jon Isaacs

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Posted 13 June 2018 - 04:31 PM

What do you think I would notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

 

 

No difference. The difference comes when viewing the planets and even then the difference is subtle. 

 

The biggest difference is not between scopes but between observers.  Strive to be the best observer you can be and your equipment is good enough it won't get your the way.  Hours at the eyepiece. .

 

Jon


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#14 RAKing

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Posted 13 June 2018 - 04:33 PM

I keep thinking about a high quality refractor,and I feel that this is just an emotional appeal of something that I like but I am not sure it is grounded in any objective rationale. if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think you said your lower premium APO is 95% of the higher premium scope? What do you think I would notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to Newtonians?

if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think Don Pensack indicated that his lower premium APO is 95% of the higher premium scope? What do you one might  notice if I have an APM 130 and ES 127 side by side viewing Messier objects?

Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to larger aperture Newtonians?
Are refractors more sensitive to transparency, or seeing conditions?

Thank you

Here's my take on this dilemma --

 

Yes, for visuals, a bigger Dob can see more, but I did not like the ergonomics of the Dob - so I will gladly take my little refractor outside any night I can.  I am in this hobby for my personal enjoyment and I get more enjoyment from a nice refractor. 

 

I owned a Takahashi TSA-120 and it is one of the nicest refractors available in that size.  BUT I also discovered that I could see the same stuff with a Sky Watcher 120ED, which cost 1/3 the amount of the Tak.  Did it deliver 95 percent? 97 percent?  I don't know, but I enjoy the views through the SW 120 and don't feel cheated when I go out for a session.

 

So if you have a decent ED refractor, you probably won't see any benefit from buying a premium refractor of the same size.  You might get a better focuser and it might be put together better, but if each scope is able to work to its full potential, they will be very close.

 

Would I rather still have my TSA 120? Sure.  The Tak is a great scope and maybe I would smile a little more when I looked at it, but I still don't think I could split a tighter double or see the Messier objects any better.  Maybe I could tell the difference on planets, but they aren't really my thing.

 

My .02, flowerred.gif 

 

Ron


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#15 Richard Whalen

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Posted 13 June 2018 - 05:06 PM

Depends on how picky you are. What a high end APO brings to the table is better glass, design, mechanics and optical quality/coatings. On DSO's you would be hard pressed to fine much difference other than a bit better contrast and sharper stars.

 

On the planets and moon you will see more of a difference. How much? Depends on the optical quality of your current refractor and the one you would buy. 



#16 havasman

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Posted 13 June 2018 - 05:06 PM

I already have a big dob.

Then you have at hand the answer to how they'll perform for DSO observing. I often take my 115mm triplet along to the dark site and half the time i may use it briefly. The 16" is just so much more useful for almost 100% of my observations. Once in a great while I take only the refractor and binoculars but those sessions have very different observing plans than my normal fare.

 

If you go look through your 127mm and through your big Dob you have the answer. A top rank 130/140mm refractor will not compare that much differently.


Edited by havasman, 13 June 2018 - 05:06 PM.

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#17 OleCuss

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Posted 13 June 2018 - 08:24 PM

How does one get a matching field flattener? Is that something I can add on to my ES 127 APO?

 

Edit: My impression is field flatteners are for AP, but not fir visual...

If your Explore Scientific is of the FCD1/FPL-51 variety you do not, IMHO, have a true (photographic) apochromat.  They just aren't quite that good and their focuser isn't desirable for imaging.  I'd call it a visual apochromat because the 102mm I had was very good for visual work.

 

If you are looking for a visual instrument and you have any concerns about cost, then I'd advise you not to get a triplet at all.

 

For visual purposes there is (IMHO) insufficient benefit to going with a triplet.  A good ED-Doublet will be close enough that many (maybe almost all) of us won't notice a difference in optical quality and our cool-down will be faster, our price will usually be lower, and we can either use a cheaper mount or put a bigger-aperture OTA on the same mount because it doesn't weigh as much.

 

For that matter, by most standards a far cheaper Dobsonian with a nice coma corrector is going to spank the view you'll get from a really good 127mm triplet apochromat.

 

Upshot is that I'd not consider buying a good triplet refractor in the 5" or larger aperture range unless I were planning to do AP with it - or just had plenty of money to spend for a beautiful functional work of art (which a superb refractor is).

 

So far as a matched field flattener?  I'd look to folk like Stellarvue, WO, ES, Sky-Watcher, Astronomics, etc. and I'd check to ensure that they have a flattener designed for that particular telescope.  Not just a flattener which has their brand name on it and is supposed to work with scopes in that range of focal lengths or focal ratios.  The focal reducer is designed and sold for use with that particular OTA.  That way if you find that you don't have great correction the seller/manufacturer of the flattener can't say that it is the fault of the OTA and the seller/manufacturer of the OTA can't say you have the wrong flattener.

 

Some years ago I had a very good triplet apochromat which was beautifully corrected and not overly costly.  I wanted to use it with focal reduction and asked the maker/seller which reducer/flattener I should use.  They advised me to get a particular one which is made by a great optics maker/seller.  The correction wasn't bad, but you could still see fixable field curvature when you approached the corners of the images.  The OTA was great and the reducer/flattener was great - but together they were good but not great.  I sold both the reducer/flattener and the OTA.  I don't have enough time to spend it trying to fix optical problems in processing.

 

Now I have an NP101is.  It's a Petzval which (when paired with an APS-C sized sensor) does not have a significant field curvature.  If I had a full-frame sensor I could have field curvature problems but I can buy a matched flattener to fix that.  I was also able to get a reducer designed for that OTA which will give me a nice flat field at an even faster focal ratio and still fully illuminate my sensor.  This makes for very nice imaging.

 

I've also a WO Gran Turismo.  Good triplet and they sell a field flattener which is marketed for that particular OTA and does a very nice job which I find within my acceptable/beloved range.

 

Net effect is that from my perspective I'd not get an apochromat for almost anything but imaging.  I'd not get an apochromatic OTA which I can't get with a field flattener sold by the OTA maker and specifically matched for that particular OTA.  And then I'd test it to see if the field curvature is beautifully corrected - and if not I'd send both units back as being of unacceptable quality.

 

A further note?  I've a Mak-Newt (Comet Hunter).  Bigger aperture and has great optics for both visual and for imaging.  I don't really like using Newts or Newt variants on a GEM for visual use, but if you don't mind that you can get a bigger aperture scope at a relatively low cost which I'd contend will come fairly close to a triplet apochromat (but not quite equal it IMHO) in quality and will exceed the triplet in light-gathering and do it with very fast optics and a nice focal length (from my perspective).

 

But what works for me is not necessarily what works for anyone else.



#18 Dennis53121

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Posted 13 June 2018 - 08:42 PM

I keep thinking about a high quality refractor,and I feel that this is just an emotional appeal of something that I like but I am not sure it is grounded in any objective rationale. if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think you said your lower premium APO is 95% of the higher premium scope? What do you think I would notice if I have an APM 130 and ES 127 side by side viewing Messier objects?
Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to Newtonians?
if I sold my ES 127, and purchased something premium in the same relative aperture, what would I gain? I think Don Pensack indicated that his lower premium APO is 95% of the higher premium scope? What do you one might  notice if I have an APM 130 and ES 127 side by side viewing Messier objects?
Also, how do you feel that these APOs perform viewing messier catalogue objects in average seeing, compared to larger aperture Newtonians?
Are refractors more sensitive to transparency, or seeing conditions?
Thank you


I would suggest that you attend a star party, setup your scope next to someone with a AP, Tak, TMB, etc. and ask them if youcould share a peak at a few objects. Compare the views in their scope to your scope at a similar power. Then I think you can make the decision yourself as to if the rule of diminishing returns is still worth the upgrade for you or not. I myself
have my own opinion which you can probably tell from my signature but I believe half the people on this forum would agree
with me and half would not.

Dennis
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#19 mantrain

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Posted 13 June 2018 - 08:43 PM

"For that matter, by most standards a far cheaper Dobsonian with a nice coma corrector is going to spank the view you'll get from a really good 127mm triplet apochromat."

 

I have a big dob, if one considers 16" big (it's all relative). I got my APO though can do things the Dob cannot. For one thing, it can fit on an AVX mount and have great goTo features. But more importantly for me, it offers higher quality views. I never was able to get four stars out of E Lyrae from my 16" Dob, nor from my friend's Dobs either. It is like a bazooka being used to hunt rabbits. a 22 caliber would be better.



#20 Cajundaddy

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Posted 13 June 2018 - 08:43 PM

On Messier objects at typical viewing magnifications doubt anyone would notice a difference in double blind testing.  Only when you really push the mag or view very bright objects will the premium scope reveal it's pedigree.  If you spend a boatload of $$ you will likely get very nice hardware, focuser, and customer support if these are important to you.



#21 mantrain

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Posted 13 June 2018 - 08:46 PM

"For that matter, by most standards a far cheaper Dobsonian with a nice coma corrector is going to spank the view you'll get from a really good 127mm triplet apochromat."

 

I have a big dob, if one considers 16" big (it's all relative). I got my APO though can do things the Dob cannot. For one thing, it can fit on an AVX mount and have great goTo features. But more importantly for me, it offers higher quality views. I never was able to get four stars out of E Lyrae from my 16" Dob, nor from my friend's Dobs either. It is like a bazooka being used to hunt rabbits. a 22 caliber would be better.

edit: when I first got my APO last month, the first thing I did when  I took it out was to test it on E Lyrae. When I looked in the EP I knew that for what I paid, I got what I wanted. 



#22 havasman

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Posted 13 June 2018 - 09:02 PM

I never was able to get four stars out of E Lyrae from my 16" Dob

You should, IMO, start there and fix that scope. It is seriously underperforming w/o a doubt.


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#23 mantrain

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Posted 13 June 2018 - 09:16 PM

You should, IMO, start there and fix that scope. It is seriously underperforming w/o a doubt.

maybe but I have looked into my friends 18" obsession and he never gets four crisp stars either. you see, with dobs there are factors such as seeing, heat dispersion, collimation, that more affect it than for a refractor.



#24 turtle86

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Posted 13 June 2018 - 09:21 PM

You should, IMO, start there and fix that scope. It is seriously underperforming w/o a doubt.

I agree.  Just want to add that the fix probably entails no more than getting it well-collimated.



#25 mantrain

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Posted 13 June 2018 - 09:26 PM

I know my friend w the 18" is rather obsessive-compulsive about collimation and still no 4 separate distinct start with space bw them. But it is wworth exploring..




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