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is 4 inch enough for serious planet observing?

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#51 N-1

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Posted 17 November 2020 - 04:18 PM

Yesss, I made a totally senseless decision and pulled the trigger for the 102mm F11 ED refractor at TS telescope  services. I am exited. I know that it is not a decision made with the head.... there are scopes around for the same or not substantially more money that will blow it away but hey, I like long refractors.  I see it as a little corona present.... working at home all the time, a man needs new toys now and then. lol.gif

smile.gif smile.gif smile.gif smile.gif

I'd like to say good choice but haven't received mine yet so can't comment fingertap.gif

My rationalisation was that we're virtually living on the beach and I don't want to subject my FC76 to these conditions (the same would apply if it was a Questar). But I still want refractor views from home, with a bit more oomph than the Galileoscope. The TS ticks all the boxes, good IQ, well-built, and less of a disaster if damaged by sand, salt or cleaning. The aim was not to get a meaningful jump in aperture - I'm quite happy with what the 3" can do, but similar performance at a lower cost & risk. Plus if I want more aperture, I can always just use the 8" dob I also have here, or borrow the 18" from the club house. But I suspect the TS will be just fine most of the time. 


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#52 CHASLX200

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Posted 17 November 2020 - 07:16 PM

I wish they were still made, but my 10" F6 is very good.

A good 10" F/6 is hard to beat. Once you get to a 12.5" old school Newt it is just too big to lift on the mount.  But a good old 12.5" F/8 is hard to beat if ya got the back for it.



#53 BillP

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Posted 18 November 2020 - 01:34 PM

I  was jumping between the C14 and my 102  as was Terry and we slowly upped the magnification ,,, C14 600x  , C102  300x and because I knew where to look on Jupiter when coming from the C14  , we could both see the same features , not as detailed for sure but there for the offering , cool and easily but I would say without a C14 at 600x only  20 metres away it would have been hard but it goes to show the detail is there but you just have to know exactly  where to look .

So in other words, simple getting some experience at honing your observation skill will do the trick. Agree!  waytogo.gif


Edited by BillP, 18 November 2020 - 01:35 PM.

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#54 Traveler

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Posted 18 November 2020 - 01:57 PM

Another option would be a 6 inch F8 Newton...

 

(and yes, i say this more often...cool.gif ) 


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#55 AndresEsteban

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Posted 18 November 2020 - 02:35 PM

Along the years I've learned that the best telescope is the one that's most used despite its aperture. Therefore, you must estabçish which one will be teh most used due to all the constraints you have: seeing, sky transparency, turbulence, your specific physical place of observation, that is: a house and a yard or an apartamant with our without balcony. Heavy light polluted skies or almost pristine night skies, your own budget, your own mobility and ability to carry weights (this is quite important, believe me!), and so on. It's not a matter of aperture, many things come first.

For multipurpose observations, a 4 inch f/11 ED refractor is, in my humble opinion, way better than a 5-in f/7.8. Color correction and other aberrations will be much better controlled in a f/11 than in a f/7.8 scope, that's for sure! Being an ED, an APo or s simple acro.

Also we must consider the not well appreciated Fried parameter: with a mean value of 100 mm for most places @ 500 nm. A 100 mm /11 scope fits nicely and you'll be gifted with an almost 365 day usable scope (unless cloud cover takes that night out)! As your aperture fever takes you up, you'll notice that the number of good nights you may use your big artillery goes down, so 100 mm aperure is a very sweet spot. Also you'll have little cooldown time, a nice aperture to pump 300x, f/11 ED will be very forgiving regarding eyepieces types as mentioned before.  

Also you must consider price. A 5-in f/7.8 for 1500 euros vs 4-in f/11 for 700 is not an option! Perhaps a 5-in f/13 ED for 1500 would tempt me but not a f/8. So yes, regarding all constraints I'd say you made an excellent choice going for this TS 4-in f/11 ED! Pay attention to the mount you'll use with it. The OTA weights about 5.3 kg considering a prism 90º diagonal (choose a good one) and a decent EP. So any 10 kg payload EQ mount will do. On the other hand, depending on your visual observation preferences, a heavy duty AZ mount  with slo-mo flexible controls is also an excellent chice for this scope!

So, congratulations and give us some feedback when you have this "litle" beauty fully tested!

Clear skies for us all!waytogo.gif 
Andy


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#56 Muffin Research

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Posted 18 November 2020 - 07:33 PM

So in other words, simple getting some experience at honing your observation skill will do the trick. Agree!  waytogo.gif

Indeed, often the act of observing gets overlooked.. what you can glean from that little ball of focused light is very much up to you.. it also takes time to recognise and train your brain. 

The person who's been quietly observing for the past half hour with one eyepiece looking at the object has good chance of seeing a whole lot more than the person who's been swapping out eyepieces in search for the best view.


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#57 Wildetelescope

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Posted 18 November 2020 - 09:53 PM

Seriously? Is that really a serious statement about being serious about something.  So need to go bigger to be serious?  Seems to be some seriously wrong logic there!  I am serious when I say that serious planetary observation not only can be done with 4" scope, but is done with a 4" scope! How do you know?  Easy, when the observer is serious about their viewing.  Of course there are some who need (i.e., crutch.gif ) larger apertures to be serious.  But seriously they have some serious issues.  But that's ok, we just pat them on the head and let them know, yes dear, you are being serious, while we go back to our 4" scopes lol.gif

When observing Saturn through my tv 102, I AM serious.  And don’t call me Shirley;-) 

Jmd 


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#58 Wildetelescope

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Posted 18 November 2020 - 09:59 PM

Yesss, I made a totally senseless decision and pulled the trigger for the 102mm F11 ED refractor at TS telescope  services. I am exited. I know that it is not a decision made with the head.... there are scopes around for the same or not substantially more money that will blow it away but hey, I like long refractors.  I see it as a little corona present.... working at home all the time, a man needs new toys now and then. lol.gif

smile.gif smile.gif smile.gif smile.gif

Liking long refractors is enough reason by itself.  Have fun!

 

jmd 


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#59 Echolight

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Posted 18 November 2020 - 11:13 PM

If I'm really serious about studying and seeing the most planetary details I bust out the equatorial tracking mount.
 

But I use a manual alt/az mount about 95% of the time. Maybe more.

 

I am getting closer to having the AVX be more grab and go though. Just got to build a wooden box with a handle to carry the lithium ion wheelchair battery and rig up a little wiring. So soon, very soon. I will be ready come next planet season!


Edited by Echolight, 18 November 2020 - 11:18 PM.


#60 Chuck2

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Posted 18 November 2020 - 11:36 PM

Michiel, congrats, your 4" APO will provide great views of the planets. I own a C90 Astro with very nice optics (obviously not equal to your Quester) but my 102 & 103 APOs easily outperform it on planetary observing. Brighter images, more contrast without central obstruction, sharp pin head stars, and +250x on good nights.  

 

During transparent, steady seeing, a 4" APO shows the Jovian moons crossing the face of Jupiter, just in front of an inky black transit shadow. Jupiter's creamy swirls, gray festoons, and white ovals spinning along with the great red spot (although mostly coral pink). The delicate equatorial and polar shading on Saturn with layered colors of the ring system split by the knife-edge Cassini division. The ever changing ice caps on Mars, the distinct shading of the Syrtis Major sloping volcano, or the mottled canyons of Valles Marineris. 

 

The Lunar surface is an entirely different world to explore, cruising amazing detail from 35x to 250x.

 

Is a 4" APO the best 'serious' scope for planetary work, probably not. But can a 4" APO provide sharp, contrasty, 'grab-n-go' enjoyment, YES!


Edited by Chuck2, 18 November 2020 - 11:40 PM.

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#61 Jeff B

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Posted 19 November 2020 - 10:03 AM

So the plentiful on the used markets 4" F9 FPL53 based ED doublets for around $450 USD are a safe bet to try out with minimal short term damage to the wallet.

 

A good sample of one of those will answer a lot of your questions directly.  If you get a good sample (and most seem to be good ones...at least mine is), it will give your Questar a hard time of it.

 

That being said, I really, really recommend, like others, a used SW120ED...really.  It is indeed bigger and heavier than the 100ED but that 20mm jump up in aperture is well worth it IMO.  The extra resolution and light grasp, screams out for bino-viewer use too.   The scope will work well with a Vixen SP class mount as long as you get a good tripod under it....which you need for any mount really.

 

Jeff

Attached Thumbnails

  • Scope A.jpg
  • 120ED with Moonlite 2.5 focuser B.jpg

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#62 Wildetelescope

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Posted 19 November 2020 - 12:00 PM

So the plentiful on the used markets 4" F9 FPL53 based ED doublets for around $450 USD are a safe bet to try out with minimal short term damage to the wallet.

 

A good sample of one of those will answer a lot of your questions directly.  If you get a good sample (and most seem to be good ones...at least mine is), it will give your Questar a hard time of it.

 

That being said, I really, really recommend, like others, a used SW120ED...really.  It is indeed bigger and heavier than the 100ED but that 20mm jump up in aperture is well worth it IMO.  The extra resolution and light grasp, screams out for bino-viewer use too.   The scope will work well with a Vixen SP class mount as long as you get a good tripod under it....which you need for any mount really.

 

Jeff

It has always been interesting to me how many REALLY  good and fussy amateur astronomers I know(many of whom do not post here) who all comment on how unusually good the Synta 120 mm ED scopes are.  These are folks who have $10K + scopes of all designs and are REALLY picky, who are at least grudgingly willing to admit that the views from that scope are really good.  I have that aperture range covered, but I have always been curious about picking one up.  To stay on topic, I think there is much fun to be had with a good F8-F9 100mm scope looking at solar system objects.  But if you wanted just a little bit more zip, the Skywatcher 120 mm ED seems like an excellent choice.  

 

JMD


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#63 Echolight

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Posted 19 November 2020 - 01:49 PM

Those 120's are double the price though.



#64 Jeff B

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Posted 19 November 2020 - 02:34 PM

Those 120's are double the price though.

Double of what though?

 

Compared to the new TS scope, the OP was looking at, a used SW 120ED is only about $200 to $300 USD higher, and you do get the larger aperture for the extra cash.  

 

It could also be easily sold for the purchase price, if not more if the buyer gets a good deal.

 

Jeff



#65 sg6

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Posted 19 November 2020 - 03:34 PM

4" is fine, my best Saturn view was a 4", about f/10 and an 8mm eyepiece.

Will struggle a bit on Mars and I suggest the easy option of just accepting what could be a poor Mars, or at least small Mars. You cannot have everything.

 

Get a dual speed focuser if possible, just easier to get the image sharp.



#66 Jon Isaacs

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Posted 19 November 2020 - 03:46 PM

Double of what though?

 

Compared to the new TS scope, the OP was looking at, a used SW 120ED is only about $200 to $300 USD higher, and you do get the larger aperture for the extra cash.  

 

It could also be easily sold for the purchase price, if not more if the buyer gets a good deal.

 

Jeff

 

I'm not seeing 120 mm Synta EDs on a regular basis for $200-$300 more than the 4 inch F/11. And the OP is in Europe where prices are typically higher.

 

There's always bigger scopes.. 

 

Jon


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#67 BillP

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Posted 19 November 2020 - 04:21 PM

Compared to the new TS scope, the OP was looking at, a used SW 120ED is only about $200 to $300 USD higher, and you do get the larger aperture for the extra cash. 

New on one vs used on the other is a bit of an apples-oranges compare.  To be fair needs to be new vs. new or used vs. used as whether a person wants ti unknowns involved with a used purchased or the security with a new purchase throws a whole new set of considerations into the mix.


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#68 Traveler

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Posted 20 November 2020 - 12:39 AM

Europe prices:

 

100ED: https://www.astrosho...rrector/p,53999

=1000 euro

 

120ED: https://www.astrosho...o-ota/p,15058  

=1600 euro

 

150ED: https://www.astrosho...-ed-ota/p,59364

=2100 euro

 

 

Why i mention the 150? Because these threads devolop always in bigger aperture answers then the OP is asking...cool.gif


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#69 BinoGuy

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Posted 20 November 2020 - 06:21 PM

This view of Jupiter is with the 4" Apo and binoviewing with 28 RKEs and Barlow.  Note that even with a 4" one can see structure inside the GRS.

 

Aren't those RKE 28s just fantastic in the binoviewer?  Just wonderful views.



#70 Craven

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Posted 20 November 2020 - 06:42 PM

After reading this thread, I'm wondering why I need a refractor, at all.  I want one, though, and I've been looking at the Astrotech refractors from 4" to 5.5"    If  I'm going to get better planetary views with my SCT and better deep sky views with a Dobsonian for 1/3rd the price, the only real reason to get a refractor, to me, would be for "grab and go" and even then it would be the 4" model.  Still, I want one and those Astrotech models seem so reasonably priced and the reviews are outstanding.  They have a 4" AT102EDiii for only $599.  That's crazy. 


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#71 Jeff B

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Posted 20 November 2020 - 06:55 PM

New on one vs used on the other is a bit of an apples-oranges compare.  To be fair needs to be new vs. new or used vs. used as whether a person wants ti unknowns involved with a used purchased or the security with a new purchase throws a whole new set of considerations into the mix.

In my experience not really Bill as I typically negotiate a return option for my used glass purchases.



#72 Astrojensen

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Posted 21 November 2020 - 04:13 AM

After reading this thread, I'm wondering why I need a refractor, at all.  I want one, though, and I've been looking at the Astrotech refractors from 4" to 5.5"    If  I'm going to get better planetary views with my SCT and better deep sky views with a Dobsonian for 1/3rd the price, the only real reason to get a refractor, to me, would be for "grab and go" and even then it would be the 4" model.  Still, I want one and those Astrotech models seem so reasonably priced and the reviews are outstanding.  They have a 4" AT102EDiii for only $599.  That's crazy. 

There's always a bigger, better scope, but there's also a lot to be said for a portable scope that's easy to set up, immediately ready for observation (IE no cooldown time to speak of) and still packs an optical punch. The key word here is comfort, because comfort means it'll actually get used, also on those so-so evenings, where conditions might be a bit iffy and you don't know when the clouds will turn up. I think the modern 4" ED refractor is a very solid player in this field. My personal favorite is the 4" f/11 ED. Not too small and not too large. Unless it's a particularly cold evening, it'll deliver sharp planetary views at 100x - 150x right from the start. My 6" f/8 Newtonian can outperform it, but only after having spent some time cooling down. The C8 I used to have, was even worse in this regard. The best thing about the 4" f/11 is that is has so much back focus, it's almost like an SCT. I don't have to think about having to use a special diagonal and barlow or glass path corrector to reach focus. I can just remove the tube extension and plunk in the binoviewer in the 2" diagonal, if I want a low or medium power view of the Moon. It's also extremely eyepiece friendly and even budget wide-fields are sharp almost to the edge. The longer focal length means that you don't have to resort to ultra short eyepieces to get to normal lunar-planetary magnifications. 

 

 

Clear skies!

Thomas, Denmark 


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#73 MikiSJ

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Posted 21 November 2020 - 04:46 AM

Remember, in 1609 Galileo Galilei used this to see Juptier, Saturn, Venus and a bunch of other stuff:

37mm plano objective                             GalileosTelescope.jpg


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#74 Muffin Research

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Posted 21 November 2020 - 05:05 AM

yes and he couldn't determine what the rings where.. however a modern designed and polished 4" sure you can


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#75 Jon Isaacs

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Posted 21 November 2020 - 05:36 AM

In my experience not really Bill as I typically negotiate a return option for my used glass purchases.

 

I buy nearly all my equipment used and that includes all the refractors I currently own as well as the my Dobs and binoculars.  There is an increased risk with buying used and the returning in 30 days just because I don't like the scope is not really an option.  You won't be buying anything from me. 

 

I can warranty that the scope as is described and will stand behind that but whether or not you like the scope, that's your deal.  I will find another buyer.  

 

But in this case, the issue is the fact that a 120mm ED costs more than $200-$300 more than a 100mm F/9 ED. I have seen Orion ED-100s for as low as $300, $500 is more realistic.  With 120EDs going for $1925 new, they are normally over $1200 used.  

 

I don't see comparing new 4 inch versus 120mm used.  If you are willing to buy used, compare them both used. 

 

Jon


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