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Size9Hex

ED frac... what size to go for?

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I've had fair amount of experience comparing my ED120 with 150mm refractors both recently with the ED150 testing and in the past with non-ED 150's that I've owned. The physical size and weight difference between the 120 and the 150 apertures is significant IMHO and, amongst other things, requires a commensurate step up in mounting capability (and cost !). My current viewpoint is that 120mm is a very good size for an ED refractor and if I was looking for a 150 or larger aperture scope now I'd probably look elsewhere than the refractor design. The 150 is on the right.

 

 

P1080684.JPG

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14 minutes ago, John said:

The 150 is on the right.

 

 

P1080684.JPG

😳😂👍

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3 hours ago, mikeDnight said:

There can be a big jump in performance from 4" to 5", but there isn't the same jump in performance from 5" to 6" as far as planetary is concerned. To get a truly meaningful jump in performance over a 5" refractor you'll likely need to be looking at 7" +.

I made the mistake a few years ago of selling my 5" Tak to buy a 6", but the bigger refractor didn't show me anymore than the smaller 5". What happened in my case was that I had to buy a much heftier mount, ( the eq6 in the attached photo was nowhere near good enough to carry the 6" Tak). My Losmandy GM8 was equally incapable of carrying the 6", so I had to buy a G11. The consequence being that I used the 6" far less as it was more hassle, and I found myself looking for excuses why not to observe.

An ED in the 4" to 5" range can be a wonderful lunar and planetary scope, that will give some incredibly sharp, contrasty views. The relative lack of resolution in these smaller refractors, is in my view, more than compensated for by the high definition they give, often leaving much bigger telescopes standing. Their portability and ease of use is another major benefit. These scopes don't generally need hefty mounts and they cool rapidly (15 mins for a doublet) on most nights, so you may find yourself doing a lot more observing, as short sessions are so rewarding.

Several of my associates who are very keen lunar and planetary observers use 4" ED apo's as their main work horse, as they seem to be relatively unaffected by seeing, and they are easy and comfortable to use.

The SW 120ED, either the DS Pro version or the Eqinox version, is in my view one of the best refractors currently available. There is minimal CA but it is certainly not objectionable, and can only be seen around the brightest objects. There is probably more CA introduced into a system by some wide angle eyepieces than by the excellent objective lens. I've owned three 120ED's and all were consistantly good. (I would certainly not worry about going for Takahashi or any other high end brand if I were on a budget. There's hardly a hairs breadth between the SW ED's and the high end refractors in planetary performance)! 

All the refractors below are superb lunar and planetary scopes. All cool rapidly and deliver breathtakingly razor sharp views, but choosing one that is easily carried out and back in again can greatly enhance your observing enjoyment.

Thank you Mike. Terrific reply and very helpful towards the decision.

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2 hours ago, cloudsweeper said:

Funny how things develop!  I too was planning on an ED120 to replace the Startravel - but the ST is OK (not the best optics or focuser) and gives nice wide views, so I've decided to hang on to it and go smaller with an ED80 Apo.  I shall use it (amongst other things) as a guide for the wider ap  8" SCT without the GoTo mount.

And when I want even more ap, I can haul the Dob out.

Best of all worlds!

Doug.

Funnily enough, I taken a similar route. My first frac was an ST102 (which I’m going to sell if I upgrade as per this thread), then dropped down to a 72mm ED which I felt was more versatile (especially under suburban skies) if less powerful. Like the sound of your set up.

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2 hours ago, GavStar said:

I have had a different experience to Mike. 

I have 100mm, 130mm and 160mm APO refractors. For me the 160mm is a noticeable jump over the 130mm and very significant jump over the 100mm. Examples objects are plato’s Craterlets and the trapezium (which should really called the hexagon in the 160mm 😀).

In terms of portability and mounting requirements the 100mm is definitely easier and can be mounted on a light mount such as the az gti. I find the 130mm needs a much sturdier mount which also works very well with 160mm. Part of this is due to the relatively fast f7 ratio  that the 160mm has which results in a shortish tube (100mm) and hence short moment arm.

I’m much less experienced than Mike so I think I’m less able to tease out fine detail in smaller scopes. I need all the help I can get!! I’ve generally found the 160mm not to be much affected by seeing either.

 

Thanks Gav, it’s nice to hear a view that’s a bit more pro big scope (not to suggest any right or wrong views on it). If I may ask, what would you pick if you could only have one in the 130/160mm space?

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1 hour ago, John said:

I've had fair amount of experience comparing my ED120 with 150mm refractors both recently with the ED150 testing and in the past with non-ED 150's that I've owned. The physical size and weight difference between the 120 and the 150 apertures is significant IMHO and, amongst other things, requires a commensurate step up in mounting capability (and cost !). My current viewpoint is that 120mm is a very good size for an ED refractor and if I was looking for a 150 or larger aperture scope now I'd probably look elsewhere than the refractor design. The 150 is on the right.

Thanks John. That’s really helpful. Seeing those two scopes side by side is quite telling, as is your comment about looking for a different design. All replies so far have been super helpful and I can start to see which way I’m leaning. The 150mm in your photo, well, if it was dual mounted with my 72mm pointed up at zenith, one eyepiece would be on the ground and the other up in the sky! Borderline whether I could reach any slow-no controls on the mount too! 😮

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5 hours ago, Peter Drew said:

For double stars, lunar and planetary viewing as a main requirement, a 150mm Maksutov would be worth considering. Easier to handle, cheaper by far and nearer to being an APO than any ED refractor. It would fit nicely between your 72ED and the 10" Dob.    😀

I've had several versions of the 120ED and sveral 150mm Maksutovs.  Though I don't disagree with the quailites of the Mak for the these purposes, I would still go for the 120ED any time.  The main reasons being (not particularly in any order), cool down time, shorter focal length of the refractor and contrast which I feel is better in the refractor.  As well as viewing planets( and the Moon) at higher powers, I also like low power wider field views of them when they are near other planets/deep sky objects or the Moon, and a small Saturn in rich field of stars is fabulous.  Also, though a Mak in theory has less colour, I find a planet on axis in the 120ED is effectively colour free and more contrasty.   The Mak is of course shorter than a 120ED, but easier to handle, I don't find this so but it's up to the individual.  

In the end, I suppose I find the 120ED a more versatile instrument with little difference in actual higher power  planetary/lunar detail between the two scopes.  In the end of course, as ever there's not a wrong choice, it's down to the individual.  A nice choice to have to make, a winner either way :smile:

 

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2 hours ago, Size9Hex said:

Thanks Gav, it’s nice to hear a view that’s a bit more pro big scope (not to suggest any right or wrong views on it). If I may ask, what would you pick if you could only have one in the 130/160mm space?

Well I’m trying to thin my scope collection down a bit at the moment so this is a live decision I’m making currently. 

I think the 130 may be the scope that goes.

But a key reason is the 160mm being a quite fast f7 so it’s not too bulky in comparison to my other scopes as shown below...

 

D7A8C541-3DF9-48C6-A240-6877617B51FD.jpeg

F1FAFC50-5CF9-48A8-9F58-C43B14FA3D15.jpeg

Edited by GavStar
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Thanks @GavStar. I may need to show that photo to the boss. “At least I’m not asking for this many!” 😀

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I couldn't possibly cope with this many fine refractors.  I'd spend so much time working out which of the excellent optics I was going to use, it would always cloud over before I was up and running :smile:.

 

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3 hours ago, GavStar said:

Well I’m trying to thin my scope collection down a bit at the moment so this is a live decision I’m making currently. 

I think the 130 may be the scope that goes.

But a key reason is the 160mm being a quite fast f7 so it’s not too bulky in comparison to my other scopes as shown below...

 

D7A8C541-3DF9-48C6-A240-6877617B51FD.jpeg

F1FAFC50-5CF9-48A8-9F58-C43B14FA3D15.jpeg

That's a really beautiful line-up Gavin!  I really like the feathertouch on your Tak FC, it looks really quite beautiful. Can you remember who supplied it and what size adapter you needed?

I'm of a similar mind to Paul in that I'd struggle to choose between them. However, I'd be happy to offer the charitable service of giving a home to your AP130 if need be. :icon_biggrin:

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46 minutes ago, mikeDnight said:

That's a really beautiful line-up Gavin!  I really like the feathertouch on your Tak FC, it looks really quite beautiful. Can you remember who supplied it and what size adapter you needed?

I'm of a similar mind to Paul in that I'd struggle to choose between them. However, I'd be happy to offer the charitable service of giving a home to your AP130 if need be. :icon_biggrin:

Mike,

I got it from FLO as per the attached link (although the price has increased a fair bit!!)

https://www.firstlightoptics.com/starlight-instruments-feather-touch-2inch-crayford-focusers/2-crayford-focuser-for-takahashi-fs60-and-fc76.html

You need to ask FLO to get a slightly different adapter as follows (although Stu uses the fc76 adapter fine on his fc100dc but it has a different look)

http://starlightinstruments.com/store/index.php?route=product/product&path=38_60&product_id=405

Edited by GavStar
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3 hours ago, GavStar said:

Mike,

I got it from FLO as per the attached link (although the price has increased a fair bit!!)

https://www.firstlightoptics.com/starlight-instruments-feather-touch-2inch-crayford-focusers/2-crayford-focuser-for-takahashi-fs60-and-fc76.html

You need to ask FLO to get a slightly different adapter as follows (although Stu uses the fc76 adapter fine on his fc100dc but it has a different look)

http://starlightinstruments.com/store/index.php?route=product/product&path=38_60&product_id=405

another tip: get an additional 2" Riser so you don't need an extension tube for your focuser.

e.g. http://starlightinstruments.com/store/index.php?route=product/product&path=44_64&product_id=137 or http://starlightinstruments.com/store/index.php?route=product/product&path=44_64&product_id=138

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I'm of a similar mind, having a 72ED and 127Mak already.  I'm intrigued by a 120mm or 125mm refractor.  If you had to choose between the Skywatcher EVOSTAR ED120 Pro and the TS-Optics PhotoLine 125mm f/7.8, what would you choose?  They're about the same price, so no difference there.  What about differences in focuser, lens cell, and other build qualities?  What about quality of figure and color correction since both use FPL-53 glass?  The TS-Optics is apparently binoviewer friendly where the EVOSTAR isn't.  The TS-Optics is 7.57 kg and 975mm whereas the EVOSTAR is only 5.2kg and 900mm, which would be a major weight savings and slight length savings.  I have a DSV-2B mount and wonder if it would work with either of these scopes.  It's plenty capable of handling the 72ED and 127Mak side by side, but what happens when all that weight is on one side and has a longer moment arm than either of those two?  Could anyone visually perceive the difference between 120mm and 125mm?  Any thoughts on this would be greatly appreciated.

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23 minutes ago, Louis D said:

I'm of a similar mind, having a 72ED and 127Mak already.  I'm intrigued by a 120mm or 125mm refractor.  If you had to choose between the Skywatcher EVOSTAR ED120 Pro and the TS-Optics PhotoLine 125mm f/7.8, what would you choose?  They're about the same price, so no difference there.  What about differences in focuser, lens cell, and other build qualities?  What about quality of figure and color correction since both use FPL-53 glass?  The TS-Optics is apparently binoviewer friendly where the EVOSTAR isn't.  The TS-Optics is 7.57 kg and 975mm whereas the EVOSTAR is only 5.2kg and 900mm, which would be a major weight savings and slight length savings.  I have a DSV-2B mount and wonder if it would work with either of these scopes.  It's plenty capable of handling the 72ED and 127Mak side by side, but what happens when all that weight is on one side and has a longer moment arm than either of those two?  Could anyone visually perceive the difference between 120mm and 125mm?  Any thoughts on this would be greatly appreciated.

I seriously doubt anyone could tell the difference due to aperture, and the SW 120ED is a known quantity to me. However, the TS-Optics scope looks stunning and has some very appealing features the SW DS Pro doesn't have. I thing I'd be tempted by the TS scope at such a great price, even though optically, I doubt there'll be much difference.

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I’d spotted what looks like an equivalent scope from Altair but wasn’t aware of the TS version. Looks awesome with some nice features, so interested in Louis’ question too. Low power binoviewing of nebulae especially looks a really nice feature. Much easier to see low contrast differences with two eyes than one.

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2 hours ago, Size9Hex said:

I’d spotted what looks like an equivalent scope from Altair but wasn’t aware of the TS version. Looks awesome with some nice features, so interested in Louis’ question too. Low power binoviewing of nebulae especially looks a really nice feature. Much easier to see low contrast differences with two eyes than one.

Stellarview has a version as well.  I'm not sure why it costs so much more, though.

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Personally scope portability and fast setup are pretty high on my list as I don't have a permanent observatory. My current main scopes are an APM 107 for practicing with imaging and WO Megrez 90 for short session visual (with the weather in this country, a long period of clear seeing is hard to come by). I've also got a SW 200PX dob for when I need some more aperture (not used often). For luna and planetary I just use my Delos 4.5 and 6mm along with a powermate 2.5x as I prefer shorter OTAs for easier handling. I'm aware the quality of view would be less than a slower long tube frac, but I'm ok with it.

If you're just like me, then my recommendation would be between 4" - 5" (e.g. SW 120ED). Otherwise a 6" would give you a very significant boost in performance compared to your 72ED (e.g. SW 150ED or APM 152).

Edited by KP82
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I am by far the least experienced here, but followed a very similar thought train to yours.
My list of scopes amounts to an Equinox 80ED, 127 Mak, 10" Dob, and my personnel favourite/dream scope at this time an Equinox 120ED.

My Orion xt10i was my first scope. Having the smaller 80 and of purely personnel taste, I always knew I wanted a larger frac. I just really like them. I was very lucky to pick the 120 up secondhand here. It was bought complete with a 2" steel leg CG5 tripod, a 16" extension tube and an Ercole Giro. Whilst this set up comfortably copes with the 120 with no counter balancing, in fact we have had a friends 8" Newt in dual mount without problems, this set-up in real-world situation is actually slower to set-up than the Dob in terms of back-of-car to viewing. I love everything about owning that 120, the views, it's operation, even how it looks. If I had to choose between the Dob and frac, i would keep the frac (but i understand that may not be the majority choice). The Ercole Giro is a joy, but the combined weight of this set-up is greater than the Dob, and not really any easier to manhandle. 
I also have the very slightly lighter, smaller 1.75" legged, steel tripod with an AZ5 mount. Despite it apparently being rated at 9 or so Kg on this type of tripod (5kg on the Skywatcher Star Adventure and one assumes similar photo tripods) the experience is very different. There is considerably more vibration. Don't get me wrong, at a push it's OK, but the heavier mount and tripod is so much better.  The 120, with a 2" diagonal, Hyperion zoom and an Orion RACI finder comes in at around 7.5kg.
I also have an AZ GTI, and wouldnt even consider mounting the larger frac on it.
For whatever its worth, I'm not sure a 120 is grab-and-go. As an OTA it's not hard or heavy to handle, but you do limit it as i guess you do with all scopes by under-mounting it. It's a lot of money and scope for "limitations". The AZ5 and GTI are great with the smaller frac and Mak.
 

Edited by steveex2003
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7 hours ago, steveex2003 said:


For whatever its worth, I'm not sure a 120 is grab-and-go. As an OTA it's not hard or heavy to handle, but you do limit it as i guess you do with all scopes by under-mounting it. It's a lot of money and scope for "limitations". The AZ5 and GTI are great with the smaller frac and Mak.
 

Really useful post. Thank you. 👍

I’m not picturing a 120mm as grab and go in my house either. The 72mm on AZ5 just about ok to take out in a single trip. It’s a nice set up for observing, but for carrying, it’s an awkward top heavy shape, and not much clearance passing through doors. Wouldn’t fancy a 120mm as a single trip in my house, which was part of what got me thinking that a 150mm might not be much more hassle for set up (albeit heavier, pricier, etc) - the OTA and mount still being separate trips. That said I’m leaning towards a 120mm after all the replies here.

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I find that I use the ED120 on an alt-az mount a lot for outreach / society evenings and UK trips. It all goes in the boot of the car easily plus once set up I can move the mount/scope combination around easily from spot to spot to get the best views.

My 130mm F/9 triplet is the same weight and size as a 150mm F/8 ED refractor and it's just not as easy and straightforward to use. The cool down time is a bit longer and it needs a heavier mount. I can just about pick the bigger refractor / mount combo up and move it around a small distance but I have to be much more careful and it requires noticeably more effort and care.

It's a personal thing but for me, at my time of life, the ED120 is much closer to "grab and go" than an ED150 F/8 would be. If I was 20 years younger maybe the differences would not be as obvious.

 

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For whatever it’s worth, and I would bow to pretty much anyone elses opinion over mine, I came across a fabulous lightweight AltAz mount, that I got for an absolute steal at £50 on Ebay. The Giro GR 2 Mini. A scaled down Ercole, it’s about 20% lighter than the AZ5, but a third of the physical size, if that. It sits quite happily on a Manfrotto 055 and copes with Equinox 80, 1.25 diagonal and a Baader zoom well enough that I don’t feel the need to throw any more money in that direction.

When last at FLO just before Xmas Martin mentioned they may carry the Giro range. In my limited experience, their simplicity and engineering quality would have me rebuy without hesitation.

Edited by steveex2003
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24 minutes ago, steveex2003 said:

For whatever it’s worth, and I would bow to pretty much anyone elses opinion over mine, I came across a fabulous lightweight AltAz mount, that I got for an absolute steal at £50 on Ebay. The Giro GR 2 Mini. A scaled down Ercole, it’s about 20% lighter than the AZ5, but a third of the physical size, if that. It sits quite happily on a Manfrotto 055 and copes with Equinox 80, 1.25 diagonal and a Baader zoom well enough that I don’t feel the need to throw any more money in that direction.

When last at FLO just before Xmas Martin mentioned they may carry the Giro range. In my limited experience, their simplicity and engineering quality would have me rebuy without hesitation.

I saw that one and thought it would be a very good buy for someone. I have enjoyed giro style mounts for a long time now, and agree with what you say. I currently have a Giro-WR, similar to the Mini Giro and when properly balanced it is amazingly capable.

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That all said, there is an ad for an older Celestion CR6 on ABS right now that I keep staring at for £250

if in good order, that’s a lot of scope for quality eyepiece money.

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