Which 4" ED/APO for visual?

[MortonH]

This has probably been done to death before, certainly over on Cloudy Nights, but I thought I'd ask here for a local "flavour".

The basic premise is that I miss the SV110ED I sold a few months ago. It was a well-made f/7 ED doublet with FPL-51 glass. False colour was controlled very well and was easy to ignore for visual observing. I was very happy with its planetary performance in particular. It was almost exclusively used at home on a balcony.

I have an excellent C6 SCT that I now use most of the time at home. On deep sky it shows more than the SV110, which was one of the main reasons for selling the SV110. However, for star clusters and double stars the C6 lacks the contrast of a refractor (no surprise there) and is more affected by poor seeing, which is common in summer.

So I'm thinking of another refractor in the 4" range and am looking for suggestions to make sure I consider all the options. An obvious choice would be a Skywatcher 100ED but I'm not convinced about the mechanics of the standard models. The SV110ED had CNC rings, retractable dew shield and a sturdy 2.5" R&P focuser.

At the other end of the scale I've seen a few classic Taks like the FS-102 go for around $2500 here but that's a bit more than I want to spend. Budget is more like $2000 maximum. Looking at used scopes to maximise buying power.

Any thoughts based on criteria below?


Visual only
Decent quality 2" focuser (not the cr@ppy Crayford that's standard in a lot of scopes)
Aperture around 100mm
Sliding dew shield preferable


Thoughts or comments welcome.

Cheers.

[Kunama]

Try a "Wanted" advert for a Vixen FL102S, probably the best visual scope of decent build quality in that price range.

[BC]

I'm not sure whether the Skywatcher Equinox 100 is available in Australia, or indeed how it compares with other scopes. It is more expensive than the normal Skywatcher 100ED. I have the Equinox 80 and it is a really beautiful piece of equipment with an excellent dual speed focuser. There's no hint of needing to replace it with a better focuser (as seems common with the 80 ED).

http://ca.skywatcher.com/_english/01_products/02_detail.php?sid=364

Maybe someone has one and can comment with some authority.

Cheers,
Bruce

[MortonH]

Interesting option, although I'm a bit reluctant to buy something of that age in case there are problems waiting to surface.

[MortonH]

The was an Orion Eon 120 that sold here recently, and an Equinox 80, but they don't seem to be all that common.

[Allan]

G'day Morton. Any chance you could buy your SV110ED back, seeing as you liked it so much?

Those SW ED100's are great value, and I thought the ones I've looked through had pretty good optics. Mechanically not as good, but you could always throw on a Feather Touch or Moonlite focuser.

But hey, you're talking 4" Taks, and it doesn't get much better than that. Although I decided on an NP101is for maximum field of view observing, and I wouldn't sell that for any other 4" telescope. I'm not sure how much they are second hand. But astronomy doesn't get much better than a NP101, 31 Nagler and really dark skies.

A TSA 102 or FC 100DF would be my pick of the 4" Tak scopes. There's a guy on CN's who churns scopes like dirty socks and he said the FS series was quite variable in optical quality. Doesn't mean that you wouldn't end up with a fantastic example of one though.

[Tinderboxsky]

You could consider the Vixen ED103S. I have one and the differences between it and the highly regarded FL102 are at the margins. They are very well made, have a silky smooth R&P focuser, are relatively lite for their size, but do note have a retracting dew shield. It is removable but you would need a separate lens cap. A job for Meru here on IIS.
I found mine through a wanted add here on IIS about three years ago. It's colour correction is outstanding, produces a perfect star test and renders pin sharp high contrast images. Second hand would be well within your budget. I don't see any need to go to triplets for visual - a well corrected doublet will perform to most people's visual acuity.

Cheers

Steve

[Tropo-Bob]

I am always amazing by the low price of the Skywatcher 100ED. It is barely more expensive than the 80ED and much less than the 120ED. Am I missing something? Is the build quality in the class of the other 2 mentioned scopes.

I have a Vixen 115SS and it is a great scope. I would also recommend the 103S.

[jenchris]

I have a skywatcher clone (saxon ed100) whether or not it is my eyes, I can't see any ca and it doesn't show in the images I've taken.

True the focuser is a little naf, though you could easily fit a moonlite or something on it without breaking the bank.

[MortonH]

I've read that Synta scopes have very good colour correction but less contrast than more expensive scopes. I would assume my SV110ED was optically of similar quality to Synta although I never compared them.

Certainly there are plenty of upgrade options for Synta focusers so that's not a deal breaker.

[MattT]

ED 100 is a great scope...had two of the things and could not see much CA at all,in either, though it was there. The standard focuser isn't that good.

For an alternative I replaced them with a 90mm f11 Achro from the mid 90's. A bit more, and I mean a bit more CA but I'm happy :thumbsup:
Cost all of $125, many thanks to Lars for the sale....a great small scope for Planets and G+G.

My recommendation is a 4" f15/3.5" Achro or an ED 100.

[MortonH]

I wouldn't go over 900mm in focal length without compromising the stability of my mount, so no f/15 for me! :lol:

I wonder if the dual-speed focuser on the current Synta scopes is better than the old one. :question:

[glend]

What about the Explore Scientific 102mm ED APO Triplet, f7, 714mm focal length. I have the 80mm version and it is a very nice scope. Currently on sale in the US for $1099 USD.
It's not a TAK but It's solid, well built, and the optics seem very good - well at least my 80mm does.

[MortonH]

I might look into that if I don't find a satisfactory alternative.

[MortonH]

On paper that's an option but the ES scopes have never appealed to me for some reason. I also prefer a doublet for contrast, cooldown and less chance of collimation issues.

[GrampianStars]

There's a Saxon 100ED on this site here
http://www.iceinspace.com.au/forum/showthread.php?t=139796

New Saxon 100ED at AstroShop http://www.myastroshop.com.au/products/details.asp?id=MAS-045I2
Or new Vixen - A105M f/9.5 at AstroShop http://www.myastroshop.com.au/products/details.asp?id=MAS-046A3
My preference is new Vixen - ED103S at AstroShop http://www.myastroshop.com.au/products/details.asp?id=MAS-046B2 :thumbsup:

[Kunama]

I spent some time looking through one of these and almost bought one, really surprised me how well it compared to my Tak.

[MortonH]

Interesting. I've seen a few similar comments about them being close to Tak optically.

MyAstroShop describes the lens as a "2 group 3-element ED optical design". Does it really have three elements? Other websites say it's a doublet.

Or did it perhaps have three elements in a previous incarnation?

Anyone know?

[Don Pensack]

If you get a doublet, prepare to get f/10 to f/12 at a minimum to control color. A triplet can be made faster with the same color correction.
I have an ES 102ED Triplet and the images are fantastic IN FOCUS. To test out-of-focus images, I use a #56 green filter because different colors defocus at different rates.
Intra- and extra-focal images are nearly identical.
I couldn't guarantee the one you get will be as good, but I'm keeping mine:
--dual speed 2" R&P focuser
--focuser suitable for visual and AP
--sliding dew shield
--push-pull collimatable cell
--good rings with carry handle connector
--standard Synta-style finder bracket shoe so many finders fit.
--comes standard with a 2" dielectric star diagonal with 2" to 1.25" adapter which is threaded for filters.

[MortonH]

Hi Don.

f/10 to f/12? For an achromat, yes. I'm talking ED or fluorite doublets where f/7 to f/9 is fine for visual.

[Merlin66]

For visual, there's nothing to beat the ol' Genesis 4" f5.
This has been with me for almost thirty years - other scopes have come and gone, but the Genesis is a 110% keeper.
In fact, I've already measured up my "box" and when I go - it goes with me.......

[jenchris]

I'm gonna use mine to light my pyre....

[Don Pensack]

Morton,
Depends how much CA you'll tolerate. For a standard doublet 4", f/12 is about the minimum, and I could see CA in my f/15 4" doublet.
ED glass helps, for sure, but I still wouldn't go below f/9, personally.
Obviously, if usage is primarily lower powers, then your f/7 to f/9 range is OK. And there are a plethora of minus violet filters available for specific scopes and targets.
I just rarely meet someone using a scope like this who is not into viewing the Moon and planets.
Given the prices on decent Asian-made triplet refractors these days, there isn't really much reason to stick to doublets unless weight is an issue (doublets are considerably lighter). I'm seeing the triplet edging out the ED doublet in terms of sales since so many triplets are out there now from several companies. Also because ES is selling the 102ED triplet for $1099.99 in the States right now. Is it more than $1800AUD for you guys?

[MortonH]

I found the CA in the SV110ED tolerable on planets. Wouldn't mind a bit less CA though, hence the thought of something with a higher spec this time.

Haven't seen many ES scopes here. There's one dealer who lists them but after hearing about some issues with their stock (of ES scopes) I'm not really interested.

Any thoughts on the Vixen ED103S?

[Larryp]

Spring the extra money for a Tak FC-100DF. You definitely won't regret it.

[Don Pensack]

I have limited experience with the Vixen f/7.7 103S-ED refractor.
The one I looked through (can't remember the brand of diagonal) was only so-so optically. I cannot say whether the owner had bothered to collimate or not, and a lot of refractors come out of the box uncollimated.
I've seen a whole bunch of these in the field over time, but all had cameras attached and weren't being used visually.
I think I agree with Larryp.

[jenchris]

I suppose the proof of the pudding is only there in an image.
Picked at random from a row taken last moon.
I'm presuming the focus was reasonable - it's a single image.
No filtering and no adjustment at all.
Just had a look, focus isn't perfect, it's actually better with a better sky too -
It's a DSLR image @ about 1/250 sec throught the Saxon F9 100ED

[casstony]

Just bide your time and see what comes up in the classifieds. Apart from Tak and Vixen, WO has been putting out very nice optics in recent years and they finally have a good quality R&P focuser. I'm not so keen on ES due to sample variability.

[MortonH]

I agree with Larry as well, except the financial controller WOULD make me regret it! :lol:

[MortonH]

Good advice, although biding my time isn't something I do well when it comes to astro gear. There's always the danger that some other expense uses up the money first.

[MortonH]

Since I have an affinity with Stellarvue scopes I've put a wanted ad for one. There have been a few of their triplets sold here as well as the ED doublets so you never know. My dream scope used to be a Stardust Blue SV4...

[johngwheeler]

I found the ES 80 triplet that I bought from AEC to be rather disappointing, and exchanged it a Tak FC100 DF. Admittedly, it must have an ex-demo or something that had been knocking around for a few years and so had some annoying mechanical defects & missing parts, but even allowing for this, I found the field curvature to be bothersome.

I may have been expecting too much from an 80mm f/6 Apo. It was very good on terrestrial objects and would be great birding scope, but I wanted sharper stars from a refractor. Maybe it was just a duff example!

I don't have any experience with StellarVue, but they seem to sit nicely in the price/quality curve.

I would also have a look at the Orion Eon line (Bintel have them).

Cheers,

John

[Wavytone]

Hi Morton,

I'm fairly sure Stellavue, Orion and others were assembling scopes using ED doublets in the 80-130mm range from a chinese factory mass-producing these, possibly Kunming Optical. The only question IMHO was whether all received lenses at random, or whether some (e.g. StellaVue) were paying more to cherrypick the best ones off the production line.

In any case its a pity you didn't ask when I was selling my Orion ED105 f/7 last year, optically it was as good as one could expect for an ED at that focal ratio. At high power it gave a nice Airy disk with a hint of colour inside/outside focus. Field curvature did exist - not bothersome visually, but for imaging you could nail that with a flattener, a few to choose from. You'd have to go to a triplet or alternatively an ED doublet at about f/10 to do significantly better at the same aperture.

[MortonH]

A belated update to this thread. Having briefly been the owner of a Tak FS-102 that I couldn't really afford, I've managed to buy back my old SV110ED.

First re-light expected tonight as the forecast looks good for the weekend.

Here she is awaiting darkness with my recently acquired vintage C8.

[FlashDrive]

:thumbsup:

[Kunama]

How did 'First again' light go Morton? I am taking the TOA out tonight to try out some birthday oculars.....

I may head to Medlow Bath next weekend with both scopes.....

[brian nordstrom]

:thumbsup: By far the best quality 4 inch class APO ( yes I class these as APO,s) is the Skywatcher 100mm ED f9 these are amazing using FPL53 for little money .

1/4 the price of a Tak but 95% of the views , a no-brainer if on a budget like most of us .

Just google Synta 100mm ED f9 reviews there are 1000,s of happy customers world wide.

Brian.

[MortonH]

First light didn't really happen last night. I did take the scope out on the balcony but it was windy and the seeing was awful. Mars and Saturn were just jumping around so I canned it. Tonight is looking much more promising.

[MortonH]

I agree. I spent a few weeks debating whether to buy my old SV or a 100ED but in the end I wanted the superior mechanics and larger aperture of the Stellarvue.

[MortonH]

Bintel now has an EOFY sale on - the Black Diamond ED100 is only $1,000 :eyepop:

That night have tempted me a bit more! :lol:

[glend]

I would be tempted at that price. I see Andrews has responded with their pricing.

[MortonH]

Both shops now selling the ED100 for less than the ED80.

[MortonH]

Been out for the last hour or so with the SV110ED looking at Mars & Saturn.

Contrast is good, not as good as a Tak, obviously, but acceptable. A bit of CA that comes and goes with the seeing. When it settles there's a subtle purple glow around only the brightest objects - for example a little on Mars, none on Saturn - but this isn't objectionable to me.

I love having a good focuser again. That was the weak point of the FS-102. The Stellarvue dual-speed R&P is a pleasure to use.

Pretty happy to have the scope back. Some day I'll go Tak again, but for now this will do nicely.

[skysurfer]

Congrats !

I have the same ED110 from 'Kunming' and have the same experiences. Slight (almost negligible) purple halo around Jupiter, but none around Mars and Saturn.
I use this one as a travel scope as it fits within in the carry-on requirements of the airlines when I remove the focuser.

For me it is for both visual and photo (Canon 6d) use.

[Wavytone]

http://www.astromart.com/classifieds/details.asp?classified_id=922073

[brian nordstrom]

;) Take some beating ,,, both ways .. visual and AP .

Great to see these are getting finally ( Lewis ) appreciated , amongst the best ever made . ( Takitis )

( its strehl is better than the atmosphere we live in for clarity )

Brian.

[5ash]

I have a 120ed I use for astrophotography and have no problem with CA though it must be there though very slight. As for the focuser , I find it robust enough to hold more than 1 kg of camera with no sag or change in focus. I would think the focuser on the BD 100ed would be a similar 10 :1 focuser. However some of the other clones like Saxon have single speed focusers.
Philip

[MortonH]

I think all current Synta versions have a dual-speed focuser now.

There's nothing 'wrong' with the Synta focuser but like any piece of kit, once you've used something better it can be hard to go back. I have the dual-speed on the Saxon Newtonian I bought last year and it's good enough but not as solid or smooth as the focuser on my Stellarvue, which in turn isn't as good as a FeatherTouch, etc.