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...il.php?sid=364

Maybe someone has one and can comment with some authority.

Cheers,
Bruce

[MortonH]

Originally Posted by Kunama

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

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

[MortonH]

Originally Posted by 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...il.php?sid=364

Maybe someone has one and can comment with some authority.

Cheers,
Bruce

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 (Steve)]

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 (Bob)]

Originally Posted by MortonH

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. Cheers.

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 (Jennifer)]

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
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]

Originally Posted by 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
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.

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

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

[glend (Glen)]

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]

Originally Posted by Allan

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

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

[MortonH]

Originally Posted by 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.

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 (Rob)]

Originally Posted by 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.

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

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

[Kunama]

My preference is new Vixen - ED103S at AstroShop http://www.myastroshop.com.au/produc...p?id=MAS-046B2

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

[MortonH]

Originally Posted by Kunama

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

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.