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4 inch all rounder refractor / grab'n'go scope, couple of contenders


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I plan to replace my ST102 F/5 with a decent all rounder for visual at some point (not so near future, but hopefully by the end of this year).

This is my list of "requirements / wishes":

- close to apo (ED) / apo performance, good optical quality, CA minimal to non existent for visual. ED doublet preferred to triplet due to price, weight and cool down reasons.

- 4" class (can go bigger, would not go smaller, so 100mm+)

- relatively light weight up to 5kg for ota, it will be mounted on AZ4 (can hold up to 6.8kg)

- Ok focuser, does not need to be anything special, good 2" crayford with fine focus will do.

- Capable up to x250 power on planets (with right eyepieces, plan to use TV N-zoom 3-6mm, 7mm TV delite for planetary role, would like to avoid barlow/powermate combos if possible) giving good sharp views

- Capable of up to 3 deg TFOV with right eyepiece (something in the ES 34/86 or ES 30/82 class eyepiece for that, depending on actual scope) - would like to fit most of M31 in the view, also other wide field targets

- High bang for the buck is a + of course.

- Shortish tube - it will be sort of travel / grab'n'go scope, but it does not need to be "airline travel" size, it needs to fit in medium car boot with room to spare.

Now, from all of the above, first / best option that comes into consideration is SW Evostar 100 ED, and so far it has been my first and only choice. But I recently stumbled onto this:

http://www.teleskop-express.de/shop/product_info.php/info/p9868_TS-Optics-PhotoLine-102mm-f-7-FPL-53-Doublet-Apo-with-2-5--Focuser.html

And that got me thinking which one of these two would be a better choice?

Compared to Evostar, TS 102 F/7 brings to the table:

- better focuser (I have TS80 Apo which I use for astrophoto, but would like to replace for visual with something more capable, it has the same 2.5" focuser and it is a good one).

- Shorter focal length - easier to go wide field, while still been able to go to x200+ power with mentioned planetary eyepieces

- I think that fit & finish will be overall better (don't have experience with evostar, only what I've read online, but C&C tube rings on my TS80, and retractable dew shield are rather good).

- overall shorter length - easier for transport.

- I might even use it for astro photography if it proves capable in that regard.

On the other side, there are couple of things that put it behind of evostar:

- heavier - 4.5kg vs 3.7kg (not sure if this is a real negative thing, mount will be able to carry it, it is not much heavier to carry around).

- more expensive (200e - that is about the amount of money for a decent 2" wide eyepiece)

- Being F/7 doublet, there is real concern that CA won't be handled as good as in evostar, although TS on their website state that it is color free (FPL53 + lanthanum element) and they even market this scope in their photoline brand - intended for astro photography.

- Unknown optical performance compared to tried and tested evostar. I do think it should be rather good scope optically (TS80 really is), but there simply are no reviews confirming this - at least I did not manage to find any. How well will it behave on planets?

 

A penny for your thoughts ...

 

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May I be the first to help you spend your money? :icon_biggrin:. Tough one to call on paper, if the TS one is as good as they claim then I would go for that one to best suit your purposes/ The extra that the TS costs could soon be swallowed up by replacing the focuser on the Evostar if it proved necessary.

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Amongst my weaponry (Python - Spanish Inquisiton ?) I have an excellent Vixen ED102SS refractor that has an ED doublet lens that uses an FPL-51 (probably - Vixen didn't specify) ED element.

It's a really good all round instrument which can deliver low power views up to 3.8 true degrees in extent as well as handling magnifications of 220x when the seeing is good. While it's not totally colour free in the way that my Tak 100 F/9 Fluorite is, the Vixen's control of CA is far, far better than any Evostar achromat refractor that I've used, even the F/10 ones.

If the TS 102 F/7 can get that sort of performance it would make a good all round scope :icon_biggrin:

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2 hours ago, Peter Drew said:

May I be the first to help you spend your money? :icon_biggrin:. Tough one to call on paper, if the TS one is as good as they claim then I would go for that one to best suit your purposes/ The extra that the TS costs could soon be swallowed up by replacing the focuser on the Evostar if it proved necessary.

Yes, it's a tough one, isn't it? Out of listed "down sides", only one that actually makes any real impact is CA handling / optical quality, and no info on that apart what is written on TS website. I was hoping that someone would come along and offer their firsthand experience, but I realize now it's a slim chance, because it is relatively new product (have not seen it before listed, and I do scan items on their website from time to time), it certainly differs from already existing TS ED 102 F/7 with FPL-51 element and 2" dual speed crayford focuser (that one is same optics as Starwave 102 ED, possibly Lunt 102 ED)

2 minutes ago, John said:

Amongst my weaponry (Python - Spanish Inquisiton ?) I have an excellent Vixen ED102SS refractor that has an ED doublet lens that uses an FPL-51 (probably - Vixen didn't specify) ED element.

It's a really good all round instrument which can deliver low power views up to 3.8 true degrees in extent as well as handling magnifications of 220x when the seeing is good. While it's not totally colour free in the way that my Tak 100 F/9 Fluorite is, the Vixen's control of CA is far, far better than any Evostar achromat refractor that I've used, even the F/10 ones.

If the TS 102 F/7 can get that sort of performance it would make a good all round scope :icon_biggrin:

I might not have been clear on that but achromatic refractors are not considered as contenders for this one, I was thinking of Skywatcher EVOSTAR ED100 Pro - F/9 ED doublet with FPL-53, and not achromat doublet one - at F/10. By all accounts ED version is virtually color free and excellent performer. There is, as I already mentioned, FPL-51 F/7 scope from several vendors, but from what I've read in terms of reviews on internet, it looks like it is easily beaten by ED100 pro on color correction and planetary performance.

I think that TS102 F/7 with FPL-53 should be ahead of any fairly good 4" F/7 with FPL-51, but that is solely based on my previous experience with TS80 apo (which is truly apo, and I've tested it to Strehl 0.98 in red, 0.94 in green and 0.8 in blue using Roddier test and OSC camera - probably not the best way to conduct such testing since I've used single focus position and real star subject to not the best seeing possible, and my Roddier skills are dubious at best, but I got assurances that any testing error would give worse results rather than falsely present better optical quality). The question is of course, is my assumption correct, and if this glass indeed has required optical quality to compete with ED100 PRO.

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Sorry - I forget that the ED PRO series refractors from Skywatcher are also part of the Evostar range.

My Vixen ED102SS matches the Skywatcher ED100 F/9 that I owned before it for CA and SA correction. I'm not sure that all scopes of a similar spec would do that though - Vixen make very good objective lenses.

The ED100 Skywatchers are very close to Takahashi scopes of a similar spec. The TS 102 F/7 might get close but without trying one I don't know whether it would match the Skywatcher ED100 F/9 :dontknow:

It's not just about the ED glass element of course but the figuring, coating, mounting of the objective and the match of the glass of the 2nd element that creates the overall performance.

 

Edited by John
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1 hour ago, John said:

Sorry - I forget that the ED PRO series refractors from Skywatcher are also part of the Evostar range.

My Vixen ED102SS matches the Skywatcher ED100 F/9 that I owned before it for CA and SA correction. I'm not sure that all scopes of a similar spec would do that though - Vixen make very good objective lenses.

The ED100 Skywatchers are very close to Takahashi scopes of a similar spec. The TS 102 F/7 might get close but without trying one I don't know whether it would match the Skywatcher ED100 F/9 :dontknow:

It's not just about the ED glass element of course but the figuring, coating, mounting of the objective and the match of the glass of the 2nd element that creates the overall performance.

 

No worries, I also had to double check if it really is branded Evostar. :D

I'm not hung up on whole FPL-51 vs FPL-53 (or FCD-1 / 100 for that matter :D ) thing, I just reckon that it is easier to properly figure lens of higher F/ratio (since we are discussing doublets here) by using glass with best index / characteristics (that being FPL-53, flourite would probably fare better, but I suspect price would match that). I simply do not know enough on topic to even know if ED100 level of correction (or very close to it) is possible in F/7 design using FPL-53 / lanthanum combination.

 

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Vixen ED103s F7.7 doublet, made in Japan.

Best ED doublet I ever used, bar none (and I've owned 3 ED100 F9s). Vega visually just a pure white, tight point of light.. Dazzling.

Expensive new but used occasionally available used. Mine cost me c £750 used in mint condition, but the new price is double that ( still cheaper than a Tak FC100 though!). I still miss it now even though I have a Tak FS128.

The Vixen showed me Sirius and the Pup, the Trap M42 E & F stars and also widefield views eg all of the Pleiades framed nicely in one view.

The newer scopes like mine have a very nice dual speed R&P focuser.

I can't think of anything negative apart from rarity and being hard to find, and recommend it without hesitation. Vixen scopes are very underrated IMHO.

Dave

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I'm looking at getting a 4" portable refractor myself soon and to me a shorter focal ratio is important because I wan't the widest possible field of view. If I'm traveling to a super dark site, it will be to look at things like the North America Nebula and Andromeda galaxy which are very big indeed! A 4" f5.5 will give me 4.6° with a 31 Nagler vs 3.6° from an f7. So for me the Skywatcher Esprit 100 ED is looking like a good option, though it's not particularly cheap. I guess the fact that it would be faster if I did want to dabble with photography is an additional bonus. Though there'd definitely much more choice in the f7s

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I have a Stellarvue 90mm APO triplet CF f7 for a 630mm fl. This scope punches above its weight and with the 42mm LVW, 30mm ES gives great views of the NAN etc. Speaking of weight it is around 8 lbs.

I believe that TS sold these same scopes and if their 102mm APO triplet is anything like my 90mm it is well worth the consideration.

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  • 8 months later...
On 6/29/2017 at 15:18, vlaiv said:

I plan to replace my ST102 F/5 with a decent all rounder for visual at some point (not so near future, but hopefully by the end of this year).

Hi Vlaiv.  I have similar requirements and wonder if you ever bought the TS photoline 102 F7 doublet or a different scope?  That and the 80mm F7, 565FL doublet version (currently reduced to 548 euros) are on my shortlist. Thanks.

Edited by SpaceBass
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1 hour ago, SpaceBass said:

Hi Vlaiv.  I have similar requirements and wonder if you ever bought the TS photoline 102 F7 doublet or a different scope?  That and the 80mm F7, 565FL doublet version (currently reduced to 548 euros) are on my shortlist. Thanks.

Hi, no not yet. Did not get much chance to observe this winter, weather was bad so purchase is postponed until further notice :D

TS photoline 102 F/7 is still main candidate for me, I have 80mm F/6 apo triplet (also photoline) but I use that only for imaging. For visual I wanted something with a bit more light grasp and a bit more FL.

I'll probably do sort of review with testing when I purchase scope, so you will get the chance to see my impressions, unless of course, you make your purchase first.

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14 hours ago, vlaiv said:

Hi, no not yet. Did not get much chance to observe this winter, weather was bad so purchase is postponed until further notice :D

TS photoline 102 F/7 is still main candidate for me, I have 80mm F/6 apo triplet (also photoline) but I use that only for imaging. For visual I wanted something with a bit more light grasp and a bit more FL.

I'll probably do sort of review with testing when I purchase scope, so you will get the chance to see my impressions, unless of course, you make your purchase first.

But that is why winter is best used for planning and purchasing. :)

You are welcome to have a look through my new 100mm acquisition to see whether you like the 100mm/f7ish combo. 

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2 hours ago, BGazing said:

But that is why winter is best used for planning and purchasing. :)

You are welcome to have a look through my new 100mm acquisition to see whether you like the 100mm/f7ish combo. 

Well it looks like I'm going to have a chance at taking a peek thru your new FC 100 DF (I guess that is new scope? :D ) if you are planning to come to Messier Marathon on 14th/15th?

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32 minutes ago, vlaiv said:

Well it looks like I'm going to have a chance at taking a peek thru your new FC 100 DF (I guess that is new scope? :D ) if you are planning to come to Messier Marathon on 14th/15th?

Weather permitting we were thinking of going to Debelo brdo on those dates, the sky is much better than Letenka (where I assume MM is taking place).

In any case, we are close enough, planets are getting higher every evening, so yes, you are very welcome. DF it is...

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Guys, I'm pondering about whether to get a star test at time of ordering from Teleskop-Express, which is 60 euros for both Star and Ronchi (or 30 euros each). They guarantee a diffraction limited optical system, Strehl 0.8 or better. I have very limited ability to do any testing of my own, other than a basic star de-focus. 

Is there much merit to paying extra for this?

 

Edited by SpaceBass
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1 hour ago, SpaceBass said:

Guys, I'm pondering about whether to get a star test at time of ordering from Teleskop-Express, which is 60 euros for both Star and Ronchi (or 30 euros each). They guarantee a diffraction limited optical system, Strehl 0.8 or better. I have very limited ability to do any testing of my own, other than a basic star de-focus. 

Is there much merit to paying extra for this?

 

Can't really tell if it is worth it. I do my own testing - Roddier analysis, and so far I've been happy with quality of my optics. I have 8" dob, which showed 0.8 or greater system strehl (so primary is probably quite better than 0.8). It is mass produced Skywatcher variety. Quite happy with the scope. I also did test on RC8" from teleskop express. It is 0.94 or better system strehl. Again really pleased with scope. TS Optics Photoline 80mm F/6 apo shown 0.8 or greater in blue part of spectrum, 0.94 or greater in green and 0.98 in red part of spectrum.

With today's technology and manufacturing process, I think that it is very unlikely that you will end up with a bad sample. So I'm fairly confident when purchasing scopes at this time that I'll get quite usable instrument (for that sort of money). I will be able to tell if scope is below usable optical quality and if it should be returned.

In my view it is worth ordering additional tests as a means of insurance that you don't need to return scope and don't even want to consider such possibility.

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Can I throw a left field option in? I’m writing this on a family holiday in La Palma where I’ve bought a 6” Skywatcher mak in my hand luggage (with eps and ASI camera) while my AZ goto and tripod went in the checked luggage. 

This gives fantastic optics on a tracking mount. Not so good for wide field of view but great for visual deep sky and moon+planets. 

Cost wise was made more palatable by buying both the mount and tube second hand. 

I hope that is of use!

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  • 3 weeks later...

Just an update ...

After a bit more research (I'm itching to pull the trigger, but cash flow has stalled somewhat, so it's not an easy decision, and there is justification for fifth scope to be made ... :D ),

it turns out that both TS 125mm and TS 102mm have better color correction with respect to SW counter parts - 100ED and 120ED, at least according to two sources:

For 102 (Stellarvue Access 102 seems to be exactly the same scope rebranded, even focuser is the same, so Kunming Optical / Sky Rover):

https://www.cloudynights.com/topic/578894-stellarvue-access-102-first-impressions/

And for 125 (in french):

https://www.webastro.net/forums/topic/161648-lunettes-ts-photoline-12578-ed-ou-1027/

Unfortunately, no data on sharpness is available (except quote of Strehl 0.979 on one item).

 

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125 is much bigger and heavier than a 4 inch frac of comparable focal length, it will be around (or more than) 9 kgs with diagonal, finder, dovetail and ep. AZ 4 cannot handle it...I suppose you included it in the discussion just for the sake of comparing quality?

 

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10 minutes ago, BGazing said:

125 is much bigger and heavier than a 4 inch frac of comparable focal length, it will be around (or more than) 9 kgs with diagonal, finder, dovetail and ep. AZ 4 cannot handle it...I suppose you included it in the discussion just for the sake of comparing quality?

 

Yes, well, given that I suspect them sharing design and optical glass elements, and also there has been another thread on 125mm questioning quality of that scope - for that reason I view them as siblings - somewhat like SW 100ED, and SW120ED. Reviews of both seem to be quite scarce.

I've also considered getting 125mm, but like you said it is in different category, both weight and focal length. Aiming for all-rounder, 975mm focal length is not quite suited for widefield, though I have no doubt it would be better scope for planets and DSOs.

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Is the Astro-Tech scopes available where you live ? This is affine scope within your requirements : https://www.astronomics.com/astro-tech-at102ed-4-f7-ed-refractor-ota_p20548.aspx

Other than that the SV102 Access would be great : 

http://www.stellarvue.com/stellarvue-sv102-access-f-7-super-ed-apo-refractor-telescope/

I don't know Vic that's owner of Stellarvue  but I do know he holds high standards for all his scopes and all are top quality . I also know he grinds all of his own glass to perfection and none goes on the market without approval and no defects . Long time ago I bought his AT1010 80mm called the tank . STill have it and love it ! 

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  • 2 years later...
2 minutes ago, Luminated said:

@vlaiv read this via a google search; so just catching up :) Which one did you go for in the end?

Still not got scope from this thread, but it is still on my list.

At the moment I've got two 4" scopes - Skywatcher 4" F/10 Evostar achromat and SW Maksutov 102mm.

I'm rather happy with Mak, it sits really nicely on AzGti mount and is sort of my grab'n'go lunar scope, but due to commitments and weather - has not seen much use (I did manage to do some observing and imaging with it this year).

On the other hand, I planned to do a lot with Evostar 102/1000 achromat, but it's seen even less use than Mak.

At the moment, plan is to play around with F/10 achromat in various roles:

- various observing roles

- white light solar

- DSO imaging scope

- lunar / planetary imaging scope

- spectroscopy scope

- possibly Ha solar (that is also on hold for the moment due to involved spending)

I want to put it thru its paces as general purpose scope and see the max that I can get it to deliver in each role. It will require some spending (that I would otherwise do anyway) - like Skytee II mount, AZ4 is simply not fit to carry such a long tube (I'm not happy with vibration dampening time) and of course Solar Ha filter (quark combo).

Thing is - I'm sort of in the middle of building a new house and I expect to be moving in spring. Spending is therefore severely limited and I'll have access to much darker skies once I relocate (obsy is also being built) - so everything is sort of on hold.

In any case - I ended up not getting 4" ED apo and it still might be some time before I get to that - two contenders at the moment - both 4" F/7 TS photoline versions, one cheaper with FPL51 glass and more expensive one with FPL53 glass. First option is in case I just decide to have it as general purpose all round visual scope and keep Mak102 for grab'n'go planetary. Second option will be if I decide to just have one scope to cover multiple roles.

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