WO zenithstar 103 vs Skywatcher Esprit 100

[gasdoc]

Hi all,

I have a WO Z61 which I love but I want more reach. Have just got an EQ6R Mount which I’m learning to use and the next step is probably a 100mm refractor (strictly AP only).

Obviously the Esprit has excellent reviews everywhere and is a triplet but am I likely to notice £500 difference compared to the WO z103 doublet + reducer/flattener?

 

Alternative: buy a dedicated Cooled Astro cam for my z61 and get some reach that way whilst entering that rabbit hole - OSC vs mono etc etc (Currently using FF and cropped dslrs)?

 

 Cheers

 

 Paul

 

[johninderby]

You should add the new StellaMira 104 sold by FLO. Should have the edge over the Esprit optically. Same build quality as WO.

Edited April 13, 2020 by johninderby

[Chris]

AP will exaggerate chromatic aberration, so if you're reasonably discerning maybe go for the Esprit out of the two mentioned. If you had said a mixture of AP and visual I would have steered you towards the WO 103 as it will cool a little quicker, it's cheaper, and for visual the CA won't be as noticeable, but for pure AP go with a triplet. 

[gasdoc]

1 hour ago, johninderby said:

You should add the new StellaMira 104 sold by FLO. Should have the edge over the Esprit optically. Same build quality as WO.

Thanks John, looks like a beautiful scope but for that money I think I'd get the Esprit 120......hmmm, now there's another option to consider!

@Lockie I'm not sure I'm discerning enough to notice the CA - and surely I can edit this out with photoshop?

 

Thanks for the opinions though! I'm sure I'll be very happy with either - just want to know whether the price gap is justified in real world images.

 

[Dr Strange]

The keys to the Espirt are a) the glass. It is Schott and FPL-53. b) the figure and mating. They do it really well c) the accessories. I don't know of any other product where everything you need in order to view or image except for the EP or camera are included with the scope. So that £500 will shrink when you add up everything else you would have to buy.

I don't know what the mating element is on the WO but I do know the quality of glass Schott makes and that is hard to beat. The Esprits have been compared to Tak's and AP's for AP with very favorable results. As in the AP's and Tak's were slightly better but not a wide margin better. So value for the price in terms of optics and mechanicals is there with the Esprit's. 

[johninderby]

18 minutes ago, gasdoc said:

Thanks John, looks like a beautiful scope but for that money I think I'd get the Esprit 120......hmmm, now there's another option to consider!

@Lockie I'm not sure I'm discerning enough to notice the CA - and surely I can edit this out with photoshop?

 

Thanks for the opinions though! I'm sure I'll be very happy with either - just want to know whether the price gap is justified in real world images.

 

I call it Scope Creep. Thare is always something a bit better for a bit more money and can be easy to blow your budget. Problem is there is too much choice nowadays. 😁😁😁

Edited April 13, 2020 by johninderby

[Dr Strange]

The 100 is almost a full f/stop faster than the 120 but the 120 would resolve more detail as well as fainter objects/parts of objects due to its larger aperture. Depending on your targets and the sensor you end up with and/or use now a fast 100mm scope may not be the best scope for you. At 840mm focal length vs 550mm the 120 is always going to win in this respect. Throw a small, sensitive sensor in the mix and it should be interesting, but a longer focal length instrument still will likely do better.

There's also size and weight to consider but the EQ6 will handle both scopes without a problem. I had the 100 and it was a porky little beastie which was surprising. It was as beefy if not more so than my present TV NP101is. 

 

Edited April 13, 2020 by Dr Strange

[gasdoc]

Yes I'm getting myself confused on what's going to give me the best imaging possible for the money:

103 WO + cooled astrocam  eg WO Z103 + zwo ASI 183 (gives a CCD suitability of 0.9 which seems ok?)

120 FL esprit plus my Nikon D7000 (I also have a D750).

 

My intended targets are nebulas and galaxies - I realise galaxies are at the edge of these sorts of refractors' focal lengths, but I was hoping a smaller sensor astrocam would make this feasible.

 

Obviously I can get the Esprit 120 and stick with the Nikon for now, and save up for a dedicated camera at a later stage.

 

Only thing I've realised lately is that skimping on decent bits of kit ultimately ends in frustration and after succumbing to purchase, results in a "why didn't I do this earlier!!"

 

 

[old_eyes]

A couple of years back I had the pleasure of working with @ollypenrice at Les Granges on galaxy imaging with a TEC 140 and an Atik 460 mono. The results were superb, and I have always thought that if I wanted to get serious about galaxies, that is how I would do it. It would avoid having multiple scopes and the hassle of swapping them.

So yes; refractor plus small pixel camera works.

[ollypenrice]

14 hours ago, gasdoc said:

 

 but I was hoping a smaller sensor astrocam would make this feasible.

Careful, the sensor size has precisely no effect whatever on on what you're calling your 'reach.'  Some of this confusion comes from the horrible term 'crop factor' used in daytime photography. This term encourages the mistaken belief that there is some equivalence between focal length and chip size. In astrophotography no such equivalence exists. The proper term for 'reach' is image scale or pixel scale, measure in arcseconds per pixel. It is controlled by just two variables, pixel size and focal length. Not chip size.

14 hours ago, Dr Strange said:

The 100 is almost a full f/stop faster than the 120 ...

 

More care needed. In daytime photography a lower F stop is faster because it has more aperture. A 120 has more aperture than a 100...  This topic is contentious and has been done to death on here (partly my fault!!! 🤣) but a quick search on the fatal term 'F ratio myth' will reveal all, even though it may leave you none the wiser.

14 hours ago, gasdoc said:

 

My intended targets are nebulas and galaxies - I realise galaxies are at the edge of these sorts of refractors' focal lengths, but I was hoping a smaller sensor astrocam would make this feasible.

Unfortunately this is rather like saying, I want to buy a sauce mix which works for fish and cakes.  Nebulae and galaxies are very different. Galaxies, apart from M101, M33 and M31, are small (and packed with tiny details requiring high resolution.) Nebulae tend to be large, diffuse and lacking in fine detail. Finding a scope-camera that will do both is not easy. The nearest you can get is to use a moderate focal length (approaching a metre) and a camera which has both small pixels and a large chip. This is always going to be expensive. Old Eyes, above, mentioned our TEC140. This can do a good job of nebulae and galaxies if we vary the camera. Here are two examples, the first with a large format, low res, large pixel Atik 11000 and the second with a small format, small pixel Atik 460. There are now cameras with both large format and small pixels using CMOS technology, however.

Olly

 

[Singlin]

Great explanation and demonstration

[gasdoc]

2 hours ago, ollypenrice said:

Unfortunately this is rather like saying, I want to buy a sauce mix which works for fish and cakes.

😂😂😂 Yes I am resigned to that fact. Your images are beautiful - I’ve seen your stuff before and it’s always impressive but I have to be more realistic with what I can hope to achieve with a budget of £2500 and bortle 5 skies.

 

sounds like I need to consider the esprit 120 to get the FL and complement my WO 61 and sticking with my dslrs (crop and full frame) for now then going for a smaller pixel astrocam - any suggestions? Zwo 183? (2.4 um pixels) - slightly under sampled but gives a similar FOV to your tec 140 plus atik 460?

[ollypenrice]

Probably better to be slightly undersampled than over. (Mainly because it's faster.) An EQ6 working well under guiding can deliver an RMS of about half an arcsecond. The generally accepted rule of thumb is that this will support imaging at about twice that, so an arcsecond per pixel. Note that it is very common for the seeing not to allow this, unfortunately.  I'm not up to date with all the possible cameras and haven't used a CMOS, so others will need to advise on that. It's certainly true that the arrival of small pixel cameras has opened up the galaxies to refractors. (I did an article on this for Astronomy Now a while back.) BTW I think there's a calculator for pixel scale on FLO's website.

Olly

[gasdoc]

Yep I’ve been using that but as you correctly assumed in your previous post, I’m coming from a dslr photography background and trying to get to grips with the whole pixel scale thing - the ccd suitability calculator tool is useful however for a guide.

 

Many thanks for taking the time to explain the concepts though!

 

Paul

[gorann]

I would seriously consider this one that TS has on sale now:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p6679_TS-Optics-PHOTOLINE-130-mm-f-7-FPL-53-Triplet-APO-Refraktor.html

Slightly bigger and much cheaper that the Esprit 120, and I do not know why. It got my attention after seeing what Pete on Astrobin have accomplished with it:

https://www.astrobin.com/users/pete_xl/

Edited April 14, 2020 by gorann

[ollypenrice]

11 hours ago, gorann said:

I would seriously consider this one that TS has on sale now:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p6679_TS-Optics-PHOTOLINE-130-mm-f-7-FPL-53-Triplet-APO-Refraktor.html

Slightly bigger and much cheaper that the Esprit 120, and I do not know why. It got my attention after seeing what Pete on Astrobin have accomplished with it:

https://www.astrobin.com/users/pete_xl/

Gosh, I hadn't seen Pete's images on Astrobin but they are quite superb with the TS instrument.

Olly