18 replies to this topic

[Rince]

Hi Guys,

 

I would like to ask for help deciding which scope I should buy. To better understand my situation and what exactly is that I am looking for, I thought I would provide a little background information:

 

In a nutshell, I would like to buy a refractor telescope mostly for wide field deep sky astrophotography. However, somewhat counter-intuitively, I would like said scope to be small and portable. The reason for this is that the mount I plan to buy for my new scope will be a star tracker (a Sky-Watcher Star Adventurer Pro to be exact) with a maximum payload capacity of 5 kgs (although I would like to be below that limit just to be safe).

 

Now, most of you will say, "but the mount is the most important part, why so small?" and believe me, I understand. However, as much as I would like one, a larger equatorial mount is just not an option at the moment. I live in a tiny apartment in the middle of the city; so, going out to image always involves a car ride and dragging all my equipment back and forth from the third floor (with no elevator). Therefore, portability and ease of use is not only a convenience for me but more often than not is the deciding factor whether or not I can go out to image at all. But, while the sky tracker is not ideal, I believe that with practice and a little patience (and very precise polar alignment), I can capture satisfying images. My camera of choice is a Nikon D5600 DSLR with a weight of 0.47 kg.

 

Based on the above criteria, I have narrowed down my choices to the three scopes below (all wide field which is more forgiving of tracking errors) and would like to ask for your expert opinions to help me pick the one that you think would serve me the best. Keep in mind, however, that I am not well versed in different scope manufacturers; so, if you know of a refractor that is not on my list but you believe would serve me well, please let me know. I am open to suggestions! Anyway, here are the scopes I believe would be a good fit for me:

 

 

William Optics ZenithStar 61 APO

https://www.firstlig...wo_zs61_rd.html
According to reviews, the Z61 has first-class design and build quality with its FPL53 glass. The imaging train is all screwed in and the added Bahtinov mask is a very nice bonus. Furthermore, with a weight of just 1.45 kg (plus 0.27 for the dedicated field flattener) it is light enough for the mount to easily handle (with my DSLR, the whole payload would be around 2.5 kilos, half of the mount's capacity). However, I am a little bit afraid of the 61mm aperture, that it may be a bit too small for astrophotography. Also, at f5.9, it is not the quickest of scopes.
The whole package with the flattener and T-ring would cost me: 710 Euros (including shipping), which is a little pricey for this size but, if I am correct, it would more than make up for it in quality.

 

 

TS Optics Photoline 60/360

https://www.astrosho...red-ota/p,56055
This is actually not a contender, I just thought it was funny that it is the exact same scope as the ZenithStar 61, minus the Bahtinov mask. It costs about the same too; although, its field flattener looks considerably more flimsy. I guess a lot of scopes do come from the same place...

 

 

Sky-Watcher Evostar 72ED PRO

https://www.firstlig...ds-pro-ota.html
With 1.96 kilos, this scope is a little bigger than the Z61, but I do like the larger aperture. And with its dedicated x.85 reducer/flattener, the scope will have the same wide field of view as the Z61 but with a better f4.9 speed. Sound pretty good, but I have watched/read a few reviews of this scope, and honestly, it looks to have considerably lesser build quality than the William Optics ones. The imaging train is pressure mounted, for example, and the fact that the company is not disclosing the glass it is using for the optics is more than worrisome. It also seems to have some plastic parts which is never a good sign.
With the field flattener and T-ring, it would cost me 580 Euros (including shipping), which is considerably cheaper than the other two (however, if I also buy a Bahtinov mask and try to replace the imaging train with an all-screwed in option, it would probably run me closer to the Z61's price).

 

 

William Optics ZenithStar 73 APO

https://www.firstlig...-73-ii-apo.html
My last contender has all the pros and cons of the Z61 but with a larger aperture and focal length, which I believe makes it better suited for astrophotography (although its field of view is slightly smaller). This, however, comes with a price, both literally and figuratively. With 2.83 kgs, this scope is the largest of the three, placing my payload right at the edge of what I would be comfortable putting on the mount (2.83 + 0.32 + 0.47 = 3,62 kilos), which would make this purchase a little risky for me (although I have read testimonial of people using this scope with my mount of choice, and they haven't reported any problems). It also cost a lot more than the other two.
With the field flattener and T-ring, it would run me 891 Euros (with shipping).

 

 

Do you have any experience imaging with these scope? Which one would you recommend. I am curious to read your thoughts. Thanks!

Edited by Rince, 06 December 2019 - 03:56 AM.

[sg6]

The WO ZS 61 would be the obvious one - not sure if the TS is the same or slightly different.

The ZS 73 is starting to get a bit big/heavy and you will need a flattener for it either immediatly or soon after, equally that is the same for the ZS61. The adjustable flatteners are $200 unsure about € cost, guess €180 (?)

 

Both are f/5.9 which makes me slightly prefer the ZS61, however I doubt you would see any difference with the extra 12mm in regards spherical aberrations.

 

The mian difference will be the overall field, both are wide the ZS61 being wider. So if "wide" is the only/main/primary reason again ZS61, but if you want to pick out something specific then the ZS73 is just a little better. Will be a case of is the target "lost" in the image.

 

As above in terms of weight the ZS61 wins.

 

Really the ZS61 seems to come out on top, my one concern is the oddity of could it be too wide?

In photography you have to realise that the eye is selective, a camera (DSLR) is not. You look at a tree, you see the tree as a "highlighted! object, a camera doesn't. If you want a camera to see the tree you stick a 200mm lens on not a 30mm lens.

 

Buy the flattener at the same time as the scope, WO have a habit of having none in say 6 weeks time then you are a bit stuck.

[DLuders]

I recommend getting the fourth one on your list (  https://www.firstlig...-73-ii-apo.html ).  The  William Optics 2019 Zenithstar 73 II APO has very high quality and the largest aperture of the four.  The 73mm-diameter lens captures 48% MORE light than a 60mm lens; more light makes for faster exposures.    

 

[(73/2)² x pi] / [(60/2)² x pi] = 1332.25 / 900 = 1.48

[happylimpet]

You might want to think about(at some point) using a low-read noise CMOS camera (like the ZWO offerings) as they will allow shorter subs less prone to guiding errors. I realise this may not be an option straight away.

 

Good luck! Sure you'll get some great stuff regardless of your choice. The important thing is to get out there and get imaging.

[james7ca]

I recommend getting the fourth one on your list (  https://www.firstlig...-73-ii-apo.html ).  The  William Optics 2019 Zenithstar 73 II APO has very high quality and the largest aperture of the four.  The 73mm-diameter lens captures 48% MORE light than a 60mm lens; more light makes for faster exposures.  

 

[(73/2)² x pi] / [(60/2)² x pi] = 1332.25 / 900 = 1.48

Yes, a larger aperture gathers more light but given any particular camera it's the f-ratio that determines the "speed" of capture for extended objects.

 

As for the OP's list, I'd go for the smallest and lightest system since that will work best with the Star Adventurer Pro. In fact, I'd probably recommend sticking with a fixed focal length camera lens or even something like the WO SpaceCat 51. You really don't need a lot of aperture for most wide-field targets.

[Rince]

Yes, a larger aperture gathers more light but given any particular camera it's the f-ratio that determines the "speed" of capture for extended objects.

 

As for the OP's list, I'd go for the smallest and lightest system since that will work best with the Star Adventurer Pro. In fact, I'd probably recommend sticking with a fixed focal length camera lens or even something like the WO SpaceCat 51. You really don't need a lot of aperture for most wide-field targets.

James,

 

The SpaceCat was on my list at some point (I really liked its compact size and that I would not need to buy a dedicated field flattener). However, I eventually decided to drop it, my main reasons being: 1) with only 51mm aperture, I was just afraid it is too small for AP, and 2) its field of view was a bit too wide for my taste. I am shooting for a FoV where large DSOs (like Andromeda or Orion) would nicely fill my view with just a little wiggle room for framing.

 

 

However, regarding the first point, I would be the first to admit that I am not sure I understand a 100% how aperture works on refractors. I would assume the larger the aperture is, the more light gathering power the scope has (this is mainly why I lean towards larger scopes), but I get confused when different sized scopes have the same f number.

Edited by Rince, 06 December 2019 - 07:38 AM.

[Starkid2u]

The fourth one. Your weight limit is not in jeopardy and it's aperture, aperture, aperture. Nothing trumps that. Good luck.

 

Brian

[PirateMike]

Good luck! Sure you'll get some great stuff regardless of your choice. The important thing is to get out there and get imaging.

I think you are heading in the right direction to be successful in AP when picking a small scope and a small mount to start out.. You should be able to get plenty of wonderful images with whatever scope you pick.

 

The main thing is to buy the equipment, get out there and image and practice, practice, practice.

 

A setup like you suggest should be able to keep you busy for a few years at least and will never become "obsolete". Good luck!

 

 

 

Miguel   8-)

 

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[Rince]

It seems that William Optics scopes are recommended overwhelmingly (which I expected, as they have an almost legendary reputation), but I was kind of hoping that someone would share his/her experiences with the Sky-Watcher scopes as that also seems very popular.

[astroseyer]

It seems that William Optics scopes are recommended overwhelmingly (which I expected, as they have an almost legendary reputation), but I was kind of hoping that someone would share his/her experiences with the Sky-Watcher scopes as that also seems very popular.

 

You can’t beat the quality and portability of Skywatcher Esprit ED APO Triplets - plus they already come with a rock solid carrying case and field flattener.

Edited by ASTROSEYER, 06 December 2019 - 04:03 PM.

[Rince]

You can’t beat the quality and portability of Skywatcher Esprit ED APO Triplets - plus they already come with a rock solid carrying case and field flattener.

They might be good quality, but even the smallest one is too heavy for my mount, not to mention that it is a little bit out of my price range. Also, I haven’t seen any mention that they come packed with a field flattener. On most sites it is an extra expanse like with most other scopes.

[james7ca]

...However, regarding the first point, I would be the first to admit that I am not sure I understand a 100% how aperture works on refractors. I would assume the larger the aperture is, the more light gathering power the scope has (this is mainly why I lean towards larger scopes), but I get confused when different sized scopes have the same f number.

Aperture can give you image scale and offers the potential for greater resolution, but for extended objects it's really f-ratio that determines how quickly you can capture an object. That said, you can also get image scale by using a camera with smaller pixels but pixel size works something like f-ratio ("speed" goes roughly by the square of the pixel size) and thus smaller pixels tend to be less "fast."

 

In terms of scale, one thing to consider is that DSOs and the night sky in general have an almost unlimited potential for detail regardless of your field of view or the aperture of your telescope. The only real limits are imposed by your horizon (can't go wider than that) and the fact that our turbulent atmosphere (i.e. the seeing) makes apertures beyond about 8" less and less useful. In the former I'm talking about how wide you can really go and in the latter I'm talking about the limits in resolution or detail that can be recorded by your capture system. Professional astronomers get around some of the limits imposed on aperture by the seeing conditions by using adaptive optics or by launching telescopes into space, but those options aren't available to us amateurs.

 

I'm not suggesting that larger apertures don't have any advantages, since a properly configured and skillfully used large scope can produce amazing image. But, so can a properly configured and skillfully used 51mm aperture scope.

 

That said, I'd agree that the SpaceCat 51 could be considered a bit too wide for some targets as framed by a DSLR, but that can be said of almost any focal length (wouldn't the same be true for even an SCT when imaging a small planetary nebula?). And, of course, you can always crop your images (within reason) as there is no law that says you need to use every square millimeter of the sensor.

 

Frankly, I think weight is your main concern and that's why I'd go with a very light scope. In terms of limits imposed by aperture and focal length, it's not that hard to find acceptable images that have been taken with apertures as small as 10mm.

 

Final word, it's your decision and whatever you decide to do will probably work out fine. Almost any scope or camera can be used to produce good images, it's mostly in the hands and mind of the end user.

Edited by james7ca, 06 December 2019 - 06:29 PM.

[MrRoberts]

Received my Esprit 80 about 3 months ago. It does come with a FF, diagonal, finder and an awesome case. The optics are outstanding. Visually it loves the 6 & 8 Ethos, Quark, MOD 3. For ap it's limited only by the mount. I have used it with my CEM25P without a groan. 

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[Erik Bakker]

It seems that William Optics scopes are recommended overwhelmingly (which I expected, as they have an almost legendary reputation)

WO scopes are OK for the price, but nowhere near legendary. Some really like their color schemes though.

The striking similarity between the William Optics ZenithStar 61 APO and TS Optics Photoline 60/360 shows the business they are in.

 

SkyWatcher makes fair scopes at a fair price. And has good and honest customer support, at least in the USA.

Don't worry about the glass types not being listed. Are they for the lenses you use with your camera? No. All that matters is the quality of the output and if that is to your liking.

 

Overall, including the prices you listed, I would recommend the SkyWatcher Evostar 72ED PRO with included dedicated field flattener, though it may be on the heavy side for your mount.

[Jon Isaacs]

WO scopes are OK for the price, but nowhere near legendary.

 

 

There are legendary WO scopes but these are not they...  The Lomo 80mm F/6 Triplet that was also sold by a number of vendors.  Early on, there was a larger WO with a TEC objective...

 

WO does seem to sell some scopes others don't 5 element 81mm scopes and the like.

 

Jon

[OldManSky]

I was very happy with my WO ZS61 for imaging.  It's very light and portable, has excellent optics, and yet was able to handle a fairly heavy imaging train with no focuser sag or slipping.  I did, finally, sell it and get something a little bigger (WO GT71), and that was a triplet instead of the ZS61 doublet...but I'm on a pier-mounted equatorial, not your intended light setup.  You *will* need the flattener for AP, but with mine I had no problem getting good stars out to the edge of an APS-sized field.

 

I would suggest that some of the bigger-aperture options mentioned are going to be too heavy for the mount you have in mind.  The SW72 and the WO ZS73 are both good scopes, but really need at least a small equatorial mount (like a CEM25P) for good AP.  

 

And yes, the TS you showed (as well as the AT60ED from Astronomics) are the same scope as the ZS61, just without the included focusing mask.  I actually used the AstroTech field flattener for the AT60ED with my WO ZS61 -- it's the same as the original flattener WO sold, just less expensive (though not adjustable like the current one).  It worked great.

 

 

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[MalVeauX]

Why not just get a Rokinon 135mm F2 telephoto for your Nikon?

 

You do not need a telescope for wide field.

 

Very best,

[Tjn58]

Why not just get a Rokinon 135mm F2 telephoto for your Nikon?

 

You do not need a telescope for wide field.

 

Very best,

I agree.  I have a Nikon d5300 and the Rokinon F2.  Another great lens is the Nikkor 180mm F2.8 ed

[SonnyE]

When I was getting ready for the big leap, I had to decide on WHAT I wanted to image, so I could decide what could take me there.

I love Nebula, so I built 3 different wish lists based on my searching and researching. Then groomed them for comparisons.

I didn't have all the great choices available now, and I was trying to keep a lid on the pressure cooker. Hah! That didn't work, I needed everything. And then all the stuff I didn't know I needed.

For a telescope, it came down to that it had to be the best lens I could afford at the time. I trusted Orion products, and they offered what I got, based on advice here and elsewhere from DSO imagers.

As I researched how to get there, I started out looking at a Celestron 6" refractor. But soon realized it was not Astrophotography quality. Funny that the more I refined, the smaller the telescopes got.

I have an Orion ED80T CF, for all the right reasons (for me). Extra low Dispersion glass, Triplet lens configuration, and a Carbon Fiber barrel which aids focus holding over temperature fluctuation (Thermal properties).

A Camera lens for astro imaging.

My next up option added a whopping $1700 onto the cost, for about 1/2" in aperture. $1,000 USD, or $2700 USD.

 

But you have a lot more candy to choose from.

 

From my limited experience with other Williams Optical equipment, I'd put my money in them. There is a ton of quality in their products.

And I'd get the best mount I possibly could, and figure out how to lock stuff in the trunk of your car so you don't have to slep it up and down 3 flights of stairs. And have good insurance.