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ZS61 first light


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ZS61 Refractor..First Light Report

First, a big thank you to FLO for selling the scope quite a bit cheaper than some of the competition. It arrived very well packed, with the original manufacturer’s cardboard box put into a larger box with polystyrene chips. All very safe and secure.

So why the ZS61? I already own a GT81 and an old Pentax SHDF75. Both are optically excellent. Well, I travel to France a lot and I wanted something more Ryanair compliant. Both the other scopes are a bit porky for my Star Adventurer mount; I wanted something that would be well inside the 5kg mount limit with 2” diagonal, eyepieces, or SLR with flattener. And the whole kit and caboodle including mount and tripod would ideally be small enough not to incur extra baggage charges with Baron O’Leary’s flying circus.

I chose the red one, basically to match the mount. Much has been made of the compact-and-bijou-ness of this scope and it doesn ‘t  disappoint. Finish and fit are generally excellent. You don’t get a travel case for the basic price which seems a bit tight for what is intended as a travel scope, but I’m keeping the foam insert from the original packing in the hope of finding something the right size. Maybe Gucci or Prada could get in on the emerging market for fashionable scientific instruments and come up with a dinky carry case with colour coded strap?

A small niggle: the focus knob cover has been downgraded from machined aluminium to black plastic. It’s a trivial point but not in keeping with the WO reputation for fit and finish. On the other hand there is a lot to like..they have kept the knob thermometer, the Rack and Pinion focuser is miles ahead of some of the dreadful Crayford efforts they’ve used in the past. The dewcap feels tight and stays up with the scope vertical (but I’d still prefer to see a locking screw). And it’s LIGHT..like a couple of bags of sugar. One thing that has changed is that WO seem to be adding a touch of grease to all the thumbscrew threads and the focuser rack. Some might decry this as risking messing up the optics but I’ve been doing this for years with all my scopes and never has an issue. Just a trace is enough to stop that vile metal-on-metal squeaking noise.

It’s virtually essential to reverse the mounting foot to have any hope of balance unless you’re using a cheap 1.25” diagonal and super light eyepiece.

Visual use

So what’s it like to look through? I tried with the following eyepieces:

30mm Vixen LV (2”)    *12, 5 degree field

11mm MK1 Nagler     *33, 2.5 degree field

3.5mm Myriad            *103, 1 degree field.

My ageing eyes don’t appreciate exit pupils much smaller than 1mm ( floaters) so this scope probably has more magnification potential than I can personally handle. The 3.5mm is my useful limit. 

Sky conditions: No moon, seeing spoiled by very thin mist. Milky Way just about visible.

Star testing on Vega with the 3.5mm, the colour correction appears to be excellent. Seeing wasn’t the best but most of the light was in the Airy disc, with the first couple of rings faint but clear. The patterns look about the same either side of focus and nicely round. No signs of mis-collimation to report. Epsilon Lyrae was split with some difficulty (seeing); I have no doubt it would be a lot easier on a better night. For some bizarre reason the closer asymmetric pair was the slightly easier split on this occasion. I would expect this scope to be good on the moon and planets within its limited resolving capacity.

The 11mm Nagler is just beautiful with this scope. The magnitude and field are ideal for scanning the Milky Way star fields and stars are tight right to the edge. The 2mm exit pupil darkens the sky enough to fully appreciate the ED refractor diamonds-on-velvet party trick.

The view through the 30mm Vixen was a slight disappointment. This is basically a binocular view with a 5mm exit pupil and the sky was not really dark enough to make the most of the enormous 5 degree field. M31 looked completely lost in the enormous light polluted field with just the core really visible. The Double Cluster looked faint. It was hard to pick out the red giants, no wow factor. It wasn’t the fault of the scope so much as the conditions, but I found myself inevitably comparing the view to a 6” Newt…this eyepiece/ magnification is best reserved for the middle of Wales or France. One service the 30mm does perform well is that of finder. There is no finder foot on the scope and no holes to mount one; you are dependent on sighting along the barrel with a very low magnification eyepiece.

So the visual verdict is generally good, but not gushing with superlatives. It’s not a reflection on build quality, just that 61mm is a very small aperture. Even the step up a GT81 is very noticeable improvement. I expect the little scope to be better on planets than deep sky when the opportunity arises.

Photographic use

Taking pictures abroad was the real reason for this scope. The relatively short focal length (360mm) and low weight look like a good match to a portable unguided mount like the Star Adventurer. I already have a FF/ reducer for the GT81 so the obvious question was whether it would work ok on the ZS61 as well. It’s probably not optimal or they wouldn’t bother making a special, but it’s a free shot.

Last night (Tuesday 19 Sept 2017) was the last night predicted to have any useable breaks in the cloud for some time so I hurriedly set up. Polar alignment was not too careful and there was a significant breeze.

Below are 2 shots, both 2 minute subs on the SA. Both use a Lumicon Deep Sky filter with a Canon 1100D set to ISO 1600. No processing of any sort has been used, just conversion from CR2 format to JPEG.

Focusing was done on Altair with a Bahtinov mask, and the scope then moved to M27 by experience and guesswork. Even though M27 is one of the brightest of deep sky objects, it is still invisible through the camera viewfinder. The field on a APS-C sensor is 3.8*2.5 degrees without the FF in place and I still managed to almost miss the target completely. Remember, there is no finder or provision for one…on a HEQ5 or similar this would not be an issue since the GOTO pointing accuracy would at least put the target in the FOV, but on the little SA this can be a nuisance. Once on the sensor it is slow but not difficult to frame the subject moving RA on the SA buttons and the declination knob. I left these shots as the initial aim to illustrate the issue. Swapping over I managed to accidentally twist the camera orientation by about 45 degrees.

The speed increase going to the FF/ reducer is obvious and the corners do look tidier to my eyes. There are some slight blue haloes but in general I’m pleased with the optical performance.

I’m going to experiment with a Vixen flip mirror to ease the finding difficulties. The problem will be that flip mirrors always mess up the FF spacing. If I can live without 2” eyepieces the flip mirror will be a weight saving over the bigger diagonal. Fortunately there is 75mm of travel on the focuser which will accommodate a of accessories.

 

Conclusions

This is a very good scope but you need to buy it for the right reasons and appreciate its limitations. As is common with a lot of small refractors, it’s a better photographic tool than visual when used with one of the portable equatorials now available. It probably shouldn’t be your only scope or even your grab-and-go, but as a travel scope it has very few quality rivals at this weight point. You can get better photographic performance with a GT81 at twice the cost, or better visual performance from a PDS150 at half, but neither can be carried in a rucksack to the Gobi Desert. It needs assessing at a really dark site, even a 60mm picks up about 100 times the light of a naked eye. When it’s not travelling, it will look really cool on the mantelpiece. Recommended with reservations.

20 Sept 2017, RL

 

 

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Very useful and thorough report, thanks for taking the time to write it up.

I agree 60mm is pretty limited but under a dark enough sky can be highly effective visually.

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Thanks for posting such a comprehensive and fun to read report :) It's such a tough call weighing up portability against aperture for visual, but it does sound a perfect match for the SA and AP.

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Davey-T..

Thanks for the RDF in the hotshoe idea. I did not realize such an item was available. That sounds the perfect solution. ....

Thanks to everyone else for the favorable feedback

RL

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Nice report, thank you.  Interesting, and very helpful.

I ordered one yesterday!  My reasons were much the same - ultra-portable scope that would fit in carry-on camera rucksack, to use on small tracking mount.  Travelled to a few places over the last 12 months when I wished I'd had something exactly like this.

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Interesting review, I'm evaluating this for myself as well.

Do you think the defects in the border are due to the reducer not properly fit?

As far as I know they have to be at a precise distance from the camera, depending on the focal length...

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7 hours ago, GuLinux said:

Interesting review, I'm evaluating this for myself as well.

Do you think the defects in the border are due to the reducer not properly fit?

As far as I know they have to be at a precise distance from the camera, depending on the focal length...

It's as well to remember I was using the wrong reducer simply because it was what I had to hand....I used the version 6 intended for a GT81. Yes, you are absolutely correct, the spacing is critical with these things for best results. Also, the polar alignment was done in a hurry (but the error will still be only a small fraction of a degree) which will add a general error over the whole frame. The focal ratio is about the same as the GT81, but the field curvature to be straightened out might be quite different since the GT81 is a triplet.

I'm going to try a few more with precise alignment and a sturdier tripod which will stand up to breezes better..rule out all the possible sources of bloated stars first. . I really don't want to buy another FF unless it's really essential. I'm not the sort of person who is going to obsess over slightly egg-shaped stars right in the corners as long as they're not obvious. I'm not a perfectionist; the way I see it the main subject of the shot should be enough to hold your attention over a few residual optical defects. Maybe this disqualifies me from making a valid review, but I guess we all have our own threshold of what's acceptable given the kit and conditions. If necessary, I guess an extra £139 (discounted from FLO) won't be the end of the world on top of the scope and mount costs to make it work properly but I do resent having to shell out on expensive extras for every scope I've got for doing virtually the same thing. On the other hand, if you do take it up the Matto Grosso on that once-in-a-lifetime trip, it would be a pity to compromise the results for so small a cost relative to the whole expedition! First world problems.....

Last night was a lot clearer. The visual performance was noticeably more convincing. I made a lot of silly procedural operating mistakes but there might be some more photos to follow, all taken without a FF since I was using a flip mirror to frame the targets. I really must get myself one of those hotshoe RDF jobbies  another 40 quid from 365astronomy!

In its own way it really is a very good scope, particularly the lack of CA. Not just a pretty face...

RL

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49 minutes ago, rl said:

It's as well to remember I was using the wrong reducer simply because it was what I had to hand....I used the version 6 intended for a GT81. Yes, you are absolutely correct, the spacing is critical with these things for best results. Also, the polar alignment was done in a hurry (but the error will still be only a small fraction of a degree) which will add a general error over the whole frame. The focal ratio is about the same as the GT81, but the field curvature to be straightened out might be quite different since the GT81 is a triplet.

I'm going to try a few more with precise alignment and a sturdier tripod which will stand up to breezes better..rule out all the possible sources of bloated stars first. . I really don't want to buy another FF unless it's really essential. I'm not the sort of person who is going to obsess over slightly egg-shaped stars right in the corners as long as they're not obvious. I'm not a perfectionist; the way I see it the main subject of the shot should be enough to hold your attention over a few residual optical defects.

Well of course, but I was mainly referring to myself: I don't have any flattener/reducer at all, so I might as well buy the right one from the beginning :)

 

49 minutes ago, rl said:

Maybe this disqualifies me from making a valid review, but I guess we all have our own threshold of what's acceptable given the kit and conditions. If necessary, I guess an extra £139 (discounted from FLO) won't be the end of the world on top of the scope and mount costs to make it work properly but I do resent having to shell out on expensive extras for every scope I've got for doing virtually the same thing. On the other hand, if you do take it up the Matto Grosso on that once-in-a-lifetime trip, it would be a pity to compromise the results for so small a cost relative to the whole expedition! First world problems.....

Be aware that the flattener listed in FLO is only a flattener, not a reducer, hence you'll have a bigger focal length.

I'm trying to make up my mind, but I'm still very undecided between the WO, and a couple of TS-Optics photoline scopes (a 60mm F330, which I'd prefer for the shorter focal length, but it's a bit too much expensive compared to the WO, and the 72mm F400, only slighly more expensive than the TS 60mm, but of course heavier and with an excessive focal length for the Star Adventurer).

But on the TS scopes there's this focal reducer listed: https://www.teleskop-express.de/shop/product_info.php/info/p10025_TS-Optics-PHOTOLINE-2--0-79x-Reducer-4-element-for-Astrophotography.html

As you can see from the description, depending on which scope you use it, you just need to adjust the distance between the reducer and the camera. Maybe the same applies to your WO reducer?

 

49 minutes ago, rl said:

Last night was a lot clearer. The visual performance was noticeably more convincing. I made a lot of silly procedural operating mistakes but there might be some more photos to follow, all taken without a FF since I was using a flip mirror to frame the targets. I really must get myself one of those hotshoe RDF jobbies  another 40 quid from 365astronomy!

In its own way it really is a very good scope, particularly the lack of CA. Not just a pretty face...

RL

That's another thing I'm very interested into :) Pictures without the reducer... I have an ASI 1600mm, so smaller chip, maybe I could do without it as well :)

 

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