Zwo harmonic mount pretty much confirmed

[eshy76]

Harmonic drives are heaven for portable widefield imaging, or anything below 800mm focal length.

They are strong mounts with zero backlash, no balancing of OTA needed, no counterweight needed except if you’re worried your tripod will topple, a gentle PE curve that can be guided out to a consistent 0.5-1 arc seconds. And all this in a mount weighing a backache killing 5kg (my RST-135 is actually 3kg!).

The mounts can easily cope with Edge HD scopes weight wise, but the need to use something like 0.5 second guide exposures make it hard to use an OAG for guiding.

I think £2k is quite compelling for the above if the quality is good.

[nfotis]

just saw it mentioned on the ZWO page:

"guiding accuracy is 0.5 to 0.8 arc seconds"

So, I suppose that puts a lower limit to the guiding accuracy, right?

Aside: If I want to use my C9.25 for DSO imaging or my Skymax 180, would a CEM40/EQ6-R and an OAG manage an accurate enough guiding? Or I would have to go to a pricey mount?

N.F.

[The Admiral]

Happy Christmas!

I don't feel I know enough to answer this question, but how often is the seeing good enough for the mount limitations to become limiting?

Ian

 

Edited December 25, 2021 by The Admiral

[StarryEyed]

Happy Christmas! 

I suspect every tom dick and harry will come out with one of these mounts . The reason being you can buy the drive and build the housing. Every other mount has a lot of parts that need to be manafactured assembled and setup. In some respects I could buy a harmonic drive and make my own housing the problem is coupling the drive to a tripod and coupling a scope to the end of the drive. 

In fact if Rowan are reading this then it might be something relatively easy to achieve. Probably at least as easy as a motorised AZ100 after all companies with no experience with mounts are starting to turn them out! 

Dear Santa, next Christmas I want a Rowan harmonic mount. I promise to be good. 

Edited December 25, 2021 by StarryEyed

[UKDiver]

9 hours ago, nfotis said:

Car industry is testing new cars much more heavily than other consumer items, because each new car is being sold in the millions.

Yet they still get it wrong, including safety based issues requiring recalls.

Fortunately astro gear is far less complex so the amount of testing reflects that. Not that this should excuse a rush to market with shoddy kit.

[Hogarth]

Just my own thoughts

[The Lazy Astronomer]

6 hours ago, nfotis said:

just saw it mentioned on the ZWO page:

"guiding accuracy is 0.5 to 0.8 arc seconds"

So, I suppose that puts a lower limit to the guiding accuracy, right?

Aside: If I want to use my C9.25 for DSO imaging or my Skymax 180, would a CEM40/EQ6-R and an OAG manage an accurate enough guiding? Or I would have to go to a pricey mount?

N.F.

0.5 - 0.8" RMS is the typical guiding I get with my EQ6R Pro.

The guiding performance you need depends on your image scale. What camera will you be using with the C9.25?

Also, be aware that 1"/px is generally accepted as the limit for long exposure astrophotography due to the atmosphere, and even then, that will only be on the nights of the best seeing.

[900SL]

18 hours ago, Elp said:

I think given the option the majority would choose an eq6 pro. Also as it's zwos gen 1 product it needs time to prove itself. Other manufacturers are already generations ahead experience wise for this type of thing.

How much experience does ZWO have of making mounts prior to this?

Is it manufactured in house or a subcontracted assembly of supply chain lowest tender cost components?

I'll wait a year.. and maybe RST prices will come down a touch..

 

[nephilim]

9 hours ago, nfotis said:

just saw it mentioned on the ZWO page:

"guiding accuracy is 0.5 to 0.8 arc seconds"

So, I suppose that puts a lower limit to the guiding accuracy, right?

Aside: If I want to use my C9.25 for DSO imaging or my Skymax 180, would a CEM40/EQ6-R and an OAG manage an accurate enough guiding? Or I would have to go to a pricey mount?

The C 9.25 @ 9kg & Skymax @ 7kg you'll easily accommodate them on the EQ6 Pro with an imaging capacity of 20kg

 

[raadoo]

@Hogarth over on CN, someone from ZWO posted to confirm that it will support ASCOM and conversely that the ASIAir will continue to support third-party mounts.

Quick errata: Yannick (Cuiv, The Lazy Geek) had the Hobym Crux, which he sent back. Not the Rainbow Astro.

Edited December 25, 2021 by raadoo

[nfotis]

2 hours ago, The Lazy Astronomer said:

0.5 - 0.8" RMS is the typical guiding I get with my EQ6R Pro.

The guiding performance you need depends on your image scale. What camera will you be using with the C9.25?

Also, be aware that 1"/px is generally accepted as the limit for long exposure astrophotography due to the atmosphere, and even then, that will only be on the nights of the best seeing.

I am considering either the IMX533 or the IMX571 for DSO imaging. For planetary, I am using the IMX462.

 

Note that the claimed ZWO accuracy puts a floor (minimum) to accuracy. You cannot be better, even with guiding, while a CEM40 or an EQ6-R mount can do better (if I understand correctly).

At the moment, I own a HEQ5 mount, with no pretensions of doing DSO imaging (but I bought a 102ED refractor, which should work well)

N.F.

Edited December 25, 2021 by nfotis

[vlaiv]

14 minutes ago, nfotis said:

I am considering either the IMX533 or the IMX571 for DSO imaging. For planetary, I am using the IMX462.

 

Note that the claimed ZWO accuracy puts a floor (minimum) to accuracy. You cannot be better, even with guiding, while a CEM40 or an EQ6-R mount can do better (if I understand correctly).

At the moment, I own a HEQ5 mount, with no pretensions of doing DSO imaging (but I bought a 102ED refractor, which should work well)

N.F.

Actually, you'll have hard time getting stock either CEM40 or EQ6-R to perform below 0.5" RMS guided.

You need to spend at least double that to get mount that will go below 0.5" RMS guided reliably.

1"/px mentioned is pretty much lower bound for any mount and any amateur imaging system. You simply can't get sharper images than that in long exposure astrophotograpy (and in fact - it really takes effort and money to even come close to 1"/px).

Stating focal length is not very helpful - if you already have lower bound on sampling rate - then you don't really care if people will get 1"/px with 800mm FL or with 3000mm FL - and in fact, mount does not care about focal length of instrument.

Only possible benefit of this mount is lack of backlash - and that should enable good / responsive guiding. Stating that lower bound is 0.5-0.8" RMS does not provide much of a confidence. I've seen 0.36" total RMS on my Heq5 (which is heavily modded / tuned).

iOptron system with spring loaded worm gear should be similarly backlash free if implemented properly.

[nfotis]

What I understand is that ZWO is not promising better accuracy than 0.5 to 0.8 at seconds, due to the design and implementation of this harmonic drive.

A belt drive EQ6-R or CEM40 can run better than that, if I understand correctly, but not this mount.

N.F.

 

[vlaiv]

2 minutes ago, nfotis said:

A belt drive EQ6-R or CEM40 can run better than that, if I understand correctly, but not this mount.

I'd like to see stock EQ6-R or CEM40 that run better than 0.5" RMS

[barbulo]

7 minutes ago, vlaiv said:

I'd like to see stock EQ6-R or CEM40 that run better than 0.5" RMS

Last 3 sessions early this week I managed to get below 0.5” (closer to 0.4”) for over 3 hours with a stock EQ6-R Pro. PPEC proved a good ally along with a good leveling, balancing and PA. Not the regular values though: normally 0.5”-0.6”. And without a permanent observatory. 
Very happy with this mount (the only component that I managed to get a good performance from) 😭

[vlaiv]

1 minute ago, barbulo said:

Last 3 sessions early this week I managed to get below 0.5” (closer to 0.4”) for over 3 hours with a stock EQ6-R Pro. PPEC proved a good ally along with a good leveling, balancing and PA. Not the regular values though: normally 0.5”-0.6”. And without a permanent observatory. 
Very happy with this mount (the only component that I managed to get a good performance from) 😭

What is your guide resolution?

[barbulo]

1 minute ago, vlaiv said:

What is your guide resolution?

3.52”/px I believe (ASI224 in a 8x50 - 220mm fl - guidescope). 

[vlaiv]

2 minutes ago, barbulo said:

3.52”/px I believe (ASI224 in a 8x50 - 220mm fl - guidescope). 

That is very close to resolution limit of guide system. I'm not overly confident in accuracy of reported RMS.

Some estimates of guide system resolution are between 1/16th to 1/20th of pixel size. In your case, if we take 1/20th - we get 0.176" as accuracy limit (for 1/16th it is even higher).

In my estimate, you need at least three times higher resolution of guide system than RMS figure you are trying to measure. With 0.176" resolution - I'd say you are relatively accurately measuring RMS down to 3 x 0.176 = 0.528.

This is very close to figures you reported and I'm not sure that measured figures are very accurate.

 

[barbulo]

PHD2 to blame then. But I should be happy with everything below 0.6”, no?

[vlaiv]

7 minutes ago, barbulo said:

PHD2 to blame then. But I should be happy with everything below 0.6”, no?

PHD2 will report what it can calculate, and actual figure can be lower or higher, but it should not concern you too much as it is on lower side of things - which is good.

It will also depend on DEC of target - higher the DEC - less resolution there is in measurement (error is smaller in pixels).

Ultimately, performance will reflect in stars in the image - if stars are tight and round, then you should not really worry too much about it all.

[nfotis]

If we use an OAG, that should take care of the resolution limit of the guiding system, right? Then, we could see what's the accuracy limit of the mount, I suppose?

N.F.

[pete_l]

On 25/12/2021 at 04:54, eshy76 said:

And all this in a mount weighing a backache killing 5kg (my RST-135 is actually 3kg!).

Is that really much of a benefit when a person would load the mount with up to 20kg of other equipment? It isn't as if you'd attach everything to it and then carry the whole thing to its place of use.
I see a mount as one component of a system. As such it is difficult to see what benefits this contributes, that a more mainstream mount would not be able to do for a similar price.

[Ouroboros]

During the last year I ventured down the ZWO path and acquired a OSC camera, guider and ASIair. It occurred to me then that the only thing missing in their product range was a mount. So I’m not surprised they have now entered that market too. As mount designs go it’s also an obvious choice for them because the equatorial market is already quite well served; plus the competition in these harmonic mounts are somewhat expensive.  They probably reasoned they could bring their particular flare for bringing affordable and easy to use astro products to producing and marketing a mount like this. 

I will be following the response to this mount with considerable interest once it goes on sale. I have wanted to replace my very old, non-goto EQ5 as a portable mount for some time. I was tempted by the Rainbow 135, but thought it expensive for what it was. I tried an iOptron GEM45 and didn’t like it. So I’m hoping this ZWO mount might fit the bill. 

[vlaiv]

9 hours ago, nfotis said:

If we use an OAG, that should take care of the resolution limit of the guiding system, right? Then, we could see what's the accuracy limit of the mount, I suppose?

N.F.

Yes.

Sometimes people report much worse guiding graph when switching to OAG. Some of it is due to reporting of guiding results in pixels instead of arc seconds and some of it is because of guide resolution/precision. With increased precision they are now getting actual results and that surprises them.

[wimvb]

19 hours ago, raadoo said:

@Hogarth over on CN, someone from ZWO posted to confirm that it will support ASCOM and conversely that the ASIAir will continue to support third-party mounts.

Quick errata: Yannick (Cuiv, The Lazy Geek) had the Hobym Crux, which he sent back. Not the Rainbow Astro.

That answers the question I had. If ZWO would drop support of other mounts, they could as well discontinue the ASIAir.

What also surprises me, is that this is the second harmonic drive mount I've come across within this last week.

https://www.aliexpress.com/item/1005003408574030.html