Avalon Linear on the way!

[codemonkey]

Well, after the bank thinking the transaction was fraudulent and cancelling my credit card, the mount has been ordered at least, probably not quite on the way yet.

[glend]

Congratulations Lee. A very nice piece of gear. Did you get it through Teleskop-Express? I know they offer a UPS options, so will customs clearance be handled by UPS?

[codemonkey]

Sure did Glen, and yep, I went with UPS for shipping. If I remember correctly standard post doesn't offer tracking, and I didn't want a purchase of this magnitude, especially an international one, being freighted without that, which left me with UPS.

I believe UPS will handle the customs clearance as well, but having not done this before I'm not entirely sure how it all works.

[Slawomir]

Wonderful news Lee!

I am really looking forward to hearing/reading your happy feedback and to seeing perfectly round stars in your 30-minute subs :thumbsup:

[codemonkey]

Thanks Suavi, me too ;-)

I did just remember that my imaging laptop is up the creek (only three months old!) and has to go in for a warranty claim too. Hopefully I can get that sorted so I can start imaging soon.

[Bassnut]

1st ive heard of Avalon. Looks very good and has some cool features!. Itll be very interesting to see how it goes for you.

[jwoody]

Nice purchase, bet you can't wait!
Apparently you are 117 Km's from me here on the Gold Coast so hopefully all the bad weather that is coming your way stays clear of me:P
Have fun
Jeremy

[glend]

Lee will this mount be on display at Queensland Astrofest this year?

[Atmos]

Congratulations on the new purchase!! Looking forward to first light :P

I may have to pick your brain about how you go getting it into the country. I've never imported anything more than $500 but I may be on the cards in the new future :)

[codemonkey]

Yeah they're probably most well known over in Europe. I'm yet to hear a bad review, but then they're still relatively new.



haha cheers mate. Given how many issues I've had over the past few months, I think I'm due for some clear skies regardless of new equipment.



The camp isn't that far from me, and given that I'm not the most social of people it's never really seemed worth the effort of packing all the gear up for conditions that are probably the same as what I get at home. Every year I think maybe I'll go this year, but I've yet to do it.... but hey maybe this year ;)



Cheers mate. Happy to share whatever I learn :) Have you made a choice yet?

[Slawomir]

Did a bit more reading about this mount, and it certainly could be my next upgrade from AZ-EQ6. Came across this brochure with technical data: http://www.baader-planetarium.de/avalon/download/Avalon-Linear-Mount.pdf

I hope your mount has already reached our shores Lee!

[Camelopardalis]

That doesn't seem to stop most of the other imagers staking their spot there :lol: :lol:

Looks like an interesting mount, would be good to see it :P

[codemonkey]

Looks the part, that's for sure, and with no bad feedback so far it's looking like a good option.

The mount finally left Germany today ETA of next Monday, although I'm not sure how that will play out with having to pay duty etc. Be nice if I picked it up on Monday though, perfect timing for a birthday present!



lol. Ok, maybe this year.... ;-)

[rustigsmed]

congrats on the new mount Lee, fingers crossed for a smooth teething (pun intended) period.

Rusty

[Atmos]

Really looking forward to seeing what this mount can achieve!

[Slawomir]

Colin, I know that Sara Wager has been using Linear FR mount, and her photos are pretty good IMO: https://www.astrobin.com/users/swag72/

[codemonkey]

When I was asking on SGL for reasons not to buy the Linear, Sara said "It is after all just an EQ6 in red clothes!!!" and, essentially, that I'll not get much better tracking than I do with the EQ6. Having said that she also owns one and swears by it. Not meaning any offence to her, but I'm not sure she understands the significance of it being 100% belt driven, with no worm/gears used.

Anyway, I know the EQ6 can do what I need it to do when it's playing nice, it's the constant fiddling I find myself doing with it to try and get it to play nice that's my issue with them.

I would suggest though, bearing in mind that I've not used the Avalon yet, if you happen to have an EQ6/AZ-EQ6 that's playing nice consistently, reports in the field (i.e from Sara) suggest that your tracking is unlikely to be significantly improved, so it may not be worth the significant upgrade cost. Might not be. I'll find out shortly whether it's worth it to me :-)

[AndrewJ]

Gday Lee

Re


Belts dont mean "better tracking", just that they are more responsive to guide commands, are quiet, and have virtually no backlash/gear meshing issues.

If you ref the blurb in the Linear pdf, you will see



Based on some data i saw from an early unit in the US, the unguided tracking can have quite a large PE, and much of it ( appeared to be ) tied to the teeth on the belts. It was easily guided out as it was quite smooth, but there is no way to say its "better" at tracking than a good worm.
After playing with my AZEQ5, i must say i now appreciate the effects of belt tension on how well a belt drive works, much more than before????

Andrew
Be interested to see yr unguided error plots when you get it.

[codemonkey]

Cheers Andrew. Wasn't meant to imply that the worm was inherently inferior when it comes to tracking, just pointing out that there's no possibility for backlash, which has been a cause for significant frustration for me. In fact, I meant to imply that if yours is working well, you probably won't see much benefit from this, as per reports from people who've owned the mount.

10 Micron are proving what can be done with a worm. It's just a PITA to tweak on SW mounts. I believe the Paramounts also have spring loaded worms to reduce backlash, and probably make adjustment significantly easier I would imagine.

I'd be interested to see more about this early model in the US, as I didn't chance upon it in my research into these.

Unguided PE isn't really a factor for me, what matters most is the shape of it and whether it can be guided out, and by all reports it does very well here. I have no intention of ever running this mount unguided, and indeed as you've pointed out, its own documentation state that it needs to be guided.

I was specifically trying to find people who might have had issues with the mount because I did have some concerns about the toothed belts, but I was unable to find any reports of issues, nor anyone with anything bad to say about the mount (other than it's expensive) when I asked about it.

[AndrewJ]

Gday Lee


No probs there. Its always an electro mechanical tradeoff, and no one system is better than another, esp when cost / benefit tradeoffs cut in.
Ie encoders and direct drive are useless unless the software is designed to suit the whole system, but many believe a mount with direct encoders is "inherently better"
Same with belts, they have pros and cons.

I will need to ask if the user is happy for early data to be posted, as he was testing very early versions of the firmwares as well, so part of it is not a fair test, esp when RA drift cuts in.
That said, the mechanical effects of the toothed belts were immediately obvious, as definite "ripple" in the tracking.
Some of the worst tests showed over 100 arcsec of PE, but as the final output gear is only 66 teeth, this equates to about a 22 minute period, and as noted, it was relatively smooth, so easily guided.
I know based on my recent grief with my AZEQ5, that belt tension can have a huge effect on how well a belt drive tracks, and maybe the later Avalon units have a better tensioning system. Dunno, but a few unguided tests will show that up pretty quickly.

Andrew

[Atmos]

The main reason I am planning on getting rid of my EQ6 is because I do want to get rid of the tiny ripples that cannot be guided out, 1" oscillations that happen sub second, some of which is an artefact of seeing but other parts are purely imperfections within the mount.

I think this is where the Linear will be better, having something like a four stage reducer it not only gets rid of backlash but should vastly smooth out all those little inconsistencies that cannot be guided out. The 30" PE that my EQ6 has is fine, that is not even noticeable, its those small bits in between :)

[AndrewJ]

Just for info, have attached a piccy of my AZEQ5 before and after tweaking the belt tension. The linear has much larger/stonger belts, and probably has a more precise belt tensioning system, but it pays to understand what can happen, even with belts ;)

Andrew

ie Some problems can be removed at the expense of possibly introducing new ones.

[billdan]

Hi Andrew,

That black graph looks heaps better with much less ripple.

Interestingly it seems the error is mostly negative arcsec, ranging from -20 to +2 as if the motor is turning too slow. If you could speed that up slightly it would also improve the graph.

Anyway its a big improvement, I wonder if many other users know that trick.

Regards
Bill

[AndrewJ]

Gday Bill

You are slightly misinterpreting the graph.
I have normalised my plots and then taken a snapshot from a section of the plot that highlighted the before and after effects.
The underlying tracking rate is actually pretty good.

Andrew

[codemonkey]

I'm not sure if the multi-stage reduction will have much of an impact there, maybe an engineer can chime in?

I've been thinking about trying to build my own mount (as a project, not a commercial endeavour), and having considered building a friction drive or belt driven system, I suspect that multi-stage reduction is simply there to keep the physical dimensions small.

You need a really large reduction ratio to move something in small enough increments that it's suitable for tracking with a stepper motor.

Worm gears are great being a "simple" single-stage mass reduction step, but when using a friction or belt system, you need another way of creating very large reduction ratio.

To give you an idea, the EQ6 has a ~700x reduction ratio so it can move in steps of around 0.14" (from memory). Of course, if you tried to have a 700x reduction ratio with one pulley, you'd have a 7m pulley on one side and a 1cm one on the other (or a 70cm, 1mm for that matter, but you get the idea).

However if you use a multi-stage approach, you can greatly reduce the physical size by making a pulley version of a compound gear. Maybe it has some impact on high frequency noise as well, but I'm not sure about that (but then again, I know jack about mechanical engineering as well, so I'm keen to hear about it if someone knows more on this).

I'm actually a bit cynical on timing belts because they must introduce some relatively high frequency noise into the system, so I'm still expecting some small-scale, high-frequency fluctuations, however I'm not expecting them to be significant enough to cause me issues imaging at 1.1"/px.



Thanks for posting that, interesting graph! Excuse my ignorance, but can you please confirm the scales on each axis?

Edit: Soooooon

[AndrewJ]

Gday Lee
For the upper graph, the left axis is in "axis" arcsecs.
This was just a grab of unguided, PEC off data, to see what the raw tracking was like. The large ripple due to the belt teeth shows very clearly, superimposed on the much larger worm error.
The lower graph is an FFT analysis ( similar to what PEMPro would do )
The left axis is scaled such that the maximum fundamental detected in the data becomes 1.
In my case, the worm ( ie fundamental 1 ) is plotted as 1.0, as it has by far the larges amplitude.
The no 36 fundamental is showing up as approx 0.11, and that indicates the PE caused by the belts meshing is approx 11% the magnitude of the primary PE of the worm, and hence is noticeable.

Andrew

[Atmos]

I have looked into friction drives like the Mesu and they look really interesting... Buggered if I know how they actually work though :rofl:

[Slawomir]

I think satisfaction with EQ6/AZ-EQ6 varies from person to person. It largely depends what telescope sits in top of it and also how descending a user is in terms of quality data. In case of narrowband imaging, in particular with 3nm filters, I feel that tracking errors will show more readily as opposed to RGB imaging. Same as you Lee, I have found that although my mount can deliver outstanding data, many subs are substandard.

I have faith, based on evidence/data available on the net, that Linear FR will consistently track more smoothly than Synta mounts. And with auto guiding, PE does not need to be small, as long as it is smooth.

I still have a HEQ5 that has a relatively small PE, but it also has sudden ripples so it is not optimal for the type of photography I do. This graph shows 50 minutes of unguided tracking: http://www.iceinspace.com.au/forum/attachment_browse.php?a=170518

I suspect that several guys on IIS (me for sure!) are quite curious about this mount's usability for AP :thumbsup:

[codemonkey]

Aha, ok, thanks for clarifying Andrew. Just looking at that graph it looks like while the change might have improved #36, #4 seems to have gotten worse.



Basically just a big metal disc pressed up against a small metal shaft. As the small shaft rotates, it rotates the big disc by friction. There's no gears, or lubrication, just metal on metal, so there's no slack in the system, no possibility for backlash.



That graph actually looks pretty good to me for an HEQ5. Not that I've ever looked into those, but I expected them at least to have a greater amplitude than the NEQ6 but that doesn't look to be the case.

[AndrewJ]

Gday Lee

Correct, but the overall result is much smoother over time ( esp by removing the high freq 36 ripple ), and hence is easier to guide.
Im not 100% sure where the no 4 fundamental really comes from
as the worm has a 36 to 12 tooth belt reduction
and the stepper has an inbuilt 2:1 gearbox.
I assume that by increasing the belt tension, it has changed the loading inside the gearbox, and this results in the changes seen.
That said, interpreting some FFT data is not as simple as saying, fundamental 4 is large, hence it is something that repats 4 times per rev of the worm.

Andrew

[codemonkey]

With the new mount due to arrive on Monday, the weather gods are up to their old tricks. (red means cloudy, basically, if you're not familiar with clearoutside.com).

No matter anyway, I've only just gotten the retailer who sold me my imaging laptop a mere three months ago to agree to have a look at it after the battery decided to go kaput, so there's not a lot I can do with the mount right now anyway.

[Slawomir]

Lee, I will be looking forward to reading your first initial impressions with the mount on Moday night then :)