#1  
Old 01-06-2013, 04:31 PM
JohnH's Avatar
JohnH
Member # 159

JohnH is offline
 
Join Date: Feb 2005
Location: NSW
Posts: 1,179
G11 upgrade - Ovision or Losmandy one piece

Hi G11 owners - I am looking for some advice on the pros and cons of these upgrades - my G11 has the standard 2 piece worm bearing blocks - and a PE of about 25" peak to peak. I think this can be tuned out by those more mechanically gifted than me but the new worm blocks seem to offer an improved performance without too much tweaking. Is this upgrade worthwhile and if yes which of these options do you recommend? I am leaning towards the Ovision currently.
Reply With Quote
  #2  
Old 01-06-2013, 07:20 PM
Lee's Avatar
Lee
Colour is over-rated

Lee is offline
 
Join Date: Sep 2005
Location: Newcastle, Australia
Posts: 2,414
I'm planning on getting a new worm also, probably ovision, perhaps the new one-piece from Losmandy though.... there is more info at the "Losmandy German Equatorial Mounts" yahoo group....
Reply With Quote
  #3  
Old 02-06-2013, 01:56 PM
JohnH's Avatar
JohnH
Member # 159

JohnH is offline
 
Join Date: Feb 2005
Location: NSW
Posts: 1,179
Quote:
Originally Posted by Lee View Post
.... there is more info at the "Losmandy German Equatorial Mounts" yahoo group....
Yup I have been there - I was hoping for local experiances though. From my reading it looks like the Losmandy OPWB solves only one issue - that is the 76s wobble you may get if your worm blocks are out of alignement. The Ovision uint has a better worm and will reduce PE - by how much is not clear precisely but in my case by perhaps halving it or less. The 76s error is also gone. I am 90% convinced the Ovision is worth the extra $$. I image at 2000mm so a smooth, slow chnging PE is going to make my guiding easier.
Reply With Quote
  #4  
Old 02-06-2013, 02:12 PM
Lee's Avatar
Lee
Colour is over-rated

Lee is offline
 
Join Date: Sep 2005
Location: Newcastle, Australia
Posts: 2,414
This fellow posted some encouraging results....
http://kizny.com/astro/losmandy-g11-...rophotography/

My stock G-11 has a PE of around 10-15 arcsec, but has a rapid jerky error approx every 2-3 min, that guiding struggles to keep on track.... I printed out my ovision order form this morning....
Reply With Quote
  #5  
Old 02-06-2013, 05:35 PM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,243
Quote:
Originally Posted by JohnH View Post
Hi G11 owners - I am looking for some advice on the pros and cons of these upgrades - my G11 has the standard 2 piece worm bearing blocks - and a PE of about 25" peak to peak. I think this can be tuned out by those more mechanically gifted than me but the new worm blocks seem to offer an improved performance without too much tweaking. Is this upgrade worthwhile and if yes which of these options do you recommend? I am leaning towards the Ovision currently.
I can't talk about the ovision which I suspect has an excellent quality worm but I have a Losmandy high precision worm and one block both in RA and DEC. In my experience it greatly helps with alignment Saying that you'll get better PE depends on a lot of other factors.

Gearbox, bearings, worm quality (eccentricity), state of the gears, orthogonality, meshing. Here's what works for me and what to look for before you buy the one block configuration.

The gearboxes, well I'm not sure how they affect PE but bad ones will affect your backlash even with good meshing and that drives me nuts enough to get 'tighter' ones.

Check your bearings. One hard spot is very easy to feel and that will bugger your PE big time. Just get one end block with the bearing in it then slide the end of the worm in there. Just press a little side ways to 'load' the bearing then turn back and forth feeling if it's smooth, then offset and keep doing it over the whole 360. Little steps back and forth. If you feel any 'click' or 'grinding' even insignificant bin the bearing and change it. You'd be surprised how many so called high precision bearings or other are dodgy.

Worm quality. I guess the only one that comes with a 'certificate' is the Ovision. The losmandy high precision worms are not consistent.

Meshing can be achieved with the two single pieces. It takes a little practice but you can achieve better meshing by shimming than with the one block. The reason is that you still can see the worm, mesh it in the gear, then check the gaps under and behind the blocks and shim them. Hard to see anything going on with the one piece block.

Another issue with the one piece block is that you need to couple the gearbox to the worm before meshing it in. So no chance of 'feeling' by hand the hard spots around the circumference of the gear. Although I'm thinking of drilling a small access hole in the cover to be able to sneak in an Allen key to couple the motors after I did the meshing by hand.

Make sure the coupling is tight against the worm but use a 0.4mm gauge so it's spaced out enough. Very important to secure the coupling on the gearbox shaft first then secure the gearbox on the plate, so everything is inline without any stress or you'll stress the coupling and the worm will be harder to rotate.

Finally clean your gear thoroughly before meshing. Turp them up and get rid of all old dry grease with a toothbrush and tooth pick.

Inspect the worms and gears. Keep both the good ones for the RA, the other goes in DEC.
Reply With Quote
  #6  
Old 04-06-2013, 04:48 PM
Lee's Avatar
Lee
Colour is over-rated

Lee is offline
 
Join Date: Sep 2005
Location: Newcastle, Australia
Posts: 2,414
Scanned and emailed my order form to Ovision at lunchtime today, got an email 4hr later advising the worm has been sent.... Can't fault them so far!
Reply With Quote
  #7  
Old 02-08-2013, 05:54 AM
JohnH's Avatar
JohnH
Member # 159

JohnH is offline
 
Join Date: Feb 2005
Location: NSW
Posts: 1,179
Quote:
Originally Posted by Lee View Post
Scanned and emailed my order form to Ovision at lunchtime today, got an email 4hr later advising the worm has been sent.... Can't fault them so far!
Has your new worm arrived - fitted ok - are you happy with the results?
Reply With Quote
  #8  
Old 02-08-2013, 08:26 AM
Lee's Avatar
Lee
Colour is over-rated

Lee is offline
 
Join Date: Sep 2005
Location: Newcastle, Australia
Posts: 2,414
Yes, arrived, fitted easily, very happy with results.
The standard worm was giving me around 11arcsec PE from memory, the ovision around 5-6, and very smooth....
Guiding RMS values have halved since....
Reply With Quote
  #9  
Old 19-09-2013, 09:27 AM
JohnH's Avatar
JohnH
Member # 159

JohnH is offline
 
Join Date: Feb 2005
Location: NSW
Posts: 1,179
I took the plunge and ordered the Ovision worm and am also very happy with the results. My native PE is now about 7" peak to peak - it was over 15 previously - but more important, as has been reported by others the PE change is now very smooth so PEC works well and reduces this to about 2-3" peak to peak. I can use guide exposures of 7s or more now and still get round stars at an image scale of 0.76-1.14"/pixel - great for NB imaging with my ST2000 (guide chip behind the filters).

I had a struggle fitting it though. Not because of the Ovision worm, that was in perfect order, but because the Losmandy assemblers were overzealous in torquing down the 1/16" grub screws on the Oldham coupler and worm dust cover. One was even cross threaded (on the dust cover). I used a small Torx head (size 10 iirc) to get them out - the provided allen keys were too loose (hex heads must have been rounded out by over tightening). It would have been a 30 min job apart from that.

Very Happy.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:57 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Lunatico Astronomical
Advertisement
Celestron Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
Meade Australia
Advertisement
Bintel
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement