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fluX

New Avalon Linear or second hand Mach 1 GTO

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I have been assessing my unguided periodic error and RA drift on my Avalon M Uno. In fact they are ridiculously large. I have no idea where the +/- 7 arc-sec figure comes from. The periodic error on my mount over the 4 stage belt/pulley reduction is somewhere in the 40-50" total range. But these mounts are unique. IMO, periodic error is meaningless with these mounts.  Yes, they must be guided, but they guide superbly, perhaps better than any other. On nights of good seeing, my total RMS guide error is <0.4" and I have taken 2 hour long subs with resulting FWHM of <2" at focal length of 2350mm. I was more concerned about the RA drift because of the possibility of losing a guide star during prolonged periods of cloud cover. But the newest StarGo firmware addresses this with a real time automated RA tracking adjustment based on guide pulses.

Regarding the elasticity / wind issue, does anyone (Beeko?) know what was actually done to address this, and is it an adjustment available to owners of older mounts?

Derek

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I agree that the raw PE is not a useful value. My Tak EM200 had an excellent raw PE but didn't guide as consistently as the Avalon. WHat I'm interested in is what I get under guiding.

Olly

 

 

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Just on the comments about support issues for US mounts, I have a preloved AP900 permanently setup and a preloved first run 10 year old AP Mach1 as my portable setup and they just work. I redo PEC every 6 months or so and don't touch them other than basic maintenance.

 In 5 years of forum browsing I don't recall seeing many posts, if any at all, about people needing to ship AP mounts back to the US from overseas .

Support from the team in the US is excellent and you just don't seem to come across reliability issues.

re polar alignment, there is a simple daytime polar alignment routine in the AP manual I use which might work for you with a tweak using Pempro later or phd.

I cant comment on the Avalon but clearly  am an AP fanboy but they really are just set and forget.

 

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19 minutes ago, Djt said:

Just on the comments about support issues for US mounts.......

My comments about stuff coming from over the pond is not based on AP mounts or their customer service, but the issues that I have certainly had with customs here in Spain with stuff that has been sent to me directly from the US. It has included the need for import licences and embargos on my bank account...... So I don't buy from the US if I can help of it for anything. While my situation may be more extreme in Spain than in the UK, I still believe that it is worth considering in the grand scheme of things when we look at all the factors for buying :) 

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Wow, Sara. Sounded tough and to your point very much worth consideration. I was more thinking about the post re paramount issues rather than import issues given that the op was comparing AP to Avalon but fair point

 

 

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On 14/04/2017 at 15:08, Beeko said:

Please clarify your experience in using the Avalon mount in windy conditions. Having used mine in recent windy conditions (>15mph plus gusts) the below represents a snap shot of my guide graph. The subs were pin sharp. 

IMG_0825.thumb.PNG.e7e3c7982ddd511ac1a980a637903343.PNG

I have to say, for all that people rave over the Avalon mount, I was expecting a flatter guide trace than that. I can regularly get 0.8" RMS guide error on my AZ EQ6GT with poor polar alignment. 

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3 hours ago, frugal said:

I have to say, for all that people rave over the Avalon mount, I was expecting a flatter guide trace than that. I can regularly get 0.8" RMS guide error on my AZ EQ6GT with poor polar alignment. 

A guide trace is just that and nothing more. I think we rely too much on numbers. There are many other mount related issues that affect the end result. The FWHM and eccentricity of your stars in your subs are what really matters. Like I said, these mounts are unique and numbers used to compare other mounts IMO don't apply here. Again, while I often get < 0.4" total RMS, even when my guide trace looks like a polygraph with RMS well over 1" the stars are still impossible round and tight. I think I remember Olly suggesting it here, that the the belts promote such rapid response to guide pulses, that perhaps the star spends more time on pixel. I've seen folks with superb guide numbers on different mounts that still have fat egg shaped stars. I've not had a fat egg shaped star in two years.

Derek

Edited by schmeah
Compulsiveness
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21 hours ago, Beeko said:

Olly and Sara have older versions of the mount, not the recently revised model which has had a revision to sort elasticity, hence my guide graph. 

Can this upgrade be retrofitted by the user?

Not to argue, just curious about all good mounts out there.

/Jesper

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7 hours ago, frugal said:

I have to say, for all that people rave over the Avalon mount, I was expecting a flatter guide trace than that. I can regularly get 0.8" RMS guide error on my AZ EQ6GT with poor polar alignment. 

I should also add for context the mount alignment was sloppy and this was my second time at guiding the mount. I was posting this merely to show it was coping well in windy conditions with gusts. Stars as said were pin sharp (happy to post an image when I'm next on my pic for clarity). Hoping to get some answers direct from Avalon as to what has been done to reduce elasticity but without a shadow of a doubt, I was told something and my mount only moves under very heavy tugging. 

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5 hours ago, Beeko said:

I should also add for context the mount alignment was sloppy and this was my second time at guiding the mount. I was posting this merely to show it was coping well in windy conditions with gusts. Stars as said were pin sharp (happy to post an image when I'm next on my pic for clarity). Hoping to get some answers direct from Avalon as to what has been done to reduce elasticity but without a shadow of a doubt, I was told something and my mount only moves under very heavy tugging. 

Thanks for the clarification. I would be interested in seeing what the guiding looks like after you have dialled the mount in well.

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6 hours ago, frugal said:

Thanks for the clarification. I would be interested in seeing what the guiding looks like after you have dialled the mount in well.

Here's a guide graph example that I would regularly get with the Linear

guide_guide_settings_1.jpg

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Heard back from Luciano, they are using a more rigid version of the belt but there have been no differences to the mechanics of the mount. 

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