Avalon Linear Mount & Wind

[psledlie]

Hello,

I'm in the market to upgrade my old Losmandy mount to a newer GOTO mount, and am looking at the Avalon Linear Fast Reverse. Oliver Penrice has given me some great info on his experience with it in his observatory, but I was wondering if I could hear from those who use it in the field. I'm concerned about the wind issue, which may not be a big deal with my small refactor. Usually, it's fairly calm at night around here  (Colorado, U.S.A.) but we can get winds from 5-10 mph. I'm not opposed to buying an observing tent if necessary, though hopefully I won't have to.

Equipment : Borg 77 & mini guidescope

                    Astro-Physics 102mm f/8 refractor

Thanks for any input on this,

Peter Ledlie

[ChrisLX200]

An interesting question, but in truth I doubt anything more than a general recommendation is possible. If your Losmandy mount (G11?) was anything like mine then it didn't like operating in any kind of wind much - a steady 5mph would be OK but 10mph no, and gusty winds a definite no-no because it would flop about even with a medium length 5" refractor tube. I would think all mounts within a given weight 'class' the results would be similar. Which leads to the question: What would make a difference to resistance to wind disruption?

For sure, the best solution is a windbreak of some sort which solves the problem at source and that really has to be the best way forward. Beyond that, heavy mass I suppose and 'stiff' construction (close-tolerance bearings, no slop anywhere). Thinking about it, my 10-Micron mount has absolute encoders which it uses as part of the drive system as feedback for regulating tracking, any slight tracking error induced by a gust of wind should (in theory) be instantly corrected. This sort of behaviour used to send my G11 nuts when using an autoguider but I don't need to guide the 10-Micron and I have used this mount successfully in a 10mph wind but I've not tried in anything stronger than that.

ChrisH

[psledlie]

An interesting question, but in truth I doubt anything more than a general recommendation is possible. If your Losmandy mount (G11?) was anything like mine then it didn't like operating in any kind of wind much - a steady 5mph would be OK but 10mph no, and gusty winds a definite no-no because it would flop about even with a medium length 5" refractor tube. I would think all mounts within a given weight 'class' the results would be similar. Which leads to the question: What would make a difference to resistance to wind disruption?

For sure, the best solution is a windbreak of some sort which solves the problem at source and that really has to be the best way forward. Beyond that, heavy mass I suppose and 'stiff' construction (close-tolerance bearings, no slop anywhere). Thinking about it, my 10-Micron mount has absolute encoders which it uses as part of the drive system as feedback for regulating tracking, any slight tracking error induced by a gust of wind should (in theory) be instantly corrected. This sort of behaviour used to send my G11 nuts when using an autoguider but I don't need to guide the 10-Micron and I have used this mount successfully in a 10mph wind but I've not tried in anything stronger than that.

ChrisH

Chris,

Yes, my GM100 doesn't like to guide in the wind either! I had heard that because it uses belts and pulleys, the Linear mount was more prone to being "deflected" in the wind, than a standard worm gear mount. The GM100 PE is enough of a problem for PHD, and doesn't need wind to make it even worse. ;-) I agree that some sort of a portable wind break would solve the problem, as long as it's not too much of a hassle to set up. Most of the time, wind is not a problem at either one of my dark sky sites, and if I do see that it's going to be windy, I won't go out anyway.

That 10 Micron mount must be a dream compared to your G-11! I wish I could afford one of those, but I think I'm going to be quite happy with the Linear and it's smooth PE.

Thanks,

Peter

[Rob63]

I have not heard any issues regarding wind with the Linear fast reverse as its a "normal" style GEM type mount, are you getting confused with the M-Uno and M-Zero "single fork" type mounts?

There was a good (but old) post at http://stargazerslounge.com/topic/191410-avalon-linear-fast-reverse-equatorial-mounting-anyone-using-this-mount/?hl=%2Bavalon+%2Blinear

Rob/

[schmeah]

This thread on CN raised the hypothetical concern of belt drives in general and wind stability. I don't buy it, and haven't seen other Avalon owners complaining.

http://www.cloudynights.com/topic/372925-avalon-muno-neaf/

My M Uno fares as well in the wind as I would expect others to  in that class and weight t. I don't image in strong gusts or steady wind greater than 10 MPH anyway, due to generally poor seeing conditions.

Derek

[ollypenrice]

I have not heard any issues regarding wind with the Linear fast reverse as its a "normal" style GEM type mount, are you getting confused with the M-Uno and M-Zero "single fork" type mounts?

There was a good (but old) post at http://stargazerslounge.com/topic/191410-avalon-linear-fast-reverse-equatorial-mounting-anyone-using-this-mount/?hl=%2Bavalon+%2Blinear

Rob/

No, it's not really 'normal' in that it is belt driven and the belts drive is elastic. I have one, like it and have presented plenty of images from it using a TEC140. Sara is another user. But the belt drive simply is elastic. Is this an issue? Well, I can't walk past it without my movement being recorded in the guide trace. (For comparison I can manually focus one of the two scopes carried by our Mesu without this handling of one scope being recorded in the guide trace or affecting the image of the other.) But, then again, the odd spike in the Avalon guide trace seems not to affect the image. I thnk that, if it is easily deflected, it is also extemely quick to come back to the correct position and this also matters.

If I wanted to image in the wind would the Avalon be my first choice? No.

Do I regret buying my Avalon? No.

A couple of images from the Avalon/TEC140...

https://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-XqpRhfL/A

https://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-kNjFmJW/A

Olly

[psledlie]

This thread on CN raised the hypothetical concern of belt drives in general and wind stability. I don't buy it, and haven't seen other Avalon owners complaining.

http://www.cloudynights.com/topic/372925-avalon-muno-neaf/

My M Uno fares as well in the wind as I would expect others to  in that class and weight t. I don't image in strong gusts or steady wind greater than 10 MPH anyway, due to generally poor seeing conditions.

Derek

Derek,

Thank you for your reply. It's good to hear from someone who has used it in the field. I think I have been unnecessarily worried about it's performance in light breezy conditions. Like you, if it's windy out, I won't take my scope out anyway, so it seems that I've been chasing a non- issue. Compared to the seismograph PE I currently deal with on my Losmandy GM100, I have a feeling that I'll be quite happy with the Linear. :-)

[psledlie]

No, it's not really 'normal' in that it is belt driven and the belts drive is elastic. I have one, like it and have presented plenty of images from it using a TEC140. Sara is another user. But the belt drive simply is elastic. Is this an issue? Well, I can't walk past it without my movement being recorded in the guide trace. (For comparison I can manually focus one of the two scopes carried by our Mesu without this handling of one scope being recorded in the guide trace or affecting the image of the other.) But, then again, the odd spike in the Avalon guide trace seems not to affect the image. I thnk that, if it is easily deflected, it is also extemely quick to come back to the correct position and this also matters.

If I wanted to image in the wind would the Avalon be my first choice? No.

Do I regret buying my Avalon? No.

A couple of images from the Avalon/TEC140...

https://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-XqpRhfL/A

https://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-kNjFmJW/A

Olly

Olly,

Thanks again for your take on this. As I said to Derek, it looks like my worries about this mount, really aren't substantiated. As long as I image in calm to light breeze conditions, I'll be fine.  Luciano also mentioned the ability of the mount to quickly come back to the correct position as you stated. I think the worst part of this enterprise will be trying to sell my GM100 on the used market in a world of GOTO mounts. The service issue of the Linear being made in Italy, and my living here in the US doesn't bother me. 

[famax]

If i had not my 10micron i would have buy an avalon mount.

In this range,they are  the best quality for use in the field.

[swag72]

The LInear is a great mount - I haven't replied to this thread as you specifically said about wind and being portable - I know nothing about being portable with this mount as it's firmly in my observatory!

In a light breeze I have found that the guide graph deteriorates but that the exposures are still more than fine to use. The Linear is an excellent mount that in my opinion punches well above it's weight. The guiding accuracy that I see on mine is equivalent to that of the Paramounts that my friends have...... That is good in my book.

[ollypenrice]

The LInear is a great mount - I haven't replied to this thread as you specifically said about wind and being portable - I know nothing about being portable with this mount as it's firmly in my observatory!

In a light breeze I have found that the guide graph deteriorates but that the exposures are still more than fine to use. The Linear is an excellent mount that in my opinion punches well above it's weight. The guiding accuracy that I see on mine is equivalent to that of the Paramounts that my friends have...... That is good in my book.

Agreed. Mine is often the same as I achieve in the Mesu but not always quite as good. Needing shorter guide subs the Avalon sometimes chases the seeing more than the Mesu, which can use 4 or 5 second guide subs to let the seeing average out.

Regarding field use, we really do need to pester the manufacturers to use the polar alignment routine found on Takahashi mounts and on the Vixen Atlux. I can polar align a Tak well enough to do 30 minute subs in about 2 minutes. Why this is not the industry standard system is beyond me.

Olly

[swag72]

I know that Avalon are working on a Polar Aligment routine and pointing model for a software release.

I have also started using longer guide subs.... Now use 3s.... No adverse results as far as I can see.

[ollypenrice]

I know that Avalon are working on a Polar Aligment routine and pointing model for a software release.

I have also started using longer guide subs.... Now use 3s.... No adverse results as far as I can see.

Interesting. Mine doesn't thrive on long subs. I wonder why the difference? We'll probably never know when technology is working so close ti its limit.

Olly

[StuartJPP]

 Regarding field use, we really do need to pester the manufacturers to use the polar alignment routine found on Takahashi mounts and on the Vixen Atlux. I can polar align a Tak well enough to do 30 minute subs in about 2 minutes. Why this is not the industry standard system is beyond me.

 Olly

What method is this Olly?

[ollypenrice]

What method is this Olly?

Hi Stuart,

Firstly, no tripod levelling. Just put it down as it is and that's that.

On the main housing which rotates in RA there are two things: a small offset scale and a rotatable ring which you set to your time zone east or west of the meridian. On the ring is a bubble level. Once set to your time zone you leave it alone.

You point roughly north at a reasonable estimation of your latitude so Polaris won't be too far out.

You then rotate the RA housing to centre the bubble in the level and then lock the clutch. This locates the polar reticle with the time clock face in the right orientation. It takes three seconds, max.

Look through the polar scope. Here you see, in effect, a planisphere which you turn so that the date on one part aligns with the time on the other. (I can't remember which is the fixed one and which rotates but it doesn't matter, you just make the current time and date line up.

This puts a little slot-shaped 'Polaris box' reticle in the right place and you tweak the adjusters to put Polaris in there. (The slot covers a 30 year spell, from memory, and you estimate where in the slot to put it. I guess 2015 would be half way along it. It's not a long slot and an estimate is enough.

You are very likely indeed to have a Tak mount polar aligned in the time it takes to level a tripod (which you don't do on the Tak.) This system is so good that I'm exasperated by it's rarity!

Olly

[StuartJPP]

Thanks Olly, interesting...

The AstroTrac uses a reticule similar to the Losmandy polar scope. I am not sure if you are familiar with it, but it uses 2 additional alignment stars along with the gap for Polaris. It also has constellation markers (Ursa Major and /Cassiopeia) but these just gives you an idea of where to point things...This scope requires no leveling of the mount or setting times or dates although you need to be able to see the two other alignment stars, however I can see them even from my light polluted garden.

I wonder how this equates to the one you describe above...mine also only takes a couple of minutes to align. In fact I have made an adapter for this polar scope for use with my Avalon M-Zero as I prefer it to the Skywatcher style that it was supplied with (I bought it second hand and the original owner chose the Skywatcher style but you can optionally get it with the Losmandy style).

Sorry about hijacking the thread! However I use an Avalon M-Zero and it uses a similar belt drive, it obviously moves about in the wind but it does recover fast...much better than the iOptron ZEQ25-GT mount I had previously. However if it is windy I don't image anyway unless I am in a sheltered area.

[opticalpath]

Just on the side issue of wind-breaks ...... I've often heard it said that a wind 'filter' can be more effective than a wind break.  Wind hitting a solid barrier presumably creates turbulence that can spill over.  Something like a fine mesh filter breaks up and slows the flow.

I hasten to add that I haven't tried this!  But if I was in an exposed position, I would try making a 'fence' out of fine-mesh garden fabric first.  It's lighter and cheaper than a solid break, and much less prone to blowing over and into your scope!

Adrian