My mount dilemma

[codemonkey (Lee)]

0.92" RMS guiding is pretty poor imo. If it was peak to peak that would be what I'd consider good guiding. If I had 0.92" RMS on my EQ6 I would consider it to be behaving poorly and would have been seeking the cause so as to fix it.

With my Avalon Linear I'm usually around 0.5 - 0.6" RMS when pointing further towards dec 0, typically where RA guiding gets worse on any mount. Often the peak to peak is below my imaging scale (1.12"/px).

Now whether that "poor" guiding is truly poor all comes down to your imaging scale. For me, I know that would be doing bad things to my images. On a wide field system with lower resolution? Maybe not.

[stefang (Stefan)]

Ioptron CEM60EC. Works a treat

[Slawomir (Suavi)]

I usually get around 0.6" RMS on my AZ-EQ6 (4" doublet, 570 mm fl, 1.33 arcsec per pixel, 3 nm filters) and such performance results in slightly elongated stars. Occasionally tracking error gets as low as 0.4" RMS and then I get perfectly round nice stars. Unfortunately, sometimes tracking gets worse, and subs with more than 0.8" RMS need to be thrown out.

I have been looking at future upgrades, including SX active optics, MDA encoder and also a more expensive mount, including MYT and Mach1. If new G11 consistently performs better than my current mount, then that would be truly great news and I would be seriously interested, after collecting sufficient funds...

[strongmanmike (Michael)]

Originally Posted by codemonkey

0.92" RMS guiding is pretty poor imo. If it was peak to peak that would be what I'd consider good guiding. If I had 0.92" RMS on my EQ6 I would consider it to be behaving poorly and would have been seeking the cause so as to fix it.

With my Avalon Linear I'm usually around 0.5 - 0.6" RMS when pointing further towards dec 0, typically where RA guiding gets worse on any mount. Often the peak to peak is below my imaging scale (1.12"/px).

Now whether that "poor" guiding is truly poor all comes down to your imaging scale. For me, I know that would be doing bad things to my images. On a wide field system with lower resolution? Maybe not.

Originally Posted by Slawomir

I usually get around 0.6" RMS on my AZ-EQ6 (4" doublet, 570 mm fl, 1.33 arcsec per pixel, 3 nm filters) and such performance results in slightly elongated stars. Occasionally tracking error gets as low as 0.4" RMS and then I get perfectly round nice stars. Unfortunately, sometimes tracking gets worse, and subs with more than 0.8" RMS need to be thrown out.

I have been looking at future upgrades, including SX active optics, MDA encoder and also a more expensive mount, including MYT and Mach1. If new G11 consistently performs better than my current mount, then that would be truly great news and I would be seriously interested, after collecting sufficient funds...

We must not confuse RMS guide errors with RMS tracking errors, there is a huuuge difference.

If a mount "tracks" with RMS errors under an arc sec that's absolutely amazing...if a mount "guides" with RMS errors under an arc sec that may in fact not be good enough for many applications.

Eg. My NJP "guides" with errors of around +/- 0.3" but the total unguided "tracking" error is closer to 3 arc sec or 10X worse.

Mike

[codemonkey (Lee)]

Absolutely right, Mike. I see I might have misunderstood Peter's post, although it does make it a little harder to be sure since corrections are not being displayed on the graph. I just assumed it was a guide graph.

[Shiraz (Ray)]

Originally Posted by codemonkey

Absolutely right, Mike. I see I might have misunderstood Peter's post, although it does make it a little harder to be sure since corrections are not being displayed on the graph. I just assumed it was a guide graph.

Likewise. It is either a pretty average guide graph or an unbelievable track graph (better than a PMX?).

Losmandy makes no claims for PE or tracking on their website - I would have thought that they might put a few shekels into publicising the issue if they had managed to reduce the tracking error by a factor of 10x over what it used to be - and thereby directly challenge or surpass mounts that cost >3x as much. On that basis, the odds are that it is a guide graph, but we await Peter's clarification.

[Slawomir (Suavi)]

Originally Posted by strongmanmike

We must not confuse RMS guide errors with RMS tracking errors, there is a huuuge difference.

If a mount "tracks" with RMS errors under an arc sec that's absolutely amazing...if a mount "guides" with RMS errors under an arc sec that may in fact not be good enough for many applications.

Eg. My NJP "guides" with errors of around +/- 0.3" but the total unguided "tracking" error is closer to 3 arc sec or 10X worse.

Mike

Thank you for pointing that out Mike

I meant RMS guiding errors.

[Peter Ward]

I'll be catching up with Losmandy this weekend, and will clarify all specs when I return from the USA.

[gregbradley]

Originally Posted by Camelopardalis

Personally, I'm unimpressed seeing a guide graph that is scaled at +/- 8 arc seconds. I scale my graph at +/- 1 arc second and it's easy to be horrified by it, but I feel that just pampers to the PHD insecurity syndrome.

What's important is getting nice round stars. Wouldn't we all like beautifully engineered mounts that look as pretty as they track (sometimes prettier!), but it's seemingly such well trodden ground that a "lowly" EQ6 can do a good job with a little time and effort. Sure, there might be lemons out there, but from what I read here in IIS alone indicates that SW are not alone...

Its a nice looking graph and is showing good performance but yes it has been scaled incorrectly. Mine is scaled in 1 arc second increments and is similar but a tad worse. And that is a PME that has routinely delivered round stars fairly easily.
The wider scaling compresses the PE lines on the graph. In fact that graph looks much like my AP1600 at its best in good seeing. The best I have seen it do is .6 arc secs RMS for about 5 minutes before averaging out to .8 arc secs RMS like this graph. It can do that for quite a long time in good seeing. Usually 1 arc sec with the AP and about 2.25 with the PME is what I see as a reference point. This is using PHD2 which to me seems to be the best autoguiding software (although I haven't used Maxim).

Greg.

[gregbradley]

Originally Posted by Slawomir

I usually get around 0.6" RMS on my AZ-EQ6 (4" doublet, 570 mm fl, 1.33 arcsec per pixel, 3 nm filters) and such performance results in slightly elongated stars. Occasionally tracking error gets as low as 0.4" RMS and then I get perfectly round nice stars. Unfortunately, sometimes tracking gets worse, and subs with more than 0.8" RMS need to be thrown out.

I have been looking at future upgrades, including SX active optics, MDA encoder and also a more expensive mount, including MYT and Mach1. If new G11 consistently performs better than my current mount, then that would be truly great news and I would be seriously interested, after collecting sufficient funds...

That's been my experience over the years with some exceptions. At 3 metres using a MMOAG through the scope OAG then .6 would still give you round stars.

Greg.

[HarryD (Greg)]

Wow, mount issues seem to cause as much angst as political ones.

Anyway I decided on a new Losmandy G11G. Out of the box there is no comparison with the EQ6.

I couldn't justify the $7500 price difference to buy a Paramount MYT.

Now to set it up and see what happens.

Thanks for all your thoughts.
Greg

[Slawomir (Suavi)]

Congratulations Greg,

I am looking forward to reading your impressions with your new mount

[phomer (Paul)]

Greg,

My opinion is the G11 is well worth the money. Also, it very easy to work on and has had many updates over the years, always compatible. There is a possibility that the worm may need adjusting before it performs at its best.

Regards

Paul

[RobF (Rob)]

Yes, we'd all be interested to hear your initial and follow up opinions down the track Greg.