Best Mount for Imaging (£5k-£6k Budget)

[ribuck]

Ah yes not much use. I think per said that the 10micron stuff uses renishaw encoders and they have about 10million ticks. Per is this about right ?

[ribuck]

Jeff,

Excellent service from Lucas, he just replied with the current standard encoder details.

Standard are encoders mounted direct on the axis with 2.16 arc minute resolution.

On the motor are encoders with a resolution of 0.162 arc seconds.

[jjongmans]

That would be 10k ticks.

[jjongmans]

For comparison; the ASA has mount encoders with a resolution of 0.03"

[ribuck]

I think the eq8 has about the same as the mesu

[ribuck]

Well that's the dream of a big payload and unguided images out the window. Lucas said the the renishaws are well over £1000 each so blows the budget.

Looks like it's definitely the GM1000HPS then.

[Jessun]

Looks like it's definitely the GM1000HPS then.

Well, you sure have done your research!

/Jesper

[jjongmans]

Too bad. Look at the bright side; the GM1000 is an awesome mount, it won't let you donw!

[ribuck]

I would just like to thank everyone who has contributed to this thread. Apologies that it's been a little long winded but at least we got got there in the end and I've got a clear idea of what I want now.

I really appreciate all the help in this thread.

Rich

[perfrej]

Long? In what way?

I've had fun anyway, but you're right - maybe we should let it go

/per

[ribuck]

Well I think I may have digressed once or twice , but I have to say it was a fun topic to debate and I really enjoyed this thread.

[ribuck]

Per, when you get your mount it's probably best to start a fresh thread to give it the proper focus it deserves.

[perfrej]

Wilco

[ribuck]

Sorry chaps, just one last update from Lucas, which is interesting, and I wouldn't mind your thoughts on the subject. Note that Lucas is saying the encoder used are 8-million ticks.

Hi Richard,

Thanks for your mail.

Maybe I can give some advice for you and the forum that can help.

You can do unguided imaging with the hi resolution motor encoder on the standard Mesu-Mount for the budget you have.

It has a resolution of 0.162 arc sec (8000000 tics) which is very high and much better than the seeing your looking trough.

If someone wants hi resolution encoders direct on the axis I build them in because the mount is prepared for that.

I that case the best solution is the Renishaw system because it is robust and reliable and has good specifications.

It’s also possible to do that any time afterwards as an upgrade.

You have the cost for the shipment of the mount and the encoders afterwards in that case.

Unguided imaging has some disadvantages over guided imaging.

You can’t correct for random failures when you do unguided imaging with any mount.

A random failure for example is a mirror flop or another movement that’s not behaving linear.

I measured them and I know that even in the best telescopes available they are present in orders that are 10X bigger than the motor encoder resolution of 0.162 arc sec.

When you use an off-axis auto guider you correct for all those failures and you don’t need the very expensive encoders.

You use the stars in the sky for free as the best encoders available in that case and your price/performance is the best you can get.

On the other hand when you want to do unguided imaging because you do remote operation and you don’t want to do the auto guiding because you think it’s too complicated.

Then the Mesu-Mount with the Sitech controller is very well equipped to do that.

The software that comes with the Sitech can make a pointing model to calculate and compensate for all reproducible errors that are in the system.

Elasticity in your tube, a polar misalignment, a cone error an much more.

Let me know if you have further question please.

Regards,

Lucas Mesu

www.mesu-optics.nl

[ribuck]

So is there anyone out there with a Mesu using a sitech controller that has tried unguided imaging ?

[Jessun]

I can see a spinoff thread coming up on the subject of absolute encoders....

Pros and cons are easy to list though. They're great but cost a bundle.

The question is how much it's worth to drop the guide gadgets...

At present I'll resist. I'm not remote and setup and align everytime, so for me I'd just get a bunch of new obstacles in getting to grips with pointong models etc. Can the Mesu be retro fitted by the user?

/Jesper

[perfrej]

I don't think guiding per se is bad. It is, however, unbelievebly cool to run unguided

It is also one less gadget that can go wrong. Also, the only totally hassle-free guiding solution is PHD, which cannot be properly automated. Maxim is a constant struggle I think.

So, I prefer the totally cool solution of not guiding

/p

[jjongmans]

My mount is designed for unguided operation, and I can achieve 30 min. unguided subs without any problem. But I'm still using an autoguider, just in case... I never see a correction, so it's also unguided I guess.

It's not that hard to achieve unguided performance in a single test, it becomes more critical when you want to have unguided performance 365 days a year over the full sky and pinpoint stars in every sub.

I don't have any problems with Maxim and guiding (controller with CCDAP). It's also the only way to go in an automated setup.

[ribuck]

Hi all, I emailed Lucas again and asked if he knew if any of his customer were imaging unguided with the Mesu 200, and he shed more light on the whole mesu unguided debate, apart from the fact that he really needs to update his web site .

I have to admit, i did find it hard to completely understand his reply but what i did take from it, was that unguided imaging is possible, and that the PE graph was done unguided on a prototype mount and for 1620 seconds.

So i really need to see an example of this from a production mount, using sitech controller.

Hi Richard,

Yes, I have.

He came to the conclusion that his long focal mirror was moving when he did long time exposures (as all mirrors do).

I did a lot of unguided measurements myself to test complete setups.

The PE graph on the mesu-optics website is an example of an unguided exposure of 1620 seconds.

It is made with the first proto mount and a telescope that was prepared to prevent elasticity as much as possible.

In the graph seeing effects and rest elasticity are included.

Later produced mounts were measured by users and gave much better PE graphs because these mounts are CNC produced.

With shorter exposure times and shorter focal lengths it is much easier to do unguided imaging.

With 2 meter focal length and ½ hour exposure time it is hard to do. Problems built up exponential with increasing focal length and resolution.

With of-axis auto guiding it is easy to do.

The reason I try to explain this is that the Mesu-200 has a lode capacity in the range of long focal heavy mirror telescopes.

With a short focal length and a fast focal ratio telescope it is possible to do unguided imaging with the standard Mesu-200.

Regards,

Lucas Mesu

[Pig]

You can have mine for that kind of cash

[ncjunk]

You've pulled together some interesting info here.

With my mesu I am torn between waiting to see if the servocat argo navis software updates enable decent pc control or just upgrading to a sitech.

I think i may add a sitech sometime this year as the software looks good (i like the complexity...means I have more options rather than just the goto i have now...to park perchance to dream..)

[ribuck]

I think the sitech controller is fairly reasonable price, think I read 250 dollars somewhere

[ncjunk]

I saw two versions on their website and just assumed it would be the more expensive $850 version that i'd need....must read the manual

[ollypenrice]

Stepping back a bit, Tim finds his mount ultra sensitive to balance but Per says his will run either side of the meridian without adjustment, which I suppose would not conflict with Tim's experience if Per's balance were absolutely perfect. (And knowing Per this is possible! ) However, if I wanted to piggyback a DSLR with 200mm lens on the ODK14/Mesu I'd just bolt it on. There would be absolutely no need whatever to rebalance.

It couldn't care less about fine balance.

The Mesu looks like a bag of spanners? Awe, I think it looks like a machine. Does everything have to wear high heels?

Olly

[perfrej]

Oh, but Olly, I normally do balance quite well but have run successfully with pretty poor balance as well. Balanceing the 10Micron mounts is so simple. You enter the procedure from the handset, wait a minute or two and then it tells you whether you're shaft heavy or OTA heavy (top and bottom for Dec) and by how much. One or two adjustments and you're perfectly balanced.