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Equipment Discussions >> Mounts

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ahopp
sage


Reged: 05/24/12

Re: LX850 M81 in mediocre seeing new [Re: Orionis91]
      #5744234 - 03/19/13 11:07 PM

Jason, What are you using for mount control on the LX850? I plan on getting TheSkyX Pro w/Tpoint and Camera AddOn, unless you have another recommendation that I should consider.

Tony


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jimb1001
sage
*****

Reged: 11/14/09

Loc: Florida
Re: LX850 M81 in mediocre seeing new [Re: Pak]
      #5744313 - 03/20/13 01:20 AM

You are certainly entitled to your negative opinion.
However, implying a poster is probably lying or deliberately misleading doesn't take more than one post.


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Mkofski
Pooh-Bah
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Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: LX850 M81 in mediocre seeing new [Re: jimb1001]
      #5744390 - 03/20/13 02:35 AM

Quote:

You are certainly entitled to your negative opinion.
However, implying a poster is probably lying or deliberately misleading doesn't take more than one post.




+1


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freestar8n
Post Laureate
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Reged: 10/12/07

Re: LX850 M81 in mediocre seeing new [Re: Mkofski]
      #5744509 - 03/20/13 04:52 AM

I think that if the intent is to convey that this scope/mount system is working well, then it would be much more informative to present quantitative performance metrics based on raw data rather than processed images.

This system, along with the earlier lx800, is I think unique in amateur astronomical imaging in relying on minimal flexure to image well in long exposures. When the guiding system is sold entirely separate from the main optics then it is up to the user to use OAG or an add-on guidescope - and to keep the flexure to a minimum. But in an integrated system the flexure is built in - and becomes an important specification that can be quantified in arc-seconds per minute.

I have battled flexure with sct's and consider it a key problem, along with centroid accuracy, that limits the results people get with reflective optics in long exposures - and I offer unique features in MetaGuide to allow the direct measurement of flexure in different parts of the sky so it can be quantified and methodically reduced.

Although people focus on the primary mirror as the culprit, an sct with its long focal length and magnifying secondary can have many sources of internal flexure, including even some distortion of the corrector plate holding the secondary.

The impact of flexure depends on the length of the exposure and the size of the stars in the image. For 4" fwhm and 5m exposures, they would start to look oblong at perhaps a flexure rate of 0.2" per minute - which is achievable. But for 2" fwhm in 10 minutes, it would be more like 0.04" per minute and that is much harder.

Regarding the "guiding accuracy" it is stated at something like "1 arc second." I'm not sure how that relates to the achievable fwhm. For example - if a skilled person with an expensive system is getting 2" fwhm - what would this system achieve? 3"? 4"? How does "1 arc second" translate to the penalty you get in guiding compared to a system guiding at the limits of seeing?

I don't know if anyone will state values for the flexure rate - but I sure hope they are measuring it and using it as a guide to improve the mirror locks or whatever. You can get it directly from a long series of guided images as long as you don't dither and you are polar aligned well. I personally would be measuring it all over the sky since the rate can be orientation dependent.

If they do solve flexure and end up with a system that can be used at long focal length for long exposure narrow band - that's great - and I'll be very interested to see how they did it. Even rc's and cdk's with fixed primaries and expensive mechanics tend to be guided with OAG - but there are exceptions.

Frank


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Whichwayisnorth
Pooh-Bah
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Reged: 07/04/11

Loc: Southern California
Re: LX850 M81 in mediocre seeing new [Re: ahopp]
      #5745066 - 03/20/13 12:40 PM

Quote:

Jason, What are you using for mount control on the LX850? I plan on getting TheSkyX Pro w/Tpoint and Camera AddOn, unless you have another recommendation that I should consider.

Tony




Meade has had the mount in the hands of a developer working on ASCOM drivers for about a month now. I am not sure how much longer before they are released however.

That having been said I have been told quite a few times that using the generic classic lx200 ASCOM drivers should work. You won't have full functionality but you will have the basics like go-tos.

The way that Starlock works you'll have to turn off the Starlock HPP if you are going to use t-point. Which is exactly what I'll do too. I must have a bad driver install because I've not been successful at getting the aforementioned ascom driver to work with The Sky X. I came up with a work around to get me by until the official drivers are released. I'll give it another shot though once my mount arrives.


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