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Big problems with an lx6 10" f6.3..... Solved


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#1 Beta.Capricorni

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Posted 31 March 2016 - 01:26 PM

Dear all,
For few dollars (530) i bought an old lx6 10" f6.3 with fork and case. On the first light something gone wrong.... Bad star test, impossible to have a good collimation so i gave it to an italian famous optical and mechanical technician ( i'm italian) this is what he found:

https://drive.google...w?usp=drive_web

secondary mirror was cutted awry (3 millimeters difference) !

https://drive.google...FJ2dkpaQ1k/view

https://drive.google...XhKMXJYMkU/view


then, primary hole is not perfectly centered, is 1 millimeter out

https://drive.google...ZnN2dG9XanZYOE0


So Davide ( the technician ) made this upgrades

https://drive.google...E&usp=drive_web

There is a technical report in italian, here the translation

technical assistance to the Customer Service
Technical report
Dear Customer,
we proceeded to run on 10-inch Meade telescope delivered at this service center changes and optimization tasks that required us.
Attached to this report you will find a CD with some images related to these transactions.
The telescope showed an initial optical test control imperfect picture of diffraction zones with different lighting, and a lot of scattered light, even after careful collimation.
Disassembled the instrument, it revealed many imperfect adjustments and a serious construction defect.
Reasons for the observed non-compliance were identified in the following aspects:
1) causes related to production mode:
- Hole in the primary mirror runs eccentrically with respect to the geometric center.
- Hole of the correction plate runs eccentrically with respect to the geometric center.
- The secondary mirror cell adapted to the configuration f / 6.3 to inadequate function.
- Free opening of the reduced entrance pupil in mm. 245 due to the protrusion of the rubber gasket of the front plate.
2) the serious construction defect lies in the basis of the secondary mirror cut crooked to the optical axis. As you can see in the videos related to the secondary mirror controls, the support element tilted in return led to a noticeable flicker of reflected images.



To avoid a rework of the mirror base has introduced a correction to the centering level of its support, in order to ensure a perfect coplanarity of the axes of the two mirrors.
3) causes related to the assembly mode at the factory:
- Eccentric positioning of the secondary mirror on its support.
- Decentralized positioning of the sheet within the own cell.
- Decentralized positioning of the secondary mirror assembly inside the slab.
- Tightening of the restraint of the primary mirror flange performed with insufficient torque.
4) were due to the deterioration due to use and age of the instrument:
- Lubrication of the sliding sleeve of the primary mirror group oxidized and dried.
- Presence of some scratches on the outer surface of the correction plate, attributable to improper cleaning of the plate.
To detect defects and optimize the development of the instrument, the following checks have been carried out:
1) Complete assembly of the optics of the telescope.
2) Control of the cylindrical geometry of the optical tube.
3) Check with dial gauge of the primary mirror centered with respect to its support tube. decentralization error measured: 103/100 mm.
4) Check with dial gauge the centering of the primary mirror hole. decentralization error measured: 115/100 mm.
5) Check with dial gauge the centering of the secondary mirror assembly inside the correction plate. decentralization error measured: 184/100 mm.
6) Check with dial gauge the centering of the correction plate hole. decentralization error measured: 28/100 mm.
7) Check with dial gauge of the secondary mirror centered on its support. decentralization error measured: 43/100 mm.
To optimize the optical and mechanical alignment of the telescope, the following interventions were operated.
1) Realization from the lathe and full of a new cell in anticorodal aluminum cockpit for the secondary mirror, with a diameter calculated so as to cancel the eccentricity of the hole of the plate and thicknesses such as to eliminate any possible bending.
2) Production of sockets for the internal ventilation of the optical tube on the new cell body, with additional lightening functions.
3) Building on the lathe of a front cap brass to the inside of the cockpit, with hermetic closing functions of the intake of internal ventilation.
4) Construction of a new support for the secondary mirror of greater thickness, aluminum. New concept of suspension with a stainless steel ball central and three classic collimation registers with stems from 5 millimeters in diameter.
5) Detachment of the secondary mirror by cutting the rear glue, cleaning solvent on the contact surfaces.
6) Repositioning and reincollaggio the secondary mirror on its support with installation of the lathe spindle and tailstock of the components.
7) Removing the lathe of the primary mirror from its support.
8) Separation of the primary mirror from its sealing ring silicone, eliminating all traces of sealant employed by the base of the mirror.
9) Flattening of the metal support with locking ring function of the primary mirror.
10) for turning Reduction of support tube of the primary mirror, to enable you to operate a perfect axial centering. eliminated Thickness: 200/100 mm.
11) Realization on the lathe of a new abutment polypropylene for the primary mirror, characterized by the major surface of insistence, plasticity of adaptation, non-slip surface, large thermal inertia.
12) Centering a dial gauge of the primary mirror on its support with respect of references for the angular orientation.
13) Sealing anti-shake of the primary mirror on its support with liquid silicone injection into the game lunula.
14) Tightening the locking nuts of the primary mirror with reduced torque.
15) inner lining of the tube with anti-reflective velvetine notch.
16) Trimming of the stop plate gasket.
17) Indoor Matting of the front cell.
18) The degreasing and washing the slide tube of the primary mirror group.
19) Lubrication with synthetic heat-stable emulsion (fat graphite with pure silicone oil) of the sliding of the primary mirror group head.
20) Dry complete primary mirror group, rinsing, blowing, drying, polishing, and control.
21) Replacement of the primary mirror and applying the safety catch group.
22) Control of the startup group in focus, registration, lubrication and replacement.
23) Construction of a new oversized seal with molybdenum disulphide between the plate and the cell of the secondary mirror.
24) Installation of the secondary mirror assembly inside the correction plate.
25) Centering a dial gauge of the secondary group, system lock.
26) Wash the plate full and the secondary mirror, rinsing, blowing, drying and polishing.
27) Installation of the slab inside the cell, centering with feelers ratings, application of 3 orders of new shim thicknesses.
28) Assembly with limited torque of the retaining ring of the plate.
29) Collimation end of the telescope 250, 500 and 800 magnifications with real point light source. The centric appear now very well defined, with well circular rings and opposed, uniformly illuminated and separated, without diffused light and with a good symmetry in the intra and in extrafocal.
30) Drafting of this report.
The following table summarizes the values ​​concerning the structure of the telescope before and after its development.

Type of inspection carried Measured error
before the measured error
after the intervention factor optimization
Centering of the secondary mirror assembly inside the plate 184/100 mm 4/100 mm 46 times
better
Centering the secondary mirror on its metal support 43/100 mm 12/100 mm 3.5 times
better
Eccentricity of the hole of the plate with respect to the true 28/100 mm geometric center - virtually
canceled
Eccentricity of the hole in the primary mirror to the true geometric center 115/100 mm - virtually
canceled
Centering of the primary mirror on its support tube 103/100 mm 16/100 mm 6.4 times
better
Centering of the corrector plate to the geometric center of its cell 220/100 mm 2/100 mm 110 times better
Angular divergence between the present findings on the secondary cell, and on the edge of the plate 12 ° 0 ° -
In the CD attached to these lines are short videos relating to the tests performed.
Video # 1: decentraggio original primary mirror on your support.
Video number 2: centering the primary mirror on your support.
Video number 3: eccentricity of the center hole of the primary mirror.
Video number 4: eccentricity of the central hole of the front plate correction.
Video number 5: centering of the secondary group inside the slab.
Video number 6 and number 7 videos: controls on the wheel on the secondary mirror.
In the hope that the work carried out to meet his expectations, thanking we send sincere cordiality.
The technician
Davide Dal Prato Brembate di Sopra, 03/18/2016

Meade LX6 10" f6.3, Meade 102ed EMC f9, Achro Skywatcher 150/1200 f8, Achro Skywatcher 150/750 f5, Achro Konus Rigel 80/1200 f15, Achro Skywatcher 80/400 f5, Achro Dai-Ichi Kogaku 50/800 f16, Newton Skywatcher 200/1000 f5, Mak 90 Skywatcher


#2 MistrBadgr

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Posted 31 March 2016 - 03:42 PM

Thanks, good information!  This reminds me of the one old SCT scope that I have worked on.  From what I gather, in those days, they put things off center a bit on purpose.  They could then rotate them various parts around until they got the right collimation.  At least that is what I THINK they did.  The older scopes had marks on the edges of the corrector plate at least to indicate how it was supposed to be positioned, at least in terms of rotation.

 

By the way, welcome to the forum!

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 Beta.Capricorni

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Posted 31 March 2016 - 10:05 PM

Thank you so much Bill!

unfortunately mine is an unlucky copy..... The plate is marked for rotation and it's ok but the marks on the edge of the plate who needs to know which side of the plate had to go outside and which inside the OTA was done reversed so Davide (the technician) mounted the plate reversed..... probably when in Meade they realized that the mark was reversed they have mounted the plate right without fixing the mark, but now it's all ok

An information about the mirrors..... are they spherical both? i mean Davide reassembling the scope has repositioned the primary mirror in the same position ( so the plate has te same position before upgrading ) but secondary mirror has no marks or indication for how reposition its towards the primary, but if are spherical both i think that the secondary position it's not important. am i wrong?


Meade LX6 10" f6.3, Meade 102ed EMC f9, Achro Skywatcher 150/1200 f8, Achro Skywatcher 150/750 f5, Achro Konus Rigel 80/1200 f15, Achro Skywatcher 80/400 f5, Achro Dai-Ichi Kogaku 50/800 f16, Newton Skywatcher 200/1000 f5, Mak 90 Skywatcher


#4 MistrBadgr

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Posted 01 April 2016 - 05:49 PM

I think the secondary mirror is going to be symmetrical at least.  Most likely, it is spherical, but then I am not an expert on the internals of an SCT.   The corrector plate is a fairly contorted figure from what I have been told, but I have no idea exactly what it is.

 

I backed off on the one I was working on when I was told that to truly get it right from scratch, I really needed a special alignment tool that cost around $400.  I did the best I could by rotating the corrector plate one bolt hole at a time, then re-collimated the scope.  I had a lot of trouble remembering from one move to the next if the new position was better or worse than the last one.  I eventually got it close enough for general use, but told the people they needed to take it to someone who really knew what they were doing, which would cost them money instead of the free work they were getting out of me.

 

It sounds like the person working on your scope really knows what he is doing and you should end up with a nice instrument.

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#5 Beta.Capricorni

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Posted 01 April 2016 - 11:34 PM

A 400$ tool? What kind of tool is? In my opinion the better is an optical bench and a lot of patience.... You've done right, As you said to rotate the plate 5/10 degrees at time then recollimate it's the better way but marking step by step with pencil taking a pic for every position and at the end, looking the pics have to choose the better position. All this only if the secondary mirror position does not matter as i hope..... I it'matters i'm in trouble...

Meade LX6 10" f6.3, Meade 102ed EMC f9, Achro Skywatcher 150/1200 f8, Achro Skywatcher 150/750 f5, Achro Konus Rigel 80/1200 f15, Achro Skywatcher 80/400 f5, Achro Dai-Ichi Kogaku 50/800 f16, Newton Skywatcher 200/1000 f5, Mak 90 Skywatcher


#6 MistrBadgr

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Posted 02 April 2016 - 03:47 PM

I think the tool did something like shoot laser beams in from a significant number of different places.  When they all coincided at the same spot, then the scope was collimated.  Someone in the business of doing that every few days would be who would buy that kind of thing.  They could get a good collimation in just a few minutes.  However, that was out of my range for a tool I would probably only use once.

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#7 Beta.Capricorni

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Posted 03 April 2016 - 03:17 AM

Oh i know, it's the Holotec collimator, but i thought was only for collimation.

Meade LX6 10" f6.3, Meade 102ed EMC f9, Achro Skywatcher 150/1200 f8, Achro Skywatcher 150/750 f5, Achro Konus Rigel 80/1200 f15, Achro Skywatcher 80/400 f5, Achro Dai-Ichi Kogaku 50/800 f16, Newton Skywatcher 200/1000 f5, Mak 90 Skywatcher


#8 MistrBadgr

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Posted 03 April 2016 - 06:07 PM

I think that is basically what you are doing in this instance, except that you have another degree of freedom with the movement of the corrector plate.

 

Bill


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#9 Beta.Capricorni

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Posted 04 April 2016 - 01:41 AM

ah, ok thank you so much!


Meade LX6 10" f6.3, Meade 102ed EMC f9, Achro Skywatcher 150/1200 f8, Achro Skywatcher 150/750 f5, Achro Konus Rigel 80/1200 f15, Achro Skywatcher 80/400 f5, Achro Dai-Ichi Kogaku 50/800 f16, Newton Skywatcher 200/1000 f5, Mak 90 Skywatcher





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