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Intes MK63. I don't NEED another scope!

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#51 clamchip

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Posted 20 May 2019 - 10:26 PM

Intes is still in business, I would send it back.

Robert



#52 DAVIDG

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Posted 20 May 2019 - 11:24 PM

 The image of the primary with the Ronchi lines are not with double pass but at the ROC  with a Ronchi grating With a very   fast mirror  in this case F2.8 and at a ROC you need to use a grating with many lines per inch to increase the sensitivity as in over 133 lines  but using a knife edge you have the greatest sensitivity. 

   With Double pass testing of the complete system your back to a F/10 system  so a typical 133 line grating has plenty of sensitivity to show the error. Also  with double pass  your , sending the light thru the system twice  so the errors are double vs testing at the ROC were it is single pass test.  So with the proper line count on the  grating the hole would have shown up more clearly when testing the mirror at the ROC. 

   The turned edge is most likely an under corrected edge caused by the mirror being close to a sphere. It really needs to an ellipse with F/10 Gregory design Mak. So when the primary is correctly  figured the edge  will most likely go away. 

 

                   - Dave  


Edited by DAVIDG, 21 May 2019 - 08:57 AM.


#53 rolo

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Posted 21 May 2019 - 07:17 AM

Dave, Is there a way to use the DPAC test to determine if a MakCass's optics are aspherical or aspherised? Do you know if the aspherical surface would be the primary, meniscus or secondary?



#54 bremms

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Posted 21 May 2019 - 07:23 AM

I find it enlightening that very few optics are really even close to 1/4 wavefront. I have a couple optics that are truly superb and they are a joy to use. Learned to not be disappointed and just accept most optics as so so at best. DPAC lays bare the errors. To  my eye there is a big difference between a 1/2-1/4 wave optic and a 1/8or better optic. Gone through a large number of commercial scopes and very few were really good. I was a bit spoiled as my first large scope had a custom made 10" mirror that was truly superb.  Guess I expected most scopes to be like this. Boy they were not. Big Coulters with figures better than a Cave and they were still not good. The Cave I am speaking of was an 8" F5 and it was then reworked by someone that left Cave ( same person that made my 10") and returned superb. Night and day difference between a 1/2wave mirror and a true 1/10 wave and smooth.

Unfortunately, I don't have the time or experience to rework an optic.


Edited by bremms, 21 May 2019 - 07:26 AM.

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#55 DAVIDG

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Posted 21 May 2019 - 08:57 AM

Dave, Is there a way to use the DPAC test to determine if a MakCass's optics are aspherical or aspherised? Do you know if the aspherical surface would be the primary, meniscus or secondary?

 In DPAC  if you test the whole optical system your looking at the total correction. So if a MAK would require an aspheric surface and it wasn't present or not figured correctly you would see the error in the DPAC results.  This is what we see in Tim results on his Mak.  In a Mak  that requires an aspheric surface you can put it on any of the surfaces or even break iup the total correction and put some on each surface as long as the result is that the total wave front is corrected. What is usually done is that it  is put on either the concave surface of the primary or the concave surface of the meniscus since those surfaces can be tested directly with a  Foucault test.  

   Making an aspheric is not easy so hybrid design have been made for Maks were the secondary is an independent from the meniscus. This allows the designer more freedom and can result in all spherical system.

  In  the John Gregory type Mak design ie with the secondary being a mirrored spot on the meniscus and the system is faster then about f/18 it will need an aspheric surface to totally  correct the system. This is what Cumberland does for the Questar optics and what they did for the Quantum optics.  On cheap Maks they leave them spherical or more likely how they come off the polishing machine. I have a couple of Chinese made Maks and it looks like they were trying to put the correction on the primary using some quick method of warping the primary when polishing in it. The result is a rough zoney surface that is only a gross approximating to the needed one .  Intes might have been trying to do the same with Tim's optics as well.

 

           - Dave   


Edited by DAVIDG, 21 May 2019 - 10:28 AM.

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#56 tim53

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Posted 21 May 2019 - 09:27 AM

I find it enlightening that very few optics are really even close to 1/4 wavefront. I have a couple optics that are truly superb and they are a joy to use. Learned to not be disappointed and just accept most optics as so so at best. DPAC lays bare the errors. To  my eye there is a big difference between a 1/2-1/4 wave optic and a 1/8or better optic. Gone through a large number of commercial scopes and very few were really good. I was a bit spoiled as my first large scope had a custom made 10" mirror that was truly superb.  Guess I expected most scopes to be like this. Boy they were not. Big Coulters with figures better than a Cave and they were still not good. The Cave I am speaking of was an 8" F5 and it was then reworked by someone that left Cave ( same person that made my 10") and returned superb. Night and day difference between a 1/2wave mirror and a true 1/10 wave and smooth.

Unfortunately, I don't have the time or experience to rework an optic.

I don't have the time, either.  And I've only worked 4 mirrors now.  Well, 5 if you count the gregorian secondary I haven't finished yet.  But what I found is that, after taking the mirror class with Dave 3 times now, It's not that hard.  And refiguring something like this is just plain fun.

 

With the 8" f/8 mirror I worked on recently, it truly started to behave once I decided to work back toward a sphere from the hyperbola.  The key was to test and press frequently.  When I did that, I was able to find the correct parabola on my way to a sphere in less than half an hour.  But even if I'd had to get to a sphere and correct to a parabola from there, the instructions on Stellafane's website (I also have a copy of Howard's "Standard Handbook for Telescope Making") are clear and well organized.  So I could have gotten to the parabola from a sphere in not too much time.

 

Same with this Mak.  The principles are straightforward, so I'm not worried about it being a big deal fixing this thing.  And it's so bad now, I might as well.  I can't sell it like this in good conscience, so unless I can fix it, it's going to sit in its case for another few years.

 

-Tim.


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#57 tim53

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Posted 21 May 2019 - 09:28 AM

Intes is still in business, I would send it back.

Robert

The scope is almost 30 years old.  Think they'd take it back?


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#58 DAVIDG

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Posted 21 May 2019 - 10:39 AM

 The issue is  if Intes would take it back is what did they guarantee ? Did they state a wave front rates ? If so how do you prove that ? They can state your test methods are flawed. If they did not spec out a wave front rating  they most likely guarantee your satisfaction. So they can send you another that might be just like the first ,  because  that is quality that they made them too.  The odds are pretty good that is case since if they were testing each scope  with a method that would show a 1/4 wave or worse type errors they would have easily seen the problem and hopefully not shipped it. So you can either accept that quality or get your money back but you might not get ever get  1/4 wave or better optics. 

 

                - Dave 


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#59 tim53

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Posted 21 May 2019 - 10:57 AM

I wasn’t serious. I bought a new ns925gps In 2004 that the original buyer had bought two by mistake. But celestron wouldn’t honor the warranty because I wasn’t the original owner from their perspective. 



#60 bremms

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Posted 21 May 2019 - 11:13 AM

Thing is, I've sold a few duds. Hate to admit that, but I can't bear the entire burden of all the mediocre optics that come through my hands. If the optic is truly bad, that is different. Thing is, I have a 1978 or 79 C8 that is very very good for a C8. Tried to sell it locally and nobody seems to want the poor thing. At a club event three people remarked at the image quality.. Oh I want a newer one. Paring down my collection has proved difficult. Very few want old scopes, they want GoTo, they want a 2" diagonal and a couple eyepieces. Can you add GoTo for me?? What the heck??


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#61 tim53

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Posted 28 May 2019 - 10:30 AM

So after I got back from Cosmic Acres yesterday, I spent a few minutes starting to set up my test stand so I can switch back and forth from figuring and lap pressing, to putting the OTA back together and dpacking the system.  The radius blocks from the stand I made this from are too big for the 6" OTA, so I stuck on some thick felt pads to center the tube and serve as a sort of "soft V-block" to hold the OTA.  It needs to either very rigidly hold the tube, or not at all but accurately enough that I don't have to fuss with alignment every time I put the tube back.  Problem is that the cell fits in the tube tightly enough that I likely will need to be able to move it around to get the cell in and out.  The mirror is held in the cell by a step in the baffle tube, which screws into the cell, and there are fiber washers on either side of the mirror so there's no metal to glass contact (except in the bore, I suppose).  The threads were sticking, so I put a little super lube on them and that helped quite a bit.  I might do that where the cell goes into the tube to make removing it easier as well.  There is no provision for collimation adjustment.

 

The tube is actually two parts of slightly different diameters, apparently epoxied together in the middle.  Sometimes, strange is truther than fiction.

 

Depending on how successful I am in making this a planet-slayer, I might make a whole new tube for it - perhaps one of my signature 9-sided plywood tubes, and make the guidescope and finder detachable (and the finder adjustable!), and attach a dovetail to it so it can ride on one of my Tak GEMs.  I like the mechanism for aiming the guidescope, but rather hate that it's attached to the tube via a nut on the inside of the tube.  And the non-adjustable finder is held on by phillips head screws from the inside of the tube.  I'm sure I've seen dumber arrangements in my time, but I'm having a hard time remembering them!



#62 tim53

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Posted 28 May 2019 - 04:03 PM

Oh, and that guidescope mount?  Those of you familiar with the way Meade did their dec tangent arms, where there's a flexible metal "strap" attached between the end of the arm and the nut on the threaded rod know that the difference in radius and angle is accomodated by flexing that metal strap piece.  The guidescope on the MK 63 is similar, only the post that holds the sky end to the tube is rigid, so the flexure is accomodated by the tube!  So there's a dent in the tube there that I made worse trying to figure out how to remove the guidescope.  Even if I don't make a new tube for the scope, THIS will be changed.  



#63 starman876

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Posted 28 May 2019 - 04:56 PM

Ok. Figured it out. Was rather a pain and a lot of what they did makes little to no sense (to me). It’s like they wanted to hide the fasteners.  But it’s such a spartan telescope that I have to wonder why. 

 

Anyway, now I have a mess. The tube was painted after assembly, cause it’s bare under the fork brackets. The bolt

for the sky end of the guide scope has a nut on the inside of the tube, and the finder brackets have Phillips screws on the inside of the tube. The finder isn’t adjustable, so it’s kind of useless. But I did like the helical focuser on it. 

 

I may modify the hell out of it if I get the optics working well. The other option would be to put it all back to stock and sell it. 

 

I wanted to get more experience refiguring things before tackling my more challenging projects. 

 

Remember when i ruminated that the mirror might be too tight right in the cell?  Well it isn’t. Moving around a bit even. The baffle tube is screwed onto the cell, with a bright green o ring or gasket against the mirror. So at least getting it out should be easy. 

that is a lot of parts.  You got to love guys who like to take things apart and know how to put them back togetherwaytogo.gif



#64 starman876

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Posted 28 May 2019 - 04:58 PM

The scope is almost 30 years old.  Think they'd take it back?

Only if miracles were being granted again.



#65 tim53

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Posted 01 June 2019 - 12:14 PM

I had this old pine cradle I’d made to test the Kludge Klassic 6” on my OC Mount. I almost threw it away severa time over the years, but now, with some felt pads, it’s perfect for holding the it’s rigidly while I dpac and refigure the primary. All I have to do now i have to do now is align it and clamp it to the redius blocks of my test stand (rotates so they’re flat). 

 

 

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#66 tim53

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Posted 01 June 2019 - 02:19 PM

Getting set up for dpac is kind of squirrely.  I can't get clamps to fit in the space I have and open wide enough to clamp the 3/4" wood to the 1" aluminum.  So I'm using double stick foam tape.  That works pretty well, once I get close and I can tweak things with the xyz stage, but I can't seem to get a round mirror reflection.  I even moved my strip LED closer to the lens axis on the camera. 

Here's what I get inside focus. 

20190601_120514_L_68PNin.jpg

 

Outside focus:

20190601_120708_L_68PNout.jpg

 

And this was tricky, since I see a lot of turbulence.  In all cases, I take 300 frame videos and align and stack those, so the turbulence is minimized.  But the residual misalignment is more obvious.

20190601_121446_L_68PN-focus.jpg



#67 tim53

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Posted 01 June 2019 - 04:26 PM

Couldn’t find my ferric chloride anywhere, so had to come to Fried Electrons for a bottle. Man, this place is almost empty!


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#68 tim53

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Posted 01 June 2019 - 05:12 PM

Seems a shame!  

 

Last pic pic before I strip it!

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#69 rolo

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Posted 01 June 2019 - 10:18 PM

Hope you have lots of free time...


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#70 tim53

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Posted 16 June 2019 - 06:07 PM

Worked on this scope today.  Finished stripping the coatings and made a pitch lap.  set the scope up to dpac before getting serious, to make sure I could without the primary coated.  I had managed to wash my index mark off the edge of the mirror, so I had to rotate the mirror and reinstall it several times before I found the reflection without a lot of hassle.  Polished with coc strokes for 10 minutes with tool on top and a 5 pound weight, and got really good "feel" in the polishing.  

 

Then, I cleaned it up and put it back in the tube...   ...and spent the next 2 hours trying to find the reflection again.  Maybe I washed the index mark off again by mistake and was lining up on some other mark?  

 

Anyway, before I got too angry, I decided to put everything away and cogitate.  Trouble is I won't have another chance to work on this until at least middle of next month.

 

Right now, I hate this scope.  I hate the way it's assembled, with the finder being mounted from inside the tube and the guidescope adjusting by bending the tube wall (no jive!).  And I hate that the RA circle is indexed backwards (for the southern hemisphere, perhaps?).  I hate that there's no means of collimating the primary, at least.  There must be some wedge to it or it wouldn't need to be oriented the same way every time.

 

So I probably need to add a means to collimate the primary, or start over and make a new tube, or at least a frame to mount the optics in for testing.


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#71 Terra Nova

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Posted 17 June 2019 - 09:44 AM

 

Anyway, before I got too angry, I decided to put everything away and cogitate.  

 

 

When my smarta s s college educated and drafted cousin (RIP last March) was at Fort Ord going through AIT his drill sergeant was on his butt over his marksmanship skills. To whit my cousin replied, “I masticate regularly, three times a day!” The drill sergeant’s reply was “I figured you would.” (He survived Vietnam (1970) and came back even more witty and sarcastic!) 

 

:rofl:


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#72 rolo

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Posted 17 June 2019 - 10:14 AM

Worked on this scope today.  Finished stripping the coatings and made a pitch lap.  set the scope up to dpac before getting serious, to make sure I could without the primary coated.  I had managed to wash my index mark off the edge of the mirror, so I had to rotate the mirror and reinstall it several times before I found the reflection without a lot of hassle.  Polished with coc strokes for 10 minutes with tool on top and a 5 pound weight, and got really good "feel" in the polishing.  

 

Then, I cleaned it up and put it back in the tube...   ...and spent the next 2 hours trying to find the reflection again.  Maybe I washed the index mark off again by mistake and was lining up on some other mark?  

 

Anyway, before I got too angry, I decided to put everything away and cogitate.  Trouble is I won't have another chance to work on this until at least middle of next month.

 

Right now, I hate this scope.  I hate the way it's assembled, with the finder being mounted from inside the tube and the guidescope adjusting by bending the tube wall (no jive!).  And I hate that the RA circle is indexed backwards (for the southern hemisphere, perhaps?).  I hate that there's no means of collimating the primary, at least.  There must be some wedge to it or it wouldn't need to be oriented the same way every time.

 

So I probably need to add a means to collimate the primary, or start over and make a new tube, or at least a frame to mount the optics in for testing.

If you think in Russian, you'll love the scopelol.gif  Patience my friend, they say its a virtue!waytogo.gif



#73 DAVIDG

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Posted 17 June 2019 - 10:15 AM

 Tim,

    Take the primary back to a sphere using the Foucault and Ronchi as the test method. That will break in the lap and get you to smooth figure. Once you get there you can pick up the fight with trying to get thinks aligned for DPAC testing. 

   The easiest way I  have found to align a scope to the flat is to look into the scope as it is pointed at the flat. You'll see multiple reflects  and your eye looking back at you. You adjust things so the reflections all line up and your looking directly into the pupil of your eye.   The problem your having with getting things to line up is the fact that your light source is off axis from your camera. You have F/2 primary so you have to be dead on the optical axis.  That is why a use small prism on my tester. This puts the light source and the return beam from the optics no more then a 1/32" from each other. 

 

                     - Dave 

 

tester.JPG


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#74 tim53

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Posted 17 June 2019 - 10:42 AM

I do have a 1/2” prism. I’ll try that next time I work on this. 



#75 tim53

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Posted 01 July 2019 - 11:42 AM

So in the process of trying to follow directions, I goofed.  I was trying to wear down the 70% zone with TOT w strokes with a sub-diameter tool (my tool is 5.75" and the mirror is 6.75").  And I made the TDE a lot worse than it was.  Dave suggested i make a full size lap, so I did.  It was ridiculously easy to make, so I'm annoyed with myself that I hadn't done this in the first place.

 

I cut a 5.75" disk from 3/4" plywood, shellacked it (shellac isn't exactly water proof, but it dries really fast, so that's my story and I'm sticking to it).  I then made a tape dam around the edge with painters tape 3 layers thick.  Then I took the container of Gulgoz 64 I'd bought last week and went around the tube with the handle of a screwdriver to bust it into little pieces (with the lid on so they don't fly all over the place).  I then poured the chips into a plastic microwave bowl from a chicken teryaki rice bowl I'd eaten for lunch:

 

msg-6788-0-20252300-1561836000.jpeg

 

Then onto the plywood tool and into the toaster oven:

msg-6788-0-85864600-1561836033.jpeg

 

After about 30 minutes at ~200F, I took it out to let it cool:

msg-6788-0-28996600-1561837880.jpeg

 

Once it had cooled enough to remove the tape, I did.  Then, I used 1" tape to lay up "guides" for cutting the channels with a solder gun.  I'd done this before, and liked it then.  This time I think it was a bit messy and I'd rather cut them with a utility knife like Dave showed me in the mirror class.  Still a bit messy, perhaps, but not as bad.  I don't have pics of doing that because I didn't want to get pitch on my phone to take pictures with it.

 

So, after about an hour of polishing with MOT, coc strokes with about 3/4" overhang, here's where I'm at.  It might look awful (TDE is pretty egregious), but it's a lot better than it was before.  The hole, in particular, is smoothing and shallowing out.  And the TDE is closer to the edge than it was.

 

I had to put everything away for a while to come out to Utah.  So probably this is it until Late July or even mid august (after Stellafane).

 

Inside ROC:

msg-6788-0-83300400-1561848252.jpg

 

Outside ROC:

msg-6788-0-36070200-1561848285.jpg

 

At ROC (this image isn't the best, as I don't think I was quite at focus, and my ronchi bands were drifting slowly across the scene for some reason - sag? - that I haven't pinned down):

msg-6788-0-61815900-1561848320.jpg


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