Appenzellersun, first light in the hand, Schiefspiegler/Kutt

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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

thank you very much for the additional explanation. The scope was made by Lichtenknecker, Belgium, so no modification at all.

Doing the alignment I can move the laserpoint along a thin line across the Primary mirror. No Problem with tat, but I can not move the laserpoint coming back from the Primary mirror into the secondery. (see your pic schiefsecondary and my pic laseronsecondary) The red dot coming frrom the Primary is out side the tube.

I will now restart the whole process. First I'm setting back all M and S screws to Zero, make a mirror cover for the secondary and the Primary with a cross at the Center. Then start with the secondary pointing the laser to the cross on the center, then tilting the secondary so the laserpointer hit the center cross of the primary. next I move the secondary out of the view using just screw M on the Primary. I'll get there, it is just a question of time, but since it is raining there is no need to rush.


A remark to my pic viewupthe tube: Looking up the tube I do not see any sign of the secondary inthe Primary but since the camera is well aligned you see some of the edge of the tube


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by DavidG »

Walter,
When the primary is aligned correctly, the laser being reflected off it should be around 62.5mm (125/2) from the edge of the secondary. It may be much more depending on the design. So if you taped a piece of paper off the back of the secondary mirror cell you can use that as a target to align the primary.
You don't have to adjust the primary so the laser is again hitting the center of the secondary. Why I do that step is I then know the primary is tilted correctly in the "S" plane and over tilted in the "M" plane. So in theory I just need to adjust the tilt in the "M" plane until the secondary is no longer visible in the primary when looking up the focuser. I then know I will be very close to having the optics in perfect alignment. I can then use an out of focus star to achieve perfect alignment and I only need to continue to move the mirror in the "M" plane.
If you can get the design from Lichtenknecker I can raytrace it and determine the angles and spacing and then determine exactly how far the laser beam should be from the edge of the secondary.
By the way is there no other lens in the secondary tube or one that came with it that is not installed ? There are two versions of the Kutter Schiefspiegler. When the aperture is small, as in 110mm only the two mirrors are required in the optical system. When the aperture is increased to 150mm, one can either increase the focal length to about F/30 and use only two mirrors or if you want a faster f-ratio you need to use an additional weak plano convex lens that is tilted to correct for the astigmatism. With yours being 125mm it maybe designed to use only two mirrors or require the lens corrector and it might be missing.

- Dave
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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David


thank you so much for your additional information. I see your point in doing the alignment in such away. I followed the way lichtenknecker suggested. I can follow your drawing and got the following results on my dining table (don't tell my wife ;-)

centered on the primary with a mask
laserpointontheprimarywithmask.jpg

almost centered at the secondary (mask has to be done later on)
laserpointonsecondarywithoutmask.jpg
result on the laserpointer
reflectionbackontothelaser.jpg

looking up the tube (shows was lichtenknecker explains what has to be seen)
lookingupthetubeexplained.jpg


Don't you agree that it is not bad aligned when the laserpointer is hitting itself after travelling 7 m . The fine tuning is any way done on the star (if clouds permitt) ?


I seem not to be missing a part . There is also no place where I would think has to be something introduced into the optical train


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

hurray, it's not much, but at least I could just see some trees very sharp in the far distance, maybe 2 KM away. Hoping that the clouds go away to see the moon.


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by DavidG »

Walter,
Excellent alignment so far. You just need to tilt the primary away from the secondary so it is no longer is visible in the when you look up the focuser. In your picture, showing what you see when looking up the tube, your at Step 3 in my drawing. The primary mirror is looking at the secondary and not at the sky. You need to now do Step 4. At that point the laser beam should be hitting the wall in your dinning room and pointing at the position of the object you would be looking at in the telescope. If you measure from the edge of the secondary to were the laser beam is located, it should be at least 62.5mm away.
Here is a drawing that shows the optical path of your Schief and were the laser is pointed at each step in the alignment procedure.

- Dave
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opticalpathschief.JPG
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Last edited by DavidG on Tue Apr 08, 2014 8:32 pm, edited 1 time in total.


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

thank you very much for these details. I'll have ago at it. I've already seen it is very simple to turn the laserpoint away from the secondary using the M screw in the meridional plane. It follows the line straight . I'll report again . Thanks for your patience


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

step four done. I'm not far of the 62.5 mm depending on where I hold the ruler on. Looking up the tube I see nothing but the primary. I wonder how that looks on the moon ;-) . I guess I have to wait a couple of days. the laser still points to the middle of the primary give or take a Millimeter. is that o.k. ?


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by marktownley »

Interesting thread guys! :)


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by DavidG »

swisswalter wrote:Hi David

step four done. I'm not far of the 62.5 mm depending on where I hold the ruler on. Looking up the tube I see nothing but the primary. I wonder how that looks on the moon ;-) . I guess I have to wait a couple of days. the laser still points to the middle of the primary give or take a Millimeter. is that o.k. ?
Walter,
You should be very close to having the optics very well aligned. The Moon will look good but stars most likely will still be slightly oval shaped. When the weather is clear or if you can observe a glint of Sunlight off a far off object to act as a artificial star you can get the alignment perfect. Center the star in the middle of the eyepiece and then slightly defocus it so it breaks up in to diffraction rings. It most likely will look ellipical in shape with the long axis of the ellipse in the "M" plane. Now slowly decrease the tilt of the primary so it continues to move away from the secondary mirror. The star will move toward the edge of the eyepiece. Move the star back into the center of the eyepiece. It should look rounder. If it does continue tilting the primary in that direction and keep recentering the star. It should only take a small movement of the tilt of the primary to make the out of focus star perfectly round.
A bit of warning thou, seeing conditions and the fact the tube is open can make it difficult to judge when the out of focus star is perfectly round but you'll be able to get it close and tune up the alignment when the seeing allows. With the alignment close the image should be very sharp. Jupiter should show detail in the clouds and not just three band. Mars as well should show a good amount of detail if the seeing is good. Double stars like Rigel should be an easy split and the star should show a clean Airy disk.

- Dave


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

thank you very much so far. I can't wait for a cloudless night. I'll report as soon as possible


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi cracks

just looked at the moon, crackling sharp. I have to wait until the stars pop out. Very happy at the moment. I know from taking flats on the sun today, that there is fine alignment work to be done. I'll report again


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi cracks

I did take some AVIs which I show here and you can easely see that it is not precisely aligned and above all I was not able to have clean stars. I had always two tailed comets. The scope is back on the bench and hopefully soon I can restart the alignement


moon with AS

Moon_09042014_200610.jpg

moon with RS

Moon_200610_regi6pp.jpg

Jupiter missalignment highlightened to show the problem
jupitest_09042014_204452.jpg
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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by DavidG »

Walter,

You need to do the final alignment on a defocused star. You most likely only need to adjust the primary in the "M" plane so the primary mirror is tilted a little bit more away from the secondary. Remember to recenter the star in the eyepiece after each adjustment.


- Dave


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi David

thank you very much. Yes I hope it will need only adjusting the M screw. The next clear night is spent again on the kutter. I'll Report again


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by GreatAttractor »

Walter, did you succeed with collimation?

I've been reading for some time about Schiefs and I love the idea (and their looks!). Planetary-useful aperture (say, 250 mm) would be impractical, but a 120-130 mm for some H-alpha solar work - this could be interesting. It seems the only good place for a subaperture ERF (to keep the main structure open) would be in the small tube, after the secondary mirror. But this means the small ERF would be subjected to some 3-4x greater than normal irradiance, I wonder if it could take it in the long term (not to mention warming up of the secondary - thermals? Disturbed figure?).


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by eroel »

Walter:
Beautiful instrument, you will love it.
Regards,
Eric,


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Re: Appenzellersun, first light in the hand, Schiefspiegler/

Post by swisswalter »

Hi Filip, Hi Eric

thank you very much.

@Filip I have not yet found any time to work with the lichtenknecker. We hope here for a fine Indian summer to work more on the mods.


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