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Registration Error in the Field

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#1 Asbytec

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Posted 18 October 2020 - 02:11 AM

I achieve pretty good collimation with my 2" combo tool indoors, but observing in the field at higher magnification I have not been happy with the star images. They are nice in the lower half of the field, and not so nice in the upper field. Even high magnification planetary observing showed marked image degradation in one part of the FOV, but it improved as the image drifted across the FOV.

 

It took me a while to realize it was not a result of my collimation, rather it appears to be a problem with the registration of the focal extender and eyepiece in the 1.25" adapter. Experimenting one evening, I realized I could improve (or degrade) the star image by experimenting with the adapter and focal extender thumbscrew tension and orientation. I finally found a combination that is approximately repeatable. 

 

I believe I understand the difference between eyepiece registration, tilt of the eyepiece optical axis, and the idea the eyepiece and focuser axes should be parallel, at least, rather than centered. The idea a small amount of registration error in the eyepiece can result in quite a bit of axial tilt over the focal length. Even with the focuser axis firmly on the primary center. 

 

I am thinking about getting a Parallizer, and any experience with ES eyepieces and especially the tapered barrel of ES focal extender is appreciated. It looks like it will work. But, for now, taking some cues from other threads on CN, I managed to use what I have to keep the tilt to a minimum with much better star and planetary images across the FOV. 

 

First, the 1.25" eyepiece adapter fits into the 2" focuser with three thumbscrews. I removed the compression ring a long time ago because it caused the adapter to unseat against the focuser. But, now, instead of three thumb screws, I chose to use only the two that are pointed toward the ground and removed the one on top. I understand this forces the adapter snug against the inside of the focuser to help keep it parallel with the focuser. 

 

Second, I make sure adapter is seated in the focuser with the thumb screw on top to counteract gravity pulling on the focal extender, then snug the two thumb screws to hold it. The focal extender is then held seated in the adapter and the thumbscrew (compression ring) snugged enough so it does not move, even with the tapered barrel. The thumb screw pushes town on the focal extender barrel as the compression ring tightens.

 

Next, there is a compression ring in the focal extender to hold the eyepiece, but it does not seem to cause any adverse tilt of the eyepiece even with a tapered barrel. The thumb screw and compression ring are just touching the eyepiece barrel. Too tight does not work well. 

 

Lastly, I observe the star field at high magnification and adjust the tension of each thumb screw until the star images look good everywhere. The 2 to 1.25" adapter is in the same configuration as I collimated the scope, and it appears to be working just fine. With that, planetary images appear to be in better focus from edge to edge. 

 

Any thoughts or experience is appreciated. Also, any nudge toward getting a Parallizer is all I need to order one, provided the ES focal extender will seat nicely so the Parallizer works correctly. But, I seem to have worked out the bugs to a large degree and even learned to check my focuser and primary alignment at night using my combo tool. I've only seen the primary collimation change once, but I think I fixed that, too. 

 

Thanks in advance. 


Edited by Asbytec, 18 October 2020 - 02:26 AM.

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#2 Men2Boyz

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Posted 18 October 2020 - 01:06 PM

Asbytec, your knowledge and experience are way beyond most of us so it seems that no one is rushing in to make suggestions. I'm a newbie so it's okay for me to just blurt out my thoughts like a first grader. I think removing the compression ring of your 2" focuser and then securing your 1.25" adapter with 2 of the original 3 screws probably isn't keeping your adapter parallel with the focuser like you wish it to be. It could be the cause of all your woes. Your 1.25" adapter is being secured by two screws and the opposite surface against the focuser instead of by the original compression ring. You have adopted several countermeasures to compensate for this modification but I think you need to prove that having your 1.25" adapter secured this way is actually giving you the results that you want.

 

The theory that the Glatter Parallizer keeps an eyepiece parallel or at least consistent within it is that it compresses the eyepiece against two optimally designed and manufactured linear ridges. Your focuser modification is pressing the 1.25" adapter against two screws. I'm certain that you know how to test and prove that your modification is working as expected.

 

With all due respects from a newbie, I don't think replacing your 1.25" adapter with a Glatter Parallizer will solve your problem. 

 


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#3 airbleeder

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Posted 18 October 2020 - 03:29 PM

   To properly register the Parallizer according to instructions, secure it in the focuser with 1 set screw, opposite the Parallizer set screw as it also has 2 parallel ridges on the outside of the barrel.

     I use ES 1.25" eyepieces, 4.7 82, 6.7 82, 8.8 82, 11 82, 16 68 and the 24 68 which I use a 12mm barrel extension because it rests on the top of the lip of the Parallizer, so the barrel doesn't seem to rest against the inner parallel ridges. I don't use a focal extender so I have no idea with that.

    I will say that the Parallizer is my favorite accessory simply because it is the most useful. It consistently and repeatedly secures my 1.25" collimation tools parallel in the focuser so I have no doubt it secures my eyepieces justas well.  


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#4 Men2Boyz

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Posted 18 October 2020 - 04:22 PM

After airbleeder’s explanation of how the Parallizer is constructed with outer parallel ridges as well as inner ridges, it looks to be a great solution for your registration problem. I may need to order one for myself.



#5 Asbytec

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Posted 18 October 2020 - 05:42 PM

Men2boyz, thank you for replying. Star testing does seem to show some improvement with the process above. I don't know if I can prove using only two screws actually achieves a parallel condition for the 1.25" adapter. I can only infer that it might if I collimate with the same registration of the Combo tool. With each adjustment above in the field, there is improvement.

Airbleeder, that is what I am afraid of. The focal extender has a similar body design to the ES 4.7 82 you mention. It does taper toward the barrel, but not sure the taper is compatible with the cone shaped lip of the parallizer. So, for now, I gotta experiment and seek advice. I did employ the opposing set screw concept hoping to strike gold. It does seem to improve the view, but it takes a little tweaking in the field. Or buy barrel extensions. I might try that.

Edited by Asbytec, 18 October 2020 - 05:49 PM.


#6 airbleeder

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Posted 18 October 2020 - 08:33 PM

   Maybe I wasn't clear enough. All my 1.25" ES eyepieces consistently register parallel to the focuser including the 4.7mm. The ES 24mm 68* does also, but requires the barrel extension to enable it to reach the parallel ridges inside the Parallizer. The cone is compatible with all my ES 1.25" eyepieces, but I do recall a thread a couple years ago in which a poster had performed surgery on the top of a Parallizer because he found the ES 8.8mm 82* eyepiece body incompatible with the cone of the Parallizer. Personally, I've never noted any problem.

   Like I said, all my 1.25" collimation tools  repeatedly, consistently register in the Parallizer and I've never noticed anything which would make me think the ES eyepieces registered anything other than parallel to the drawtube. By that I mean feel the eyepiece tilt or seen a tilted focal plane.


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#7 sixela

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Posted 19 October 2020 - 05:15 PM

The cone is not what is used to register most eyepieces in a Glatter, the flat at the bottom is, together with the ridges; the eiepiece is pushed down against them by the angled set screw.

For some thicker eyepieces like the Nikon Nav-HW 12.5 the shoulder does seat itself in the cone and not at the bottom, but the ridges still do their bidding.
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#8 MellonLake

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Posted 19 October 2020 - 05:53 PM

I have owned the Glatter Parallizer for a couple of years and use it with Meade 5000 UWAs and an Explore Scientific 24mm 68°.  I have played quite a bit with the registration and found that registration is better when the 1.25" eyepiece is pulled up slightly so that the eyepiece body is not in contact with the Parallizer upper cone. This prevents any binding of the eyepiece before the 1.25" barrel is fully registered in the Parallizer.  This will work with all eyepieces if there is a concern about registration.

 

I also use the Parallizer for collimation to ensure collimation is perfect. 

 

FYI - It was Kipperfeet that modified his Parallizer to remove the conical surface.  The conical surface was intended by Glatter to maintain the infocus length available.  I wish it was flat on top as I don't like the conical surface.  Kipperfeet also suggested the slight pull out of the eyepiece to ensure proper registration.  

 

Note the Gap between the Body of the eyepiece and the Parallizer

 

parallizer with ES68 small.jpg

 

Registration on ID

registration small.jpg

 

 


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#9 MellonLake

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Posted 19 October 2020 - 05:57 PM

FYI my 24mm ES 68° has the same tapered barrel as the ES focal extender and it seems to register consistently.  The barrel extension would help if you are not confident in the registration.  


Edited by MellonLake, 19 October 2020 - 06:06 PM.


#10 airbleeder

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Posted 19 October 2020 - 09:21 PM

I have owned the Glatter Parallizer for a couple of years and use it with Meade 5000 UWAs and an Explore Scientific 24mm 68°.  I have played quite a bit with the registration and found that registration is better when the 1.25" eyepiece is pulled up slightly so that the eyepiece body is not in contact with the Parallizer upper cone. This prevents any binding of the eyepiece before the 1.25" barrel is fully registered in the Parallizer.  This will work with all eyepieces if there is a concern about registration.

 

I also use the Parallizer for collimation to ensure collimation is perfect. 

 

FYI - It was Kipperfeet that modified his Parallizer to remove the conical surface.  The conical surface was intended by Glatter to maintain the infocus length available.  I wish it was flat on top as I don't like the conical surface.  Kipperfeet also suggested the slight pull out of the eyepiece to ensure proper registration.  

 

Note the Gap between the Body of the eyepiece and the Parallizer

 

attachicon.gifparallizer with ES68 small.jpg

 

Registration on ID

attachicon.gifregistration small.jpg

  I've never felt I needed to slightly pull the eyepiece out as I've not noticed any registration problem with any of my 1.25" eyepieces, but I do leave the 25mm extension on the ES 24mm 68 for assurance.



#11 Asbytec

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Posted 20 October 2020 - 04:39 AM

Still here and reading posts, thank you for replying. Would love to get outside and tinker and observe some more, but gotta wait for Typhoon what's-its-name to pass next day or two. 

 

Mellon and Sixela, thanks for the clue as to the purpose of the conical throat. 

 

Right now the work around described in the OP seems to work well enough. It requires some real time tinkering, but it may not be entirely repeatable. Maybe the parallizer is the way to go for more consistent registration...in the field. 


Edited by Asbytec, 20 October 2020 - 04:44 AM.


#12 Starman1

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Posted 20 October 2020 - 02:12 PM

Norme,

If you add a Parallizer to your kit, presume you will add barrel extenders to your eyepieces.

The small section of full diameter barrel above the undercut cannot be pressed against the far wall of the Parallizer if the eyepiece does not seat on the Parallizer's flat surface next to the bore.

That means the thumb screw can tip the eyepiece.

A longer straight section of barrel below the undercut means you can pull the eyepiece out until the undercut is above the bore of the Parallizer and the Parallizer will work perfectly.


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#13 Asbytec

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Posted 20 October 2020 - 03:41 PM

 

The small section of full diameter barrel above the undercut cannot be pressed against the far wall of the Parallizer if the eyepiece does not seat on the Parallizer's flat surface next to the bore.

 

Hi Don, I am counting on this to not be the case. I believe it will be okay. After some investigation and offline discussion, the barrell should seat fully with a body taper that is compatible with the conical lip. I think it's worth a try. If not, no harm. No foul. 



#14 Starman1

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Posted 20 October 2020 - 06:24 PM

The CNer who machined the top of his Parallizer flat found that eyepieces with conical tapers got shoved sideways and if the full diameter section above the undercut was sitting outside the bore of the Parallizer,

the eyepiece got tipped when the thumbscrew was tightened.

He ascertained the full diameter barrel section above the undercut had to be pressed against the opposite wall to register the eyepiece correctly.

His solution was to machine the Parallizer flat.

Another solution is to add a 1" or so additional barrel extender to the eyepiece and merely pull the eyepiece out of the Parallizer until only the full 1.25" diameter barrel below the conical undercut is inside the Parallizer.


Edited by Starman1, 20 October 2020 - 06:24 PM.

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#15 sixela

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Posted 20 October 2020 - 06:32 PM

Which is why I have a Parallizer and also several Baader PushFits. I prefer the Parallizer, but for some eyepieces pulling them out prevents you from reaching focus correctly (especially when using a Paracorr) -- that increases the effective height of the Parallizer -- so something lower profile is again necessary.

To give just one example, you'll be disappointed if you have a Paracorr and want to use a Parallizer to give a Nikon Nav HW 12.5 2" filter threads (that eyepiece doesn't require a lot of focuser in-travel when you use the provided 2" barrel, but that comes without filter threads, so you can't even install a 2" barrel extension)..

Mind you for that even the Baader only just works (or rather, fails to work but it's close enough). For that eyepiece, only the "really zero height" Starlight 2"-1.25" adapter works and gives you some slack.

Edited by sixela, 20 October 2020 - 06:34 PM.

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#16 a__l

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Posted 20 October 2020 - 07:00 PM

In the "H" position (or close) of paracorr-2 , there are problems with heavy eyepieces.


Edited by a__l, 20 October 2020 - 07:00 PM.


#17 Asbytec

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Posted 20 October 2020 - 07:01 PM

The CNer who machined the top of his Parallizer flat found that eyepieces with conical tapers got shoved sideways and if the full diameter section above the undercut was sitting outside the bore of the Parallizer,

the eyepiece got tipped when the thumbscrew was tightened.

He ascertained the full diameter barrel section above the undercut had to be pressed against the opposite wall to register the eyepiece correctly.

His solution was to machine the Parallizer flat.

Another solution is to add a 1" or so additional barrel extender to the eyepiece and merely pull the eyepiece out of the Parallizer until only the full 1.25" diameter barrel below the conical undercut is inside the Parallizer.

Understood. The CNer and I have been chatting a bit, and I received thorough information. Chatting a lot, actually. lol.gif

 

The 5x FE has a 37mm base at the bottom of the tapered body, that'll just fit inside the flat lip at the base of the conical section. The small 1.25" barrel diameter just below the tapered body should register in the Parallizer. Anyway, I think the parallizer is the way to go for consistent registration after collimation and in the field (while fiddling with registration in the field until it arrives).

 

I will order a flush mounted 25mm barrel extension just in case it comes in handy, and there is plenty of infocus to accommodate it, if necessary. Really, I am mostly concerned with high power viewing above 200x using the focal extender. I am not sure the Meade HD 60's will fit into the Parallizer, but they fit in the focal extender offering around 240x and higher. Eyepiece registration error should be minimal. 

 

I collimate with a 2" Light Pipe, so I plan to register the Parallizer the same way the Light Pipe is registered. That is, by using the instructions for the Parallizer requiring the 2" adapter set screw(s) be opposite the Parallizer set screw.


Edited by Asbytec, 20 October 2020 - 07:03 PM.

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