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Does my eyepiece look big in this?

Bart

By Bart
in Discussions - Eyepieces

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Bart

Bart

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post-11876-137096842502_thumb.jpg

The phrase made me laugh to myself and thought this photo suited. It's an ES 20mm 100* sitting in a coma corrector sitting in the 10". When you're looking into it the focus knob feels along way away!

Sorry about the completely frivolous nature of this post.....

Barry

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John

John

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I sometimes wonder if extreme weight that projects some distance from the tube poses a risk of distorting thinnish tube wall where the focuser is mounted or even imparting some slight twist to truss tubes ?

I've no evidence of this but when you get 3 or 4 lbs stuck out the leverage force on the focuser mounting must be reasonable substantial, I 'd have thought ?

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Bart

Bart

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You must put a lot of weight on the tube bottom to counterbalance that thing ;)

Well, I use a small lump hammer head taped to a magnet sitting on a cloth that allows to move the weight freely along the tube. Works really well!

John

On my 16" LB truss tube I must say I haven't noticed any movement/distortion, but would agree that weight sitting that far out must exert force to a degree.

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russ.will

russ.will

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As someone who uses a GSO/Altair coma corrector, I looked at the piccie and thought 'Where's the coma corrector?'.

I'm definitely going to have to post a pic of the ES82 30mm plus the CC in the 300p. Here's a teaser thought:

30es82coma.jpg

Panzerfaust? Pah! Here's the Stielhandgranate.

Russell

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John

John

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John

On my 16" LB truss tube I must say I haven't noticed any movement/distortion, but would agree that weight sitting that far out must exert force to a degree.

Probably no problem but the collimation "sweet spot" with an F/4.5 newt is only about 1.5mm around the optical axis. I do wonder if these lengthy heavy combinations could cause just a little deflection from that, unless the focuser is really robust and precise and likewise, the connections between the eyepiece, barlow, and coma corrector.

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russ.will

russ.will

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I think that's an excellent point.

When truing my focuser, square to the optical axis, I was quite alarmed at how little force was required to result in a large shift of the focuser off that axis, relative to a point marked on the opposite side of the upper OTA. Easily a mm or two with light finger pressure.

It left me wondering whether one should collimate for the heaviest or lightest EPs? I suppose the longer FL EPs tend to be the heaviest, but also the lowest magnification and so are slightly more tolerant of collimation errors anyway, so collimate for the lighter end? That's what I'm hoping, at any rate!

Russell

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Bart

Bart

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As someone who uses a GSO/Altair coma corrector, I looked at the piccie and thought 'Where's the coma corrector?'.

I'm definitely going to have to post a pic of the ES82 30mm plus the CC in the 300p. Here's a teaser thought:

30es82coma.jpg

Panzerfaust? Pah! Here's the Stielhandgranate.

Russell

Ye Gods! Don't tell me I falsely stated the picture had the CC as well. Russel, you might just be right in stating the CC may have been hiding in the EP case as this picture was taken. The shame of it! Sorry all, imagine another 30mm or so onto the apparatus!

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alan potts

alan potts

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Something I have commented on before. This is one reason why I will keep the 20mm Nagler even though I have the 21mm E, it just is silly in a top mounted scope riding piggyback on my LX.

To pick up on Johns post about the weight and tube flex, there has to be a point there surely, small maybe but there. I think unless you have a very good focuser the optic path will not be in line and then the tube on top of that. I know for a fact that thefocuser in my Mac/Newt does not hold a true line, you can move it all over the place, it is fine for a BGO. The biggest problem is many of the larger eyepieces focus a good way out and in some cases ( 35mm 41mm 12mm TV's) to name a few will not focus without extra extentions in the mix compounding the problem.

Alan

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michael.h.f.wilkinson

michael.h.f.wilkinson

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Something I have commented on before. This is one reason why I will keep the 20mm Nagler even though I have the 21mm E, it just is silly in a top mounted scope riding piggyback on my LX.

To pick up on Johns post about the weight and tube flex, there has to be a point there surely, small maybe but there. I think unless you have a very good focuser the optic path will not be in line and then the tube on top of that. I know for a fact that thefocuser in my Mac/Newt does not hold a true line, you can move it all over the place, it is fine for a BGO. The biggest problem is many of the larger eyepieces focus a good way out and in some cases ( 35mm 41mm 12mm TV's) to name a few will not focus without extra extentions in the mix compounding the problem.

Alan

And then people moan about mirror shift in SCTs :D

In truth, there will be play in focusers on fracs and other scopes due to different weights of EPs (but probably not in SCTs or Maks with moving mirrors, they have the same wobble for all EPs). You cannot make a moving focuser without any play. Any telescope with a small sweet spot will suffer more, of course.

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alan potts

alan potts

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Michael,

I hear what you say and agree, the problems at F10 are only going to be small. For faster scopes though, like the M/N at F5.26, agree not the fastest but with the wobble in the focuser with say a 35mm Panoptic on board is fairly bad ( comes to focus 14mm outside max extention) . I know all focuser have play but there isn't much in my Feather Touch or Moonlite, I know they cost but everything just seems so much better heald in place, but for the money they should do a better job. I just wish it was as easy to change the M/N as it is the SC.

Alan

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