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Equipment Discussions >> Binoviewers

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tomcody
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Reged: 07/06/08

Loc: Titusville, Florida
Re: Followup to post on aperture reduction in EdgeHD 8 new [Re: Eddgie]
      #5775413 - 04/03/13 12:01 PM

Eddgie,
Have you considered using the Mark V's directly screwed to the back of the scope with no diagonal? should get you to under 140 mm total. As if it were a big binocular? If you have a Alt-Az mount and raise it up? it should work. I know that it causes more neck strain, but with the right chair?
Rex

Edited by tomcody (04/03/13 12:02 PM)


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HowardK
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Reged: 10/20/10

Re: Followup to post on aperture reduction in EdgeHD 8 new [Re: Eddgie]
      #5792526 - 04/11/13 02:36 PM

Quote:

Easy answer

The proceedure to measure... A green laser works best, but a single emitter LED light might work OK.

Next time you use the telescope with binoviewers, bring it to focus with the configuration you want to test on a a star or planet with an eyepeice that gives about a 1mm exit pupil (infinity focus).

Do not touch the focuser knob until after you have made the measurment. It is critical that the telescope be in focus for the configuration you want to test.

When you are ready to do the test, position the telescope facing square to a wall, maybe 1 foot from the wall. Get it as square as possible.

Now, holding your light source above the same eyepeice you used earlier, shine it into the eyepeice. It will take some trial and error, but when you have aligned the laser, you will see a green projection on the wall.

This circle will contain the secondary shadow.

You can measure the apeture directly by simply marking the edges of the circle with a piece of tape (it would help to have somone do this part for you).

Once you have the edges marked, you can measure the distance between the marks and you have your effective aperture.

You can also use a Finder scope as a beam collimator. Place the finder with the objective pointing toward the laser and the eyepiece pointing into the binoviewer.

One person mounted the laser on a camera tripod so he could make tiny adjustments. He rotated the binoviwer to one side so the laser could be horizontal. This may help because it is very difficult to get the laser exactly over the exit pupil of the eyepiiece.

I usually use a lower power eyepecie and I have been told that it can affect the accuracy, but I would think that if anything, it would overstate the amount of aperture, but I think it is still pretty accurate to within a millimeter or two.
Anyway, if you measure some different configurations, please let us know what you find.




Ed...does this aperture test with binoviewers hold true for refractors or is it for SCTs only?


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Eddgie
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Reged: 02/01/06

Re: Followup to post on aperture reduction in EdgeHD 8 new [Re: HowardK]
      #5792842 - 04/11/13 04:55 PM

It works for refractors as well, but in most cases, you won't experience any apeture reduction because of the need to use a GPC or OCS to reach focus.

There is a case though that you could experience apeture reduction.

If you cut the tube on a refractor to shorten it and don't cut the focuser tube, when racked in, the focuser tube can cut into the outside of the light cone.

This has happened even in mono-viewing.

When Stellarvue first got into the refractor business, they sold what really appeared to be a superb 80mm achromat.

Tests showed though, that the scope was operating below its full apeture because the focuser tube was to long.

To answer your question though, this test should work with any telescope.

Glen is the one I think that introduced most of us to the test, so if I am incorrect, I am confident he will let us know.


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HowardK
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Re: Followup to post on aperture reduction in EdgeHD 8 new [Re: Eddgie]
      #5792933 - 04/11/13 05:34 PM

Thanks Ed

I have a Edge 8" arriving next week and want to use it with my Denk power switch and Baader Mk V's...

You got me worried though...with a cut in aperture
Will do the aperture test right away to see just what's what
Scope will be used for a little of everything..not solely planetary though.


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SteveSMS
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Reged: 03/29/08

Loc: Jersey Shore USA
Re: Followup to post on aperture reduction in EdgeHD 8 new [Re: Eddgie]
      #5793149 - 04/11/13 07:36 PM

Hi Ed,

I have not been "unlazy" enough to measure the aperture with my Edge8 and favorite binos. However, after considering the amount of thought you have already put into this topic and were kind enough to share I have come to a personal solution. I have the Baader 2" Clicklock installed and I use a 1.25" Clicklock and a 1.25" diagonal with my TV Binovue with the 2X OCS. This configuration has been VERY satisfying for planetary work and tight doubles. Although it's not exactly a "tight" double for an 8"er Epsilon Lyrae looked like a pair of Castors at approximately 240X. Thanks for bringing this issue to light.

Clear Skies,

Steve


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Eddgie
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Reged: 02/01/06

Re: Followup to post on aperture reduction in EdgeHD 8 [Re: HowardK]
      #5794083 - 04/12/13 10:10 AM

I had the Denkmeier with a powerswitch but used it with a 2" diagonal.

The result was for me very poor when using the reducer mode. I felt the image was very dim with the reducer in, and still somewhat dim even in straight though.

I noticed a pretty dramatic change when I went to the Maxbrirght with the T2 diagonal. It was very much like using a larger telescope.

With the reducer arm in, I felt like I was using a C6.

Again, my system was using a 2" diagonal, but I just don't think you are going to get anything close to full apture using a Mark V with a powerswitch unless you keep the light path very very short.

Looking forward to your report though.


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