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Equipment Discussions >> ATM, Optics and DIY Forum

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Scout92
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Reged: 12/20/11

Loc: Hoquiam, WA.
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5572469 - 12/15/12 11:55 AM

Quote:

Scout 92, you should try to build a Hypo keeping STRICTLY to my specifications, and use a low power eyepiece to get anything from X16 to X25. You will then see what a Hypo can do. If you dont like then OK, no sweat, but at least you tried to see one for yourself, instead of just shooting it down in flames because it does not conform.




Jon,

I plan on building (already strarting to collect materials in fact) trouble is I have no clue where to find a lens like the one you discussed so I have to research that and as of right now do not have he skills to produce on my own. As soon as I get the materials I will check it out and form my own opinion (don't understand most of the opinions on here anyway...yet) thanks for the advice and I enjoyed reading your original hypo thread.


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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Aljr]
      #5572483 - 12/15/12 12:01 PM

As I said watch out for those lenses but they are the right focal ratio for a simple Hypo, you must repolish them. Remember they must be F:40, bottom limit F:30.

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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5572501 - 12/15/12 12:12 PM Attachment (25 downloads)

Image of a security light taken with a 76mm F:40 PCX OG using a 7 X 50 bino OG for the reduction lens. fuzzy due to misty night. Note lack of colour.

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kfrederick
Carpal Tunnel
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Reged: 02/01/08

Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5572683 - 12/15/12 02:22 PM

Mark does the BK7 polish faster than Pyrex??

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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
Re: Hypo/Dialyte testing discovery new [Re: Aljr]
      #5572890 - 12/15/12 05:20 PM

I discovered something that might be of value, whether you're making a Hypo, or Dialyte.
****
I have my meniscus sitting on a windowsill. The conjugate focus (with objects outside) happens to be where a chair is placed in the room.
I picked up a pair of binoculars, and took a look. The lens aperture was totally a blur, and a uniform color. Strange, I noticed that just using my eye, the color resolved into fuzzy blobs.
So I went downstairs, and drilled a 1mm (.040") hole through a piece of sheet metal. (smallest I had)
The blobs of gray, white and green seen with naked eye resolved into treebark, and evergreen individual pine needles, with their characteristic curved tips!
The bark grooves off an ash tree are vertical, so I swept the grooves across the lens aperture, and the dark lines representing the grooves revealed straight lines to within 1/32" of the meniscus edge on the concave side. My methods and theories of polishing remain intact!!!
I could see these edge issues on each surface, but using an apertured hole to view through sharpened things up to an excellent degree.
The hole I am sure, apertured the lens down to a smaller virtual lens, but being near my eye, allowed me to see the whole aperture, and some of the surrounding background, all at once.
There are individuals who would call it preposterous that I could test edges and general conditions simply by eye, but it is possible; if you pay attention to what you can see. Experience can be a big help as well.
Aljr, mine looks very smooth cmpared to your pic. No trace of zones.
M.

Edited by Mark Harry (12/15/12 05:27 PM)


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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
Re: Hypo/Dialyte testing discovery new [Re: Mark Harry]
      #5572895 - 12/15/12 05:24 PM

BK7 is very similar to pyrex for polishing time; maybe slightly less (with pads).
This piece as far as waiting to test or otherwise take a look, posed absolutely no problems; and displayed hardly any stress at all using polarized light. Nice piece of glass.
M.

Edited by Mark Harry (12/15/12 05:28 PM)


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Mark Harry
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Reged: 09/05/05

Loc: Northeast USA
Re: Hypo/Dialyte testing discovery new [Re: Mark Harry]
      #5572908 - 12/15/12 05:34 PM

Even though I have just the meniscus objective, I can see more detail, than with naked eye, by far. With a "pinhole" in daylight anyways; using my eye and the aperture stop. I would like to see using a 3/4 and 1/2mm (.030, .020") pinhole would show.
M.


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Hypo/Dialyte testing discovery new [Re: Mark Harry]
      #5573517 - 12/16/12 01:29 AM

Mark,
I know what you mean about the surprising sensitivity of the bare eye when near the focus. When figuring 12.5" f/2 ellipsoidal primaries for a CDK, to quickly see if I'm keeping the very edge under control I use the reflected image if the light fixture overhead. The fine pattern of 'diamonds' in the clear plastic diffuser, when observed as I move my eye laterally, can let me know if the edge is beginning to turn, thus warning me to move the *very* sub-diameter polishing tool a tad farther in from the edge. And this is at f/2, where sensitivity is much lower than at longer f/ratios.

I discovered this somewhat by accident, after noting the not-too-subtle difference in reflection after a spell of overcorrection, as revealed by a tiny test plate made specifically for monitoring the very edge. Thereafter I found that once the proper variation in slope was achieved, with very little practice a departure of about 1/2 fringe over the 1/4-1/3 inch edge zone width of concern could pretty reliably be detected by the eye alone when scrutinizing the way the reflected image modulated as it was made to sweep across said zone, where the slope variation amounted to a good 5-6 fringes.


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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: GlennLeDrew]
      #5573588 - 12/16/12 03:37 AM

This is termed "reading an optic", you will find reference to this technique in ATM somewhere, I do it by looking through an OG under test at a distant object, and put a vertical of some sort in the field, then place the eye at the focus, you can see exactly the condition of the optic, turned edge zones, roughness etc, another way is use the edge of the iris in the eye as a knife edge and do a crude Foucault test, this gives the figure trend as you go along. I peer through commercial scopes sometimes and can see how bad they usually are.

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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5573721 - 12/16/12 08:17 AM

Glen:
-PRECISELY-! I use a light source regularly for a quick look!
******
I can add, the back side of this meniscus is about 122", equating to an 8" F/7.6~. The stroke needed to get rid of the pad polished edge had to be known on the outset. I reduced it to the point of getting a hint of a diffraction line showing, and figured the rest should be obscured by a cell made to hold the lens. Gratifying to see it's so narrow now. I tested it only once, and it's interesting to see the verification with such a simple pinhole.
The other thing- using just the pinhole with the lens can be used as a makeshift scope of sorts with suprising detail.
The lens is facing out toward the barn around 30 yards away. When fully illuminated, it projects a highly detailed image of the face of the barn on the wall- a camera obscura. The aperture is large enough to make a good image even when the curtains are open. The image is 4 feet tall, and 6 feet wide. The conjugate just so happens to be close to the width of the room.
This would make a good educational example to bring to a school...
M.


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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Mark Harry]
      #5576985 - 12/18/12 09:20 AM Attachment (15 downloads)

This specification works very well for imaging and visual viewing. The spec shews the OG as F:31, this is the bottom limit. Two images taken through this scope of test objects. The images were cleaned up in photoshop, the colour was not tampered with.

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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5576991 - 12/18/12 09:22 AM Attachment (16 downloads)

First image

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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5576994 - 12/18/12 09:23 AM Attachment (22 downloads)

Second image

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Ed Jones
Carpal Tunnel
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Reged: 04/06/04

Loc: Sin-sin-atti
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5577060 - 12/18/12 10:26 AM

For only $39 you can pick up an 80 mm diameter achromat from Surplus Shed 400 or 900 mm focal length. I'm sure it will perform much better and have less color.

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Crayfordjon
Vendor - Zerochromat
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Reged: 06/17/09

Loc: UK
Re: Hypo/Dialyte testing discovery new [Re: Ed Jones]
      #5577100 - 12/18/12 10:53 AM

Ed Where can you see the colour in these images ???. So you can get an achro for cheap so what! I am pushing new idea for the inventive and imaginative ATM here. But it seems I am having very little success.

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ed_turco
Pooh-Bah
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Reged: 08/29/09

Loc: Lincoln, RI
Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5577201 - 12/18/12 12:08 PM

At the eyepiece your eye does not process with photoshop. Please show the images as they are.


Ed


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MKV
Carpal Tunnel
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Reged: 01/20/11

Re: Hypo/Dialyte testing discovery new [Re: ed_turco]
      #5577210 - 12/18/12 12:12 PM

Quote:

At the eyepiece your eye does not process with photoshop. Please show the images as they are. Ed



Ditto!


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Ed Jones
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Re: Hypo/Dialyte testing discovery new [Re: Crayfordjon]
      #5577225 - 12/18/12 12:22 PM

Quote:

I am pushing new idea for the inventive and imaginative ATM here



The goal should be something that's an improvement.


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kfrederick
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Reged: 02/01/08

Re: Hypo/Dialyte testing discovery new [Re: MKV]
      #5577235 - 12/18/12 12:28 PM

John is TRYING to share some of his cool design . I like the effort and am glad he shared . John builds his ideas and shares the results .Easy for some who has NOT used this type of telescope to tell the guy who invented and built it and owns it and HAS USED IT is is no good . John you are the ATMs ATM .

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MKV
Carpal Tunnel
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Reged: 01/20/11

Re: Hypo/Dialyte testing discovery new [Re: kfrederick]
      #5577366 - 12/18/12 02:03 PM

K Fredrick, and I think Ed Turco was TRYING to convey that the images John presents here are not what you see at the eyepiece, but Photoshoped RGB photo art. No one is trying to deny John's inventiveness or willingness to share, but what is shared should be WYSIWYG (what you see is what you get).

Mladen


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