Fitting a USB camera to an alignment microscope

[John McNamaraParticipant @johnmcnamara74883]

Hi All

I want to fit a camera to a Taylor Hobson alignment telescope. A browse on the net revealed many different options, quite a number are aimed at astronomical telescopes and microscopes. I guess they are similar? My knowledge of optics is limited. Has any forum member done this?

I will have no trouble setting up the mechanical side and will be able to make any needed adaptor.

Being a one man band the ability to see the image from afar while moving the target will save a lot of time, and the magnification will improve my accuracy. The latest versions have this… Mine is 50 years young. The new ones are almost the same mechanically.

**LINK**

Regards
John

[John McNamaraParticipant @johnmcnamara74883]

[Michael GilliganParticipant @michaelgilligan61133]

John,

You would probably be disappointed with the result from a typical USB 'eyepiece-replacement'. Many [probably most] of these have no optics, and have vey small sensors. … For the Planetary imaging that Neil is doing, that's ideal; but you would almost certainly find the field of view too restricted.

The primary image of your 'scope is probably about 20mm diameter, and the eyepiece "looks at" this: a tiny webcam-size sensor would only see the central portion.

The better approach would be what the BirdWatchers call 'digiscoping' … keep the eyepiece and attach a camera [focussed on infinity] as a replacement for your eye. This is called "afocal" imaging, as opposed to the "prime focus" technique first-mentioned. … You should find plenty about digiscoping on the web.

Interesting exercise … please let me know how you get on.

MichaelG.

.

P.S. … oops; forgot to mention that if the measurement graticule [reticle] is in the eyepiece, you will almost certainly need to go afocal. … [I'm supposed to be asleep at this time]

Edited By Michael Gilligan on 13/05/2015 04:51:35

Edited By Michael Gilligan on 13/05/2015 05:00:48

[Roger HartParticipant @rogerhart88496]

Suck it and see is my advice. A USB camera is very cheap in the local supermarket, I don't think the usual astro ones are anything special (some used to get modified for exposure reasons but not so much now). You don't need the expensive low light astro cameras unless your application is very special. I doubt the USB cameras sold for microscopes are anything very special either.

Before getting too technical with the optics just offer it up to the telescope eyepiece and see if the image is any good. A USB camera is just like your eye – a lens with a silicon retina, nothing more.

[Clive HartlandParticipant @clivehartland94829]

Perhaps you might want to look at some of the air gun attachments, they fit a screen and have a camera looking through the telescopic sight showing the graticule and the target with some videos of pest control.

Clive

[roy entwistleParticipant @royentwistle24699]

Can I suggest that you contact http://www.srb-photographic.com and look at their catalogue

Roy ( no connection just well satisfied )

[Neil WyattModerator @neilwyatt]

All imagine chips are of similar size, so if they sell a camera accessory just try taking out the eyepiece and holding a cheap webcam in its place. Because they replace the eyepiece, the reduction in magnification offsets the smaller image area somewhat.

Cheap USB eyepieces are generally lower quality than a decent webcam with the lens removed.

Digiscoping (camera held to eyepiece) will give widest FOV.

The biggest magnification is eyepiece projection where no camera lens is used and you project though the eyepiece.

If you can get it to focus and the FOV is ok, then you are in business. DSLRs have a larger chip and therefore wider FOV but that isn't a DSLR in their picture!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 13/05/2015 11:05:09:

(a) All imagine chips are of similar size

(b) but that isn't a DSLR in their picture!

.

(a) … ?

(b) … but it might be a C-mount camera, which typically have larger chips.

The spec. for the new Taylor Hobson device would be useful.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 13/05/2015 12:33:46:

Posted by Neil Wyatt on 13/05/2015 11:05:09:

(a) All imagine chips are of similar size

(b) but that isn't a DSLR in their picture!

.

(a) … ?

(b) … but it might be a C-mount camera, which typically have larger chips than do webcams.

.

Edit: three words added, for the sake of clarity ^^^

[John McNamaraParticipant @johnmcnamara74883]

Hi All

You learn something every day…Thanks for the as always good advice.

I have spent quite a bit of time digging around the net, so far the only specifications I have found for the Taylor Hobson alignment telescope have been dimensions. I guess they regard the rest as proprietary. I did see reference to the focal length of the eyepiece? being 8 inches.

This was mentioned on one site I visited. The fixed camera eliminates parallax which can cause the aiming image to move about when you move your eye side to side or up and down. This can cause an error. Without a camera you have to adjust the device to eliminate this. In this application the mount must be solid not like some of the rather "Wonky" setups seen.

I have found a couple of videos that explain the process of Digiscoping pretty well. Both are non technical. They are focussed, sorry Pun! on nature photography using a spotting telescope. However as the first UK video makes clear all eyepieces are similar because they all have to interface with the human eye.

This one form the UK in two parts **LINK**

And this one from the US **LINK**

They both suggest that a basic camera (with a lens that is of a similar diameter to the eyepiece of the telescope) will work better then larger lens DSLR camera. The demonstrations are fairly clear. in the US video the presenter also shows a larger camera being used, he mentions it needs to be a camera fitted with a 40 to 50mm lens but not more.

Both show proprietary adaptors of varying mechanical merit, That wont be a problem for anyone reading this in here. I already have a nice piece of Aluminium waiting to be machined, once I have sorted a nice little camera.I don't know much about them also I do have a DSLR but it is big the lens will not work.

I do want a camera that can echo the image in the viewfinder LCD to a PC screen at the same time via a USB cable, maybe that is a common function. I don't Know.

I will not really need to take many photos of measurements although a record of accuracy is a nice thought, when I have the setup working I will post a photo here.

Regards
John

[Michael GilliganParticipant @michaelgilligan61133]

Brief details of the current Alignment Telescopes, here.

MichaelG.

[John McNamaraParticipant @johnmcnamara74883]

Hi All

I Found another link **LINK**

Towards the end there is useful information on selecting the right camera.
After opening the page Type Ctrl F to open the finder.
Then enter in the little find box near the top left of the page the word… Avoiding
It will then take you to a section Understanding and Avoiding Vignetting

Worth reading if you are going to connect a camera to an eyepiece.
There are many examples of cameras adapted and connected to instruments.

Regards
John

[Michael GilliganParticipant @michaelgilligan61133]

John,

I've just found a couple of videos, about the Taylor Hobson CCD and CCTV attachments, here.

MichaelG.

Edited By Michael Gilligan on 13/05/2015 21:05:33

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