Question about phase contrast

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mintakax
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Joined: Mon Jul 29, 2019 12:06 am
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Question about phase contrast

#1 Post by mintakax » Thu Aug 15, 2019 1:25 am

My scope came with a turret with 4 DIC prisms (10x,20x,40,100x) and 2 phase rings (10x and 40x). It did not come with any phase objectives so I started just doing BF and DIC, switching happily between turret positions and objectives with no disturbance to any alignment. I have since procured a 10x Phase objective and am really finding it valuable, however I am noticing that it is very sensitive to the alignment between the condenser ring and objective ring. If its properly set up for phase and I switch the turret (and objective) to DIC and then back to phase, the alignment is off and needs to be repeated. Is this par for the course or is there something I can do to prevent this ? I have recently lubricated my turret and it turns pretty smoothly.

PeteM
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Re: Question about phase contrast

#2 Post by PeteM » Thu Aug 15, 2019 2:55 am

Once adjusted, the phase ring should be able to be rotated in the condenser and come back in alignment.

So there is slop somewhere in your system. Some possibilities:

- Your condenser isn't properly locked in place. I believe you'll have one locking screw, a spring loaded locator, and two adjusting screws. All of 'em need to be present and accounted for.
- The phase ring is loose in the condenser turret. Ought to have a spring and two adjusting screws holding it in place.
- Your condenser turret has a loose indent.
- Your nosepiece has a loose indent.
- You're adjusting the condenser vertically and not returning it to the same place

Do you have a phase telescope? If not, this will make it easier to figure things out and make future adjustments.

If things are a bit worn, you might also try always approaching the phase ring from the same clock direction. Could be the indents will have a bit of backlash that's not symmetrical.

Worst case it takes you under 60 seconds to get the annuli aligned once you have a bit of practice and a phase scope.

mintakax
Posts: 72
Joined: Mon Jul 29, 2019 12:06 am
Location: Boulder CO, USA

Re: Question about phase contrast

#3 Post by mintakax » Thu Aug 15, 2019 4:50 am

PeteM wrote:Once adjusted, the phase ring should be able to be rotated in the condenser and come back in alignment.

So there is slop somewhere in your system. Some possibilities:

- Your condenser isn't properly locked in place. I believe you'll have one locking screw, a spring loaded locator, and two adjusting screws. All of 'em need to be present and accounted for.
- The phase ring is loose in the condenser turret. Ought to have a spring and two adjusting screws holding it in place.
- Your condenser turret has a loose indent.
- Your nosepiece has a loose indent.
- You're adjusting the condenser vertically and not returning it to the same place

Do you have a phase telescope? If not, this will make it easier to figure things out and make future adjustments.

If things are a bit worn, you might also try always approaching the phase ring from the same clock direction. Could be the indents will have a bit of backlash that's not symmetrical.

Worst case it takes you under 60 seconds to get the annuli aligned once you have a bit of practice and a phase scope.
Thanks so much Pete-- Very comprehensive list and as soon as I read it, I knew it was probably e a loose phase ring. Sure enough one was loose. I tightened the adjusting screws and its all good now.

I do have a phase telescope and not sure how I would do the phase alignment without it. I do need to get an eyepiece adapter so I don't have to take my camera off and use it in the photo tube.

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75RR
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Re: Question about phase contrast

#4 Post by 75RR » Thu Aug 15, 2019 5:30 am

I do have a phase telescope and not sure how I would do the phase alignment without it. I do need to get an eyepiece adapter so I don't have to take my camera off and use it in the photo tube.
Not sure I understand why you would need to use it in the photo tube - there should be a lever that allows you to switch viewing between the eyepieces and the photo tube.

Are the eyepieces and the photo tube not parfocal? If not, they need to be.

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mintakax
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Joined: Mon Jul 29, 2019 12:06 am
Location: Boulder CO, USA

Re: Question about phase contrast

#5 Post by mintakax » Fri Aug 16, 2019 3:04 pm

My eyepieces and photo tube are par focal , to do that I had to shim up the eyepieces a bit. The CT-5 telescope is 23mm OD and my eyepieces are 30mm, but the CT is the same size as the photo eyepiece so fits in the photo tube. Am I missing something ? I do know about the 3 position lever that controls where the light goes between the eyepieces and photo tube. I usually have it set on the middle position. IIRC, 80% photo tube/20% eyepiece ?

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75RR
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Re: Question about phase contrast

#6 Post by 75RR » Fri Aug 16, 2019 3:22 pm

Am I missing something ?
Thanks for your reply.

It would appear that you are not missing anything.

I had assumed that your phase telescope was 23mm as were the eyepieces and that the photo tube was the same.

Perhaps this might help: https://www.ebay.com/itm/Eyepiece-Adapt ... 3729023119
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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