Resin marble at 40X

Cyclops · Post by **Cyclops** » Sun May 16, 2010 1:50 pm

This is a kiddies resin marble(not the usual glass ones) photographed using my phone and lit with a wind up LED torch (not very effective)
Only trouble is I forgot to reset the colour balance in the phone's camera with was set to incandescent! The whitish parts are supposed to be yellow.

Meiji 4x/10 objective
Basic 10X eyepiece

rjlittlefield · Post by **rjlittlefield** » Sun May 16, 2010 2:06 pm

Working the numbers, I'm thinking that this must be just a small part of the whole marble, and the circular outline is just the limit of the eyepiece field.

Can you tell us what the field width is, at the subject? Take a picture of a mm scale, maybe.

--Rik

Cyclops · Post by **Cyclops** » Sun May 16, 2010 2:13 pm

rjlittlefield wrote:Working the numbers, I'm thinking that this must be just a small part of the whole marble, and the circular outline is just the limit of the eyepiece field.

Can you tell us what the field width is, at the subject? Take a picture of a mm scale, maybe.

--Rik

Err yea, i always get the black circle when using the camera phone.
I have no idea of the field width or how to measure it and really must be getting off here now, so maybe another day!

rjlittlefield · Post by **rjlittlefield** » Sun May 16, 2010 2:58 pm

Cyclops wrote:I have no idea of the field width or how to measure it

Measuring field width is easy -- just take a picture of a mm scale, using the same setup that you used for the marble. Post the picture, and I'll work the numbers if you'd like.

--Rik

Cyclops · Post by **Cyclops** » Sun May 16, 2010 3:20 pm

rjlittlefield wrote:
Cyclops wrote:I have no idea of the field width or how to measure it
Measuring field width is easy -- just take a picture of a mm scale, using the same setup that you used for the marble. Post the picture, and I'll work the numbers if you'd like.

--Rik

Thanks Rik, sorry,had to dash off there,things to do etc. I will have to try that with a ruler but well,if you only knew what I had to go thru to get these images-its no wonder I don't use the scope often! Basically I have to wind up the LED torch,switch it on and point it in the general direction,then hover the phone over the eyepiece while looking for signs of light,lowering it down gently so its almost touching the ocular then oh so carefully squeeze the button and hold my breath! Usually I get something but its like 9/10 I get nothing or its very off centre!

Gary W Brown · Post by **Gary W Brown** » Tue May 18, 2010 7:09 pm

Cyclops,

What's all the moaning about the wind up torch ? Don't you have a nice illuminator for your microscope ?

If your eyepiece has an 18 mm field the diameter using the 4X objective would be 4.5 mm. If it is 18.5 mm, as many of that style are, it would be 4.625 mm.

Gary

rjlittlefield · Post by **rjlittlefield** » Tue May 18, 2010 7:35 pm

Gary W Brown wrote:If your eyepiece has an 18 mm field the diameter using the 4X objective would be 4.5 mm. If it is 18.5 mm, as many of that style are, it would be 4.625 mm.

I agree with your calculation, but the result does not agree with experiment. When I asked Cyclops to shoot a picture of a mm scale, the image showed only 3.6 mm across the field. See HERE, picture of a tape measure.

So... It seems that either the calculation somehow doesn't apply to the setup, or the markings on the scale are not 1 mm. I'd bet on the former.

I had assumed that the hard circular outline is the field stop on the eyepiece. Perhaps it is not? But then what would it be? This looks way too crisp to be a vignette. Were there any eyepieces with 14.4 mm field? Any chance that the objective was designed for a different tube length and is actually acting here as a 5X?

--Rik

Gary W Brown · Post by **Gary W Brown** » Tue May 18, 2010 7:51 pm

Hi Rik,

I think there may be some variations in the fields of the eyepieces but I have not seen a 14.4 mm on a 10X eyepiece (that I can remember). I would question the tape measure.

Gary

Gary W Brown · Post by **Gary W Brown** » Tue May 18, 2010 7:56 pm

Rik,

You may be on target with the 5X objective. Scopes like the one we are discussing often were equipped with 3.5, 4, or 5X objectives as the lowest power of the set.

Gary

rjlittlefield · Post by **rjlittlefield** » Tue May 18, 2010 8:55 pm

Hark, an adventure awaits! Assuming, of course, that Cyclops is interested in participating.

Having a picture of the objective and its markings would help, as would having a picture of the scope used for this exercise. It might be the same one shown HERE, but I'm not sure. If it is the same scope, and the tube doesn't have any lenses in it, then we could get a physical measurement to confirm the tube length. The tape measure can be checked against another rule. Field stop diameter on the eyepiece, hhmm, should be able to get a pretty good estimate by eyeball and ruler at arm's length. Just possibly, if the field stop is accessible from the underside of the eyepiece (as it is on some of mine), a physical measurement could be made.

Even after all that, of course, there's a possibility that the calculations won't match the experiment. I have this vision of somebody in a dim and distant faraway place, accidentally swapping barrels between a 4X and a 5X objective!

--Rik

Cyclops · Post by **Cyclops** » Wed May 19, 2010 1:25 am

Gary W Brown wrote:Cyclops,

What's all the moaning about the wind up torch ? Don't you have a nice illuminator for your microscope ?

Gary

Hi Gary,long time no see!
Yes i did get your lovely illuminator, but unfortunatelu its nowehere near bright enough for some reason, plus it doesnt fit in the slot where the mirror goes-it has a different size and shape connector.

Cyclops · Post by **Cyclops** » Wed May 19, 2010 1:30 am

rjlittlefield wrote:Hark, an adventure awaits! Assuming, of course, that Cyclops is interested in participating.

oh yes, i'm game

Having a picture of the objective and its markings would help, as would having a picture of the scope used for this exercise. It might be the same one shown HERE, but I'm not sure. --Rik

Yea its the same one, a chinese student monocular bought over 20 years ago from Brunel microscopes (oh has it really been that long!!)
They sai they could get me a new carcass for £50 but we just dont have the finances so it will have to wait. I have found that the condenser will stay in if I slightly overtighten one of the little grub screws that control the iris or something.
As for the objective, I'll get a pic later.

Cyclops · Post by **Cyclops** » Wed May 19, 2010 1:31 am

Gary W Brown wrote:Rik,

You may be on target with the 5X objective. Scopes like the one we are discussing often were equipped with 3.5, 4, or 5X objectives as the lowest power of the set.

Gary

Yea i have 3 eyepieces, a 5x narrow field (hardly used cos its like looking down a tunnel) a 10X and a 12.5X

Gary W Brown · Post by **Gary W Brown** » Wed May 19, 2010 3:46 pm

Hi Larry and Rik,

I took a photo of a stage micrometer using a microscope similar to Larry's. Is this the place to post the photo ?

Gary

Cyclops · Post by **Cyclops** » Wed May 19, 2010 3:53 pm

Gary W Brown wrote:Hi Larry and Rik,

I took a photo of a stage micrometer using a microscope similar to Larry's. Is this the place to post the photo ?

Gary

I would guess so but its Rik's forum so its down to our esteemed moderator. Or you could post it in my thread in Equipment Discussions where you can see various pics of my scope.