How important is exact compliance of tube length?

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Pau
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Re: How important is exact compliance of tube length?

Post by Pau »

I see that Viktor was faster :D
Pau

viktor j nilsson
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Re: How important is exact compliance of tube length?

Post by viktor j nilsson »

Pau wrote:
Thu Mar 18, 2021 3:22 am
I see that Viktor was faster :D
I'm just glad we agreed! :D

seta666
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Re: How important is exact compliance of tube length?

Post by seta666 »

Thanks both of you
viktor j nilsson wrote:
Thu Mar 18, 2021 3:18 am
In fact, it is better to check tube length compliance using a low-power objective. Low power objectives have less depth of focus at the sensor plane than high power objectives, so using low magnification objectives gives you much higher precision.
Now I understand.. My system is still off by a huge margin (10mm or so..), and I though the 4x was badly design because its parfocality is by large the worst.. :D

The way I measured it is by focusing on something with the camera and then rising the eyepiece to match that focus pint, then measure how much I had to rise the eyepiece to get to that focus point
Pau wrote:
Thu Mar 18, 2021 3:20 am
1- I think so. If you use the nominal tube lens focal length focused to infinite, you can think in the inf. objective+tube lens being equivalent to a finite corrected objective

2- Yes, as you well know there is a recent thread on the subject: https://www.photomacrography.net/forum/ ... 95#p259395, although likely more experiments and clarifications would be needed
.............
This is what I thought; I like using the Mitutoyos with DCR-250 so pushing them up will be also an option without having to change the Tube lens

If my foto tube had some more extension tolerance I would use a focusing helicoid as a coverslip correcting collar (theoretically it could work) ,but may still possible to do it via an olympus intermediate piece.

I use glasses, so with them on diopter should be set to 0 I guess but it does not seems as important as making objectives parfocal


Something really weird I have just found ..to make the Nikon CFN 4 parfocal with the 10 20 and 40 I have to rise the olympus eyepiece a little bit more than a mm; does this mean Olympus/nikon TL specs are off by a mm?

Whatever, all this is very good news to me as I have 1mm more to work with regarding photo tube length which now is 17mm; also measuring again the phototube length error with the CFN 4 gives me a new number, my system is off by 6mm instead of the 10mm I thought. I will have no trouble making the phototube 11mm long including camera rotation via a glassless thin polarizer.

Thanks, you made my day!! This and the PZO MIP-5 head I just received that happens to fit on the BH-2, no mods needed.. :D

dolmadis
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Re: How important is exact compliance of tube length?

Post by dolmadis »

seta666 wrote:
Thu Mar 18, 2021 3:47 am
Thanks, you made my day!! This and the PZO MIP-5 head I just received that happens to fit on the BH-2, no mods needed.. :D
Was the MPI-5 modified already for BH2?

If so can you show us some photos on a new post?

Thanks


John

seta666
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Re: How important is exact compliance of tube length?

Post by seta666 »

Nope, is just that they have the same size..almost
Bh2 is a bit deeper and pzo a bit wider

The trinocular fits inside MIP-5, and MIP-5 fits in the body but there is a small threaded pin that should be removed..I guess is safe but have not touched it yet

I am still waiting for a KIP-2, have been told it wiuld take a few weeks to find one in good condition..total project cost will be around 600€

PZO vs BH-2 Dovetails

Image

The small screw pin that should be removed

Image

I will start a new thread when project is finished.
Last edited by seta666 on Thu Mar 18, 2021 8:05 am, edited 1 time in total.

dolmadis
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Re: How important is exact compliance of tube length?

Post by dolmadis »

So the BH2 trino fits into MPI-5 well enough.

How does the MPI5 fit the BH2 stand? OK?

BR

John

seta666
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Re: How important is exact compliance of tube length?

Post by seta666 »

Was not clear enough, I edited it.

It fits but there is a small threaded pin that prevents it to go fully in, I guess is is just some kind of locking pin but I will ask before removing it.
Maybe centering will not be 100% perfect, I will have to see once I get the KPI2

dolmadis
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Re: How important is exact compliance of tube length?

Post by dolmadis »

Looking forward to seeing how you fit PZO DIC to BH2 stand and trino. The other issue may be KPI-2 condenser on a BH2.

Good Luck and see you soon on that thread.

John

seta666
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Re: How important is exact compliance of tube length?

Post by seta666 »

I have seen people adding a machined custom dovetail, does not seem too difficult. A 3D printed one could be easier maybe..

dolmadis
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Re: How important is exact compliance of tube length?

Post by dolmadis »

seta666 wrote:
Thu Mar 18, 2021 8:41 am
I have seen people adding a machined custom dovetail, does not seem too difficult. A 3D printed one could be easier maybe..
If a 3D printed dovetail is possible please share .stl file !!

Who have you seen producing machine custom dovetail to BH2? Thanks

Best, John

seta666
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Re: How important is exact compliance of tube length?

Post by seta666 »

dolmadis wrote:
Thu Mar 18, 2021 8:45 am
Who have you seen producing machine custom dovetail to BH2? Thanks
PeteM on this thread I started..You can follow the progress there. Once I have it working
I will start a new thread here too.

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