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First thoughts on Mod3C and prime focus

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#1 maxmir

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Posted 16 June 2021 - 10:24 AM

I successfully moved my tube over from the PVS-14 to the Mod3-C housing.

This is doable but you need be mechanical inclined.

I recommend an adjustable O ring tool. I got one on ebay for about 15.00 

 

Insert the gain control with care and wrap with teflon tape as AB nightvision says in their instruction.

This the only tricky part.

 

I also cut new 32 tpi ( C mount ) threads on the PVS14 lens on the lathe. This works but is not for the faint of heart.

Turn down the old PVS 14 thread area down to 0.992-3 inches. Hold on to lens by using afocal coupler in the chuck.

This will prevent crushing the optics. 

 

Now on to observations. The PVS lens works just as well in the Mod3 ( no surprise ). The new threads fit flush to front of Mod3-C housing a 1x.

 

Next I tried prime focus in my friends 30 inch f 4.5 with a Paracor.

The view was dissappointing in that the edge correction was no better than afocal with a Russell 65mm.

In fact with and without the Paracor looked very similar. Need to figure this one out.  Spacing ?

 

Next I tried a Rokinon 135mm camera lens. The is noted lens for astrophoto. It is known to give round stars at the edges of a 35mm frame.

The Mod3 C and this lens give a flat field with tight stars to the edge. It is a bit on the heavy side for hand held use but a great lens none the less.

 

More testing to come. 

 

Max


Edited by maxmir, 16 June 2021 - 10:28 AM.

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#2 chemisted

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Posted 16 June 2021 - 12:20 PM

So if I understand your posts correctly you purchased a PVS-14 from Kosher Surplus because it was immediately available with a good tube.  You then purchased the Mod3-C body from AB Nightvision and cannibalized the PVS-14 for its tube and objective which you installed into the Mod3-C to give a fully functional c-mount NV device.  Is that correct?  I would be very interested to hear its performance in the 30 inch f/4.5 scope, if you have the chance, on M92 and NGC 6229 in Hercules.  A compare and contrast of these two clusters regarding diameters and core structure would be very interesting to me.

 

BTW, great job on the machine shop work!



#3 maxmir

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Posted 16 June 2021 - 01:58 PM

So if I understand your posts correctly you purchased a PVS-14 from Kosher Surplus because it was immediately available with a good tube.  You then purchased the Mod3-C body from AB Nightvision and cannibalized the PVS-14 for its tube and objective which you installed into the Mod3-C to give a fully functional c-mount NV device.  Is that correct?  I would be very interested to hear its performance in the 30 inch f/4.5 scope, if you have the chance, on M92 and NGC 6229 in Hercules.  A compare and contrast of these two clusters regarding diameters and core structure would be very interesting to me.

 

BTW, great job on the machine shop work!

You understand correctly. Kosher cant supply Mod3. 

I got the MOD3 from Nightline INC in Tennessee.

It is expensive to go this way. Housing costs about 650.00. I used all the PVS 14.

I hope to recoup 300 to 350.00 by selling the Carson.

 

If I have chance to observe on the 30 again; I will give you a detailed report. When I get on it again.

It may be tough coming up. Moonsoon rains start around now here in AZ.

It is my friends scope. He is bigger visual observer than I. He writes a lot of articles for S&T. 

His name is Ted Forte. He has an new article this month. He has a PVS14 on order after looking at mine.

I have a feeling he might write about night vision observing when he gets his.

 

I have had a greater focus in astrophotography in the past 20 years.

I have a couple of 12 inches yet to test in my observatory. 

One is an Astrophysics Riccardi Honders F3.8 , the other is a Mewlon 300.

Afocal did not look very good in the Honders.  It will be interesting  to see what prime can do.



#4 chemisted

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Posted 16 June 2021 - 02:29 PM

I have read lots of Ted's articles and have thoroughly enjoyed them. I wrote on NV and globulars back in 2017: S&T July issue, p.57. I referenced one of Ted's articles at the beginning of mine.

Edited by chemisted, 16 June 2021 - 02:36 PM.


#5 chemisted

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Posted 16 June 2021 - 03:36 PM

When you used the 65mm RO Plossl for afocal did you have a 25mm spacer between the eyepiece and the NV device objective?

Edited by chemisted, 16 June 2021 - 03:37 PM.


#6 a__l

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Posted 16 June 2021 - 07:22 PM

I successfully moved my tube over from the PVS-14 to the Mod3-C housing.

This is doable but you need be mechanical inclined.

I recommend an adjustable O ring tool. I got one on ebay for about 15.00 

 

Insert the gain control with care and wrap with teflon tape as AB nightvision says in their instruction.

This the only tricky part.

 

I also cut new 32 tpi ( C mount ) threads on the PVS14 lens on the lathe. This works but is not for the faint of heart.

Turn down the old PVS 14 thread area down to 0.992-3 inches. Hold on to lens by using afocal coupler in the chuck.

This will prevent crushing the optics. 

 

Now on to observations. The PVS lens works just as well in the Mod3 ( no surprise ). The new threads fit flush to front of Mod3-C housing a 1x.

 

Next I tried prime focus in my friends 30 inch f 4.5 with a Paracor.

The view was dissappointing in that the edge correction was no better than afocal with a Russell 65mm.

In fact with and without the Paracor looked very similar. Need to figure this one out.  Spacing ?

 

Next I tried a Rokinon 135mm camera lens. The is noted lens for astrophoto. It is known to give round stars at the edges of a 35mm frame.

The Mod3 C and this lens give a flat field with tight stars to the edge. It is a bit on the heavy side for hand held use but a great lens none the less.

 

More testing to come. 

 

Max

It is not very clear what "Paracor" is.
If this is an old model, you need to to remove the head, install a adapter 2"- M42 and M42-M31-NV (as mine).

If it is P-2, you need to remove the head and install the adapter with 2.4" thread. Further, depending on the type of this adapter.

The distances according to the TV specification must be observed.

The adjusting knobs on the NV can be an obstacle here.


Edited by a__l, 16 June 2021 - 07:45 PM.


#7 maxmir

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Posted 17 June 2021 - 06:43 AM

When you used the 65mm RO Plossl for afocal did you have a 25mm spacer between the eyepiece and the NV device objective?


I sure did. I want to try 30,35,40mm
The 65mm and 85mm have a lot eye relief

#8 maxmir

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Posted 17 June 2021 - 06:49 AM

It is not very clear what "Paracor" is.
If this is an old model, you need to to remove the head, install a adapter 2"- M42 and M42-M31-NV (as mine).
If it is P-2, you need to remove the head and install the adapter with 2.4" thread. Further, depending on the type of this adapter.
The distances according to the TV specification must be observed.
The adjusting knobs on the NV can be an obstacle here.


It is the original. I need to find the spacing specification.

#9 a__l

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Posted 17 June 2021 - 07:04 AM

For prime focus only experiment.
C-mont standard flange focal distance is ~ 17.5 mm. Added to this is a glass tube thickness.
https://televue.com/...id=61&Tab=_phot
TV distance 9 + 47 mm (measured from glass P2)


Edited by a__l, 17 June 2021 - 07:05 AM.



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