Lunt 50 mod. Cut the tube, or buy adapters?

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Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Wed Feb 10, 2021 11:40 pm

Hi all,

So I finally got my 102mm f/7 refractor. I was hoping it being f/7, I would reach focus by just attaching the Lunt module to the focuser M68 thread. Of course it didnt work. I need another 10-15mm

So the big question is; should I cut the tube (cheap! but I change the focal ratio slightly)? Or should I unscrew the whole focuser (don't really need it), add a M84 to M68 adapter and a 40mm extension tube (a lot of money for "nothing")?

What do you guys recommend?



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by MalVeauX » Thu Feb 11, 2021 2:14 am

If you can make it work without cutting the OTA, that would be preferred I assume.

Very best,



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by marktownley » Thu Feb 11, 2021 6:31 am

Post a pic of the setup so can see it, there's always a way!


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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Carbon60 » Thu Feb 11, 2021 7:17 am

As Mark suggests, a picture (or diagram) of what you’re trying to achieve would be helpful.

Sounds interesting though.

Stu.


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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Thu Feb 11, 2021 12:43 pm

See this is the problem when you write stuff at 2AM :P

Pics time!

Image

Image

Image

I just measured my Lunt 50. At F350, does the PT module, focuser and diagonal really make up 162mm (350-188) of that?

Image



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by marktownley » Thu Feb 11, 2021 12:52 pm

Don't cut the tubes - given you have the M84 fixings on the tube go for removing the focuser and using the m84 extension to get the correct spacing, by far the best way!

Mark


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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Thu Feb 11, 2021 12:59 pm

So I don't have to factor in the 162mm anywhere?



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by marktownley » Thu Feb 11, 2021 1:13 pm

Ofcourse. The front lens on the etalon assembly needs to be 162mm ahead of the focal point.


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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Thu Feb 11, 2021 1:43 pm

lol of course! Brain is seriously not working today. But it's almost the weekend! :D

Thanks Mark



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Sun Feb 14, 2021 3:16 pm

Right, I got a bad case paralysis by analysis here... :?

I focused both telescopes just to see where the focus point was (with the same diagonal and eyepiece).
When put next to each other, they seem to focus at more or less the same spot. So, other than the M84-M68 adapter, do I even need an extension tube?
Or will I run into problems with the 20mm etalon by moving it in?

Image
Last edited by Gingerfish on Fri Feb 26, 2021 11:03 pm, edited 1 time in total.



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by marktownley » Sun Feb 14, 2021 4:46 pm

Try it under the sun, what's the worst that can be? you have to buy an m68 extension! :)


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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Sun Feb 14, 2021 5:26 pm

lol true!



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Sat Feb 20, 2021 2:42 am

Right, I need to double check something here, as another solar modder is confusing me!

The 2" Baader 35nm H-a filter goes BEFORE the PT module right? My buddy here says to use it in the diagonal instead, since the Lunt PT module already has a filter in it. Now that is true, but I thought the Baader filter was there to take some of the heat away from the Lunt filter? :geek:

Image



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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Carbon60 » Sat Feb 20, 2021 8:05 am

The Baader 35nm Ha is acting as an energy rejection filter (ERF), so it should go in front of the etalon assembly. I see from the image that you have a few degrees of tilt on this, which is correct as it will help reduce unwanted reflections.

Looks good.

As Mark suggests, give it a try and see what you get. If it doesn’t quite work out you can always have a custom spacer made to achieve the exact positioning.

Stu.


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Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
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Re: Lunt 50 mod. Cut the tube, or buy adapters?

Post by Gingerfish » Sat Feb 20, 2021 12:20 pm

That is what I thought! I guess there is more than one way to do it. Obviously having a filter in the diagonal works for him!

Cheers Stu!



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