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Re: lunt 50 mod

Posted: Thu Jul 05, 2018 7:20 pm
by krakatoa1883
A very interesting discussion as I am also considering a LS50 mod. I have few questions if someone would be so kind to answer:

1. I assume the mod is fully reversible that is I can have back the original LS50, am I correct ?
2. Is the red cylinder with the PT knob simply screwed to the LS 50 white tube ? can they be separated easily ?
3. Which M68 adapter would I need for attaching the LS50 rear part to the telescope ? has this part a male or a female thread ?
4. I have seen in the above image a Coronado BF replacing the Lunt diagonal, is this replacement necessary ?

Thanks in advance

Re: lunt 50 mod

Posted: Tue Sep 04, 2018 10:35 am
by antonello
After a long time, during which no one knew if the Lunt 50 had a lens with a single lens or an achromatic lens, I discovered from this image
lunt 50.jpg
lunt 50.jpg (236.86 KiB) Viewed 5592 times

that even the Lunt 50, like the Lunt 60., seems to have a objective with single lens, and therefore the use of the Etalon of the Lunt 50, together with the two lenses of its collimator, used on a new telescope with an big achromatic objective, will not allow to obtain, in h-alpha, all the quality of the new big achromatic lens ... :(

Re: lunt 50 mod

Posted: Thu Feb 07, 2019 2:17 pm
by solarchatted
Hi
What an interesting discussion.
I am newbie on Solar and still deciding if to get a PST new [second hand is rare to find they go like cakes - obviously affordable!]
But I have been thinking to jump forward and get a Lunt 50 and then 'in the future - not now' possibly modify it to use on my AR152 988mm F/6.5.
What do you think - experts?

I am getting older and Solar would be an 'easy' addition for later years.

For now I am going to play a bit with White light only - just to get the hang of it again.

Thanks for your time

Re: lunt 50 mod

Posted: Fri Mar 01, 2019 5:58 pm
by GreatAttractor
antonello wrote: Tue Sep 04, 2018 10:35 am even the Lunt 50, like the Lunt 60., seems to have a objective with single lens
Hmm, interesting. Where does the image come from? I just double-checked my specimen (purchased in 2015) and it seems to have a doublet. I mean I didn't disassemble it, but it shows two upright minified reflections of my phone's LED when I hold it close, the same as my 90 mm achromat's objective.
But I have been thinking to jump forward and get a Lunt 50 and then 'in the future - not now' possibly modify it
Definitely! You will find some successful mods here on the forum. Mine are here and here.

Re: lunt 50 mod

Posted: Sat Mar 02, 2019 7:29 am
by antonello
Hello GreatAttractor
I found this image on internet...
It is not a photograph, is a drawing that can not solve the mystery.
It seems that only Lunt knows if the objective is single or achromatic :-)
The number of reflexes is not significant, even a single lens produces two reflections, like a glued doublet.
I still would like to know if the 60 lunt and the Lunt 50 have a single or achromatic lens.
You can easily solve the mystery without disassembling the lens by looking at a tree far away with your Lunt 50 without the etalon mounted. Can you do this? Thank

Re: lunt 50 mod

Posted: Sat Mar 02, 2019 8:46 am
by marktownley
Lunt50 is a doublet.

Re: lunt 50 mod

Posted: Sat Mar 02, 2019 10:35 am
by krakatoa1883
I disassembled my own for cleaning, it is a cemented doublet (front is positive, rear is negative).

Re: lunt 50 mod

Posted: Mon Mar 04, 2019 7:44 am
by antonello
Hello,
many thanks for the information.
Therefore the Lunt 50 Ha has an achromatic objective, and the image I posted was misleading. On the contrary, the lunt 60 Ha has a single lens
lens, as it is clearly written in this image
lunt_60.jpg
lunt_60.jpg (207.79 KiB) Viewed 5241 times
Some time ago I wanted to buy a Lunt 60 Ha to use it to see whole sun in Ha, and cannibalize it, using only the etalon group, on a large diameter achromatic. I did not buy it because I saw an image in which it seemed to have a objective with a single lens. I have then thought of buying a
Lunt 50 Ha, but I did not do it for the same reason.
I still wanted to get the same result and bought a Lunt 35 secondhand. I checked that this tool was little more than a toy and I worked to get something better.
With the Lunt 35 etalon I obtained a "Lunt-Zeiss 50", using a Zeiss achromatic lens 50 mm, f: 540 mm (teleminor) and two simple lenses from catalog for the collimator (-300 mm and +300 mm).
This is the result
lunt-zeiss_50.jpg
lunt-zeiss_50.jpg (117.73 KiB) Viewed 5241 times
The etalon group thus obtained can be placed on any telescope f: 10 approximately. I use it often on a Tal 100, when I want to see the protuberances in detail.
This is the instrument
lunt-tal_100.jpg
lunt-tal_100.jpg (265.21 KiB) Viewed 5241 times
I am very happy with the result.

Re: lunt 50 mod

Posted: Mon Mar 04, 2019 12:03 pm
by marktownley
That's a sweet setup!

Re: lunt 50 mod

Posted: Tue Mar 05, 2019 12:27 pm
by antonello
If it can interest someone ...
Here are the individual lens of 42 mm diameter f: -300 and f: +300 in my etalon Lunt 35.
lunt_35_mod.jpg
lunt_35_mod.jpg (284.28 KiB) Viewed 5220 times
Here is the simulation of the quality of this collimator with three different objectives.
Perfect lens 50/540
1_perfect_lens_50_540.jpg
1_perfect_lens_50_540.jpg (152.9 KiB) Viewed 5220 times
edmund50/500 achromatic lens
2_edmund_achromatic_50_500.jpg
2_edmund_achromatic_50_500.jpg (185.03 KiB) Viewed 5220 times
Single lens 50/500
3_single_lens_50_500.jpg
3_single_lens_50_500.jpg (167.53 KiB) Viewed 5220 times
We can do a reverse test.
Let's take the "telescope-optics.net" single lens Ha solar telescope, diameter 100 mm f:850 mm, with collimator for etalon,
https://www.telescope-optics.net/specia ... scopes.htm

This is the quality of this single lens telescope
4_lens_sistem_telescope_optics.jpg
4_lens_sistem_telescope_optics.jpg (161.42 KiB) Viewed 5220 times
If we now remove the single lens and put a perfect lens (apo or achro is similar), 100 mm f:1000 mm, we get a very bad quality
5_perfect_lens_100_1000_with_collimator_for_simgle_lens.jpg
5_perfect_lens_100_1000_with_collimator_for_simgle_lens.jpg (158.12 KiB) Viewed 5220 times

Re: lunt 50 mod

Posted: Tue Mar 05, 2019 10:11 pm
by marktownley
Interesting spot diagrams, thanks.