Lunt 60 - 127mm mod

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
Post Reply
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

I guess the answer is try it with regards the stray light, see if it works. Never tried it myself in an open tube configuration so I don't know.

The mechanics of your drawing will be fine I think.

Regards the f- ratio thing. If the f-ratio is less than that of the collimating lens then there will be vignetting - by my calculations you'll be running at an effective aperture of ~100mm if the collimating lens on the Lunt is f7.5. You may also have issues with the bandpass getting wider across the fov as you get towards the edge, and also the bandpass shifting towards the red as you also get towards the edge of the fov. Basically the centre of the fov will show more detail than the edge.

You can work out how far the 127mm lens needs to sit in front of the Lunts collimating lens - my calcs put it at 543mm.

Also, you will need to unscrew the objective from the Lunt OTA...

Mark


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

that is a very fine project. I did something like that 2 years ago and found that it helps if you add another ground plate on top of the "scope" in order to have a firm constellation which is not flexing too much. You can add very easely aperture stops down the light train if you have problems with straylight


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

that is a fantastic construction. It's the way to go. Good luck


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

sexy time 8)


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »

http://solarchat.solarastronomy.org/ind ... unt-etalon
See message #6249 for a summary....

The lunt objective seems to be around f4.5, so f5 should be OK. Check the distances..
Your set up is no different to an optical bench set-up - it will work. If needs be a black cloth will suppress any reflection issues...give it a go.


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »

The 125 objective wil be pumping 430% more energy into the system....
Me, well I'd play it safe and have an ERF as close to the objective as possible.
You can always use a temporary aperture stop say, 70mm to test out the system.....


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »

Do what Ralph did...just cut an aperture stop from some cardboard and give it a go!!!


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Definitely use an ERF ;)


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »

Onwards and Upwards!
I'm 100% sure you'll get there.


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

that lens looks good, very good ;-)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

that depends only on your skill, not on the lens :lol:


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »

John,
I know from Viljo's Lunt 60 mod that it can and does work!

Valery on another thread raises the issues of aberrations in the Lunt single objective being corrected by the front barlow in the etalon assembly, and when used with a doublet - overcorrects...


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
Merlin66
Librarian
Librarian
Posts: 3970
Joined: Tue Dec 13, 2011 1:23 pm
Location: Junortoun, Australia
Has thanked: 173 times
Been thanked: 615 times
Contact:

Re: Lunt 60 - 127mm mod

Post by Merlin66 »



"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Great scope you and your father made John! :)


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Hi John, apologies for the slow response.

Okey dokes, if you look at the collimating lens in front of the etalon on the Lunt 60 (I think) it is 35mm diameter. So, the object of what we're trying to achieve is to position it so that it intercepts a light cone of the same diameter from the 127mm lens. We can work this out using similar triangles; i'll assume the Lunts collimator is 35mm but you should easily be able to substitute other numbers if it is not.

35/127 = 0.276

0.276 x 700mm = 193mm

So we want to position the lunt collimator 193mm inside the focus of the 127mm lens. But there is an easier way to do this - measure backwards from the back face of the 127mm lens. So, 700mm - 193mm = 507mm... This is the (approximate) gap you will need between the back of the 127mm objective and the front face of the Lunt collimating lens. You will want to have some ability to wiggle this distance a bit - it's only approximate, but it should put you somewhere in the right ball park.

Mark


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Yup, 40mm looks like it would work. Just don't unscrew any of those retaining rings, I guess they hold the pressure on the etalon...


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

yes that silicone rubber compound was here too on the threads of the CaK wedge ;-)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

such is life ;)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

Looks great, do I know the lens ;) , looking forward to your first lights


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Looks good there John! I look forward to first light :)


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
Carbon60
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 14209
Joined: Wed Mar 07, 2012 12:33 pm
Location: Lancashire, UK
Has thanked: 8418 times
Been thanked: 8162 times

Re: Lunt 60 - 127mm mod

Post by Carbon60 »

Looking good, John. All primed and ready.......

Good luck with your first light.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
User avatar
GUS
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 1298
Joined: Thu May 08, 2014 12:03 pm
Location: Katoomba,NSW,Australia
Has thanked: 102 times
Been thanked: 213 times

Re: Lunt 60 - 127mm mod

Post by GUS »

Great looking mod John, looking forward to first light.

GUS.


User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17948
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Been thanked: 1 time
Contact:

Re: Lunt 60 - 127mm mod

Post by swisswalter »

Hi John

fantastic. eager to see the first lights


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Have you got the ERF the wrong way round? One side has the UV/IR coating on, one side does not. Try reversing it and see what happens...


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
Carbon60
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 14209
Joined: Wed Mar 07, 2012 12:33 pm
Location: Lancashire, UK
Has thanked: 8418 times
Been thanked: 8162 times

Re: Lunt 60 - 127mm mod

Post by Carbon60 »

John,

My internal 90mm ERF reflects back through the 150mm objective roughly mid-way between the centre and the edge. Initially I had it tilted too much in my opinion and the reflected heat was impinging on the inside face of the OTA at the rim of the objective. I reduced the tilt purposely to 'let the heat out' as it were.

Clearly, it goes without saying, care has to be taken with the now focussed reflected beam!

I don't know if this will help, but I always have a polarising filter fitted to the nose of my camera so that I can rotate to kill any reflections. My new mod doesn't seem so affected as the original version, but I've left the polariser in place anyhow.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

It's the relative distance of that internal ERF compared to everything else then - just gotta play around with it...


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Asimov wrote:What about the fact that it's running 2 internal ERF's Mark? Reckon the 2 are interacting somehow?
Quite possibly, wouldn't surprise me.


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20438 times
Been thanked: 10245 times
Contact:

Re: Lunt 60 - 127mm mod

Post by marktownley »

Noooo, definitely don't start taking anything off the 60...


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
MapleRidge
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 10199
Joined: Fri Jan 13, 2012 11:58 pm
Location: Cambray, ON Canada
Has thanked: 64 times
Been thanked: 4340 times
Contact:

Re: Lunt 60 - 127mm mod

Post by MapleRidge »

Hi John...

The modded system looks good...hope you have a successful first light!

Brian


Brian Colville

Maple Ridge Observatory
Cambray, ON Canada

Photos: https://www.flickr.com/photos/185395281@N08/albums

10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
Deep Sky Work - ASI294MM Pro+EFW 7x36/Canon 60D (Ha mod), ONAG
Planetary Work - SBIG CFW10, ASI462MM

2.2m Diameter Dome
iOptron CEM70G Mount carrying:
Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
ASI1600MM, ASI432MM, ASI294MM Pro, ASI174MM, ASI462MM
Post Reply