Final Assembly LUNT 60 mm Pressure tuned MOD

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solarmax2016
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Final Assembly LUNT 60 mm Pressure tuned MOD

Post by solarmax2016 » Fri May 12, 2017 6:15 pm

Just finished construction of a 60 mm Pressure tuned Lunt MOD fitted to a Meade 102ED refractor, Turned out exceedingly well. If you try to construct this keep in mind that you must know your objective focal length and most important that it has a long focus outreach (in the vicinity of at least 10 or
11" ) which the older meade series ED scopes possessed. It relies completely on Moonlite adapters which not only help to assemble it but MAKE IT QUICKLY REMOVABLE to interchange with a Regular Moonlite focuser (by dovetails). Thus you have a perfect White light (with Herschel Wedge) or H-alpha telescope all in one package. Attached are construction diagram and photo of completed assembly in my observatory. I went the extra mile to anodize the aluminum tubing and the machined down parts (I live near an aerospase anodizer). Hope you like it - took 7 months of trial and error and a fair bit of cash to achieve this beautiful baby. I'll send images once the jet stream clears up in Canada - lousy seeing for weeks. John
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by solarmax2016 » Fri May 12, 2017 6:29 pm

Just one added diagram you need for the 60 mm PT Lunt MOD conversion - the assembly diagram. If you follow this the only variance will be your focal point and thus the length of the tubing between the two Moonlite Adapters. Moonlite was very helpful in this construction and no other way could you build this without high-priced machine costs. The focus thread alone is a 1 mm micro - hard to cut on normal lathes. Its all worth the effort when you hold this baby in your hands - first impressions were - the chromospheric detail was as good as LUNT's 100 mm PT scope, so for at least $6000 less you are quite up to par with the most expensive diameters. John

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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by solarmax2016 » Fri May 12, 2017 6:33 pm

Sorry about the diagram - bytes were too big. Here is a lower byte diagram. John
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by GreatAttractor » Fri May 12, 2017 6:48 pm

Great work! Judging by my own experience, this should perform very well. Looking forward to some solar shots.
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Sat May 13, 2017 12:50 am

Looking good!
When you achieve first light and the assembly is confirmed. I'd recommend adding this to the Library.
Ken
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by marktownley » Sat May 13, 2017 9:18 am

Very nice!
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Sat May 13, 2017 3:24 pm

John,
Hmmmm may be your numbers are not correct...
The LS60 etalon is 35mm diameter and the "majic" number I think is not what you show.
Check out:
viewtopic.php?f=9&t=546
The 2012 investigations....
Lunt60_sketch_own2.gif
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"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Mon May 15, 2017 12:07 am

Further checking....
What we know:
1. The collimating (barlow) is positioned at the "majic" number - the distance inside the prime focus to give a parallel collimated beam to the etalon.
2. The rear re-imaging lens provides a fixed distance to the final focus.

So, a quick check on the accuracy of any mod would be: With the original assembly focus the sun, lock the focuser and camera/ eyepiece so there is NO possibility of movement. Remove the OTA and re-fit the mod section to the new donor (with ERF) and re-check that the sun is still in focus. There's NO change to the back focus due to the mod. If the sun is not in focus, then the positioning of the front collimator (barlow) is not at the "majic" spacing. Re-adjust until success.

For the Lunt 60 the "known" dimensions seem to vary.....
The etalon is effectively 35mm diameter.
It does appear that the objective is a 60mm f 4.8 lens, focal length 275mm(?) The final effective fl is 500mm therefore the rear re-imaging lens is not exactly (?) the same focal length as the collimator (barlow) giving a 500/275 = x 1.8 enlargement.
It also appears that the collimator is positioned at 164mm (?) behind the objective, this then infers that the "majic" spacing is 175-164 = 111mm
It seems that any donor >f4.8 would be good.
lunt60-design.jpg
lunt60-design.jpg (456.74 KiB) Viewed 1579 times

It would be good for the community to be able to "lock in" more accurate data - this is an important mod opportunity!!!
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Valery » Mon May 15, 2017 7:07 am

I have a great doubt that this mod will work fine. The problem is that Lunt 60mm optical system has been designed as straight through system when the system works properly only with all it's elements.
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Mon May 15, 2017 10:44 am

Valery,
Not sure I understand your comment.......
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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"Astronomical Spectroscopy for Amateurs" and
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Valery » Mon May 15, 2017 11:09 am

Merlin66 wrote:
Mon May 15, 2017 10:44 am
Valery,
Not sure I understand your comment.......
The Lunt 60THa PT is quite different to, say, Lunt 80THa PT. In the 60 model all three lenses works together.
And two collimating and focusing lenses also compensite aberrations of the singlet objective.
This system has, for example, corrected spherical aberration at 656nm. If to use these lenses with another objective
(say, a corrected doublet objective) then it will overcorrect a spherical aberration of this objective and images should
be soft. Collimation-refocusing systems from LS80 and LS100 can be used with another objectives which are more
or less corrected for SA.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by GreatAttractor » Mon May 15, 2017 8:43 pm

I'm afraid Valery has a point. I was under the impression that only the old version of Lunt 60 used a singlet objective, but apparently it's still true. As Valery wrote, this will likely give less than optimal results after attaching to a regular achromat.
My software:
Stackistry — an open-source cross-platform image stacker
ImPPG — stack post-processing and animation alignment
My images

SW Mak-Cass 127, ATM Hα scope (D=90 mm, LS50 etalon), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)

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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Tue May 16, 2017 12:10 am

Valery,
Thanks for that....
Yes, the under/over corrected SA may be an issue - but the results will show if the problem impacts on the results........
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by marktownley » Tue May 16, 2017 5:04 am

As with anything in solar, it's all about compromise, and a mod like this is about getting more aperture for the money with spending the money of the full scope equivalent. SA may be an issue to a greater or lesser extent, as may be the smaller sweet spot (relative to say the Lunt 100), similar compromises would also be had putting a PST etalon on the back of an SCT, for which it was not designed. At the end of the day if you are happy with the results is what counts.
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Valery » Tue May 16, 2017 6:01 am

marktownley wrote:
Tue May 16, 2017 5:04 am
As with anything in solar, it's all about compromise, and a mod like this is about getting more aperture for the money with spending the money of the full scope equivalent. SA may be an issue to a greater or lesser extent, as may be the smaller sweet spot (relative to say the Lunt 100), similar compromises would also be had putting a PST etalon on the back of an SCT, for which it was not designed. At the end of the day if you are happy with the results is what counts.
Hi Mark,

Yes, compromises rules. But to a limited degree.

1. At the very center of the SCT field where the PST's sweet spot is still useable, the SCT aberrations correction is quite good.

2. The difference in SA between achromat 40mm F/10 and 150mm F/10 is MUCH MUCH less than between 60mm F/5 singlet and 100mm F/10 achromat. In tens times.

3. Happiness can quite vary.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by Merlin66 » Sat May 20, 2017 6:55 am

John,
Have you had the opportunity to test your mod??
These discussions are interesting but the proof of the pudding is in the use.....
Look forward to seeing your results.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: Final Assembly LUNT 60MOD mm Pressure tuned MOD

Post by solarmax2016 » Wed Jul 05, 2017 1:28 am

I guess its time I showed some of my images taken with the new 60 mm PT Ha MOD coupled to a Meade 102ED Apocromat. The interesting thing about
this construction I came up with is that it is constantly tunable - just be rotating the whole Etalon assembly around its 1 mm micro thread attaching it to
the Meade OTA barrel. I also discovered that if I necked down the 100 mm ERF to 80 mm I lose almost ALL the off-band information. The LUNT product
is very mysterious largely because its collimator is f/2 according to Brian at LUNT which makes it hard to work with in such a short focal distance. He did
not think I could achieve what I have done. Anyway here are a few examples taken with a DKK41AUO on bad seeing days. I may try the same attachment to an 80 mm Orion achromat with a shorter focal length (similar to LUNT's). I have an idea that the focal length plays as large a part in the resolution as much as f/ratio. All it needs is a Moonlite upper flange (which I now have) attached to the OTA of the ORION instrument and I'm away - the same extension just set-screws onto the dovetail - I just love the way Moonlite makes this stuff - its so easy to marry with anything else you use. Well worth the cash outlay, and the finishing is just first class. I'm very pleased with this new instrument and it looks sharp too.
John
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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by solarmax2016 » Fri Jul 14, 2017 3:31 am

Has anyone tried to add a telecentric lens (such as an Astrophysics telecentric) directly in front of the LUNT 60 mm Ha Pressure-tuned assembly in a MOD
position? (i'e. like mine on the rear of a Meade 102ED)? Effectively doing what we used to do with Del Woods original Daystar Ha filters, straightening out
the wave bundles before they enter the filter. Lunt used to tell me that off-band wave bundles were caused by reflection off the Daystar Cowling on the
face of the Daystar producing blurred and over-exposed blotches across the field. - he always insisted that is why he made front-mounted etalons to get
perfectly parallel light in his objective-mounted scopes. Any ideas? Is it effectively scrambling the beam because the collimator attempts to straighten out the cone inside the LUNT filter itself - thereby adding two collimators - one in front of the other?

John

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Re: Final Assembly LUNT 60 mm Pressure tuned MOD

Post by marktownley » Fri Jul 14, 2017 5:11 am

It will work in theory putting a lunt etalon in a telecentric beam instead of a collimated beam. There are however 2 issues to overcome; the first mechanical in the sense the front and rear collimating lenses in the assembly act as a pressurised gasket seal, this could be done by replacing them with optically flat glass. Secondly is a little more difficult to work around; an air spaced etalon (as a system) has quite a different refractive index than a solid etalon (like a daystar) and as a result when an airspaced etalon is used in a telecentric system the result is it has a considerably wider pass band than when it is used in a collimated system. This is why the different etalon manufacturers use the respective systems they do.
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