Show me your lunt solar mods

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...
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marktownley
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Re: Show me your lunt solar mods

Post by marktownley » Mon Oct 09, 2017 6:52 pm

I think there's a few people know who've done a variant with different scopes on what you're wanting to do so there will be plenty of info on here. You should be able to 3D print a reducer for your focuser, just go for a dense fill. Where abouts in the west midlands are you?
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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!

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marktownley
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Re: Show me your lunt solar mods

Post by marktownley » Mon Oct 09, 2017 8:08 pm

Should be a pretty straight forward mod. Let me know if you find anywhere local to mill the ali.

Mark
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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!

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GreatAttractor
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Re: Show me your lunt solar mods

Post by GreatAttractor » Thu Oct 12, 2017 5:23 pm

Here's mine, works very well: viewtopic.php?f=9&t=19238
Most of my solar images since then have been captured with this setup.
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)

Macavity
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Re: Show me your lunt solar mods

Post by Macavity » Sat Oct 14, 2017 2:12 am

I have added a few practical details re. the making of my Lunt50 / SW ST120
86mm Frankenscope now. I acknowledge the ideas & encouragement of others! :)

viewtopic.php?f=9&t=23187

No skilled machinist *immediately* on hand here either. But sometimes easier
to make a "prototype" to get the "Engineering Drawing" into acceptable form? ;)

Chris / Macavity (SGL)

Macavity
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Re: Show me your lunt solar mods

Post by Macavity » Mon Oct 16, 2017 9:06 am

Hi SB! :)

There is e.g. a convenient EU source of 100mm Lunt ERF's at Teleskope Service (DE)?
https://www.teleskop-express.de/shop/pr ... ilter.html

There is a slight "flaring" of the ST120 lens cell to give a canonical 120mm.
But the internal diameter of the ST120 OTA is indeed about 112mm too! :|

However, this being my *first ever* Frankenscope, I decided to "stick with the rules" in the design. Since I was upgrading the Lunt 50 *BF600* version, I decided to go with a f=600mm Donor scope. You can calculate light cone width at the blocking filter, but I decided to stay within the quoted limits! That limit fixed, I followed the general advice to stick with the Lunt f/7 light cone. Solar scopes use lenses to paralellise then restore this before / after passing it (parallel) through the Etalon etc. This also fixes things to f/7 and an objective aperture to 86mm! Ergo my 90mm Baader ERF. :)

Whatever the *individual* experience, it is anecdotal that mounting the ERF internally may give rise to tube currents? But simply it is *easier* to mount the thing on the front of the scope! lol. You may sacrifice some (potential) aperture, but I also checked out the (Ronchi Tested!) *optical* performance of Bresser / Skywatcher Achromats. I looks like they work best in green light and may suffer some spherical aberration at H-Alpha wavelength? :shock:

I tried a few ad-hoc tests of my ST120 and concluded the performance of the objective WAS better using a (green) Solar Continuum than a (red) standard H-Alpha (nighttime) filter. It is (as ever) far easier to focus a white light scope using a GREEN filter! But stopping down a faster objective down a bit from full aperture would not hurt things? I decided to be content with an externally mounted ERF - An 86mm H-Alpha seemed a FAIR upgrade! :cool:

It is not a *Full Disk* Solar scope. I checked that out too... Vignetting, non-uniformity of tuning (sweet spot) limits it. BUT it does give some encouraging *Barlowed* images. Overall I am pleased and excited by the result of this. On my limited budget, it is all totally FINE by me! I have some vague notions of upgrades. A BF1200 + greater aperture? Use the ERF inside the tube? Like Dogs and CATS, an ERF is "for life"! :mrgreen:

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