Lunt LS100Tha Double Stack

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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Re: Lunt LS100Tha Double Stack

Post by Highbury Mark »

Excellent! And what a day to get your first view of proms through the SM90 - today was quite a show. Good idea to try in single stack first. I have to wait a little longer for my new set up, but glad you had a great first light


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Re: Lunt LS100Tha Double Stack

Post by Solar B »

The big gold scope looks great ... I think your gonna have a lot of fun with it.

I'm most jealous again 👽 :mrgreen:

Brian

Hang on though I think you can only use the factory DS Coronados in DS mode (not SS)

as the internal etalon does not have an ERF ... I'm sure this is the case with my SM60IIDS

but the advantage of these set ups is that they offer much brighter DS views than

those using 2 ERF ( in DS mode you only require one ERF )

Brian


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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

I read that the ERF to the internal etalon is in the coatings on the refractor’s objective lens in a similar fashion to the AiryLab HaT ERF coatings on the corrector lens of their Celestron SCTs. I cannot remember where I read that. But it makes sense and legally they could not sell something unsafe and plus a lot of people buy and observe with the Coronado SS scopes. SS often does better with prominences. I think the blocking filter also has some ability to block IR/UV energy.


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Re: Lunt LS100Tha Double Stack

Post by Solar B »

I'd prefer some clarification on that ... there are clear objectives with ERFs by other manufacturers

but I recall reading on CN 10 years ago or more that some of the factory

DS Coronados did not have an ERF to the internal scope , around this time they were switching

from 2 external to 1 internal & 1 external etalon and one could send the scope back to Coronado

to have an internal etalon installed ( this being before the introduction of the SMII)

It could be the ERF is further into the scopes assembly to like a PST , however I've always

just used mine in DS mode as is my preference and the BFs are

trimming filters that will only omit 656 nm.

However having said all that looking at the Coronado manual again there is nothing to suggest that

you cannot use the scope in SS mode.


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Re: Lunt LS100Tha Double Stack

Post by Montana »

:hamster: :hamster: :hamster: :hamster: :hamster:


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Re: Lunt LS100Tha Double Stack

Post by marktownley »

Solar B wrote: Tue May 05, 2020 10:59 pm Hang on though I think you can only use the factory DS Coronados in DS mode (not SS)

as the internal etalon does not have an ERF ... I'm sure this is the case with my SM60IIDS

but the advantage of these set ups is that they offer much brighter DS views than

those using 2 ERF ( in DS mode you only require one ERF )
If there was any concerns it would say in the instruction manual. You're talking about the older SMi series Brian, this is one of the newer versions of the SMii series - dull annealed tube opposed to brass tube. Mine is one of the older versions of the SMii series and that has no ERF (internal or external) and brass tube. The manual with doesn't state anything about it being unsafe to use in single stack configuration.


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Re: Lunt LS100Tha Double Stack

Post by Solar B »

I'm none the wiser Mark ?

Yes I recall the original otas were brass , mine is the newer (cheaper) finish , so where abouts

in the assembly is the ERF ... as they are obviously normally red or have a mirrored finish ,

you say yours is an older SMII or is it an SMI without ERF to the OTA so I take it this means

it's a DS configuration only 🤔

I'm just trying to establish where the ERF is ... as stated there is nothing in my manual

to suggest it is unsafe in SS mode 🤷

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Re: Lunt LS100Tha Double Stack

Post by marktownley »

The purpose of the red (RG630) ERF on the double stack unit is to keep it thermally stable and stop it going off band. There is no RG630 in the ota of the Coronados, the main lens may have some coating - don't know without testing, i'll get my hand held spectroscope on the case later on if I get the scope out.

So, light goes through objective and then next thing it goes through is the etalon, this produces a series of constructive and destructive interference which reduces throughput. There's the numbers for this somewhere on the forum on a thread, can't remember where without having a good search. The Blocking filter (ITF and blocker itself) then acts as the final line of filtration.

My scope is the SM90ii, this very one https://www.skyatnightmagazine.com/revi ... telescope/ (with quite a few mods from me now).


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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

Yours is an earlier model II. It looks like it still has the brass anodized OTA. While I like the color of mine, not sure if it is some kind of duller anodization or more likely a good powder-paint coating I like the shiny brass tube better. It's more polished...get the pun???.. :)


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Re: Lunt LS100Tha Double Stack

Post by Solar B »

I see Pete tested it Mark (he used to image with an DSSF70 as I recall) beautiful scope !!

Funnily I read this review only last week as was considering one

Yeah the stand alone SMII 60/90s OTAs do not have the red rg630 erfs but must have

a means of rejection , if you can check your 90s objective that would be great.

Some of the solarscope objectives did not have sufficient IR blocking as they would go

off band if tracking for a couple of hours as my SV50 used to ... Bob did however highlight this

to Ken some time ago (where is Bob these days ?)

It's ok I've just gotten my head round the interference process , plate flatness and parallelism

Probably will need someone to explain the FWHM graph to me again

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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

I found a review of an earlier model Coronado SolarMax II by Stephen Ramsden. The only visible difference I see in this scope and mine is that this one still had the brass anodized tube. Mine has the powder-painted golden tube finish. He does mention the objective having an ERF coating on it.

http://www.stephenramsden.com/solarastr ... -10-23.pdf

James


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Re: Lunt LS100Tha Double Stack

Post by marktownley »

Solar B wrote: Thu May 07, 2020 10:20 am if you can check your 90s objective that would be great.
Ok, so I checked yesterday the scope with a hand held spectroscope. Visually there was no difference with the spectrum through the scope and the spectrum of the sky. So, I would suggest any blocking that may (or may not) exist is out of the visible spectrum range. Looks like all blocking is done by a combination of the etalon itself and the blocking filter unit.


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Re: Lunt LS100Tha Double Stack

Post by Solar B »

Thanks Mark .. I doubt the etalon itself would reduce the transmission enough by bouncing it

around having to cope with that kind of intensity ... I was thinking the erf could be by the BF like the PST

but of course the SMs are all in a regular diagonal format .. I reckon I'll stick with the 60 in DS mode

for the time being.

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Re: Lunt LS100Tha Double Stack

Post by marktownley »

They would be safe else coronado wouldn't sell them. Does show the importance of making sure the ITF in the blocker if replaced is replaced with an ITF and not a 7 or 35nm Ha filter, as there would be little or no blocking above about 1500nm.


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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

Could an 1.25" eyepiece mounted UV/IR filter be used to give one added protection from UV/IR wavelengths visually at the eyepiece?


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Re: Lunt LS100Tha Double Stack

Post by marktownley »

DeepSolar64 wrote: Sun May 10, 2020 6:55 pm Could an 1.25" eyepiece mounted UV/IR filter be used to give one added protection from UV/IR wavelengths visually at the eyepiece?
Absolutely yes


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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

I will certainly get one of these. Any suggestions?


Lunt 8x32 SUNoculars
Orion 70mm Solar Telescope
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Meade Coronado SolarMax II 60 DS
Meade Coronado SolarMax II 90 DS
Meade Coronado AZS Alt/Az Mount
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Losmandy AZ8 Alt/Az Mount
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Re: Lunt LS100Tha Double Stack

Post by marktownley »

I use a Baader, but any of them should be fine, just double check the transmission is up at 656nm.


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Re: Lunt LS100Tha Double Stack

Post by DeepSolar64 »

Thanks Mark!


Lunt 8x32 SUNoculars
Orion 70mm Solar Telescope
Celestron AstroMaster Alt/Az Mount
Meade Coronado SolarMax II 60 DS
Meade Coronado SolarMax II 90 DS
Meade Coronado AZS Alt/Az Mount
Astro-Tech AT72EDII with Altair solar wedge
Celestron NexStar 102GT with Altair solar wedge
Losmandy AZ8 Alt/Az Mount
Sky-Watcher AZGTI Alt-Az GoTo mount
Cameras: ZWO ASI178MM, PGR Grasshopper, PGR Flea
Lunt, Coronado, TeleVue, Orion and Meade eyepieces

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