Lunt modular scopes on sale in UK

[Highburymark]

Notice that Telescope House has the new Lunt modular scopes on its website - first time I’ve seen them on sale in Europe. Price of LS60 with the 1200 blocking filter is a few quid short of £3k. So a premium of £300-£400 over the outgoing model. The advantage being of course that you also get an FPL51 ED doublet for night or white light viewing. Not cheap, but perhaps better value as a more flexible package than the dedicated solar scopes.

[johninderby]

Solar scopes are just gerting more expensive. Like the idea of the modular version though.

Wonder how many of these Telescope House will be selling? 🤔

[Peter Drew]

There are much more affordable options if you need that sort of aperture.     🙂

[vlaiv]

I'm sort of being dumb here.

This is the image of the item:

Can anyone explain how this works?

From image, it is obviously sub aperture etalon. That means it needs to have some sort of negative lens in front of etalon and positive lens behind etalon in order to collimate light beam for etalon to be efficient.

How does one remove all of that and why does the text say it is 60mm aperture for Solar and 70mm aperture for nighttime use?

If it is indeed front mounted etalon - which would explain everything above - will it indeed be pressure tuned?

[Davey-T]

Guess you just remove the pressure tuner, the red and black bit in the  middle, rear lens is in the blocking filter not fitted in the picture not sure how you regain the focal length ?

Dave

[vlaiv]

Ok, this is interesting - to answer my own question - indeed - very modular:

This is same scope with Ha etalon (assembly should I add) - removed.

Anyone seeing PST style mod in the making? Just a F/6 donor scope and some machining?

[vlaiv]

1 minute ago, Davey-T said:

Guess you just remove the pressure tuner, the red and black bit in the  middle, rear lens is in the blocking filter not fitted in the picture not sure how you regain the focal length ?

Dave

This is actually very easy thing to do. One just needs to pair negative and positive lens element. Here is simple ray diagram:

Negative lens element needs to be placed at specific distance from focal plane - it's own focal length and it will create parallel rays. Parallel rays are ideal for etalon to do its job, and after one just needs to put another small doublet (like 50-60mm) to bring rays to focus.

I guess that red thing with pressure tuner is etalon together with two suitable lens - front negative and rear positive lens. Such assembly can do the same job on any F/6 scope (if original 70mm lens is F/6 to have 420mm FL), if placed at proper distance from focal plane.

 

[johninderby]

Here’s the manual. 🙂

https://www.bresser.de/out/media/a16d54845c5469b523b890c66e38d14c.pdf

Edited September 28, 2020 by johninderby

[Highburymark]

Not sure there are any new modding opportunities with this range - Lunt’s been making removable internal pressure tuned etalons for years - though they are double stack units (for the LS80 and LS100.)

[vineyard]

13 minutes ago, vlaiv said:

Such assembly can do the same job on any F/6 scope (if original 70mm lens is F/6 to have 420mm FL), if placed at proper distance from focal plane.

 

That's the thought that struck me too!  I have a Lunt50 and have already assembled a mod that allows me to take that OTA off, thread a 2" nose (that looks exactly like the nose on the red etalon in John's picture above) on that allows me to then attach it as if it was a diagonal.  Its worked with a a 4" frac, but becomes a bit of a long frankenscope.  Just struck me that I can do that with my little Primaluce 72ED (f6 exactly like you say, FPL51).  I only have the helical focuser though, so I really need to change that but the UK/Europe prices for those are ridiculous so I'm trying to be patient.  I do get some NR but am getting a tilt adjuster 🤞🏾

[EDIT: here's the link to a more detailed writeup w photos - pls forgive the awful solar photo - my PP skills were even worse then & also the footage was taken on an alt-az]

Btw I think the sort of 72ED modding that @vlaiv suggests would also fit within the weight limit of a Solarquest mount (just about)?

Edited September 28, 2020 by vineyard
added link

[Highburymark]

2 hours ago, vineyard said:

 

Btw I think the sort of 72ED modding that @vlaiv suggests would also fit within the weight limit of a Solarquest mount (just about)?

Those little SW mounts are pretty robust - I’ve had scopes over 6kg on mine and it’s been great.