Lunt LS80 - Part 1

[Rossco72]

Lunt LS80/PT/FT/B1800

This will be a review in 3 parts. This first part is the unboxing and initial impressions, I will follow this up over the course of the summer with updates on visual use and imaging use as I get to grips with not only the scope but my own learning curve with solar imaging.

So, part one is all about the scope itself, my initial thoughts and impressions and an idea of what you get. I ordered this scope back in early March through Ian King and it’s taken until the end of June to arrive as they come in batches from Lunt in USA. The scope arrived double boxed with an outer shipping box, white Lunt box and inside foam the aluminium flight case containing the scope, a dovetail bar (Vixen style), a Tele Vue Sol searcher and a Lunt 7.2mm – 21.5mm Zoom Eyepiece. Everything you need to get started except a mount. This is a great package by Lunt and others should consider following the same example, there’s nothing worse than buying a bit ok kit and then finding out you need x, y and z extra to use it.

The flight case is a nice solid aluminium job with three latches on the front with locks, not enough to stop a determined thief of course but better than nothing. My one grumble is the fact that once you fit the dovetail and sol searcher the lid doesn’t close. Lunt address this in the manual by stating that the user should cut out a small hole in the top padding once the finder is in place. I think this could have easily been carried out in the design and this seems a bit of a cop out to ask the end user to modify the supplied padding on the first day!

The scope itself is an 80mm ED refractor, at the front end is a metal dust cap similar to those found on William Optics and other scopes of this size but not screwed in like top end Tele Vue types. The dew shield (Sun Shade??) retracts along the tube for transport like most seem to these days. The tube is a pearlescent white which I must admit I am not a fan of. I’d much prefer either a plain gloss finish or the powder coated finish found on my William Optics FLT for example. There is a large Lunt Solar sticker on the tube which also looks a bit cheap but these are mere cosmetic details and not at the end of the day what the scope is all about.

That comes next along the tube in the form of the red anodised etalon chamber and pressure tuner. This contains the heart of the system in the ERF and Etalon. The rather large hand grip for the pressure tuner is prominent sticking out of the side as it does. It is a good size and seems easy enough to use. The ERF and etalon are sub-aperture and unobstructed giving high levels of contrast. There is also an optional double stack pressure tuned etalon which can be fitted at any time behind the original one to narrow the bandpass even further. The supplied flight case has cut outs pre cut to allow this to be fitted and the finished scope to sit in the same case, a nice touch.

Behind the etalon chamber is a very nice feathertouch 2” focuser. This is a bit of a luxury as I’m sure the Lunt Crayford would be fine but hey ho...

I then have a B1800 blocking filter. The stock blocking filter is 1200 but the 1800 is better for imaging so hopefully this will bear out in future. The blocking filter is contained in a star diagonal (sun diagonal? Just our nearest star...) which has a long 2” extension tube on the scope end and a 1.25” eyepiece holder topped with a t-thread on the other end. This can be removed and the base of the diagonal is also t-threaded so I have fitted a t-threaded 2” EP holder so that I can use my other EP’s in the scope.

I hope to acquire a Celestron SE mount for this scope but at the moment I have fitted it to my Tele Vue Gibraltar mount. This isn’t ideal as the balance point is very far to the rear and the pressure tuner makes moving the scope forward impossible on the TV mount. However a set of ankle weights wrapped around the front end of the tube has restored some balance.

So far the sun has only put in about 30 minutes of appearance so my initial use has been limited to this brief period late in the day after work. Finding the sun using the sol searcher is a snap, using a low power setting on the Lunt Zoom there was a nice red blob. Getting the blob to form a circle was straight forward enough using the blocking filter extension tube and then the fine focus on the feathertouch. At this point is was a bit of a letdown, ok, there was a red circle in focus, with my Baader solar film on my current refractors I can see a focussed white circle so what’s the benefit?

Well, then comes the tuner, I twisted the tuner down to a few turns from the bottom and suddenly a number of very visible, bright prominences snap into view. This is what it’s all about. Using the tuner to subtly alter the bandpass and see some of the detail. I must admit, the proms were bright and easy to see, so far I have had much less luck with the surface detail, other than sunspots as you would see anyway. But I am sure practice will help with this and a bit more sun would help...

For imaging a webcam or fast frame rate camera can be attached via the 1.25” eyepiece holder or a camera fitted with a t-thread can connect directly to the blocking filter.

I will give more detail on the visual and imaging performance through the summer but for now it’ll be cloud cloud cloud as the astro kit curse is sure to strike.

Regards

[Viv]

Nice first report Stuart.

Looking forward to your next ones.

[steppenwolf]

Excellent, I'm looking forward to parts 2 and 3. Now put that Feathertouch focuser away and stop fondling it!

[Merlin66]

"The ERF and etalon are sub-aperture and unobstructed giving high levels of contrast."

I assume from your comments that the objective is just a plain single 60mm lens?

I had a visitor last week with his 60mm Lunt double stack - it had a full aperture ERF/etalon filter up front and the sub-diameter etalon at the back. I think this is the "standard" rather than having two sub-diameter etalons to tune???????

[Rossco72]

Forgive me if i get the nomenclature wrong as i'm new to solar.

The scope has a normal ED doublet refractor lens at the front. Looking down the tube there is a reflective lens which i assume to be the ERF. The etalon is in the pressure tuning chamber in front of the focuser and the Lunt DSII module if purchased goes behind the pressure tuner and is also pressure tuned. reading the Lunt blurb it says these are unobstructed for best contrast. As they are at the rear of the scope and smaller than the front lens diameter, I assume they are sub-aperture.

Cheers