SolarChat!

OK, so I just saw a Lunt LS230THa for sale. I wasn't aware that such a telescope existed. It's an f/7, so it's over 5 feet long. Lunt does not list a 230 on their website, so either they once made them and no longer do, or else the 230 is a special order model.

Does anyone here know anything about the Lunt LS230? Did Lunt have problems that caused them to stop making this model, or did the 230 simply not sell due to the high cost? How much would a telescope like this actually be worth on the resale market? The same seller is selling a Lunt 152 and has it listed at full retail price, so I'm guessing that his asking price of $22,000 for the 230 is close to its list price. I wonder also what a second etalon would cost - or if one even exists.

It's a wonderful thing to fantasize about, but suspect that it would be only the starting point of a list of expensive additions, beginning with a dedicated, permanent mount. What other accessories are need for a scope of that size? What innate problems come with a larger sized instrument like this? Would a dome become a requirement to avoid wind buffeting the scope? What size of an image circle would such a scope produce? In other words, how large of an imaging chip would you need on a camera to see most of the field of view?

Just curious. Simply seeing a scope like that has my imagination running

Bruce

If you have the money that much, we can make a good deal with, say, 12" telescope equipped with very nice filtering system and it will be short, compact and not require a large mount.

This is the image of a very small sun spot group taken with 280mm telescope (total cost less than 1/3 of the Lunt 230mm).

Valery

Certainly an interesting proposition Valery. I may consider that.
Seeing that big refractor got my juices going

Lovely shot Valery!

Thanks Bruce .Very good point Valery we have a 150mm DS Lunt for sale here in Australia but as I already have a 150 mod I think my money may well be better spent modifying my 10” SCT?

A 230mm scope with no front mounted ERF has a lot of energy going into the tube. Not sure I would design it that way...

From lunt years ago

https://luntsolarsystems.com/limited-run/

Lunt is pleased to announce the next run of LS230T/B3400/PT Solar Systems.

This run will be limited to 10 instruments. However, we are excited to be offering these systems as the Double Stack version with dual USB/PC Pressure Tune control.

SPECIFICATIONS:
Objective: IR coated (Energy Rejection) 230mm doublet optimized at 656nm
f/ratio: 7
Etalon 1: Internal un-obstructed 80mm pressure tuned.
Etalon 2: Internal un-obstructed 80mm pressure tuned.
Blocking Filter: B3400 internal mount
Bandwidth: <0.5 Angstroms at 656.28nm
Pressure tune control: Computer control, dual support.
Focuser: Feather Touch
Mounting: Tube rings and mounting plate included
TERMS:
MAP: $29,995.00(USD)

Thanks!

Only ten instruments, eh? Quite a collector's item then - if you have suitcases of money sitting around the house and no idea of what to do with them

Derek Klepp wrote: ↑Tue Apr 10, 2018 10:50 am Thanks Bruce .Very good point Valery we have a 150mm DS Lunt for sale here in Australia but as I already have a 150 mod I think my money may well be better spent modifying my 10” SCT?

Hi Derek,

For these kind of money I can easily modify your 10" or 11" SCT as well as the PST etalon and you will be able to take high resolution pictures similar to what I have posted here and there.

Valery

Just need the seeing to go with it

And the mount...

It's a wonderful thing to fantasize about, but suspect that it would be only the starting point of a list of expensive additions, beginning with a dedicated, permanent mount. What other accessories are need for a scope of that size? What innate problems come with a larger sized instrument like this? Would a dome become a requirement to avoid wind buffeting the scope? What size of an image circle would such a scope produce? In other words, how large of an imaging chip would you need on a camera to see most of the field of view?

I would say that in general these larger instruments are only useful for imaging small regions of the Sun's surface, as depicted in Valery's superb image, and as Mark states, excellent seeing is an absolutely necessary requirement. Living in Florida, Hawaii, the Canary Islands, the California coast south of SF, etc. would be ideal.

If your interests and seeing are sufficient, then by all means go this route. However, such instruments would be compromised for typical solar observing under average daytime seeing, and do not perform very well in regard to contrast uniformity over a large field of view. For example, the typical field angle magnification for such a large instrument as the Lunt 230 using a collimator lens system would be almost 2.9 X, yielding a rather significant jacquinot (sweet) spot size reduction. Double stacking results in even a smaller area of on-band performance:

https://www.cloudynights.com/topic/5371 ... try7229898

So I believe these larger systems must be used in conjunction with a smaller instrument for full disc and typical daytime conditions... the "two scope" solution. Lunt has said as much even when considering the LS 152, and how it is designed specifically more for Hi-res close-up viewing/imaging, not low to moderate image scale observing, where a smaller instrument is more appropriate and will perform better.

It is interesting to note that Lunt is using two 80 mm etalons in the LS 230 double stack. This could indicate that both etalons are located within the same collimating-refocusing lens system. However, since each etalon appears to have individual pressure tuning, they would then have to be isolated from each other via another element - perhaps a circular polarizer for retro-reflection suppression? Just speculation on my part. These 80 mm etalons don't seem to be part of the regular etalon production, since no 80 mm etalons appear to be marketed for use in double stacking the LS 80, which is unfortunate, since this is the ideal method to DS an internal etalon such as the LS 80's internal 60 mm etalon.