Lunt 1.25" Herschel Wedge

[LukeSkywatcher]

The reason i bought a variable polarizing filter is because when my wedge arrived, i could see it was polarised to a degree but wasnt sure to what degree. I thought it best to add more polarisation. I bought the Baader SC also. I thought that was a safety filter, but it isnt. I wasnt sure i'd ever use it but use it every time.

[LukeSkywatcher]

26 minutes ago, John said:

The wedge I've purchased includes a single polarising filter so I should be "good to go"

I seem to have a dark green filter knocking around my bits box so that will be worth a try too I reckon. Would the dark green filter be used stacked on the bottom of the eyepiece with the single polariser or would you use one or the other ?

You can use both stacked or just either or............

[Moonshane]

It is definitely ok with the 120mm John. Used mine with both a 120 f5 & a 120 f 7.5 with no issues.  Marcus Ludes who designed this wedge confirmed once that he uses a 1.25" wedge in his 10" apo.
The rear disc does get pretty hot on good days and certainly would with a tracking mount but it cools quickly. Keeps your hands warm in winter! Hardly gets warm with 80mm.

Honestly you'll love it.

 

[paulastro]

34 minutes ago, Stu said:

No, you should be fine using the 1.25" in your 120ED, I think Shane does it and I used to.

Are you sure about this Stu?  I have a Lunt 1.25 HW and I thought they said it should only be used up to four inches aperture?  I haven't got a scope bigger than four inches myself, but it would be nice to be used in other people's. 

[LukeSkywatcher]

I just love this image. Its my solar setup. It is so light and compact but delivers the views. I am outside observing the Sun within 3 mins.

70mm Celestron Travel scope

1.25" Hershel Wedge 

8-24mm Hyperion zoom

Horizon 8115 tripod

*not visible are the ND3.0 filter,the Variable polarising filter and the Baader SC filter*

 

[John]

Thats a sweet scope Paul - nice that you keep it well fed, watered and bedded too !

 

[michael.h.f.wilkinson]

Congrats on that purchase. I use my Lunt 1.25" Herschel wedge in the APM 80 F/6 and it works a treat. I generally use the Baader Solar Continuum filter, and sometimes the polariser, but not both together.

[LukeSkywatcher]

17 minutes ago, John said:

Thats a sweet scope Paul - nice that you keep it well fed, watered and bedded too !

 

The scope cost me 95 euros new and i never used it much (if ever) until i decided to get into solar observing. Moonshane (in particular) was instrumental in me taking up solar observing. I asked all the idiotic questions and he never once didnt answer my concerns. I even named my solar scope after him. My 8" SCT (Mick) is named after Michael.h.f.wilkinson because he was instrumental in my buying the 8se because on my budget it allowed for the biggest aperture while being the most  portable setup for me.

[mikeDnight]

On 25/04/2016 at 18:00, paulastro said:

Are you sure about this Stu?  I have a Lunt 1.25 HW and I thought they said it should only be used up to four inches aperture?  I haven't got a scope bigger than four inches myself, but it would be nice to be used in other people's. 

I thought the 1.25 was good for scopes below 6". At least that's what I've read from either the instruction sheet or from BC&F's web site.

Mike

[Moonshane]

I base my opinion on the scope I use, a 120mm ED Skywatcher. It's fine. Worst case scenario is that the wedge is damaged but doubt this could create problems for the user or the scope, just that a new wedge would be needed.

[xtreemchaos]

yer works well with my ed80,120mm f5,and my AR127l f9.5, and it dont get too hot just warm, with the AR127 it gets about as hot as a cup of coffee with milk in it after a hour.charl. ps here a pic of my solar setup.

[spaceboy]

I can confirm with others that a 120mm refractor is fine with a 1.25" Lunt HW. I had my doubts after reading Lunts recommendation of 1.25" up to 4" and 2" over. I'd even made my purchase of scope based on this being the ST102 which was then later replaced by the ST120.

I have since then attempted imagine on several occasions with the ST constantly tracking the sun while noting only on one occasion where I felt it needed a breather and the dust cap was put on while I continued to observe in Ha. The Lunt wedge soon cooled and was back up and running way before the minutes end. The only thing I have noted is if you do use a filter stack of either SC / oiii & polorize filter always make sure the polarize filter is the closer to the eyepiece. May sound obvious to some but for other's a lack of clear instruction may result in the thought the same levekl of performance can be achieved in either stack configuration. 

For the record I have also tried the 1.25" wedge in my evo150 and while it does work you are very limited to the amount of time you can observe before the wedge becomes noticeably hot. Not that this makes any real difference as for some reason the added aperture in my opinion did not bring a significant advantage to the views on the days I tried it. I'm sure there will be days where seeing permits advantages but I'm also guessing those days would also go to heating the wedge even quicker anyway.

 

[Piero]

I think Lunt's recommendation are generic in terms of the location the Lunt is used. 

In the UK, the back of my Lunt gets warmer mostly in the summer, but it is never really hot. In Italy, the back gets very hot instead. It can burn your finger if touched.

So, personally, considering the opinion of members in here, it might be okay with a 120mm here in the UK where summers are quite cool, wind is common and the country latitude is quite high. 

Instead, I would definitely follow Lunt's suggestion for all the other countries at lower latitudes and where summers can reach +30 degrees. 

As solar can be dangerous, equipment expensive, and this forum has an international audience I would be careful with the suggestion that is fine, particularly if this is against what the vendor says about their product.

Piero

[Stu]

It's interesting Piero, the information in various places on the web is fairly inconsistent which doesn't help. Most of the dealers seem to say 'works best in scopes up to 4", not to be used in scopes over 6"' but it is not totally clear.

Lunt say 'Available in either a 2″ or 1.25″ model.  1.25″ is best for refractors 4″ and under, and the 2″ is best for refractors 6″ and under.'

None of these indicate a safety issue with using the 1.25" Wedge in a 6" scope. The back heat sink on my Wedges has never really got more than warm, despite the warnings. I would expect it to get extremely hot with a big scope under Mediterranean skies but I think it is designed to take that?

Being cautious and careful is the best bet in these cases but it seems from the guidance that it's ok. Everyone must make their own decision based on available info though.

[Piero]

I agree that the information reported on the Lunt website is not very clear. Precisely, it is not clear what they mean by being best for. 

Analysing the meaning of this, I can only think about two explanations: 

1. Aesthetically. To view a larger area of the Sun one needs 2" eyepieces, hence a 2" model. I suppose this might also remove vignetting if these are present with a 1.25". 
2. Safety. A larger refractor collects more light and therefore a larger back side is needed for releasing the warm/hot air in the tube.

Interestingly, also FLO reports an important notice "Only for use with refractor telescopes up to 150mm aperture." on their website, highlighting that the heat accumulated inside can be an issue. Sure, no data is available to quantify the safety boundaries and hopefully Lunt collected enough data about this. Nobody instead seem to mention about aesthetic reasons instead. 

 

 

While I agree with you regarding the unclear text reported by Lunt, I partially disagree with this:

1 hour ago, Stu said:

Everyone must make their own decision based on available info though.

The reason why I disagree is that we are making information too with this thread. The information that (1) lunt 1.25" seems fine with a 120mm (everywhere??) or that (2) 'Worst case scenario is that the wedge is damaged but doubt this could create problems for the user or the scope' does not have any supporting data. If a Lunt heats up too much and breaks, we cannot really predict the outcome. Since solar observation can be very dangerous if a proper filter is not used, I think we need to be very careful before disseminating information like the one above. 

Many countries are more lucky than the UK with the weather, not just the Mediterranean countries. As this is a public forum, I think it is important to think in the interest and safety of everybody. In the same way we repeatedly report how solar filters are crucial for observing the Sun safely, I don't think it is correct to report information that we cannot support with data, especially when safety is a major concern. 

[Stu]

Piero, I agree with your concern, but ultimately this is not a safety issue. If the wedge is damaged then you do not risk your eyesight, the view will just degrade.

Lunt's position states that it is not for use above 6", they are a US company used to bright sunshine at high elevations so will not base their calculations on the UK. If this were a safety issue then they would state categorically on their site that it is not to be used, rather they say 'best used'

I have asked FLO to clarify this for us anyway so hopefully we can have some better information soon.

[Piero]

Thanks for asking FLO to clarify this. I hope you are right and that they can confirm this. 

[John]

So far I've only used mine with my ED102 Vixen. With patchy cloud, the heat sink of the wedge didn't get warm at all. With longer periods of sunshine it got mildly warm to the touch but no more. I may give it a try with my ED120 sometime.

[101nut]

A continuum and a single polariser should be good. The filter order (from objective) should be wedge, ND3, then chosen 'enhancement' filters.

I have the ND3 and continuum permanently mounted in the nose of my 2" wedge, the the polariser can be mounted on the end of the eyepiece. Since there's a plane mirror reflection within the wedge the beam is already polarised so polarisation angle variation is made simply by rotating the eyepiece. The only thing to watch is having enough room for the filter stack without crashing the wedge face or intruding into the light path, neither of which is good ... 

AndyG

[Moonshane]

I have seen a report from Markus Ludes who designed the Lunt wedge that he uses a 1.25" wedge with his 10" apo with no issues. One thing that would be interesting to establish is whether the prism gets hot or just the dot at the back of the wedge. If the prism does not get hot then whilst I have no evidence to back up my assertion, I doubt there are any possible safety concerns. 

Maybe FLO can obtain confirmation from the horse's mouth.

[FLO]

9 hours ago, Stu said:

I have asked FLO to clarify this for us anyway so hopefully we can have some better information soon.

I will email them for advice  

HTH, 

Steve 

[Paul73]

One thing that I do know is that the view is great through an ED120. The owner of the scope reported no overheating problems. He did stress that he wouldn't use it on a tracking mount due to heat buildup. But, for manual tracking, or lack of, the sun wasn't in shot long enough to cause issues.

I guess that the golden rule is, if you don't feel comfortable, don't do it. Pero's point is well made about the quality of info on which we make decisions. My tuppence worth is second hand information and although I trust the primary source, it is unlikely to have tested his findings to any degree.

Paul

[FLO]

On 15 May 2016 at 22:45, FLO said:

I will email them for advice  

Lunt feel their existing advice is correct and up-to-date. 

At our website's Lunt Herschel Wedge product description page we have a number of notes advising correct use: 

Quote

 

Available in two sizes:  

2” (LS2HW) accepts 2” eyepieces (or 1.25" via your telescope's existing 2"-1.25" adapter) and has a 2” nosepiece for the focuser - performs best on refractors with 6” or less front aperture. 

1.25” (LS1.25HW) accepts 1.25” eyepieces and has a 1.25” nosepiece - performs best on refractors with 4” or less front aperture. 

IMPORTANT: 

1. Only for use with refractor telescopes up to 150mm aperture. The full energy and heat of the sun will be inside the telescope so Lunt advise using only refractor telescopes with a Herschel Wedge. 

2. Not suitable for use with Petzval or other telescope designs with a rear lens element positioned close to the focuser drawtube. 

3. Never mount a 2"“ filter in front of a Herschel Wedge! Any filter mounted into the full beam of Solar energy so near to the focus point will become extremely hot and damaged within seconds. Filters must only be mounted above the exiting side of the prism. 

4. Solar observing is dangerous and can be hazardous to eyesight. Safety is everyone’s responsibility, please use the correct equipment and read the safety notes supplied with the products carefully.

 

If anyone would like us to edit or add to the above please say  

HTH, 

Steve

[DRT]

I read this thread this morning and it prompted me to experiment with my Baader CoolCeramic Wedge as I sometimes find it very bright and lacking detail. I have the photographic version, which includes the pre-installed ND 3.0 and Solar Continuum filters plus 0.6, 0.9 and 1.8 ND filters that can be used in combination to dim the image. I thought these were only for AP so they have never been out of their boxes before today. 

After switching them in and out I have found that the addition of the ND 0.9 gave the best results with lots of graining, small spots/pours and faculae easily visible that I could not see with only the 3.0 ND and SC filters installed. Result!

I will now buy a polarizing filter for my Lunt 1.25" wedge as I after find that too bright. I have a SC filter for it (thank you @Paul73 ) but have been somewhat underwhelmed by the detail visible. Hopefully this will fix that problem.

Oh, and I've used it in my ED120 with no adverse effects and no detectable heating.

Thanks for the info in the thread, which is very helpful.

 

PS: FLO have sold out of Baader single polarising filters. I wonder if this thread is to blame

 

 

[LukeSkywatcher]

"I will now buy a polarizing filter for my Lunt 1.25" wedge as I after find that too bright". 

Can you not just use the 0.6,0.9,1.8 ND filters from your ceramic wedge?. It sounds like they do the same thing as a Polarising filter.

*wipe that* 

I see your ceramic wedge is the imaging one, so i'm guessing the ND filters you have for it wont fit the 1.25".