Herschel wedge 1.25 in - safe refractor size limitations

[Telescope40]

Hello All.    Have read numerous posts re this subject and  please take my humble apologies for returning to the issue.  Have never got a conclusive answer in my head from all I have read.

I Currently used Baader film with my 2 Fracs.   Having read the increase in performance of a wedge in comparison,  I am thinking the following will apply.   It centers around whether it's safe to use a 1.25 wedge on my 127 Meade Frac.   Happy that there will be no issues with my Borg 100 achro.

So long as I am careful not to use the wedge for a long period of time - 10 mins max  ??? - with the 127,  would you go ahead and purchase a wedge to use with both these scopes.

Safety first and all that.  My Wallet really wishes to avoid buying the 2 in version of the wedge as funds could be used in other areas, as always . LOL

 

Any advice / wisdom would be great.

Regards   John

 

[Mark at Beaufort]

John I appreciate your dilemma about using a 1.25" Herschel Wedge on a 5" scope. I have used my Lunt HW for a couple of years in my 4" Astro Tech APO without any problems of overheating. The view IMHO is far superior that anything else I have used in over 40 years viewing the Sun

I suppose you will get many members saying they have used a 1.25" HW in scopes of 5" and 6" without a problem. I may be wrong but I would have thought that the material used in a 1.25" and 2" are the same, only the size is different.

In the end its only Baader or Lunt that will be able to give a precise answer to your question. However, this is on the Telescope House website  and they are a very knowledgeable company and would not be quoting this unless they were pretty certain. Or if you are really worried send an email to Lunt in the United States.

[John]

I have the Lunt 1.25" solar wedge. I've now used it with 100mm, 102mm and 120mm refractors and it's worked fine. The heat sink gets a little warmer with the larger aperture but I didn't feel that the wedge was at any risk during the 30 mins or so I used it with the larger aperture scope.

 

[Stu]

I think Mark's post says it all. Safe up to 150mm. The heat sink is just that, and it has a warning that it may get hot. So if it gets hot, well just don't touch it ;).No safety issue either, the worst worst case is a damaged prism, not a blinded eye.

I've used a 1.25" Lunt wedge in a 120mm scope for relatively long sessions with no problems.

[xtreemchaos]

i use my 1,25 lunt solar wedge with my ed80, st120 and AR127L with no problems, with the 127 it gets as hot as a hot cup of coffee after about 30 min in full sunlight and stays that hot for aslong as ive used it in a session about 2 hours till sols outa range or cloud.charl.

[sungazer]

I have used my Lunt 1-1/25" HW on a 100mm refractor for quite long sessions without any problem it just gets hot but not excessive .

Just my experience ,regards,John.

[spaceboy]

I have as others have, used the Lunt HW 1.25" in a 120mm refractor and can concur that it works OK at least in the UK where sun isn't a dominant feature. I have also used the HW / ST120 combo for imaging on a driven mount and as long as you check the heat sink from time to time to make sure it doesn't get too hot again your going to be OK. I will though note that the wedge is bronzing no doubt due to the heat. It can't be because of direct sunlight bleaching it as I always use a scope and skies sun shade (very handy acc').

As always it is down to the individual to make up their own mind and any advice is offered through my personal experience and by no means an endorsement to use a product beyond the manufacturers specification.

[Telescope40]

Hello everyone who replied. Fantastic, informative responses as always on this website. 

I was correct with my initial thoughts.  Birthday in a few weeks.  Wedge now added to Ye Olde Wishlist. 

Regards and clear skies.  John 

[spaceboy]

You may want to add https://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html  or at the very least   http://www.telescopehouse.com/revelation-astro/revelation-filters/revelation-premium-polarising-filter-1-25.html to that birthday list

[Telescope40]

52 minutes ago, spaceboy said:

You may want to add https://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html  or at the very least   http://www.telescopehouse.com/revelation-astro/revelation-filters/revelation-premium-polarising-filter-1-25.html to that birthday list

Thanks Spaceboy.  I was aware a polarising filter will be needed.  Does the Solar continuum filter do the same job or does it give a different / better view

John

51 minutes ago, spaceboy said:

 

 

[spaceboy]

The SC filter adds far more contrast and detail to the view than the polarizer alone. It does though turn everything green but this soon settles as your eye adapts. It is a must in my opinion to get the very best out of the wedge. Some can live without the polarizer but again I feel it adds something and for the sake of £15 its hardly worth cutting costs.

I would buy the polarizer with the wedge (essential to reduce the brightness of the views if not using a sc filter) then put up a wanted advert for the SC though as they are pricey new. 

[Telescope40]

6 minutes ago, spaceboy said:

The SC filter adds far more contrast and detail to the view than the polarizer alone. It does though turn everything green but this soon settles as your eye adapts. It is a must in my opinion to get the very best out of the wedge. Some can live without the polarizer but again I feel it adds something and for the sake of £15 its hardly worth cutting costs.

I would buy the polarizer with the wedge (essential to reduce the brightness of the views if not using a sc filter) then put up a wanted advert for the SC though as they are pricey new.

Many thanks again.    John

[Moonshane]

hi John

I have also used the 1.25" Lunt wedge in my 120ED frac and it does get hot after a while, probably about radiator hot.

Recently I tried a UV/IR cut filter before the wedge (in the 2-1.25" adapter) and it reduces heat substantially albeit not entirely. With that it's about the same heat as an 80mm frac.

I'd certainly recommend it but it's not essential.

 

[Telescope40]

4 hours ago, Moonshane said:

hi John

I have also used the 1.25" Lunt wedge in my 120ED frac and it does get hot after a while, probably about radiator hot.

Recently I tried a UV/IR cut filter before the wedge (in the 2-1.25" adapter) and it reduces heat substantially albeit not entirely. With that it's about the same heat as an 80mm frac.

I'd certainly recommend it but it's not essential.

 

Shane. Think I have a IR filter on a webcam somewhere.  Appreciate the suggestion 

 

John 

[spaceboy]

I know there are IR and UV/IR filter so be careful as I'm pretty sure its the UV light over IR the filter needs to block. I'm not sure how a basic IR filter might react but I doubt it would be a good outcome??

[Telescope40]

Noted. Thank you. 

 

John 

[Alan64]

A traditional, planetary, crown-and-flint achromat is, in my view, the ideal with which to integrate a wedge, and the Borg would be the closest to that ideal.  You'll soon find a polariser indispensable with the Meade.   A 2" wedge is for those who like to "sunbathe", although for those times the Borg and a 32mm Plossl may serve.

[Stu]

6 hours ago, Alan64 said:

A traditional, planetary, crown-and-flint achromat is, in my view, the ideal with which to integrate a wedge, and the Borg would be the closest to that ideal.  You'll soon find a polariser indispensable with the Meade.   A 2" wedge is for those who like to "sunbathe", although for those times the Borg and a 32mm Plossl may serve.

I don't disagree necessarily, but in my experience what is important is not whether the scope is an apo or not, but whether it has a good figure with well controlled SA. A continuum filter takes care of any CA, but you will lose the lovely fine detail at higher mags if the optics aren't good. I think the 102 f11 clones are probably pretty good when used with a wedge.

Second point is that not all 2" Wedges are created equal. The Baader Zeiss definitely has an edge when it comes to high power viewing of granulation cells and fine detail in penumbral zones etc. Having said that, the Lunt 1.25" wedge must be one of the best value products out there; fantastic performance and a great price! Everyone should have one  

[Moonshane]

I am not 100% sure but it seems to make sense to me that it's the IR element that's more key to reducing heat. UV is taken care of by the wedge / filters. Either way as above there's no actual danger to the user, or an appropriate scope, just the wedge (and that's debatable).

[spaceboy]

We put on UV sunscreen not IR sunscreen. The wedge does indeed deal with UV light but by using a UV filter in the path are you not trying to reduce this further so that the smaller heat sink on the 1.25" wedge doesn't get excessively hot by using a larger aperture which collects more sun light?!?!

[Alan64]

Herschel wedges are certainly and currently at their safest point in history, however caution must still be exercised in their use.  I understand that they are to be used with refractors only, but all refractors? 

I've read enough over time where I would only feel comfortable using a wedge with an air-spaced crown-and-flint doublet of no more than 100mm in aperture; and one of fine quality, of course; but that's just me.

[Moonshane]

IR is heat : http://solar.physics.montana.edu/ypop/Spotlight/Today/infrared.html

UV does not create heat but is damaging to tissue : http://www.livescience.com/50326-what-is-ultraviolet-light.html

[Stu]

40 minutes ago, Alan64 said:

Herschel wedges are certainly and currently at their safest point in history, however caution must still be exercised in their use.  I understand that they are to be used with refractors only, but all refractors? 

I've read enough over time where I would only feel comfortable using a wedge with an air-spaced crown-and-flint doublet of no more than 100mm in aperture; and one of fine quality, of course; but that's just me.

Alan, you are correct in that wedges are not supposed to be used in Petzval design scopes, anything that is likely to have a cemented element near to point of focus. Non air-spaced triplets (eg oil spaced etc) are also to be avoided apparently. Although I've heard of people using them with no problems I would certainly say it's best not to try.

There are no problems as far as I'm concerned with air spaced ED doublets or triplets and the 100mm limitation you set yourself is over cautious. I have regularly used a 106mm fpl-53 triplet, a 120ED and currently use my FC-100 Fluorite doublet with no problems at all. The views through the Tak are the best I've had so I am glad that I've found this combination.

[spaceboy]

35 minutes ago, Moonshane said:

IR is heat : http://solar.physics.montana.edu/ypop/Spotlight/Today/infrared.html

UV does not create heat but is damaging to tissue : http://www.livescience.com/50326-what-is-ultraviolet-light.html

You are right mate. My thinking was all wrong?? I see what you are saying now. My thoughts were the whole idea of using the wedge to stop any damage to tissue ie: our eyes. If the UV light is the one we need to avoid adding further protection from that in the form of an additional UV filter was going to be more effective than an IR filter alone. Of course your reasoning for trying filters in the first place was to reduce heat as apposed to offering any further protection from damaging UV. Obviously your recommendation were for using a UV/IR filter where you gain both. My concerns at this time were that if the OP only had an IR filter like the ones used for webcam imaging would not be ideal but your findings suggest otherwise.

Although the IR link also suggests More than half the Sun's power output is in the form of infrared light, though much of it is absorbed by the Earth's atmosphere.

 

[Moonshane]

As with any solar equipment (in terms of herschel wedge and HA based equipment), the IR/UV or ERF filter is there to protect the gear not the user as the wedge/ha filters protect the user.