Using a Baader uv/ir cut filter with 1.25" Lunt Herschel Wedge and larger apertures.

[Moonshane]

Whilst I have always been content with the safety of my wedge for use with my 120mm ed refractor I did wonder whether the reasonable heat levels (about cup of tea hot) on the red disk might affect either longevity of the unit or turbulence reducing detail at the eyepiece.

Stu kindly offered a 2" one for sale at a decent price so I bought it. My plan was to use it attached to a 14mm Baader fine tuning ring screwed onto my 1.25"-2" adapter into which the wedge is placed.

Users of wedges will note that in general filters should not be used between the objective and the wedge due to heat risks.  However,  given this filter sends back almost all the uv and ir (i.e. heat) up the tube and is a recommended filter for quarks in many cases I believed it would be safe (for the filter - based on experience I knew that even if the filter cracked,  I have been using the wedge successfully for a long time). I should stress that all the required filters should still be used.

I am pleased to report that the filter has worked exactly as I hoped.  The heat build up in the wedge has been reduced to very low levels with no apparent negative impact on views; I had considered tube currents a risk. In fact initial results suggest improved detail; I recently saw cell structure for the first time.

I'd recommend this filter for users of scopes of 100mm or more but it is probably still not absolutely essential.

I would be interested to hear from other solar observers able to test this out.

[Stu]

Result ?

Hope that doesn't mean I have to buy one now ??

[spaceboy]

Glad to hear the results of using the filter were positive. I'd ask the same question a while back as my wedge was getting hot quickly in the EVO150 but the general feedback was not to try it. As you say it is recommended for the quarks so why wouldn't it work in a wedge. Sure would come in handy for when I'm solar imaging with the ST120 on a driven mount ?

[Moonshane]

I suspect it may be even more beneficial for imaging.  @Stu I am not placing any weight on my initial findings at this stage but time will tell as always.  you'd be welcome to try it at sgl12.

Cheers

Shane

[John]

I've yet to use my 1.25" Lunt wedge with anything other than my Vixen 102 and my Tak 100 so I've not had the chance to see how it does in the ED120 as yet. Interesting findings though Shane

 

[Stu]

27 minutes ago, Moonshane said:

I suspect it may be even more beneficial for imaging.  @Stu I am not placing any weight on my initial findings at this stage but time will tell as always.  you'd be welcome to try it at sgl12.

Cheers

Shane

I was being slightly tongue in cheek Shane ?, I don't own a frac above 100mm currently and the 2" Baader should be well up to taking the heat even on a 120 or 150 I should think. There's a thought, should I pick up a 150 f8.........

Back on track, interesting if it does improve the image quality in the 1.25" though.

[Mark at Beaufort]

Interesting findings Shane. I have used a Lunt 1.25" Herschel Wedge for several years on my 4" Astro Tech APO and never really felt that the rear panel became too hot. I have it in my mind that Zoltan at 365 Astronomy recommends using a Baader UV/IR filter with a HW but I cannot remember how I know this.

[SkyGibbon]

I have always used an Astronomik uv/ir cut on front of my wedge (on all my scopes. 60mm - 110mm). Very minimal heat on the wedge. I definitely wouldn't film without one. You will see the sharpness pickup instantly.

[Mark at Beaufort]

11 hours ago, SkyGibbon said:

You will see the sharpness pickup instantly.

Thanks for that - it would be interesting to try out a UV/IR on the HW especially if I am taking photos.

[Mark at Beaufort]

I knew I had been here before - here is the thread that I started a few years back

 

[Moonshane]

Cheers Mark

As always there's never a single benefit/impact/story

[spaceboy]

BUMP

Any updates Shane ? I am starting to think I need to do something similar for during the mid day sun.

[AstroSylv1]

If the UV and IR are filtered by the filter, before the HW, it means that they don't go through (obviously), they are not "absorbed" by the filter either, so they are "reflected" back to the tube and lens cell... UV's don't carry much heat, but IR's do, a lot actually... So, while protecting the HW, the eyepiece and consequently our eyes, aren't they slowly damaging the tube or the lens cell by entering, bouncing back inside the tube and getting out again ? Bafflings, coatings, etc....? I am getting curious...

[spaceboy]

If it is Daystar are going to end up in an awful lot of bother. Daystar recommend them for use with their Quark over a certain aperture. 

[Stu]

8 hours ago, disciplus55 said:

If the UV and IR are filtered by the filter, before the HW, it means that they don't go through (obviously), they are not "absorbed" by the filter either, so they are "reflected" back to the tube and lens cell... UV's don't carry much heat, but IR's do, a lot actually... So, while protecting the HW, the eyepiece and consequently our eyes, aren't they slowly damaging the tube or the lens cell by entering, bouncing back inside the tube and getting out again ? Bafflings, coatings, etc....? I am getting curious...

It is certainly something to be aware of, particularly if using a D-ERF. I had one internally mounted on an f5 150mm Skywatcher frac, an had the D-ERF tilted slightly too much. The reflected beam was near focus as it burned a hole through a foam aperture mask I was experimenting with! Certainly don't glance down the tube whilst it's pointing at the sun!

[101nut]

41 minutes ago, Stu said:

It is certainly something to be aware of, particularly if using a D-ERF. I had one internally mounted on an f5 150mm Skywatcher frac, an had the D-ERF tilted slightly too much. The reflected beam was near focus as it burned a hole through a foam aperture mask I was experimenting with! Certainly don't glance down the tube whilst it's pointing at the sun!

Tilt isn't something I hadn't considered. The effective length of a 2" Baader wedge will be about 120mm from the end of the nose piece, so the focus position of the reflected uv/ir will be about 140mm up the tube from the base of the diagonal ... if there's a bit of tilt and a baffle anywhere near that position in the tube it could have interesting consequences ... 

[Stu]

25 minutes ago, 101nut said:

Tilt isn't something I hadn't considered. The effective length of a 2" Baader wedge will be about 120mm from the end of the nose piece, so the focus position of the reflected uv/ir will be about 140mm up the tube from the base of the diagonal ... if there's a bit of tilt and a baffle anywhere near that position in the tube it could have interesting consequences ... 

I would reckon you should be alright with an IR filter screwed into the focuser tube or Wedge, unless things are really out of kilter. My setup was with a D-ERF internally mounted and I deliberately gave it some tilt to avoid reflections, I just gave it too much!!

[AstroSylv1]

I wonder how much "heat" can the lenses on aperture side can take, and how much "heat" can be trapped in the tube, when using a UV/IR filter...