Refractor for Baader Herschel Wedge

[DRT]

I have ordered a Baader Herschel Wedge from FLO which should arrive in a couple of weeks. I am planning to use it with my Skywatcher Startravel 102T but want to make sure that I will be doing the relatively expensive wedge justice by putting it in such a modest scope.

If such a thing exists, what is the ideal type and size of refractor to use with a Herschel Wedge? I am considering buying an APO of some sort for night time observing but don't know whether that would give any benefits over the Achro for white light.

On the safety side, are there any types of refractor that need to be avoided for use with a wedge?

Thanks in advance.

[michael.h.f.wilkinson]

I use my 80mm triplet, which is brilliant. An achromat can work, but will show chromatic aberration. However, this will be minimal if you include a Solar Continuum filter.

[DRT]

Thanks, Michael.

The Baader has a pre-installed Continuum filter so that should help the ST102.

What I am really wanting to know is will I see more detail in white light with an expensive refractor than with my humble ST102 that cost me £100?

Also, Is there any advantage in having a larger aperture for Solar viewing or should I stick to the 80-100mm range?

[Moonshane]

I used to love the views through my 120 startravel. The views through my 120ed are no better on the sun in truth but the edge of field egginess is not there with the ed.

The 120 ed is better for everything else though other than mega wide fields

[nightfisher]

Only time i have looked through a scope fitted with the wedge was a vixen 102 f10 achro, and a star travel 120, hard to say which gave the best view

[RichieP]

On the safety side of things, you just need to avoid any refractors which have extra lenses near the eyepiece end e.g. petzvals and scopes with in built field flatteners.

[DRT]

On the safety side of things, you just need to avoid any refractors which have extra lenses near the eyepiece end e.g. petzvals and scopes with in built field flatteners.

Thanks - that is exactly the sort of advice I need.

I am considering a second-hand TeleVue refractor and would hate to spend £1k and then have it melt the first time I pointed it at the Sun :-(

[russ.will]

I used to use my wedge on a Bresser AR127L and even after extended viewing, the wedge never got hot enough to hurt yourself. There was only a smidge of CA in the 127L compared to the complete absence in the Apo, but when you put the SC filter in the chain, there obviously was no CA and the larger aperture of the 127L murdered the 80 Apo for detail.

Mind you, the detail available full aperture through Baader Solar film full aperture on the LX200 is on another level again.

On a side note, the Bresser scopes are also available from and branded by Opticstar. The short tube versions of the 127L and 152S (labelled Quad) I always thought were Petzval designs, but they make specific reference to the Quads being suitable for solar viewing  "...when used with a specialist H-Alpha Solar filter at the eyepiece end". No mention of ERFs, etc.

Russell

[Merlin66]

The sweet spot for average seeing seems to be around 100-120mm aperture.

I have a great TV Genesis and found that at least one other amateur is using it safely with a Baader wedge.....

BUT I decided not to take the risk and bought a TS102 f11 (similar to the Lyra) for my white light imaging.

(It also fits well with the PST mod ;-) )

[Stu]

Totally agree that 100 to 120mm seems best. I also think that an apo can help with better images. If using a continuum filter then CA won't make any difference but a well figured lens certainly will.

As Ken says, I'm sure the Lyra clone f11's are good, and good value.

My TV85 gives lovely views, not as much detail as a 120ED for instance but still very nice. A TV 102 might be worth a look, no Petzval to worry about in that.

[michael.h.f.wilkinson]

I am looking at various 102-127mm achromats to upgrade my solar viewing. I will be mounting a tri-band ERF internally  (85mm one) which will allow use in solar continuum band, H-alpha and CaK (in the distant future). I am not sure I would fork out for an ED, unless they are the only ones at the ideal focal ratio for my H-alpha filter + Tele-Centric (F/7 to F/8). Should I I go insane (been there, done that ) and get a 6" frac for solar I will certainly go for an achromat (F/8).

[damnut]

I used my Phenix 127m with a solar filter for the recent partial eclipse. This is my first pic ever using un mod dslr through a scope. Echo comments above for the petzval scopes with the Hershel Wedge, Was also advised not to use with  the 152mm Petzval Meade.

[ollypenrice]

Also of vital importance is not to choose an oil-spaced instrument. These are fairly unusual but we have one here in our TEC140. Astro Physics are also keen on oil spacing.

I haven't done much wedge observing but the view through a Tak FS60 was remarkably good. For some reason the granularity showed better than in a big refractor that day, though the big one pulled more susnpot detail and could magnify far more.

Olly

[Rainmaker]

I used mine with the TSA 120 and the FS60Q, there was a difference but it was not anywhere as big as the apertures would suggest.  

As previously stated the Solar Continuum filter will negate any worry about the dreaded CA.

The Baader ClickLock Herschel wedge comes with the SC and the OD 5 ND filter fitted between the prism and the eyepiece clamp.

Should you ever have cause to remove the filters remember to reinstall them so that the sc filter is nearest to the prism.  

You can view safely without the SC as long as the Optical Density 5 neutral density filter is ALWAYS in place.

The view will be brighter and you may want to attenuate it somewhat with either a second ND filter or a Baader polariser.

Do not place any filters into the threads of the nosepiece of the Wedge.  Although these threads will accept the standard 48mm filters, the heat that is generated in front of the prism will destroy the filters and may damage the scope of prism.  Any supplementary filters must go after the OD5 ND (except the SC filter which precedes it.)

You can view with the OD5 ND in place in the wedge and a 'single polariser' in the eyepiece threads , this will allow you to vary the image brightness by rotating the eyepiece  in the clamp.

[Rainmaker]

Couple of other pointers: 

Remove your finderscope you won't need it saves worrying about someone accidentally looking at the Sun.

I used the shadow of the dew shield to line up the OTA and then you will see the image (defocussed) of the Sun in the ceramic tile. Only then put you eye to the scope. 

When not actually viewing even for short times, turn the scope away from the Sun, there is no point heating things up unnecessarily.

A sunshield, even a piece of cardboard placed over the OTA will shade the top of your head from sunburn if you're hirsutely challenged  !!!!

Enjoy, the Baader wedge is the best way to view the Sun in white light.  Much safer than a filter covering the objective.  If the wedge falls off you get defocussed sunlight toward your chest.

If the objective covering filter falls off in use you will get superheated retinas.

[DRT]

Thanks, Rainmaker, lots of good advice there and exactly the sort of steer I was looking for.

I will test the water with my ST102T and perhaps leave potential future expensive APO purchase for wide-field observing

[Moonshane]

You would be welcome to try my 120ed any time mate if over Stockport way anytime.

[DRT]

Thanks, Shane.

Does the Sun ever come out on that side of the Pennines?

[Mark at Beaufort]

Derek did you have chance to look through my 102mm Astro Tech APO when we did the eclipse together? Although I did not have the Baader I was using the Lunt Herschel Wedge.

[JamesF]

Also of vital importance is not to choose an oil-spaced instrument. These are fairly unusual but we have one here in our TEC140. Astro Physics are also keen on oil spacing.

I thought Alexandra uses a TEC140, but perhaps she has an ERF up front?

James

[Moonshane]

Thanks, Shane.

Does the Sun ever come out on that side of the Pennines?

Fair enough - no......   

[michael.h.f.wilkinson]

I thought Alexandra uses a TEC140, but perhaps she has an ERF up front?

James

I think she does. A front-mounted ERF should reduce the heat sufficiently

[DRT]

Managed to pick up a 100ED at a good price so looking forward to trying that and the wedge when it all arrives.

[JED-E3]

Congrats on the new scope purchase, the stock Startravel 102 won't reach focus with the 2" Baader Herschel wedge in my experience, the light path is quite a lot longer than a normal 2" prism and the 2" clicklock sits quite high, you can make it work with the right adapter and a low profile 1.25" eyepiece holder but hopefully you won't need to with your new 100ED.

James.

[hunterknox]

I think she does. A front-mounted ERF should reduce the heat sufficiently

I suspect that any glass or oil up front isn't an issue - heat gets concentrated at the back of the scope and if anything the oil im a triplet might help to stabilise any temperature differential betwen lenses.

That said I do believe that the earlier TEC 140s aren't recommended for solar viewing - something to do with the collet rings? Later versions had a different design and to say they've been used to impressive effect would be understating it.