Refractor for Baader Herschel Wedge

[Stu]

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.

I've always read that oil spaced objectives are a complete no no when it comes to solar without a full D-ERF up front. I certainly wouldn't want to risk a TEC140 if I had one!

[hunterknox]

Here's a solarchat thread on he same topic: http://solarchat.natca.net/viewtopic.php?t=4307&p=43819

In summary, check design specifics with the manufacturer but there doesn't seem to be anything intrinsically bad about using oil-spaced refractors.

[Stu]

Interesting. Fortunately, or unfortunately I don't have a TEC140 so it's not a problem, but it appears you are right and it is ok providing it has the correct metal rather than plastic ring.

As a general rule though I would think checking with the manufacturer is strongly recommended

[russ.will]

I could be way out here, but I thought the issue was only when used with a dichroic UV/IR cut mounted on the wedge, which reflected energy back at the objective? I'm sure somebody on here melted an objective (or whatever it was between the objective) on here in the last year.

Russell

[Stu]

I could be way out here, but I thought the issue was only when used with a dichroic UV/IR cut mounted on the wedge, which reflected energy back at the objective? I'm sure somebody on here melted an objective (or whatever it was between the objective) on here in the last year.

Russell

It's certainly an issue with a D-ERF. I have one internally mounted in a 150mm f5 scope and the reflected light beam comes to focus quite near the objective. I actually melted a hole in a foam aperture mask because the tilt I had in the D-ERF was too much.

[Moonshane]

This must be an issue also with where the derf is sited. The closer to focus point the more likely I think it is to focus the light to a point at the primary end? I put mine as close to the objective as I could but without vignetting

[Bender]

When using 2" eps with the 2" baader wedge I found I don't have enough infocus with my 100ed, but are ok with the 80ed.

I even struggle with my 1.25" baader 12.5mm micro guide EP in the 100ed. And I connected a 1.25 T2 ep holder directly to the wedge, for shortest possible light path.

The Tak le and Fujiyama orthos are ok though.

[Stu]

This must be an issue also with where the derf is sited. The closer to focus point the more likely I think it is to focus the light to a point at the primary end? I put mine as close to the objective as I could but without vignetting

So did I Shane, but unless I got my Maths completely wrong, that point was pretty far back in the tube in my scope so the focus point is near the objective. I have a 150mm scope with a 75mm D-ERF

[russ.will]

I can't help thinking it must be more of an issue with short foal ratio scopes, where the focal point of the rejected energy forward of the filter will be commensurately closer to the objective.

Russell

[Stu]

I can't help thinking it must be more of an issue with short foal ratio scopes, where the focal point of the rejected energy forward of the filter will be commensurately closer to the objective.

Russell

I'm sure that is correct Russell

[DRT]

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.

The wedge arrived yesterday. The only EP that I can get to reach focus in the ST102 is my Ethos 8mm - which is good enough for me until the 100ED arrives

Some lovely detail around a string of sunspots this morning.

[DRT]

When using 2" eps with the 2" baader wedge I found I don't have enough infocus with my 100ed, but are ok with the 80ed.

I even struggle with my 1.25" baader 12.5mm micro guide EP in the 100ed. And I connected a 1.25 T2 ep holder directly to the wedge, for shortest possible light path.

The Tak le and Fujiyama orthos are ok though.

The 100ED arrived this morning and I've been able to reach focus with all of my EPs with the wedge installed

[101nut]

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.

Any supplementary filters must go after the OD5 ND (except the SC filter which precedes it.)

I'm a bit confused.

The ND is a safety component designed to reduce the image intensity with no other filtration apart from the wedge, thus it must be fairly heat resistant. So why should the SC be placed between the ND and the wedge, rather than being treated like any other filter and 'protected' by the ND by placement between the ND and the eyepiece?

AndyG

[DRT]

The ND3 is further dimming the image after the wedge has taken most of the light away. The blurb in the user guide says that placing the SC filter between the wedge and the ND3 "reduces unwanted reflections".

I tried it out today without the SC (just ND3 + ND0.6) and the image was bright with a slightly uncomfortable bright spot in the centre. I also tried it with the ND0.9 and ND1.8 in tandem with the (compulsory) ND3 and they were both more comfortable. But the telling point is that you can see granular detail with the SC filter in place that is not visible (at least to me) with just the ND filters.

I'm glad I bought the "imaging" version as it includes the three additional 2" ND filters but is otherwise identical to the "visual" version. The price difference is about half of the price of buying those filters individually so now I have lots of very good Moon filters if I want to have a session with multiple scopes

...or some of those filters might find their way to the Classifieds or ABS

PS: The compulsory ND filter is a 3, not a 5 as stated by Rainmaker above.

[Stu]

That's interesting Derek, I've always put my continuum filter the eyepiece side of the ND3.0, for reasons of protection as stated. Did it say in your instructions to do it the other way?

I guess that all of the heat has been taken out by that stage, the ND3.0 is just dimming the light further to safe levels.

[DRT]

That's interesting Derek, I've always put my continuum filter the eyepiece side of the ND3.0, for reasons of protection as stated. Did it say in your instructions to do it the other way?

I guess that all of the heat has been taken out by that stage, the ND3.0 is just dimming the light further to safe levels.

Yes, it says that in the instructions and that is the order in which they were pre-installed. The warnings relating to filter damage all relate to placing the filters before the wedge.

For some entirely unacceptable reason (probably to do with production cost) the nose of the wedge has a thread that accepts filters and the user guide is full of warnings not to place filters in that thread. Supplying a nose with no thread doesn't seem like rocket science to me and would solve the problem completely.

[DRT]

Here is the relevant instruction in the user manual...

[Stu]

Thanks Derek, I have them the other way round, will give this a go!

You learn something every day in this game!

[DRT]

Thanks Derek, I have them the other way round, will give this a go!

You learn something every day in this game!

Do you have a Baader or Lunt wedge? Might be worth checking an instruction manual if it's the Lunt just to be safe ;-)

[Stu]

True enough. Mine is a Lunt.... Would seem that similar principles apply but will not do anything without checking.

[DRT]

I've just been out having a look at Jupiter and Venus through the 100ED in the fading light. I now understand what all the fuss is about using slow APOs for planetary observing

Looking forward to some nice wide field views later tonight!

[Stu]

I've just been out having a look at Jupiter and Venus through the 100ED in the fading light. I now understand what all the fuss is about using slow APOs for planetary observing

Looking forward to some nice wide field views later tonight!

M45 is about 3 degrees from Venus tonight, and closer tomorrow. Just had a look, really nice in the same fov

[DRT]

M45 is about 3 degrees from Venus tonight, and closer tomorrow. Just had a look, really nice in the same fov

It's all down behind the roof line from here now so can't get that view

[Stu]

It's all down behind the roof line from here now so can't get that view

Shame

[YKSE]

For some entirely unacceptable reason (probably to do with production cost) the nose of the wedge has a thread that accepts filters and the user guide is full of warnings not to place filters in that thread. Supplying a nose with no thread doesn't seem like rocket science to me and would solve the problem completely.

I think you're right.  My guess is that Baader has one and only kind 2" nosepiece for all their diagonals, that's a way keep good product quality and maintain low inventory for lower product cost. If they're to do a specific 2" nosepiece for wedge only, they will either have a specific treatment for non-threaded nosepiece (seperating from the threaded ones, painting process), or a new production line, that'll cost something, also keeping inventory of a low volume product is an addition cost.