Different approach for my EP collection?

[astro744]

May I suggest a Paracorr too to eliminate primary mirror coma before you go selling off all you good eyepieces. You will get pin point stars to the edge and it may just give you the wow you are seeking. You can always use it with any Ethos you buy later and you're going to need it to get sharp stars to the edge.

Note a Paracorr will increase magnification by 1.15x and decrease true field and exit pupil by 1.15x. I would recommend any Paracorr with a tunable top for easy adjustment bewteen eyepieces.

If that does not satisfy may I suggest you test your current optics and if sub-standard then get a premium hand crafted mirror. You could go larger mass produced aperture and hope you get a good mirror.

Maybe too you would prefer views through an APO refractor. May I suggest a Tele Vue NP-101 or 127. Of course you wont need a Paracorr with either one of them but a 21mm Ethos would be nice.

Back to your Newt; Ethos 21mm + Paracorr Type 2 I think would satisfy most people.

[JJDOBBER79 (Jas)]

Hi Matt and MattT, you have talked me into it I guess I really am searching for a wow factor. I will give binoviewing a go. I have a couple of questions though, hopefully you guys can help,
1.) I understand its a nightmare to get them to work with a big dob. I know I may have to barlow with them which limits the low power achievable, can I, instead of a Barlow, use an extension tube or even a series of them piggybacked if necessary?
2.) what would I do about eyepieces? Would I be correct in saying there is no point using premium eyepieces because the prisms will be cheap Chinese factory glass which will limit the EP's? I think I may have asked this question before but not sure of the answer.
3.) glend recently bought an andrews bino for $99 and he seemed happy with it, is this likely to be an ok choice if I don't want to commit to a binovue? I keep seeing the term BAK4 prisms. If they all have these they should all be roughly the same???? I don't know if the andrews one has this.

[JJDOBBER79 (Jas)]

Also, I have a TV 20mm plossl on the way from the US. Would it be a good choice to buy another one of these?

[astro744]

Originally Posted by JJDOBBER79

Hi Matt and MattT, you have talked me into it I guess I really am searching for a wow factor. I will give binoviewing a go. I have a couple of questions though, hopefully you guys can help,
1.) I understand its a nightmare to get them to work with a big dob. I know I may have to barlow with them which limits the low power achievable, can I, instead of a Barlow, use an extension tube or even a series of them piggybacked if necessary?
2.) what would I do about eyepieces? Would I be correct in saying there is no point using premium eyepieces because the prisms will be cheap Chinese factory glass which will limit the EP's? I think I may have asked this question before but not sure of the answer.
3.) glend recently bought an andrews bino for $99 and he seemed happy with it, is this likely to be an ok choice if I don't want to commit to a binovue? I keep seeing the term BAK4 prisms. If they all have these they should all be roughly the same???? I don't know if the andrews one has this.

A binoviewer will require an extra 120-130mm of inward focus travel. You cannot do this on a standard Newtonian unless you have that much travel available.
The Tele Vue Bino Vue (see http://www.televue.com/engine/TV3b_p...k#.U0jYrFWSySo) comes with two nose-pieces; one offers 1x amplification and the other 2x amplification/correction.

The 1x is for SCT use or special refractors with a shortened tube such as TV-102iis (no longer in production) and the Tele Vue 85mm Bizarro; a special TV-85 with shortened tube for Bino Vue operation (no longer in production).

The 2x is for use on Newtonians and refractors with star diagonal.

Adding extension tubes is opposite to what you need so this will not work.

You certainly will get the wow factor when first seeing a stereo Moon. Note a pair of 24mm Panoptics and your telescope with 2x amplifier will give about 1/2 degree true field at 125x magnification. A pair of 20mm Plossls and your telescope with 2x amplifier will give about 1/3 degree true field at 150x magnification. This would be a great introduction to the Moon in stereo.

Look for a binoviewer with maximum clear aperture, i.e. you don't want a binoviewer with 20mm clear aperture and use an eyepiece with 27mm field stop diameter as you will get vignetting. The 20mm Plossl has 17.1mm field stop diameter whereas the 24mm Panoptic and 32mm Plossl have 27mm.

As far as what quality of eyepieces you use; the view will only be as good as the worst component in the optical chain. This includes telescope, eyepiece, binoviewer, observer, atmosphere and assuming everything is well collimated.

[JJDOBBER79 (Jas)]

So, how do I get that much inward travel to use it only dob?

[Kunama]

Hi Jas, I don't know enough about them yet to advise on their use on Newts. I think MattT can answer that better.

As for eyepieces I would suggest trying it with some cheapies until you're sure you want to use them regularly. One thing to remember is that the bulkier eyepieces do not work for everyone, it is best to try them before buying. The determining factor is your interpupillary distance and also you need room for your nose, especially with short eye relief eyepieces.

The eyepiece focal length needed also depends on the scope and whether you need a Glass Path Compensator in the optical train. I think with newts you will need to use a GPC.
I am using mine at "native" that is I have removed a section of my refractor OTA 105mm in lengths which corresponds to the length of the lightpath of the Denkmeier binos. This means that a 12mm performs in the binos same as it would without the binos.

A GPC is a form of 'barlow' in that it multiplied the power of the eyepiece. You would use longer focal length eyepieces with a GPC than without. The difference being the GPC factor.

I strongly suggest trying the cheaper ones like the WO or similar before splurging out for the Denkmeiers, Baader Mk Vs etc. Perhaps try to attend a viewing evening and try someone else's first (bit difficult around Lismore perhaps, although I know around Nimbin they have parties where everyone sees stars)

[astro744]

Originally Posted by JJDOBBER79

So, how do I get that much inward travel to use it only dob?

In the case of the Tele Vue Bino Vue you have to use the 2x amplifier/corrector. With other brands some sort of 2x Barlow amplification is needed. I'm only familiar with the Bino Vue.

[Kunama]

Originally Posted by JJDOBBER79

So, how do I get that much inward travel to use it only dob?

Or You move the Primary mirror up and then use extension tube when not binoviewing

[astro744]

Originally Posted by Kunama

Or You move the Primary mirror up and then use extension tube when not binoviewing

I was going to suggest this but the primary would have to be moved a considerable distance with implications on secondary performance.

[JJDOBBER79 (Jas)]

Yeah.. I don't wanna move my primary. Is anyone out there that is binoviewing with a 12" dob and can save me considerable grief by telling me exactly what I need to acquire to make these binos work. I have about $600 to get this happening.

[Renato1 (Renato)]

I have a Denkmeir Binoviewer set, which requires using different pieces to be attached to the Binoviewer or star diagonal in order for it to work with SCTs, refractors and Dobs. (You can download instructions at their site).

Mine worked fine with my 14.5" dob, but the binoviewer and eyepieces were extremely heavy, requiring a lot more counterweight - which I didn't have, so I basically hand held my dob up to look at the bigger DSOs.

The Denkmeir ones have versions where you move sliders across and change the magnification in the unit while using it, so that you can get several magnifications on a pair of eyepieces. But the magnifications are different, depending on which telescope type is used.

I also have a simpler Takahashi binoviewer, where the eyepieces go in at a 45 degree angle. It basically connects to SCT via SCT thread and to refractors (using 2" to SCT thread adapter). It is easier to attach and use, but the 45 degree eyepiece angle makes it hard to use on anything high up in the sky. It can't be used with my dob.

I guess I'm the exception, I don't get wowed that much using binoviewers - either with my Denkmeir or Takahashi one - rather I think them a nuisance to viewing lots of things in the sky. Some people like looking at the same thing for a lot of time, and I think a binoviewer would suit them better. I think I've only been wowed using them to look at the moon in my C8.

So I don't use them much, preferring to use my 20 or so pairs of binoculars instead. But plenty of people love using them, and you may be one.

Regards,
Renato

[JJDOBBER79 (Jas)]

Thanks Renato, you certainly have some gear (20 pairs????)
I think I am going to give the andrews bino a go as an entry level, can't go wrong with $90. I can get some cheap Denks etc on astromart but would cost $100 to get them here. I still don't know what I need to get it to work, would a different focuser be an option and if so, what would that mean for single ep viewing?

[JJDOBBER79 (Jas)]

I'm thinking I could get a low profile focusr and just use an extension tube when single ep viewing, would this work?

[JJDOBBER79 (Jas)]

Something like this???

http://www.cloudynights.com/classifi...&cat=20&page=2

[MattT]

Jas you sure move quick!
I wouldn't buy the focuser you linked to. From what I have read it isn't that good. Much better to get a Feather Touch, Moonlite or a Baader Steel Track.
If I were you I'd read the threads on dobs and bino's on CN binoviewer forum. There is a lot to read…a whole lot. It seems that dobs that are solid tube or fixed UTA need some type of OCS, my 10" Newt does.
Look at the useful links on the BV CN forum too, there is a lot of info on the different types of binoviewers and what eyepieces vignette etc etc etc
So if you get the Andrews bino's, get a pair of GSO 25mm plossls, good and cheap and will give the max TFOV with this bino, and if you don't have a 2x 1.25" barlow get the GSO one…good and cheap Keep your focuser!
That'll get you started for under $200. The barlow nose piece can be taken off and screwed onto the nose piece of the bino's for a little less magnification.
You won't need a Coma Corrector with bino's either.
It's not high end stuff but should work.

Matt

[JJDOBBER79 (Jas)]

Thanks Matt,
Let me get this straight, you are saying that all I should need is the andrews bino, 2 x gso plossls and this combined with my 2 x TV Barlow should bring my 12" lightbridge to focus with the stock focuser? You don't think I need anything else in the chain?

[casstony]

For a dob you're best option is a used Denk II supersytem from Astromart. This gives you a greater clear aperture through the binos and the proper 2" optical corrector allowing focus at lower powers. It's probably not hard to find with owners upgrading to the Binotron.

The cheaper Chinese binoviewers are perfectly adequate for use with refractors and SCT's.

Moving mirrors up tubes is not worth mucking around with since an f/5 light cone doesn't work well with the narrow aperture and long light path of the binoviewer - you need f/7 or slower.

[MattT]

Should work yes….the only but is the 2x might not be enough, in which case the next step is a 2.5x, but I doubt you'll need it. Today I'll try my Newt with a 2X barlow and measure the difference between that and the 1.6 OCA.

Tony is right though it's a bit more of an expense.

[JJDOBBER79 (Jas)]

How about this, I need a 3x Barlow for my ep collection anyway to achieve all the fl's I want so, if I order a bino, the pair of plossls and a 3x Barlow. I will have a 2x and a 3x so I should be able to get it going. Tony, I've been looking at binos from the us but postage is going to be huge.

[casstony]

Originally Posted by JJDOBBER79

Tony, I've been looking at binos from the us but postage is going to be huge.

probably about US$50 or so for USPS Priority Mail International.