6" Wide Field REFRACTOR BINOSCOPE

[CHAMACO]

I'm considering to build a nice all-round wide field 150mm binoscope, mainly to observe DSOs and, why not, some planet observations.

The priority is wide field observation with good contrast at 5 pupil exit, and also good contrast on smaller DSOs at 2-3 exit pupil, so I guess the focal length should be 900mm at maximum. I don't mind too much some chromatic aberration observing the moon and planets at 100 X, I'm not aiming higher than 100-150 X for planets.  I want this binoscope to be a keeper for life.

I'm considering these refractors, and I would like to hear your suggestions and recommendations based on your expertise:

(1) TS 152mm F5.9 http://www.teleskop-express.de/shop/product_info.php/language/en/info/p2229_TS-152mm-f-5-9-Gro-feld-Refraktor-mit-3--Crayford-Auszug.html

(2) iStar WFX 150mm F5 http://www.istar-optical.com/refractors-ii.html

(3) Celestron Omni 150mm F5 http://www.teleskop-express.de/shop/product_info.php/info/p4010_Celestron-Omni-XLT-1590R-Rich-field-Refractor---Optical-Tube-Assembly.html

I plan to use high end 2" barrel eyepieces, like Ethos 13 for the 2-3 exit pupil views, and other eyepieces suited for binoscopes (less that 6.2 cm diameter) for the 5 exit pupil range. Which pair of refractors do you think will do the job better and more cost-effectively? I'll consider other refractors you may suggest.

Thanks in advance

[Stu]

I think @Peter Drew could be your man for this, in more ways than one!

http://www.astrobuysell.com/uk/propview.php?view=120851

[nightfisher]

As above, Peter Drew knows a huge amount on this subject, are you planning to buy 2 refractors or use a binoviewer in one scope

[spaceboy]

I pondered a similar idea a while back. Due to the money involved I had to make sure in my mind what I'd be letting myself in for. Where I felt I may slip up is diopter. I'm sure there is some device out there that tackles the need to focus both eyes individually in a bino scope set up but binoviewing is already an expensive game when you only use one scope and can't reach ideal focus. The thought of chopping 2 ota and having trouble focusing both eyes wrote the idea off for me. You also have to consider a mount as there isn't going to be one commercially available so your going to pay that bespoke price. I have no doubt it would be a truly fantastic setup if you can acheive it but at what cost? An f/5 achro is going to be demanding and once you get over the whole wow factor your going to notice these demands more and more.

Personally I feel a 10" Newtonian bino scope set up for be far better consideration and probably easier to do in the long run. I also feel it would be easier and more comfortable to use. Huge yes but just think of those views and for probably similar outlay. A dual dob mount could be made with DIY skills and some ply but an AZ refractor mount may not be so easy to knock up.

I don't want my comments to put you off as I think it would be dead cool to have a bino scope but as I have already gone over the same thoughts I wanted to let you know what my conclusion was. 

[mikeDnight]

Peters definitely your man! I think he has a pair of 6" F5's for sale. I've used them many times and they are superb!

Mike

[Chris]

17 minutes ago, spaceboy said:

I pondered a similar idea a while back. Due to the money involved I had to make sure in my mind what I'd be letting myself in for. Where I felt I may slip up is diopter. I'm sure there is some device out there that tackles the need to focus both eyes individually in a bino scope set up but binoviewing is already an expensive game when you only use one scope and can't reach ideal focus. The thought of chopping 2 ota and having trouble focusing both eyes wrote the idea off for me. You also have to consider a mount as there isn't going to be one commercially available so your going to pay that bespoke price. I have no doubt it would be a truly fantastic setup if you can acheive it but at what cost? An f/5 achro is going to be demanding and once you get over the whole wow factor your going to notice these demands more and more.

Personally I feel a 10" Newtonian bino scope set up for be far better consideration and probably easier to do in the long run. I also feel it would be easier and more comfortable to use. Huge yes but just think of those views and for probably similar outlay. A dual dob mount could be made with DIY skills and some ply but an AZ refractor mount may not be so easy to knock up.

I don't want my comments to put you off as I think it would be dead cool to have a bino scope but as I have already gone over the same thoughts I wanted to let you know what my conclusion was. 

Snap! I went through the same thought process a few years back and concluded pretty much the same, i.e. Expensive and very tricky, and for a large instrument I would go for the dual tube Dob design. For a smaller binoscope a pair of small ED/apo fracs would be nice, I think this would be a lot more manageable than a giant pair of Achromats. 

I've found it easier in the past to just use big binos for low power, and  binoviewer plus scope for high power.

[CHAMACO]

Thanks guys for your input. Definitely the 10-12" dobson binoscope is on the cards, or maybe just one big dobson about 25" when my future observatory is ready. But now I just want to enjoy wide field views with a portable refractor binoscope with the maximum aperture possible. And that means a maximum of 6" or lower, to be portable. Forget binoviews with just one tube, I want two tubes, and focus the two tubes individually. 

[CHAMACO]

5 hours ago, mikeDnight said:

Peters definitely your man! I think he has a pair of 6" F5's for sale. I've used them many times and they are superb!

Mike

Thanks Mike, could you send me pics and features of the two refractors on sale?

[CHAMACO]

6 hours ago, nightfisher said:

As above, Peter Drew knows a huge amount on this subject, are you planning to buy 2 refractors or use a binoviewer in one scope

Two refractors, one for each eye... My eyes are very selfish and don't want to share views with any binoviewer.

[CHAMACO]

5 hours ago, spaceboy said:

 An f/5 achro is going to be demanding and once you get over the whole wow factor your going to notice these demands more and more.

 

Thanks for your comments Sapeceboy. That's why I'm considering F6 (the TS refractor), or the F5 iStar which according to reviews looks like something between a normal refractor and ED/Apo. Looks like lower chromatic aberration in these 2 scopes.

[CHAMACO]

6 hours ago, Stu said:

I think @Peter Drew could be your man for this, in more ways than one!

http://www.astrobuysell.com/uk/propview.php?view=120851

Thanks for the reference. Definitely looks like Peter Drew is the man here to build binoscopes. I also know about Matsumoto in Japan. The alt-azimuth mount he uses is really smart, and would work perfectly with the two 6" refractor OTAs. 

[spaceboy]

10 minutes ago, CHAMACO said:

 I want two tubes, and focus the two tubes individually. 

I'm not sure this would work though. It's my understanding correct or not that the focusers work in tandem you then require some sort of a diopter (unless you have 20/20 vision). Focusing the scopes seperatly is going to move the position of the eyepiece. You just want to move the focal point not the eyepiece, as your going to struggle to comfortably use two eyes with the eyepiece going "up and down" as you try to reach focus in both eyes. Your eyes are in a fixed position after all. Hope that makes sense? I assume you could use some sort of helical focuser fitted to a T thread on a baader diagonal and then space out the other side?? 

[mikeDnight]

29 minutes ago, CHAMACO said:

Thanks Mike, could you send me pics and features of the two refractors on sale?

PM sent

[Stu]

29 minutes ago, CHAMACO said:

Thanks Mike, could you send me pics and features of the two refractors on sale?

They were in the link I posted originally, from ABS