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Equipment Discussions >> Binoviewers

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pftarch
professor emeritus


Reged: 09/21/07

Re: WO BV in 10" Dob? new [Re: johnnyha]
      #6039106 - 08/21/13 08:32 PM

What eyepieces were you using? I ask this because if you are using a high or even moderate power eyepiece and you are using a 2" Barlow, the final Barlow effect would be more like 5x. If you are using 20 mm eyepieces at 5x you are getting up around 300x on your scope. At those powers conditions may not let you focus even in mono mode.

I will say that I am surprised that the extension tube with the 1.6 Barlow didn't work. For me the longer the extension tube or Barlow power the easier it is to focus. The problem being that the resultant magnification increase makes the views unusable, or extreme limited. I also doubt that a low profile focuser will give you enough back focus.

Peter T


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: WO BV in 10" Dob? new [Re: pftarch]
      #6039718 - 08/22/13 08:30 AM

Hi Peter, I was using the supplied 20mm EP in it. Yes the 1.6x would not come to focus even If I added more extension tubes, which I think is going the wrong way anyway. The 2x barlow was the short type and that did not work either.

I sent this question over to WO and they came back with this reply. Seems they don't have a solution either!

"Many telescopes, especially Newtonian reflectors, do not have sufficient back-focus to achieve focus with such an optically long accessory. By using a barlow, the focal point of the telescope can be extended sufficiently to accommodate the length of the binoviewer.


We recommend first choosing the lowest powered barlow that will allow your scope to reach focus. This will permit the widest possible field of view. In addition, one or more higher powered compensators can be added to give a greater range of magnifications.

You already tried 1.6x and you also can try 2x barlow for Binos.

It would be easier if you check with your telescope maker if the model you have bino friendly or not.

Best regards,

Tim

WO


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: WO BV in 10" Dob? new [Re: REC]
      #6039900 - 08/22/13 10:54 AM

Ok, update...I just spoke to Russ at Denkmier and told him I needed an adapter OCS for my Denk2 and so he is sending me that and the middle spacer for my Dob and that's that I guess. Since I can't get the WO to focus with the Dob even though it a lighter set up, I'm just going to sell the WO and be done with it.

He told me that with my 20mm EP's I would get about 80x as the lowest power, so that sounds good. I'll use the 26SP for lowest power and brighter EP for DSO's

Stay tuned!

Bob


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MaestroMyth
professor emeritus
*****

Reged: 02/16/06

Loc: CT
Re: WO BV in 10" Dob? new [Re: REC]
      #6041058 - 08/23/13 12:17 AM

i had the same problem as you with my WO binoviewer and solved it, thanks to help from this forum. i ordered this from siebert optics:

http://www.siebertoptics.com/Burgess125xto3x.html

i use this with my A12 and my WO binoviewer. works great, and i get three magnification options.


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SkyGibbon
super member


Reged: 02/09/13

Loc: Las Vegas, Nevada
Re: WO BV in 10" Dob? [Re: johnnyha]
      #6041121 - 08/23/13 01:32 AM

I was able to achieve focus by Attaching three unused filter cells (with filter glass out of course)to bino nosepiece and screwing on the 2x element of a shorty barlow to the end of filters. When I switched to a low profile focuser, I was able to do the same with the 1.6x corrector that came with the WO viewers. You will have to move mirror up to do it without any correctors.

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REC
Post Laureate
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Reged: 10/20/10

Loc: NC
Re: WO BV in 10" Dob? new [Re: MaestroMyth]
      #6041337 - 08/23/13 07:27 AM

Thanks for the tip! As of now, I think I'm just going to see how the Dob setup for my Denk works out before I spend any more money for tubes ect. for the WO BV.

Just to be clear with this Siebert fix, you are using a combination of tubes ans some kind of glass element as well?


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MaestroMyth
professor emeritus
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Reged: 02/16/06

Loc: CT
Re: WO BV in 10" Dob? new [Re: REC]
      #6044369 - 08/24/13 10:56 PM

yes, REC, that's correct. i might be reading into your question here somewhat, but if you're concerned about adding all those glass elements to the light path, and any possible image degradation, there is little to no drop off in crispness in my system. i know that sounds impossible, but i've tried it both ways. the siebert OCS is a great fix for our problem.

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Relativist
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Reged: 10/11/03

Loc: OC, CA, USA
Re: WO BV in 10" Dob? new [Re: MaestroMyth]
      #6045471 - 08/25/13 04:22 PM

Same exact setup I use. It even let me use my WO with a Firstscope

http://www.celestron.com/astronomy/series/firstscope-telescope/?cat=4

No kidding.

That said, you also have another BV set to try, and it probably makes sense to only keep one.



Quote:

i had the same problem as you with my WO binoviewer and solved it, thanks to help from this forum. i ordered this from siebert optics:

http://www.siebertoptics.com/Burgess125xto3x.html

i use this with my A12 and my WO binoviewer. works great, and i get three magnification options.




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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: WO BV in 10" Dob? new [Re: MaestroMyth]
      #6046511 - 08/26/13 07:53 AM

Ok, than that's what I need then, thanks! So next question to resolve this whole BN business and to get down to observing, is what to keep?

I have been testing a Denk 2 PS with my 8" SCT and trying to determine a basic question, what looks better in the EP? So far I'm have a hard time choosing. Next up is to see how well the Denk performs in my 10" Dob.

Last night I was using M13 as an acid test and the Denk was not doing to well with it. M13 was directly overhead in an area of least LP and I could not resolve stars in it like I can in Mono. If we get another clear night this week, I'll do a side by side with both BV on some of the brighter DSO's


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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: WO BV in 10" Dob? new [Re: REC]
      #6046563 - 08/26/13 08:55 AM

If you are configured properly, the difference between binoviewing and non binoviewering for DSOs should be very subtle and hard to see. If there is an obvious difference, then I suspect something is wrong.

Are you using a 2" diagonal?

The problem with using a 2" diagonal with something like a powerswitch (or even without the powerswitcy) is that the system can loose apeture.

When the light path is very long, the primary has to be moved so far forward that the light cone widens so much the baffle on the secondary miorror starts to shave off the outside of the light cone so that aperture is reduced.

The other consequences are that the central obstruction becomes larger by percentage and the excessive back focus induces spherical aberration into the system.

If you are using a 2" diagonal and a typical visual back with 40mm of light path, along with binoviewers, your light path is about 270mm.

This will reduce your apeture to maybe 7.3".

If you are using this configuration with a powerswitch, you add about 18 mm to this, which reduces the apeture another .2".

And when you slide in the powerswitch low power arm, your apeture drops to about 6.7" or so,

I would not avoid using a Binotron or similar system in an SCT because the effect is least when you are in high power mode (double Barlow), but as you can see, there is a compromise.

If you are using a 2" diagonal, you can save qite a bit of back focus by converting your system to work with a short visual back and short light path diagonal.

What I recommend are the Televue Short Visual back and the Baader T2 Prism. These will save you about 60mm of light path, restoring about .6" of apeture to each of the figures above.


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: WO BV in 10" Dob? new [Re: Eddgie]
      #6046745 - 08/26/13 10:51 AM

Hi Ed, yeah it's me Bob again and still trying to work out all of this back focus problem and yes, still using the 2" Diagonal and the 32mm OTA with it.

I did not try the reducer arm in it because you had told me that will reduce my aperture even more! Just looking straight through with a pair of 26mm SP. The view was still dim and could not quite resolve any stars in M13.

Next I am going to try the WO BV and see if there is any change and then, use a 1.25" diagonal with the stock OTA that came with the scope. That would be the shortest light path of all at 24mm long.

I am also waiting for the OCA from Russ to use my Denk on my new 10" Dob and hoping that will show a big increase on DSO's.

Bottom line for BN is two fold. One I like the views of the Moon and planets for sure! Two, my right eye is not quite as good as my left eye on DSO's. With my left, I can see a little bit better on faint stars and also it has better contrast and shows a little darker background. I am hoping by using both eyes, this will give me a more pleasing overall view and yes, a lot more comfortable.


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Relativist
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Reged: 10/11/03

Loc: OC, CA, USA
Re: WO BV in 10" Dob? new [Re: REC]
      #6047690 - 08/26/13 08:51 PM

between the WO BV and the Denkmeier 2, the Denk has a larger clear aperture, which will will allow for wider FOV, hence why Siebert has 'supercharge' services for less expensive BVs.

http://www.siebertoptics.com/SiebertOptics-Binoviewer%20Upgrade.html

If you find that you like BVs, then you might want to keep the Denks.


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Epsilon_Lyrae
member
*****

Reged: 07/27/11

Re: WO BV in 10" Dob? new [Re: Relativist]
      #6047868 - 08/26/13 10:37 PM

You used WO binoviewers with a Siebert OCA in a Firstscope mini-dob? How did you manage that - did you only use part of the OCA? I remember trying that when I first bought my binoviewers, but it looked like the OCA would hit the secondary mirror, so I gave up. Maybe I'll have to take another look at that!

Quote:

Same exact setup I use. It even let me use my WO with a Firstscope

http://www.celestron.com/astronomy/series/firstscope-telescope/?cat=4

No kidding.

That said, you also have another BV set to try, and it probably makes sense to only keep one.





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Relativist
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Reged: 10/11/03

Loc: OC, CA, USA
Re: WO BV in 10" Dob? new [Re: Epsilon_Lyrae]
      #6047984 - 08/26/13 11:45 PM

Quote:

You used WO binoviewers with a Siebert OCA in a Firstscope mini-dob? How did you manage that - did you only use part of the OCA? I remember trying that when I first bought my binoviewers, but it looked like the OCA would hit the secondary mirror, so I gave up. Maybe I'll have to take another look at that!




Be very careful if you do, if they touch then you could scrape the OCA lens or coating! I used the 1.25x setup. I was trying to get a large FOV, and I did...

P.S. that's why I didn't post pics or talk about it much, I don't recommend it.


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Epsilon_Lyrae
member
*****

Reged: 07/27/11

Re: WO BV in 10" Dob? new [Re: Relativist]
      #6048010 - 08/27/13 12:11 AM

Ha ha - you're careful not to say much, then mention it in an unrelated thread, and I immediately want to try it! Thanks for warning.

Anyway, I've used the WO binoviewers in a 10" dob, but I had to use the Siebert OCA.

Quote:



Be very careful if you do, if they touch then you could scrape the OCA lens or coating! I used the 1.25x setup. I was trying to get a large FOV, and I did...

P.S. that's why I didn't post pics or talk about it much, I don't recommend it.




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Relativist
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Reged: 10/11/03

Loc: OC, CA, USA
Re: WO BV in 10" Dob? new [Re: Epsilon_Lyrae]
      #6048152 - 08/27/13 02:57 AM

Quote:

Ha ha - you're careful not to say much, then mention it in an unrelated thread, and I immediately want to try it! Thanks for warning.

Anyway, I've used the WO binoviewers in a 10" dob, but I had to use the Siebert OCA.





yea, main point i was trying to make is that the OCA works. The way I did it is racked in the focuser so it was as close to the secondary as I was comfortable with, then focused by racking out slowly. Because damage might happen if someone just racks in, I don't really share the views when I do this.


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