Jump to content


Photo

WO BV in 10" Dob?

  • Please log in to reply
35 replies to this topic

#26 REC

REC

    Fly Me to the Moon

  • *****
  • Posts: 5139
  • Joined: 20 Oct 2010
  • Loc: NC

Posted 23 August 2013 - 06:27 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?

#27 MaestroMyth

MaestroMyth

    Viking 1

  • *****
  • Posts: 514
  • Joined: 16 Feb 2006
  • Loc: CT

Posted 24 August 2013 - 09:56 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.

#28 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4113
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 25 August 2013 - 03:22 PM

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

http://www.celestron...elescope/?cat=4

No kidding.

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



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.siebertop...ss125xto3x.html

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



#29 REC

REC

    Fly Me to the Moon

  • *****
  • Posts: 5139
  • Joined: 20 Oct 2010
  • Loc: NC

Posted 26 August 2013 - 06:53 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

#30 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 12651
  • Joined: 01 Feb 2006

Posted 26 August 2013 - 07:55 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.

#31 REC

REC

    Fly Me to the Moon

  • *****
  • Posts: 5139
  • Joined: 20 Oct 2010
  • Loc: NC

Posted 26 August 2013 - 09:51 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.

#32 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4113
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 26 August 2013 - 07:51 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.siebertop...er Upgrade.html

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

#33 Epsilon_Lyrae

Epsilon_Lyrae

    Sputnik

  • *****
  • Posts: 31
  • Joined: 27 Jul 2011

Posted 26 August 2013 - 09:37 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!

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

http://www.celestron...elescope/?cat=4

No kidding.

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



#34 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4113
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 26 August 2013 - 10:45 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!


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.

#35 Epsilon_Lyrae

Epsilon_Lyrae

    Sputnik

  • *****
  • Posts: 31
  • Joined: 27 Jul 2011

Posted 26 August 2013 - 11:11 PM

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.


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.



#36 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4113
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 27 August 2013 - 01:57 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.


:lol: 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. :p






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics