Quark Binoviewing

[Pig]

Gordon.... I think you have to divide the F15 - 30 by the built in 4 x Barlow impact and maybe the spread of the fine tuner..... this still does not make total sense as it would only apply to the top end. I think someone has just plucked a "central"  figure out of the sky. Magnification aside I see no massive difference between my F5 & F7.

[Floater]

I agree, Shaun. The Barlow effect is x4.2. However, even using that and throwing the numbers around I can't find anything pointing to f7.5 as a 'sweet spot'.

As you wrote earlier, aperture and eyepieces seem to be the factors which are far more important than focal ratio, provided one stays within the limits.

I'm happy with how my Quark operates but was/am just curious how the f7.5 figure seemed to be accepted without explanation or query. So I queried it ...??

[Stu]

27 minutes ago, Floater said:

I keep reading in this thread the statement that f7.5 is the 'optimum' for a Quark. Where does this figure come from?

The manual states: so we need to alter your telescope’s F/ratio in order to reach F/15 to F/30 where your DayStar will operate correctly. Best performance is at F/27-F/32 

If we are referring to the scope's basic, original f-ratio, elsewhere in the manual it states that the Quark is best suited to scopes with a focal ratio of f5-f9. The median there would be f7. So can someone please explain why f7.5 keeps cropping up?

I suspect it's one of those cases where someone has quoted a figure which seems about right, and everyone has repeated it!

If you take the mid point of 27 and 32 you get f29.5. Divided by the x4.3 Barlow in the Quark and you get f6.8 which should be the optimum.

Given that the aim of the game is to get the light beam going through the Quark as parallel as possible, I've always thought that erring on the long side of the focal length range would be better.

I have seen definite differences in performance, particularly if you go down to much shorter focal lengths, the contrast drops off. I found that with my Quark (now sold), at the optimum focal length, the surface contrast was better because the bandwidth was tighter but also the banding which was a 'feature' of my quark showed up more. I believe later Quarks were shipped with a wider band pass so the banding tolerance did not show up as much.

[Pig]

I agree guys... the problem with differing F ratios is that in most cases you are changing the important factorial dynamics (refractors) IE my f5 has 80mm aperture and my f7 has 110mm so straight away brightness has its impact, then you add into the mix differing focal lengths of eyepieces, filters and so on...... so maybe all these differing permutations contribute as to where f7.5 comes from !!!! Simply middle ground numbers

[Pingster]

An update. I think ive discovered why turning the binoviewer in the quark is required to "match" the brightness thru each eyepiece....

The mrk5 bino like most is polarized! I think the quark is also polarized becuse i have no issues with WL solar and ive never had an issue binoviewing at night.

You can test by removing the eyepieces from the bino and looking thru one barrel at a time at an LCD TV and rotating the bino. You will clearly see one side dims with less roatation than the other.

This answers my long standing issue. Using the bino during the day... i had noticed that one barrel in the bino showed a different highlight on objects to the other. I persionally find this extremely distracting and strains the eyes. Annoyingly this issue is barely present in my cheaper WO bino!

The question is.. can the mrk5 polarization be matched on both barrels?

http://www.cloudynights.com/topic/500910-mark-v-polarized-on-one-side/

[Stu]

54 minutes ago, Pingster said:

An update. I think ive discovered why turning the binoviewer in the quark is required to "match" the brightness thru each eyepiece....

The mrk5 bino like most is polarized! I think the quark is also polarized becuse i have no issues with WL solar and ive never had an issue binoviewing at night.

You can test by removing the eyepieces from the bino and looking thru one barrel at a time at an LCD TV and rotating the bino. You will clearly see one side dims with less roatation than the other.

This answers my long standing issue. Ising the bino diring the day... i had noticed that one barrel in the bino showed a different highlight on objects to the other. I persionally find this extremely distracting and strains the eyes. Annoyingly this issue is barely present in my cheaper WO bino!

The question is.. can the mrk5 polarization be matched on both barrels?

http://www.cloudynights.com/topic/500910-mark-v-polarized-on-one-side/

That's very interesting Pingster. I assume you use solar film to observe in white light, because a Herschel wedge also polarizes the light passed through it.

I have a pair of Mark IV Zeiss binoviewers and do not see any difference in brightness when using a Baader Herschel Wedge, so I assume the polarization is matched in the two channels in the Mark IVs?

[Pingster]

Hi Stu.

I have both baader film and a Lunt solar wedge. So far using the wedge i have not noitced any difference.  

But the polazation effect is deffo there when using the quark and when binoing during the day. 

From what i have read the baader maxbright bino has no polarization/minimal... if so im going to buy one for daytime viewing and maybe quark.  

[Peter Drew]

I don't think you will get even brightness both sides of a binoviewer, the beam splitter typically does a 60/40 split although 60+40 is 100 so this is what you see using both eyes. 

[Pingster]

Hi Peter.

I have a WO unit and the Mrk5 and the light distribution is pretty much perfect vjsually across both of them. The Mrk5 is epseically know for perfect split.

The issue is polarization with is different and results in differences in highlighted edges on day tome viewing. For example both eyepieces will be exactly the same brightness... but the highlighted edge of a tree branch will be x2 brighter in one eyepiece. The same is seen on the highlights of waves on the sea. Most people may never notice it.

In the quark the polarization makes one eyepiece look about 50% less bright... but it can be fixed by rotating the quark.