Posts Made By: Glen Scott

The bright objects make your pupil constrict and the smaller hole that light has to enter into your eye may make it more difficult to merge the images. At this point all I can suggest is to try rotating one or both eps in their holders to see if it helps. You could double check to see if both eyes are seeing a focused image, even a little bit of focusing difference between your eyes can upset the merging process. I don't know if Russ offers the individual
diopter adjustment as a retrofit option on the DenkI but it
might help if this part of the problem. Good luck,Scotty

Tom,you might keep half an eye on the Astromart classifieds.
There are currently 3 Denkmeiers for sale over there, two
standards and one premium. I think there have been a couple
of Denk 2's in the the last couple of months. I believe a bargain could be had if you were patient.

Guy,can you see any showpices of the southern hemisphere
like the Carina nebula,LMC,SMC,or the Omega Centauri globular cluster from your location. I will live vicariously through your observing reports from my more northernly observing latitude. Please keep us posted and welcome to the world of two eyed astronomy. Clear Skies and less dew, Scotty

Nope, your math is fine.See Tom Holes post,copied here in it's entirety,Re: .3 magnitude equals what ?
Posted by Tom Hole on 12/22/2003 6:56:04 PM

Glen,

I can't put a mag figure on the difference. My test was one night with my Denk stds with the 2" OCS and the TV binovues with the TV 2x corrector. Used 2 GTO zoom ep's. The target was M57. There was a star just above M57 (below in the ep) that was right on the limit of my vision with the Televues. It required averted vision to detect in the TV's. But with the Denks at the same magnification, it was visible with direct vision. Not easily visible, but visible with direct vision. This led me to comment on the Denks stds with 2" OCS going a bit deeper than the TV binovues with 2x corrector. I do not have any idea what mag difference that might be.

I'm sure this test was rife with potential errors. Mismatched mags (I was using a pair of zoom ep's) could have easily made the difference. I had measured the actual magnification of the Denks with the 2" OCS and the Binovues with the 2x corrector during the day. The Denks/2" OCS were actually 1.37x mag. The TV was 2x. So I felt very comfortable selecting a zoom setting, but who knows how accurate the markings on the zoom were.

The folks that can really nail this down are the SCT users. Correctorless binoviewer testing is a good basis for data with respect to the binoviewers themselves. Testing on a newt with a corrector at potentially differenct mags introduces a lot of variables that are difficult, if not impssible, to isolate.

So, that's my data. Can't explain it. Don't need to, really since I still have both of them. Maybe if I sell one, the other one will suddenly start getting grander laurels

Clear skies,

Tom

Floyd, your participation on this or any other forum is not a requirement if you purchase a binoviewer. I would not let
the petty bickering that takes place here influence in any way what aspect of amatuer astronomy
I enjoy. You could purchase a binoviewer and enjoy it in the real world and no one here would be the wiser.
With apologies to Shakespeare. This is a forum full of sound and fury signifying nothing. Clear Skies, Scotty

Depending on what you are viewing a moon filter or neutral
density filter may be helpful on brighter objects.
Good luck,Scotty

I will probably get nailed for promoting vaporware,but if you are not in too big a hurry and can wait for the developement of the zoom OCA you could save some money on eyepiece pairs. Regardless of the binoviewer you own the zoom OCA will work with it as it is intended to be universally compatible. You have not mentioned any eyerelief
issues related to your Pentax purchase so I would have to vote for a pair of 24mmPans for starters.
Welcome to the world of two-eyed astronomy. Scotty

Buy this book and study it.Star Testing Astronomical Telescopes by Harold Richard Suiter.It is the definitive work on this subject.Here is a link. http://www.willbell.com/tm/tm5.htm
This book explains everything about the subject and newtonian telescopes.
Also be aware that when your newtonian telescope is slightly out of collimation and is racked a 1/4 turn on either side on focus you will see what looks like astigmatism. That is the star image will elongate first one direction and then 90degrees the other direction on the opposite side of focus. This tells you that collimation is just a little off. Clear Skies,Scotty.

Mark,for your application I can't see any big advantage. A corrector makes a good barlow if you need one.
Depending on the aperture of your MAK and the manufacturer
which both affect how much mirror movement is necessary to reach focus, you may not have increased your magnification by 25%, it could be less,a daytime test of field of view with and without bino at close to infinity focus would give you an accurate measurement. Siebert Optical makes a focal
reducer that can make your combination of MAK and TV bino operate at half the F ratio they would normally have. If you can reach focus with your scope this is kind of a neat accessory to have to look at open clusters and asterisms with. The floater reduction is real and nice to have when viewing the planets. I would say you are good to go,welcome to the the two eyed universe, Scotty

Milton,I have not seen this problem in my Nexstar8 with either the BW Optics or the TV binos. This is of course an
F10 system with a light cone that does not utilize as much of the prism surface area as a steeper light cone.
I have looked for for spherical aberration with my Discovery
15in.F5 truss dob with my BW Optics and Siebert 1.8xOCA
and haven't seen any evidence of it in star testing at 200x.
When I was looking at Globular clusters last May at 185x with my BW Optics 1.8OCA combo M13 just looked wonderful with no softening of the core, cyclopes 12.5in Portaball
users also had no complaints when sharing views with me.
I have not be able to go higher this year due to seeing conditions. When I have used my TV 1.8x OCA combination stars have not looked noticably degraded.I have not checked for it with my TV bino and Siebert 1.3x OCA. in my dob I guess I wasn't too concerned about it. At 150x and below open clusters seemed excellent in sharpness, and contrast on the galaxies in Leo and Virgo was excellent which would not have been the case with significant spherical aberration. The loss of sharpness due to the sheer amout of glass introduced into the optical path is an unavoidable
price that has to be paid if a prism based binoviewer is used. An individuals sensitivity to this phenomenon varies greatly and fortunately I am fairly tolerant of a very small loss of this type. I may not have had the problem with spherical aberration in dob due to the Fratio of the scope after the corrector which is F6.5 and F9. It is also possible that the Siebert Optical correctors deal effectively with any spherical aberration introduced by the binoviewers. I don't think these two issues are necessarily
a Dark Secret,but people who are interested in promoting binoviewing are not going to go out of their way to talk
about any potential downside to purchasing a binoviewer.
For myself the gains in comfort and floater reduction have
outweighed any potential loss of sharpness and spherical aberration has been a no show in my case YMMV.
Scotty