4 replies to this topic

[Baatar]

Which is better?

 

I like using BVs on both ST120 for low power scanning, and 100mm apo for planetary observing.

 

I know about light splitting 50/50, thus image getting dimmer, partly compensated by summation effect, increased comfort and all such.  Although, I like binoviewing everything, I do understand people's preferences to monoview DSOs.

 

ST120 binoviewing becomes like roughly using 90mm binoscopes.  But I still have full resolution of 120mm aperture, right?  And the image is just dimmer as looking through 90mm?

 

If you can't detect galaxies with 100mm mono, but you could detect with 120mm, using BVs on the latter just dims the image but you are still using the light gathering and resolving power of 120mm?

 

For DSOs, what do you prefer? 120mm aperture with BVs or 100mm mono?  What is the theory and what is your actual expereince?

 

 

Edit:  I know this is achro vs apo, different focal lengths and F ratios, but I don't want to get into discussion on CA and which one is better optically and such.  Just comparing aperture sizes and pros of using a slightly larger aperture with BVs against using smaller aperture monoviewed.  In this case, would aperture difference of 20mm really make any difference?

 

Edited by Baatar, 19 February 2025 - 11:11 PM.

[ngc7319_20]

 

ST120 binoviewing becomes like roughly using 90mm binoscopes.  But I still have full resolution of 120mm aperture, right?  And the image is just dimmer as looking through 90mm?

 

If you can't detect galaxies with 100mm mono, but you could detect with 120mm, using BVs on the latter just dims the image but you are still using the light gathering and resolving power of 120mm?

 

For DSOs, what do you prefer? 120mm aperture with BVs or 100mm mono?  What is the theory and what is your actual expereince?

 

 

Edit:  I know this is achro vs apo, different focal lengths and F ratios, and I don't want to get into discussion on CA and which one is better optically and such.  Just comparing aperture sizes and pros of using larger aperture with BVs against using smaller aperture monoviewed.  In thus case, would aperture difference of 20mm really makes any difference?

Binoviewer with 120mm is roughly like 85mm binoscope in terms of image brightness.  Yes, binoviewer with 120mm has resolution of 120mm scope.

 

I like binoviewer for DSO for the viewing comfort and experience.  But which goes deeper -- 100mm mono or 120mm with bino I can't say.  I have pretty good grasp of the optics and physics, but don't know enough about visual perception.  I just like the binoview better.

[betacygni]

Comparing mono to bino can get tricky. Even if mono (or larger aperture) wins in pure light gathering capability, contrast can be significantly better with two eyes. The DSO can “pop” from the background better with two eyes. Brute aperture will of course eventually bypass this, but it plays a role.

As for my preference, I always prefer two eyes. Aperture is secondary. I don’t find deep space objects just barely within reach of a given aperture very interesting anyway, so I’d rather two eye view for comfort and immersion than hunt for the faintest of fuzzies. There is always going to be a larger telescope that can go a little deeper, the key is what views do you enjoy the most. Seeing more isn’t always seeing better.

[balcon3]

Which is better?

 

I like using BVs on both ST120 for low power scanning, and 100mm apo for planetary observing.

 

I know about light splitting 50/50, thus image getting dimmer, partly compensated by summation effect, increased comfort and all such.  Although, I like binoviewing everything, I do understand people's preferences to monoview DSOs.

 

ST120 binoviewing becomes like roughly using 90mm binoscopes.  But I still have full resolution of 120mm aperture, right?  And the image is just dimmer as looking through 90mm?

 

If you can't detect galaxies with 100mm mono, but you could detect with 120mm, using BVs on the latter just dims the image but you are still using the light gathering and resolving power of 120mm?

 

For DSOs, what do you prefer? 120mm aperture with BVs or 100mm mono?  What is the theory and what is your actual expereince?

 

 

Edit:  I know this is achro vs apo, different focal lengths and F ratios, but I don't want to get into discussion on CA and which one is better optically and such.  Just comparing aperture sizes and pros of using a slightly larger aperture with BVs against using smaller aperture monoviewed.  In this case, would aperture difference of 20mm really make any difference?

You have both. What is your opinion? For galaxies, which are extended objects, the important thing for detecting them is brightness and contrast, not resolution. You need enough aperture to detect them, and enough contrast to distinguish them from the background sky. To increase brightness, increase aperture (for a given magnification). To increase contrast, go to a darker site. In my experience, binoviewing really helps with detecting faint extended objects like galaxies. So as long as the brightness is about the same, I would always go with the binoviewer. For open and globular clusters, I like to see as many stars as possible, and bright colors, so I would always go for the largest aperture, which would give the best limiting magnitude for stars.

[Jon Isaacs]

I think this depends on the two instruments involved. An ST-120 is optically compromised at higher magnifications. It may also require an optical path length corrector. 

 

The maximum possible field of view with 1.25 inch eyepieces and a 600 mm focal length is about 2.6°. The maximum possible TFoV withy favorite 4 inch refractor for deep sky is 4.9°.  It's also optically much better at high magnifications.

 

How the higher power views compare, I'm not sure. But for me, 4 inch deep sky is not about small galaxies, it's about those things that a 4 inch scope does best, low power wide field and the NP-101 does that better than just about any scope you can buy.

 

How one observes, the skies, the other scopes involved, the observers preferences..

 

In my situation, under dark skies, my refractors are setup alongside some powerful deep space scopes so viewing 10th-11th magnitude galaxies in a 4 inch is an interesting exercise but somewhat futile. Sometimes I'll look at a galaxy cluster like Hickson 68, it has three galaxies from magnitudes 10.9 to 11.4 and that are 14.0 and 14.6. Viewing them in a Dob, helps me see the three brighter galaxies in the 4 inch.

 

Jon

Edited by Jon Isaacs, 20 February 2025 - 11:21 AM.