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need advice on Binoviewers

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#1 Nessark

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Posted 09 December 2019 - 08:22 PM

Should i get a pair?  Do they lower the clarity? anything bad about them?  i am tired of straining my one eye, putting my hand on the other, then switching and it just makes astronomy stressful.  I don't wanna look like a pirate either so i don't want to wear an eye-patch. I have a 12" Dobsonian, do binoviewers work well with dobsonians?

 

Also what is a good quality brand that doesn't cost more than $200?

 

I like the Celestron pair but my telescope is a Meade, maybe they wont work together?

 

Thank you!


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#2 TOMDEY

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Posted 09 December 2019 - 08:56 PM

Should i get a pair?  Do they lower the clarity? anything bad about them?  i am tired of straining my one eye, putting my hand on the other, then switching and it just makes astronomy stressful.  I don't wanna look like a pirate either so i don't want to wear an eye-patch. I have a 12" Dobsonian, do binoviewers work well with dobsonians?

Also what is a good quality brand that doesn't cost more than $200?

I like the Celestron pair but my telescope is a Meade, maybe they wont work together?

Thank you!

Well, Nessark, if you want good quality new... change that to $500, and selections begin to appear. The other alternative would be to buy used, here or on AMart... some of those have sold for as little as $325 (used prices ranging from that low one up to $1000++, depending on make, model and features). And the used ones tend to sell fast... so that's where the market is. If your Dobsonian is fast (as most commercial ones are)... you will need a binoviewer that further comprises a front lens to bring it to focus. Orion markets a Linear Binoviewer that provides that feature and creative disjoint pupil sharing, rather than the more common bi-conjugate identical pupil-splitting. That Orion device lists for $500 and works well with a Dobsonian.

 

Bottom line... good and $200 defines the null set.    Tom

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#3 Cali

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Posted 09 December 2019 - 08:59 PM

You may want to blow the cycles and read this thread.

 

Best investment I ever made, well, regar

 

- Cal


Edited by Cali, 09 December 2019 - 09:49 PM.


#4 MalVeauX

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Posted 09 December 2019 - 09:33 PM

I too will suggest you look into Arcturus binos. Inexpensive and fantastic.

 

I don't prefer binos for everything. There are limits. But, the bigger the aperture, the brighter things are, and the brighter the view will be in the binos. So your 12" aperture gives you a lot of room to get lots of light and still see everything nicely even when using binos splitting the light in half (dimming it). I actually prefer binos for solar system bodies. I prefer binos less, for DSO. For DSO, I just prefer a wide eyepiece and low power to get it as bright as I can since they're so dim. Some DSO are bright enough to still be very nice in binos if you have enough aperture. Again you have a 12" aperture so you should be fine.

 

A big thing about binos is that to come to focus on many instruments may require a piece of glass on the nose that magnifies things, like a barlow. The Arcturus comes with a 1.85x screw on barlow nose, this allows you to come to focus with most instruments. So this can change what eyepieces you use. Because of this, you will likely be most interested in the widest, longest focal length eyepieces because they will be adjusted by the 1.85x magnification of the barlow. You'll want a set of basic 32mm plossls or similar.

 

Speaking of eyepieces, there's no need to fret or worry over having to have a set of eyepieces to use. 1.25" eyepieces are affordable, there's lots of quite good ones that are inexpensive, and you will not want the short focal-length ones anyways, so you don't need very many at all. You could frankly do fine with just one or two pairs and that's it! I would look at 32mm plossls (GSO, inexpensive, good), or the ones that come with the Arcturus binos in the first place (30mm plossls, close enough), and then maybe a set of 20mm SWA (Agena SWA are great) or 18~25mm Agena StarGuiders (which are Paradigm Dual ED clones). Inexpensive, great 1.25" eyepieces. And again, consider their focal length with that 1.85x barlow on the nose for the resulting FOV and all that. This is why I prefer binos for solar system. For faint DSO I use the widest 2" eyepiece I can get my hands on.

 

BinoViewing_HA_C8Edge.jpg

 

Solar_150mm_Visual_Quark_Bino.jpg

 

Very best,


Edited by MalVeauX, 10 December 2019 - 08:09 AM.

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#5 TOMDEY

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Posted 09 December 2019 - 10:10 PM

You may want to blow the cycles and read this thread.

 

Best investment I ever made, well, regar

 

- Cal

Wow! Under $200 and with a piar of plossls. And, especially with the slow, gentle feed of an SCT... good choice.    Tom


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#6 outofsight

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Posted 09 December 2019 - 10:50 PM

I second, third, Arcturus. If you're not sure about buying BVs, they're a good place to start, and maybe a good place to finish. I have some very nice Denkmeier BVs, and some Arcturus. Nessark, it sounds like you might appreciate some BVs, if nothing else they are worth checking out just to look at the Moon. With what you've said, you should either look at used or get some Arcturus. Have fun.

 

P.S. Many of us prefer using two eyes.

 

Edit: One thing I just noticed though, there can be some focusing problems with Newtonians, dobs, so you might want to call Camera Concepts and make sure they will be easy to use first. I think the problem can be solved by the nose pieces that come with the Arcturus, or if you have a dob that can be lowered toward the primary mirror, like some SkyWatchers. Just something to check into. Good luck with it.


Edited by outofsight, 09 December 2019 - 10:58 PM.


#7 Tony Flanders

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Posted 10 December 2019 - 06:04 AM

Personally, I find binoviewers uncomfortable and difficult to use, but many people swear by them. Be aware that the real cost of binoviewers isn't the device itself but the fact that it requires you to spend twice as much on eyepieces.

 

I hope that line about not wanting to look like a pirate was a joke. One of the great things about astronomy is that you do it in the dark, so nobody can see you. It's bad enough worrying how your telescope looks; if you worry how you look, it will prevent you from doing all manner of useful things, notably wearing practical warm clothes.

 

Granted, there are a number of perfectly legitimate reasons for not liking eye patches. Personally, I love them. Many people also get used to keeping their non-observing eye open and ignoring the image seen through it.


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#8 Jon Isaacs

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Posted 10 December 2019 - 06:31 AM

Personally, I love them. Many people also get used to keeping their non-observing eye open and ignoring the image seen through it.

 

 

One can also get used to closing the non-observing eye.

 

Personally, I find binoviewers uncomfortable and difficult to use, but many people swear by them. Be aware that the real cost of binoviewers isn't the device itself but the fact that it requires you to spend twice as much on eyepieces.

 

This has been my experience.  You also are limited in the eyepieces you can use, no 2 inch eyepieces and affordable binoviewers do not have the clear aperture to avoid vignetting with 1.25 inch eyepieces that offer the widest fields of view.

 

Also, the image in each eye is 1/2 as bright so when you are pushing the limits, one eye will show more.

 

Jon



#9 Cali

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Posted 10 December 2019 - 09:10 PM

Wow! Under $200 and with a piar of plossls. And, especially with the slow, gentle feed of an SCT... good choice.    Tom

TOMDEY

 

Yeah, when I bought the Orion 127mm Mak they threw in a 25mm Sirius Plossl 1.25" eyepiece. So I picked up a second 25mm Sirius Plossl 1.25" eyepiece on this site just for cheap and WoWiE ZoWiE, the Arcturus bino viewer really cooks with these 2 pieces of glass. (And they did just fine with the included 30mm's) Just remember that the Sirius Plossl has an undercut but they work with no prob in the bino viewer. You can tape the undercut if so desired. As I've said elsewhere, adding this viewer was like turning my MAK into a whole new instrument. (Nice people to deal with and you also get 2 barlows with the viewer).You'll never look at Luna the same way again. Even noticed some better detail on Saturn and Jupiter. Can't beat the price for enhancing your local views.

 

If serious you should read this entire thread

 

- Cal 


Edited by Cali, 10 December 2019 - 11:04 PM.


#10 Volvonium

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Posted 13 December 2019 - 02:33 AM

Before jumping into binoviewers, you should understand your current telescope very well, where you know how to keep it well collimated.  This is particularly the case when binoviewing with a newtonian reflector/dob, where the telescope's collimation can tend to shift and need more frequent adjustment.  

 

The best binoviewing experience will benefit from:

 

Good basic telescope collimation

Focuser is squared with the tube and secondary

Focuser drawtube does not sag or tilt under heavy weight

Binoviewer is well centered when attached to focuser

Binoviewer is well collimated (this is not something most people can do and quality of binoviewer can impact how precisely collimated it is)

Binoviewer diopters (eyepiece holders) allow for eyepieces to be attached as close to centered as possible

 

Why all of these considerations for collimation and keeping everything tight and centered?   This is because the light cone has to travel through the whole optical system, be split evenly, and remain straight, so that both eyes receive a similar amount of light and a similar, on-axis image.  The above factors are all things that can throw off the image. The earlier in your optical system the light cone is thrown out of wack, such as if your telescope's collimation is off, then the negative visual effects are multiplied and exacerbated as the light travels through the components of the system.  This usually manifests as one eye getting more light than the other, making it more difficult for your brain/visual cortex to merge the images.  Now, there is some leeway where being slightly off will not present a visually appreciable change, but in general, binoviewing has much steeper technical requirements compared to monoviewing.

 

With monoviewing, it's not very critical that my eyepiece is nicely centered.  With binoviewing, you've really got to be on top of the collimation game and be mindful of keeping stuff centered to enjoy the improved comfort of using two eyes.   Some people are more sensitive collimation issues and have trouble merging the two images...others are not.   

 

On top of collimation, in newtonians/dobs, you will almost certainly need to use some type of optical corrector or barlow/telecentric barlow in order to reach focus.  Without some kind of corrector, you will not be able to reach focus, or the light cone will be too big and get cut off, resulting in aperture loss and light loss.

 

I find that with binoviewing, it is easier for my mind to take in all of the details of an object at once.  Ridiculously more comfortable viewing experience.  I liken it to speed reading-- it's easy to speed read when using both eyes at once-- much more difficult when only using one eye.  Binoviewing can be heavy on the pocketbook and is technically challenging.  If you are not comfortable monoviewing, jumping into binoviewing too quickly might be too stressful.



#11 Spikey131

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Posted 17 December 2019 - 09:59 PM

Should i get a pair?  Do they lower the clarity? anything bad about them?  i am tired of straining my one eye, putting my hand on the other, then switching and it just makes astronomy stressful.  I don't wanna look like a pirate either so i don't want to wear an eye-patch. I have a 12" Dobsonian, do binoviewers work well with dobsonians?

 

Also what is a good quality brand that doesn't cost more than $200?

 

I like the Celestron pair but my telescope is a Meade, maybe they wont work together?

 

Thank you!

First, what telescope do you have?

Second, what do you want to observe?

 

Binoviewers work great in SCTs on Alt/Az mounts.  They work great on bright objects like the sun, moon and planets.  You can buy the William Optics kit with 2 EPs for less than $300 and it will give stunning views of the solar system in a SCT.

 

With other telescopes, things can get more complicated and expensive.

 

Many refractors and Newtonian reflectors will need a Barlow lens to reach focus.  Still OK if you are viewing the solar system, but you lose the wide field views that refractors are good for.  
 

You can use binoviewers for DSOs, they won’t be as bright as mono vision.  You can use them with a GEM or a DOB, but it can be awkward.

 

I love my binoviewers in my C8 or refractors on a tracking AZ mount when viewing the moon and planets.  I sometimes use them for double stars and bright DSOs, but I am less enthusiastic about it.  I haven’t bothered trying them in my DOB.  Seems like more trouble than it is worth.


Edited by Spikey131, 17 December 2019 - 10:01 PM.


#12 Bob4BVM

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Posted 20 December 2019 - 03:53 PM

OP,

Is there any possible way you can try someone else's BVer setup ???

Is there a astro-club anywhere near you ? Star party ? Public viewing nights ?

 

BVing is not for everyone as some folks L/R eye-brain just seems to be wired differently than others.  Give it a try on other's gear if at all possible, you will know after a few minutes if it works for you. From my own outreach experience, it seems that it does work for around 80+% of people who try it.

 

All that said, if you find it works for you, one look at Saturn or a 1st-quarter Moon will change your viewing life forever.

I say that from many years of progression thru the 2-eyed viewing experience, starting with binoculars, BT's, BVers. After all that, how convinced am I of 2-eyed view advantages ?  Enough to go thru the immense trouble of building a large Binocular Telescope....

 

The step up in viewing comfort & detail perception borders on ridiculous. I have literally spent hours studying a single bright object like planets, Moon, M13, M42 etc.   M42 alone to me is worth the price of admission to BVing. Countless times I have gone out on a crisp winter night "for a quick look" and have sat there spellbound by the intricate detail & colors, finally coming in from the cold before I realize I had just spent over two hours on that single object ! smile.gif  That is something I could never do in cyclops mode, my eyes would be watering & exhausted after 10 minutes of one-eyed squinting for detail. In short, the experience goes from a self-imposed handicapped squint to a completely natural relaxed vision you don't even have to think about, just like you use your eyes in the daytime.

 

Good luck in your quest 

Bob


Edited by Bob4BVM, 20 December 2019 - 03:59 PM.

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#13 Zwick

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Posted 06 January 2020 - 11:33 PM

OP,

Is there any possible way you can try someone else's BVer setup ???

Is there a astro-club anywhere near you ? Star party ? Public viewing nights ?

 

BVing is not for everyone as some folks L/R eye-brain just seems to be wired differently than others.  Give it a try on other's gear if at all possible, you will know after a few minutes if it works for you. From my own outreach experience, it seems that it does work for around 80+% of people who try it.

 

All that said, if you find it works for you, one look at Saturn or a 1st-quarter Moon will change your viewing life forever.

I say that from many years of progression thru the 2-eyed viewing experience, starting with binoculars, BT's, BVers. After all that, how convinced am I of 2-eyed view advantages ?  Enough to go thru the immense trouble of building a large Binocular Telescope....

 

The step up in viewing comfort & detail perception borders on ridiculous. I have literally spent hours studying a single bright object like planets, Moon, M13, M42 etc.   M42 alone to me is worth the price of admission to BVing. Countless times I have gone out on a crisp winter night "for a quick look" and have sat there spellbound by the intricate detail & colors, finally coming in from the cold before I realize I had just spent over two hours on that single object ! smile.gif  That is something I could never do in cyclops mode, my eyes would be watering & exhausted after 10 minutes of one-eyed squinting for detail. In short, the experience goes from a self-imposed handicapped squint to a completely natural relaxed vision you don't even have to think about, just like you use your eyes in the daytime.

 

Good luck in your quest 

Bob

I would be interested in hearing more about your experience with using Binoviewers on outreach? I love the view, but would be concerned about the delays and complexity of adjustments between visitors. I'd love to be able to add the Bino "wow factor" but fear I would be adding a lot of frustation as well. Definitely interested in your thoughts/experiences?


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#14 sarco789

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Posted 08 January 2020 - 09:56 PM

What about a pair of clickstop zooms for binoviewing?

#15 Eddgie

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Posted 09 January 2020 - 08:54 AM

I would be interested in hearing more about your experience with using Binoviewers on outreach? I love the view, but would be concerned about the delays and complexity of adjustments between visitors. I'd love to be able to add the Bino "wow factor" but fear I would be adding a lot of frustation as well. Definitely interested in your thoughts/experiences?

Bad idea.   For small groups that will be observing with you, it is OK, but for outreach it is just not a very good idea.  Too much trouble with IPD and dipoter focus.  In particular, the IPD, which has to be pretty close unless you are using very big exit pupils, is not something you want people having to mess with.  

 

Also, the BV dims the image, and while an experienced amateur will find it minimal, we are used to dealing with faint fuzzies and the dimmer you make the image at outreach, in general, the harder it will be for people to see the subject. 

 

I mean hey, it is your BV, so give it a whirl, but I would say you should restrain your expectations.  Even in small groups, I don't use BVs. Better to pick big, showy subjects and use an eyepiece like a 31mm Nagler with its long eye relief and big exit pupil.  Well, that is my own recommendation though, but of course this is CN and there will be 20 other opinions that are equally as valid. 



#16 Eddgie

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Posted 09 January 2020 - 09:00 AM

What about a pair of clickstop zooms for binoviewing?

Now I don't use the Clickstops anymore (weight and the problem with the rotating top) but they work great.

 

That being said, by the time you put together a set of zooms and a binoviewer, it might be better just take the money you would spend on all of that stuff and buy a system with a power switch.

 

The limit of the zooms is the narrow apparent field at low power.  A pair of D21s in Denk bino with power switch was much better than using zooms, but even with the power switch system, I often used my zooms for planetary work.

 

I still use zooms for all planetary work, but not the Baaders (for the reasons mentioned above). Now I use either a pair of very light Nikons or some inexpensive zooms for solar work.  The zooms (along with the weight of the binoviewer, power switch and GPC) were kind of torture on my focusers. 

 

The click steps though are great for matching magnification. 

 

I love zooms though, and use them almost exclusively when I use binoviewers, which is not much, but for 100% of solar system work I use them.

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#17 Eddgie

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Posted 09 January 2020 - 09:05 AM

And above the Nikons are shown, but for H-a solar viewing, I have since moved to a cheap pair of Agena zooms. These seem as sharp as the Nikons to me, but the Nikons have a rotating top, and for H-a, I like to use winged eye guards (in fact, I used winged eye guards on the D21s in the Denks and I highly recommend them). 

 

The inexpensive Agena eyepieces have tops that do not rotate when they are zoomed making them my top choice for solar work.

 

thumbnail_20191002_111615.jpg

 

I highly recommend winged eye guards when binoviewing. They do a great job of cutting out ambient light. 

 

(The notes on this picture are there because I was using it to explain how to set up a Lunt binoviewer with zooms and a Baader GPC. It is just the only picture I had at hand that shows the winged eye guards.) 


Edited by Eddgie, 09 January 2020 - 09:07 AM.


#18 Shorty Barlow

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Posted 09 January 2020 - 10:09 AM

Nearly five years ago I decided to purchase the William Optics binoviewers. They came bundled with two 20mm, 66º eyepieces and a 1.6x nosepiece Barlow. I also acquired the 2x WO Barlow and slightly later a 2.6x TS Optics Barlow. I'm pretty sure the WO bino's are manufactured by Kunming United Optical as are most of the BV's with the smaller prisms.

 

sml_gallery_249298_10580_1123872.jpg

 

From the outset I intended these to be used in Maksutov and SCT scopes although I have experimented (unsuccessfully) with refractors.

 

sml_gallery_249298_10580_406129.jpg

 

If you have no focusing problems the main difficulty with bino's is actually merging the individual images.

 

sml_gallery_249298_10580_100179.jpg

 

Unlike with binoculars, this is essentially a learned skill, and there are many factors to achieving a good consistent ability to merge both images.

 

sml_gallery_249298_10580_153436.jpg

 

 

In my experience the individual eyepieces have to be of sufficient focal length and have well-sized eye lenses and adequate eye relief.

 

sml_gallery_249298_10580_303925.jpg



#19 Zwick

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Posted 09 January 2020 - 11:54 AM

Bad idea.   For small groups that will be observing with you, it is OK, but for outreach it is just not a very good idea.  Too much trouble with IPD and dipoter focus.  In particular, the IPD, which has to be pretty close unless you are using very big exit pupils, is not something you want people having to mess with.  

 

Also, the BV dims the image, and while an experienced amateur will find it minimal, we are used to dealing with faint fuzzies and the dimmer you make the image at outreach, in general, the harder it will be for people to see the subject. 

 

I mean hey, it is your BV, so give it a whirl, but I would say you should restrain your expectations.  Even in small groups, I don't use BVs. Better to pick big, showy subjects and use an eyepiece like a 31mm Nagler with its long eye relief and big exit pupil.  Well, that is my own recommendation though, but of course this is CN and there will be 20 other opinions that are equally as valid. 

Those were precisely my misgivings. But Bob mentioned using his on outreach, so I was curious about his experiences in this area. I don't have binoviewers yet, but will be getting a set. I'll be using them on a 12", so hopefully I'll have a lot of photons to start out with. I may try it a bit with family or very small groups, but have no expectation of using them on regular outreach events.



#20 Eddgie

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Posted 09 January 2020 - 01:39 PM

Those were precisely my misgivings. But Bob mentioned using his on outreach, so I was curious about his experiences in this area. I don't have binoviewers yet, but will be getting a set. I'll be using them on a 12", so hopefully I'll have a lot of photons to start out with. I may try it a bit with family or very small groups, but have no expectation of using them on regular outreach events.

With small groups it is more feasible, but even in this case, only (in my opinion) if the scope is driven.  If it is a traditional dob, you will have to constantly be re-finding the target as the other viewers knock it all over the place trying to get the IPD and the diopter settings correct.  Even with a Go2 mount, I have seen a huge number of instances where people could not get comfortable and wound up canting their head, closing one eye, and just viewing with the other eye. I would say that this was a 50% outcome. 

 

If you can work at native focal length where the exit pupil can be larger, making it easy to acquire the field, then that too will help, but if using Barlow with small exit pupil it can be very frustrating for your guests.  They just want to look in and be thrilled.  

Again, there is no harm at all in trying it, and try it you should. You may have better luck with it, but I found it to be frustrating for both me, and very often for my guests.  Everyone loves to see the Double Cluster or Pliedes in a 31mm Nagler.  I go with the sure fire stuff. 

P

(These days, I do outreach with image intensifiers and it is the best outreach I have ever done!  Peter and I get long lines and people often loop through the lines and wind up staying half an hour!) 

 

Anyway, that is my experience with outreach. The bigger, brighter, and bolder the target is, and the longer the eye relief and lower the power you can use to show the subject well the more the guest enjoy it.  Using the image intensifier, the line is longest for the 1x views. Peter can have is 16" dob set up and there will be almost no line, but where we are handing out image intensfiers, there are two lines with people almost always waiting. 



#21 Zwick

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Posted 09 January 2020 - 02:11 PM

With small groups it is more feasible, but even in this case, only (in my opinion) if the scope is driven.  If it is a traditional dob, you will have to constantly be re-finding the target as the other viewers knock it all over the place trying to get the IPD and the diopter settings correct.  Even with a Go2 mount, I have seen a huge number of instances where people could not get comfortable and wound up canting their head, closing one eye, and just viewing with the other eye. I would say that this was a 50% outcome. 

 

If you can work at native focal length where the exit pupil can be larger, making it easy to acquire the field, then that too will help, but if using Barlow with small exit pupil it can be very frustrating for your guests.  They just want to look in and be thrilled.  

Again, there is no harm at all in trying it, and try it you should. You may have better luck with it, but I found it to be frustrating for both me, and very often for my guests.  Everyone loves to see the Double Cluster or Pliedes in a 31mm Nagler.  I go with the sure fire stuff. 

P

(These days, I do outreach with image intensifiers and it is the best outreach I have ever done!  Peter and I get long lines and people often loop through the lines and wind up staying half an hour!) 

 

Anyway, that is my experience with outreach. The bigger, brighter, and bolder the target is, and the longer the eye relief and lower the power you can use to show the subject well the more the guest enjoy it.  Using the image intensifier, the line is longest for the 1x views. Peter can have is 16" dob set up and there will be almost no line, but where we are handing out image intensfiers, there are two lines with people almost always waiting. 

My scope is a SkyWatcher collapsible. It has detents on the collapsible truss design to shorten the OTA for binos. I borrowed a set from a friend and was able to try it out briefly. That experience prompted my ordering of a set for myself. With the shortened OTA, no barlow nosepiece is needed to achieve focus, thus lower magnifications should be practical. As for the scope being driven, I am building an EQ platform for that scope as well, but that project had to be put on hold for other priorities. Maybe the binoviewer arrival will bump that up a bit.

 

I'd be interested in your thoughts on the collapsible truss setup for binoviewer implementation.

 

Thanks for the pointers and clear skies to you!



#22 Eddgie

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Posted 09 January 2020 - 10:38 PM

I do not have the geometry of the scope in question but from what info I have, it is likely that the scope will not work at full aperture when it is lowered enough to reach focus with BVs, but it could be close.

 

That may not prevent you from getting good views though.

 

If you want to do planets though, it would be best to raise the cage and use a Barlow.

 

Someone and I discussed this same scope, but I don't think we ever worked up the final figures.   As I recall, he said that the scope had about a 25% secondary and that an extension was needed to reach focus.  I believe that at f/5 you would need about a 33% or larger secondary to get the secondary close enough to the primary for a binoviwer to reach focus and not lose the axial rays.   The other person party to the conversation was going to try to do a ray trace and see how the system would work in the lowered position. 

 

Again that in itself may not be much of an issue for general use, but for planetary, you would want to use the scope all the way up and use a Barlow to reach focus.


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#23 Zwick

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Posted 10 January 2020 - 12:02 PM

Thanks! Of course, I am a newb and still lack a decent understanding of the optics issues. The manufacturer specs say the secondary is 23%. If I need 33%, does that just mean I am effectively losing aperture, or are there other implications as well?



#24 Eddgie

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Posted 10 January 2020 - 01:53 PM

Thanks! Of course, I am a newb and still lack a decent understanding of the optics issues. The manufacturer specs say the secondary is 23%. If I need 33%, does that just mean I am effectively losing aperture, or are there other implications as well?

Well, if you use the lower position and the scope no longer produces full aperture (cannot catch all of the off axis rays converging on the center of the field) then the two questions are how much aperture is lost and what is the effect on the size of the secondary mirror.

See, if the secondary mirror is no longer catching all of the axial rays and the aperture is reduced, the secondary mirror now becomes a larger with respect to the remaining aperture.  If the aperture were reduced to 9" (and to be 100% clear, I do not even know if the aperture would be reduced, but my guess is that it would be, but probably not this much) since the secondary size does not change, it is now a bigger percentage of the remaining aperture.

And this is why I said it would be best to use a Barlow when doing planets.   This will ensure that the system is working at full aperture with the minimum size secondary (as a percentage of aperture).   

 

Here is the simple math.. Lets suppose the scope has a 10mm fully illuminated image circle and 75mm of back focus (And I don't know what it has, but you can measure it and find out).  

 

For every multiple of the focal length that you move the secondary closer to the primary, the fully illuminated circle will be reduced in size by 1mm.

 

Now suppose your binoviewer has 96mm of light path and you could reach focus by lowering the secondary mirror by 21mm.  At f/5, then means that the fully illuminated circle would be reduced by a bit over 4mm, but at the center of the field, the system would still be working at full aperture. 

 

Now suppose the scope has a detent that is 50mm lower than the full extension. If you lowered it all the way to this position, then that would be 10mm, and that would be the lowest you could go and only the very exact center of the field would be fully illuminated.  Past this point, and the scope would be loosing aperture an the more you went, the more aperture would be lost. 

 

I think these have a dent, and as this suggests it might be better to only lower the secondary cage exactly as much as needed.  It might be good to cut a piece of PVC pipe and spit it in half lenghtwise to set the poles all at the same height if there if you can reach focus without going all the way to the detent. 

 

Again, for deep sky, it probably would be very difficult to see how much light loss you would get from half an inch of aperture loss, but for planets, best result will be at full aperture, and if you are manually tracking, the bigger the full aperture field (which is essentially what your fully illuminated circle is) the better. 

 

For general use though, it is probably not really a big deal.  If you like the views, that is all that matters. 


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#25 REC

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Posted 10 January 2020 - 01:53 PM

Now I don't use the Clickstops anymore (weight and the problem with the rotating top) but they work great.

 

That being said, by the time you put together a set of zooms and a binoviewer, it might be better just take the money you would spend on all of that stuff and buy a system with a power switch.

 

The limit of the zooms is the narrow apparent field at low power.  A pair of D21s in Denk bino with power switch was much better than using zooms, but even with the power switch system, I often used my zooms for planetary work.

 

I still use zooms for all planetary work, but not the Baaders (for the reasons mentioned above). Now I use either a pair of very light Nikons or some inexpensive zooms for solar work.  The zooms (along with the weight of the binoviewer, power switch and GPC) were kind of torture on my focusers. 

 

The click steps though are great for matching magnification. 

 

I love zooms though, and use them almost exclusively when I use binoviewers, which is not much, but for 100% of solar system work I use them.

Hey Ed, as a side note, how good are those cheap Nikon zooms? Same as the Celestron ect, but not in the class of the more expensive Baader zooms?

Thanks, Bob




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