Largest DOBs in Europe

[jetstream]

1 minute ago, Ships and Stars said:

I make it sound so easy....

You just might Robert!!

You don't know until you try. Good idea about sourcing the mirrors and also the structures, possibly on the latter.

[Ships and Stars]

PS Mel Bartels claims the contrast boost with binoscopes is markedly larger than the gain in perceived aperture. Combine those two factos (aperture+contrast), and it starts to sounds really, really appealing. I've been comparing one-eyed views through my binoculars against using both eyes, and the difference of course is massive. I can only imagine what 20" stereo views would look like... even with the mass-produced SW mirrors.

[jetstream]

2 minutes ago, Ships and Stars said:

PS Mel Bartels claims the contrast boost with binoscopes is markedly larger than the gain in perceived aperture. Combine those two factos (aperture+contrast), and it starts to sounds really, really appealing. I've been comparing one-eyed views through my binoculars against using both eyes, and the difference of course is massive. I can only imagine what 20" stereo views would look like... even with the mass-produced SW mirrors.

For sure!

Read Arie Otte's PDF I link a bit back....

and this too"http://arieotte-binoscopes.nl/Why a Binoscope.htm

 

Edited October 18, 2020 by jetstream

[Ships and Stars]

Just now, jetstream said:

For sure!

Read Arie Otte's PDF I link a bit back....

Will do - thanks Gerry! 

[jetstream]

3 minutes ago, Ships and Stars said:

I've been comparing one-eyed views through my binoculars against using both eyes, and the difference of course is massive. I can only imagine what 20" stereo views would look like... even with the mass-produced SW mirrors.

Just remember Robert, that we will all respond differently to the binoscope- some might see more than calculated, some less and some might see different objects differently, gain wise.

The math is hard and fast, the brain is not.

Your response to binoculars is a very good sign.

[jetstream]

@Ships and Stars

Important, from link

" If there is any advantage above the mentioned binocular summation factor of 1.4, this is attributed to this mechanism, which is called binocular facilitation or neural summation"

Its possible to get more than 1.4x IMHO...

[jetstream]

37 minutes ago, Ships and Stars said:

PS I wonder why Mel says the secondary mirrors have to be larger?

I'm not sure but I think that between the needed"L"  dimension , the speed of the scope and possibly the illumination he wants dictates the larger size. I'll run it through his calc.

[Ships and Stars]

9 minutes ago, jetstream said:

@Ships and Stars

Important, from link

" If there is any advantage above the mentioned binocular summation factor of 1.4, this is attributed to this mechanism, which is called binocular facilitation or neural summation"

Its possible to get more than 1.4x IMHO...

It certainly feels like more than 1.4x to me and the contrast factor definitely shoots up. I think my years of squinting through a camera viewfinder with my right eye has inflicted a bit of permanent loss of sensitivity to a small degree. Using both eyes just seems to boost everything across the board to me while reducing eye strain immensely. I can observe with a high degree of concentration much longer with two eyes than one. I know some don't get on with binocular vision, but it seems to suit me well.

[Peter Drew]

I've built more than 20 binoscopes over the years, both reflecting and refracting so have no qualms about building any size, the main limitation is cost!.  I do have a spare 18" F3.6 mirror, it's tempting to get another made.  I have not found it necessary to use coma correctors on my 12" reflecting binoscope despite the off axis images being compromised.  When you use a binoscope you generally concentrate on the central image and the periphery is just a perception, the eye has a very small field of definition and resolution.  Try looking at a page of text without moving your eyes and you will find that it is difficult to read more than an extra word either side of it, the same goes for stars in a binoscope.    🙂

[Peter Drew]

I've built more than 20 binoscopes over the years, both reflecting and refracting so have no qualms about building any size, the main limitation is cost!.  I do have a spare 18" F3.6 mirror, it's tempting to get another made.  I have not found it necessary to use coma correctors on my 12" reflecting binoscope despite the off axis images being compromised.  When you use a binoscope you generally concentrate on the central image and the periphery is just a perception, the eye has a very small field of definition and resolution.  Try looking at a page of text without moving your eyes and you will find that it is difficult to read more than an extra word either side of it, the same goes for stars in a binoscope.    🙂

[Peter Drew]

I've built more than 20 binoscopes over the years, both reflecting and refracting so have no qualms about building any size, the main limitation is cost!.  I do have a spare 18" F3.6 mirror, it's tempting to get another made.  I have not found it necessary to use coma correctors on my 12" reflecting binoscope despite the off axis images being compromised.  When you use a binoscope you generally concentrate on the central image and the periphery is just a perception, the eye has a very small field of definition and resolution.  Try looking at a page of text without moving your eyes and you will find that it is difficult to read more than an extra word either side of it, the same goes for stars in a binoscope.    🙂

[Peter Drew]

I've built more than 20 binoscopes over the years, both reflecting and refracting so have no qualms about building any size, the main limitation is cost!.  I do have a spare 18" F3.6 mirror, it's tempting to get another made.  I have not found it necessary to use coma correctors on my 12" reflecting binoscope despite the off axis images being compromised.  When you use a binoscope you generally concentrate on the central image and the periphery is just a perception, the eye has a very small field of definition and resolution.  Try looking at a page of text without moving your eyes and you will find that it is difficult to read more than an extra word either side of it, the same goes for stars in a binoscope.    🙂

[Peter Drew]

Apologies for multiple posts, don't know what went wrong there?    🙂

[Ships and Stars]

9 minutes ago, Peter Drew said:

I've built more than 20 binoscopes over the years, both reflecting and refracting so have no qualms about building any size, the main limitation is cost!.  I do have a spare 18" F3.6 mirror, it's tempting to get another made.  I have not found it necessary to use coma correctors on my 12" reflecting binoscope despite the off axis images being compromised.  When you use a binoscope you generally concentrate on the central image and the periphery is just a perception, the eye has a very small field of definition and resolution.  Try looking at a page of text without moving your eyes and you will find that it is difficult to read more than an extra word either side of it, the same goes for stars in a binoscope.    🙂

Oh wow, that's some knowledge gained! I may have some questions for you one of these days Peter. I think my starting point would be to double up my 300p when one appears for a good price. I'd need to do more research first, the OTAs might be the cheap part!

[Louis D]

Just now, Peter Drew said:

Apologies for multiple posts, don't know what went wrong there?    🙂

You can ask a moderator to delete the extra posts.

I've had it happen when my internet connection was flaky, and I hit return multiple times before it actually posted thinking the first time didn't work.  They all got queued up until my connection returned.

[Ships and Stars]

3 minutes ago, Peter Drew said:

Apologies for multiple posts, don't know what went wrong there?    🙂

Must be all this talk of binocular vision

[PeterW]

Look at the sky through some mounted binoculars and then close one eye... shows fainter stars more easily and low contrast easier. This chap was indigogoing a 6” https://analogsky.co/swift/ (the 8” he was asking a fair bit for). Covid happened and he didn’t reach his target. Would be a shame if it never became available as there is no one else making any and he had some clever designs, though not in the size range some are contemplating here... 

Peter

[Captain Scarlet]

3 hours ago, Louis D said:

You can ask a moderator to delete the extra posts.

I've had it happen when my internet connection was flaky, and I hit return multiple times before it actually posted thinking the first time didn't work.  They all got queued up until my connection returned.

Better on here than on Amazon I guess!

[estwing]

5 hours ago, Ships and Stars said:

I've been thinking about binoscopes since this summer as an alternative to a ridiculously large dobsonian,

And two 500p scopes together isn't large at all..!!!!😁

[Ships and Stars]

23 minutes ago, estwing said:

And two 500p scopes together isn't large at all..!!!!😁

Well, relatively speaking, compared to a 30" f5 behemoth with a 2" think mirror... 😁 

[Barry-W-Fenner]

This question is would probably be better asked in a new topic, however in short, could someone advise what advantages there would be to using a binoviewer in my 300p if any? I assume you would just need to purchase a set of binos and a 2nd matching eye piece and your away?!

[PeterW]

The binoviewer chops the light in half and so you lose exit pupil brightness, I’ll let others comment on the benefits

Peter

[Peter Drew]

This is true, but I think the summation effect that tends to enhance the brightness of a binoscope above that of a single unit may also apply to the summation of the two exit pupils of a binoviewer such that the light loss appears to be less than half.  Also, some binoviewers split the light nearer to 60/40 which again gives an advantage over 50/50.  🙂