'Binoviewing' M57 and other DSOs

[Ships and Stars]

Hi all,

I've really wanted to try my WO binoviewers in the big dob for DSOs like nebulae and galaxies, which I've understand is kind of a non-starter, since it effectively halves aperture, though other gains can be had through stereo vision. I had a very short observing session last night - wind picked up too much for the dob and it was shaking like mad. But I did make a brief but interesting observation.

I finally decided to try the binoviewers on M57 last night (20mm standard WO ep with 1.6x GPC at 160x) vs my 17.5mm Morpheus (114x) on the 20" dob. Admittedly, it's a bright DSO, but I was pleased to find it looked amazing through the BVs. I 'think' I could even see a hint of the central star, and that was with the moon very close by, maybe 25-30deg to the south and at a higher altitude. I'll call it a maybe on the central star - will try again next go.

For comparison, I swapped out the BVs for a single 17.5mm Morpheus and could tell absolutely no difference in brightness - only that I gathered a fair bit more detail with the BVs.

Maybe I just saw what I wanted to in my mind, but I tried to be objective. The maths behind BVs splitting the light ray will presumably contest this assertion.  

In reality, I didn't get much time to play with this setup so the jury is still out. The next chance I have, I will try using binoviewers for a longer period to scan along the Veil and also M31, M32, M33 and M110 and any other DSO I can  in increasing faintness to see what the practical limits are. 

As an aside, I also found the BVs better for centring a star during alignment vs using a single ep, perhaps because there was no slight 'head roll' when placing both eyes to the EPs.

Anyone else player around with BVs on some of the brighter DSOs? I'm hoping to get some lower mag 1.25" EPs to try and gain more of a widefield and drop mag for fainter DSOs. 

I'd love to lose the 1.6x barlow but can't focus without. One idea I had was investigating if there was a 'negative' 2" adaptor which actually sits inside the drawtube, as the BV nosepiece will go in some distance. Not keen on cutting and truss rods! A SW flextube dob would be great to play with in this regard. 

Cheers all. 

 

 

Edited December 5, 2019 by Ships and Stars

[Space Hopper]

Hi,

Despite being accused by some on here of 'making sweeping statements' regarding the perceived benefits of two eyed viewing,

I too, have found my results to be the same as your own with regard to brightness with what i see through the eyepiece.

Admittedly i'm only using a 12" mirror compared to your 20". The dark sky views you have there must be fantastic ?

I always found the showpiece objects looked better for me personally, and have been rewarded with my best ever views of objects like M42, M27, M11, M13, M35

Getting by without the 1.6x multiplier is a tricky one. 

I used a Denkmeier / Earthwin system, to get the minimum amplification down to somewhere around 1.2x - 1.3x

I was getting 60x magnification at my lowest setting : pretty much as low as i could get. 

I'm glad to hear you're enjoying binoviewing with the 20" : the views must be amazing with it on a good night 😀

 

[Ships and Stars]

17 minutes ago, Space Hopper said:

Hi,

Despite being accused by some on here of 'making sweeping statements' regarding the perceived benefits of two eyed viewing,

I too, have found my results to be the same as your own with regard to brightness with what i see through the eyepiece.

Admittedly i'm only using a 12" mirror compared to your 20". The dark sky views you have there must be fantastic ?

I always found the showpiece objects looked better for me personally, and have been rewarded with my best ever views of objects like M42, M27, M11, M13, M35

Getting by without the 1.6x multiplier is a tricky one. 

I used a Denkmeier / Earthwin system, to get the minimum amplification down to somewhere around 1.2x - 1.3x

I was getting 60x magnification at my lowest setting : pretty much as low as i could get. 

I'm glad to hear you're enjoying binoviewing with the 20" : the views must be amazing with it on a good night 😀

 

That's great - now we're talking! I can only agree with you from what I've seen thus far. How again did you manage to drop down to 1.2-1.3x? I know the Denks are BVs but is the Earthwin a low power GPC? Would that thread onto my standard 1.25 nose piece I wonder, or is bespoke for Denk BVs? My target mag for faint DSOs in the 20" is around 85x which will be hard to achieve without losing the current mandatory 1.6x barlow effect. I'd be thrilled even to go down to 100x. I have a second-hand 27mm/53deg  Orion 'Edge On' that will be arriving soon, a low price 1.25" ep - curious to see how it fares. If I like it and can find another, I'll give that a go in the BVs.

12" is still a lot of aperture! I have to say the 20" can be truly awesome at times, I've only ever had a 200p and a 130PDS (now sold), so the 500p is in a different league altogether. Under 21.90+ skies in the Cairngorms it's probably the best visual astronomy I'll ever experience, unless I have a chance to view through someone else's bigger dob someday. 

If I can replicate the ball ends on the 6 truss rods, I'll make some shorter 'bino' truss rods, hate to modify the standard ones in case it throws something out of alignment. The ball ends (12 in total) might be something for a 3D printer enthusiast. I'll measure them, but I think they are simple 25mm ball ends.

I bet M27 looks amazing but M42 is probably mind-blowing through BVs! Next time I'm out I think I will just stick with binoviewers vs 17.5 Morpheus and revisit some of the targets I've seen recently to compare the experience. From what I saw viewing M57 with the bog standard 20mm WO eyepieces, I think I will have some exciting results.  

60x mag through yours is excellent, that must be wonderful! 

[Space Hopper]

The Denks / Earthwins initially use a 2" barlow type lens which amplifies 2 - 3x They call it an OCS (an optical corrector system) It just enables you to be able to focus with any Newtonian (or refractor)

The OCS in my Earthwin gives me 2.4x

Using a 'Powerswitch' adds a reducer lens into the view to give 2 lower power options ; in my case 1.2x and 1.9x so you then move it in to place and refocus. It gives you 3 different magnifications with just the one set of eyepieces.

I've spent many a session using it with only my 24mm Panoptics, getting 60x, 90x and 120x which is ideal for most objects.

    

Edited December 5, 2019 by Space Hopper

[Louis D]

I created a DIY unit power OCS/GPC by combining a Meade 140 2x barlow nosepiece at the front of 40mm of spacer tubes (IIRC) and a GSO (or generic?) 0.5x focal reducer at the back end and then screwing it into the nosepiece of my Arcturus binoviewer.  I'll have to double check sometime, but I think there is some vignetting with widest field eyepieces and obviously some field curvature/distortion issues.  However, it reaches focus in my Dob's limited backfocus focuser.  It's startling to see with two eyes how much sky is visible, even if it's not perfect, compared to the 2x barlow nosepiece by itself which yields about 3x in the BV.  That's nine times as much area on the sky visible at once!

[Ships and Stars]

3 hours ago, Space Hopper said:

The Denks / Earthwins initially use a 2" barlow type lens which amplifies 2 - 3x They call it an OCS (an optical corrector system) It just enables you to be able to focus with any Newtonian (or refractor)

The OCS in my Earthwin gives me 2.4x

Using a 'Powerswitch' adds a reducer lens into the view to give 2 lower power options ; in my case 1.2x and 1.9x so you then move it in to place and refocus. It gives you 3 different magnifications with just the one set of eyepieces.

I've spent many a session using it with only my 24mm Panoptics, getting 60x, 90x and 120x which is ideal for most objects.

    

Ooh that's a nice looking setup!  I appreciate the information. I looked at the Siebert website some time ago and emailed him, but never ordered a GPC. Getting the magnification down is a top priority. Thanks very much!

 

1 hour ago, Louis D said:

I created a DIY unit power OCS/GPC by combining a Meade 140 2x barlow nosepiece at the front of 40mm of spacer tubes (IIRC) and a GSO (or generic?) 0.5x focal reducer at the back end and then screwing it into the nosepiece of my Arcturus binoviewer.  I'll have to double check sometime, but I think there is some vignetting with widest field eyepieces and obviously some field curvature/distortion issues.  However, it reaches focus in my Dob's limited backfocus focuser.  It's startling to see with two eyes how much sky is visible, even if it's not perfect, compared to the 2x barlow nosepiece by itself which yields about 3x in the BV.  That's nine times as much area on the sky visible at once!

I like your thinking! This area is still a bit of a mystery to me, but have a rough idea of what you've done.

Thank you both! 

[JTEC]

I’ve found the brighter DSOs to be superb binoviewing targets.  I’m not sure it would be the best approach searching for seriously faint stuff, though perhaps the advantages of the two eyed approach - you do see more - might compensate to some extent for any light loss. For brighter objects, the light loss argument can, in my experience at least, be dismissed. I’m not saying there isn’t any - I’m saying it’s negligible in terms of observational impact. I’m not talking about big aperture either. My scopes are a TEC 140 and a C11.  The binoviewer is a Baader Mk V.  The binocular views of, say, M42 and M13 are dramatically more engaging than the mono views. 

For the Baader at least, I believe that a negative lens is required to lengthen the focal ratio and diminish the chromatic aberration due to the prisms. This, I think, is what Roland Christen said, and he designed the unit. I started with the GPCs but now use the 2x Powermate; there are other options from Baader and AstroPhysics.  There is no problem about using such a lens. There is no degradation of the image. In fact, because of the above, it is arguably improved. On top of this,  it allows you to use longer focal length eyepieces which, in most cases, are likely to be more comfortable.  

By the way, I suspect that the Morpheus you’re using is one you bought from me. 🤔 I hope it’s going well!

 

 

 

[Space Hopper]

You have a similar set up to me JTEC.

Your experiences mirror mine. I've never used a C11, but had a C8 edge for a while.

As long as you keep the lightpath short, SCTs binoview superbly.

I have a 2" Powermate, but must confess to never using it with my Mk V. I have 2 Baader prisms and keep a 2.6x gpc permanently in one of them for high power use.

[jetstream]

@Ships and Stars

From CN former mod EdZ, an important read

" Exit Pupil
A telescope with binoviewer produces what I would call a false exit pupil. The exit pupil is always larger than the amount of light that it delivers (as compared to exit pupil from scope without binoviewer). That is due to the fact the beam splitter delivers half the light to each exit pupil. This mathematics is all discussed above.

Think about it. A 6" scope with binoviewer at 30x has a 5mm exit pupil. But the light delivered to that exit pupil in each side of the binoviewer is (150x150)/2 = 11250, then sqrt11250 = 106mm. The true exit pupil would be 106/30 = 3.5mm, or an exit pupil with one half the area of the false exit pupil.

The light delivered to the exit pupil in a binoviewer is not as bright as the light in an equal sized exit pupil from either a scope or binocular. Hence, it can be described as a false exit pupil."

https://www.cloudynights.com/topic/61467-binocular-vision-summation/
 

Edited December 5, 2019 by jetstream

[jetstream]

One on my very best views of the Needle galaxy,NGC4565 was with the15", Binotron 27's/32mm TV plossls/powerswitch at 1.3x. Another stunning view is the Leo Triplet, along with M42, M57 etc...

A 20" fast f4 scope should be super on these objects with the right eyepieces.

[Harmony Smurf]

I haven't tried it with a large scope(mine is a 6" f/5 reflector), but love low power binoviewing of bright DSOs.  I use a 2x OCA with my 25mm HD Orthos producing 61x.  BTW, you lose brightness but not resolving power with a binoviewer.

[Ships and Stars]

Hi all, apologies for not replying earlier - things have been flat out! 

On 05/12/2019 at 21:22, JTEC said:

I’ve found the brighter DSOs to be superb binoviewing targets.  I’m not sure it would be the best approach searching for seriously faint stuff, though perhaps the advantages of the two eyed approach - you do see more - might compensate to some extent for any light loss. For brighter objects, the light loss argument can, in my experience at least, be dismissed. I’m not saying there isn’t any - I’m saying it’s negligible in terms of observational impact. I’m not talking about big aperture either. My scopes are a TEC 140 and a C11.  The binoviewer is a Baader Mk V.  The binocular views of, say, M42 and M13 are dramatically more engaging than the mono views. 

For the Baader at least, I believe that a negative lens is required to lengthen the focal ratio and diminish the chromatic aberration due to the prisms. This, I think, is what Roland Christen said, and he designed the unit. I started with the GPCs but now use the 2x Powermate; there are other options from Baader and AstroPhysics.  There is no problem about using such a lens. There is no degradation of the image. In fact, because of the above, it is arguably improved. On top of this,  it allows you to use longer focal length eyepieces which, in most cases, are likely to be more comfortable.  

By the way, I suspect that the Morpheus you’re using is one you bought from me. 🤔 I hope it’s going well!

 

 

 

Thanks! It is your Morpheus that I've been using, a great eyepiece. I'm going to try out a range of DSOs  with BVs and use the Morpheus and the 21E as benchmarks. I'll look into some different arrangements to drop magnification as well. Cheers!

On 05/12/2019 at 23:14, jetstream said:

@Ships and Stars

From CN former mod EdZ, an important read

" Exit Pupil
A telescope with binoviewer produces what I would call a false exit pupil. The exit pupil is always larger than the amount of light that it delivers (as compared to exit pupil from scope without binoviewer). That is due to the fact the beam splitter delivers half the light to each exit pupil. This mathematics is all discussed above.

Think about it. A 6" scope with binoviewer at 30x has a 5mm exit pupil. But the light delivered to that exit pupil in each side of the binoviewer is (150x150)/2 = 11250, then sqrt11250 = 106mm. The true exit pupil would be 106/30 = 3.5mm, or an exit pupil with one half the area of the false exit pupil.

The light delivered to the exit pupil in a binoviewer is not as bright as the light in an equal sized exit pupil from either a scope or binocular. Hence, it can be described as a false exit pupil."

https://www.cloudynights.com/topic/61467-binocular-vision-summation/
 

 

On 05/12/2019 at 23:20, jetstream said:

One on my very best views of the Needle galaxy,NGC4565 was with the15", Binotron 27's/32mm TV plossls/powerswitch at 1.3x. Another stunning view is the Leo Triplet, along with M42, M57 etc...

A 20" fast f4 scope should be super on these objects with the right eyepieces.

Good point Gerry on the exit pupil through binoviewers - I didn't realise that about splitting the exit pupil, but it makes perfect sense.

It will be a few weeks before I can invest in some new EPs, but looking for an affordable combination - a slew of different ideas ranging from 30 or 40mm Vixen NPLs (the 40mm NPL only has a 40deg FOV, but mag would drop to 80x with a 1.6x gpc so as good as it gets for moderately faint nebula) to 27mm Orion/ BST/ Omegon etc extra flat eps. Also the trusty TV plossls or maybe a pair of 35mm Baaser eudiascopic(s) if I can find some second hand ones, although I hear they need considerably more inward travel to focus because of the shoulder design which would probably set me back to a 2x GPC. John has mentioned some focusers have a split tube to shorten drawtube length, perhaps an idea. 

I'd go for the Binotrons and a powerswitch but will have to wait until I've sold a few more toys!

Lots to think about! 

Thanks everyone, I'll no doubt report back once I've tackled a few more DSOs with the 500p. 

[Ships and Stars]

10 hours ago, Harmony Smurf said:

I haven't tried it with a large scope(mine is a 6" f/5 reflector), but love low power binoviewing of bright DSOs.  I use a 2x OCA with my 25mm HD Orthos producing 61x.  BTW, you lose brightness but not resolving power with a binoviewer.

I can only dream about 61x! My target for the fainter DSOs is around 85x for best results I believe, but that is single EP viewing. Probably a bit lower mag for binoviewers. I wished I'd started experimenting with them before, but only recently realised I had a low profile 2" to 1.25" adaptor lurking in the back of my EP case, doh! 

[jetstream]

31 minutes ago, Ships and Stars said:

Good point Gerry on the exit pupil through binoviewers - I didn't realise that about splitting the exit pupil, but it makes perfect sense.

At f4.8 the I wanted to go lower mag than the 32mm's give. At f4.1- not tried yet- I think the 32mm range will be VG. As we know we have to deal with secondary shadow on brighter objects if the mag gets down there.

You might want to consider this for your upcoming purchase....

No need for fancy, expensive eyepieces with the binoviewer IMHO, GSO plossls are VG for example. I like plossls vs orthos for this application because the plossls eye relief is tighter and not as prone to float, eventhough the 32mm TV's do float without the eyguard extender.

[Ships and Stars]

2 hours ago, jetstream said:

At f4.8 the I wanted to go lower mag than the 32mm's give. At f4.1- not tried yet- I think the 32mm range will be VG. As we know we have to deal with secondary shadow on brighter objects if the mag gets down there.

You might want to consider this for your upcoming purchase....

No need for fancy, expensive eyepieces with the binoviewer IMHO, GSO plossls are VG for example. I like plossls vs orthos for this application because the plossls eye relief is tighter and not as prone to float, eventhough the 32mm TV's do float without the eyguard extender.

 

Indeed - I was just looking at the GSOs for £32.80 each, that's pocket change in this game. The Baader 35s eudiascopics sound great, but they are £155 a pop, virtually second-hand 24mm Panoptic territory (now £254 new).

Now I'm reading about clear aperture (my WO binoviewer has only 20mm clear aperture), light cone restrictions in fast dobs, Siebert's website (ouch!) and the 'zero path' TS or Omegon BVs etc and it's making my head spin again. No cheap way out to get maximum performance, as with most things.

To complicate matters even more, I am now looking at a low profile Crayford focuser to move the binoviewer in as close as possible to try and get away with a 1.2x or 1.3x gpc. 

I think for now I will live with the 1.6x and some 32mm EPs and see how life goes! I'll probably be happy with this set up. At least for a week or two! 🤣

 

[jetstream]

3 hours ago, Ships and Stars said:

I am now looking at a low profile Crayford focuser

I would hold off... everything is working well for you, I would just stick some 30-32mm eyepieces in the binoviewers and observe.  So far I havn't got things to work well with filters in this type of set up.

Big controversy with bino prism clear apertures including mine... mine are 27mm clear at the "zero" 2.3x but the reducer or whatever is in there reduces it a bit.

My humble advice? don't worry about clear aperture. "run whatcha brung"!

btw 25mm plossls work well too.

[Ships and Stars]

5 hours ago, jetstream said:

I would hold off... everything is working well for you, I would just stick some 30-32mm eyepieces in the binoviewers and observe.  So far I havn't got things to work well with filters in this type of set up.

Big controversy with bino prism clear apertures including mine... mine are 27mm clear at the "zero" 2.3x but the reducer or whatever is in there reduces it a bit.

My humble advice? don't worry about clear aperture. "run whatcha brung"!

btw 25mm plossls work well too.

Excellent advice. If anything, I can simply use what I have as a benchmark or reference for any future tweaks I make. Just getting time to view is my main problem!

[jetstream]

2 minutes ago, Ships and Stars said:

Just getting time to view is my main problem

Yes, time can be an issue, here its the year of clouds/snow and rain. I was 90 miles north yesterday, clear as a bell into evening and drove into a wall of cloud not too far from this place. I guess thats why they call it Rainy Lake lol!

[Ships and Stars]

5 hours ago, jetstream said:

Yes, time can be an issue, here its the year of clouds/snow and rain. I was 90 miles north yesterday, clear as a bell into evening and drove into a wall of cloud not too far from this place. I guess thats why they call it Rainy Lake lol!

I hear you, I need 20 acres in Spain, Nevada, etc and a job working online! 👍 I'm halfway there with the job but would miss working in the field. Ah well...

[JTEC]

On 05/12/2019 at 22:39, Space Hopper said:

You have a similar set up to me JTEC.

Your experiences mirror mine. I've never used a C11, but had a C8 edge for a while.

As long as you keep the lightpath short, SCTs binoview superbly.

I have a 2" Powermate, but must confess to never using it with my Mk V. I have 2 Baader prisms and keep a 2.6x gpc permanently in one of them for high power use.

Hi Space Hopper.  It’s a great combo isn’t it.  I use the Baader prisms as well, having tried most other options - I’ve not found anything better and the Clicklock system is a real treat. I’ve used the 1.7 GPC (which reportedly gives more like x1.5) more than the others. I think they all work very well. You might think, as I did, that the Powermate (since you have one) is worth experimenting with. I haven't decided whether I think it’s ‘better’ than using the GPCs. It is nice and solid. With the PM, the TV T adapter lets you screw it direct to the bino - you unscrew the black section of the PM. As for eyepieces, I have some pairs of the Tak orthos which work well and I like the 18mm Tak LEs; also a pair of 28mm RKE’s which are a bit unusual but give those bright ‘floating’ views. If I had to pick one pair, it would prob be the Tak LEs.