Bino-dso session

[Paz]

I haven't done much DSO observing since the March lockdown, mostly sticking to solar system targets that are relatively easy to find and easy to observe as I could do without the stress of testing my limits trying to spot faint fuzzies and navigating tough star hops. However since getting into binoviewing I have been thinking about trying them out on star clusters, my thinking being the brighter clusters might be ok. Tonight I decided to get out there and give M44 a go which Skysafari tells me I should be able to frame (just).

The sky looked clear-ish of clouds tonight and the moon was out of the way so I decided to set up with the ed102r, 1.25x gpc, Maxbright 2 binoviewers, and 17.3mm Delos. That in theory would mean a 2mm exit pupil, 52x magnification, and 1.4 degree true field of view, which is good for many DSO's. I took no other eyepieces out, I wanted to stick to one set up and make the most of that.

I have to take my set up up some concrete steps to the back garden patio so it takes a few trips. On my last trip setting up the garden has become bathed in a bright glow! It turns out my son is going to bed and reading a book with his bedside light on but he has no curtain as his room has just been refurbished. He thinks his room is quite dim(!), I decide not to make an issue of it, I know he will be conked out within half an hour. 

The binoviewers plus Delos are quite a heavy lump and so I am very careful checking everything is secure and balanced. I line up my finder on Pollux to hop to M44 and I get into a pickle immediately, not finding it at all when it should be easy. After a few minutes of getting increasingly confused I realise I alighted my finder on Procyon not Pollux - how is that possible - arrrgh! 

I moved up to Pollux and hopped over to M44 - it looks promising and once I get the focus spot on things are looking very good indeed. I have lights blazing into my eyes from houses on my left and right plus the usual light pollution above so the field is mottled grey and the contrast is blunted a bit, but the view is great - the views is sharp, flat, and merged, and I've got my observing chair so all-in the view is very physically easy to observe at length.

I can see that I am getting slightly less field of view than Skysafari suggested. In order to get enough backfocus with a 1.25x gpc I put the gpc n front of the diagonal rather than behind it - this throws out a bit more backfocus but at the same time ups the magnification a little. I had the focuser racked 7mm out and started wondering if I might be able to cut enough more from the light path to observe without any GPC, I guess probably not but make a note to try it.

I had intended to only observe M44 - the more experience I get the fewer targets I observe in a session and the more time I spend on each. It I could not quite frame M44 as I had hoped and I found myself wondering what other clusters would look like so I moved over to M35. This was absolutely winning - perfectly framed, plenty bright enough, and as good a feeling of actually being out in space as I can recall using Naglers and my dobsonian. The more observing I do the more I wonder if there will be any more "wow" moments as one's expectations go inexorably upwards and get harder to exceed, but this was a proper "wow" moment. I wondered what else I could try, and ended up tearing around checking everything out like I did when I started out observing - with long lists that I never got anywhere near covering. I tried Collinder 82 but it was a bit too big for this set up. Auriga was sliding into a tree so I moved over to that to bag some clusters before they hit the branches. Collinder 62 ok, M38 great, NGC1907 faint fuzzy, M36 nice but M38 was better, M37 winning! I forgot M67 earlier so I went back and had a look at that - great stuff - delicate and well framed compared to M44 that looked like a sea of bright stars which my brain for some reason seems to group into innumerable triangles.

My son's light is out now and the street lights are off, but a neighbour has to lights on and curtains open so I'm not going to get as good a view as I hoped but I am stoked and want to keep going. Leo is up and I decide to go galaxy hunting. M66 M65 and NGC3628 - very faint but cores seen with direct vision and some elongation and PA certainly evident with averted vision on 66 and 65 (I can't remember if the same was true for 3628). M105 - seen, NGC 3384 - not seen, M96 super faint and diffuse - expands and contracts as I switch between direct and averted vision. M95 - seen but the toughest of them all. All the galaxies seen were faint fuzzies with no structure other than extension and elongation for some but I was very happy with the views. M66 and M65 floating alongside each other was the highlight here.

I wondered about nebulae and going inside to get a filter but looking on Skysafari there's nothing easy to find and observe that presents itself so I decide to quit while I'm ahead - this is the best session I have had in some time. One of those where you go out with no expectations but end up with some epic views.

 

 

 

Edited February 6, 2021 by Paz

[Stu]

Great setup and lovely report @Paz Gotta love those Delos, binoviewing must be amazing with them.

Looks like your optical path is as short as it can be. If that’s a T2 prism you won’t get any shorter than that with the same quality and with solid connections.

[RobertI]

Interesting read. I have been wondering about binoviewing the brighter  DSOs, so that was an interesting read. I have virtually the same setup, and get 56x with my 1.6 GPC and a FOV of 1.2 degrees, so should be good enough for clusters.  I’ll give it a go next time. 👍

[Paz]

4 hours ago, Stu said:

Great setup and lovely report @Paz Gotta love those Delos, binoviewing must be amazing with them.

Looks like your optical path is as short as it can be. If that’s a T2 prism you won’t get any shorter than that with the same quality and with solid connections.

Yes the Delos are great, its like peering into a pair of perfectly still infinity pools. I think because I'm already used to them cyclops observing it has been seamless getting used to them in binos. I have glasses on and the eye cups low so my big nose is far enough back that everything fits well. If I observed with no glasses and the eye cups touching my eyebrows then my nose wouldn't fit.

I think my preferred idea from here is to add 12mm Delos and 22mm LVWs to these 17.3mm Delos and 30mm NPLs I already use and that's me done. Except that finding a pair of 22mm LVWs is never going to happen.

Yes that is the T2 quick connector and bayonet, a really useful thing, in fact I bought a second set for attaching the binos to my SCT and maksutov more easily and securely.

[Space Hopper]

Nice report @Paz and good to hear you are enjoying the Max 2's

I've been really impressed with mine. In fact if i'd had the chance to compare them with the Mk V back them, I would not have purchased the Mk V at all.

They are great value for money, perform very well with lowpower wideangles like the 24 Panoptic, and have , by quite a distance, the best designed eyepiece holders

and diopter adjusters i've seen.

You may find, the Delos themselves, throw the focal plane out by quite a bit.

When you say 'the GPC behind the diagonal' do you mean actually screwed into the back of the bino ? Or somewhere else ??

Putting it scope side of the diagonal will certainly up the magnification, perhaps giving you 1.5 - 1.8x

In my own 4" 105mm / 650 scope i can reach focus with no GPC at all.

I look at clusters from time to time as well and with the 24 Pans the M45 Pleiades are nicely framed.

But 4" doesn't really give me that WOW from home with clusters (Bortle 7) and its the same with my bigger scope as well. 

A darker sky is a different matter of course, and makes such a difference.

I used to have a 300mm reflector, and that gave stunning views of clusters at dark sites. M13, M11 and the Double Cluster were all spectacular. 

If i'd had better home skys i'd have kept it. I couldn't even see M1 in it from home.

[Kon]

Very nice report and a nice list of targets you managed.

[Paz]

6 hours ago, RobertI said:

Interesting read. I have been wondering about binoviewing the brighter  DSOs, so that was an interesting read. I have virtually the same setup, and get 56x with my 1.6 GPC and a FOV of 1.2 degrees, so should be good enough for clusters.  I’ll give it a go next time. 👍

That will be a fine set up,  will be interested to hear what you think.

[Paz]

5 hours ago, Space Hopper said:

Nice report @Paz and good to hear you are enjoying the Max 2's

I've been really impressed with mine. In fact if i'd had the chance to compare them with the Mk V back them, I would not have purchased the Mk V at all.

They are great value for money, perform very well with lowpower wideangles like the 24 Panoptic, and have , by quite a distance, the best designed eyepiece holders

and diopter adjusters i've seen.

You may find, the Delos themselves, throw the focal plane out by quite a bit.

When you say 'the GPC behind the diagonal' do you mean actually screwed into the back of the bino ? Or somewhere else ??

Putting it scope side of the diagonal will certainly up the magnification, perhaps giving you 1.5 - 1.8x

In my own 4" 105mm / 650 scope i can reach focus with no GPC at all.

I look at clusters from time to time as well and with the 24 Pans the M45 Pleiades are nicely framed.

But 4" doesn't really give me that WOW from home with clusters (Bortle 7) and its the same with my bigger scope as well. 

A darker sky is a different matter of course, and makes such a difference.

I used to have a 300mm reflector, and that gave stunning views of clusters at dark sites. M13, M11 and the Double Cluster were all spectacular. 

If i'd had better home skys i'd have kept it. I couldn't even see M1 in it from home.

I was going to give up with binoviewing as the top end binos were so expensive and also big/heavy and I had bad luck  with lower end binos, bit when the MB2 was announced I decided to try that when it came out - and it is fine - lighter, smaller, shorter light path, and cheaper than the big boys but not far off on quality from what I had read.

The gpc was as in the picture below... screwed into the back of the nosepiece which then screws into the front of the diagonal.

[Ricochet]

23 hours ago, Paz said:

If I observed with no glasses and the eye cups touching my eyebrows then my nose wouldn't fit.

That's the problem I found when I tried using XWs in BVs. I also found that in the horizontal direction only 60-65° is visible simultaneously with both eyes so there is a resolution drop before things get to the field stop. As a result my current plans are based around Delites and a pair of 24mm Pans.

[jetstream]

On 05/02/2021 at 21:08, Paz said:

I wondered about nebulae and going inside to get a filter

Great report!

The very best view of the Needle galaxy was with my binoviewers. Those Baaders look excellent and won't be behind any other bino IMHO- they will be on par with the best.

So... have you explored the "false exit pupil" idea? Many thoughts, ideas and calculations... long story short is that the beam splitter halves the light to each eye making things dimmer and such that binocular summation does not recover it.

With respect to your Delos 17.3 at 1.25x GPC =13.8mm fl. If we can believe the false exit pupil idea then the effective fl could be 6.9mm fl (whatever it really is its dimmer view). Not sure of your scopes fl.

IMHO if you want to view galaxies lower the mag quite a bit, if your scope is f7 then the 17.3 might really be giving you a 1mm (false) exit pupil. I use 32mm TV plossls in my 15" dob with the powerswitch at 1.3x for a false exit pupil of about 2.56mm. I have had staggering views of the bright galaxies and also M42, but also had very limited success on the dimmer nebula that need filters.

The Leo triplet is another favourite with this combo, any of the bigger and brighter ones can work well. Nothing beats clusters with binos...

Another thought- my 15" dob/Moonlight will de collimate a bit with very heavy eyepieces/bino past half travel... are lighter eyepieces better for a dob?

Excellent report and observing, Gerry

Edit: The 15" would give 3.6mm false exit pupil not 2.56. 1828/24.6=74 .   269/74=3.6mm false exit pupil. Sorry for the mistake its been years since I thought about this. I just know what to do now.

Edited February 10, 2021 by jetstream
clarify, mistake

[jetstream]

I was off a bit-from a fellow that figured this stuff out https://www.cloudynights.com/topic/61467-binocular-vision-summation/

"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."

 

Edited February 10, 2021 by jetstream

[Paz]

On 10/02/2021 at 04:46, jetstream said:

Great report!

The very best view of the Needle galaxy was with my binoviewers. Those Baaders look excellent and won't be behind any other bino IMHO- they will be on par with the best.

So... have you explored the "false exit pupil" idea? Many thoughts, ideas and calculations... long story short is that the beam splitter halves the light to each eye making things dimmer and such that binocular summation does not recover it.

With respect to your Delos 17.3 at 1.25x GPC =13.8mm fl. If we can believe the false exit pupil idea then the effective fl could be 6.9mm fl (whatever it really is its dimmer view). Not sure of your scopes fl.

IMHO if you want to view galaxies lower the mag quite a bit, if your scope is f7 then the 17.3 might really be giving you a 1mm (false) exit pupil. I use 32mm TV plossls in my 15" dob with the powerswitch at 1.3x for a false exit pupil of about 2.56mm. I have had staggering views of the bright galaxies and also M42, but also had very limited success on the dimmer nebula that need filters.

The Leo triplet is another favourite with this combo, any of the bigger and brighter ones can work well. Nothing beats clusters with binos...

Another thought- my 15" dob/Moonlight will de collimate a bit with very heavy eyepieces/bino past half travel... are lighter eyepieces better for a dob?

Excellent report and observing, Gerry

Edit: The 15" would give 3.6mm false exit pupil not 2.56. 1828/24.6=74 .   269/74=3.6mm false exit pupil. Sorry for the mistake its been years since I thought about this. I just know what to do now.

That is interesting, I've read about the effect of splitting the beam in half and so each eye gets a dimmer image, but I had not come across the false exit pupil method of articulating it.

Hopefully over time I can work out when/where binoviewing is preferable and when mono is preferable in practice.

The lowest magnification  I can get at the moment is with 30mm NLVs but with a little bit of vignetting, I'll try them out next. I have a 32mm Televue Plossl so I can try that out in one side for comparison.

[jetstream]

11 hours ago, Paz said:

Hopefully over time I can work out when/where binoviewing is preferable and when mono is preferable in practice.

I was going to get 40mm 1.25" EPs for filtered bino use but thought in the end that mono was better for most nebula. M42 though, man is that super in the binos. Im interested in what you find out. The 32mm TV plossls with the powerswitch are the most used. I normally bino the 15" dob. Purists say "yeah but your cutting off the light cone" or "you have more obstruction with OCS in there.

Bottom line- binos really do work IMHO.