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100mm Binoculars with 90 degree Eyepieces

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After coming out the other side of a serious illness over the last year I've decided to treat myself to something I've always wanted, a pair of 100mm astronomy binoculars with 90 degree interchangeable eyepieces.

The two main contenders I'm looking at are the Helios Quantum 6.3 22x100 Semi Apo Triplet Binoculars and the Altair 100mm 90 Giant Binoculars (which look like the same model sold by Omegon, Explore Scientific and a few others).

As I'm not in the position to test any of these out beforehand, can anyone here give some feedback, if they own or used either of these binoculars?

My main questions are: 

The most obvious generic question...out of the two, is one 'better' than the other and why?

Is the Helios really semi apo, in that it has better colour correction etc?

Why spend approx £300 more on the Altair model? 

Do both accept and focus a range of 1.25 eyepieces easily?

What would be the maximum usable magnification you'd expect from these?

What is the general build quality of both ? 

I'm assuming both have similar specs regarding things like multi coatings on all surfaces, type of prisms and they actually use the full 100mm aperture etc.

thanks for any replies


Edited by stuarts
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I can't directly comment on the models you mention as I've not used these or any other commercial offerings.  I do have considerable experience of self built binoculars/binoscopes with similar specifications so would add to your list of queries, whether either can be user adjusted for collimation and which supplier has the best returns policy.  Good luck with your research, large binoculars are wonderful instruments.      🙂

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You should also add, what is the best way of mounting such large instruments. I use a parallelogram for mine but they are only 80mm, not 100 so the weight difference will be quite large.

I would suggest using a parallelogram as they offer (IMHO) the best and most versatile way of mounting and then using them. For the weight of either you would be looking at the Orion monster version for OTS or maybe self building one.

I would expect both will accept 1.25 EP's but be aware of the thickness of "fat" eyepiece as they may not be able to move inward enough to match your interpupillary eye distance.

Maximum magnification is part ruled by CA avoidance and stability in my experience. I go up to x59 (60 max recommended) and the mount stability is slightly testing at this. You may get up to say x70-75 but a lot would depend upon your mount stabilty.

They are both F5.5 but the altair seems to have a better spec and the eyepiece are APM which are the same as I use with my giant TS optics ones. The APM perform superbly in them btw, I have 3 pairs of them. 

Regarding the Helios, although I personally was advised they would not be the first choice of big bins from someone, I have never actually used them. But the advice given was from a well respected member of this forum. 

Finally and this is just an FYI, I chose to have five sets of eyepieces. My 32mm plossl and 24mm APM UFF have an almost identical FOV, but the exit pupil is 5.6 (HB area) and 4.2 for the UFF which are my more general used pair. The pair I use most is the 18mm (supplied) but only just. The 32 plossl are used least, followed 10 and 8mm pair, I could in honesty make do with just the 10's but the other pair were a cheap 2nd hand buy so I thought WTH. 

Edited by bomberbaz
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The Altair should take most take eyepieces. The APM UFF are nice as ate Baader Morpheus. Not sure if the prism size as this might limit the lowest powers you can reach (some have a slightly larger prism that helps utilise 24mm eyepieces), best for nebulae. These are semi-APO so some CA will show, hugest power likely around 7mm before the views get too dim.

with a 90degree set the easiest mount will be a solid camera tripod and fluid head, though you might not quite get to the zenith (you can let one leg of the tripod down a bit if you need a bit more elevation).

inuse my 70mm with 12.5mm eyepieces on the daytime, very nice views. I tend to use the 18 or 24mm at night.




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I plan to mount it on a heavy duty Gitzo Carbon Fibre tripod and Manfrotto 503HDV Fluid Head I have, along with a long mounting plate to help balance it.

It should be enough to keep it stable.

Also I do have a SkyTee 2 mount which I guess could work.

Edited by stuarts
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52 minutes ago, stuarts said:

I plan to mount it on a heavy duty Gitzo Carbon Fibre tripod and Manfrotto 503HDV Fluid Head I have, along with a long mounting plate to help balance it.

It should be enough to keep it stable.

Also I do have a SkyTee 2 mount which I guess could work.

Manfrotto should work but the skytee should easily handle it also.

Don't know what your doing about a finderscope but I fixed a vixen clamp to the carry handle and now it has a 365Astronomy RDF mounted to it. Cracking finder that one. 

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I reviewed the Altair version for the November 2016 issue of BBC Sky at Night magazine. Very capable instrument, which I thought was good value at the time.

* Eyepieces: yes, all 1.25" eyepieces should fit, but do make sure that you get pairs from the same batch, because there can sometimes be variations between batches. Also, some with steps or safety-tapers on the barrels may not seat squarely. Max: I don't know; I only used the ones that Altair provided; I thought they were very good indeed: nice wide flat field.

* Build Quality: Robust. 

* Collimation (as per @Peter Drew's suggestion): Via eccentric rings on the front of the objectives. Note that standard 100mm lens tools may not extend far enough for the outer ring.

* Mounting: I used a UA T-mount (ideal!) and a Manfrotto 501 (which has a rated 6kg capacity compared to the 8kg  of your proposed 503). I don't know if the 503 would be adequate; the main issue is the increased turning moment as you get to higher elevations, which results in you have to increase the altitude tension or readjust the position of the QR plate in the head. With the 501, only about 55 deg was possible.

I hope that helps.


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Many thanks for the replies and suggestions.

I'm getting a feeling from what has been said, (and lack of comments on the Helios) that the Altair binoculars are the better option.

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  • 2 weeks later...

Hi Stuarts,

A bit late to the thread. I have an Altair 100mm which I'm very happy with.

As well as the supplied 18mm I've bought a pair of 10mm Altair 10mm flat field eyepieces which work also work very well.

I have it mounted on a Fotomate tripod and head which gives easy fore and aft movement for balancing, I can give you more details of it if you need.

I have the 45 degree version. Mods I have made are to reverse the mounting arm on the bottom of the bino to get better balance at high elevation and removing the carrying handle to fit a red dot finder, the latter is a big bonus.



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Hi Martin... many thanks for replying.

What sort of quality do you get at the edge of FOV with the Altair (particularly with the 18mm eyepieces) ?

Are there any niggles , however minor, you have with the binoculars ?

I was wondering about the 10mm flat field eyepieces so its good to know they work well. I was also thinking about the 24mm ones as well, that with my calculations should give x23 with a 4.4mm exit pupil.  



Edited by stuarts
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Hi Stuart

I am a new voice on SGL but have been using BT's for years. I have no experience with the models you are considering. I use an APM 100 ED APO BT and an APM 70mm NON ED BT.

Here are my thoughts for someone considering using BT's.

Binocular telescopes are superb instruments for wide field views and give fantastic 3D views of the night sky.

Mounts: I would recommend a good quality photo tripod with an adjustable centre column. Being able to adjust the height of the BT greatly increases viewing comfort. I use a 503 fluid head with my 70mm BT and it is just about adequate. I think it would struggle with a 100mm BT. With my 100mm BT I use the APM centre mount but I would also consider a fork mount for a 100mm BT

Eyepieces. My most used EP's are 24mm APM UFF and Morpheus 12.5mm in both scopes. They give excellent flat field views with good edge performance. My most used combinations are 24mm with my 70mm BT and 12.5mm in my 100mm BT - this gives x44 magnification and a shade over 2mm exit pupil. It is superb for open clusters.

I have used BT's for lower power Milky Way sweeping in the x17 - 44 range and have also pushed my 100mmBT to x110 to view the planets and the moon. I have seen Juipters GRS and Saturn's rings. The ED glass in the 100mmBT minimises any CA even on bright views of the Moon.

I have a number of instruments to observe the night sky from 8x30 bins to a 12 inch dob and if I had to use only one it would be my 100mm BT.

As always YMMV.


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