Bino Session

[Nightspore]

I really couldn't resist observing a setting Moon so I set the *Big Mak up at 20:30 so it could cool nicely.

 

 

This is the first real chance to give the 20mm WO eyepieces a good workout. I started off with 75x and a Baader Single Polariser in the diagonal.

 

 

I mainly used the WO's but did try the 12mm GSO Plossls briefly.

 

 

As it got darker I used the 1.6x and 2x WO Barlows for 120x and 150x. The seeing or transparency weren't good enough for the TS Optics 2.6x Barlow.

 

 

I also saw Jupiter right up until transit. I now had a Baader Neodymium filter in the nosepiece. Again, not brilliant as the conditions hadn't greatly improved but I could see the GRS. I also saw a rising Saturn for a short while. So I'm a pretty happy bunny.

 

 

*At 127mm it's my biggest Mak, so it's big to me lol.

[Smithysteve]

A good session, nice photos too ?

[Nightspore]

1 hour ago, Smithysteve said:

A good session, nice photos too ?

Thanks. The transparency did improve as it got later, although by then the Moon was getting low.

 

 

Jupiter and Saturn were a bit of a bonus as I thought I wouldn't be able to see them.

 

 

I found that the 20mm WO SWAN's were pretty easy to merge. They are 72° but I reckon the bino’s only show around 66°.

 

 

Edited July 8, 2019 by Nightspore

[Guest]

To be pedantic, I wouldn't call 127mm a big Mak. I have one and really enjoy using it. I tend to think one of 200mm as big and 127-150 as "medium".

[Nightspore]

On 09/07/2019 at 13:05, Sunny Phil said:

To be pedantic, I wouldn't call 127mm a big Mak. I have one and really enjoy using it. I tend to think one of 200mm as big and 127-150 as "medium".

It's big if you are partially paralysed in the right arm, hand and leg. As the AZ5 was set low it wasn't so difficult to slide the OTA into the dovetail. I'm slowly getting some dexterity and range back into my right arm and hand. I did practice a bit though, just to be on the safe side. Sitting directly behind the visual back seemed more logical than rotating the diagonal. Any OTA above 10cm is difficult to pick up with one hand. I need to utilise a large belt to get my 9.25" (235mm) Celestron Evolution SCT into its mount lol! It's precarious but I can do it.

 

 

When you have a fairly severe physical disability everything is a logistics exercise. I have to plan how to carry each item of equipment out safely and then assemble it. This isn't always straightforward. As a consequence I tend to use smaller scopes a lot. The ED72 on a Porta II/Polaris tripod tends to get a lot of use.

 

 

Getting the APP-TL130 back into this little bag with one good hand can be bloody frustrating though ROTFL.

 

[philjay]

The 127 mak punches above it,s weight, apo performance within a sub 300 pound package. I had mine for longer than I had my 180mak, which I called my big mak. Ive often been tempted to get another 127.

Physical disability, is really limiting, I sympathise, my C11 had to go because I couldnt manage it at the time. I had many nervous moments setting up and taking down.

 

[Nightspore]

12 minutes ago, philjay said:

The 127 mak punches above it,s weight, apo performance within a sub 300 pound package. I had mine for longer than I had my 180mak, which I called my big mak. Ive often been tempted to get another 127.

Physical disability, is really limiting, I sympathise, my C11 had to go because I couldnt manage it at the time. I had many nervous moments setting up and taking down.

 

The difference between the 127mm Mak and my 102mm Mak is quite startling. I almost considered a 150mm SCT instead of the 127mm Mak as I originally intended to use it on a Porta II/Hal 130 combination.

 

I think I'd need a JCB to mount a C11 lol.

[+Bino-viewer]

A tip i learned from 'Eddgie' over on 'Cloudy Nights' :

 

When using binoviewers with Catadioptric scopes, be it SCTs or Maksutovs, try and keep the lightpath distance 

ie the point from the back of your scope to your eyepieces as short as possible.

 

With one of theses scopes, if your put a visual back, and a regular mirror diagonal, with a long nosepiece, and add something like a clicklock etc,

then put a binoviewer in there with eyepiecs, you're adding way too much length to the optical lightpath.

A big 2" diagonal (instead of a 1.25) is even worse due to its size and length.

 

I'm not saying the above won't work at all, and you may even be fairly happy with the views, but your scope will no longer be working optimally at its intended aperture.

 

I've read lots of reports over the years from observers trying bino's out with SCT/Maks saying the image is dim, not very bright, over magnified, poor contrast.

Thats because it is. The blame the bino, give up on it, and go back to cyclops viewing.

 

If you go beyond a certain length of lightpath, and i think its around 160 - 170mm (the bino itself is around 110=120mm) this is what will happen :

 

To focus with such a long lightpath, you end up winding in the primary mirror a long way in along its travel, to a point where it gets too close to the secondary mirror,

and the outer part of the primarys reflected light is clipped off and lost. This is aperture loss.

It may only be a small amount (less than an inch) with a small scope, or quite a bit (2 inches) with a larger scope like a C14.

 

So your 127mm scope is no longer a 127mm scope, but probably closer to 110mm.

 

Its no longer the focal length it was either, but something much longer. As you increase lightpath you increase focal length too and its magnified.

Your focal ratio is no longer F12 (or F15?) but something bigger.

The magnification you thought your eyepieces were giving you is actually much bigger.

Contrast is degraded. As you lose the outer part of your primary (the best bit) to aperture loss, your secondary mirror obstruction size, as a percentage, is increased (up past 40%)

You'll also be introducing Spherical Abberation (as much as 1/5 of a wave) into your view as well, degrading the image you see still further.

 

But, you can mitigate all of the above by keeping the lightpath to a minimum.

 

This means :

 

Ditching the visual back saving about 40mm of lightpath straight away.

Investing in a low profile type diagonal. This couples directly to the binoviewer (assuming compatibility) at one end, and uses a short 10 or 15mm adapter to connect the diagonal straight on to the

SCT thread at the back of the scope.

 

Big 2 inch mirror diagonals with nosepieces and Clicklocks take up way too much lightpath !!

 

 

Like i said, you may be happy already with the views you have and that is great.

But if you want your telescope to perform optimally, as designed, to its given aperture (and who doesn't ?) then keep the lightpath as short as you can 

when you use a binoviewer with these type of scopes.

 

Below is an image of my old C8 with a Baader Maxbright binoviewer in an optimal configuration.

When i had it, i did an experiment an put a 2" diagonal onto the original visual back with an adapter, and then added the binoviewer, and believe me,

the views were a lot dimmer, and not as contrasty as they were with the short lightpath kit on, and everything was rather precarious as well.

To me, to have an 8" scope only performing as a 6.5 - 7 inch scope would be a deal breaker, knowing all the hard earned money i had invested in the scope had resulted in something

that wasn't performing as it should.

 

Hope this is of use to someone  !! 

Comments welcome ?

 

 

 

 

 

 

 

 

 

Edited July 11, 2019 by Bino-viewer

[Nightspore]

That's interesting. Probably a bit too technical for me though lol. I've always suspected that the magnifications seemed higher than they should be with a bino. But I've heard other explanations for this. I was actually using a 1.25" Omegon Amici diagonal. Plus 1.6x and 2x WO Barlows/GPC's.

 

 

These work well in cat's and the filter threads are compatible with most of my 1.25" filters, even Lumicons.

 

 

I have no idea who the OEM is, I suspect Long Perng.

 

 

Just a head's up on the drawtubes, they don't thread off! I'm guessing brazed. lol