Ortho Collection - taking shape

[Mr Spock]

Just had a 4mm arrive so we are almost there. Just the elusive 6mm and 5mm to go.

Compared to the others the 4mm doesn't have a sharp field stop and doesn't appear to be adjustable either. As long as the image quality is there I can put up with that. Exciting times!

Magnifications in my 250mm:

25mm -    x48
18mm -    x67
12.5mm - x96
9mm -     x133
7mm -    x171
6mm -    x200
5mm -    x240
4mm -    x300

The missing ones are needed!

[Roy Challen]

That's a very nice clean set of orthos you have.

[Highburymark]

Very nice indeed! Good luck tracking down the 5mm and 6mm. Will make a superb collection.
Presume these are the spiritual successors to modern Fujiyama orthos, made by Kokusai Kohki? Do prefer the volcano tops at shorter focal lengths. Have a 6mm Fujiyama but the eye relief is too tight for me, so it’s in the ‘to be sold’ box at the moment. 

[Scosmico]

Great set! I hope you can find the missing ones soon.

Do you use it quite often?

I do have a complete BGO set that is used together with my 12" Dob. I find it the perfect match in terms of visual and physical balance of the Dob. I don't remember seeing darker backgrounds than I see with my orthos.

[jetstream]

4 hours ago, Mr Spock said:

Compared to the others the 4mm doesn't have a sharp field stop

Congrats for the fine purchase. My 4mm UO version of these is one of my best eyepieces, silly sharp and competes with eyepiece classes it shouldn't... The 12.5mm resides in the TSA120 as the firstline eyepiece to try.

[John]

Nice set !

I've owned a used a number of the 4mm's that did not have a sharp field stop. I've still got one of the Fujiyama HD "flat tops" with that issue. Otherwise it works pretty well though. Keeping the tiny eye lenses clean can be tricky.

I used to have a short set of the University Optics branded "volcano top" versions which were great. I find the eye relief and small AFoV rather hard work with my undriven scopes now though.

[Mr Spock]

Luckily my scope is driven so the small FOV isn't a problem.

The 9mm had a blurred field stop when I got it but was easily adjusted. On the longer focal lengths the field stop is a separate ring to the one holding the lenses in place. On the 4mm there's only the one ring - a combined lens holder and field stop, so, not adjustable.

I haven't used it yet, but if it's as sharp as the others I'll be well satisfied.

[Louis D]

11 hours ago, Mr Spock said:

Just the elusive 6mm and 5mm to go.

Not exactly minimal glass, but you could use a high quality 2x Barlow with the 12.5mm and 9mm or a 3x Barlow with the 18mm to get close for now to fill in the gaps.

At the very least, it would allow you to get some idea of what the missing powers would look like.

[Mr Spock]

I'm currently using a Meade 140 APO x2 Barlow which is supposed to be x2 but measures more. With the 12.5mm it gives (measured) x225 - which is half way between the 6mm and 5mm. 

[Mr Spock]

It does actually give a perfect x1.3 progression:

7mm = x171 - 171 x 1.3 = 222
12.5mm + Barlow =  x225 - 225 x 1.3 = 293
4mm = x300

Perfect for now 

[callisto]

17 hours ago, Mr Spock said:

my scope is driven so the small FOV isn't a problem

You've got me looking at these Japanese Ortho's now 😁....would these be ok in my 10" f4.8 Dob, It's on a EQ platform?

 

Mark

[Mr Spock]

1 hour ago, callisto said:

You've got me looking at these Japanese Ortho's now 😁....would these be ok in my 10" f4.8 Dob, It's on a EQ platform?

That's what I'm using - 10" dob. Image quality is outstanding; so crisp and clean.

Although I still like wide fields and long eye relief, for lunar and planets I won't be going back. 

[jetstream]

5 hours ago, callisto said:

.would these be ok in my 10" f4.8 Dob

I use them in an undriven 15" f4.8 and 24" f4.1 with no problem, they chew up faint galaxies and Pns.

[Pixies]

I have a few - not exactly as wide a range - a 7mm (University Optics) and a 6mm (sorry Michael) and 4mm Circle-T orthos.

When all else fails trying to split a tight double, these are the ones to do it.

[Saganite]

Excellent set of Ortho's !

I still have my UOVT Orthos in pairs at 18mm, 12.5mm, and 9mm, and would not part with them, though I thought until not too long ago that I would never part with my pair of 7mm units, but alas, the eye relief was no longer enjoyable, for my eyes.

I am sure that the 6mm and 5mm will appear soon.

Edited June 23, 2021 by Saganite

[F15Rules]

Good luck finding your last two to complete the set Michael 😊👍.

Although I don't have any now (you actually had the last one I owned 🤣!!), but I have a real soft spot for them. I've always found the volcano top design more comfortable than the Baader Genuine Ortho flat tops, although if I'm honest I found the flat tops slightly superior on contrast: the difference was very slight though...I often wondered how good a volcano topped BGO with their excellent Phantom Coatings would have performed 🤔😊..

Dave

[callisto]

5 hours ago, jetstream said:

they chew up faint galaxies and Pns.

Which ones do you use for those?  (sorry for all these questions guys, just I've never used these before) 

 

Mark

Edited June 23, 2021 by callisto
change wording

[GazOC]

 I've got all the UO volcano orthos from 4 to 12.5, they really are exceptional eyepieces. 

[jetstream]

5 hours ago, callisto said:

Which ones do you use for those?  (sorry for all these questions guys, just I've never used these before) 

 

Mark

I use the 5mm, 6mm and 7mm depending on the conditions. I have an exceptional 7mm KK ortho and the Circle T 7mm holds in own.  Orthos are my goto eyepieces for tough DSO regardless of aperture. Hickson 55 revealed 3 of its sections with the orthos/15" and was pretty pumped about it.

From dark skies, with your scope, try Stephans Quintet with orthos once found and in UMa the NGC 3982 is also ortho grounds. Same goes for small Pns...the Cateseye comes to mind, NGC 6543.

I have them all except the 25mm, but the 25mm TV plossl is superb and has needed tighter eye relief.

[jetstream]

On 22/06/2021 at 04:42, Mr Spock said:

Just the elusive 6mm

I might have an extra 6mm but we are 3700 miles apart. I'm sure you will find the missing members of the line up.

[Mr Spock]

I did some eyepiece tests a few weeks ago and one thing that surprised me was how much brighter the image was in the orthos compared to more complex designs.

[callisto]

7 hours ago, jetstream said:

I use the 5mm, 6mm and 7mm depending on the conditions. I have an exceptional 7mm KK ortho and the Circle T 7mm holds in own.  Orthos are my goto eyepieces for tough DSO regardless of aperture. Hickson 55 revealed 3 of its sections with the orthos/15" and was pretty pumped about it.

From dark skies, with your scope, try Stephans Quintet with orthos once found and in UMa the NGC 3982 is also ortho grounds. Same goes for small Pns...the Cateseye comes to mind, NGC 6543.

I have them all except the 25mm, but the 25mm TV plossl is superb and has needed tighter eye relief.

Thanks for that 👍

Well, it looks like a gonna have to get a couple of these ortho's and try them out

 

Cheers,

Mark

[John]

1 hour ago, Mr Spock said:

I did some eyepiece tests a few weeks ago and one thing that surprised me was how much brighter the image was in the orthos compared to more complex designs.

Some data here. A bit out of date now but it does include the Kasai Orthos which I believe are the same:

http://www.amateurastronomie.com/Astronomie/tips/tips3.htm

Pentax XW's have 96% light transmission I believe.

The difference in peak transmission between a Nagler Type 6 and a Zeiss ZAO ortho is around 2%. Surprisingly little.

Personally, I thought that the later HD type orthos (eg: Baader Genuine Orthos, Fujiyama Or's, Astro Hutech and Baader Classic orthos showed slightly brighter DSO images and a touch less light scatter around bright objects than the classic "volcano top" orthos when I compared them for the forum but that was quite a while back now. I assumed that this was due to more effective coatings on the later eyepieces. The "volcano tops" are still very good eyepieces though.

Back then I remember hoping back then that a "volcano top" range that contained HD ortho optics would be produced which would have been a great idea 

As I said, my comparisons were done a few years ago now so my memory might be playing tricks on me

 

 

 

Edited June 24, 2021 by John

[Mr Spock]

Interesting. A while ago I had a 10mm Radian which I compared to my 10mm NLV - they were about the same. Comparing the 10mm NLV to the 9mm ortho the latter is significantly brighter when looking at my white test chart. In photographic terms maybe ⅓ a stop difference or more.

[jetstream]

10 hours ago, John said:

Pentax XW's have 96% light transmission I believe.

The difference in peak transmission between a Nagler Type 6 and a Zeiss ZAO ortho is around 2%. Surprisingly little.

This transmission stuff is something I dont understand...the difference in measured transmission doesnt always reflect what the eye notices IMHO. The optical experts say the levels of difference cant be noticed and yet I personally do see it.

The 10BCO is my king of "transmission" ie object detection. The Nagler 3-6 zoom is near the bottom of "transmission" to my eyes eventhough it is a great lunar/planetary eyepiece.

All I know is that the top DSO observers all use orthos at high mag for faint threshold objects. It is an absolute bonus that these orthos, Circle T included offer top tier views of the moon and planets.

I have a UO Tani 4mm ortho that is unbelievably good, so good that it takes the Vixen 3.5mm HR to knock it off the stump, and that is quite an accomplishment.