Orthoscopic eyepieces

[Mike_S]

Hi, 
I've heard these are good for planetary and lunar for a sharp and high contrast view? I think I've got my collimation right now and was looking at ordering an eyepiece for my 10 inch dob as I've been posting about. I was going to order a 100/110 degree Myriad in 5 or 9mm. However do these give sharper views? I'm having real issues getting a sharp view of Saturn but haven't tried it since adjusting my collimation that I don't think was bad before anyway. 
Thoughts on these? What is the AFOV?
https://www.firstlightoptics.com/takahashi-telescope-accessories/takahashi-orthoscopic-eyepieces.html

[John]

The Takahashi Abbe Orthos have an apparent field of view of 44 degrees. Most orthoscopic eyepieces have something like this AFoV. Their eye relief is around 80% of the focal length of the eyepiece (another general orthoscopic characteristic) so the shorter focal length ones need you to get your eye pretty close in to the eyepiece top to get the full views !

They are very sharp eyepieces that show very little light scatter, no "ghosting" and little in the way of other distortions, so are ideal for planetary and other high resolution / contrast observing. The small AFoV, small eye lenses and tight eye relief can make them hard work to use with a manually driven scope such as a dobsonan - lots of nudging required at high powers to keep the target centered.

Overall good orthoscopic eyepieces can perform slightly better than premium ultra / hyper wide eyepieces at planetary observing. Of course the orthoscopics can also cost a lot less and do weigh a lot less than 82/100 degree eyepieces.

The question is, do you trade the comfort, convenience and immersiveness of the ultra/hyper wide view for the lower cost, lighter weight and slightly higher performance of the orthoscopics ?. Not always easy to answer !

There are other good orthoscopic designs around for less than the Takahashi's though such as the Baader Classic Orthoscopics and the Astro Hutech / Fujiyama / Baader Genuine Orthoscopics and also the venerable classic "volcano top" Circle-T orthos, which can be high performing bargains !

Sorry if thats not conclusive - eyepiece discussions rarely are

[Mike_S]

 That's brilliant John, I was hoping you would reply
The Myriads are cheap now as they're discontinued. £159-166. These are about £30 less. Had a really clear night last night. Moon was super sharp and clearer than ever. It seemed I could see millions of stars through my 25mm super.  I'm sure I should be able to get a sharper view of Saturn though and thats what I'm practicing most at the moment. Either with my 10mm with X2 barlow or my 4mm. Same on both. I really want a sharper view for now so think I might try an ortho. Are these all suitable for F4.7? Since posted this I have realised thet they're all around 40 odd degrees AFOV but I can manage. Would you recommend the Takahashi then?

[Mike_S]

Or this one? The review suits my scenario as well! 
https://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html

I am planning to order something tomorrow

[Mike_S]

Sorry I see you mentioned these. This turret set looks awesome value! I want! Solves the frustrating problem of routing around for eyepieces in the dark and the time to change them then re centre. 

https://www.firstlightoptics.com/eyepiece-sets/baader-classic-eyepiece-set-with-turret.html

[Ruud]

Othoscopic eyepieces have two conditions to fulfil: 
1:  magnification is very close to constant across the field (angular magnification distortion, AMD,  is then virtually zero)
2:  pincushion distortion must not exceed 5% (beyond that it becomes noticeable)

condition 2 limits the apparent field of view. If 1 is fulfilled, and if the afov does not exceed 44°, pincushion distortion will be under 5%. Hence the  44° limit. Beyond 44° pincushion becomes perceptible. (A bit of negative AMD could remedy that, but that by itself would be noticeable as the much more unpleasant"rolling ball effect".

The OED puts it like this:

Quote

 Orthoscopic: Having or producing correct vision; free from, or constructed to correct, optical distortion; spec. of binocular vision: without the reversal of convexity and concavity produced by pseudoscopic instruments.

The term has been in use since at least as far back as 1835.

Orthoscopic has always retained this meaning, but these days an added condition is implied: any aberration that distracts from the view must be imperceptible.

Even an eyepiece as good as the best Delos is not orthoscopic because Delos have a field of 72°, and at the edge of that field, pincushion is 13,5%. The inner 44° of the Delos eyepiece however  is oththodcopic.

Delos do have very little AMD and are virtually aberration free. Their only flaw is that their field is wider than 44°.

Here's an animation of the rolling ball effect. Panning across The Moon
makes it appear like a circle on a revolving sphere. This kind of AMD can 
remedy pincushion. 

And here is how (in the absence of AMD) pincushion varies with the afov:

 

 

 

 

 

[Ricochet]

It is worth remembering that Saturn is quite low in the sky this year and so you are looking through a lot of the Earth's atmosphere. The more atmosphere you have to look through the more it will degrade the image and so views of Saturn are likely to be affected. 

Having said that, if you're using the supplied 10mm then any of the options you have mentioned should have better performance, so long as the atmosphere allows it. 

Personally, I prefer wider fields if I am monoviewing to when I am binoviewing. For lunar and planetary I always binoview these days and my current favourite eyepieces for this are a pair of Baader BCOs that give approximately 135x or 200x depending on the binoviewer nose piece in use. I have no trouble tracking at 200x with the 50° field. 

[John]

8 hours ago, MSammon said:

Sorry I see you mentioned these. This turret set looks awesome value! I want! Solves the frustrating problem of routing around for eyepieces in the dark and the time to change them then re centre. 

https://www.firstlightoptics.com/eyepiece-sets/baader-classic-eyepiece-set-with-turret.html

I don't hink the turret won't work with a newtonian I'm afraid - there is not enough focuser travel generally.

Although they are very fine eyepieces, I'm not sure that I would invest in Takahashi orthos for use with an F/4.7 dobsonian, unless money was really no object. I might go for the 10mm and 6mm Baader Classics though at 1/3 of the price and 90% of the performance and not such a big investment if I then decided that a wider field of view and more eye relief was my preference in due course.

My high power eyepieces in my 12" F/5.3 dob are either the Ethos 8mm and 6mm or Pentax XW's at 10mm, 7mm and 5mm. I do have a set of othos which are very good but don't use them much in the dob to be honest. Comfort wins out for me and the "optical penalty" for that with the Ethos and Pentax XW's is very small I feel.

 

[Stu]

I think John’s advice is very good. Buying the Taks new would be a certain way to loose a lot of cash if you choose to sell them. The BCOs have a great reputation, I have their predecessors the BGOs and having had to sell all of my widefield Ethos’, Delos etc have mainly just been using these. They are a little tiring in terms of having to nudge the scope frequently, a tracking mount helps a lot, but the views are excellent, very sharp.

[Chris]

As you're using a Dob which requires a bit of nudging, it might be handy to combine orthoscopic views, comfort, affordability, and a wider field of view, in which case you might want to look at Vixen SLV's

Planets are low at the moment so we're looking through a lot of atmosphere and crud at the moment which doesn't help with achieving crystal clear views. 

[dweller25]

As mentioned above , if nudging a Dob consider Vixen SLV’s

[Timebandit]

 

Hi . Or look out for some second hand Pentax XW ,these should be around the same price as your Tak Orthodox link in the original post.

I use the Pentax XW in my dob and frac. They have a fov of around 70d, around 20mm eye relief and as sharp as a top quality Ortho IMO.

I am not just giving this advice on a wim, this is what I have actually brought and used. These eyepieces are top quality, and if you wish to buy a set of the 5mm to 10mm second hand ones then IMO you will not regret it. Certainly a keeper IMO. 

I hope this helps ☺ ?

 

 

 

[Nyctimene]

Excellent posts; especially John's two posts sum it all up very comprehensively. When it comes down to see the last details of a target - moon, planets, but DSO's as well -, I always put in an ortho.

Here is an interesting report by Alvin Huey from faintfuzzies.com, comparing widefield eyepieces to orthos on DSO details

(you have to scroll down to the last entry):

http://www.faintfuzzies.com/ObservingAids.html

Stephan

[Mark at Beaufort]

1 hour ago, Nyctimene said:

 

http://www.faintfuzzies.com/ObservingAids.html

Stephan

Thanks for this link Stephan - I was not aware of the 3 different Herschel 400 objects books. So as not to cause a problem with MSammon's original thread I will start another under observing.

[Mike_S]

Great replies thanks. Those Vixens look nice too. The extended volcano tip eyecup on the BCO’s looks a little awkward. Very pleased to hear some reasonably priced options, thanks. I will leave the takahashis for now as can’t see any second hand anyway. 

[Stu]

7 minutes ago, MSammon said:

The extended volcano tip eyecup on the BCO’s looks a little awkward

It does look a little odd, but I don't recall anyone having an issue with it. I've not used BCOs, only BGOs. Meade Research Grade Orthos are also worth watching out for. Very good optically and lightweight too.

[Mike_S]

Okay so I think I’m gonna to order the BCO 6mm and maybe the 10mm and use my X2 barlow. Is Barlow quality really important with these as mine is a very cheap one but Baader do a X2.25 for only £39.  

[Charic]

I bought the Baader Classic Ortho set based on their good reports. I really just wanted to try them out, see what the fuss was about ( Fuss in a nice way! ) and simply compare them to other eyepieces? but on one particular and difficult night whilst observing a crater on the Moon they gave me no better performance over what I'm presently using. The test was pretty simple, which of the following eyepieces would suit my eyes whilst looking at the Moon, which included Plössl's from Meade, TeleVue and Revelation[GSO]. I kept the Revelations!

I'm not sure if they were bought for keeps or testing, but I know they went to a good home?

[JOC]

13 hours ago, MSammon said:

£159-166.

Woah.....they are not cheap are they?  At that price point there are loads more EP's that you could consider which may be way easier to look through in terms of eye relief - the Baader Morpheous range come to mind!

[Charic]

20 minutes ago, MSammon said:

Okay so I think I’m gonna to order the BCO 6mm and maybe the 9mm.........

The BCO's I purchased were 6,10 & 18mm focal lengths.

There's a 32mm too.

[Mike_S]

Sorry yes just edited 

[Charic]

I edited too.......there's a 32mm

There's  been several mentions to Dob nudging, as if its a special art.
A wider field of view can/does help but I had an opportunity to use some Plössls last night,  and whilst looking at the primary target, if a satellite passed through the field of view, I was on it in a flash, held on axis.  I just don't have any  issues with manually tracking, but it does come down to practice and how smooth the scope is set.

Also the Moon was shifting last night at x375 whilst taking iPhone snaps, but its doable. 

[Mike_S]

Just going back to one of Johns points that he prefers the Pentax XW for comfort. Just wondering are they generally sharper for planets than say Myriad/Lunt 100/110 degrees?

it seems to be a trade off between contrast/sharpness and field of view for less nudging and easy of finding. 

[Mark at Beaufort]

8 minutes ago, MSammon said:

 Just wondering are they generally sharper for planets than say Myriad/Lunt 100/110 degrees?

 

@John is the best person to answer this question because he owns Pentax EPs and has reviewed the Myraid range. For information I have a 12" Dob and use the 20mm and 9mm Myraid EPs which I believe are v.good quality for the price. However, when it comes to viewing the Moon and Planets I much prefer binoviewers.

[jetstream]

26 minutes ago, MSammon said:

Just going back to one of Johns points that he prefers the Pentax XW for comfort. Just wondering are they generally sharper for planets than say Myriad/Lunt 100/110 degrees?

it seems to be a trade off between contrast/sharpness and field of view for less nudging and easy of finding. 

The XW's are perhaps the best planetary widefields out there, just the way it is.