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Orthoscopic ep's in a 12 inch dob

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#1 Itz marcus

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Posted 03 December 2019 - 08:21 AM

Hi,

I would like to buy a few ep's for my dob. I dont have the funds for the 82 deg. ep's etc. I do remember how good the U.O. volcano orthos were in my refractor (EON 120). Do they work well in f5 reflectors? I'm aware that the fov is small but as I live in the light POISONED capital of the world I rarely get more than planetary and bright DSO's. I am looking at the 25mm  the 18mm and the 7mm which would give me 60x and 83x and 214x and when barlowed would give me 120x and 160x and 428x (if seeing ever permits that). 

Anyway, would they be just as good as in the refractor or should I save and go for ES 68 deg ep's?

Clear Skies

Itz



#2 sg6

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Posted 03 December 2019 - 10:06 AM

Half guess the problem may be getting good Ortho's these days. Also "Ortho" is a "property" not a specific design, many mean/think Abbe Ortho's but not all Ortho's are Abbe Ortho's. TV plossls are good but budget and eye relief are the concern. Not sure what Ortho's are like for similar.

 

Not sure but ES 52's may be a possibility, seems they get good reports and the "negative" is the field, plossl like, or Ortho like I suppose.

 

Unsure of availibilty are Antares Ortho's, used to be good but Antares seem to have "gone" - half think they are owned by someone else now so things will have changed.

 

If you are in a club I suggest you nicely ask to try out a few of the eyepieces that fit your budget and are available.

 

Odd thought - if you are in a club how about arrange a night for people to bring alone a selection of equipment for others to try out. So many times it seems we go round asking "What about XYZ?". Would be nice to have the possibility to try. Needs people to partake but could be useful, and hopefully fun.



#3 Ihtegla Sar

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Posted 03 December 2019 - 10:41 AM

Not sure but ES 52's may be a possibility, seems they get good reports and the "negative" is the field, plossl like, or Ortho like I suppose.


The other "negative" with the ES 52's is light scatter. They are in desperate need of flocking but if you open them up to flock them, you lose the argon. Other than that, they are very good eyepieces. But had I known about the light scatter issue I may not have purchased my set.

#4 csrlice12

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Posted 03 December 2019 - 10:43 AM

Our club has an annual "auction" where members can bring equipment to sell/auction off.  Good way to sell excess stuff and maybe find something you need.  I've seen everything from simple eyepieces thru complete 6" refractors, goto mounts, and decent sized dobs.  Most all equipment is well cared for.  

 

We also have monthly public nights.  Find a scope similar to yours, talk to the owner, chances are his good eyepieces are in the car waiting for the crowds to leave.



#5 John Fitzgerald

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Posted 03 December 2019 - 10:49 AM

Orthos don't work as well in fast telescopes.   They are best, I have found, in f/6 and slower.  The OP on a budget would be better served to try to find some used TV Plossls or Radians at a bargain price,  IMO.

 

Used ES 68s also should work decently.  Watch the classifieds here.


Edited by John Fitzgerald, 03 December 2019 - 10:50 AM.

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#6 areyoukiddingme

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Posted 03 December 2019 - 01:23 PM

Are we talking about a manual Dob, and how big are we talking?

 

While orthos are likely to be sharp, as pointed out they are better with slower focal ratios. 

 

With a manual Dob, I much prefer eyepieces with a greater field of view, and decent eye relief.

 

For me orthos with 40 odd degree fields are just too narrow, and the eye relief starts getting tight in the 6mm or so range.

 

I think if you have a tracking scope, and/or use in your refractor orthos are fine. Otherwise I’m all for 70 degrees or more.


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#7 Jeff B

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Posted 03 December 2019 - 02:52 PM

Hi,

I would like to buy a few ep's for my dob. I dont have the funds for the 82 deg. ep's etc. I do remember how good the U.O. volcano orthos were in my refractor (EON 120). Do they work well in f5 reflectors? I'm aware that the fov is small but as I live in the light POISONED capital of the world I rarely get more than planetary and bright DSO's. I am looking at the 25mm  the 18mm and the 7mm which would give me 60x and 83x and 214x and when barlowed would give me 120x and 160x and 428x (if seeing ever permits that). 

Anyway, would they be just as good as in the refractor or should I save and go for ES 68 deg ep's?

Clear Skies

Itz

Actually the APM Ultra Flats may be exactly what you need.  They come in 24, 18, 15 and 10mm FL's in the 1.25" format, 65 degree AFOV, are very well made, very "reasonable" in price, and IME perform nicely at F5 (Also see raytrace number 31):

 

https://www.telescop...ce_raytrace.htm

 

I love mine.  Check'em out:

 

https://www.apm-tele.../eyepieces.html

 

 

Jeff


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#8 Asbytec

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Posted 04 December 2019 - 06:14 AM

"I would like to buy a few ep's for my dob...I'm aware that the fov is small...I rarely get more than planetary and bright DSO's."

I think a smaller field works against panetary observation. You need some amount of (well corrected) drift time to catch the best seeing moments. With a smaller FOV and an undriven alt az mount, I feel like I spend a good part of my observing pass tracking, or getting ready to track, rather than observing.

At high planetary magnification, most of a 60 to 70 degree AFOV can be well corrected and offer sufficient drift time for observating. Orthos served me well, however, with a manual GEM and a simple turn of the RA knob (at f/13, anyway). As Jeff said above, you can pick up a nice APM UFF for about the price of a good Ortho. I like mine, too, at F/6 with a focal extender. The AFOV buys some breathing room.

Drift time is important to observing. I'd encourage - at least - 60 degrees of well corrected AFOV for lunar and planetary.

Edited by Asbytec, 04 December 2019 - 06:24 AM.

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#9 Itz marcus

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Posted 04 December 2019 - 08:15 AM

Hi,

Thanx for the info guys.

As far as drift time I observe with a roundtable platform so the small fov shouldnt be a problem I just want to get the sharpest views and the clearest double star splits possible.

I am looking into all the suggestions given.

Clear Skies

Itz


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#10 Allan Wade

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Posted 04 December 2019 - 08:47 AM

I just had 4 nights on my 32” chasing some specific targets. I used my Abbe Orthos for about 12 hours of that observing because I was after better performance than I could get from my widefields. 

 

I obviously got pretty comfortable with my 9/6/4 Tak Abbes and ZAO’s over those nights. Something I want to share with the forum, because I was looking for it very closely, was that these eyepieces were very well corrected to the edge in my f/3.3 dob with the SIPS.

 

They have a reputation for poor edge performance in fast scopes, but my experience over a long period of time doesn’t bare that out at all. Though I’m not including any long focal length Abbe orthos in this conversation, as I don’t typically use those in my fast dob.

 

But for Itz, as long as you are using a Paracorr at f/5 even the long focal length Abbe Orthos will perform well.


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#11 Don H

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Posted 04 December 2019 - 01:52 PM

Hi,

Thanx for the info guys.

As far as drift time I observe with a roundtable platform so the small fov shouldnt be a problem I just want to get the sharpest views and the clearest double star splits possible.

I am looking into all the suggestions given.

Clear Skies

Itz

Many affordable 60* eyepieces also offer more eye relief than an Ortho, providing extra comfort when making critical observations. 


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#12 areyoukiddingme

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Posted 04 December 2019 - 05:35 PM

Hi,

Thanx for the info guys.

As far as drift time I observe with a roundtable platform so the small fov shouldnt be a problem I just want to get the sharpest views and the clearest double star splits possible.

I am looking into all the suggestions given.

Clear Skies

Itz

You have a tracking platform?

 

If that's the case, and you can tolerate the small eye relief, then for center of view sharpness, you'll not do better than a good ortho.

 

But you can probably do close to as good, or as close as can be perceived. Delites might be a good choice for critical sharpness.

 

I've tried Takahashi 6mm ortho, a University Optics 6mm ortho, and Takahashi TOE 4mm. 

 

None of them are better than a Nagler 3-6 zoom for sharpness. The Tak ortho was possibly a little behind, and the other two are on par, but not better.



#13 ltha

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Posted 04 December 2019 - 06:34 PM

Hi Its,

 

I have a Portaball 12.5" F/5 and have enjoyed using orthos for planetary for years. Have tried everything from old UO "volcano tops" to Zeiss 1.25" Abbes. Sharpness on lunar and planetary is excellent. Yes, the FOV is a bit small for "push to" but even that as not a big issue to me. I also own a Roundtable platform but do not always set it up as I enjoy the simplicity of the PB. 

 

Larry




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