Suitable widefield ep for Orion OMC 140

[PaulB]

I have the deluxe version of the, Orion Optics OMC 140.

But at 2000mm fl. I really need a suitable WF EP for observing DSO's.

I suspect a 40mm giving 50x mag, would be suitable. Does anyone here have any recommendations? 

[Louis D]

With a 31.7mm optical back, you're pretty well limited in how wide you can go before vignetting sets in.  A 1.25" 40mm isn't going to be any wider than a 1.25" 32mm.  Both will have a 27mm field stop.  I don't know if there's a focal reducer available for this scope, but that might be an option.  Going with a 40mm would give you a slightly larger exit pupil which would make nebulosity more concentrated and slight brighter, though smaller.  What sort of DSOs are you wanting to observe with it?  I see you are quite the astrophotographer based on your webpage.  Are you trying to get into visual observing now?

[PaulB]

Hi Louis,

I started out in 1990, as a visual observer, before switching to digital imaging.

I brought the OMC 140 last year, to use with my IOptron MT2. The idea was, to start observing DSO's but also double stars, from our society's local dark sky patch. It has enough light grasp for observations of  a good number of DSO's. 

It would be very interesting to try out a reducer. And that has given me food for thought. I have a F6.3 reducer for the C9.25. So I might try that.

Thank you for the advice.

[Stu]

I would agree that a 32mm Plossl would give you the widest view, and less of a 'looking down a straw' view than the 40mm.

I suspect binoviewing might actually give a good result, something I will try soon hopefully.

I have read about people using 2" eyepieces without too much vignetting but in theory the baffle tube aperture is too small to allow 2" eyepieces to be used. I limit myself to 1.25", and understand that the scope is designed for higher powers and a narrow field of view. It works well on Smaller DSOs such as open and globular clusters, planetary nebulae etc.

[Mr Spock]

I used to have an OMC-140. I fitted the 2" back and that allowed me to use a 42mm LVW.  Worked just fine though a little restricted; I reckon I was getting about 1.2°

[John]

If you can find a used 35mm Celestron Ultima or 25mm Orion Ultrascopic (both now out of production) they would deliver just over a 1 degree true field with the OMC140. They are 1.25" eyepieces. Whether the additional .2 of a degree that moving to the 2" eyepiece size (and a diagonal to match) would give is questionable, perhaps ?

 

 

[PaulB]

Funny you should say that John

I have a 35mm Ultima and a 24mm Panoptic.  I can also use 2" eyepieces with this MCT. I have a TS 2" star diagonal and Baader 2" visual back.

I don't have any problems regards vignetting.

I think I will stick with what I've got. And wait for some clear skies, so I can use the OMC 140. Last time I did any visual observing. Was at KH last Autumn. That's how bad the weather has been.

I had some very good views through the eyepieces I have, at Kelling. But now we have Galaxy season. I want to use the OMC again. 

I will see how my 35mm and 24mm eps perform.