LP + largest TFOV EP?

[Dunkster]

Folks... I've been getting to know my 20T5 with both the C11 and the 6SE and I'm really happy with it so far, but I'm wondering whether there's much use getting a longer FL EP for the C11.

Most of my viewing is done from home (so far), and while I aim to make more darker sky outings next season, I should probably assume that viewing with the home LP is a baseline. The 20T5 has been doing a great job with both scopes and I've fit almost everything I've aimed for in the FOV - bar the Coathanger and the Pleiades which I'm never squeezing down these tubes in one go anyway

So I guess what I'm asking your opinions on is whether it's worth investing in a longer FL EP for the C11 for what will be essentially occasional use, what with the need to go out of town darker for larger, fainter objects... all told, I know I'll be lucky to eek out 1 degree TFOV with it and I knew that going in, so really it's a cost/use balance. I'm sure the 31T5 or XW40 are great, but will probably get used rarely from here and are not inexpensive, so maybe a SW aero or ES68 would serve just as well at f/10 or is there a good rule of thumb to figure out what the useful magnification/FL is for a given (lack of) darkness?

[swamp thing]

That 20mm T5 is a beauty ain't it.

TBH if you don't think you'd use a lower power eyepiece very often then the aero types work well in slower scopes.

I must admit I seldom use my 31mm T5 in my 10" Dob as its so heavy and the power is just too low for most objects. Just occaisionally I use it on really big objects like the Rossette or NA neb, IMO it's really an eyepiece suited best for big fast scopes. It was a killer in my 16" and looking forward to using it in my 20" when finished.

Don't get me wrong it works extremely well in smaller scopes its just the weight of the thing (it's a tad portly).

[Dunkster]

It definitely is... I know they're both slow scopes but wow! Great with clusters in the 11... M13 I was not prepared for

The 31T5 or Pentax both get rave reviews, but with significant investment. I'm up for experimentation, and the 20T5 is a good - possibly too good - frame of reference, so it should be fun.

It's as much a question of balancing out FOV with contrast already compressed by LP

[alan potts]

Dunkster,

If I had my time again I would not. I have a LX 200 12 inch. I was one of the fools that bought the .63 reducer and a televue 41mm thinking I would be able to see behind me. I wanted a wide field of view. In the end I just bought a new telescope and mount. The most I get from my Lx 200 is about .92 Degree, you will get a little more. My advice is don't bother, for about the same outlay you can almost buy another scope.

Alan

[Moonshane]

Personally I agree with Alan. I think that overly wide FOV (not AFOV) is somewhat over-rated, especially if your main observing site suffers LP as mine (ours) does.

My target was 1 degree from my 16" dob and I get this comfortably with the 26mm Nagler I have (1.15 degrees). I rarely find myself wishing I had a wider field and when I do, for e.g. the Pleiades or Beehive I just look in the 9x50 finder! I'd probably think differently if I lived at a dark site or got to one more regularly though.

That said, I'd tend to buy e.g. a 6"/8" f5 newt/dob to get those wider views if I started to crave them (which would give me almost 3 degrees).

[Mr Spock]

For DSOs with my C9.25 I mostly use a 22mm T4 Nagler. At x107 it's just about perfect for most objects. For globulars and planetaries I go to the 17mm T4 at x138, or 13mm LVW at x181.

If I need to fit a cluster in, I use my 42mm LVW. That gives x56 and 1.29° - the widest my scope can go. I don't use it all that often though, I prefer a darker background.

[michael.h.f.wilkinson]

I love to use my 31T5 in my C8. True, as with Mr Spock, I do switch to the 22T4 often (it's my main galaxy-hunting EP), but the 31T5 is great. It gives a 3.1mm exit pupil, so LP is not the greatest of problems. In Virgo it gives breathtaking views of large groups of galaxies. I sometimes even switch to my old 40mm TMB Paragon, for the extra little bit of true FOV (1.34 deg vs 1.25 deg for the 31mm). This is used on just a few objects, or for public outreach, as the Paragon is easier to use for less experienced observers. The 31 gives a much darker background than the 40mm, which is why the 31mm is always the first in my scope.

[Dunkster]

Thanks folks, that's helped me think more clearly

The 31T5 sounds fantastic, but I'll hold off and see how it goes, I guess I was just getting cloud rage

I knew the C11 was never going wide, and to be honest it's been fantastic so far on clusters with the 20T5 at 140x... actually the combo has made me really enthusiastic about these objects after being a little disappointed with them in my C6 (I now feel it must have been a dodgy night as I've since had better luck with the 6+20T5).

I do also have the 23mm Axiom LX, but I tried using it to align my C11 using it on first light and was getting blackouts. I'll try it again when less rushed.

The sensible thing to do if it doesn't work out come nebula season would be to get a small portable Dob. But _then_ I'm sure it'll haunt me again

[alan potts]

Dunkster,

One thing you could do which in my LX 200 give the widest field. Buy a .63 reducer and use it with a 26-28mm SWA this give you a faction over 1 degree and don't vignet. You may even get away with a 30mm but I have never tried it. There is also the possibity that Naglers of the same size will work, I am sure 26mm will give you fine results but as for larger I simply don't know. I don't know how much of this gear you may already have but it is cheaper than a Nagler 31mm.

Alan

[Dunkster]

Thanks Alan - my C11 is the Edge HD variety so the FR is pricey, the Nagler would probably be cheaper LOL.

The C6+20T5 gives me in the region of 1.1 degrees (maybe less because of my 2" diagonal), it's just the difference in light grasp between the 2 OTAs is