New eyepiece for 10" Dob

[JJ]

OK, so I'm a newbie and proud new owner of a 10-inch Dob from BinTel.
It came with a 2-inch 26mm wide-view eyepiece plus 15mm and 9mm 1.25-inch Plossls.
I want to add a high quality eyepiece to the kit with extra magnification.
I'm looking at a 5mm Nagler or a 6mm Ethos.

I've done as much research as I can. The magnification with the 5mm Nagler will be 250x versus 208x for the 6mm Ethos. I think I'd like to go for the higher magnification of the 5mm Nagler, despite the lesser AFOV. However, my research has me wondering if this will push the limits of the scope (too much magnification) for the given conditions (light pollution) of my location.

Factors to consider:
- The scope is 250mm x 1250mm (F5).
- Most viewing will be from my backyard in the Chelsea area (Melbourne metro).
- I'm in my late forties and, although I wear glasses for night-time driving, I don't need glasses when using the scope (eye-relief shouldn't be a big factor at present).
- I mainly want the extra magnification for better planetary views.

What NOT to consider:
Price. This is not a 'better value' question. This is a quality and viewing-pleasure question. I don't care if the eyepiece ends up costing as much as the scope itself!

Considering all of the above, am I too concerned?
Is there any real reason NOT to choose either? (If so, what other EP may be more practicable?)
Could I even consider more magnification? (e.g. a 3.7mm or 4.7mm Ethos SX with even greater AFOV.)

I humbly bow before those of greater experience and wisdom - which is anybody really!

Jason.

[barx1963]

Hi Jason
Congrats on the scope! THe thing with eyepieces is that more power is not always a good thing. My old scope was a 12" GSO (essentially the same as yours but more aperture and 1500mm focal length) and when I purchased a 10mm Ethos, which gave 150x, it was only marginally useable. I also had a 6mm Delos and it was even less so.
I found that on most nights 13mm giving 115x was about as far as I could push it. On bright objects the 10mm was OK, Jupiter looked fantastic, but for DSOs it was marginal. Unsteady seeing prevails most of the time and magnification makes that worse.
If it was me, I would look at a 13mm Nagler or Ethos, see how they go and then decide if you need more power.

Cheers

Malcolm

[JJ]

Thanks Malcolm, that's the kind of experience/advice I'm after.

[Hzadbhat]

Malcolm is spot on. Higher magnification is sometimes quite useless, even sometimes bad. I've got a 10" and usually don't go below a 10mm. I occasionally barlow this and many times, it suffers.
I'm personally looking in the 15 - 17mm range as well as something near to 25mm. In the future I'll be adding a 9-11. If money isn't a consideration, the ethos are the way to go.
The key to getting the best from ep's of this quality is darkness.
A drive of half an hour will amaze you in the difference, and if you get to a really dark site quickly (with your scope and these amazing ep's) you will know what I'm talking about. However, they will still blow your mind in your backyard. It's just, at a dark site, your mind is blown so, so much further.
I've looked through my scope with a series of serious ep's and would definately go the ethos if I could justify spending the cash today.
Within 6 months or so, I'll have them anyway.

[dannat]

there is a 8mm ethos in the classifieds here, which will give a good medium power for planets & luna - & be usable on nights of good seeing for deep sky objects

i have a smaller scope but i like about 120x for dso (like malcolm) & around 200x on planets (my smaller scope cools quickly)

imo the 5mm angler will be too high a mag on most nights, the 6mm would be used more often

[JJ]

Thanks for the input Brandon and Daniel. Every bit of perspective helps.

In my researches I'd noticed that Tele Vue's website suggests an 8mm Ethos or 7mm Nagler as the high-power EP for a 6"-10" Dob. I guess that assumes good seeing conditions. Nonetheless, I've been pretty impressed with the views of Jupiter and Saturn I've been getting with my 9mm Plossl from the backyard. Given that I'm close to the beach and therefore not smack bang in the middle of a built-up area, perhaps the light pollution where I am isn't as bad as elsewhere.

So my rationale has been, if I'm getting pretty decent views with a standard Bintel 9mm plossl, surely I can go for more magnification with far superior optics. Obviously there's a limit to this trade-off, but I want to push it as far as I can.

Hmmm, do I go for the 6mm or 8mm Ethos .... (!)

[omegacrux]

Hi Jason
I have a 10in Dob Il second what the others have said
My 6mm TMB doesn't get used much , its good on Jupiter , but it scoots out of the ep fast !

David

[JJ]

Thanks David - more food for thought.
I guess it'll come down to whether I'm prepared to spend a lot of money just for the best planetary views I can get and be prepared to spend more again down the track on another eyepiece for DSO's. Then again, an 8mm Ethos just may be the sweet spot.

[Satchmo]

I would recommend a 5mm Nagler type 6. If its primarily going to be a lunar and planetary eyepiece its not justified spending double that on a super wide field and 82 degree is very respectable. Ethos's are great at wide field but do not necessarily do any better than other eyepieces on axis which is where you'd be using it.

Whether you can use a 5mm eyepiece giving 25X per inch depends on the quality of your mirror , how good your collimation is and how steady your skies are at home. You may get a better performance gain spending money on a high quality barlowed laser and a Nagler rather than buying a really expensive eyepiece.

In the time I had a tracking drive on my 14" I found that I saw a vast amount more planetary detail. Again, if you don't have tracking I would question the point of investing too much in a high power eyepiece.

Hope this helps.

[JJ]

I've just re-read everyone's replies - particularly Malcolm's initial response. I think I need to spend more time comparing the views of my 9mm and 15mm plossls on some DSO's, especially as I haven't used the 15mm anywhere near as much as the 9mm. This will no doubt help balance my perspective on the issue a little more.

Thanks again one and all.

EDIT: Cheers Mark - the 5mm Nagler type 6 was one of my early considerations for just that reason, and yes - every little bit helps.