20mm Nagler Vs 17 mm Ethos

[Chris Fleming]

I recently upgraded to a 12" lightbridge which has accentuated a gap in my EP range between my 13mm Nagler & 24mm Panoptic. To close the gap a bit I'm planning to replace the 24mm Pan with either a 20mm Nagler or a 17 mm Ethos ... Any recommendations or alternatives? My widest EP is a 30mm TMB Paragon.

[astro744]

The field stop diameter (which determines true field) for the 24mm Panoptic is 27mm. For the 20mm Nagler it is 27.4mm and for the 17mm Ethos it is 29.6mm. Both the eyepieces you are considering will give you a wider true field but at a higher power than the 24mm Panoptic with the 20mm Nagler being almost identical in true field to the 24mm Panoptic.

The 20mm T5 Nagler is a very nice alternative to the 24mm Panoptic but your combination of 24 Pan and 13mm Nagler is a good combo as it stands.

See http://www.televue.com/engine/TV3_page.asp?id=28 for Tele Vue field stop info.

However if you have light polluted skies then the smaller exit pupil of the 20mm Nagler and especially 17mm Ethos may be beneficial to you by giving you better contrast.

[astro744]

What have you got under 13mm?

A 9mm T6 Nagler will give you a good amount of power on globular clusters, planetary nebulae and planets and complements the 13mm T6 nicely. It will also give you near 2mm exit pupil which is ideal for DSO's and will allow you to pull in many faint galaxies.

[Chris Fleming]

Thanks for the feedback. I have an 8mm Burgess Planetary (60 deg) which I never use on DSOs but nothing in between. 9mm Nagler sounds like a great option. I don't have any tracking and at that magnification things move out of field quickly.

I've also been investigating the Explore Scientific range. They have a 9mm 100 deg which may be interesting. They also have a 20mm 100deg which may be a good alternative for a 20mm Nagler or 17mm Ethos. This would give the same FOV as my 30mm Burgess.

Any thoughts or experince with Explore Scientific range?

[JethroB76]

I recently got a 20mm T5, although I haven't had a great chance to evaluate it, its a very nice EP. Apart from the obvious FOV it doesn't lose out too much to the shorter fl Ethos EPs that I own.
With a 13 Ethos and the 20 T5, I don't see a need for anything in between - I had considered maybe getting the 17E but then decided on something in the ~20mm range (either 21E, 20ES or the 20-26 Nags), the 20T5 came up first at the right price so that is the way I went.
I nearly pulled the trigger on the 20ES at the start of the year but hesitated and missed a great price and have regretted it since :rolleyes:

[erick]

Here Chris:-

http://www.iceinspace.com.au/forum/showthread.php?t=45759

[Rodstar]

Hi Chris, my range is 31T5, 20T5, 13E and 9T6. I cannot imagine ever wanting to change. It is my ideal set. New designs come along, but for mine, the 20T5 is near perfection. It is a nice tidy size, much smaller that any other Nagler around that focal length, and certainly much smaller than the Ethos range. It is very sharp and contrasty, and at least at my focal length, perfectly frames most targets.

The only thing to be aware of with the 20T5 is the eye relief is a little tight when wearing glasses. I am a glasses wearer, but I prefer to take my glasses off to observe, so it is a non issue for me, not sure if that is a factor for you.

Good luck with choosing.