which ep for a 150mm newtonian?

[Rob]

OK here goes my first posting on IIS! I am effectively a beginner as I am just returning to astronomy after a very long break. I bought a 150mm f5 bintel newtonian on an eq mount in December. (Bintel have been great BTW), and have been slowly getting used to it, learning to collimate etc. IIS has been a great help, I have been lurking extensively.

The scope came with gso plossl EPs. I have been resisting the urge to spend $ on a premium high power ep, but I think it's time to take the plunge. I'm tossing up between an 8mm radian and a 7mm nagler. In either case I would buy second hand when one comes up. What's stopping me is I'm not sure what magnification will work for my conditions. With a 2x barlow (I bought an orion shorty), the 8mm will give me 188x and the 7mm will give me 214x. Bintel suggested going with 8mm as atmospheric conditions in Wollongong might not support the higher magnification. But this seems a bit conservative and I am very tempted to push it to the 7mm. Mostly I observe in my back yard with suburban skies (not terribly light polluted but not great either). Occasionally I get to a field night with dark skies, and 2 or 3 times a year we visit my girlfriend's parents in western NSW with very dark skies.

Any suggestions on these or other EPs I should consider? Thanks for reading my long winded story.

Cheers,
Rob

[janoskiss (Steve H)]

The advice you got from Bintel is correct IMO. The barlowed 7mm will be much less useful than the 8mm. On planets and DSOs, the image will be quite dim even in good seeing and you will probably very rarely use it unless you have some special reason to need high magnifications (you're into splitting close doubles perhaps??).

[ving (David)]

first up i'd like to offer kyou a huge welcome!

ok now t you r question.... i'd go the 8mm cause it gives you extra eyerrelief and would be more comfortable to use.
in my f6 8" the max i tend to use is a 7.5mm. this gives me 160x. in average to above average this is as high as i'd go. i have a 6.5mm which gives me about 182x and i use this only when the seeing is good.... under exeptional seeing i'd barlow my 10.5 (@ 228x) and this is about the max i'd go on a planet.... double stars are another thing entirely.

[rmcpb (Rob)]

In my 8" f6 the most commonly used "high" power lense would be the 9.7mm (123x) so I would add a vote for the 8mm (94x) in your scope. I use other shorter lenses only when conditions allow and commonly on the moon but most other objects cannot often support the extra magnification.

As for the choice of expensive wide angle lenses, that may need consideration as you have tracking with your GEM so maybe a good plossl lense is all you need. This would allow you to get some good lenses at considerably less money than the wide angle options.

[Rob]

Thanks for the advice and welcome. I'll be keeping my eye on astromart for a second hand 8mm radian!

Cheers,
Rob

[janoskiss (Steve H)]

A new 8.5mm Pentax XF would be less expensive than a 2nd hand Radian, and probably just as good (same FOV, plenty of eye relief, same coatings as the XWs). I'm very happy with mine.