Quick EP Question

OldOz (John) · #1 08-03-2017, 04:31 PM

Coming back into Astronomy - after 25+y!
Certainly an impressive amount of change - particularly in astrophotography (not really my thing, but awesome advances with CCDs/stacking etc).
Following advice here, and on Reddit subs, have opted for a Collapsible 8" Dobson initially. My next step is a more useful planetary EP: would a) Baader 5mm (with FT rings, and various focal configurations) be better than b) Williams Optics 4mm (fixed focus, but 82° FOV). Or something else?
As both roughly the same price (and about my budget limit), any input would be greatly appreciated

gaseous (Patrick) · #2 08-03-2017, 09:41 PM

Hi John, and welcome (back!) I can't comment on any quality differences between the two eyepieces in question, but in my 8" collapsible dob even a 6mm EP is starting to push the limit on planetary viewing in a suburban setting with a 200x magnification. I've tried higher than that, but any increase in magnification is more than offset by some pretty unappealing blurriness. If you can get yourself to a dark site the seeing might be OK with a 4mm, but I'd have my doubts, and even the 5mm might be losing too much clarity. Just my $0.02 worth. Good luck.

OldOz (John) · #3 08-03-2017, 11:12 PM

Thanks for the input, Patrick.
Am right on the city outskirts, so find I can just use our basic 10mm Plossl with an (even more basic) x2 Barlow - on good nights, anyway. Hoping to build another EQ platform, but in the interim thought I'd get a slight improvement in clarity, and a certain improvment in FOV/eye relief with something better?
Guess my question is really if the 5mm Williams 82° FoV beats the likely usefulness of the Baader 5mm (+4mm +25mm options) 68°. Or, as you seem to suggest, perhaps a gold-line 66° 6mm would be far more sensible, at 1/10 the price!
Again, many thanks - John
http://www.iceinspace.com.au/vbiis/i...ttons/edit.gif

SkyWatch (Dean) · #4 08-03-2017, 11:13 PM

Hi John,
I agree with Patrick. You want to look for a planetary eyepiece that gives around 200x. If your scope is f6, then this would be a 6mm, with an exit pupil of 1mm. You would rarely be able to go higher than that because of atmospheric conditions, and 200x is enough to enable you to see a lot of detail, especially on Jupiter and Saturn.
I would suggest you look at the Long Perng "planetary" series if possible. Andrews have them listed for $99, but the 6mm is shown as "sold out", so I would ask them if they are getting them in. The Orion "edge-on planetary" and Williams "super planetary" series are, I believe, identical to the Long Perng, but more expensive (although cheaper than the ones you have mentioned). They all have a very nice 20mm eyerelief, 55 degree fov, and are very sharp.
Another very good planetary eyepiece would be the Vixen SLV6 Lanthanum. A bit more expensive than the Orions, but excellent reviews, and again a 20mm eyerelief.
The classic eyepieces for planetary work are the orthoscopics, but they have narrow fov and very limited eye relief at that fl. They are very difficult if you wear glasses. Astronomy and Electronics Centre stock the Fujiyama Orthoscopics. They all have 42degree fov, and the 6mm has only 4.9mm eyerelief. Although if you want the sharpest and highest contrast views, they are arguably as good as you can get, especially for $115.

All the best, and enjoy your "re-start" in astronomy!

- Dean

(PS: the only reason I would look at the 4 or 5mm 68-degree or 82-degree FOV's that you mention is so I don't have to push my scope quite so often, but they are a lot of money for that convenience if you aren't going to be able to use them often because of atmospheric conditions, and I suspect neither would be as sharp as the ones above...)

OldOz (John) · #5 08-03-2017, 11:35 PM

Appreciate your thoughts too, Dean.
My interest in a wider FoV surely is the need for accurate - and frequent - nudging of the dob (and image) at <10mm even with milk bottle mods (and pending the EQ platform). Got a fair bit less co-ordinated in those missing 25y!
I was certainly pretty keen on the Long Perng, and will certainly follow up that suggestion. Perhaps the best answer may be to finish the EQ first, which would open the field considerably?
Many thanks - john

AEAJR (Ed) · #6 05-04-2017, 05:03 AM

If you have not purchased yet, you may want to look at the Explore Scientific 68 or 82 degree line. They are on sale for the month of April. I have the 8.8 and 6.7 for use in my 3 scopes and find them excellent. They also have a 4.7 mm 82 degree.

dannat (Daniel) · #7 05-04-2017, 08:07 AM

the edge of the baader won't be great in a newtonian--its heavy also

AEAJR (Ed) · #8 05-04-2017, 09:26 AM

Compared to what? Looks pretty good in my F5.9 8".

Weight does not seem to be a problem for me. I have much heavier eyepieces than this.

glend (Glen) · #9 05-04-2017, 09:35 AM

John, the problem with 4 & 5 mm eyepieces in general is that you will rarely be able to use them. The problem is 'Seeing' conditions usually do not suit these high powered EPs. If you lived out inland at a dark site with really good Seeing, then they might be useful. But your in Brisbane, and i doubt you could ever get a great image out of them there. For most folks a good 9mm EP, like a Televue Nagler is a better investment. You can use it in most conditions and if you ever do run into anazing Seeing you can stick on a 2x barlow to take it to 4,5mm power.

N1 (Mirko) · #10 05-04-2017, 10:08 AM

I agree a decent 2x barlow might be best in the OP's situation, in combination with a good 8-12mm EP.
No need for a dark site to get good seeing though - just one with little air turbulence.

dannat (Daniel) · #11 05-04-2017, 10:09 AM

the 8mm bst explorer [at paradigm] is a good afffordable eyepiece [150x mag usable most nghts]

how much are you looking at spending?

maybe look for a 7mm [171x mag] in city i find its hard to go past this on most nigths

AEAJR (Ed) · #12 24-04-2017, 02:41 PM

Quote:

Originally Posted by glend

John, the problem with 4 & 5 mm eyepieces in general is that you will rarely be able to use them. The problem is 'Seeing' conditions usually do not suit these high powered EPs. If you lived out inland at a dark site with really good Seeing, then they might be useful. But your in Brisbane, and i doubt you could ever get a great image out of them there. For most folks a good 9mm EP, like a Televue Nagler is a better investment. You can use it in most conditions and if you ever do run into anazing Seeing you can stick on a 2x barlow to take it to 4,5mm power.

I use my zoom eyepiece most of the time. In my Orion XT8i that would be my Baader Hyperion 8-24. Excellent eyepiece. Gives me 50 to 150X and everything between. Drop in a 2X barlow and I have 100 to 300X.

I am in the USA, New York City area, so my conditions may be different from yours. I do most of my observing under 200X and the seeing will rarely support over 250X.

In addition to the Zoom I also have Explore Scientific 82 8.8, 6.7 and a Meade 5000 82 degree 5.5. All excellent.

I have a 4.5 but rarely use it at 266X.