Pentax 7mm XW / Vixen 8mm LVW

[iceman]

hrmm, been looking out for an series 4000 8.8 Meade UWA for months now.. the one I found (and bought off astromart) subsequently didn't turn up :( Lost in the post :( Also been looking for a 6.7mm of the same ilk, but I haven't seen one come up.

So, I'm starting to look for something else now.. after selling the 22Pan that I didn't really like, and then winning a 22mm Vixen LVW, I have some funds to purchase my high-mag DSO/low-mag planetary eyepiece.

Anyone have any opinions on the Pentax 7mm XW vs the Vixen 8mm LVW? Apart from cost ($450+ vs $345), what other differences are there? The both have similar FOV and eye relief.

I've looked through John Bambury's 7mm Pentax XW many times and it's without a doubt a very fine eyepiece. I've yet to look through a Vixen LVW.

It's also worth throwing into the equation a Nagler 7mm T6 as well I guess - how does it stack up vs these two?

I was going to get a 7 and 9mm UO HD Ortho, but I can't get past the allure of the premium widefields for some reason :doh:

Opinions please.

[davidpretorius]

i love my lv 5mm, i do still have the odd glare fairy so to speak. I have not looked through a wide view LVW, sorry, it is all i can add to this thread.

what happens when you don't take delivery, do you get your money back? what a pain in the butt!

[janoskiss]

I've compared the 8mm LVW to the 8mm Stratus and they were very similar (but the LVW is slightly better in every aspect). Fair bit of false colour off axis would be my main concern with that EP (and not just at the very edge). For DSOs the EP performs very well. The false colour is an issue on Moon and planets. I've never looked through an XW.

[Starkler]

As you have the same scope as I , my opinion is that a 7 or 8mm eyepiece isnt short enough to get to a good planetary magnification. I have a 7mm ortho that I would gladly trade for a 6mm.

IMO the ideal workhorse planetary ep would be a 6mm, but there are very few sold at this focal length other than the TV Radian.
When the TMB/Burgess 6mm becomes available I plan to buy one.

[iceman]

I didn't choose insured or registered post, so I forfeit my money. But lucky for me on this occassion, the seller was a fantastic guy and offered to pay me half back.. I tried to convince him not to, but he insisted. Wonderful guy.


I've got the 4.7mm Meade UWA for high mag planetary, and it's doing a great job for that purpose. Ideally i'm after something at the 7mm/8mm and then the 9mm/10mm range, to give me enough range at that high power.

The 2 eyepieces in the subject wouldn't solely be used for moon/planets, they'd mainly be used for high power DSO, as a step up from the 14mm UWA when higher power is needed. Though of course I'd use them on planets when the seeing isn't good enough to support 265x (in the 4.7mm). And i've seen from using John's Pentax that it does a good job on planets. I don't expect either of them to be very good on the moon, i'd probably look at getting a 6mm UO HD for the moon/planets.

I wonder when Dave47's getting his 8mm Vixen LVW? I'm very interested to hear his impressions, though the scope he's planning to use it in is significantly different :) You need to test it for me in your scope, Geoff!

Steve, who's LVW8 did you try? And in what scope?

[acropolite]

MIke, The EP may still turn up, I ordered a DVD from South Africa in November last year, it didn't arrive until mid march. Where it went in the meantime is anyones guess, but 3 1/2 months later there it was.

[iceman]

Yeh i'm hoping it came seamail instead of airmail, in which case it might still turn up. But i'm certainly not expecting it to.

[janoskiss]

Cameron's (castor) and Daniel's (danielsun). Both times in an ED80 mostly, and only very briefly in an f/5 Dob. The Stratus I used in my f/6 Dob for a while as well.

[ausastronomer]

Geoff/Mike,

I have the 7mm and 10mm Pentax XW's and 5,6,7 and 9mm UO HD orthos as my native high power eyepieces. I also have the 2.5X Powermate and sometimes barlow the 14mm Pentax XW in the Powermate for an effective 5.6mm focal length. You really need both a 6mm and the 7mm because of variable seeing and if you can afford it you also need a 5mm for nights of very good seeing. I have many nights where the 5mm or the 6mm will not hold up and you need to drop back to the 7mm, particularly on Jupiter and Saturn. If I was only able to have 1 eyepiece in this focal length range it would be 7mm. 8mm is too short a focal length IMO for planetary work in this scope. The 8mm Vixen LVW is a great eyepiece but you really need a 7mm focal length IMO. The 7mm also does on excellent job for high power work on DSO's. I often stick the 7mm Pentax XW in the scope with my Astronomiks OIII filter and then use Argo to tour planetary nebula. Excellent combo all round for this. Also a great combo to go deep on globular clusters (without a filter of course).

Something else to consider are the Williams Optics UWAN. I have discussed these with Tom Trussock and he rates these very similar to and almost as good as the Nagler T6's at about 70% of the price. So they are definately something to consider (I know Naglers row your boat).

If you are not critical about having an 82 deg AFOV nor worried about the extra size and weight of the 7mm Pentax XW, it is the best eyepiece optically, in this focal length range that I have used and I have used just about all of them. Remember that Comfort (eye relief), Sharpness, Contrast, High Light Transmission and cool colour reproduction are important factors to me in rating eyepiece performance, they may not be so important to you.

CS-John B

[Dave47tuc]

My LVW 8 mm is arriving late next week hopefully. I will gladly let Geoff use it for you. But when!! Who knows this time of year?
But I think as others have said you need a 6 mm or 5 mm. I only thought you would like an 8.8 mm to match your 14 mm.
If it’s just a planetary eyepiece you are after then I think you need 6 or 5 mm as I said.
I have spoken to a few people who know about eyepieces and who have been observing for a long time. They had no hesitation recommending the 8mm LVW to me.
For me the 7 mm was a bit too much magnification. But this would be the opposite for you.
What about a 6 mm Radian?:shrug:

[Starkler]

My planetary workhorse combo is a 14mm XL in my Ultima barlow.
The barlow gives an effective mag boost of 2.2x giving effectively a 6.36mm eyepiece and 196x mag.
As I mentioned I also own a 7mm ortho which I feel isnt enough magnification.
If I cant get a pleasing view at 196x, I wont bother looking at planets as IMO there isnt worthwhile detail to be seen. I just mention this as I dont think its worthwhile to sink the big eyepiece dollars into a lower planetary magnification. :shrug:

[iceman]

As I said, it's not specifically for planetary. I've got my 4.7mm for that, and I will probably get a 6/7mm UO HD Ortho as my "other" planetary eyepiece.

The 7/8mm pentax/vixen will be higher power DSO's.

I do still want the 6.7/8.8 s4000 UWA's, but I can't find any so i'm not going to go without forever, in the lost hope of eventually finding one.

[Dave47tuc]

Well either will do you well. Toss a coin :D

If it was me and I'm not you! With your scope the Pentax would be my choice. If it was me and my Mak, the LVW would be the go:whistle:

:)

[iceman]

I decided (http://www.iceinspace.com.au/forum/showthread.php?t=9152) on a 7mm Pentax XW - bought it today.

I'll probably get a 6mm Vixen LV or UO HD Ortho to fill the gap for planetary/lunar observing.