PDA

View Full Version here: : Advice sought - 8mm Eyepiece


Lismore Bloke
16-09-2009, 02:47 PM
I want to complete the eyepiece collection in the near future. I already have the TV 22 and TV12 Naglers. The 17mm will join them.

I am not sure about the 8mm. Tack sharp images to the edge and
generous eye relief are more important than 82 degrees of field.

A 2" barrel would be nice, I would only need one filter!! I am not sure if any eyepieces in this length have this feature. I rather like the LVW and
Pentax for sharpness. Thanks, Paul.

astro744
16-09-2009, 03:27 PM
Ethos 8mm is 1.25'/2". An EBX-2120 barrel extension allows the use of a 2" filter
.
Radian 8mm is 1.25" only but you can leave a permanent 2"-1.25" adaptor on the eyepiece.

16mm T5 Nagler with 2x Powermate is 8mm and 2" but not as much eye relief.

32mm Plossl with 4x Powermate gives plenty of eye relief and a big eye lens and is 8mm and 2" barrel.

40mm Plossl with 5x Powermate gives plenty of eye relief and a big eye lens and is 8mm but 1.25" barrel.

31mm Nagler with 4x Powermate gives plenty of eye relief and a big eye lens but is 7.75mm. (2")

35mm Panoptic with 4x Powermate gives plenty of eye relief and a big eye lens but is 8.75mm. (2")

Plenty to choose from, depends on how much you want to pay. The tack sharp to the edge is what you are paying for.

Waxing_Gibbous
16-09-2009, 04:16 PM
L.B.
The Vixen LVW 8mm (65degrees FOV, 20mm eye relief) is a scorcher, especially in fast scopes. Some minor ghosting on very bright stars.

If you're not fussed about a degree or so, the Takahashi HiLE 7.5 (52 degree FOV, but only 10mm eye relief) is sharp as any eyepiece I've seen.

The Pentax SMC-XL 7 (65 FOV, 20mm ER) is, well, almost perfect. No CA, no pincushioning or barrel distortion.

Second Astro744's coments on the 16mm Nagler. A really useful combo.

These are eyepieces I've either owned or used. Can't comment on others.
BOL.
PJH

dannat
16-09-2009, 04:23 PM
there was a WO uwan 7mm in the ice trade

GrahamL
17-09-2009, 05:39 AM
Try my 8.5 xf paul its got most of what your after and is surprisingly cheap .
Sold on a 7mm nagler to get this one as I think this magnification gets a lot more
use with our skys .

Most 2"/1.25" adapters are threaded underneath for 2 " filters
been using my 2 " filters on my 14 xw switching to 22t4 for ages without any dramas.

cheers graham

Lismore Bloke
17-09-2009, 06:58 AM
Thanks to everyone for their replies.

GRAHAM -
Thanks, we must get together for an observing session! I like the sound of the Pentaxes, with their sharpness and eye relief. The Radian and LVW are the other favourites. Where did you get the adaptor? There is a Televue adaptor around, but no filter thread. If I am to get a good filter, Lumicon or Astronomik, I only want to pay for one!!! I will phone Bintel and ask about using the Radian in a 2" barrel threaded for filter, if it is possible.

PETER,
Do you have the LVW? If so, is it a 2"?. Thanks, Paul.

Waxing_Gibbous
17-09-2009, 08:03 AM
LB,
No, its only a 1.25". Its pretty hard to find high power EP's with 2' barrels. Does your diagonal have filter thread? If not consider getting one that does, that way yhere's minimal faff.
Als all the EP's I've mentioned I no longer own, tho I'm planning to splash out on the Pentax come pay-day!

GrahamL
17-09-2009, 04:00 PM
bintel got em paul ;)
under telescope acceseries




drop me a line when your free

erick
17-09-2009, 04:09 PM
Be careful. A few 1.25" eyepieces have barrels long enough to hit a 2" filter screwed into a GSO 2"-->1.25" adapter. I recall that some GSO plossls would do this. I recommend that you check carefully in daylight with the eyepieces you plan to use this way.

Lismore Bloke
18-09-2009, 02:44 PM
Thanks, Eric. I notice that Televue do not include filter threads on their adaptors, just in case someone slides a great long barlow or similar into the adaptor and crunches an expensive filter.

erick
18-09-2009, 03:16 PM
Yes, my 1.25" TV 3x barlow would leave an impression on a filter! Hadn't thought of that! :help:

Lismore Bloke
18-09-2009, 06:48 PM
I phoned Bintel to check on fitting a 1.25 eyepiece with a sleeve for 2". They didn't know, but took my number and phoned back in 5 minutes. Yes you can fit a $19 Bintel 1.25 to 2" adaptor to a 8mm Radian and fit a 2" filter on the end without the eyepiece hitting the filter, just as Graham suggested in his post. As long as you keep the long nosed barlows away. Good answer!! Just another example of their great service. The Bintel boys were all getting primed up to drive 3 hours to a dark sky site and observe until 3 am. Good stuff.