A 150mm F8 Dobsonian Eyepiece Conundrum

[MrJulius]

I have a Skywatcher Skyliner 150P Dobsonian on its way to me from Germany.

Previously I had an Skywatcher ED80 F7.5 which I now sold because I enjoy my visual observing and occasional planetary imaging more than the long exposure more tracking sensitive deep sky work.

I had an old black Heq5 Syntrek which I mostly used manually(i.e without power), and that was kind of hard to say the least considering it is not meant for manual work.

Also it had the black synta grease which freeze here in the cold winter nights of Norway. Enough of that

With the ED80 I sold a Skywatcher 28mm LET 2" eyepiece with 55 degrees apparent field of view. That provided me with a 22x magnification and a true field of view of 2.57 degrees.

I loved the view of the double cluster, that is the largest AFOV I have ever looked into

I also have Vixen NLV in 12mm, 9mm and 6mm which with the ED80 provided me with 50x, 67x and 100x and a true field of view of 1, 0.75 and 0.5 degrees.

With the 150P they provide 100x, 134x and 200x with a TFOV of 0.5, 0.38 and 0.23 degrees.

I enjoyed Jupiter at 100x last fall and could see both equatorial belts, although not in very much detail.

I now have a Skywatcher 2x ED Barlow, therefore my logic is that I can sell the Vixen NLV 6mm and just Barlow the 12mm. I am not sure if I will have any use for the 9mm either, with 2x it will give me 268x which sure must be to large magnification for any thing useful with a dob?

I have been on the lookout for a 2" eyepiece that will give me as low magnification and therefore large TFOV as possible with the 150P.

I have been considering the Moonfish 2" 30mm 80AFOV clone after seeing a good review in Sky at night. But I have heard many people recommending a smaller AFOV with better optical qualities than a large one.

At the end I have quoted the reply's I got in http://stargazerslounge.com/equipment-reviews/114787-ethos-13mm-first-light.html thread but I figured it is better to start a new one, than to threadjack Rob's thread.

Excellent review Rob

Could you comment a bit on the Moonfish 80 degrees field of view vs the Ethos 100? (As a kind of low cost alternative to the Ethos, maybe a bit of a stretch there ).

I was impressed by my Skywatcher 28mm LET 55 degrees eyepiece

With my ED80 it felt like the sky was around me, not trough a hole.

Well the moonfish 30mm has a good field of view and is clearly wider than the Hyperion, I find that theoff axis aberattions are quite severe. It's still a good eyepiece but I think the hyperions are better.

Thanks for the quick answer, looks like I have to take a look into the Hyperion series then.

Thanks again,

Julius

I've tried quite a few different eyepieces in my scope and the Moonfish 30mm I would put very close to the bottom. The aberattions were very bad, at least 40% of the FOV had seagulls, it was not a pretty sight.

I agree with Doc. I've tried various Hyperions and a Moonfish (or, more strictly speaking, a Moonfish clone). The Moonfish does have a nice wide FoV, but you really have to jam your eye into the eyepiece in quite an uncomfortable way to see the edges, and the distortion you find there is quite dramatic.

The SkyWatcher Aero eyepieces are well worth a look and they're not much more than the Hyperions. They're clones of the TMB Paragons and do perform well in faster scopes.

http://www.firstlightoptics.com/proddetail.php?prod=sw_aero_eyepiece John

[MrJulius]

I have been quoted £140 for The Skywatcher Panaview 38mm 70 AFOV eyepiece which I think is a bit to expensive. Wish I had a FLO in Norway

The Aero series is probably even more expensive here

I have also been looking at the William Optics SWAN 40mm 2" 70 AFOV eyepiece it costs just $118 directly from Taiwan, about £93 including Norwegian VAT .

That Eyepiece would yield a 30x magnification and a TFOV of 2.33 degrees and an exit pupil of 5mm.

I have heard of people who say they can see the secondary if you use to low magnification, do you think this eyepiece will work in the 150p F8?

[Moonshane]

I think that the WO SWANs would be a good choice for you. I had an f8 scope (refractor) and the 33mm SWAN I had was lovely in that. The exit pupil is the eyepiece focal length divided by the focal ratio of the scope so in your case 40 / 8 = 5mm, therefore in your case this would be fine. it's in the faster scopes the larger exit pupil CAN cause problems (eg an f5 would be 40/5 = 8mm which is wider than most people's pupil).

If I were you, I'd buy used off here if you can get people to post - if you cover the cost then I am sure they would.

you can get the 40mm SWANs for maybe £40 used.

[MrJulius]

Thanks for the input Moonshane. I will post an ad in the wanted section.

To confuse myself and others some more

I found an ad for a person selling a TeleVue Panoptic 22mm localy for about £80 here in Norway.

It is a 1.25" fitting and a AFOV 68. It will be about 55x and a 1.25 degrees TFOV.

Are the Panoptics as good as they seem? In comparison to the Swans? £90 locally seems like quite a bargain.

[Moonshane]

I'd be over there now and buy it. this is a wonderful eyepiece and that's a serious bargain.

if he has a 22mm Nagler T4 then pass me his details!

[MrJulius]

Still thinking

[MrJulius]

I am leaning towards an 11 or 9mm T6 Nagler because of the large AFOV.

It will provide 109x and 133x 0.71 and 0.59 degrees. The price is £120 which is quite good I think, the seller says they have had little use, like new.

Thanks again for the help

[John]

The T6 Naglers are excellent IMHO - I have 4 of them at the moment. If in nice condition, £120 is an excellent price - they generally go for around £140 used.

It's certainly nice to have the extra FoV while using a dob at high power I find and the T6's are very sharp and contrasty eyepieces, despite the number of lens elements in them.

[Matthew.Blake]

I use a 30mm Aero as my lower power eyepiece. I absolutley love it and if there is a way to make it affordable in Norway I'd go for it. It's my favourite eyepiece by far.

Matt

Spiese Flagamoose!

[MrJulius]

Thank you very much Moonshane, John and Matt

I ended up with the 9mm T6 Nagler.

And I am considering the Aero or Swan at about 40mm for use as a finder and of course for widefield.

[Moonshane]

great choice!!