Eyepieces for fast scope?

[turboscrew]

I have a 300 mm / 1200 mm (F/4) scope, and I wonder what kind of eyepieces would be good for higher powers (<= 10 mm)?

I've heard that Plössls are good, but there doesn't seem to be a lot of them around with focal length of 2 mm to 5 mm.

What kind of eyepieces are "planetary eyepieces"?

 

[Rob_UK_SE]

Shorter plossls have very tight eye relief which is less (in mm) than their focal length. An 8mm plossl might have 6mm of eye relief, for example. Classic designs, such as plossls and orthos, can provide excellent views, but tend to have a 50 degrees field of view or less. Combined with their tighter eye relief, you may not find them particularly comfortable in their shorter focal lengths and, for this reason, they are not necessarily well suited to telescopes on manual mounts (although many experienced astronomers do use them in this way for specific applications). 

Planetary eyepieces is a more generic description for an eyepiece that has excellent contrast, minimal light scatter and sharp optics across the full FOV. They are often more simple designs (with less lens components) that may assist improved light transmission too. I say ‘may’ because the recent advancements in eyepiece designs have resulted in some very superb examples which are all of the above, while having wider fields of view and being comfortable to use too. However, some planetary observers very much prefer a narrower FOV to frame a planet / the moon as well as the previously mentioned characteristics of orthos and plossls. We are fortunate to live in a time where many options are now available to us in the astro community. 😀

Could you, perhaps, share a little more detail of your eyepiece preferences so that we can offer more specific ideas of which eyepiece/s might work well for you.  For example:

Do you prefer wider/narrow fields of view? Do you need more eye relief to assisting observing while wearing glasses? Do you have a specific budget?

 

Edited September 1, 2020 by Rob_UK_SE

[turboscrew]

I could start from the fact that I did buy a 3.6 mm MA - very bad idea. My budget... well, rather less than 200€ per piece.

I'm a beginner from Finland, and I got my tube in the beginning of June = not much experience. I think it has been darker than civil twilight for about a month now...

Those more powerful eyepieces are mostly for planetary. I guess it's enough for me if the eyepieces work, and are not very hard to use (like 0.5 mm eye relief 😄 ). I think about 50° AFOV is good.

BTW, which is usually better? A 3 mm eyepiece or 9 mm eyepiece with 3xBarlow?

 

 

[vlaiv]

Low budget option - very good range of focal lengths available:

https://www.teleskop-express.de/shop/product_info.php/info/p154_TS-Optics-7-mm-Planetary-HR---1-25--Eyepiece--58---fully-multi-coated.html

High performance but narrow field of view (not good if your scope does not have tracking mount - you need to nudge it more frequently and that distracts from viewing), also plenty of eye relief:

https://www.firstlightoptics.com/vixen-eyepieces/vixen-slv-eyepieces.html

Excellent performers with wide field:

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-82-degree-series-eyepieces.html

There are only a few focal lengths available like 4.7mm, 6.7mm and 8.8mm that could be considered planetary on fast scope. Maybe think of adding telecentric lens like this one:

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

x2 1.25" version (you won't need 2" version nor more power).

In fact, in most cases you won't need over x200 power, which you can get with 6mm eyepiece. Atmosphere is limiting factor. I always prefer single eyepiece vs barlow + eyepiece, but sometimes people find barlow + eyepiece sharper and easier to use.

If you want the best planetary performance (at a cost), have look at perhaps these (they are 50% over your top budget per piece):

https://www.firstlightoptics.com/tele-vue-eyepieces/tele-vue-delite-62-degree-eyepieces.html

[RT65CB-SWL]

@turboscrew... according to FLO, the BST StarGuiders https://www.firstlightoptics.com/bst-starguider-eyepieces.html say they are OK at f5, though whether f4 is/maybe pushing the 'scope to the limits. Many satisfied SGL'ers use them. I was thinking on the lines of wider FOV, your budget, eye-relief, etc. Orthoscopic's are good for planetary observation, but the FOV is usually <50deg.

[fifeskies]

A 6mm eyepiece will give you x200 with your 300mm scope , this is a high magnification for most days given the turbulent atmosphere on this planet.

Your in Finland I see so probably have superior air quality, you may be able to push to x300 on a good night. This would equate to a 4mm eyepiece.

Decent eye relief is important and many sub 10mm eyepieces begin to struggle in that respect.

for 200euros you can pick up a very good quality eyepiece 2nd hand.

 

Delos eyepieces have 20mm eye relief even at the sub 10mm range, and I use these with my 254mm scope, quality is excellent , clear over the whole view and high contrast. I bought mine 2nd hand for around the 200euro mark.

I have a 10mm for planets (which gives me x158 in my long tube scope). Jupiter and Saturn very clear at this magnification. When 2x barlowed to x316 the view if often mushier as the atmosphere in UK is just too erratic at that magnification 95% of the time in UK. They look far better at x158.

 

 

With conditions for very high magnification being rare I would suggest you go for something around a very usable 8mm giving x150 which will be fine in most viewing conditions and not only on planets.

You can 2x barlow it to x300 when atmospheric conditions permit.

Or a 6mm for x200 , (which x2 barlows to an unlikely x 400)

Edited September 1, 2020 by fifeskies

[Rob_UK_SE]

As your telescope has a focal ratio of f4 it might be less forgiving of certain eyepieces. In terms of of your budget:

top end: Baader Morpheus 6.5mm (185x magnification) and 4.5mm (276x). https://www.firstlightoptics.com/baader-planetarium/baader-morpheus-76-degree-wide-field-eyepieces.html . The 6.5mm would be a good all rounder for all plenary and lunar observations; The 4.5mm would be useful for the moon and Mars and, perhaps, Saturn in really good seeing. As well as good optics, both of these eyepieces have a wider field of view (76 degrees) which can be useful for manual scopes.

middle: Vixen SLV 9mm (133x) and 6mm (200x) have good eye relief, very good correction and are useful focal lengths. The 9mm has a 50 degrees FoV; the 6mm has 45 degrees. https://www.firstlightoptics.com/vixen-eyepieces/vixen-slv-eyepieces.html

lower: 8mm (150x) and 5mm (240x) BST starguiders, Baader classic 6mm ortho (200x) or OVL Nirvana 7mm (171x) are all worth exploring.  https://www.firstlightoptics.com/bst-starguider-eyepieces.html

https://www.firstlightoptics.com/ovl-eyepieces/ovl-nirvana-es-uwa-82-ultrawide-eyepieces.html

If you are prepared to ‘blow the budget‘, the 7mm (171x) Tele Vue Delite is one of the best planetary eyepieces I have experienced and is also very comfortable to use. https://www.firstlightoptics.com/tele-vue-eyepieces/tele-vue-delite-62-degree-eyepieces.html

Edited September 1, 2020 by Rob_UK_SE

[turboscrew]

Thanks, guys. Now I need to ponder. I'll go through the suggestions probably several times.

 

[Louis D]

I've read that the Takahashi TOE and Vixen HR lines also do well at faster f-ratios.  They have decent eye relief, but somewhat narrow fields of view.  However, they are rated among the best planetary eyepieces ever made including the ZAOs, TMB monos, and Pentax SMCs, XPs, and XOs.

If you want the Vixen HRs, you'd better hurry as existing stock is quickly being depleted since Vixen hasn't made a new production run in a while and may not again.