Yet another 'please vindicate my choice of eyepiece' thread

[Jimtheslim]

Watching the GRS transit last night, some fleeting decent conditions meant that for the first time I could definitely pick it out with my 6.4mm (154x mag), however the image was far from sharp. The view through my 12.4mm was, however the GRS was just about impossible to make out, ergo I was looking to buy a decent plossl that would sit in the middle of these.

I was thinking something around 8mm. I currently have a 90mm f/10 frac, but looking to buy a 10" dob in the near future. I know these bigger, faster scopes are less forgiving on eyepieces so you have to pick them well. So far I have looked at and considered an 8mm vixen or possibly a Baader Hyperion 8mm or possibly a Celestron E-xcel LX. Anyone else want to chuck some suggestions in? [insert standard response about used televues here]. Budget wise it depends on my capricious mood swings, but looking to go second hand if I can.

Talk to me people.

[ronin]

First is that the X-Cels LX's do not come in 8mm, they are 7mm or 9mm. Small point but you ask about 8mm, I suppose the 9mm would be the one in the X-Cel's. Somewhere around the £60 mark I believe.

BST's come in 8mm, it seems to get about the highest comments of all of them so that is worth considering, £49.

TV plossls come in 8mm but if used then you have the "problem" of one appearing on the market and then you have to be the one that gets it. That is the problem of a used item.

As an additional to the X-Cel length, 9mm, there are the Altair Lightwave eyepieces, they do a 6mm and a 9mm. The eyepieces look and are specified identical to the William Optics Planetary's. If you decided on a 9mm first check Tring and Rother Valley out as they seem to have them for £45, Altair have them at £55. Also check the postage, sometime this is a significant additional cost.

Someone somewhere has the "old" Orion ED 2 eyepieces, minor problem is I cannot recall who and neither the cost - not much help I suppose - but you may find them in a search.

They are the sort of common not horriably costly ones I can think of.

[billyharris72]

One question that comes to mind is if you're absolutely sure the seeing was up to it. I would think a 90mm frac should be able to handle that magnification without too much degradation of sharpness. Also, could there have been anything (e.g. oil from fingers or eyelashes) on the eyepiece, or a bit of fogging? Can be harder to tell with small eyepieces and would make a big difference.

As for something between the two focal lengths, I have an Ex-Cel (9mm) and I like it. It does suffer a little from glare on Jupiter, but mainly if used with a Barlow, and it does not affect the ability to observe. Another option if your scope is equatorially mounted would be an ortho. The Astro Hutech ones give a lovely crisp image; the field of view is narrow (40-something degrees) but for planetary observing that is less of an issue with an EQ mount.

[Knighty2112]

I was observing Jupiter last night, and the seeing (when the clouds cleared) was average to poor. During very brief clear spells I could make out the GRS, plus Io's shadow too. Was viewing through my ST120 frac, using a 4.5 mm TMB Planetary II EP, so magnification was x133. Couldn't get any higher than this. A few nights ago up in Scotland, the view of Jupiter was much better, and the same EP showed details much sharper and crisper. One thing I use to bring out details better on Jupiter is a blue filter. Maybe be worth getting an 80A blue filter to see if you can tease out better detail from Jupiter, and can be used also on the moon also, as well as a few other planets too. 365 Astronomy does a filter for £12.90 plus p&p, which won't break the bank.

http://www.365astronomy.com/Castell-80A-Blue-Planetary-Filter-30-Transmission.html

[Jimtheslim]

26 minutes ago, billyharris72 said:

One question that comes to mind is if you're absolutely sure the seeing was up to it. I would think a 90mm frac should be able to handle that magnification without too much degradation of sharpness. Also, could there have been anything (e.g. oil from fingers or eyelashes) on the eyepiece, or a bit of fogging? Can be harder to tell with small eyepieces and would make a big difference.

 

39 minutes ago, ronin said:

 

It was certainly much better than it has been before. When I say it was far from sharp, I simply mean the brightness and edges weren't quite as sharp as the 12.4mm. Eyepieces are nice and clean, recently cleaned them with Baader fluid and cloth (but that's a whole other topic of discussion!), but worth checking again. I just kept switching a lot and wanted to look into something that would give me a compromise between the two lengths

[michael.h.f.wilkinson]

For an F/10 scope an EP of 9-10mm is often optimal on planets. The Vixen SLV 9 and 10mm should fit the bill nicely. They are excellent EPs with really nice eye relief and  and Pentax XW-type performance, albeit over a smaller FOV. The Vixen 8mm Plossl is just that, a Plossl. Most likely a good one (given my earlier experience with other, older Vixen Plossls of  focal lengths). Eye relief is very short which made me trade the 10mm I had for a Vixen LV 9mm (also an excellent choice if you can get one second hand, as is the NLV series).

[Jimtheslim]

I tried an 80 blue filter but I just can't get on with them. They don't seem to show any more detail and simply dim the planet. Maybe seeing just wasn't as good as I thought. Still would like to consider an eyepiece in the 8 - 9 range.

[michael.h.f.wilkinson]

I find blue filters make things worse, by increasing seeing problems.

[YKSE]

This thread can give you some ideas.

I'm of the opinion that trying to get a whole picture is the better way forwards, i.e. what's your possible future scopes? How the present stuffs (EPs, mounts, finders, etc) work on each one? It's not easy for sure, at least we have tried.

[spike95609]

If your budget can stretch that far I would also recommend a Vixen SLV as it will hold the quality of view when you switch to a fast scope, and providing you don't want to swap its 50° field of view for something more expansive, you won't find yourself buying another eyepiece to replace it at a later date. I was going to fill the gaps in my EP range with more TV plossls but in the end the tight eye relief put me off. NPLs are much cheaper though, I don't know how well they work in a fast scope, but for £39 it's not a serious gamble.

[Jimtheslim]

48 minutes ago, YKSE said:

This thread can give you some ideas.

I'm of the opinion that trying to get a whole picture is the better way forwards, i.e. what's your possible future scopes? How the present stuffs (EPs, mounts, finders, etc) work on each one? It's not easy for sure, at least we have tried.

I'm looking into a 10" skywatcher dob. Think they are about f/4.5 off the top of my head. I understand faster scopes are less forgiving on eyepieces hence I was looking to spend a little more on something I wont be looking to upgrade again. My budget for a good planetary eyepiece for such a scope I guess would be around 70 quid

[michael.h.f.wilkinson]

A second-hand LV, NLV or SLV can be had within your budget. New, the SLVs are a bit more. For a future F/4.5 (or F/4.7?) scope there is a 4mm LV on ABS-UK, but that is rather short for you current scope 

[Jimtheslim]

46 minutes ago, michael.h.f.wilkinson said:

A second-hand LV, NLV or SLV can be had within your budget. New, the SLVs are a bit more. For a future F/4.5 (or F/4.7?) scope there is a 4mm LV on ABS-UK, but that is rather short for you current scope

Yes it's the f/4.7 I was considering. I didn't want to buy another Meade plossl. I like the ones I have for the scope I have at the moment, however although they will be better than the optics supplied with a new Skywatcher, they might fall short at higher magnifications and so I wanted something that will perform well (or at least better) with the faster scope

[billyharris72]

1 hour ago, Jimtheslim said:

I'm looking into a 10" skywatcher dob.

That would definitely rule out an ortho and suggest a wider angle eyepiece if you can find a suitable one. As earlier, the Ex-Cels are good (9mm would be a good intermediary) and the BSTs get good reviews on here also.

[Moonshane]

Bear in mind that higher magnification even if the seeing allows it, will reduce brightness.

Based on what I have read, at your sort of budget, a Vixen 9mm SLV would be a great buy but this gives 100x magnification and I'd suggest a little more would be best. Your 6.4mm gives 140x which is often all I can use with my 12" dob albeit with a brighter image. Maybe try the 9mm and if you have a 2x barlow and can unscrew the elements, then if you screw this onto the eyepiece like a filter and it creates a 1.5x barlow so 6mm eyepiece. Might help with the 12mm initially to create an 8mm. Even cheap £20 barlows would probably be ok in a f10 frac at least for establishing what focal lengths work for you under certain conditions.

[Jimtheslim]

18 minutes ago, billyharris72 said:

That would definitely rule out an ortho and suggest a wider angle eyepiece if you can find a suitable one. As earlier, the Ex-Cels are good (9mm would be a good intermediary) and the BSTs get good reviews on here also.

What is a BST, is that the brand or type?

 

[YKSE]

17 minutes ago, billyharris72 said:

That would definitely rule out an ortho and suggest a wider angle eyepiece if you can find a suitable one. As earlier, the Ex-Cels are good (9mm would be a good intermediary) and the BSTs get good reviews on here also.

I'm not following your reasoning here, how do you know that it definitely rule an ortho? I know there're observers using ortho larger mirrors and f4.7/4.8 orthos happily.

Scatter control is one of the most important charater in planetary observing, and Abbe orthos are best in this aspect. Besides, you have, in your post above, that 9mm Ex-Cel does suffer glare from Jupiter, that, is exactly the scatter control in an eyepiece about.

[Mak the Night]

10mm BCO? http://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html

[Jimtheslim]

17 minutes ago, Mak the Night said:

10mm BCO? http://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html

I was going to go for one of these. Then decided on a hyperion 8mm, then it was a BST 8mm and now I'm considering a celestron x-xcel in a 7 or 9 after reading a few reviews of these versus the BST's.

[michael.h.f.wilkinson]

54 minutes ago, Moonshane said:

Bear in mind that higher magnification even if the seeing allows it, will reduce brightness.

Based on what I have read, at your sort of budget, a Vixen 9mm SLV would be a great buy but this gives 100x magnification and I'd suggest a little more would be best. Your 6.4mm gives 140x which is often all I can use with my 12" dob albeit with a brighter image. Maybe try the 9mm and if you have a 2x barlow and can unscrew the elements, then if you screw this onto the eyepiece like a filter and it creates a 1.5x barlow so 6mm eyepiece. Might help with the 12mm initially to create an 8mm. Even cheap £20 barlows would probably be ok in a f10 frac at least for establishing what focal lengths work for you under certain conditions.

100x in a 90mm aperture scope is often more useful than higher magnification, I find. I rarely push my 80mm F/6 triplet beyond 96x (5mm SLV or XW). In a 10" F/4.7, you will get a useful 133x, so for that scope you would like something like a 6mm (200x) and a 7 or 8mm (171 and 150x), and possibly a shorter one for days of really good seeing.

[John]

38 minutes ago, Jimtheslim said:

I was going to go for one of these. Then decided on a hyperion 8mm, then it was a BST 8mm and now I'm considering a celestron x-xcel in a 7 or 9 after reading a few reviews of these versus the BST's.

If you are thinking of an F/4.7 scope in the future then Hyperions are not a good investment IMHO.

The BST Starguider / Explorers and the Celestron X-Cell LX's are pretty much the same in performance and certainly do OK in my F/5.3 dobsonian. F/4.7 is somewhat tougher again though.

 

[Jimtheslim]

the hyperions were starting to fall behind in the running but i was attracted to the fact that you could use rings to get different mags (I think). It might sound silly to be looking into something that would work in my current f/10 refractor if I'm thinking of selling and going to an f/4.7 reflector, but the reality is thus might nit happen, at least nit in the near future. If I don't clear enough this month for a new scope I can at least treat myself to a new,quality eyepiece which might get used in the f/10 fir some time to come

[billyharris72]

1 hour ago, YKSE said:

I'm not following your reasoning here, how do you know that it definitely rule an ortho? I know there're observers using ortho larger mirrors and f4.7/4.8 orthos happily.

Fair point, and agree 100% about the importance of scatter control. I was thinking less about the optics and more about using a Dob with a narrow-FOV eyepiece and high magnification. With planetary observing it's important to sit down, slow down and just look, to let the detail reveal itself, and it's just that bit harder when you've having to chase the object. That said, I'm sure it gets easier with practice, so "rules out" was probably too strong a choice of words.

[YKSE]

Yes, drift time in high mag is a concern when EP's FOV is narrow, that's why I've always considered a tracking platform is the most important addition should I get a larger dob. All the aberrations, spherical aberration, astigmatism, coma, distortions etc, grows towards to edge, keeping observing in center of FOV solve lot of these issue, as long as the edge aberrations are not distracting.

Here's a link to explanantions of different aberrations

http://umich.edu/~lowbrows/reflections/2007/dscobel.27.html

[Mak the Night]

1 hour ago, Jimtheslim said:

I was going to go for one of these. Then decided on a hyperion 8mm, then it was a BST 8mm and now I'm considering a celestron x-xcel in a 7 or 9 after reading a few reviews of these versus the BST's.

I only have the 18mm and 32mm BCO's, although only the 18mm is actually an orthoscopic AFAIK as I think the 32mm is a Plossl. For the money the 18mm BCO is very good and easily equates with my Hutech ortho's or my 15mm Antares UPL. The Baader Eudiascopic 10mm looks very good but is more expensive. I believe the Eudiascopic is very similar in design if not identical (5 element) to my recently acquired Antares UPL 15mm (pictured). If it has the same performance as the UPL it is easily as good as a TeleVue.

http://www.firstlightoptics.com/baader-planetarium/baader-eudiascopic-ed-eyepieces.html