Too much mag?

[Itabot]

Wanting to add an higher powered BST Starguider EP to my collection, may be the 5mm or 3.2mm ?, I've noticed quite a few members that have a SW 200p Dob, list the full set of BST Starguiders in their signature, including the 3.2 mm, am I right in thinking thinking it would possibly never get used at 375x mag .

Is the best we can expect in the UK between 200x to 250x.

[nightfisher]

I would say you are correct about this, if i had a 200 dob i would not even buy the 3.2mm, i have a 4mm ortho as my highest power ep and that never gets used, even the 5mm only comes out to play on very good nights

[alan potts]

I don't have a 200mm dob but I am sure I would never use that amount of power for a serious observation. I would have thought 5mm was as high as you would need to go.

alan

[laudropb]

I don't think you would ever get to use it unless you were fortunate enough to be at a truly dark sky site and the seeing was perfect

[Charic]

I have and use the 3.2mm. I use all my eyepieces  to simply frame the target. I don't think to myself (example ) I'm using a 12mm here, I just look to see if it fills the field of view and gives me the best image, I'll swap and change until I find what's best The more focal lengths I own, the more framing options I have!

At 375x you have to appreciate that your target wont stay still for long - not at all! But I can track my Skyliner fairly well, and although I don't use any filters, to reduce the brightness, I do enjoy looking inside craters on the Moon and along the Terminator. Maybe this EP is specific for this task on my system, as is my 6mm WO to get my 200x power. ( I  have the WO on recommendation from rwilky, such  an excellent choice for a wide-view eyepiece for the Skyliner) but if  Alan had  a Starguider 6mm back then, it too would be in my signature. Also, the nature and quality of the Starguider line-up, I too also considered, should I have the 3.2mm, do I need it. Yes was my answer, it conforms to having the 'kit' and gives me the options as mentioned above.

Remember the Sky-watcher Skyliner is designed  for 200x, so a 6mm or 12mm Barlowed gives me that power, anything over this parameter may shortfall some expectations?

Theory suggests the Skyliner, under perfect conditions can reach 400x but practically 200x using the data plate is easily achievable under UK skies. A 3.2mm is still within the theoretical limits, and works for me on the Moon, but further afield, probably not so good. 

Hopefully  the darker nights are not too far away, so that I can start / continue using my scope again, its just too light here for my Skyliner during these Summer nights?

I've also acquired some  RA/GSO Plossl EP's  just for testing and comparison! I've  Always wanted a Plossl kit from the outset, and I think I have found what I need. They wont replace the paradigm designed Starguiders!

Lastly with such a similar set-up, Barlow that 8mm to see what 4mm looks like on the Moon. Then decide if you need the 3.2?

[scarp15]

With my 8" F6 dob, I use a 6mm and 5mm eyepiece 200x and 240x respectively, both are effective, yet I not feel a need to go any higher.

[ronl]

The 5 mm will give you 240 mag, which you might get to use now and again, you

would be better getting a 6 mm which would be 200 mag, the 5 mm Starguider is

a nice eyepiece and I use it quite a lot, but sometimes the seeing is not suitable, so

I use a W O. SPL 6mm, which costs more than a Starguider but gives great views,

your scope is f/6, mine is f/5, thats the only difference, the 5 mm gives me 200 mag

and the 6 mm gives me 167 mag, you would use a 6 mm much more than the 5 mm,

there are cheaper 6 mm eyepieces around, put a new post in and ask what others use.

Clear Sky's

[spike95609]

I've got a 6mm giving 200x on my 250px, which is the same focal length as your 200p. I am considering adding a 5mm at some point for those rare special occasions, but on most nights 200x feels like the limit.

[Mr Spock]

The ideal magnification for a balance between detail and contrast comes at about x1 per mm. So for a 200p you'll be aiming for x200. Any thing above that and the image will just get darker with less contrast and less sharpness. On most nights seeing conditions are going to limit the times you could get above x200 anyway.

A good, 82° 6mm eyepiece would be ideal. There's enough magnification and a wide enough field to make tracking and viewing easier.

[ronin]

Your initial post reads that you do not have the 5mm so that that is the one to consider, it will get some use.

The 3.2mm you will use very rarely, however when Mars makes an appearance, starting early 2016, you will likely want more (to at least try) then the 5mm will deliver. It may not give a good view, but you might gt one night when it allows Martian detail to come through. Equally an 8mm and a good barlow would be the sensible first step.

Bit of a shame they made it 3.2mm as 4mm or 3.8mm would have been I think more useful.

Mind you the 2.3mm X-Cel seems very close to pointless.

Ignoring performance etc the 3.2mm BST has nice purple rings. :D

[Charic]

......colour freak!   They look good in the Day, but  colour coding is useless at night. I'm sure I  noted somewhere that  the same colour  banding had been  used for a different  focal length! This was due to a different branding. but internally,  the same eyepiece. 

As I said earlier, you may consider this eyepiece for a specific task. I don't think you need any special viewing requirements for the Moon, but for the likes of  distant planets, I've yet to find out?

[Reeny]

I have an 11mm barlowed down to 5mm, and it is too much magnification for most of the time.

When it works - it is spectacular, so I would recommend getting the 5mm.

I have also tried to use the 9mm barlowed down to 4mm (290-330x mag)

The views are blurry and hazy, so I normally go back to the 240x mag / or 200x mag.

The 9mm stays with the travel scope now.

[Itabot]

Many thanks all for your advise and opinions,very interesting, I'm now thinking of the suggested Williams Optics SPL 6mm for the sweet spot 200x for my scope, shame Alan doesn't have a 6mm in his line up, I like the BST's.

[Charic]

Itabot.....I've often read that the sweet spot for the 200 is achieved by using a 12mm.  This  same EP could be Barlowed to achieve the 200x that the scope  is fully capable  of achieving!

If like me you use the data from the label on the scope,  doubling the focal ratio f/6  becomes 12 equating to the focal length of the eyepiece? These components you already have. But there is also mention that the sweetspot is achieved when the eyepiece  matches the scope in all parameters, therefore a 6mm matches the focal ratio AND produces the 200x on a Skyliner, so technically, this would be 'sweet' or 'perfect'. Anywhere between 1-2mm exit pupil should produce clear sharp Planetary images,  but don't let me stop you investing in the WO 6mm SPL, that still is a very good eyepiece, I've even considered buying the 12mm, but still favour the Starguiders.

[Itabot]

Thanks Charic, for putting me right, interesting, with little knowledge I just assumed,  thinking I will have a play around with the kit I have a little before spending any cash.  

Just wish we could have a few clear nights in Cumbria now and again, where I live it's just impossible to get out to gain more experience.

[scarp15]

Thanks Charic, for putting me right, interesting, with little knowledge I just assumed,  thinking I will have a play around with the kit I have a little before spending any cash.  

Just wish we could have a few clear nights in Cumbria now and again, where I live it's just impossible to get out to gain more experience.

I know, we have just had to cancel a planned camping trip today near Keswick due to the horrible weather forecast over the next few days.

At high (and mid to high) power I quite like to have a few focal length options, 5mm, 6mm and 8mm. The 8mm 150x (with 1200 FL F6 dob) receives the most use.

[Itabot]

Thanks Scarp 15, sorry you've had to cancel your camping trip, reminds me of a horrendous wet and windy weekend  camping at a site on the shore of Derwent Water Keswick, I was up all night hanging on to our frame tent, fearing we'd loose it, all night long unhappy campers were screaming and shouting as their  tents were ripped to shreds or blown over. 

[bingevader]

Ooh, I remember a camping trip like that, ending up looking like something out of Winnie the Pooh after hanging on to the tent all night, the rest of the camp site was flattened.

Doesn't anyone else look at the moon?!

That takes buckets of magnification.

I often use my 7mm with a barlow on that (same 'scope).

The 6mm and Barlow produces too many problems with floaters and dust specks for me, but a 3.2mm might be spot on as long as conditions are favourable.

A 5mm on it's own would be lovely.

The WO SPL 6mm EP is fab, btw.

Needs a good steady night on the likes of Jupiter, which have been few and far between of late.

But in the long run, I think all 3 EPs would probably be worth it (and a 7mm at some point)!

Having a range at high magnification and being able to swap between them doesn't half make a difference, because the difference in magnification varies so much more at the short focal lengths.

On Jupiter, I use the 8mm, 7mm and 6mm the most.

The 5mm is for the very good nights, but having said that, last Feb I put the barlow on the 8mm EP and the views were tremendous!

The clarity dropped in and out, but when it was clear, my goodness it was worth it for the detail.

It had been as clear (or not so, depending on how you look at it!) through the 6mm the night before.

Mined you, I'm not suggesting you should go out and buy them all immediately!

It's taken me some years to collect my EPs.

And, as Charic has suggested, you can check out a 6mm, to see what you think, by sticking your barlow on the 12mm.

Sorry for jibbering!

[alro]

Ive used my x2 barlow on moon with 12mm /8mm bst starguider and meade sp 6.4 and 9.7, just to see max i could use, based on this i can justify 5mm starguider for very good conditions.

al

[Itabot]

Thanks Bingevader, Alr for your advice, I'll have to save up, next project to find space in my EP case, will there be any space for the foam