Good spread of eyepieces for a SW 200p

[JulianFR]

As a telescope beginner I find the subject of eye-pieces quite complex. I have a Sky Watcher 200 (f 1200) Dob, which came with 10mm and 25mm eye-pieces.

Could anyone advise me on what range and what type of other eye-pieces would be useful to cover general viewing, while not breaking my small bank!

On a different point, the finder-scope is difficult for me to use as I can't get my head and eye close enough to the tube to look up it! Any thoughts on whether I should try to find a right-angle finder ... Or should I go straight to a Telrad/Rigel finder?

Many thanks in advance, Julian

[Mr Spock]

When I had a scope of that fl, I found my most used eyepiece for deep sky was 13mm (x92). The 25mm (x48) you have is ok for low power.

For planets a 5mm would just be about right. I wouldn't be tempted to use a Barlow with the 10mm, the supplied 10mm is notoriously poor You may find a 6mm (x200) useful as well for when the sky isn't steady enough for x240 on the 5mm.

[Schorhr]

Hello Julian,

a Telrad vor Rigel is a great Addition, in combination with maps... It saves a lot oft time and struggle.

AS for eyepieces, the UWA 66 degree apparent viele oft view are great budget eyepieces and give amaing views. They only Cost 30€ and are even cheaper then the HR planetary for 45€, which are also great budget eyepieces.

They are only avyilable in 6, 9, 15 and 20mm though, so you may want to ad a 30-35mm eyepiece to your list.

You should get one eyepiece for overviews, one for maximum magnification, and one vor two inbetween.

The rule of thumb is to keep the exit pupil (eyepiece mm devided by telescope focal ratio) between 0,5 and 7mm, but also conditions limit this. Older people's iris may not reach seven mm anymore, and due to light pollution even the ideal eye won't. So under a 5mag sky, 5mm exit pupil will do, and rarely will you need anything larger then six mm exit pupil, else light is "wasted", as it won't reach the eye.

Maximum magnification' may it be 0,5-0,6mm exit pupil or "double apperture in mm" is also not allways possible. 200, perhaps 250x magnification is often the limit under clear skies with good seeing/air turbulances. But for those rare very clear nights it is great to have either an eyepiece to magnify higer or a barlow.

Also the object you observe should not stand low on the horizon as seeing will be worse then as well.

So what eyepieces to get always depends on conditions, observation preferances and budget. A six mm UWA and a 30-35mm erfle will be good budget eyepieces. The 9 and 20mm uwa as well. If your main focus is planets or small deepsky objects, consider some hr planetary so you can inch forward to the maximum magnification thats possible each night.

Of course there are also cheaper eyepieces such as the seben/orbinr plossl. Other thrn their telescops that seem to have bad reputation, i foun their plossl and achromatic barlow quite good for the price. But below nine mm plossl are not comfortable to look through, similar if you compare your two eyepieces, where you have to get closer to the ten mm. I have a four mm plossl and observing through it is very anoying' a eight mm eyepiece and a barlow might loose som contrast, but is overall easier to observe with. The uwa and hr planetary do have y large eye relief, one more reason to get those. Also a 25mm erfle will show as much as a 32mm plossl due to the larger apparent field of view. Keep Theiß in Kind when considering cheap eyepieces and exit pupil, too.

as the question is asked frequently, a two inch eyepiece makes sense for lower power eyepieces, as a 32mm plossl or 24mm erfle show about the maximum field the focuser barrel will show, so a 40mm plossl may sound like a good idea, but all it does is show a lower magnification with a narrower field of view...

Check out stellarium (freeware) and set up a few eyepices (crtl-o, alt-o) to see the difference of a 32mm 50 degree afov eyepice, a 24mm 68degrre afov, and a 40mm 40degree afov.

:-)

[ronl]

Try this link http://www.swindonstargazers.com/beginners/eyepieces.htm it's

a very good site and will help you understand eyepieces, there is lot's of

information, and how much the different types cost, and also features the BST

range of eyepieces which will suit your scope.

[Avocette]

There's also a very good piece in 'Getting Started General Help and Advice' called 'Eyepieces - the very least you need'. Also think about raising the mount off the ground on a water butt stand - helps align your eye with the finderscope without being a contortionist.

[twotter]

I have a 200P dob and I've built up a collection of Baader Hyperions (around £65 second hand), and tend to use my 24mm and 13mm most often

[JulianFR]

Thanks for the advice all. Really helpful. It confirms my fear that optics is a difficult topic for me so I was right to ask for help. Great article on eye-pieces Ron ... Thanks for the link. That's my local astronomy society in Swindon so I plan to join with my son (hope they will put up with me!)

Any preferences on the two red laser finder brands?

Julian

[Jiggy 67]

You might want to consider a zoom eyepiece such as the Baader Hyperion Zoom. Looks, initialy, like a lot of money to shell out but you are getting, in effect, a lot of ep's for your money. Some people say that they are not as good as fixed focal length ep's but unless your an expert with finely tuned eyes to the subtle differences in ep's, I don't think you will see a difference.....personaly I'm a big fan and I use mine all the time, I find the quality to be good and with the added bonus of not having to scratch around in the dark to change ep's, I'd recommend them.

[66mikeg]

+1 for the Hyperion Zoom

[scuffer]

If you get a RA finder then I would recommend a Rigel or Telrad as well , it's difficult to pin point the sky with a RA finder on its own. Really depends on how much you want to spend on ep's , some names to look for are TMB planetary , BST Explorer and vixen NPL are thought to be decent good priced eps