To much magnification?

[steve_bham]

Is 208x too much magnification for a scope. My focal length is 1250 and the eye piece my looking at is 6mm giving a magnification of 208x appeture is 5" SCT.

[johninderby]

300x is the max magnification under perfect conditions for your scope. 208x should be OK, but it all depends on what the seeing is like and what you are trying to observe, some nights you can only use half the theoretical max magnification or much less.

Try using the Televue eyepiece calculator. http://www.televue.com/engine/calculate3b.asp?NoBack=True&_2in=yes

John

[johankj]

I think the rule of thumb is 50-60 times inches of aperture, so maximum useful magnification : 50-60 * 5" = 250-300.

There are all sorts of things that affect if you can see anything at that magnification, like atmospheric conditions, light pollution, exit pupil, optical resolution of your instrument (these are the ones I know about). I'm no expert, but if you can track and see your target, why not 208x?

Are you buying a new 6mm eye piece? I'm just starting out in amateur astronomy, and I find that I'm buying longer and longer eye pieces. My latest procurement is a 32mm plossl.

[acey]

A 6mm should be fine as a maximum power eyepiece for a 5". But be aware that with some designs at that focal length you have a very small lens which can be uncomfortable to use. Rather than a plossl you might want a design such as the TMB planetary.

Such high power is good on Moon/planets if the air is sufficiently stable, and in some deep-sky applications, but for most deep-sky viewing I use lower magnifications. For a long time I used an 8mm eyepiece as my maximum power on a 200mm F6 dob and felt no need to go any higher.

[brianb]

a magnification of 208x appeture is 5" SCT.

I'd say that is too much. Except possibly for double stars near the zenith on the steadiest seeing day of the year.

For planets, 25-30x per inch is enough, you can pick out all the detail he scope can resolve if you look carefully & the brighter image that you get at 25x per inch allows low contrast detail to be seen more easily than if you are using 50x per inch.

With my own 11" SCT I've used x225 (12.5mm) fairly frequently but x280 (10mm) only a couple of times, on neither occasion could I see any more with the higher power.

[crovax]

I have 130mm/900mm reflector and I use high-power EPs rarely....but when I get a chance to, it's purely awesome! I used 4mm (225x) and even 6,5mm+Barlow (276x which is a bit higher than my limit) on Saturn and the look was totally great. And the moon is awesome too! But you really need good skies for that. On bad nights you'll get useless smudges with that magnification. Also there are really not many targets that you'll be able to magnify like that. So both Andromeda and Whirlpool galaxy looked the best with 25mm and magnifying them furher didn't bring any results. I was able to notice them with 10mm EP but they were better at 25mm.

Anyway I think buying high-power EPs is worth it (unless you don't have good skies at all). Planets look really amazing in them.

[steve_bham]

Hi i was looking at either:

William Optics - William Optics SPL eyepiece

or:

Skywatcher - Skywatcher Ultrawide eyepieces

in 6mm, which do you think is the better one?

[johninderby]

I've had both and the WO SPL is just in a different class completely, well worth the extra. Lots of eye relief, very sharp and with very good contrast. The SPL just feels and performs like a more expensive eyepiece than it actually is.

Very highly recommended.

John

[Capricorn]

For a 5 inch I would say that you should get fair results up to 150x, may get to 180x if everything is right but then images will deteriorate.

Used to be said that max mag was 1.5xDia in mm. Have noticed in the last couple of years that manufacturers are saying 2xDia in mm. Have also noticed a corresponding increase in people saying that with the "new" high magnification they are getting poor results.