too barlow or not?

[algol]

Just a quick question, would it be better for visual work on planets to use a 12mm with 2x Barlow or a 6mm without?

[ronin]

For planets people tend to go for the least glass possible, therefore Ortho's and plossl's are often chosen.

So that tends to mean that barlows are not included.

The other aspect is that a barlow is a "general" item and is not designed as a specific item for the optics of one particular scope so they add in small aberrations of some sort.

[Dude_with_the_tube]

i use orthos for planetary or also ultrawides,but no barlow.However,there is nothing wrong with using a barlow.orthos tend to have quite tight eye relief and one way around is to use a lower power eye piece in likes of 12.5mm ortho and a 2x barlow.Orthos barlow very well and there is very minimal if any loss of quality of image.has to be a good quality barlow in likes of Televue 2x or any othe good make what can be picked up s/h for about 60 quid,not the cheap chinese ones .

[RikM]

I prefer not to use a barlow because I use reasonably heavy eyepieces and the extra length sticking out puts strain on the focuser. I do still use one occasionally though. In my case a Televue 2.5x barlow with a 10mm eyepiece to get the equivalent of 4mm. This gives me 300x magnification in my scope and on rare occasions, when the atmosphere permits this level of magnification, it is very nice to have and it cost £50, where the equivalent eyepiece would be £200 plus. Also as above though, if you don't mind the smaller field of view and getting up close and personal with the eye lens, orthoscopics offer stunning performance for the money.

[Grotemobile]

http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-ed-deluxe-2x-two-inch-barlow-lens.html

This is the barlow I use,when I use it.

It is mainly for lunar use.I also

use it for imaging.

Steve

[Don Pensack]

A lot of modern eyepieces have built-in barlows in their bases in order to keep the eye relief longer than it otherwise would be, and

to reduce aberrations.

A good barlow:

--loses minimal light--so minimal as to be irrelevant to brightness.

--increases the light cone prior to hitting the eyepiece, making the light rays more parallel, and induced aberrations in the eyepiece

much less.  Many eyepieces marginal at f/5 work great in a barlow.

--keeps the eye relief of the longer focal length (or even slightly increases it), improving comfort over the shorter (well, most shorter)

eyepieces.

--decreases light scatter over the entire field by providing additional baffling for the eyepiece

--can be used at varying distances from the eyepiece to yield slight differences in power.  A barlow is only its stated

magnification at one distance away from the eyepiece--expand the distance and the magnification factor increases, and reduces

if the lens is used closer to the eyepiece.  At distances dramatically different than the design, though, spherical aberration can

increase, which wouldn't be useful in planetary observing.

--is invisible in use.  The only things noticeable when a good barlow is used are and increase in magnification, a darker field,

and possibly more issues with the seeing conditions, all of which would be noticeable in a higher power eyepiece.

Myself, I use eyepieces to yield magnifications up to 388X.  But for the occasional 456X, 608X, or 776X, I use a barlow

(well, actually a PowerMate) and the only issues I've noticed is when that magnification is too high for the seeing.

My lifetime-best Jupiter image was with the PowerMate at 456X.

[Paul73]

I started from the premiss that sticking even more between me and the target couldn't be a good thing. However, I have since discovered that it is another tool in your arsenal. I use an second hand 2x Tal one (thanks Earl) which gives not just more magnifications but different combinations.

Example 1 : splitting the double double in Lyra. Using my 6mm Vixen SLV - can't split the right hand pair. 2x Barlowed Delos 12mm and there it was!

Example 2 : ring nebula. Barlowed Delos 12mm - rubbish. Vixen SLV 6mm - lovely. This really surprised me.

Paul