Barlow???

[paul schofield]

Hello again all on SGL, A bit of advice needed again please, I have been reviewing Barlow lenses for about a week,(sorry, budget Barlows I mean). As the sky watcher one that came with my 130p is not very good at all to say the least. I have narrowed it down to a TAL x 2 (hard to get hold of) but really decent apparently, or a Celestron Omni x 2. Does anyone have much knowledge of these 2 barlows. As usual any advice would be greatly appreciated. Thanks in advance..

[starstalker]

i can vouch for the tals, hav the x2 and x3 and not hard to get hold of... Tal

[Star-Gazer]

I am not entirely clear about when a barlow should be used or whether a telextender is better? If you have just looked into all this then can you enlighten me please?

[sixela]

A barlow is one form of telextender. Not all telextenders are called "a barlow". So we'd have to know which "telextender" you mean to say anything.

[paul schofield]

I believe that a barlow doubles the magnification of the eyepiece it is used with. So in effect doubles your E.P collection. I also think that clarity of image can be sacrificed with certain Barlows, if not all. Sorry you probably know this already. I have never heard of a telextender ?? but I am a total newbie. Good luck.....

[brantuk]

A 2x barlow will double the strength of an eyepiece so a 10mm becomes a 5mm. Best done with the highest quality you can afford. Tal's are great vfm at the budget end. Next up I would choose a Celestron Ultima or Orion Shorty Plus (recognised by most as the best you can get under £100 (around £80 new).

After that you'd be into Televue territory - Powermates being the best. You have to remember though that if you magnify the object you also magnify the atmosphere. It's not really worth doing with most supplied ep's that come with a new scope unless going for quality glass. It'd be better to get a single ep of the required size mostly.

[nightfisher]

i second brantuk`s comment, better to not use a barlow if poss, due to extra glass

[John]

A telextender does the same thing as a barlow but uses a slightly different optical design to achieve it. Telextenders can have some advantages over barlow lenses one of which being that they maintain the original eye relief and focus point of the eyepiece being used. Meade markets telextenders:

Meade - Meade Series 5000 TeleXtenders

I owned the 2" 2x Meade for a while and it was pretty good although a heavy and bulky accessory.

I believe the Tele Vue Powermates are also a type of telextender and their performance is really superb - with a price to match of course !.

Really good barlows / telextenders just seem to "get out of the way". The Antares 1.6x 2" that I currently use is in that category.

[brantuk]

Ahh yes I forgot the Antares 1.6 - very nice piece.

[Moonshane]

see U.K. Astronomy Buy & Sell

[smudgeball]

Hi

I went for the Astro Engineering 2x (1.5x) AC710 Barlow

Added bonus is the "T mount" thread on the end if I want to attach my DSLR.

Been really pleased with it.

Regards

Neil

[sixela]

i second brantuk`s comment, better to not use a barlow if poss, due to extra glass

A barlow and a simple eyepiece usually has "less glass" than many more complex eyepieces (for wider fields or for long eye relief). In fact, many eyepieces have a built-in lens group at the field end that functions pretty much like a barlow.

[sixela]

After that you'd be into Televue territory - Powermates being the best.

There's no reason to think Powermates are "better" than the plain TV barlows unless the specific features of the telecentric telextender are relevant (small insertion depth, relative independence of magnification factor and Powermate/eyepiece spacing, unchanged eye relief even for longer focal length eyepieces, lack of vignetting in some rare eyepieces, etc.). In fact, for planetary observation, I tend to prefer the 2x TV barlow by quite a margin (and I put my money where my mouth is and sold my 2.5x Powermate).