Barlow or Tele converter for a DSLR

[oldpink]

I'm looking to add either a 3 or 4X Barlow for planetary imaging with my Canon 600D
I currently have a SW 2X barlow and was thinking that if I got a 2X tele converter and combined them that would give me 4X
or allow me to use the Tele converter in 2X mode with BYEOS and the X5 zoom
but also allow me to add a telephoto lens later for wide field with the camera alone

thoughts ??

anyone use a tele converter this way

[Leveye]

Get either a 2x or a 5x Televue Powermate and an EOS T-ring they make for it.

[SJP]

I asked something very similar recently and the advice I was given was use a teleconverter for terrestrial photography and use a Powermate rather than a Barlow for astro. In the end I bought a Canon Extender (teleconverter) and a Celestron 3x Barlow rather than spend the extra on a Powermate and have had very limited success using the teleconverter on the 'scope. You'll find that unless you tape-over the contacts or partially disengage the teleconverter to disconnect the electrical contacts you'll get an error every shot which requires a power-down of the camera. Focusing seemed to be very difficult with the teleconverter in place, and contrast suffered. Overall it wasn't my most successful purchase! Cheap teleconverters are worse than useless, they're definitely not designed for astro-use and they can't focus a single point of light adequately so I'd steer well clear of them. Expensive teleconverters are, well, expensive, they're better than the cheap ones but still don't seem ideal for astro work.

After trying various combinations I've ended up buying an inexpensive planetary camera as well. It was cheaper than the teleconverter by a factor of two and the small pixel size works perfectly for planetary captures. The DSLR (without the Barlow or teleconverter) works well for long-exposure deep-sky stuff.

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[oldpink]

I already have a Revelation 5X Barlow but its not much use as its putting my setup on the limit unless I get perfect viewing
thats why I want to go to 3X or possibly 4 so I can use it around F15 - 20

[Mr TamiyaCowboy]

Barlow : 

if you cannot afford a teleview powermate then your best purchasing a quality barlow.

problem is these quality barlows do not last long on the shelf, they sell out as soon as they hit the uk mainland.

A cheap barlow is just that, usually a single or doublet lens, with low power eyepieces they do just fine,

but start to push them or use them for imaging and you start having problems. color banding in the green and blue

is the usual give away, they start to produce more chroma.

Teleconverter : 

these are use with a camera lens, you normaly find these fitted to long camera lenses to double them up,

a 400mm F4 L now becomes a 800mm monster at around F7, Teleconverters are chip based,

they have contacts and the data between lens and camera is two way, the camera and lens talk to each other.

On a scope you need to blank off the contacts with tape sometimes this does not work and errors happen. 

Teleview powermate : 

i seen reviews and raves about these units. you dont take a 40s car to a 10s drag race.

and a powermate is just that a dragster of the optical world. these units command a price,

they can have triplet lens units of the finest quality optically correct lenses , the finest and expensive coatings around.

With the price come the knowing you pop one of these suckers in theres not going to be much of a problem

and the view /image you get back is near on optically perfect. 

I cannot afford a nice powermate ( wish i could ) so i run a dual 2x skywatcher barlow setup.

its not ideal in the one bit, but low powered eyepieces and the 4x mag is nice,

I have doubled up barlows on my ST80 and had it running at 1600mm @ around f20+

and able to resolve prycon with a microsoft hd5000 ( cinema/studio lifecam) webcam modded out.

My advice if using a DLSR and wanting to photo the sky, stay away from the barlow its gonna ruin shots

in the long run. use the telescope as one giant camera lens