Barlow recommendations

[Mattscar]

Lately I seem to be taking up imaging, having started with an xbox webcam and now moving on to the SPC 900. When using a webcam with the SW 130p I have to image with a barlow, as without it just doesn't reach focus but easily does when barlowed.

So

With that in mind, what would people recommend as a barlow upgrade? I currently have the deluxe skywatcher one that came with my scope, but like everything in this hobby I'm sure someone somewhere has got a good way of working out what mag/brand etc works best for certain scopes.

If no such thing exists, what would people recommend anyway? Budget wise I'm looking around the £100 mark, as then I can either buy new or (hopefully) keep an eye out for something second hand from that price range thats been dropped down abit.

Cheers everyone

Matt

[knobby]

If you keep your eyes open on our classifieds or UK Astro buy sell, Televue 2 x barlows pop up sometimes.

Then you'd have a barlow of quality that you would keep far longer than your scope

Or this, 3 x might be a bit much though

http://www.astrobuysell.com/uk/propview.php?view=70284

Or these are well regarded and like rocking horse poo !

http://www.astrobuysell.com/uk/propview.php?view=69975

[Mattscar]

I had seen that first advert which is kind of the reason for this post. I was worried 3x might make it abit unmanageable, however I think I would like the extra magnification.

[knobby]

Someone cleverer than me will know about the maximum mag. for your scope !

If you're webcamming then its roughly the same as a 6mm ep.

I think your scope is 650mm so 6mm ep will give about 110 x mag so with the barlow would make 330 x

sounds a lot but on a good night who knows ?

[JamesF]

If you're webcamming then its roughly the same as a 6mm ep.

I think your scope is 650mm so 6mm ep will give about 110 x mag so with the barlow would make 330 x

*Cough* http://stargazerslounge.com/topic/179118-the-meme-must-die/

James

[JamesF]

The GSO/Revelation 2.5x barlow works well. The Celestron Ultima 2x has always had a good reputation if you can find one second hand, as does the Orion Shorty Plus (the same thing with a different name). It's nearer 2.3x though. If a Tele Vue barlow comes up cheap it's almost certainly worth picking up.

The problem you find as you get increasingly large multipliers is that it's harder to keep the image on the sensor when you add the barlow because the margin for error becomes so small. If you're going to go up to 3x I'd recommend also having an illuminated reticle eyepiece for centering the image. I find it easier to use my 2x or 2.5x barlow and then put a 40mm extension (actually an old barlow with the lenses removed) into the back of that to get more image scale than to use a 3x barlow straight away.

James

[knobby]

I did say 'someone cleverer than me' would explain it better!

got that bit right didn't I

[JamesF]

I have a feeling the "6mm eyepiece" thing came about purely to illustrate the apparent field of view of a webcam with a sensor the size of that in the SPC900 (and other similar 640x480 5.6um cameras). Given the range of cameras available now with different sensor sizes and that there are a whole range of 6mm eyepieces with fields of view of 100 degrees, 82 degrees, 70, 68, 50 and somewhere down in the mid-40s as well, I really don't think it's a helpful thing to say any more, if indeed it ever was.

James

[knobby]

Minefield...

I guess trial and error may be a good idea then, and if buying second hand you probably won't lose to much money?

how about a zoom Barlow? Needs to be invented me thinks

[Mattscar]

Haha, cheers for all that guys, its exactly what I needed. Its not something I feel the need to rush out and buy, as I'm going to try it with the one I have for a while. Just so I know what to keep and eye out for on the second hand market really.

I held off buying the 3x one as I thought there would be issues centering it and what with the mount I have at the moment (brilliant for observing, not so much for imaging) going to 3x wouldn't be the best plan.