Questions on barlows and ST80 extension tube

[LouisJB]

Hi,

I've a couple of unrelated questions.

1. Imaging planets, say Jupiter, I'd like to try something stronger than the kit SW 2x barlow to get a better image scale. What do people use, a 3x or 5x? I'm thinking or jumping to a 5x, is that a good or bad idea. Anyone got any recommendations on either that don't cost a fortune?

2. I guide through ST80, what exactly do I need to order to eliminate the diagonal in the light path to allow my QHY5L-II camera to focus. Has it a name, what length should it be, 50mm?

Many thanks!

[red dwalf]

1. You could use a 5 x barlow on your f5 scope giving f25, but usually the more you barlow the darker the image gets, well it does when I barlow my f10 sct to 5x, which is properly too much,

rule of thumb is more focal length for imaging planets and less for dso's

2. The piece your looking for is a extension tube, 2 inch is about right, maybe a little longer say 65mm ish, but to be totally honest I guide with a webam on my st80 and as they are so light I use the diagonal which works very well.

if I do use my atik titan to guide then I use a screw on extension tube to the rear of the st80 because the titan is alot heavier than the Web cam

[LouisJB]

thanks.

for 1. I've ordered a revelation astro 5x, cheap and should work with the F5 tube. I think going from 2x to 3x for planetary imaging might not have been a big enough jump, needed to bump up the image size considerably. Hope it works ok.

for 2. Ok - well it's not urgent, I was just thinking it might make things more reliable by removing possible movements. So it's a 1.25" 2-2.5" extension tube, it will need an eyepiece holder on the end to hold the 1.25" camera?

[Stephen]

1. 5x will be too much I fear but I'm sure there are others that manage this

2. 80mm T2 extension tube is what you require

[LouisJB]

1. you might well be right, but I guess I can only try it. If not, I might get the TV 3x as that seems to get good reviews for the price.

2. Ok, thank you!

[Uplooker]

Why not just unscrew the lens element from an unused (and not very good, anyway) Sky Watcher barlow and use that for the extension tube. It is also perfectly formed by having a set screw to hold the camera nosepiece.

Ian 

[LouisJB]

I can certainly give that a try, especially as I have two of the things already!!