Focal length question?

[northcanadian]

Hi folks:

I'm curious about my 9.25 sct which has a focal length of 2350mm. If I use a 3x barlow would the focal length be increased to roughly 23 feet...or is my math waaaaay out?

Cheers

Roger

[Freddie]

I make it 277.5" so yes, 23.1 feet.

[Laurie61]

Yes, it would be around 23 ft or f30. Ideal for planetary imaging

[JamesF]

Indeed so. The only problem is finding the planet again after you've put the barlow in

James

[kirkster501]

Indeed so. The only problem is finding the planet again after you've put the barlow in

James

..a most frustrating experience indeed. Only way I found is to defocus massively and look for the larger airy disk of the defocused planet and "focus into" the disk whist trying to centre the said defocused disk. I got rapidly annoyed with planetary AP for this reason.

[atmenterprises]

Indeed so. The only problem is finding the planet again after you've put the barlow in

James

Heck I have the same problem with my paltry 600mm!

[JamesF]

An illuminated reticle eyepiece is really helpful for this, so you can get the image dead centre before swapping. It's one of the reasons I like stacking a barlow and extension though, as I can recentre each time I add a new component.

James

[Laurie61]

It is a game trying to locate a planet at high fl. I ended up using an EP to center, then non barlowed camera before fitting the barlow. Then make sure you don't lose it I noticed just standing on the lawn by the mount moved the target on the screen

[Gina]

I gave up on planetary imaging because I couldn't find the planet too - and that was with a much shorter focal length Otherwise the planet was too small to see much detail.

[atmenterprises]

An illuminated reticle eyepiece is really helpful for this, so you can get the image dead centre before swapping. It's one of the reasons I like stacking a barlow and extension though, as I can recentre each time I add a new component.

James

I just picked up one of those a few weeks back and it made my life so much easier for planetary work.

[Psychobilly]

I used to autoguide on the planets.. used to keep it nicely centered even on a smallish chip...

Peter...

[northcanadian]

Thanks all:

May the Clear Sky Gods be kind to you.

Cheers

Roger