focusing issues with low profile crayford

[jamie56]

Hi guys,

just got my little grubbies on a new low profile crayford for my sw 200p as the original rack and pinion one was naff for taking astro pics, problem now is I cant focus on stars and planets, lost the out travel side of things, any ideas how to overcome this, short of swoping focusers about depending on what you are doing ie imaging or viewing. Also would a coma corrector be usefull for pics? Cheers guys.

jamie

[ronin]

1" or 2" extension tube?

[Peter Drew]

A suitable extension tube should help. 

[jamie56]

Its a 2" with the usuall 1.25 insert, what would be a suitable extension tube? I have various extensions for my off axis guider, could I use these?

Jamie

[ronin]

Its a 2" with the usuall 1.25 insert, what would be a suitable extension tube? I have various extensions for my off axis guider, could I use these?

Jamie

Don't know the detail of these but as just about everything is 1.25" fittings I would guess one would do the job.

[todd8137]

2" ext tube all the way I had the same prob when I owned a 12" newt pretty cheap,of FLO

Pat

[rwilkey]

Hi Jamie, with out-focus problems I use the Baader FTR's, the 14mm in particular is sufficient I find, they screw nicely onto the 2"-1.25" adaptor and they take filters as well, most useful and a 'must' in my kit.

[jamie56]

Hi Robin,

thanks for that, would an extension tube suit for out travel?

Jamie

[rwilkey]

Hi Robin,

thanks for that, would an extension tube suit for out travel?

Jamie

Yes, an extension tube will also suit your purpose, the advantage of the FTR is that it comes in short length (ie 14mm) and that extension tubes usually start around 35mm.  I often find that if you need more out-focus it's usually only a little.  I find with the 14mm FTR I quite often have to draw the focus in quite a bit once fitted.  I sold my 35mm extension tube some time ago.  Just an extra thought, you need to ask yourself how much focus travel you really need.