Another conundrum...

[timthelder]

Well,I thought I would take a few shots Saturday evening

so I got all set up early,achieved the best alignment yet to date,(20 min dead in the center of the crosshairs@391x mag.)found my object,and found out,with the crayford focuser on the back of my scope,it apparently increases the focal length so much I can't use the 6.3 reducer.(which also threads on the back of the SCT.)

The scope and the crayford run out of focusing room.:hmm:

Anyone tried or had any success with those .5x reducers that thread on the nose of the camera like a filter?

Otherwise I will just have to take the Crayford out of the mix so I can use the reducer.(I'm lazy.)

Just thought I would ask here before I up'n buy one of those little devils.Only to find out it won't work either.

Trial and error...gotta luv it.

[hpcoolahan]

Hey there Timthelder,

Have you tried the reducer in front of the focuser??

Might work, meades work like that.:thumbsupmate:

Clear Skies
Pat

[timthelder]

Howdy hp,good to hear from ya.

The reducer IS on the back of the scope first.My setup was going to be something like...reducer>crayford>diagonal>lens/camera.

If I use the reducer,which is made to thread on the back of the scope,then the crayord,which threads onto the reducer it adds roughly about 8-10cm to the focal length.(may be causing that parfocal problem as well.)

Anyway,the crayford is made to thread on the back of the scope,or on to a 2 inch thread...such as the 6.3 reducer.

But that's not working for me.

That's why I was thinking about maybe placing a .5x reducer,onto the camera after the crayford...because it's sure not working the way I had it planned.(in front of the focuser.)

I can omit the focuser,put the threaded ring back onto the diagonal,(I bought a barrel for it so I could insert it into the focuser.)

And just screw the diagonal onto the reducer.(that's what I did before adding the crayford.)

But I really like the fine focusing of the crayford....I was hoping to keep it in the drive train of the imaging process if you know what I mean.No more mirror shifting when I am focusing...

Sigh.....Off to eBay...again.

[Radar]

Hi Tim,

This is an interesting problem. Theoretically buying another reducer should fix your problem. But you could also introduce a new problem.

For some reason telescope accessory manufacturers don't take into account the extra focal length that their accessories create. It is annoying sometimes that simple things such as filter wheels or focusers take up so much focal length.

The problem you could have with

reducer>crayford>diagonal>reducer>lens/camera

is flexure.

The weight of all these things combined has a very good chance of causing the image path to be bent slightly. I know the crayford focuser is nice to use but if you have another built in focuser on your telescope I'd say remove the crayford and your problems will be solved.

Have you got a photo of this setup?

Ray

[hpcoolahan]

G'day there Tim .

Does the diagonal HAVE to be in there??:hmm:
Most people have it set up like this,, scope>reducer>focuser>camera.

So if u can get rid of the diagonal , shorter image train,able to reach focus better.:hmm:

I never use a diagonal when imaging,,in fact i collimate the scope with no diagonal in place , so when i image i know its collimated properly.
not all diagonals are accurately made, so if its collimated with it in , it will probably be wrong with it out.

Just a thought!!

Most focal reducers are designed to work best at a set distance. (between reducer and its focal plane.)
If u can find out its distance it might help you work out how long the image train has to be to work.:pipethinker:



Clear Skies

Patrick

[timthelder]

:hmm:


reducer>crayford>diagonal>reducer>lens/camera
Not two reducers...Omit the 2 inch,and use a .5x on the nose of the imager,stacked with an IR filter.


Does the diagonal HAVE to be in there??
I suppose not,I could slap in a lens adapter after doing alignment and shoot straight through.


so if its collimated with it in , it will probably be wrong with it out.
I've never checked this...might be worth a look.

Thanks fella's,I'll keep you posted on the solution.

[hpcoolahan]

well Timthelder,

How goes the focus woes??:woot:

Just thought we could do with an update.:smile:


Clear Skies
Pat

[timthelder]

Howdy hp,

I ordered a .5x focal reducer that threads onto the end of a lens(or a camera),the reason why is because it comes with a seperates 25mm extension tube,which should do the trick in extending a lens so I can make it parfocal.Plus I figured I could probably use the reducer on occasion as well.(hasn't arrived yet.)

I will still probably wind up having to take the crayford out of the optical path when using ANY reducer though.Just not enough focusing room.

I'll keep you posted should I have any breakthroughs...