Lessons learned - Refractors and barlows....

[Alveprinsen]

So, about full moon tonight... clear skies...

So I head down to the observatory, and connect a 2x barlow to my 600mm 80ED refractor. And to my surprise.. impossible to get focus...

Ok.. so I add one of those spacers... still no focus.. And at this point, the tube is maximum extended, with a broom-stick length of stuff at the end of it with a camera in the very end.

Conclusion? - Barlows and refractors? Forget it....

Still, with my Maksutov I can add like a 3x barlow and still get focus...

I wonder, will I encounter problems like this when I receive my Skywatcher Explorer 200PDS Newtonian? The need for a 1,5km tube in order to focus a measly 2x barlow?

Sincerely, Alveprinsen.

[jambouk]

With the newtonian if you attach a DSLR you might not have enough inwards travel on the focus, so that barlow might come in handy!

There must be a less frustrating hobby than this

James

[Alveprinsen]

With the newtonian if you attach a DSLR you might not have enough inwards travel on the focus, so that barlow might come in handy!

There must be a less frustrating hobby than this

James

Uhm... ok?

so I guess an OAG is out of the question then?

Seriously.. how DO ppl. image... cant use this, cant use that... Seems to me the scope needs to be custom made for the camera...

[jambouk]

You can get skinny OAG attachments, and with a low profile focus tube you should be ok.

You need to do your home work before buying anything as there are things which don't work together how ever hard you may want them to.

That is the beauty of the forum. There is usually at least one other who has tried it before and failed, and there will be others who have found a solution/alternative.

James

[Steve Ward]

I use a Barlow with my ED80Pro and 1000D every day and have no problem getting focus ..... ?

It just needs an 2" adaptor extension between Barlow and focuser.

[toxic]

i have no problem with focusing the skywatcher 200pds and an eos i only need the extension tube when using an eyepiece for visual.  eos+t2+2inch coma correcter+focus tube for ap but then i have not tried a barlow as my barlow is not threaded.

[Alveprinsen]

I use a Barlow with my ED80Pro and 1000D every day and have no problem getting focus ..... ?

It just needs an 2" adaptor extension between Barlow and focuser.

I was using a 2" adaptor extension myself... still no focus. I considered adding another one, but... it seemed it would become so long it would start to flex...

[Alveprinsen]

i have no problem with focusing the skywatcher 200pds and an eos i only need the extension tube when using an eyepiece for visual.  eos+t2+2inch coma correcter+focus tube for ap but then i have not tried a barlow as my barlow is not threaded.

Sounds kickass.

I was worried I might get problems when I get the 200PDS.

So theres more than enough inward travel? I will be using a modified Canon EOS 600D.

[Steve Ward]

Don't know if it makes the difference but I use a 2" Barlow ... ?

This one .... http://www.scopesnskies.com/prod/barlow/2x2inch.html

[Alveprinsen]

Don't know if it makes the difference but I use a 2" Barlow ... ?

This one .... http://www.scopesnskies.com/prod/barlow/2x2inch.html

Ahh...

I dont know whether or not that would make a difference, but I was using a 1,25" one...

[Naemeth]

I was using a 2" adaptor extension myself... still no focus. I considered adding another one, but... it seemed it would become so long it would start to flex...

Your problem sounds like you were adding on 'out-focus', barlows bring the focal point in so require in-focus (ie. not using extension tubes)

[Alveprinsen]

Your problem sounds like you were adding on 'out-focus', barlows bring the focal point in so require in-focus (ie. not using extension tubes)

Hmm... Perhaps it would have looked different if I had used a prism... My barlows are made for use with eyepieces and stuff... would a prism correct for that I wonder? ... hmmm...

I simply attached a 2" spacer to the T-adapter for my camera, slipped the spacer and adapter into the barlow, and the barlow into the "hole" so to speak at the end of the telescope and tightened the screws..

[Alien 13]

My williams optics zs71 can get a bit long, at prime focus its scope > 2" camera adapter > t adapter > camera but doubles in lenght if i use a barlow its all quite rigid though. The shortest tube length is scope > field flattener > t adapter > camera.

[leemanley]

200PDS & Canon 550d =

No probs there !
 

[Mr Spock]

The 80ED focusser is made for use with a diagonal. The light path is too long for the focusser without one.

Useful tip for Barlows - screw the end off the Barlow and screw it on to the diagonal. You'll get between 2.5x and 3x from a 2x Barlow by doing that

[wxsatuser]

I tried EP projection with my Baader zoom without diagonal and barlow, it does'nt focus.

Wanted to reduce the weight hanging there but no.

[wxsatuser]

Here is some useful info......

http://www.myastrostuff.com/CCD-Imaging/projection.htm

[jambouk]

That's a really useful link, thanks.

James

[Alien 13]

This is what i use for eyepiece projection or a barlow. The lens goes inside the orion adapter you will also notice the 35mm length of spacers in there not strictly necessary but it reduces the exposed drawtube length. This setup would also work fine with the ED80.