LX90 - a 'baffling' problem (for me anyway :P )

[goldblade1983]

Hi all!

As we're back into imaging season I thought I would check something with you guys before I start getting frustrated again - it's probably an easy question but I'm useless with the mathematics for focus / focal length etc.

I have an 8 inch LX90.

I have the 0.63 Meade focal reducer

I will be using a modified Canon 300 (I think d - don't have it to hand)

 

In the past when using my LX90 with Sony DSLR I've always had trouble with essentially what looks like probably the optical tube baffling coming into the picture and so having to crop (a lot).  Is this simply because I need some sort of spacer?  And what is the best / correct spacer for the Canon above. 

Many thanks!

Brian

 (PS - I also have a WO GT81 with focal reducer and don't have the same issues -  My plan for this year is to 'try' and get both LX90 and WO GT81 balanced side by side on NEQ6 and swap between the two depending on targets. - wish me luck!)

[Davey-T]

The sensor of the camera needs to be between 100 / 150 mm from the back of the focal reducer, not too critical it just alters the actual focal length a bit.

Dave

Here's what I use, you can add more extension if you need it

[cjdawson]

The setup that I used looks like this.

That's a 70d, attached to a flip mirror with a T-ring, then attached to the SCT thread with the smallest tube that I can get.  I insert the .63 FR on the end of the small extension tube.

 

One thing to watch for is over exposing can product rings if the maths isn't 100% correct.

As you can see the rings are rather easy to see.  I'm going to attempt this again by dropping the flip mirror out of the setup and will use the standard T-thread adapter.  if that doesn't work, I'll use the short extension to get the sensor closer into the lens.

 

Either way, you shouldn't have problems.  The above image is uncropped, from my LX-90.

[ollypenrice]

The spacing also affects the true change to focal length and so to focal ratio. Plate solving has shown many owners that the FL was not giving them the F6.3 for which the flattener-reducer is optimized.

Olly

[goldblade1983]

Thanks - I can see where I'm going wrong. Back focal distance of Eos 300 is 44mm I think so I can do the maths from there! I might actually have a spacer somewhere that will fit but if not will buy one. Cheers

[Davey-T]

5 hours ago, goldblade1983 said:

Thanks - I can see where I'm going wrong. Back focal distance of Eos 300 is 44mm I think so I can do the maths from there! I might actually have a spacer somewhere that will fit but if not will buy one. Cheers

Back focus with the T ring, which is generally 10mm, should be 55mm, get spaced somewhere between 100mm and 150mm, minus the 55mm,measured from the rear of the focal reducer and try it.

Dave

[goldblade1983]

Yup - ie need a spacer of between approx 50 and 100 mm - can anyone point to where I can buy the necessary adapters? 

[Davey-T]

5 hours ago, goldblade1983 said:

Yup - ie need a spacer of between approx 50 and 100 mm - can anyone point to where I can buy the necessary adapters? 

Have you already got something with an SCT thread to join to the focal reducer ?

Dave