Star elongation and Reducer spacing - what does it mean

[AlistairW]

Hello,

I read on this forum that star elongation can be caused by the distance generated by adding a FF/FR to the camera chip sensor. If that were the case what would you typically see image - all stars elongated across the full image ?

Then I hear you  can us deralin spacers. How exactly does that work ?

Thanks

Alistair

[swag72]

The star elongation will tend to be in corners either radially or in a whooshing away from the corners way, depending on if there's too much or too little space. Someone posted on here some time ago a brilliant diagram showing the two effects, but Im not sure if this was only for a specific reducer and telescope combo. I've posted them and if they don't relate to your combo, then I'm sure someone will say .....

The first image is the spacing is too close and the second it's too much.

Delrins are great - You put them between threads of connecting parts and so when you screw everything together, it will only screw down as far as the Delrin and so you gain some spacing.

[ollypenrice]

14 hours ago, swag72 said:

The star elongation will tend to be in corners either radially or in a whooshing away from the corners way, 

 

 

Olly

[swag72]

You knew what I meant though @ollypenrice

[ollypenrice]

3 hours ago, swag72 said:

You knew what I meant though @ollypenrice

Absolutely! I like plain English, hence the applause.

Olly

[ian_bird]

The Too Far - Too Close diagrams apply to all flatteners. T'was me whot posted them originally! ;-)

Cheers.

Ian

[swag72]

6 minutes ago, ian_bird said:

The Too Far - Too Close diagrams apply to all flatteners. T'was me whot posted them originally! ;-)

Cheers.

Ian

I'm sure that they've been a godsend to many Ian. I hope you didn't mind me posting them..... I'd seen them before and thought they were so helpful that I saved them...... is that OK?

[ian_bird]

Sara - absolutely OK. They are not my originals - I got them from the support guys at Teleskop Service.

Cheers!

Ian

[AlistairW]

Thanks for the help everyone - now I understand.

[AlistairW]

Hi,

I have one last question. My images display characteristics of the second image "so the spacing is too much". What can I do to correct  ?

I am using a DSLR with a FF/FR

Thanks

Alistair

 

[swag72]

How does your imaging train fit together? Are there any spacers or adapters in there?