Greg Thanks for your input.
I'm using a canon 500d. with a celestron 6.3 focal reducer and flattener plus a radial guider bnetween. maybe i need to ditch the radial guider and have spacers .
I've tried imaging also with a 2 inch adapter between the radial guider and camera. From memory my distance from reducer to chip is around 100mm.
Cheers carl
Quote:
Originally Posted by gregbradley
If you are using a Canon 5D on an SCT you are probably not going to be able to get round stars at the corners with any reducer.
You need a flattener, not a reducer. And a 5D is a 35mm sized sensor so that requires a corrected circle of about 44mm or so.
That is quite large and generally that would mean you need a 3.5 inch or larger focuser.
You will not be able to achieve with anything less.
What camera is this?
If its an APS sized sensor then I think you should be able to get all stars in focus. I am pretty sure there are plenty of images around where this is the case.
All reducers/flatteners have a specified metal back distance. The definition of this term is the distance from the last metal flange to the chip.
For example 86.2mm usually with a stated tolerance like +/-6mm.
You are moving it 50mm to check. That is a huge variance. They are usually way more sensitive to the spacing than that - more like +/- 6mm.
Also I am not sure what effect the radial guider has. Is that rotating as the scope is tracking? That may explain your rotating stars whilst your PA is accurate (if it proves to be - it would be the first thing to check).
Most likely you are expecting round stars to the corners that is not possible with that setup if you are using a 5D.
Greg.
|