Two Eta Carina nebula Shots for comparison

[kosh]

Hi all,
I know its a fairly easy target, but I just modded my Canon 1000D and wanted to test it out using my 8" F4 Newt and the little ED80.
Which one do you guys think is better?
Also, anyone know why I have double diffraction spikes with the Newt?

Image 1 (Newt ) : 20 x 120 sec subs iso400, 10 Darks modded 1000D
Image 2 ( ED80 ) : 10 x 180secs subs iso400, 10 darks, modded 1000D

Both images guided.

Thanks for looking.

[IanP]

My vote goes to ED80 ..

[Andy01 (Andy)]

ditto on the refractor

[alpal]

Hi Kosh,
The double diffraction spikes are caused by being out of focus.
You really need a coma corrector for that Newt.
The refractor has come out a lot better.

cheers
Allan

[kosh]

Originally Posted by IanP

My vote goes to ED80 ..

Originally Posted by Andy01

ditto on the refractor

Yeah me too. Maybe a reprocessing of the newt image will help. Its a little blown out at the bright bit.

Originally Posted by alpal

Hi Kosh,
The double diffraction spikes are caused by being out of focus.
You really need a coma corrector for that Newt.
The refractor has come out a lot better.

cheers
Allan

Thanks allan. I already use a baader mpcc mk3. I'm not really getting as much help from it as I had hoped. Could something else be going wrong there?

[alpal]

Originally Posted by kosh

Thanks allan. I already use a baader mpcc mk3. I'm not really getting as much help from it as I had hoped. Could something else be going wrong there?

Hi Kosh,
The coma corrector has to be exactly the right distance to the camera chip
in order to work properly.
I had an MPCC on my old DSLR setup & was never able to adjust it.
The distance was too short when using an OAG.
I don't have that problem with my CCD camera as I have an RCC corrector
which gives plenty of back focus & also a Varilock adjuster to get the right distance.

Maybe someone else can advise?

cheers
Allan

[kosh]

Originally Posted by alpal

Hi Kosh,
The coma corrector has to be exactly the right distance to the camera chip
in order to work properly.
I had an MPCC on my old DSLR setup & was never able to adjust it.
The distance was too short when using an OAG.
I don't have that problem with my CCD camera as I have an RCC corrector
which gives plenty of back focus & also a Varilock adjuster to get the right distance.

Maybe someone else can advise?

cheers
Allan

Allan, I think you are right. I have a small spacer in between the corrector and the DSLR to give me some extra back focus. I didn't realise that the distance between the corrector and the DSLR sensor had to be 55mm. How embarrassing
I hope your suggestion works, it's an easy fix.

[alpal]

Originally Posted by kosh

Allan, I think you are right. I have a small spacer in between the corrector and the DSLR to give me some extra back focus. I didn't realise that the distance between the corrector and the DSLR sensor had to be 55mm. How embarrassing
I hope your suggestion works, it's an easy fix.

Hi Kosh,
That's good but it's not that easy -
the distance of 55mm is recommended but will change by ± 1 mm
or maybe more - depending on your scope.
That allows the MPCC to correct for different f ratios.
You may need a set of spacers to try.

cheers
Allan