Tulips anyone?

[Rocket Pooch]

Tulips from hamster jam, roll on France!

18x6 minute Ha, usual kit.

[Fay]

Fantastic Chris!!!!

[RobertM]

Nice one Chris, but which of the usual kit did you use ?

[JohnP]

Nice FOV & very 'tulip' like.... I can't believe how many hot pixels you had on the image that you sent me last night...

John

[MarkS]

Beautiful - that captures it nicely.  I can now see how it looks like a tulip.

[Rocket Pooch]

Nice one Chris, but which of the usual kit did you use ?

ED80 and Atik 314L, EQ6 Skyscan, still no SXD its being repaired.

Chris

[RobertM]

That's really bad about the SXD, firstly their QC should have been better and secondly how ling can it take to replace a locking screw !  So Chris, which mount have you an eye on ?  also are you really going for an 8300 based camera for wide field ?

[Rocket Pooch]

Hi,

Providing I don't talk my way out of a job this week (another story), I was thinking or replacing the EQ6 with something like a G42 or Altus, that would leave enough for the camera, if I did an AP I would not have the cash to get the camera.  Anyway so yes and yes I suppose, I think it will be a G42 not the Altus because of the experience dealing with the SXD problem.

Then I will be able to image at a full 2 meters or more at 9mpix !!!

But I would need to change all the filters etc!
 

[RobertM]

Imaging consistently at 2 meters is a whole new ball game as you're probably aware... another challenge !

Had a go the other day with the DSLR, 10 mins at F10 (2350mm) on the C9.25, trailing all over the place but better than I expected overall as there wasn't much coma over the frame.

[MarkS]

Imaging consistently at 2 meters is a whole new ball game as you're probably aware... another challenge !

In what ways does it present new challenges? 
My C11 with focal reducer effectively gives 1800mm so I must be constantly facing them!

[RobertM]

New challenges over imaging at less than 500-600mm as guiding has to be more accurate and movement in any component becomes more of an issue.

[MarkS]

Which reminds me - I had terrible problems with guiding and trailing last night.  Tonight I've just discovered why - my mount (left outside until tonight) was polar aligned on the wrong star!!!   

[Fay]

  I am surprised at you Mark, that sort of thing usually only happens to me!!

[JohnP]

Phew Mark...! - I'm glad it wasn't the ToUcam... That is a big mistake though unless you have Mag 6 skies in your garden then it's understandable.....

John

[Rocket Pooch]

The challenge is to get no drift on the subs and ensure that everything is absolutely bang on, i.e. every little pixel used with little elongation; I get a star centroid elongation of approx .0133 on my subs at the moment and thats at 600mm at 2 meters that going to goto a third of a pixel, ok call me fussy.

[RobertM]

Not fussy, thats what you need. +/- half a pixel may show on fainter stars and dimishes their brightness substantially.  BTW 0.0133 sounds like an excellent result.

[Fay]

Stop showing off Chris!

[MarkS]

.0133 at 600mm is an absolutely astonishing result!  But how does that translate into a third of a pixel at 2 meters?

With my C11 on the EQ6 I've got my guiding down to approx 1.3 pixels at 1800mm.  Still got a long way to go ...

[Rocket Pooch]

The pixels on the guide camera are 13microns at 400mm the ones on the imaging camera are 6.45 at 2000mm and the .0133 is the adv of guiding with .025 being the max at 400mm, just work out therefore what the movement at 400mm at .025 is against the smaller pixels at 2000mm and you will get the image scale drift, easy, and no I can't do it in my head so you can work it out for yourself.

[MarkS]

O.K. then.  Working it out for myself I get this:

guide camera pixels are almost exactly twice the size of the  imaging camera pixels.  The imaging camera has 5x the focal length of the guide camera.  Therefore a 1 shift on the guide camera would result in a 10 pixel shift on the imaging camera.

So if .025 pixel is the max error on your guide then on the image you will see 10x this i.e. 0.25 pixel.  Since this is a tiny fraction of the blur caused by the seeing when using 2000mm, I can't believe it would ever be noticeable.

[Rocket Pooch]

It does a little have a look at this, http://farm3.static.flickr.com/2249/2483192672_10d463c6a2_o.jpg

You will see a little elongation.

Chris

P.S. You probably right though, I'm being fussy.