Conus Nebulous

[dvj (John)]

http://img836.imageshack.us/img836/6483/concrop.jpg

10 x 900s
RH200, f/3
6nm Ha filter
SBIG ST 11000

Bit of a crop on the full image. Nice pedestrian shot of the neighborhood. Hubble's variable nebula in lower left corner.

[peter_4059 (Peter)]

Beaut image John. There's some amazing detail around the tip of the cone.

[Larryp (Laurie)]

Very nice-lots of detail

[batema (Mark)]

Stunning. Well done.

[LewisM]

Oh yeah, that'd be rather nice!

[alexandre (Alexandre)]

Hy John .
Bravo for this very beautiful image!
I look at it with a big interest, because the RH200 is a telescope which I shall buy for to exploit of the big field rather quickly.
But on the image I notice that stars are not perfectly round, why?

Bye for now!
@lex

[dvj (John)]

Originally Posted by alexandre

Hy John .
Bravo for this very beautiful image!
I look at it with a big interest, because the RH200 is a telescope which I shall buy for to exploit of the big field rather quickly.
But on the image I notice that stars are not perfectly round, why?

Bye for now!
@lex

Well.... that is because it is not a perfect telescope. It is difficult to collimate and over time requires collimation tuning. You would be better off with the FSQ for big image circle with very sharp stars to the corners. If you are adverse to telescope adjustments, the RH200 f/3 not the scope for you. It's an expensive little instrument that requires a bit of TLC. Large central obstruction, small image circle, many optical surfaces, heavy tube assembly, prone to differential flexure. That may sound critical of me, but it is the truth.

[multiweb (Marc)]

Beaute details but the stars look a little white clipped.

[dvj (John)]

Originally Posted by multiweb

Beaute details but the stars look a little white clipped.

White clipped? Sounds racist to me.

[multiweb (Marc)]

Originally Posted by dvj

White clipped? Sounds racist to me.

Highlight clipped is the PC version then.

[alexandre (Alexandre)]

Hy!
Thank you John, I did not think of finding this kind of defects with the quality optical which we know of Riccardi Honders!!
I am not against a small alteration of the collimation from time to time, but if it remains comparable has my C9, I would go even somewhere else, and can be one 106??
This Tube pleased me for that focal speed , thus has to see!!

Bye !
@lex

[dvj (John)]

Originally Posted by alexandre

Hy!
Thank you John, I did not think of finding this kind of defects with the quality optical which we know of Riccardi Honders!!
I am not against a small alteration of the collimation from time to time, but if it remains comparable has my C9, I would go even somewhere else, and can be one 106??
This Tube pleased me for that focal speed , thus has to see!!

Bye !
@lex

To be clear, it's not the quality of the optics or the Riccardi-Honders design, it is the extreme mechanical collimation and tip/tilt sensitivity at F/3 that requires a steady hand. Once those are locked in, you have an excellent system. Fortunately OS provides crude but effectrive tip/tilt adjustment for the camera, and easy to use collimation. What was surprising was that there was a recent apparent mechanical shift somewhere in the optical train. This changed the orthogonality of the camera to the backplate. It was very minor, but just enough to tilt the focal surface leading to the slightly elliptical star shapes.

[alexandre (Alexandre)]

John , your montage is to screw ?
Because , with another montage , I think this is the possible tilt on the optical train!

have you the photos to show your montage ?

@lex.

[dvj (John)]

Originally Posted by alexandre

John , your montage is to screw ?
Because , with another montage , I think this is the possible tilt on the optical train!

have you the photos to show your montage ?

@lex.

Alexandre, I think something is lost in translation. I don't understand your question.

[alexandre (Alexandre)]

Sorry John .
The tilt come can be of your assembly(editing)?.
Do you have an editing screwed?.
I find that three small screws are often too low to prevent a tilt with a caméra CCD !.

@lex.

[Ross G]

Hi John,

That is a beautiful monochrome photo.

Sharp, amazing tonal range and great composition.

...who cares if the stars are slightly off!..

Ross.

[dvj (John)]

Originally Posted by alexandre

Sorry John .
The tilt come can be of your assembly(editing)?.
Do you have an editing screwed?.
I find that three small screws are often too low to prevent a tilt with a caméra CCD !.

@lex.

Image train tip and tilt are fully corrected by the 4 screws on the tip tilt plate. Only very very minor adjustments are made to correct for minor orthogonality issues with the image train. I use a depth guage to make very minor but recordable adjustments.

j