Schickard Walled Plain

[MarkS]

Schickard walled plain 2 nights ago.  Eyepiece projection using 15mm eyepiece on Celestron C11 giving a focal ratio of approx F60.  This is the full frame but scaled down by a factor of 4.

Using the Canon EOS 350D, this is 10 exposures of 1 sec at ISO 100, stacked and strongly deconvolved.  I've only processed the red channel because it had the best quality data.  Even so, field curvature is very apparent towards the edges (defocusing).

The image scale is approx 0.7km / pixel.  The walled plain itself is approx 230x230km.




And below is Vallis Schroter, Aristarchus and Herodotus with exactly the same shooting parameters i.e. EOS 350D with 10 exposures of 1 sec at ISO 100 at F60, red channel only.  Final scale is 0.7km / pixel

[RobertM]

Very nice Mark, 1s is quite a long exposure time so I'm surprised you got so much detail especially at f/60.  Lovely detail and it doesn't look processed either.

[Mike]

Very nice Mark. I love close up moon images. Those jaggedy shadows of the mountains around the crater rim are excellent.

[JohnP]

Mark - they do look good & image scale is fantastic - They are very smooth as well - in fact they would even stand up to a touch of 'sharpening or wavelets' with no detremental effects....

I must admit I'm always impressed with the way you do the 'not so' conventional stuff - I would never of thought of eyepiece projection & EOS - wasn't vignetting a major problem...?

John

[Fay]

Fantastic mark!

[MarkS]

Thanks all, for your comments

Robert, John,

This was a deliberate experiment.  I reasoned that in broad terms a 1 sec exposure would have the same signal to noise ratio as 625 stacked webcam frames of 1/25sec (because of the square root law of noise).  So 10 frames of 1 sec is equivalent to stacking over 6000 webcam frames.  This allows some hefty wavelet processing to be done without creating too much in the way of noise or artifacts.

I should really have used even longer exposures but I wanted to avoid burning out the bright crater edges.

John, yes, there is scope for another iteration of wavelet sharpening - in fact I tried it after posting these last night, without detrimental effects.

Vignetting?  I expected it to be a problem but I can't see any severe effects in those images.

As a matter of interest, the FWHM of the Gaussian that gave the optimum deconvolution was 1.2 arcsec.  This is a pretty accurate measure of the seeing on that night (though this figure might also include air turbulence within the OTA itself).


Mark

[Mac]

very nice images.

i was wondering,

What would be the difference between using the 15mm eyepiece projection,
as against using a 2X Barlo and 30mm eyepiece projection.

I was thinking more along the lines, of the 30mm having a larger exit diameter, would that
give you easier focusing, ect.

[MarkS]

Very interesting point Mac:  15mm vs 30mm+Barlow 

From a focusing point of view, it will be equally critical whichever you choose.
From an exit diameter point of view, this clearly must have an effect i.e. you clearly wouldn't want a tiny exit diameter because somehow it would become the limiting factor in the setup.  But how and why?

I'll go away and draw a few diagrams