Hyperstar test

[Daniel]

I shall try out my jessops focal reducer when I get a chance.....................you never know!

[mickw]

It'll be like an 11" astrograph 

[RobertM]

Or an 11inch pile of poo 

[mickw]

Or an 11inch pile of poo 

Well that will be down to you then matey 

[RobertM]

Well if it does then I can always have more beer 

[mickw]

True

I'll swap you two one beer for the nyperstar   

[RobertM]

Deal- you drive a hard bargain Mick.  Now all I have to do is find a 'nyperstar' - they'd better be cheap !!

[mickw]

Doh

I must change my spell chucker

[RobertM]

This is the calibrated version, had a bit of trouble getting the flats right and in the end had to use some trailed images from after the mount battery gave up near the end of the session.

The image has been calibrated with darks, flats and bias and then one round of DDP to bring out the nebulosity and no other processing.  You can see halo reflections off the Hyperstar lens surfaces and also one artifact lower middle left.  I wonder whether that's a reflection off the sides of the lens.  I also need to sort out my processing workflow somewhat.

Calibration apart I'm really chuffed with this image, the stars are quite tight across the frame and it's very fast.  This image ended up being 22 x 60s in the end, no guiding and recorded to SD Card using a Canon interval timer as I didn't have a laptop.



And a link to the full version: http://farm6.static.flickr.com/5177/5414530742_c573d96ed0_o.jpg

Robert

[Mike]

Nice but ruined by the vertical noisy streaks down the image. What is causing that?

[Mac]

Excellent,

Just need to sort out the noise.

Mac

[MarkS]

Looks very good.  The haloes are not at all objectionable.

That "L"-shaped bright artifact over to the left and 1/3 of the way fom the bottom -  I guess is due to internal reflections.  
Here's another example (this time fom a Schmidt): http://www.robertreeves.com/repair1.htm

The vertical streaks are typical of patterning from the Canon CCD.  I always switch on "extreme dithering" in Nebulosity during shooting to help prevent it.  A very extreme example is here: http://forum.orpington-astronomy.org.uk/index.php?topic=2821.0

BTW - why is the whole image a mirror image?

Mark

[Fay]

looks like the streaks I have on my image, Mark

[RobertM]

Nice but ruined by the vertical noisy streaks down the image. What is causing that?

I'm sure the streaks are caused by trailed stars in the 12 or so subs I used for the flat frames, median filtering didn't entirely remove them.

Just need to sort out the noise

Yep, there's more that I would have expected and that's something I need to take a look at.  I suspect the red channel noise is due to faint Ha signal but that's only a guess.

Mark,  thanks for posting those links, both very interesting and noted.  Dean from Starizona has recently published that the spot sizes for the C11 Hyperstar are less than 7 microns across the field; that's twice the resolution of an FSQ and must be nearly on par with that Schmidt camera.  The image is mirrored because that's the way it came out of the camera, I'd usually flip the image so it matches reality but forgot.

Still plenty to think about but I'm comfortable now that I can collimate and focus quite quickly using live view which was my main worry.

Robert

[Fay]

Mark your second link is interesting. I wonder if 4 min exposures was not enough for my latest image, thing is, any more & the sub would have been completely white. I assume that white 5 min subs would be no good?