Hyperstar test

[RobertM]

This is my first real test of the C11 Hyperstar after collimation.  I tried using a number of methods but in the end using a defocused star in live view seems the quickest (though not necessarily the most accurate).  The image is 10 x 60s uncalibrated so has plenty of warts and issues but I'm very happy that I managed collimation to such a good degree after only 10 mins.  Flats are the next problem though hopefully not so bad.

Reduced size:


Full size 450D image (560mm f/l f/2) :
http://farm6.static.flickr.com/5212/5408930284_66b2d46509_o.jpg

[Carole]

Going down the hyperstar route then Robert.  I read about this once as I wanted to know what it was when Daniel kept talking about it.  Sounds like a bit of an initial challenge but will produce good results once set up.

Carole

[Fay]

Looking good Robert, bet you are glad to have tried it out, I am envious of the 10x1 min subs!!

[Mac]

Looking good,

Mac

[PhilB]

That's not at all bad. Nice to see the investment is paying off.

[MarkS]

Looking very promising Robert!  I'm sure this is going to be a great rig.

Did you use a filter for this image? 
Is the 450D unmodified? Or have you taken the plunge!

I look forward to seeing a properly calibrated result.

Mark

[Rocket Pooch]

Can I borrow it and put my QSI on the front please, oh please!!!!

[RobertM]

Camera still unmodded and the filter was an IDAS LPS-P2.  I did get a 1000D to mod but after Err 99's had to go back.

There are very strange gradients which I need to investigate ... another day.

Chris, if you have a Canon adaptor then that idea might be a goer

[MarkS]

There are very strange gradients which I need to investigate ... another day.

Do you mean the dark strip along the bottom of the frame?  If so, it's caused by the mirror interrupting the light path and casting a "shadow".  It's bad enough at F2.8 on the bananascope - you'll have it even worse at F2.  It also causes a diffraction spike on the stars that fall within that strip.

I'm planning to rip the mirror out some time.  Won't be able to use the viewfinder any more but that is not a huge issue.

Mark

[RobertM]

Thanks Mark, that's what I thought it was and that'll be my solution too.  I'm also planning on buying one of the MkIII Canon 1.4 tele extenders to use with it but that's part of a longer term consolidation project.

Robert

[Daniel]

That's a great result Robert, I've been waiting for a first light of this for a while. you can see the mirror issue your getting in this image

http://www.flickr.com/photos/23188472@N02/3178909495/

those stars are looking lovely and round, amazed you got the collimation that good in just 10 minutes!

Daniel
:O)

[RobertM]

Hi Daniel,

Thanks and yes the flats are just like yours.  Collimation would actually have taken less than 5 minutes but it was miles out from previous duff attempts with CCD Inspector and manually recentering (don't ask).  I can also see two improvements that would make the system better - a) blackening the edges of the flattener optics and b) spring loading the adjusters.  Certainly the current push/pull arrangement of screws is the weak link when collimating, especially on a star as low as Sirius.

I made a 120mm mask to fit over the secondary housing to remove artifacts due to the shape of the camera and that certainly helped to produce a good out of focus dougnut for collimation.

Will do some flats and bias tonight and try stacking the other 30 subs.

Robert

[Daniel]

By the way, what's this about using a tele extender, is that with the hyperstar?

[RobertM]

That's one of its uses but I'm waiting for someone to review the 1.4 MkIII before deciding.

[mickw]

Cunning

784mm @ f3

[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?

[RobertM]

This is after recentering the secondary and re-collimation:



and the full res: http://farm6.static.flickr.com/5171/5497519449_9b009064ba_o.jpg

I think this is about as good as I can get by eyeball and liveview.

This was taken with the EOS 1000D ISO 200 a single 3 minute exposure.

Robert

[Rocket Pooch]

Looks pretty flat to me.

[Mac]

Nice sharp image,

Mac.