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Old 17-12-2012, 10:30 AM
Poita (Peter)
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Recommend a mono camera for f2 work!

Looking at the hyperstar systems that give you around f2 aperture using a C8, C9.25, C11 or C14, what are some possibilities for cameras?

The limiting factor is that you don't want the physical camera to be too large and block the incoming light.

Any recommendations new or old for nice slim, sensitive mono cameras?
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Old 18-12-2012, 01:05 PM
Poita (Peter)
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No one?
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Old 18-12-2012, 01:24 PM
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asimov (John)
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The Imaging Source cams are a lot smaller than any secondary housing I've seen on any SCT. 70mm corner to corner.

I've had mine apart, & one doesn't necessarily have to stick with the Imaging Sources original ally housing, & it's dimensions. I've seen some nice DSO work with these cams BTW. Not the best choice though..
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Old 18-12-2012, 03:06 PM
Poita (Peter)
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I never thought about using the DMK... I have a mono Grashopper 2, it certainly is small enough and pretty sensitive. It's not cooled though so it may be noisy. I'll give it a go though!
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Old 18-12-2012, 03:38 PM
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The Starlight Xpress cameras seem to be popular for Hyperstar systems because they are small and cylindrical...
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Old 18-12-2012, 05:10 PM
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At f2, you can forget 3nm NB filters
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Old 18-12-2012, 06:12 PM
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The OSC QHY cameras are designed to be about the same size as the secondary obstruction and thus good to use with hyperstar.
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Old 18-12-2012, 09:01 PM
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Tandum (Robin)
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You don't see many hyperstar images around. The few people I know that have gone down that path have all given it away.
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Old 18-12-2012, 09:31 PM
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i done some research about a year ago and found out that to get a fully illuminated image circle to not exceed a 28mm diagonal chip and i think if you can get a pixel size about 5um or under then that works optimally for f2 and hyperstar 3
as someone else has mentioned the SX and the new qhy10 or even the qhy12 would be fantastic
perhaps pm marc (ze froginator) as i know he had gone down the f2 route on a c11
i will be very interested in whatever you do as i would like to try it one day in the not too distant future........but i really need to sharpen other basic skills first ha ha!
good luck
pat
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Old 19-12-2012, 10:11 AM
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Peter,
I'd be looking to try the used SX cameras, either a one shot colour, or a mono with a filter slide/drawer.
I know of a couple that might be coming up, that would fit the bill. SXV-H9 and or SXV-H16. Both are round and would be similar to the size of the secondary area.
I'll find out and e mail you if they do become available.
Gary
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Old 19-12-2012, 10:48 AM
Poita (Peter)
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Quote:
Originally Posted by Tandum View Post
You don't see many hyperstar images around. The few people I know that have gone down that path have all given it away.
I've been more than happy with Hyperstar imaging with OSC, but would like to do some NarrowBand work.
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Old 19-12-2012, 11:33 AM
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multiweb (Marc)
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Did a fair bit of hyperstar imaging until I stripped my C11 apart for some major surgery. Just got it back together now and did some test last Wednesday which was clear(ish) in Sydney. Main issue is clear skies time at the moment.

TBH the hyperstar is great. I love it. Sure it is a little more demanding to setup but c'mon! Where else are you going to get a clear Horse head in a 30s exposure. It's a bit like solar imaging. Takes more time to setup than actually acquiring data.

I have used both an OSC (old square QHY8) in the past and recently a QHY9 mono (also square).

The obstruction is not an issue (with the C11 anyway). What's more of a problem is any straight cable or sharp angle/corner across the aperture. That will make a nice diffraction spike in no time.

So don't worry too much about the size of what you're putting in front but try to keep everything curve and avoid straight lines especially with cables.

What SCT are you using now?

PS: these are two 30s subs. collimation is pretty close but still a little off. My primary needs a tiny bit of tilt and I'm there. I don't collimate the hyperstar. It sits flat on the corrector.
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Last edited by multiweb; 19-12-2012 at 11:52 AM. Reason: added test shots
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Old 19-12-2012, 11:37 AM
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multiweb (Marc)
ze frogginator

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Quote:
Originally Posted by Bassnut View Post
At f2, you can forget 3nm NB filters
I heard about the light cone being too steep for NB filters to work properly due to the angle of incidence on the glass surface but I haven't seen anything different with my 7nm Ha. Don't have a 3nm set. They're too bloody dear.
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Old 19-12-2012, 12:08 PM
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Marc, that's a nice jellyfish in your horse head image. Great for 30 second images, really great.
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Old 19-12-2012, 12:37 PM
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multiweb (Marc)
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Quote:
Originally Posted by allan gould View Post
Marc, that's a nice jellyfish in your horse head image. Great for 30 second images, really great.
It's called the frog mouth nebula. Something you have to live with is schmidt reflections on very bright stars (Alnitak) in this case. It has something to do with the profile of the corrector I think. Good thing is you can get rid of them very easily by offsetting and stacking as they move when you move the scope and the subs are so easy to get I never had an issue with them. Funny enough there's none in NB. Don't know why.
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Old 19-12-2012, 02:27 PM
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Modern ccd and cmos have microlenses on the pixels. That is because pixels require light to hit them at a fairly straight up angle and the lenses limit the variation in angle - ie straighten the light up. Also often pixels are more sensitive on one side than the other and the lens is designed to focus the light more on the sensitive side.

Too fast no doubt would mean reduced efficiency of any CCD/CMOS sensor. As the light would hit it at a bad angle where efficiency is weak.

Also colour cameras may be worse off than mono. I read recently many posts about Sony Nex 7 cameras having magenta cast images when using ultra wide lenses as the angle of the light is too far over and this caused an annoying magenta cast to the image.

So I imagine from the above that a smaller chip would be better than a larger chip. That larger pixels may be better than smaller pixels due to generally better efficiency to start with.

Failing theory best look at photos from various setups and pick the camera that seems to be performing the best.

Greg.
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Old 19-12-2012, 07:09 PM
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Hi Peter,

I'm successfully using a QHY9 with a hyperstar C8. The obstruction is around 30% by area, but the sharpness is excellent and the speed is impressive. It totally transforms the common SCT as deep sky imaging system!

However, there a couple of problems to be aware of, for example:

1. Limited image circle, the Kodak 8300 is about the largest mono chip you would be able to use. There are some f3-4 imaging systems that can cover a Kodak 16803 and so are effectively faster and wider than the hyperstar.
2. Sprite like Reflections of bright stars can be quite severe.

Terry
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