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Old 27-11-2009, 10:17 AM
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QHY8, C8 and Hyperstar

Presently I have an imaging set-up using a 127mm f/7 refractor and a QHY8, which gives me pleasing results... but I'm interested in shorter exposure times and wider field of view for those big DSO's

I have a C8 OTA (off a Nexstar 8) just sitting idle... A Hyperstar lens is calling to me... It'd give me f/2.0 and 400mm focal length. A fast astrograph on a budget!

The question is, if I locate a QHY8 in front of a C8, will the QHY8 create too large an obstruction? The QHY8 is 100mm square, and the C8 is only 200mm diameter...

Has anyone here tried a large-ish camera such as the QHY8 on a Hyperstar and C8? Any opinions from those in the know would be valuable before I rush out and spend my money

Edit: Starizona reckon it works fine! http://starizona.com/acb/hyperstar/hyperstar3/


Cheers,

Rob

Last edited by Astrod00d; 27-11-2009 at 01:35 PM.
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Old 27-11-2009, 08:21 PM
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tlgerdes (Trevor)
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Multiweb (Marc) did this with a C11 and QHY8. Cabling is seemed to be and issue, he posted stuff about it about 6-8 weeks ago.
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Old 27-11-2009, 10:26 PM
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A QHY8 Pro would be a better form factor.
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Old 28-11-2009, 12:10 AM
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Rob,

I highly recommend the hyperstar. The obstruction by area of the QHY8 is ~25% so its not a big penalty.

I am using a C8 hyperstar with a QHY9 which has slightly more obstruction again but I'm very impressed. Attached is a single unguided 60 second exposure of the horsehead nebula.

Pros - Inexpensive, very fast, excellent edge-edge sharpness. Fantastic value for money.

Cons - Bright stars cast funky reflections. Also some might not like the diffraction spike caused by the cabling.

Terry
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Last edited by CometGuy; 28-11-2009 at 06:26 AM. Reason: Horsehead Unspun - must have been late when I posted!
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Old 28-11-2009, 12:22 AM
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Octane (Humayun)
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Terry,

That image has totally spun me out.

Regards,
Humayun

Quote:
Originally Posted by CometGuy View Post
Rob,

I highly recommend the hyperstar. The obstruction by area of the QHY8 is ~25% so its not a big penalty.

I am using a C8 hyperstar with a QHY9 which has slightly more obstruction again but I'm very impressed. Attached is a single unguided 60 second exposure of the horsehead nebula.

Pros - Inexpensive, very fast, excellent edge-edge sharpness. Fantastic value for money.

Cons - Bright stars cast funky reflections. Also some might not like the diffraction spike caused by the cabling.

Terry
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Old 28-11-2009, 06:40 AM
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How's that now Humayun

Anyway here are some photo's of the QHY9/Hyperstar mounted on the C8. The QHY8 I believe is 90mm x 90mm (compared to the 110mm diaameter of the QHY9).

Terry
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Old 28-11-2009, 09:14 AM
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Wow, 60 seconds. Very fast.
Was this done from dark skies?

Matt.
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Old 28-11-2009, 09:50 AM
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Quote:
Originally Posted by Astrod00d View Post
The question is, if I locate a QHY8 in front of a C8, will the QHY8 create too large an obstruction? The QHY8 is 100mm square, and the C8 is only 200mm diameter...

Has anyone here tried a large-ish camera such as the QHY8 on a Hyperstar and C8? Any opinions from those in the know would be valuable before I rush out and spend my money

Edit: Starizona reckon it works fine! http://starizona.com/acb/hyperstar/hyperstar3/


Cheers,

Rob
Yay! A new HS user I have one for the C11 so I can't comment but Terry's happy with it so go for it. As far as FOV's concerned, not sure you'll get much wider than your refractor. My C11+HS3 gives me very similar field as my 5" at F/5, but I can take 30s exposures instead of 15min ones. I'm just getting back into it now that I have finished aligning the optics on my C11. Did a few test last night. B.E.A.U.tiful!

Quote:
Originally Posted by CometGuy View Post
Rob,

I highly recommend the hyperstar. The obstruction by area of the QHY8 is ~25% so its not a big penalty.

I am using a C8 hyperstar with a QHY9 which has slightly more obstruction again but I'm very impressed. Attached is a single unguided 60 second exposure of the horsehead nebula.

Pros - Inexpensive, very fast, excellent edge-edge sharpness. Fantastic value for money.

Cons - Bright stars cast funky reflections. Also some might not like the diffraction spike caused by the cabling.

Terry
I have bought right angle cabling which I still have to put in place. So the central power goes straight down and the S-video and USB are 90 degrees on each side so I can make a spider vane pattern. If you don't separate the cabling you get one big fat horizontal diffraction spike across the stars. I've also seen those secondary reflections with a C11+HS3 combo on the QHYCCD forum. They reckon it could be reflections caused byt the corrector plate. I haven't investigated further yet as I haven't had the problem (yet) and haven't started using it "in production" mode.

Last edited by multiweb; 28-11-2009 at 10:12 AM. Reason: spelling
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Old 28-11-2009, 02:11 PM
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Matt,

This was from Bayside Brisbane, so there is significant light pollution. The background sky level on the raw image were quite high, so from a true dark sky it would have been quite a bit more impressive!

Marc, I'm going to try reducing the cables cross-section by clamping the cables so they are at right angles.
Terry
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Old 03-12-2009, 12:42 PM
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Hey thanks guys for all your input, your results look good. I was thinking that converting an SCT into an f/1.8 astrograph would give mediocre performance at best, however you've proven otherwise. Now... should I spend almost a grand upgrading my C8 (I'll need the adapter kit USD250) or should I hunt around for a good C11 OTA and convert that? Yes and a QHY8 Pro would be nice too... Hmmm... the slippery slope hahaha

Cheers,

Rob
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Old 03-12-2009, 03:43 PM
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Check this for the power cables. Trev found the link for me. I bought 4 adapters.
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Old 03-12-2009, 09:11 PM
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Marc,

Thank you for that info BTW it looks like the reflections shown in the Horsehead shot appear because collimation is slightly out. With better collimation test images of Peacock tonight (mag 1.9 B2 star) showed only a faint reflection.

Rob,

The C11 will give you more flexibility with what cameras you can use because it has more backfocus (i.e you can use a DSLR) and perhaps its possible to use a filterwheel with a mono -CCD. It also obviously has a lot more light gathering power.

The C8 is better if you want to maximise field of view as well as keep costs down. You can still use 2" filters as there is an internal thread in the camera adapter for that purpose.

The sharpness is really quite superb and certainly better (per pixel) than the scope natively, or with a focal reducer.

Terry
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Old 04-12-2009, 08:26 AM
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Quote:
Originally Posted by CometGuy View Post
Marc,

Thank you for that info BTW it looks like the reflections shown in the Horsehead shot appear because collimation is slightly out. With better collimation test images of Peacock tonight (mag 1.9 B2 star) showed only a faint reflection.
No worries. Oh good. If it can be fixed with better collimation it sounds good. I might start trying to collimate my newt better now as well. I started to assume those reflections were caused by the QHY* sensor glass. Will do some test shots this saturday hopefully if the weather's good.
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Old 04-12-2009, 09:05 AM
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wow, 60sec's, that is impressive. I cant get that with 10mins with my 1000d and 8" GSO Newt.

Got me thinking.... I feel a burning in my wallet...
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Old 05-12-2009, 04:14 PM
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No luck getting collimation spot on, but one thing I found is that you can't tighten up the push-pull screws very well. For some reason they use a nylon sleeve under the pull screw which tends to compress slightly. So I made a trip to Jaycar to get some small metal sleeves to replace the nylon ones (see photo). Also a small amount of lubricant on the screws to stop them binding up.

Terry
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