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  #1  
Old 23-10-2009, 12:30 AM
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Tandum (Robin)
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QHY8 Reflections.

I'm wondering what others have done to kill the reflections from bright stars with the ever popular QHY8 cameras.

I note that some have added a T-Thread extension and put the original nosepiece on the end while others have replaced the nosepiece with a 2" adapter and plonked an IR/UV filter on the end.

It seems the idea is to move the filter further from the sensor yet I've heard others have screwed a t-thread filter directly into the camera.

What is the best option. I tried the 2" adapter option tonight and the sensor had ice on it pretty quickly. However icing aside, it made a big difference in these 200sec unguided shots.
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  #2  
Old 23-10-2009, 05:18 AM
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Maybe remove the standard nose piece, and have a new one made up that is open, but threaded for a 2" filter. Grab yourself a Baader U filter and screw that on, using a little bit of sealant grease on the thread to ensure its sealed.. That reflection is a direct result of the rather low quality anti reflecting filter in the standard nose piece..

If you have freezing issues even after sealing it up with a 2" filter, you could open the camera up and find somewhere to tape in a big sillica gel satchel... That would suck the moisture out of the camera once sealed up, and keep the nasty ice off the chip... I also found with my QHY8 that regular (once a month) cleaning with 99% Isopropyl alcohol greatly reduced any icing issues..

I'll post back when I've got more time to go over other things I thought of when I had my QHY8... Off to work for now
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Old 23-10-2009, 08:59 AM
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As yet I have not noticed any reflections in my system - maybe just lucky but I also run a 2" dew heater around the front of the camera to stop any moisture condensation on the filter
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  #4  
Old 23-10-2009, 09:19 AM
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toryglen-boy (Duncan)
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i have removed the nosepiece, and am using a Baader MPCC, with a LPR filter on the end, sometimes i notice reflections, but its usually a reflection of the centre marker on the mirror

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Old 23-10-2009, 01:29 PM
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Quote:
Originally Posted by toryglen-boy View Post
i have removed the nosepiece, and am using a Baader MPCC, with a LPR filter on the end, sometimes i notice reflections, but its usually a reflection of the centre marker on the mirror

Duncan, what (if anything) did you do about maintaining the 55mm separation between the imaging chip and the MPCC?
Peter
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Old 23-10-2009, 01:55 PM
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peter, a 30 and a 5mm t thread extension would do it. You can get heaps of different size extensions.
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Old 23-10-2009, 02:39 PM
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Quote:
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Duncan, what (if anything) did you do about maintaining the 55mm separation between the imaging chip and the MPCC?
Peter
Well, thats a strange one Peter.

I have the spacing correct (55mm as far as i can see) and i get shocking coma. I have been in touch with Peter Lee over this in HK, as he sells a MPCC to QHY8 adaptor thats "back focus matched" so i would assume this to mean that, the adaptor will put the focus behind the MPCC exactly where its supposed to be.

Cost of the adaptor is $50 posted

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Old 24-10-2009, 05:07 PM
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If the image is already flat, or close to it, it can over correct and give you coma. I had this issue when i used the Giant Reducer from Lumicon, and because of the flat field of the RCX, it gave coma near the edges where there wasnt bfore.

Theo
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  #9  
Old 27-10-2009, 11:41 PM
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I was a bit worried about geting correct distance to the tak reducer after changing to a different nosepiece. After all, I got a custom adapter made for the qhy8. I've since found that by screwing the reducer onto the tube first instead of the camera adjuster then screwing on the CAA and the tak 2" adapter, the distance is exactly the same as the custom adapter

I'll check it out when the weather clears.

Last edited by Tandum; 27-10-2009 at 11:55 PM.
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  #10  
Old 28-10-2009, 07:05 AM
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Hi Robin, To reduce reflections I use a 2" camera adapter with a Baader UV/IR blocking filter on the end of this. I screw it directly into the camera.
Icing is another problem which is usually taken care of with a desicant strip, well cleaned sensor, and a camera which has been blown out with a quite hot hair dryer. Here in Mt Beauty the Rel Humidity over winter is often in the very high 90's% and with ambient temps falling to 0 or below during an imaging session it can be hard, I have used argon gas to purge the camera and while this works well, if the camera is left on the telescope overnight some leakage occurs through the USB and power sockets. I have found the best method to be to just blow the camera out with a hot hair dryer and assemble quickly just before an imaging session. It works well, take only a few seconds to do and has no ill effects on the camera.
To clean the CCD I use a lint free cloth, Isopropyl alch or acetone.
Good luck.
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  #11  
Old 31-10-2009, 10:52 PM
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Doug, I've had a M42-> 2" nose piece on for a couple of hours now with no ice. I used a little black greese from the RC cars on the threads and a hair dryer to dry it out. I have the astronomik IR filter I got off you on the end of it but it's got overcast and wet so I can't test for reflections At least it's not frosting up yet
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  #12  
Old 02-11-2009, 03:26 PM
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Hey Doug, I've been looking around to source some dessicant strip. Where do you source it?
Peter
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  #13  
Old 03-11-2009, 09:13 PM
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Peter,
Gama might have some -> http://web.aanet.com.au/gama/index.html
Else QHY -> http://www.qhyccd.com/
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