QHY8 and QHY8Pro Reflections

[Hagar]

Both these cameras seem to suffer from reflection problems between the front IR filter and the CCD. There has been quite a bit of discussion here in Australia about this problem and fixes for the use of things like MPCC etc. I personally don't use a MPCC imaging with a FSQ106 but have managed to rectify the problem I have by removing the front IR filter and adding it to the front of the camera adapter, some 2" in front of the CCD. The results speak for themselves. I have attached 2 images taken on two consecutive nights.
The first image is taken with the stock IR filter on the QHY8Pro and the second with a Baader IR filter fitted to the front of the camera adapter with the stock filter removed.

Bothe images are 6 X 10 minute exposures stacked in IP3 and finished off in CS3. No calibration files used for these images.

Anyone have any better ideas?

[Garyh]

Both nice and deep images Doug! I like them.
Was thinking of getting a QHY8 but decided to upgrade to the 40D. Soon to be cooooled :)
I have seen these reflections in a lot of images done with this and frankly it has put me off abit in getting one.
Would it be possible to replace the optical window with like a baader one.?

[multiweb]

Hey Doug, that shot is corker! :eyepop: Well done. The MPCC is the culprit. True you'll get the reflection like halo if you keep the glass nosepiece but with the MPCC on regardless you'll get the donut reflections offsets on bright stars. I'm now convinced it's an internal reflection within the MPCC. I have had no reflection with the Hyperstar. Not the same shapes anyway. So I reckon it's not a problem with the camera as far as I can tell.

Hope everything is falling into place for you, have a good Xmas, stay safe and healthy and all the best for 2010. :thumbsup:

[Hagar]

I doubt the reflection is the result of the type of filter used but rather the distance between the filter and the CCD. QHY is now going to make a null front for the QHY8Pro to allow this type of setup to be used. You can already get a null extender for the stock QHY8. The biggest problem with the mod will be keeping the CCD chamber free of moist air.
Be aware the Astro 40D does exhibit some reflection problems on bright stars. May be worth contacting EXFSO as he hs had some reflection woes with his Astro 40D.

[allan gould]

Marc
For the same subject (HH) as Doug I get exactly the same reflection and I do NOT use an MPCC - so it has to be the IR filter in front of the CCD. Ill move mine forward like Doug suggests and see if it tames the reflection

[desler]

Doug,



Why the need for the purchase of the Mod. Obviously you've had great success just moving the filter to the end of the nose piece.

Did you have any problems with moist air in your second shot? Which I must admit I am incredibly jealous of! I love it.

Also, have a great Christmas and New Year!


Darren

[toryglen-boy]

Hi Allan

I dont use the IR filter that came with the camera, i never have, and i still get reflections.

:question:

[multiweb]

Hi Allan, that's not what I meant. I don't image with any filter on the nose piece anymore and the reflections I'm talking about (donut shaped) are still present (Alnitak, M45 to name a few). See my shots and Duncan's of the pleiades.

The Hyperstar has a lot more glass surfaces than the MPCC and the camera is very close to it too and I don't get those reflections.

[toryglen-boy]

indeed, i dont knwo whats causing it, i have checked the colimation, and its fine.

The next thing to do, is to flock the inside of the OTA i guess

:shrug:

[multiweb]

Flocking won't help with that but it doesn't hurt to flock your tube. I'm pretty convinced those donuts are star reflections from the CCD glass on to the back of the glass of the MPCC. So it shines back on the sensor as a secondary out of focus star. They will only happen on stars that are relatively central or on axis. Off axis stars will still have the reflection but it is off the field of view. I did extensive testing with and without MPCC, different spacing, etc... when I flocked and aligned the optics on my newt. I doug's case the TAK image circle is so flat and wide that he probably has a fair distance between the camera CCD and the first piece of glass inside the OTA and I suspect that's enough to get rid of any potentail reflections from the CCD glass because it's too far to affect the built-in flattener?

[toryglen-boy]

Hmmm, thats a good call Marc

Maybe some sort of anti-reflection filter between teh MPCC and the CCD face?

:question:

[Hagar]

The QHY8 wasn't a problem as the UV/IR filter screwed into the camera and became the nosepiece but the QHY8Pro has the filter fitted as a fixture in the camera. I removed ine in lots of little sharp pieces.
Moisture can be a problem but there are ways around this also. Just storing the camera in a platic bag wih some desicant seems to be all that is required. The other method which works well with the QHY8Pro is to initially setthe temp to -1 degrees and allow the resident moisture to freeze on the cold finge then screw the cooling to whatever you want. Cooling in't a big problem with the Sony CCD as the noise levels are almost nil one the CCD gets below 0 degrees anyway. These Sony CCD's and cameras seem very under rated in regard to their abilities as a OSC camera. I rarely use dark frames, only if time allows and I feel excited by the image but even then the diference isn't huge.

All the best for you and your family over the holiday period and keep safe on that bike. Keep in touch.

[multiweb]

Well yes that's a good idea. Like an anti reflection coated filter there's such a thing?

[Hagar]

Might be worth talking to your local optometrist, he may be able to get you a plain glass, optically perfect filter with good anti reflective coatings on both sides.

[allan gould]

Doug
How long was the null extender that you used with the QHY8 to remove the reflections?
And a merry Xmas to you and others in IIS

[TheDecepticon]

Hi guys. I too have experienced some of these problems, and as I was following the threads I decided to experiment also. If I dont have a filter down near the chip, it freezes over straight away! I can then open up the camera and put a filter there and the freezing is gone, with out trying to dry the inside of the camera with warm air or what ever. How do you guys stop this from happening? I have tried storing it in a plastic bag with dessicant or with the heater and it still happens.
The only shot I have done that didn't give me a reflection was a Horse's Head shot with the Megrz110 and a Flat II(which I just can't seem to get the spacing right still!) with which I used the original noise piece with no glass>an Astronomik UV/IR>a version of Marc's adjustable spacer(thanks for the diagram)>Flat II>extension>IDAS LPS P2 filter on the end in that order.
I then ended up with blocky stars- is that what is called undersampling?
I would like to find an answer, as I'm getting ticked off and am considering selling the QHY8, or perhaps we need some collective pressure on QHY to help resolve the problem.

[toryglen-boy]

TBH, i dont think its a fault as such, just REALLY bad luck in the way it all functions, when stuck together, and i dont think QHY are responsible.

I think Marc hit the nail on the head, its probably an internal reflection with light bouncing off the shiny, clean sensor front, onto the secondary, and casting reflections of the primary collimation marker through the MPCC

i think the only fix would be an anti reflection filter or coating.

its pretty poor though

:(

[multiweb]

Hi Grey, that looks pretty cool. You got no reflections there. :thumbsup:
Regarding the camera. I leave mine opened in the case with the heatbox all the time when not using it. When I'm going to use it I get a hair dryer and blow warm aie inside and all the tubes, spaces I assemble between the CCD and the MPCC or filters. The body of my QHY8 is also taped around the outside to stop light leaks and air leaks. I also re-siliconed around the plugs to improve it and make it air-tight. Never had frost/dew problems since then, even with the hyperstar camera facing down.


The squares are not undersampling. Not sure what it is.:shrug:

[AlexN]

I had the exact same reflection with my QHY8, I got it when imaging with a a 2 different refractors, my C11, and a newtonian, all with and without flatteners/reducers etc.

I did the same thing that Doug did, removed the standard QHY8 nose piece, put a 2" to T-Thread adapter on it, and a 2" Baader U filter... Instantly cured the problem.

[allan gould]

Thanks for that Alex - will try it out

[multiweb]

Alex I agree you can remove the halo. Did you get these donuts (http://www.multiweb.com.au/astro/M45_f.jpg)ever with your different configurations?

[TheDecepticon]

Hi Duncan, I was more referring to the halo Doug has mentioned, as I have got that problem also. The one caused by the MPCC isn't so bad to deal with in Photoshop.
Thanks Marc, looks like my dear lady is going to be short one hair dryer!!:D I'll have another go!:question:
Thanks for the confirmation on getting rid of the halo, Alex.:thumbsup:

[AlexN]

Ps - Square stars can be undersampling... If a stars light falls onto a very small amount of pixels, (between 1 and say, 5 pixels) you'll get irregular, blocky shaped stars.

[AlexN]

Yes Marc. I got doughnuts like that with the C11.. Reflections That I'd believed were from the corrector plate (as it had the shaddow of the secondary in the reflection...

I'll see if I can dig up an image..

[TheDecepticon]

Thanks Alex, I'll try again and see. Can you expose longer to overcome this and saturate the pixels a bit more?:question:

PS: Perhaps this thread should be moved to Cameras, etc??:shrug:

[multiweb]

On the C11? Wow, that's interesting... Yeah please do post the pic. I'd like to get to the bottom of that. :thumbsup:

[TheDecepticon]

Hi Marc. Ummmm....I had a very quick play with your piccy of M45(sorry if you do really mind), so it's not perfect, but your reflections have gone. Have you tried this before, I'm sure you would have, you seem rather knowledgable?

[AlexN]

Grey - I dont think long exposures would overcome this.. What I can say though from the image of the horse head that you've posted... It looks like the spacing for your flattener is perfect to me.. The stars look very well focused from the center to the edges, what I'm seeing in that image is field rotation caused by a polar alignment error..

Marc, I'll find one.. I have one of M42 somewhere here where I got the little doughnuts from the C11...

[TheDecepticon]

Oh! Really? Ummm....I'll look into that too!:thumbsup: Thanks!

[multiweb]

:eyepop: :lol: Ok. Who needs an anti-reflective coating when you've got decepticon powers. What's the trick? I'm all ears! :prey2:

[AlexN]

Clone stamp tool or spot healing brush are my guess :)

[TheDecepticon]

:P:rofl::rofl::rofl::rofl::rofl:

Yeah, spot healing brush is all. Set the brush diameter to just larger than your reflection and then it uses the pixel info around it to clean up the area under the brush when you click your mouse button.:D
Enjoy:thumbsup:

[Hagar]

G'Day Allan, I just use a 2" Camera adapter. I also blow the camera out with a hot hair dryer and seal it up very quickly. I have just aquired a bottle of Argon gas which I can now purge the camera and adapter with in a plastic bag then assemble and use.



Hot hair dryer is the way to beat it.

[Hagar]

Graham, if the star shape bothers you try selecting all brights stars in photoshop, then, select,modify,expand. enough pixels to select more than just the star. Then select,modify,feather about the same as the expand pixels. Then filter,gausian blur and var the blur to give your star a faint edge.

Should help make the image a little softer. Just remember any sharpening without a star mask will sharpen the stars and may make them appear blocky.

[TheDecepticon]

Thanks Doug, great advice as always!:thumbsup: