Protecting a QHY5

[cybereye]

Hi all!!

I've just taken delivery of a QHY5 (hence the rain in Brisbane) and was surprised to note that there was no protection for the sensor. Does anyone have any suggestions on how to protect the sensor from fingers, dust, etc.? I've used one of the caps from an eyepiece over the 1.25" adapter to keep dust of it at the moment but wondered if there was a better way, especially when using it.:question:

Cheers,
Mario

[Omaroo]

You've done all you can Mario. Put a cap on it... not much to it. :)

When you're using it, it's usually mounted to a scope. :shrug:

[Terry B]

Mine stays permanently on the scope. I use it with diagonal to make achieve focus without the focusser being racked fully out. The diagonal acts like a cap.

[wasyoungonce]

Are you using using a 1.25" UV/IR filter on the nose piece?

[cybereye]

No, I've got no filter and wasn't intending on getting one. I'm still getting the "are you sure this is definitely it for astronomy gear?" questions at home so don't want to buy anything else just yet!!!

I guess I'll just do with the setup I've got at the moment to keep the dust at bay.

Thanks for all the suggestions,
Mario

[wasyoungonce]

Mario..the UV/IR filter helps anti-blooming of the CCD sensor..specifically the UV wavelengths.

Oh..and keeps dust of the sensor. Its common practice to use a UV/IR filter on all naked sensors...unless you want to pick up those emissions.

[Terry B]

I wouldn't use any filter. You want all the possible light as it is a guider not for imaging.

[wasyoungonce]

I thought, and I may be wrong, that UV/IR wavelengths are at different focus point wrt visible light. If not filtered the sensor sees these wavelengths as energy (regardless of the energy being non-visible) thus your focus can be upset...trying to focus on the wrong wavelengths. However we are talking nano meters here.

UV is higher energy wrt visible and this can cause blooming of the sensor..If the sensor was designed for visible light. Though..that said..I don't know what the design parameters of the CCD were taken into account? ...aka was it designed to accommodate this type of wavelength?

I don't think there is any possibility of damage from UV to the sensor so I am probably talking about my semantics of this.

[mill]

The Qhy5 doesn't need a filter when guiding but to keep it as clean as possible i would at least put a ir or uv filter on it (or a clear 1.25" filter).
For guiding you dont have to have the star pinpoint sharp as the guiding software guides on the middle of the star anyway.

[mldee]

I was also wondering if, since you don't really care if the thing is guiding on visible or IR, no filter might be a help in guiding.

BTW, does IR radiation show as visible on the image? I presume so, as the CCD just sees photons. A la Sony nightshot.

[mill]

Ir makes the star blobby (bigger).
Some people make the star a bit out of focus to make guiding better anyway, so without a filter it is bigger in the first place :).
A filter just keeps the dust off the cmos/ccd and is only really required on a imaging camera (because ir makes stars blobby).
Hope this answers some questions.

[JohnH]

I am in the no filter camp - you want max sensitivity to ensure you can always get a guidestar in you fov - hence go for mono and no filters. Mine stays on the guidescope or on the OAG and I have had no dust issues in 2+ years of use...

The focus comment are really not an issue for guiding - in fact many recommend slightly de-focusing for best guide performance as this will reduce noise associated with the centroiding routines by lighting more pixels. If you want to do hi-res planetary or lunar shots then a UV/IR is a good idea....

[DavidTrap]

Are you sure there is no clear glass in front of the chip? I thought these came out of the same factory as the SSAG. There is definitely a piece of glass infront of the chip on my SSAG. You can screw the whole thing apart - the bit which has the t-thread in it comes away.

DT

[mill]

Yes there is clear glass on the chip it self but to make it easier to clean you can put a clear filter in front of that.

[DavidTrap]

To be sure, to be sure, to be sure!

DT

[multiweb]

Yes I'd say so. I have cleaned my QHY8 once with a bit of alcohol and there is indeed a thin piece of glass on top. I'd assume the QHY5 sensor is protected with glass as well. In doubt ask Theo [gama].

[wasyoungonce]

Ahhh thanks for that David. .

[marki]

I use a UV/IR filter on the nose piece of my QHY5. Always manage to find a guidestar even through an OAG. It's easier to clean a filter on the outside then a sensor on the inside.

Mark

[cybereye]

Well, what I thought was a simple question has certainly given me a lot to think about!!! Thanks everyone with your ideas - that's one of the things that I love about this forum, the fact that there is always someone out there who can guide you in the right direction.

Now, if it would stop pouring here in SE Queensland then I might be able to actually try out the QHY5!!! :)

Cheers,
Mario

PS Please don't tell the people at the Queensland Astrofest that I've just bought a new piece of equipment as I'll get the blame for the rain!!!:campfire::cloudy:

[cybereye]

I've just been thinking about the uv/ir filter to fix bloated stars when imaging using a ccd. Am I correct in the assumption that this is only an issue when using a refractor and not a reflector?

Cheers,
Mario

[wasyoungonce]

No not that I know of.

A reflector reflects all wavelengths to a common focus.

A refractor refracts (bends) wavelengths at differing rates according it's glass type (refraction index). APOs are supposed to bring most visible wavelengths to a common focus. Of course it would be neigh impossible to bring UV/IR to the same common focus as visible...they will be close but slightly different.

A refractor glass will attenuate some incident energy (thru reflection & dispersion) as well. A small amount ~3% or less. This is why they use coatings...to reduce reflections..and good glass to reduce dispersion of rays.

[cybereye]

That's what I thought, only a refractor would have trouble with bloated stars as it can't bring all wavelengths to a common focus without the use of some nifty optics.

Cheers,
Mario

[wasyoungonce]

Ahh yes..I should have said ..yes..not no ...a double negative which was wrongly put buy me.:D

If you know what I mean...:shrug:..I think I need a lie down!

[marki]

The aim of the UV/IR filter is to stop these wave lengths reaching the chip and prevent bloating due to the extra energy forcing electrons to flow. It would not matter what the scope type was IMO. If you have shallow wells best to make every photon count and block out what is not useful.

Mark