QHY5L-II colour IR filter question

[pluto]

Hi,
I just got a QHY5L-II colour the other day to be used for planetary imaging and guiding. I gave it a quick test the other night while I was out and I noticed that the stars had a soft halo around them. I now know this was because I had removed the IR blocking filter so that I could attach the 1.25" extension, so that it would fit and get focus on my 9x50 gudescope. I also noticed that the thread at the end of the extender will not take the IR filter, seems crazy they don't use the same thread!

So my question is, is there a way to use both the extender and the IR filter at the same time?

[Merlin66]

Hugh,
can you screw the extension into the front of the filter?
Usually if the rear thread fits ( on spacers etc) the front thread fits?????????

[pluto]

Thanks for the reply Ken,
The filter only has a thread on the back to screw into the camera body.
Maybe it's not a standard 1.25" filter size...? I'll have to check when I get home...

[Merlin66]

Hmmm
You'd think if the rear thread fits the camera where the filter came off, then the filter would fit the front thread???
I use a Baader UV-IR filter with threads on both sides.....

[pluto]

That would seem logical, so logical in fact that, although it was pretty easy to see that it didn't fit, surely I must have missed something while fiddling with it in the dark the other night.

Just read the description of the camera on this site:https://www.astrofactors.com/component/hikashop/product/45-qhy5l-ii-mono.html
and it says it includes a "1.25 extension tube / filter holder"
So I'm starting to think the included IR filter has a non standard thread size :shrug:

Worst case it's nothing a bit of electrical tape can't fix ;)

I'll have a look when I get home.

EDIT: the description says the IR filter is 22mm. Is that standard?

[Merlin66]

Hmmm,
Reading the spec for the camera, it says it's already fitted with an IR blocking "window" - that being the case there should be no need for an additional UV-IR filter?

[Merlin66]

The standard 1.25" filter fits a 28.5mm thread (approx) and is 28mm clear.
I assume the 22mm is the built -in IR not a moveable filter??

[pluto]

The built in IR "window" is screwed into the front of the camera body, the black bit at the front of the camera in this pic: http://s4db2ab52c6d7a.img.gostorego.com/802754/cdn/media/s4db2ab52c6d7a/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/q/h/qhy5-ii_2.jpg
If the filter were removed in this picture there would be no black bit at the front and you would just have the coloured body.

The thread on the front of the filter is much too small to take the extension tube so the filter must be removed in order to attach the extension tube to the camera.

[Merlin66]

If it were me, I'd get in touch with the supplier and ask him how it SHOULD work...sounds like a B*&^%$ arrangement.
I think a "std" 1.25" UV-IR filter would fit in the extension.....
(Edit) Reading the web site's sales blurb...it says the 1.25" extension is threaded for filters....not that it takes the filter you've just removed!!!

[Tandum]

The extension tube is something one of the early testers wanted so he could attach normal 1.25" filters to the camera. It would have been nice if the front thread on the optic window was a C thread, but it's not. It took me a while to realise you had to remove the optic window to fit it.

[pluto]

Ahh.. that sounds about right, shame though as I need the extension tube to get focus in the guidescope. I'm going to try and tape the filter to the front of the tube and hope I don't get any vignetting. Failing that I guess I'll be buying an IR/UV block filter. Thanks Robin.
Thanks for your help too Ken.

[Merlin66]

What about using a 1.25" spacer adaptor?
I use one about 25mm long for the Lodestar guide camera on the spectroscope..works well for me and then I can use the parfocal collars to lock the focus...

[pluto]

I'd still need to get a standard 1.25" IR filter wouldn't I?

[Merlin66]

Hugh,
No.
The existing body (with the built-in filter) would just slide into the extension tube.....

[pluto]

Ah cool, that's a good idea, thanks :D

EDIT: like this?: http://www.bintel.com.au/Accessories/Extension-Tubes/Bintel-Extension--br-Tube-35mm--1-25--/1068/productview.aspx

[Jay-qu]

I noticed this on my mono version.. A bit annoying.. But a few pieces of PVC later and I've got a good focus upon my finder ;-)

I think it would be possible to remove the filter and mount it in the extender properly, but I didn't look too closely.

[Merlin66]

Hugh,
Yes, that's the idea.
Still thinking about the original issue....if that black "ring" on the camera has a standard 1.25" thread (hopefully a filter thread size...) on the outside, when it's removed and a std extension (again with std filter threads rear and front) added then the old black ring complete with filter should screw into the extension???
This argument falls apart if the thead on the camera body is a C mount thread.....

[Tandum]

It's none of the above Ken. They out did themselves with this one. None of the threads on the optic window or the camera body are any know standard thread size. I initially bought a c threaded nose piece, that was a waste of $30, I should have measured it better.

There is also an adapter to replace the optic window which accepts C threaded lenses, and they sell the lenses. Tiny complete guide cam maybe or perhaps an all sky camera. Or an Sti wanna be :)

Still, I have the mono in an OAG and so far have always had a star to guide on.

[pluto]

Thanks guys,
I think I'll just get the spacer tube and use the included IR filter.