Can't focus webcam

[dannyboy]

Hey guys,

Santa gave me a Philips SPC900NC webcam for Christmas, so I thought I'd give it a try tonight as the soggy British skies have finally cleared.

To try and get a feel for things I started by viewing the moon, but hit a problem straight away - I can't get the webcam focused. When I wind the focuser tube down, the image does almost focus, but then the focuser runs out of travel (I reckon I'd need another 1/4 of a turn of the focuser knob to focus it correctly).

My scope is a Skywatcher Explorer 130PM, and I'm using the SPC900 in prime focus mode (i.e. with the lens removed), with an adapter and IR filter. For software I'm using wxAstroCapture.

Any thoughts would be much appreciated as I feel like I've rather fallen at the first hurdle!

thanks

Dan

[Stephen]

I didn't quite follow : do you need to move the camera closer in, or further out?

Further out is easy, you want an extension tube, or a barlow with the lens removed to give you that additional distance out.

Further in is tricky, you need to somehow get the camera closer to the secondary mirror. This can be done by low profile adaptors, moving the primary mirror up the tube, or low profile focusers.

The last option isn't relevant for a 130 though as there is not a suitable relacement I believe.

[SPOD]

I had the exact same set up.

Are you using the x2 barlow with it or straight in?

Also...have you tried moving the SPC up and down as well as the focuser ?

Kh beet me to it..i'm a sloooow typer.

[dannyboy]

Thanks for the replies chaps.

Just to clarify, I need to move the camera closer in/down, i.e. towards the secondary mirror. Not by much, but that makes it all the more frustrating!

I did try altering the camera position within the focuser, but it didn't really help as the camera was already as far down into the focuser as it can go. Tried with and without the 2x barlow, with same results.

One thing I did notice is that the camera doesn't sit exactly straight in the focuser, because the camera isn't a perfect snug fit (though it does have a 1.25" adapter fitted), and my scope's focuser only has 2 thumb screws to hold EP's in place. These are spaced 120 deg apart, so there's a gap where it could really use a third one.

SPOD - interesting that you had the same setup, I presume it worked ok for you?

[malc-c]

The issue is that the focal point of the mirror is too far down inside the focuser for it to fall on the CCD sensor. Other than fit a low profile focuser (which apparently isn't a option for your scope) the only way to resolve this is to move the main mirror up the tube (closer to the secondary) thus shifting the focal point further out and thus within the range of the focuser. This however isn't without issue, and if you are not confident about undertaking such a task then there is nothing much you can do to resolve the issue.

[dannyboy]

The issue is that the focal point of the mirror is too far down inside the focuser for it to fall on the CCD sensor. Other than fit a low profile focuser (which apparently isn't a option for your scope) the only way to resolve this is to move the main mirror up the tube (closer to the secondary) thus shifting the focal point further out and thus within the range of the focuser. This however isn't without issue, and if you are not confident about undertaking such a task then there is nothing much you can do to resolve the issue.

Hi Malcolm

Many thanks for the info. Unfortunately moving the primary mirror would be a bit beyond me, so with that in mind, all that remains to be said is '******' !

On the plus side, maybe it's a good excuse to upgrade my scope. I presume this kind of issue is relatively unusual, and perhaps less likely to occur with a slightly more expensive scope?

thanks

Dan

[Moonshane]

sometimes a barlow can affect the focus travel. try it with this in also?

[pritc]

Which webcam adaptor do you have?

I found two (normal/low) profiles available.

When I had my SW130P, I needed the shorter one to get focus.

Wayne

[dannyboy]

sometimes a barlow can affect the focus travel. try it with this in also?

Thanks, I tried with the Barlow again and it did help actually, as the focal point was right in the middle of the focuser's range. I still found it tricky to focus perfectly, but this time it was just due to my ineptitude and the difficulty of trying to manually focus without shaking the scope around too much. Definite progress though

[dannyboy]

Which webcam adaptor do you have?

I found two (normal/low) profiles available.

When I had my SW130P, I needed the shorter one to get focus.

Wayne

Hi Wayne

I'm not sure but would guess it's the normal profile, is that how it looks from the pic? Will a lower profile adapter help though, as with mine the whole adapter disappears into the focuser tube, so I'm thinking that the CCD sensor will still be the same distance from the secondary mirror?

cheers

Dan

[SPOD]

Thanks for the replies chaps.

Just to clarify, I need to move the camera closer in/down, i.e. towards the secondary mirror. Not by much, but that makes it all the more frustrating!

I did try altering the camera position within the focuser, but it didn't really help as the camera was already as far down into the focuser as it can go. Tried with and without the 2x barlow, with same results.

One thing I did notice is that the camera doesn't sit exactly straight in the focuser, because the camera isn't a perfect snug fit (though it does have a 1.25" adapter fitted), and my scope's focuser only has 2 thumb screws to hold EP's in place. These are spaced 120 deg apart, so there's a gap where it could really use a third one.

SPOD - interesting that you had the same setup, I presume it worked ok for you?

Yup same set up.

Adapter screwed all the way into the webcam, IR filter fitted and straight into the Barlow, then into focuser all the way down.

I take it you can focus OK without the webcam?.

I do remember however having to up the fps in astrocapture to get a better image.

Other than that' i'm at a loss.

Sorry.

[dannyboy]

Yup same set up.

Adapter screwed all the way into the webcam, IR filter fitted and straight into the Barlow, then into focuser all the way down.

I take it you can focus OK without the webcam?.

I do remember however having to up the fps in astrocapture to get a better image.

Other than that' i'm at a loss.

Sorry.

Maybe that's it - did you always use the barlow? As I found tonight that when using the 2x barlow, the focal point is now in the middle of the focuser's range, so that seems to be the answer. It's still hard to achieve perfect focus, but that's obviously a separate issue which is mainly due to inexperience on my part, I suspect

Yes I can focus fine without the webcam, and collimated recently, so pretty sure the scope's optics are ok. Looks like I just need to make sure I use a barlow when imaging.

[malc-c]

Maybe this might help

Astro Engineering AC624 1.25" low-profile nosepiece to webcam lens thread (ToUcam 840K)

[mallorcasaint]

I had exactly the same setup and it worked fine. Focussing with a webcam is tricky at the best of times and my advice is to practice in daylight on a distant object. Also make sure you have your exposure and other settings set correctly in Sharpcap as this plays a big part.

[dannyboy]

Ta muchly for all the replies - will look into the low profile adapter and do some daytime focusing practice at the weekend

[Kendo_Fuzzy]

Hi,

I have recent got the same scope and converted a Microsoft life cam as per the online guides. I have exactly the same issue.

I purchased the dedicated eyepiece holder for the cam which is really nicely made, I fitted the cam inside but the CCD was too far from the focus point. I ended up fitting the cam into an old 35mm film pod and inserted this into the focusser, this gained my about 3-4cm closer to the focus point and works fine. If I use the purchased holder with a barlow its fine. I was happy with this until I just got a Tmount in the post. I unscrewed the central part of the skywatcher 2inch to 1.25inch adapter , screwed this to the tmount and fitted it to the scope. Guess what?.... exactly the same issue. I cannot get the camera close enough to the scope. I scewed the T-mount to the barlow and again it works fine.

I appears to me that this is a common problem with the SW 130p

Any advice further to whats been posted here so far would be appreciated

Fuzzy

[themos]

I couldn't reach focus on my 4.5 inch reflector when I put the DSLR in. I took out the mirror end and sliced about 2 inches off the tube, then reattached the mirror end. Brutal but it worked.

[Kendo_Fuzzy]

Ouch !!

[Sully]

Try these settings, I've been having pretty much the same problem but seem to have it now and managed to get decent results:

[Philips SPC 900NC PC Camera]

Frame Divisor=1

Resolution=640x480

Frame Rate (fps)=10.00

Colour Space / Compression=YUY2

Exposure=-7

Brightness=48

Contrast=23

Saturation=-3

Gamma=0

ColorEnable=255

BacklightCompensation=0

Gain=32

See thread

http://stargazerslounge.com/beginners-help-advice/171612-spc900-focus.html

Cheers

Sully

[dannyboy]

Thanks Sully, these really helped actually. Managed to get some (by my standards anyway) reasonably good shots of Jupiter and the moon just now. As good as I think I can expect with my little 5-incher anyway

[mallorcasaint]

There is no problem with the SW 130p and the Phillips webcam, It should focus ok without anything other than the nosepiece inserted into the focusser. There is however a problem when using a DSLR.

[davecv]

Hi - I had this problem with an SPC900NC and a stargazer dobsonian.  The focus ran out and the camera could not get close enough in.

I took the eye piece adapter out of the camera and after carefully covering in masking tape I filed / ground down the lip on the eye piece until it was able to drop down inside the focus tube but there was still enough eye piece to grip with the locking screws.  I the original camera case got in the way so I dismantled it and put the camera in a flat project box.  It solved the problem. 

As this process produces a lot of aluminium filings and dust make sure the masking tape covers the internals up.  I also dusted everythign off and gave the finsihed part a quick spray of black paint not only to make it look neat but any extra dust was takeing into the paint befor the masking tape was taken off.

Dave. 

[Alienfox]

I have been working on this problem with the Sky-Watcher 130, you just cant get focus using a webcam or SLR even with a barlow, the only answer I can seem to find is, move thw mirror up the tube 40mm or remove 12mm from the focuser giving you more movement inwards.

[D4N]

I could achieve focus on several webcams through the 130P, DSLR prime focus does require some modification though.

Note that if you move the primary mirror too far it can cause loss of effective aperture as some of the light cone will go past the secondary instead of reflecting off of it.

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