SPC 900NC prime focus mod (Request by Sam)

[Sqyff]

This mod was inspired by Dave Evans' blog and his prime focus modded SPC 900NC.

http://coronado-pst....01_archive.html

I have to state before I start that anyone who attempts a mod to their camera does so at their own risk. Please take all static precautions and don't fry your board.

To start you need to dis-assemble your SPC 900NC. I followed the instructions here;

http://home.zonnet.n..._Y/spc900nc.htm

This next part is the most nerve-wracking, removing the camera microphone. This is the round component right next to the CCD, you cant miss it and unfortunately it's gotta go!

The positioning of this microphone will foul any attempt to get the camera to prime focus as the CCD has to be as close to the prime focal point of the scope as possible. The two camera boards do come apart so you are able to get a soldering iron to the mic's backside. Be careful not to damage any other part of the boards when removing this.

Once you have got rid of the mic you can then re-assemble the two boards.

The 'case' for this mod is actually a top from one of those Airwick automatic air freshener containers, which I used because the plastic is quite thin but strong, with the back being a lid from a vitamin container lid.

Making sure you have grounded yourself hold the camera next to the bottom of the lid. Looking from the other side position the center of the CCD as near to the center of the lid as you can. Because the plastic is mostly transparent you should be able to draw a rough felt-tip outline of the area of the lid you want to cut out making sure you have enough room to clear the lens mount on the board, remembering to mark where the small mounting screw holes will be located. You can then cut this area out of the lid with a Dremmel (I found that too fast a speed will start to melt rather than cut the plastic) or similar tool and make the pilot holes for the mounting screws.

You should now be able to mount the camera on the inside of the case/lid using the mounting screws. Dont tighten the screws right down hard as you might damage the camera board, but just enough to make the camera sit securely.You could also cut a hole for the USB lead in the side of the lid. I did mine by making a smallish hole and then cutting a slit down from the edge of the lid to the hole so I could use the anti-pull grommet that was still attached to the lead.( As an aside, I was thinking it might be better if the board was mounted using M2 nylon flat head or recessed screws that are put through from the outside-in with nylon nuts and washers to tighten the board down on the inside.)

I used the plastic web cam adaptor I got with the camera (I bought one of the SPC 900NC,adaptor and filter packages from Morgan Computers a few years back but I think the adaptors are readily available. Just make sure they are plastic otherwise you may have problems modifying them) and got a mate to lathe the ridge off that is used to stop the whole thing dropping down the eyepiece hole. I also got him to shorten the length of the adaptor by reducing the front end by about 1-1.5 cm to stop it from hitting the prism or filter in the eyepiece holder. This is because the CCD needs to be as close to the top of the eyepiece holder as is physically possible. After i had screwed the adaptor back into the camera I measured the gap between the adpator and the front of the newly housed camera and cut a 35mm film container to size. I then cut a hole in the bottom of the container to fit the adaptor through and then cut a round 'slug' of packing foam to fit into the inside of the film camera and when I was happy with the fit made a central hole through it for the adaptor. Basically it was to pack out the flimsiness of the container and make it rigid enough to hold the camera straight. This whole Frankenstein thing was then screwed back to the camera making a nice solid eyepiece tube.

The last thing I did was to cover the entire case and lid with black plastic tape, just in-case of stray light (not pretty I know, but functional).

A word of caution, I went through about four different configurations before I settled for this method and I handled the naked camera more than I should have. Luckily enough I didn't cause any damage to the boards or CCD but I would recommend that you keep any handling to the bare minimum as the SPC 900NC seems to be a more and more rare item nowadays and those that are available are getting pricey.

This mod should be good for PST and Skywatcher scopes that usually require a barlow to get a camera to focus.

I'm not going to say this is the best or only way to do a prime focus mod for this camera but this method has worked for me.

Critique (constructive), observations and improvements most welcome for this mod.

[Sam]

Thanks for posting this. I haven't opened my spc900 since I did the long exposure mod. This looks a good mod so I'll have to give it ago. thanks for the detail and the links it's very useful information.

[Sqyff]

^{No problems Sam, I hope it works for you.}

[malc-c]

Sam, If you search the forum you'll see lots of alternatives for modding he phillips webcam, from simply replacing the case to a full blown long exposure mod