Hey gang...I have seen a bunch of converted 8x50's and 9x50's finders but I am having a heck of a time trying to find the right distance to make my little 6x30 finder into a guider...I have a SPC900NC webcam that I would like to hook to it to try it out...its going on a 6" SCT so thats why I wanted to stay with the 6x30 as it already has the guide rings for adjustment...
I found that if I take the front lense out of the scope that it takes around 12" or so in front of my eye to get the lense to come to focus...this is way too long for what I am needing...my assumption is that the rear lense is acting like a barlow to reduce the length needed on the tubes overall length?
Buying a guide scope and the stuff to mount it are not an option as I'm a stay at home dad and the funds aren't flowing (hell there not even trickling)...so I have to use what I have...
can anyone help me...is there a formula as to how far the ccd needs to be away to get it to focus...thoughts on how to go about it?
Tig
welcome aboard.
I have used a 50mm finder as a guide-scope, and it works very well. There is no reason why your 6x30 won't work as well.
In my case I removed the eye lens (it was actually an eyepiece for all intents and purposes) and simply affixed the web-cam in the eyepiece's place. I am at a loss as to why the focus seems to be way longer than your actual tube length, in my case the focus point was quite close to the end of the tube. You will need a fitting in the end of the SPC900, something that screws in and then see if you can adapt that to the inner section of the finder tube. Trail and error, lots of both, but it is something that can be done (better in fact) in the daylight.
Report back with how it goes.
Gary
the webcam does have the Agena Astro adapter in it already as thats what I use for planetary imaging...the outside diameter of the finder and the webcam adapter outside diameter are within a 1/32" of each other so I lucked out there...and both are threaded although the threading is different...
the tricky part is finding the distance the chip needs to be from the lense to get focus...basically find out out if I need to cut or add to the main tube...the good thing with the Celestron finder is that it has a focusing adjustment on the end (objective end) with a lock ring so it doesn't need to be perfect as there is a little room for fine focus...
Just trying to figure out if there is a way to get me close without a ton of trial and error
Then slip the finder out of the rings, and remove the eye end fittings.
Point the finder across the street or at a distant object. Put a piece of lunch paper or similar near where you figure the focus point would or should be. Move the paper until the image is clear, and that is where the focus point is. I guess the chip to front of the web-cam will be about 10mm at most, not including the Agena adaptor. The chip needs to be in the same spot as the lunch paper.
Make sense?
Gary
I got it figured out...I took a TP roll and cut it in half long ways...that way I could tape it tight to the front lense and the webcam...slid it out until it was focused...now I have the length to have the tube made...I'm going to have a tube made that will screw into the Agena Astro adapter and thread the other end to fit the lense...
After I got all that figured out one of my buddies called and said he had a guide scope that I could have...with a focuser on it none the less...its an older model 8x50 that uses the .965 EP's so he's gonna make an adapter to fit the 1 1/4" nose piece of the webcam...
still going to have the tube made though...it will be free so might as well have a backup...
I've had a play with a couple of 8 x 50 type finder scopes to try to get them to work as guiders. There are a couple of problems:
1. The focal length of the objectives on both of those I tried this with both fell just inside the main optical tube. So getting a ToUCam to work required a fair bit of playing around because you are using it as a prime focus camera in effect and so have to get the focal plane of the objective to coincide with the CCD in the camera.
2. The eyepieces these guidescopes have are not any standard size so you can't just pull one out and whack in another eyepiece.
3. The eyepiece assemblies screw away from the main tube but the female thread in the end of the main tube doesn't seem to be compatible in terms of size (diameter) with any of the other bits and pieces I had lying around. So if this is going to work at all, I am going to have to lean on my mate with the lathe to turn up a whole new assembly - perhaps even shorten the optical tube by 25-40 mm to make it possible and try again.
I'd like to her more about your progress and see any pics you have.
I've read a bit about the Kwiq guider in US/canada and seemed interesting to use such a small light assembly. Don't know if you've seen this article? - talks about removing a spacer from behind the objective lens (if you've got one....)
Well I'm hoping the FL of the main scope which is 1500mm (945mm with a .63 F/R) isn't going to really be a factor as the guide scope should be backup...if I get my drift alignment spot on my subs probably will be in the 2 to 5 min range so the guider will be there as a "just in case"...I'm a newbie to AP so I will keep the subs short until I get it perfected...
Rob...the nose on the webcam itself adds 1" so just removing the locking ring behind the objective lense still wouldn't be enough...it needs about 1 3/8" removed from the tube to make it work...
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