lewis_riches
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Posts posted by lewis_riches
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Thanks for the responses, guys.
I had considered selling the finder and going for an all-in-one kit. Some are very reasonably-priced. Unfortunately, there are various issues in attaching most of the cheaper kits to the top side dovetail bar of the OTA which, for the sake of brevity, I won't bother going into.
I decided to buy some throw-away used eyepieces and just unscrewing the barrels. This actually turns out to be rather cost-effective if a little wasteful.
As for the finder attachments, I still can't find any details on the thread gauge of the tube, so am taking the vendor's words on trust that the attachments fit the onto the finder tube.
I gave ModernAstronomy a go (which was very helpful - thanks for the pointer, there) and found these:
- http://www.modernastronomy.com/shop/accessories/adapters/sky-watcher-clones-to-t-thread-adapter-for-straight-through-finders/
- http://www.modernastronomy.com/shop/accessories/focusers/t-thread-to-1-25-helical-fine-focuser/
The helical eyepiece focuser is needed to bring the sensor to focus. There are non-rotating alternatives for roughly the same price but not with a female T-thread on the scope side, adding the need for more adapters and thus extra cost.
I'll post updates once it's fully assembled.
Thanks again
Lewis
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After doing a little scanning of the internets, I have seen that this is a rather popular method of obtaining a guide scope. I'm at the very beginning of this and have notice that much of the crucial detail is left out of all of the tutorials I have seen with all the obvious stuff left in. The way I want to do this:
- The kit must function as both a finder and a guide scope (after the necessary dis/reassembly, of course)
- Use a webcam as the sensor placed into the guide scope via a 1.25" eyepiece barrel (that will be glued onto the webcam casing)
- Use an eyepiece adapter in place the finder's crosshair eyepiece (this obviously needs to be detachable if the first requirement is to be met)
- Preferably have some kind of sensor focusing so the primary focus can be left in the same position for both purposes.
So, in order to achieve this, I need to know (but can't seem to find anywhere else):
- The focal length of the finderscope's primary lens (this might determine whether or not it would be worth getting a helical eyepiece focuser to add to the train)
- The thread type at the end of the tube or if there are any attachments I can buy that would allow a 1.25" eyepiece to replace the original crosshair eyepiece
- Where on earth I can buy some 1.25" eyepiece barrels. Seriously, I've looked everywhere! How else could I attach the cam sensor to the guide/finder scope?
If anyone else has tried/is trying this your advice would help immensely! (Tried adding photos but the site says that my 220Kb and 223Kb files are too big! - ???)
Thanks
Lewis
Skywatcher 9x50 Finderscope as a guidescope
in DIY Astronomer
Posted
Not putting an eyepiece in the train for guiding. My mistake, should have said "helical eyepiece FOCUSER". I have updated the comment.
Sounds good. I'll be using a Raspberry Pi for the guiding calcs, operating the mount over GPIO and controlled by an Android phone via Bluetooth but the idea of having a video feed from the guidecam sounds like something I'd like to add. So, this bit is the easy part!
Lewis