Skywatcher 9x50 Finderscope as a guidescope

[lewis_riches]

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

[lewis_riches]

So, here's what I'm trying to achieve and what I mean by the eyepiece barrel I'm looking for. This one came straight off an old T-adapter (pictured).

Thanks!

[Macavity]

Maybe one of these might help?
http://www.modernastronomy.com/product-category/accessories/finder-guider-adapters/
Though quite WHICH may take a bit of research?

Personally I got my friend to "turn down" a standard 2" to 1.25" adapter, cut off an 
appropriate amount of finder tube (with angle grinder) and just "whacked it in"!...

But I sense such things DO exist. Might be worth giving Bern @ Modern Astronomy a ring?
(Not sure there will be room for a (unneeded?) Helical Focuser, without a fair bit of surgery!)

Edited February 6, 2016 by Macavity

[MARS1960]

Modern astronomy do and adaptor specifically for this job.

Also you may find this helpful.
https://stargazerslounge.com/topic/71628-diy-50mm-guidescope/

 

 

[Ajohn]

Googling uk skywatcher guider conversion came up with this link

http://www.rothervalleyoptics.co.uk/rvo-finderguider-adaptor-skywatcher-to-c.html

However looking at prices selling yours and buying this might work out cheaper - not sure about mounting but it does come with a decent holder. It might mean sawing of the base of a bracket and attaching it some how.

http://www.365astronomy.com/ZWO-60mm-Finder-and-Guide-Scope-60280.html

They also do the adapter - probably cheaper than the other link

John

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[lewis_riches]

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

Edited February 8, 2016 by lewis_riches

[carastro]

If you are using a computer, you don't need to use an eyepiece as well as the camera for guiding (if I am reading your thread correctly), you can see what the finder is looking at on screen.  Saves a lot of bending and squatting, and saves having to swap over the eyepiece and camera and re-focus.

Got mine from Modern Astronomy, system is brill, finderscope on screen, lovely jubbly.

Carole

 

[lewis_riches]

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

[Ajohn]

As I am slowly collecting bits for AP I bought one of the ZWO one's I linked to. I've a lot to sort out first. May as well mention here as using it will be a bit diy.

Nice and light. Pleased about that as finders can be pretty heavy.

Things lock up nicely.

Having looked through a lot of optics I reckon I can get a good idea using them terrestrially. Nice and bright and very sharp even with a 10mm eyepiece and then a 22mm Vixen. 280mm fl. If the sky ever clears I'll see what stars look like but strongly suspect it will be ok. I was bit dubious when I saw that there were no baffles in it.

It will focus with an eyepiece in it but a televue plossl wouldn't unless it was pulled out about 6mm. Distance around 30m. Another old Vixen was ok. So due to looking how much the focus was sticking out I thought I might get away with a 1 1/4 diagonal in it. No. Might be able to by modifying one but doubtful. There is some scope for modifying by making new bits for it where this could work out - with a lathe. The fact that this one has a rotating focus doesn't seem to be much of a problem to me. It certainly isn't with an eyepiece in it and I can't see it being much of a problem with  a guide camera either.

It's a nice holder with 3 adjusting screws that can be locked on each ring but it sits on a short Vixen dovetail. Small holders for these are available but making one or adapting would be a lot cheaper.

So, wont focus with one eyepiece so I could send it back legit but o/all think I will keep it. I was surprised just how light it was given it's 60mm objective. Pity about the work needed. The focus adjustment could have been longer. May well not be a problem with a cross hair eyepiece but it would benefit from an eyepiece focal length that maximises the field of view, say 32mm giving a mag of just under 9x  the edge of the field  might be a bit colourful using a 1 1/4" eyepiece like this. It's only intended to be used over a small sensor.

Then there is the work needed to make some sort of camera par focal with an eyepiece.

John

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[JimFR]

On 06/02/2016 at 10:44, Macavity said:

Maybe one of these might help?
http://www.modernastronomy.com/product-category/accessories/finder-guider-adapters/
Though quite WHICH may take a bit of research?

Personally I got my friend to "turn down" a standard 2" to 1.25" adapter, cut off an 
appropriate amount of finder tube (with angle grinder) and just "whacked it in"!...

But I sense such things DO exist. Might be worth giving Bern @ Modern Astronomy a ring?
(Not sure there will be room for a (unneeded?) Helical Focuser, without a fair bit of surgery!)

Brilliant! Just found this, wishing to solve a similar problem, but it looks like this is perfect for my needs! (see list of cams in bio 😉 )

[malc-c]

I originally used the adapter for a modified  Philips SPC800 some years back and it worked very well.  Modern Astronomy currently have this listed for £24, and worth every penny.  I now use one of the other adaptors for an old QHY5 camera attached to the finder, which again works well

[Viktiste]

Hi. This is my 8x50 SW finder scope as a guide camera. It works sufficiently for a small (80mm) aperture refractor, Guiding with PHD2 I can take longer than necessary exposures with it on a HEQ5 pro mount.

The pictures shows it in focus with the ZWO 120 MC camera. 

I very much doubt you will get it in focus with the helical adapter. It is not needed anyway, just focus by adjusting the front like you would if using it as a finder scope. A bit touch and go to get focus, but definitely doable.

 

Edit: Oh, just now realized the OP is from 2016 😜  Hope he got sorted out.

 

Edited April 23, 2022 by Viktiste