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Fork mount or German for video?

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#1 maroubra_boy

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Posted 27 February 2013 - 06:52 PM

Hi all,

I'm looking to make a rig dedicated to video astronomy. I have a couple of options for a mount, either the fork from an SCT or a German style (no more sophisticated than an EQ3 with an RA motor).

The gear I'll be using with it will be photography lenses (16mm to 300mm) and a couple of scopes (80mm f/5 refractor & 114mm f/4.5 reflector) coupled to my GSTAR camera.

Anyone have experience in this line of things?

Many thanks,

Alex.

#2 GlennLeDrew

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Posted 27 February 2013 - 07:41 PM

I vastly prefer forks. I've been tempted to make a fork to replace the Dec assembly on my EQ-5 mount, as I don't use a Dec motor anyway. The meridian flipping and image flipping (with amp glow swapping corners with respect to north) are annoying!

A more recent acquisition of a late-90s fork-mounted C-8 (with better tracking!) might put paid to the former notion. In this case a simple mounting plate to bridge the Dec trunnions would be a doddle to make up. Indeed, I did just that for an older C-8 fork mount back in '87, for my first Sky & Tel astrophoto workshop out at Yulara (Ayers Rock).

#3 maroubra_boy

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Posted 27 February 2013 - 08:12 PM

Thanksfor that Glenn.

Any pics of that rig? My initial inclination is to a fork, but I'm open to other options.

#4 GlennLeDrew

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Posted 27 February 2013 - 10:02 PM

That old fork mount with bridging plate changed hands some twenty years ago, and I never did take any pics of it. The plate was simply a piece of hardwood, the ends being curved to fit the trunnions. It was at most a half hour job.

#5 Lorence

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Posted 28 February 2013 - 08:37 PM

Anyone have experience in this line of things?


I've got video cameras on 20mm and 70-210mm Canon FD lenses and a Celestron 750mm f5.6 telephoto version of the old C5. I'm in the process of putting an old Mintron video camera on a spare Meade 10" fork mount. It will replace a webcam used to monitor the inside of my observatory. I'm going to try using this camera and mount as an Aurora and meteor camera as well. Not sure if the Mintron is up to it but if the the concept works I'll just have to get another Mallincam.

#6 nytecam

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Posted 01 March 2013 - 11:13 AM

Hi all,I'm looking to make a rig dedicated to video astronomy. I have a couple of options for a mount, either the fork from an SCT or a German style (no more sophisticated than an EQ3 with an RA motor).Alex.

Must admit the GEM has always been a bit of a mystery in that the counterweight is almost as heavy as the scope tube itself which does little for portability! GEMs are versetile whilst forks designed for specific scopes but still my favourite mount. My old DIY BIG scope-cluster had tines 3ft apart but something more modest will adapt :p

#7 maroubra_boy

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Posted 03 March 2013 - 09:41 PM

Thank you all for your comments and suggestions. I've been able to get my hands on an old Meade 8" LX5 mount that I've made a video platform for. The pic below shows it fitted with an 80mm refractor and a 50mm finder-come-guide-scope. I'll look to shortly make the platform accept my 114 f/4.4 reflector. I'm pretty chuffed with it :)

I just need to make a plywood wedge to take the mount. Going to be a busy couple of weeks as I want to have it up and running at a public viewing mid March.

Alex.

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#8 maroubra_boy

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Posted 03 March 2013 - 09:42 PM

Another view.

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#9 mclewis1

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Posted 04 March 2013 - 11:00 AM

Alex,

That's a very interesting setup. It appears that you've been careful to ensure the altitude axis is oriented correctly with the optical axis of the primary scope.

I'll be very interested to see how accurate your goto's are with this setup (I have a NS11 GPS setup just sitting in a box ... I'd like to do something similar to what you are doing).

#10 maroubra_boy

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Posted 04 March 2013 - 04:38 PM

Mark, there's not an encoder or CPU within earshot here. Like your signature says "just because I can...". I choose not to. This rig uses just its RA motor. It doesn't need go-to with a 50mm finder.

The purpose of making this rig (be it with a fork or german mount) is to show novices how accessible astronomy is. Imaging isn't my niche in astro. I just use video as a tool at urban star parties. By making the rig as simple and as effective as I could, I hope to show newcomers to astronomy that it doesn't require particularly sophisticated gear. The choice of scope used here is a part of this too. To use an expensive go-to system that is out of reach of most kids, for me is counter productive to what my aim is. That I'm using a fork that was destined for the scrap heap is exactly what I was looking for too. I know that there are a lot of fork mounts that are begging to be put to use again, :).

#11 GlennLeDrew

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Posted 04 March 2013 - 05:31 PM

So evocative of my own adaptation on a C-8 fork for wide angle and telephoto photography.

#12 maroubra_boy

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Posted 19 March 2013 - 07:13 PM

Well, I've now got myself two video rigs that I can use with this fork platform. One with an 80mm f/5 refractor and another with a 114 f/4.4 reflector, :)

I made myself a plywood wedge from 12mm ply that I had surplus from a previous project. I screwed and glued two sheets of ply for each element of the wedge and had the kids paint it for me before I varnished it. Gee I just love their unabashed use of colour! The wedge I can adjust for different latitudes too. Very solid and vibrations die much quicker than they do in my old C8 and its Celestron wedge.

Below is a pic of the 80mm rig just after first light with my GSTAR camera. I never imagined that such a little scope could have such punch! The nebulosity of M42 and Eta Carina was amazing, and colourful. Omega Centauri was ablaze in a ball of resolved stars. I also managed to pick out the Sombrero, M83 and Centaurus A - all faint but just identifiable. Just wonderful :grin:

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#13 maroubra_boy

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Posted 19 March 2013 - 07:23 PM

A couple of nights ago I finally got around to attaching my 114mm f/4.4 reflector to the same platform. I have been thinking about a 130mm reflector, but after seeing what this little tin can do, I think I'll forget about a 130 scope.

WOW! is all I can say about the images from this fellow. I pulled up the same targets as with the 80mm, but what a difference some more aperture makes. This time I only went for Centaurus A, and there was such a difference in the size of the galaxy's extension. Even its central dust lane was showing details. Just amazing :)

Reaching focus was a concern for me at the start, but a dumb luck would have it, the image was focused with the drawtube rucked in all the way. I haven't tried using a focal reducer, but I don't think I'll be able to reach focus with the current set up without changing the focuser.

One thing that really appeals to me with this Newtonian is that the camera and focuser are never located in between the tynes of the forks as the can be with an SCT and a refractor.

Two excellent rigs - which one to use??? This is a happy problem to have

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#14 Dragon Man

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Posted 21 March 2013 - 08:25 AM

Alex, looking good mate.
That reflector sits nicely on the Fork. :)

#15 buddyjesus

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Posted 25 March 2013 - 02:01 AM

cool re-use of the fork mount.

#16 labmand

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Posted 05 May 2013 - 02:09 PM

Found this thread while looking for fork mounted refractors.
I have a Celestron Ultima C8 that has not seen light in a
few years and was thinking that it would be nice to try
deforking the sct and mounting 1 of my refractors using a
mounting plate as you did. The mount and tripod is massive,
has drives etc. Was looking to mount the sct on a GEM but
just not sure if I should get another goto or pick up a eq
with drives only, but this setup may work, maybe a dovetail
could be added to the plate so I could slide the sct back on
it also nice job and any more advise is appreciated. thanks

#17 nytecam

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Posted 05 May 2013 - 04:11 PM

A couple of nights ago I finally got around to attaching my 114mm f/4.4 reflector to the same platform. I have been thinking about a 130mm reflector, but after seeing what this little tin can do, I think I'll forget about a 130 scope. WOW! is all I can say about the images from this fellow.

Yes - it's amazing how a small scope + all important cam punches way above it weight. Just read on a UK forum "Can I see M51 from town with a 6" scope?" and they struggle to reply positively. Your setup would eat M51 in seconds - if it wasn't below your horizon maybe :o. Keep up the good work :grin:

#18 maroubra_boy

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Posted 15 May 2013 - 06:31 PM

Dave, an new German mount with goto would be the cheapest option over a whole new scope & mount.

The trickiest thing with making the platform to fit between the forks is getting the spacing right. The mount I modified had a fair bit of play in the mounting plates, & I found my first lot of measurements was a little small & I had to pack them with a couple of washers.

What will make things somewhat easier for you is that you have the OTA that you can take measurements from to be more accurate.

Nytecam, M51 comes just above the horizon for me in Sydney, but too low to overcome the city's sky glow. I need to be out bush to see it.

I've got a high school viewing night coming up next month. I'm hoping to set up this rig again in the next couple of days to plan a program of objects. There's going to be several scopes out that night with some four fellow photon junkies on duty. I'd love to be able to show the kids the same object with a scope & this video rig side by side. The kids can then see what can be achieved with both instruments & not a whole lot of money. Might inspire to school to purchase a scope too. Might start a new thread to detail the experience of the night.






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