>I recently purchased a Televue Pronto as a travel scope and am thinking of
>using it as a guide scope on my LX-200. I will be using a CCD for guiding.
>Is it usable for that purpose?

This is my aim, too. Adrian Catterall (very active British CCD-er) has had
good results with a Pronto and 2x Barlow plus ST4 on his 12" LX200. The
Barlow needs to be rigid: a short one, or 2" is better, possibly with extra
screws fitted. The Pronto can also be used as a piggyback wide-field scope
for 35mm, guiding through the LX200.

>I have a Losmandy dovetail plate on the top of the scope for use with the
>camera adapter.

If this is the "piggyback" dovetail plate it would not be adequate for this
job, and it doesn't accept guidescope rings anyway. The heavier Losmandy
rails are required. As Doc G says, their rings are very good, and Don
Holcombe mentions the Milburn rings, which also look well made. But note
that both these ring sets use adjusting screws which bear directly on the
painted aluminium of the OTA. Even with nylon tips, they will mark, and can
slip, especially when pointed straight up! Another issue to consider with
rings is the eventual distance of the guidescope OTA from the axis of the
main OTA, as this will determine the length of the lever arm and thus the
amount of balancing weight required: smaller rings (i.e. just big enough)
would be best in this respect.

Chris Heapy (see http://easyweb.easynet.co.uk/~chrish/lx200.htm ) also
makes beautifully-machined dovetail bars and rings for this purpose. His
guidescope ring set includes split rings which fit to your OTA, and the
adjustment screws fit into grooves in the split rings, which eliminates both
the marring and the risk of slippage. He has made these to fit the Pronto
(to my measurements) for two of us here in the UK, and they work perfectly.
The split rings are black anodised and look good on the Pronto, and don't
prevent the use of the original Televue mounting ring. If you change your
guidescope at any time, you could have new split rings. I strongly suggest
you contact him: you can actually see my ring set on his website.

Don Holcombe mentions the weight problem. Whatever setup you use, you will
need balancing weights, and these should be of the 2D variety. The Pronto
plus a guider will be about 8lb, and the bar and rings are not light either!
With the correct balancing weights in place, and balanced both horizontally
and vertically, you should not need to worry about the extra weight,
especially if you use slower slewing speeds. Again Chris can supply all you
need, as a matching set, for any size LX200.

Unfortunately I have not yet been able to use my setup for guiding as the
weather in the UK has been foul for the last seven months!

Regards

Dr Nigel Puttick
Great Broughton, North Yorkshire, UK
054.45N 001.15W
"Where observation is concerned, chance favours only the prepared mind"
(Louis Pasteur, in 1854)

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