Exploere 200P R&P upgrade to Crayford

[Glider]

I've got the Skywatcher Explorer 200P with R&P focusser, love it. I've bought it a 'direct replacement' Skywatcher Crayford focusser for Christmas because its been so good all year.

However, now everything is on the kitchen table in front of me the problem is obvious, the central hole is 6mm too small all round and the 4 mounting holes need moving out.

I've had a chat to the guys up at Rother and it seems 'direct replacement ' is not that. Rework is necessary. We even discussed chopping everything that I had in and getting a new OTA with a Crayford, but it turns out the replacement is still better than the standard, and still requires rework to replace it!

I'm very nervous at the thought of hacksawing away at the aluminium tube.

Obviously you must strip everything out of it before starting.

Has anyone done this before? How did you do it? Did you use any special tools that make it easier?

Help!

[John]

I think I'd be very cautious before doing that upgrade - I'd have to be convinced that the standard focusser could not be made tolerable with a strip down and re-grease before cutting the tube. You will need to remove the primary and secondary mirrors and their cells and the spider holding the secondary.

The problem is that, once you have started, there is no way back. It's a shame they claim that it's a straight replacement when obviously it's not.

I may be being pessimistic - I've not much faith in my DIY abilities !.

John

[Rusty Strings]

The tube is steel not aluminium (try a magnet on it) which will make it a bit harder to work. You could use a hole saw suitable for cutting sheet steel by sandwiching the tube between two pieces of ply. The inner piece would need to be planed to fit the curve of the tube. Then bolt the two pieces together using the existing R+P mounting holes. mark the centre, again using the same mounting holes, fit a support strut across the tube diameter to prevent it distorting as you apply the drill.

As John says you will have to strip the tube down, so while it's in that state you could flock it as well.

John

[PhoenixRising]

Painful stuff. Ive seen the upgraded focusser and its alot nicer than the standard one. I too was put off by the diy work needed. Is there not a straight forward(ish) replacement focuser for the 200P?

[topdude]

Be brave

It is not difficult to fit a replacement focuser but you need to be comfortable with your DIY ability.

I recently fitted a Crayford to my 130PM, it is a bit daunting before you start as there is no going back but the reward is worth it

I did not remove any components, i just worked very carefully so as not to damage either mirror. The steel tube is quite tough to cut / file but it is possible.

A good collimation later and the Crayford is a pleasure to use

If you want a more detailed description just let me know.

[stev74]

I'd also be interested in any replies as i'm looking to do the same upgrade. I'd narrowed it down to 2 -

A single speed Crayford on FLO that says it's a direct replacement Skywatcher - Skywatcher Newtonian Focuser 1.25/2 inch

An Antares Dual Speed Crayford on RVO - Antares Dual Speed Crayford Focuser New TypeTelescope Accessories | Rother Valley Optics

Most of the dual speed Crayfords that I've seen advertised on different sites say for newts over 9" but this one says newts over 7".

Maybe if you could post a link to the model that you bought it would help people giving any advice and tell me which one not to buy. I was planning to give both shops a call before ordering for some extra advice. I would probably be happy to drill some extra holes to bolt the new focuser on, but I'd not be happy to attempt widening the central hole. I think that could end up a bit of a mess if you didn't know exactly what you are doing.

As John says you will have to strip the tube down, so while it's in that state you could flock it as well.

That was my thinking so I've already got the Proto Star flocking paper from here - Telescope Parts UK There's also a guide on the site on how to do the flocking. It also includes stripping everything out, the first half of which you'll need to do to replace the focuser anyway. This guide is a bit more detailed - Flocking a Newtonian - How To and should give you a good idea about stripping the focuser out.

Lastly there's astro babys guide for collimating once you put it all back together again which you probably know about but just in case. Astro Babys Guide to Collimation

I hope some of this info helps and hopefully some of the advice you get from others will help me too!!

Oh I almost forgot I was thinking about going the whole way and cleaning the primary mirror as well with the help of this guide -

Wow I think I'll be busy but, well, I need to be doing something during all the cloudy nights.

Cheers

[Rusty Strings]

I fitted a moonlite dual speed jobby to my explorer 200p and that was supposed to be a direct replacement but the mounting holes on the tube had to be enlarged slightly so that four of the many available holes in the new focuser would line up. Only a minor irritation compared to Gliders problem but the central hole in the tube doesn't have to be staggeringly acurate or round as long as the mounting holes place the central axis of the focuser tube above the secodary mirror in the correct place, indeed a small amount of up/down/side to side play may be desireable to get it just in the right place before tightening those fixings.

John

[PhoenixRising]

Ive tried the Antares Focuser and it is supersmooth and very firm. It isnt a direct replacement however.

[PhoenixRising]

Yup, just had a scoot round for you and it appears that the Moonlight Focuser is the one to get for a "direct" replacement. The holes need widening slightly but this is alot less hassle. Heres a link to Astrobabys site where shes put up a pic of her 200P with this focuser on and an explanation. (Nice site btw Astrobaby). Hope this helps, Ill be doing it at some point.

[PhoenixRising]

oops, heres the link:

Review of the Sky-Watcher 200/HEQ5

[Mike_F]

I'd also be interested in any replies as i'm looking to do the same upgrade. I'd narrowed it down to 2 -

A single speed Crayford on FLO that says it's a direct replacement Skywatcher - Skywatcher Newtonian Focuser 1.25/2 inch

Mmm, but it's clearly not a direct replacement for all 200P OTAs..

An Antares Dual Speed Crayford on RVO - Antares Dual Speed Crayford Focuser New TypeTelescope Accessories | Rother Valley Optics

Ah yes, the Antares focuser, also branded as a SkyWatcher unit elsewhere..

Put it this way, that was my first option, and I acutally fitted one to my OTA courtesy of FLO - but I didn't like it and paid the extra for a Moonlite instead.

Disclaimer: I'm not "dissing" this product in general. My total sample size is 1.

I found that the unit I looked at wasn't brilliantly made. It's collimation was inconsistent through the focuser travel - and the extendable drawtube introduced a great deal of slop into the assembly.

Most of the dual speed Crayfords that I've seen advertised on different sites say for newts over 9" but this one says newts over 7".

It does actually fit the 8" OTA - just.

Maybe if you could post a link to the model that you bought it would help people giving any advice and tell me which one not to buy.

It was the "Direct replacement" model, as now fitted to the newer 200P OTAs as standard. (This one: Skywatcher - Skywatcher Newtonian Focuser 1.25/2 inch )

HTH.

Mike_F.

[Astro_Baby]

Baader do one thats supposed to be a direct replacement. I decided to go for the Moonlite having seen Astronuts one.

The Moonlite needed two of the screw holes widening slightly. The Moonlite is a lot more expensive but its very good.

Cutting a hole in the tube - you'll need to strip out the spider for a start. You could get away without taking the primary out byt stuffing a towel down the tube - make sure it doesnt contact the primary. After you have done the work hoover the tube out throughly and keep the tube horizontal or facing down when working on it.

The steel wall of the tube is quite thin so you could grind it down with a grinding burr on a drill or even file it out with a half round file.

I'd agree though - if it were me I'd fit something else rather that start butchering the tube up. Failing that find local engineering company who can do it.

ps - theres a review of my Moonlite here http://www.astro-baby.com/reviews/moonlite_focuser_review/moonlite_focuser_review.htm

[Astro_Baby]

pps should have read the post closer - the R&P focuser may well have too small a hole even for the moonlite.