Dual Esprit 150 imaging rig

[Jonk]

On 16/01/2020 at 23:06, Davey-T said:

Is that just an artist impression as the plate is restricting a lot of movement, it could end between the focusers and the rear tube rings.

Yes it's a 3d render of my planning. It really helps to get the measurements right and to visualise things.

I won't rotate the OTAs so no danger of the plate being in the way of the focusers, if I do ever rotate to frame then the Star 71s have camera rotators as you probably know. I try and avoid rotating the cameras if possible.

Balance is another issue to combat, I'd rather have it all laid out at stage 1 without having to add weights to balance, but I feel that's likely to be inevitable.

The reason I want to go as close together as possible, is the quest to reduce any flexure at stage 1. I just don't trust the rings, there's too much movement, so I'll draw and make something solid for both OTAs to lay in.

Then the guidescope and large frac can sit on top, again, as part of the same clamp system.

[Davey-T]

 

All the tube rings on my Star 71s have become very loose over time and now I can rotate the scopes without loosening them, need to double up the felt, just bought a SharpStar 150mm f/2.8 HNT which has really rubbish rings that are too small and they have been over tightened and dented the carbon fibre tube, hopefully won't affect the image.

Apologise to T bros for hijacking their thread 😁

Dave

Edited January 20, 2020 by Davey-T

[retret66]

I use ADM on all my tri-scope setup. There is no flex on this one. The middle is fixed, both sides are adjustable via Max-HD pointing saddle.

I use APT for my imaging software. I use a non powered USB hub to connect all devices and then thru a single 16ft USB3 cable to one laptop.

The middle scope is used for dithering, the other two will just wait when the middle finish dithering and repeat.. Advantage of having 3 is  speed

and cost by eliminating EFW and extra filters.

 

 

 

 

 

 

 

Edited January 29, 2020 by retret66

[tomato]

If some’s good...

@Tomatobro has completed the focuser drive for scope #2, no more dashing to and from the dome to manually tweak the fine focus.😎

 

[steppenwolf]

3 hours ago, tomato said:

@Tomatobro has completed the focuser drive for scope #2, no more dashing to and from the dome to manually tweak the fine focus.

Wow, they look very smart indeed. I note that there is a very slight variation in design between the two and wondered why there was a change? To be honest, I'm just being nosey as both look nicely engineered making me curious!

[tomato]

Thanks for the compliment Steve. 

@Tomatobro used a more powerful stepper motor on the first version with a wider tooth belt drive. Lighter Identical motors have now been installed on both units now but he left the wider belt assembly in place on the first one, as he saw no great need to change it. It has been commented by others that they look over engineered, but they are extremely stable and precise in operation even on these large focusers carrying a heavy camera load, which is exactly what is needed from a motorised focuser.

He has also added some graduated degree  rings to assist with focuser rotation, but we are in the early stages of discussion on how this could be automated, we will keep you posted.

[Tomatobro]

With the first esprit Tomato had to set up each time so the criteria was as follows

No modification that would impair the resale value

The scope had to fit into the flight case that the scope came in

Had to work with a Hitec focuser

No backlash

Had to have at least a 60:1 reduction ratio

Be powerful enough to handle large camera/filter wheel/reducer etc

The reduction requirement meant we had to use the 10:1 reduction but the 2mm reduction drive spindle would not handle the belt tension load so the large toothed pulley sits on its own shaft and bearing so imparts no load onto the reduction drive. Drive is imparted by a three pin wheel onto the reduction shaft.

Experiments with smaller stepper motors (two years ago) indicated that the system was underpowered so a NEMA 24? motor was used together with a slightly wider toothed belt. Somewhat overkill but that is what we used. The second version uses a narrower belt and while we were at it the larger motor was replaced with NEMA17 types for uniformity.

Each drive setup cost less than £50 each but does need a couple of days in the machine shop to construct.

I forgot to mention that PTFE bearings, Carbon fibre etc is used to avoid corrosion issues long term

 

 

Edited March 12, 2020 by Tomatobro
more info

[steppenwolf]

13 hours ago, tomato said:

It has been commented by others that they look over engineered,

You cannot over-engineer any component when it comes to AP IMHO !! I love the job you have done and wish I had the skills/bench equipment to do this sort of work myself - as it is, I am limited to drilling vertical holes with a Black and Decker drill in a 1970's Black and Decker drill stand attachment 😱

[tomato]

I think I posted in another thread that after    the scope, mount, obs etc, a good investment is a small lathe and a pillar drill. Once the basic skills are acquired (and both myself and  @Tomatobro are self taught machinists), they can save you £££s in this hobby as well as adding the interest and satisfaction that comes with making stuff.

[steppenwolf]

4 hours ago, tomato said:

a small lathe and a pillar drill.

What pillar drill did you go for - this is something I really could do with! A lathe is probably a step too far as there would be lots to learn and with all my other hobbies (and it is a long list!) I don't have enough years left!!

[Jonk]

https://www.amadeal.co.uk/acatalog/Mini-Lathe.html

I'm going to get one!

[Davey-T]

40 minutes ago, steppenwolf said:

What pillar drill did you go for

I bought a cheap Clarke pillar drill, about £80.00 IIRC real rubbish so you need to spend more than that, may be better off looking at the second hand professional market.

Dave

[Jonk]

24 minutes ago, Davey-T said:

may be better off looking at the second hand professional market.

You can probably apply that logic to most tools.

[tomato]

22 hours ago, steppenwolf said:

What pillar drill did you go for - this is something I really could do with! A lathe is probably a step too far as there would be lots to learn and with all my other hobbies (and it is a long list!) I don't have enough years left!!

All the machine tools are based at Tomatobro’s, the lathe was purchased second hand back in the 80’s for our motorsport activities. It was pretty ancient then but has since made a whole myriad of items, from custom engine and suspension parts, the movement for a long case clock, a fully motorised heavy duty GEM, right up to parts for the current dual rig, and it’s still going strong.
 

The pillar drill was also second hand, the industrial ones are more substantial than the Aldi specials, and that certainly helps, same philosophy as telescope mounts.

Having said that, I have heard favourable comments about a recent pillar drill that was for sale in the centre aisles.

[Tomatobro]

Talking of pillar drills brings back memories of when I collected mine from a guy in the West Midlands.  He was a model steam engine enthusiast and a real eccentric in the mould of Fred Dibnah.  At the bottom of his garden he had a miniature coke fired blast furnace for melting cast iron. After about three hours of discussion we finally got round to the sale of the pillar drill. I am sure that only in the UK folks like this exist.

As I recall he was an accountant and a self taught engineer.

[Jkulin]

On 13/03/2020 at 20:18, steppenwolf said:

What pillar drill did you go for - this is something I really could do with! A lathe is probably a step too far as there would be lots to learn and with all my other hobbies (and it is a long list!) I don't have enough years left!!

I bought one of these a couple of years ago and would be lost without it, I have mode loads of adapters up, but my skills are not up to a lathe as the last time I used one was at school!

https://www.ebay.co.uk/p/699417512?iid=201907962279