Dual ED80 setup

[tooth_dr]

Although I was looking for a blue or gold ED80, I managed to get a virtually new black ED80 for not a lot more, which included a SW field flattener and a few other extras.

I sourced a few pieces of 10mm aluminium off a friend and have a selection of dovetails and basic machining tools at my disposal.

Ive read through a couple of threads here on this type of thing and am looking pointers on what to look out for.

Planning a side by side configuration, with two DSLRs and guiding with a modified finderscope guidescope (pictured with normal finderscope below)

Some bracing on top of the rings to be used with aluminium off cuts. Although I’m not sure how I’d go about attaching this?

I plan to align the scopes left/right using a slot in the base plate for one of the rings , and up/down using fine shims from an old set of feeler gauges.

I’ll need to leave room to rotate the cameras 90 degrees for framing, any other tips? The centre balancing point is gonna be closer to cameras and the 40d is about 400g heavier than the 1000d.  I could use my usb hub to offset this difference, thinking of mounting it on the upper aluminium beside the 1000d  

 

Cheers

Adam  

 

 

[Adreneline]

Hi Adam

I used an off-the -shelf ADM dual vixen mount to mount an ED80 alongside a WO-ZS71 with the guidescope piggy-back on the ED80. The problem I had was not just aligning the two main OTAs but getting everything aligned with the polarscope as well. The ADM proved to be a pain to me - maybe mine was a bit off in manufacture. I did not resort to slotting the holes in the ADM but I did try feeler gauge shims as you propose; I also found that to be very difficult and failed to get the scopes to align with each other and the polar scope. I lost several good imaging nights because of the polar alignment error which I could not resolve.

As you intend to start with stock aluminium bar you can build in as much adjustability as you wish and I wish you more luck than I had. I have virtually no machining capility here (or near) so I'm a bit stuck on the front.

In the end I essentially gave up and went with a full piggy-back arrangement. I used one of the ADM saddles (modified) with an SW adjustable guidescope mount (from FLO) to mount the ZS71. I mount the guidescope directly under the ED80 so I know for certain they are aligned with the polarscope. The ZS71 is easily and quickly adjusted.

It doesn't help that my rig needs setting up each time I use it - I don't have the luxury of a permanent installation.

Good luck.

Adrian

P.S. Hope you don't mind - I've attached a couple of photos of my setup.

 

[Timebandit]

 

 

Hello. Peter Drew and Olly are the two gents who could probably give you some advice on the best way forwards to go on this matter. They probably know a lot more about this sort of set up than many of us.

Hopefully Peter or Olly will be along at some point and can shed a bit of light on matters.

Good luck with your project.?

 

 

[sloz1664]

I tried a side by side set-up and eventually gave up. Balancing and alignment being the major factors. I now use a piggyback configuration which has worked out very well.

Steve

[RayD]

There are a number of people here who have dual rigs, @Davey-T has a triple one.  The main thing you will find problems with are alignment, balancing and flexure.  This is not insurmountable but will best be resolved with a proprietary alignment device such as the JTD one sold by @FLO.  Without something like this you will find precise alignment extremely difficult.

You are doing the right thing with a separate guide scope if you plan at any point to use auto-focus as this can also cause issues.

The balancing can also take a little time but, once done, doesn't really change unless you change equipment, so time spent here is worthwhile.  One word of advice here from personal experience is to get your focus somewhere near the point it will be on both 'scopes before balancing.

Good luck with it, looks like a great project so will be interested to see how it goes.

[swag72]

I guess that there are a couple of types of dual rig..... one that tried to match the focal length perfectly and one that doesn't. It looks like you are trying to match the FOV on yours and this is the most tricky I would say. In order to get the two fields matched, initially I went for a system of just using the same mounting gear, thinking that everything would match as would the resulting field of views..... wrong!!! a 1mm tolerance at ground level sure does make a difference many light years into the sky! 

To that end I bought an adjustment saddle, which is excellent to align the two scopes perfectly. I say perfectly as I really don't want to waste any pixels if I can help it.

Then of course there's weight and balance..... I found that quite a bit of weight on the front end, protruding off the cross dovetail really sorted this issue out. I've got a picture of the front weights if that would help to visualise what I mean.

Cables...... nightmare!!! 

[tooth_dr]

4 hours ago, Adreneline said:

Hi Adam

I used an off-the -shelf ADM dual vixen mount to mount an ED80 alongside a WO-ZS71 with the guidescope piggy-back on the ED80. The problem I had was not just aligning the two main OTAs but getting everything aligned with the polarscope as well. The ADM proved to be a pain to me - maybe mine was a bit off in manufacture. I did not resort to slotting the holes in the ADM but I did try feeler gauge shims as you propose; I also found that to be very difficult and failed to get the scopes to align with each other and the polar scope. I lost several good imaging nights because of the polar alignment error which I could not resolve.

As you intend to start with stock aluminium bar you can build in as much adjustability as you wish and I wish you more luck than I had. I have virtually no machining capility here (or near) so I'm a bit stuck on the front.

In the end I essentially gave up and went with a full piggy-back arrangement. I used one of the ADM saddles (modified) with an SW adjustable guidescope mount (from FLO) to mount the ZS71. I mount the guidescope directly under the ED80 so I know for certain they are aligned with the polarscope. The ZS71 is easily and quickly adjusted.

It doesn't help that my rig needs setting up each time I use it - I don't have the luxury of a permanent installation.

Good luck.

Adrian

P.S. Hope you don't mind - I've attached a couple of photos of my setup.

 

 

Hi Adrian

Thanks for your reply.  I really enjoyed looking at your photos, so thanks for posting those.  I figured if I can get the two scopes lined up with a bit of fiddling, then it's only a matter of tweaking the guidescope within the adjustable holder to get it lined up with the other scopes.  I didn't think that it was essential to have the kit all lined up with the polarscope in the mount, just as long as the mount itself was accurately polar aligned?

 

Thanks

Adam.

[tooth_dr]

3 hours ago, Timebandit said:

 

 

Hello. Peter Drew and Olly are the two gents who could probably give you some advice on the best way forwards to go on this matter. They probably know a lot more about this sort of set up than many of us.

Hopefully Peter or Olly will be along at some point and can shed a bit of light on matters.

Good luck with your project.?

 

 

Thanks for your reply Timebandit. I feel that by the calibre of the posters in this thread, that I may have bitten off more that I can chew.

[tooth_dr]

2 hours ago, RayD said:

There are a number of people here who have dual rigs, @Davey-T has a triple one.  The main thing you will find problems with are alignment, balancing and flexure.  This is not insurmountable but will best be resolved with a proprietary alignment device such as the JTD one sold by @FLO.  Without something like this you will find precise alignment extremely difficult.

You are doing the right thing with a separate guide scope if you plan at any point to use auto-focus as this can also cause issues.

The balancing can also take a little time but, once done, doesn't really change unless you change equipment, so time spent here is worthwhile.  One word of advice here from personal experience is to get your focus somewhere near the point it will be on both 'scopes before balancing.

Good luck with it, looks like a great project so will be interested to see how it goes.

 

Thanks Ray.  I have a set of 140mm rings that I was thinking about using to align the scopes, but your linked item is likely to be better.

 

Basically I was gonna stick it all together and see how far out it is. I'm a fairly handy sort of person, used to dealing with small tolerances, so I 'think' I can achieve a result. (I have thought about the likely issues I will encounter over the past couple of months whilst I was sourcing a second scope!)

[tooth_dr]

2 hours ago, swag72 said:

 guess that there are a couple of types of dual rig..... one that tried to match the focal length perfectly and one that doesn't. It looks like you are trying to match the FOV on yours and this is the most tricky I would say. In order to get the two fields matched, initially I went for a system of just using the same mounting gear, thinking that everything would match as would the resulting field of views..... wrong!!! a 1mm tolerance at ground level sure does make a difference many light years into the sky! 

To that end I bought an adjustment saddle, which is excellent to align the two scopes perfectly. I say perfectly as I really don't want to waste any pixels if I can help it.

Then of course there's weight and balance..... I found that quite a bit of weight on the front end, protruding off the cross dovetail really sorted this issue out. I've got a picture of the front weights if that would help to visualise what I mean.

Cables...... nightmare!!! 

 

Thanks Sara.  I am now definitely worried because a) you've tried it and b ) you are in my opinion one of the big hitters in the astroimaging world!

I will consider an alignment device as I can imagine that tweaking a screw in a slotted hole with not be very precise, but just on the off-chance that its close I'll give it a go.

I would really like to see you photos, to see if there is anyway that I can try to minimise additional weight by careful positioning of my dovetail.  I was planning running my dovetail parallel with the scopes, but your post suggested that you placed it perpendicular to the scopes?

 

Thanks

Adam.

 

[Davey-T]

Got mine set up with three home made adjustable mountings for triple imaging, only done two so far though.

The crossbar and three mounting clamps weighs 6.3 Kg.

Just finished one to put the WO110FLT in the middle that weighs 2.3 Kg inc' the dovetail clamp.

Had to buy three longer dovetails to balance the Star 71s with cameras on the back.

Dave

Losmandy clamp for WO110FLT

[Adreneline]

1 hour ago, tooth_dr said:

I figured if I can get the two scopes lined up with a bit of fiddling, then it's only a matter of tweaking the guidescope within the adjustable holder to get it lined up with the other scopes.  I didn't think that it was essential to have the kit all lined up with the polarscope in the mount, just as long as the mount itself was accurately polar aligned?

Hi Adam,

Just a couple of points to add from the experience I had. I tried and tried to get the shim solution to work. I would get thngs pretty well aligned on some star or other and then when I tightened the bolts, no  matter how careful I was, it would all go out of alignment again. It was mega frustrating.

Re. polar alignment I am not qualified or experienced enough to comment but I found that once I had polar aligned I would then slew to a star only to find it was not in the field of view of the any of the scopes! - not even the 176mm guidescope! I typically polar align using just the polarscope. I then slew using CdC and 'sync' several times in the eastern sky - I can't see a western sky from my garden as the house is in the way! My tracking errors are always less than 0.8 so I am happy I get a reasonable PA and the images show no sign of star trailing even at 600s.

@carastrorecommended the SW guidescope mount and used in combination with an ADM saddle it works really well with just the WO-ZS71; I guess it may struggle with anything any bigger.

I really wanted the side-by-side solution to work but it all proved too frustrating for me.

I wish you luck and look forward to seeing how you get on.

Merry Christmas!

Adrian

 

 

[Davey-T]

6 hours ago, tooth_dr said:

 

I plan to align the scopes left/right using a slot in the base plate for one of the rings , and up/down using fine shims from an old set of feeler gauges

 

I tried shims made from soft drink cans originally but it was a complete time consuming failure so resorted to making adjustable mounts.

Dave

[swag72]

1 hour ago, tooth_dr said:

I would really like to see you photos, to see if there is anyway that I can try to minimise additional weight by careful positioning of my dovetail.  I was planning running my dovetail parallel with the scopes, but your post suggested that you placed it perpendicular to the scopes?

 

Here's my weights pictures......... I had a spare piece of dovetail type stuff around and so put that on the dovetail so that I could mount the weights out front so to speak. You can see it close up and in use as well.

 

[tooth_dr]

Thanks again all

@Davey-T I can begin to see that everyone struggles with shims. I’d be a fool to think I can do better ?

@Adreneline I’ve been thinking this too and i figured it will go off alignment once tightened down properly. I wonder if I can accept a small mismatch?

@swag72 thanks Sara. That’s very clear and I’ve plenty of material to similar including dumbbell weights.

 

I am a lot happier now that I’ve got advice on here. 

[swag72]

7 minutes ago, tooth_dr said:

.....I wonder if I can accept a small mismatch......

Only a personal point, but I can't see the point of NOT aligning the frames correctly. I wouldn't want to run a dual rig knowing that stuff isn't lined up properly, otherwise it kind of defeats what you are trying to do.... Double the amount of exposure across the whole frame, not just some of it ... Just my thoughts!

 

[Davey-T]

To move the weight forward I bought longer dovetails, they balance without extra weights now.

Dave

[tooth_dr]

22 minutes ago, Davey-T said:

To move the weight forward I bought longer dovetails, they balance without extra weights now.

Dave

Thanks Davey. I’ve a few spare dovetails, I think I can do something similar and minimise any extra weights needed. Nice engineeeing on the adjustable blocks. 

[tooth_dr]

29 minutes ago, swag72 said:

Only a personal point, but I can't see the point of NOT aligning the frames correctly. I wouldn't want to run a dual rig knowing that stuff isn't lined up properly, otherwise it kind of defeats what you are trying to do.... Double the amount of exposure across the whole frame, not just some of it ... Just my thoughts!

 

 

I know you are right! But I guess I mean a few pixels side or top!

[Skipper Billy]

If you want to borrow my ADM side by side Losmandy set up you are welcome to - its not going to be used anytime soon (my scope is back in Germany for warranty work - could be weeks) - if you want to have a play ??

Its this one. https://www.firstlightoptics.com/adm-losmandy-type-d-series/adm-losmandy-style-dual-mounting-bar.html

[tooth_dr]

3 hours ago, Skipper Billy said:

If you want to borrow my ADM side by side Losmandy set up you are welcome to - its not going to be used anytime soon (my scope is back in Germany for warranty work - could be weeks) - if you want to have a play ??

Its this one. https://www.firstlightoptics.com/adm-losmandy-type-d-series/adm-losmandy-style-dual-mounting-bar.html

That’s very kind of you Billy, I appreciate the offer, very generous!

I have got this, maybe I should give it a go with an extended dovetail on each scope?

 

[tooth_dr]

I decided to go with a Geoptik dual saddle that I had spare, instead of making a new rig. I slotted one end of one dovetail for lateral adjustments (ignore other hole as this was already present in the second hand dovetail), and for vertical adjustments I simply filed the base of one ring in several iterations until it was as close as possible. I’ll try it out and see if it’s ‘close’ enough.

So its now all sitting balanced and ready to go. Next thing to sort out will be controlling two cameras with APT - camera 1 and camera 2, sort out dithering settings for two cameras and whatever else needs done. 

I need to make another dew strap and controller for the finderscope and also make a 12v power supply for the 40d.

Thanks for everyone’s input so far.

Some photos:

 

[tooth_dr]

So far so good. 

[tooth_dr]

Rotation of cameras not quite right, but alignment look fairly close.  I'll try again later.  Scuppered by snow/cloud/mist/beer/wine last night

 

alignment.wmv

[Allinthehead]

Nice work Adam. That alignment looks good. Forecast not looking great until Saturday night. Looking forward to seeing some results from this. For what it's worth i asked the same questions on here when i was doing my dual Samyangs and the advice given was the same. Get the adjustment saddle, so i did and i'm really glad i did, as i'm now going to use the same setup for dual Star 71's too. So alternating the scopes/lens will be made as easy as possible.