Mounting 2 telescopes for imaging

[Anne S]

I'm looking into mounting a 102mm triplet and 60mm triplet with associated cameras on an eq6 so I can double the amount of data acquired. I have a SXH694 mono and Atik 320e colour ccds. What's the best way of doing it? I'm inclined to go down the side by side route as I will need to fix my mount hub pro on top of one telescope, mostly because my dew heater straps are too short to allow anything else.

Photos would be nice! Also what do you use to aim the two telescopes? I have a Skywatcher guidescope mount but my husband has adopted it. Would I be better off going for a better version of that?

The 60mm may well be replaced for an 80mm once I know it all works as the 2 fields of view will match better, so I need the aiming solution to be accurate and strong enough.

Thanks

Anne

[daz]

Side by sides can be tricky to balance, as you need to balance in 3-axis - whereas a piggy-backed arrangement may need more c/weight or be further down the shaft (or both!).

I would also be inclined to use OAG - assuming you have sufficient back-focus to allow this.

Your mounting for both scopes is going to need to rock-solid to overcome any differential flexure..

 

I've not done this in a long time, so others may well have more relevant info - but those are the key issues as I remember...

[AKB]

22 minutes ago, Anne S said:

Also what do you use to aim the two telescopes?

I believe that these...

https://www.firstlightoptics.com/misc/jtd-dual-rig-telescope-alignment-saddle.html

...are the bee's knees for lining one up with the other.

[LightBucket]

36 minutes ago, daz said:

Side by sides can be tricky to balance, as you need to balance in 3-axis - whereas a piggy-backed arrangement may need more c/weight or be further down the shaft (or both!).

I would also be inclined to use OAG - assuming you have sufficient back-focus to allow this.

Your mounting for both scopes is going to need to rock-solid to overcome any differential flexure..

 

I've not done this in a long time, so others may well have more relevant info - but those are the key issues as I remember...

Hmmm, what are the 3 axis, what should it make any difference on an EQ mount.. ?

[Merlin66]

Good balance makes for good results/ performance.

Proper balancing  involves:

1 Balancing the OTA etc in RA against the usual balance weights when the OTA is horizontal 

2 Balancing the length of the OTA (with the usual attachments, camera etc) in Dec by setting the OTA horizontal and moving it back and forth in the dovetail (or adding weight at the front/ rear.)

3 setting the OTA vertically and ensuring that it sits balanced on the Dec axis. Any offsetting of the OTA's Finders etc may require adding additional balance weights.

A final check with the clutches disengaged should allow the OTA to be positioned in any direction without wanting to move.

Hope this helps.

 

[Anne S]

3 hours ago, daz said:

Side by sides can be tricky to balance, as you need to balance in 3-axis - whereas a piggy-backed arrangement may need more c/weight or be further down the shaft (or both!).

I would also be inclined to use OAG - assuming you have sufficient back-focus to allow this.

Your mounting for both scopes is going to need to rock-solid to overcome any differential flexure..

 

I've not done this in a long time, so others may well have more relevant info - but those are the key issues as I remember...

 I've had a guidescope on a tandem set up before I switched to a finderguider, so I've had to balance in the 3 axes. As to an OAG, my SX camera doesn't have enough back focus so I would need to use the Atik. I was hoping to continue using the finderguider as I'm on fairly short focal length.

[MattJenko]

One consideration is how will you control it all in that dithering is going to be extremely tricky unless you just don't dither, just guide and take images independently.

[swag72]

OAG and two scopes .......... Doesn't work and so you need a separate guider. For this scenario imagine if you will that you have two scopes running. As there's no dedicated software at the moment that can fully coordinate two scopes with regards to dither, download etc ( You don't dither either!) then you run one scope as the master, controlling the mount, guiding, plate solve, etc and the other runs as a slave and just takes pictures all night without knowing what it's taking! So in the middle of one of the slaves subs the other scope needs to focus and so stops guiding while it focuses or loses a guide star for a bit and jumps about..... can you imagine whats happening to that slave scope? You've lost a sub.

I've got quite a bit of info on my website about setting up two scopes if you are interested and I also did a thread on the forum to help if needed  

[Anne S]

I'm thinking of piggybacking as a starting point, I'm using an Altair 60mm triplet as the second scope. I still need to check it images OK with a OSC as my 80mm Zenithstar didn't focus the colour channels at the same point! I'm going to be taking the 60mm to the SGL starparty with me. I don't want to lose imaging time at home! I haven't dithered yet as I need to get back to guiding with Maxim DL as I've only just got my mount repaired, it wasn't guiding properly and I've been using PHD2 to see what was happening,

I'm going to just let the second scope take images and put up with losing the odd one. I haven't managed to get autofocus working yet either! That's the next job.

Swag72 - I'll take a look at your site.

Anne

[ollypenrice]

There is no difficulty in balancing side by side. In fact it is easier to dynamically balance a side by side rig because you have simple adustment avaiable right/left on the Dec axis. On a single rig you don't, and dynamic balance needs complex intervention.

We can't dither with our dual Taks because the two scopes are not taking the same sub lengths. Does it matter? I don't find it does. Compared with the benefit of combining data from cameras with entirely different residual noise patterns it matters not a jot.

The dual rig is a formidable instrument. If your two fields of view are similar then you will need a good alignment device as in AKB's link. We use a Cassady but they are out of production. If you have a substantial difference in FOV then you might be lucky and find that the larger FOV entirely overlaps the smaller (or might be bullied into doing so!) and jobs a good 'un!

Pictures...

This outfit really does knock out good data fast. 

(The obsy walls are damp because the outside hadn't been rendered at the time of this pic, and Tom has since pinched back his Tak 60 for his Eclipse trip this year so we're guiding with an ST80, but this is the productive rig of all time in my view.) It is only effectively F4 as an ensemble but it is F4 that just works. I love it.

Olly

[Rodd]

It may be easier to run 2 scopes on 2 mounts--treat each as an individual scope and shoot the same target.  Won't loose any more subs than usual.  I am thinking of doing this.  No balance issues.  Seems the easiest way to me.  You need 2 of everything anyway.  except the mount, but I want to get a mount anyway.  I gues sit depends on what you have and what you need.  Having to buy a mount, scvope, camera, laptop, filters would be like climbing mount Everest.  But if you already have the scopes, and the ASI 1600mmcool is inexpensive, it becomes doable.

Rodd

[carastro]

I have a dual rig and having tried various options of mounting, I found piggy back much the best way to mount it all using a SW Guidescope mount (you need to get that back from hubby!!).  Using the SW guidescope mount so long as I don't alter that, putting the top telescope back into the slot it should be pointing in the same direction each time once you have done the initial alignment. Doing the initial alignment with the SWGuideScope mount is so easy as you have just to turn the two axis. UP/Down and side to side.  

Orientating the cameras - I try to mount them so the chip is horizontal on both scopes and then use the daytime to look at a land-object to check/tweak it all - then I am ready for a night's imaging.  

If you don't move it between sessions even better. 

I use a finder guider on the lowest scope, and you can buy extensions for those dew heaters.  I can't remember where I got mine from, but there might be a thread on here where some-one posted me a link to some when i first bought some where the cables were too short.  Very cheap on Ebay.  I will see if I can find my order on Ebay but it's probably a few years ago. 

This is my rig:

Carole 

[carastro]

Found a thread where dew heater extension cables are discussed with a link to them on Ebay.  HTH

Carole 

 

[Anne S]

On 12/08/2017 at 13:46, carastro said:

I have a dual rig and having tried various options of mounting, I found piggy back much the best way to mount it all using a SW Guidescope mount (you need to get that back from hubby!!).  Using the SW guidescope mount so long as I don't alter that, putting the top telescope back into the slot it should be pointing in the same direction each time once you have done the initial alignment. Doing the initial alignment with the SWGuideScope mount is so easy as you have just to turn the two axis. UP/Down and side to side.  

Orientating the cameras - I try to mount them so the chip is horizontal on both scopes and then use the daytime to look at a land-object to check/tweak it all - then I am ready for a night's imaging.  

If you don't move it between sessions even better. 

I use a finder guider on the lowest scope, and you can buy extensions for those dew heaters.  I can't remember where I got mine from, but there might be a thread on here where some-one posted me a link to some when i first bought some where the cables were too short.  Very cheap on Ebay.  I will see if I can find my order on Ebay but it's probably a few years ago. 

 

Carole 

I’ve just remembered I posted here! That looks a good setup and I’ve got enough dovetails to do it! I don’t have a problem with dewheater cables as I have a Mount Hub Pro stuck to the eq6. I’m planning on setting it up next summer once I’ve finished imaging with my RC scope as I haven’t don’t much with that.

 

Thanks for your help, Carastro.

 

As to controlling both cameras, I’ve discovered APT does it and I’ve also found some software that links 2 computers running Maxim dl so that the secondary computer stops imaging when the main scope needs to do something, The Curdbridge Observatory is the name on the website. My remaining issue is that I have a guidehead so need the software to work with that. 

Anne