Losmandy Tilt adjuster for dual scope rigs advice ??

[kirkster501]

Hi all,

First couple of clear hours in the sensible evening hours for months last night.  I tried dual rig imaging with SGP and it works well.  We have got to get the most of every session in our cloud infested UK skies.  I used a separate guide-scope on top of the FSQ and I turned off dithering.

I centred on Betelgeuse with my longer focal length set up (TEC140 + Atik 460) and then I did the same with FSQ[reduced]/G2-8300.  Unsurprisingly on the second scope the star is not in the exact centre but perhaps 20-30 minutes of arc to one side.  Still, not that bad; I was not expecting it to be in the FoV at all so I may be able to live with this.

However,  I am toying with the idea of an adjustment saddle device that can tilt the lighter scope/camera assembly (FSQ) to precisely match the FoV of the TEC.

I have a side-by-side dual Losmandy saddle device made by Stefan (Astomekanik)  based out of Germany.    This device is as solid as the Rock of Gibraltar.  The continent of Europe will be gone before this side-by-side saddle moves a micron    Currently, one saddle on this side-by-side arrangement is populated by the TEC and the other by the FSQ.    So the adjustment device for the FSQ would need to both have its own Losmandy dovetail (to fit it into the existing Saddle) and it would also need to have its own Losmandy saddle to accommodate the Losmandy dovetail of the FSQ.  In other words, the tilter device needs Losmandy both sides?  Does that make sense?   I really don't want to have to go to Vixen if I can help it.

I cannot seem to find such a Losmandy tilter device.... My questions are:

1.  Is my plan sound?

2.  Any suggestions on a *robust* tilter adjuster device with Losmandy both sides?

Many thanks folks,

Steve

[fireballxl5]

how about this?

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

 

[swag72]

I have a JTD adjustment saddle fixed DIRECTLY in the dual bar..... if you have a losmandy saddle for example the JTD wont fit as it is made in such a way that it doesn't fit on a saddle as there's adjustment knobs that are below the plate itself.

[ollypenrice]

I'm struggling to grasp this! Does the side by side device have built in Losmandy saddles for both scopes?

If not, if, like ours, it is just a flat plate held onto the mount's saddle and intended to carry a pair of saddle plates (one for each scope) then you bolt a normal saddle plate onto the dual bar at one end and a tilt pan adjuster onto the bar at the other. The tilt pan device we use is a Cassady T-Gad like this:

The four holes forming the corners of a square closest to the centre are used to bolt the T-Gad to our dual bar. In profile the device looks like this:

So the dual bar goes under the central stainless steel oval bracket held on with two allen bolts.

Alas the Cassady device is no longer made, your wallet will be glad to hear! This one cost us about 500 euros second hand, from memory. However, FLO make this one:

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

There is surely a huge difference in FOV between your scopes so in one imaging scenario all you need to be sure of is that the smaller field is fully overlapped by the larger. That way you could add, say, colour at lower res to lum at higher. However, in a more sophisticated scenario you might want to frame up the widefiled image and then blend into it high res data for particular areas of interest in the widefield. (Composite imaging as it's known.) In this case you would want to frame the widefield first and the high res second using the tilt pan. I have to say that this sounds like a palaver. I've done lots of dual rig imaging but might shy away from this scenario...

The Tak without reducer works at 2.47"PP and the TEC at 0.92. That is roughly equivalent to binning 2.7 by 2.7 if I have my sums correct. How well will this work? Not sure. I've tried using two-scope data at 1.8 and 3.5"PP and found it tricky to combine them. I found it best to do it in two stages, using the high res lum initially to create an enhanced RGB and then applying the high res lum to that. The fact that I only did it once might say something!

For dual capture would it not make more sense to reverse the cameras? That way the TEC would give you 1.1"PP and the Tak 2.08. This would be much closer to binning colour 2x2 and you'd get a larger FOV from the system working as one. (TEC/8300 gives 1.06 x0 .79 deg  and the TAk 1.59 x 2.47 deg. Still quite a bit of waste but an awful lot less.

Olly

PS Crossed in the post with Fireball and Sara.

[kirkster501]

Ok does this make sense folks?

[ollypenrice]

37 minutes ago, kirkster501 said:

Ok does this make sense folks?

Hmmm, you've got a white line separating the Losmandy B saddle from the dual bar but no equivalent line on the A side. Is this a drawing slip, as I suspect? If the blue Losmandy B saddle can be removed from the blue bar you'd remove it and bolt the tilt device straight to the blue bar as Sara and I do. If the blue Losmandy B saddle is integral with the blue bar then you'd need to put a Losmandy rail in it and bolt the tilt pan device to that rail. You'd need to drill four countersunk holes in the rail to bolt the tilt pan device to it. Perfectly possible.

Olly

Like this:

Oops, I meant new Losmandy rail, not Vixen! Sorry...

[gorann]

I also got the JTD Dual Rig Telescope Alignment Saddle from FLO (after suggestion from Sara) and it works quite well for my dual rig, right now holding an Esprit 150 and an Esprit 100. But since FLO says that it has a maximal payload of 9 kg, I use it for the Esprit 100 and putting the 150 (or your Tec 140) on it would probably not be such a good idea. So I suggest you use it for your smaller scope. However, like Olly, I am a bit confused about your drawing that seems to suggest that the clamp on one side is a solid part of the side-by-side bar.

[ollypenrice]

9 minutes ago, gorann said:

I also got the JTD Dual Rig Telescope Alignment Saddle from FLO (after suggestion from Sara) and it works quite well for my dual rig, right now holding an Esprit 150 and an Esprit 100. But since FLO says that it has a maximal payload of 9 kg, I use it for the Esprit 100 and putting the 150 (or your Tec 140) on it would probably not be such a good idea. So I suggest you use it for your smaller scope. However, like Olly, I am a bit confused about your drawing that seems to suggest that the clamp on one side is a solid part of the side-by-side bar.

Yes, put the smaller socpe on the tilt pan.

Olly

[kirkster501]

Hi guys, the Losmandy saddles are an integral part of the blue bar.  Apologies for the confusion.  The two saddles either end of that bar cannot be removed.

What you depict is what I was thinking Olly: namely, that I could use a piece of dovetail, bolt the tiltable saddle onto that and then affix that into the existing saddle.

Definitely, it will be the FSQ that goes in the tiltable saddle, not the much heavier TEC.

[kirkster501]

My intention is not to necessarily combine the data from the two scopes as Sara does, rather, to make two completely different pictures at a different scale.  So a wide-field of, say, the Horsehead, but a "zoomed in" one too.  Seems ridiculous not to be using both scopes.

[gorann]

Sounds like a god idea (a close up and a wide field on their own rights) and I have been doing that, but then it soon became very tempting to add the high resolution data to selected parts of the wide field (as Olly talked about as composite imaging), and I ending up doing that. I suggest that the next step should be adding something like a DSLR with a Samyang 135 on top of one of the scopes, and triple the data for the night.....

[kirkster501]

26 minutes ago, gorann said:

Sounds like a god idea (a close up and a wide field on their own rights) and I have been doing that, but then it soon became very tempting to add the high resolution data to selected parts of the wide field (as Olly talked about as composite imaging), and I ending up doing that. I suggest that the next step should be adding something like a DSLR with a Samyang 135 on top of one of the scopes, and triple the data for the night.....

I am also thinking of doing exactly that    It's been desperate times this winter in UK.  Dreadful clouds.

[ollypenrice]

Honestly, I think that having a dual rig with entirely unrelated resolutions and fields of view is like trying to have your cake and eat it. The pictures really are entirely different pictures. Just bung the low res widefield on an HEQ5 and do a different picture with it, one suited to the FOV and resolution. Your total photon count will be exactly the same.

Steve, what do you think of my suggestion of reversing the cameras/scopes? That is, to my mind, a potentially productive solution with the gear you have. You'd be making one image fairly efficiently rather than two at single rig speed.

Olly

[gorann]

Olly has a point and that is what I have been doing lately, having the larger chip camera (ASI 071MC) on the Esprit 150 and the smaller field (ASI 1600MM) on the Esprit 100, so relatively similar FOV, collecting Ha with the mono camera and RGB with the OCR, or Ha with both when the moon is up.

[kirkster501]

Thanks chaps.  I actually *want* to collect two different FoV's though.  Don't have any intentions of blending together at the moment.  When I want to do that I'll update to two FSQ106's and sell the FSQ85.  I'm looking into upgrading to a FSQ106 in any event.

[skybadger]

On 28/01/2019 at 12:41, swag72 said:

I have a JTD adjustment saddle fixed DIRECTLY in the dual bar..... if you have a losmandy saddle for example the JTD wont fit as it is made in such a way that it doesn't fit on a saddle as there's adjustment knobs that are below the plate itself.

Mine does. I use Altair tms dual mount and it bolts to one end of the long dovetail .

 

[skybadger]

On 28/01/2019 at 15:41, ollypenrice said:

Yes, put the smaller socpe on the tilt pan.

Olly

I tried that to start. However I recommend that you consider which is your primary pointing scope and whether it is cone error adjustable . Then decide. 

[swag72]

13 minutes ago, skybadger said:

Mine does. I use Altair tms dual mount and it bolts to one end of the long dovetail .

 

Exactly this - It bolts directly onto a dovetail, but won't attach to a saddle.  

[whipdry]

Hi Steve,

Seems this might work Optec libre;

https://www.optecinc.com/astronomy/libra_dovetail.htm

 

Or here for a complete solution;

https://www.admaccessories.com/product/tgad-tandem-guiding-aiming-device-altaz-aiming-device-for-side-by-side-systems/

Peter

[ollypenrice]

8 hours ago, whipdry said:

Hi Steve,

Seems this might work Optec libre;

https://www.optecinc.com/astronomy/libra_dovetail.htm

 

Or here for a complete solution;

https://www.admaccessories.com/product/tgad-tandem-guiding-aiming-device-altaz-aiming-device-for-side-by-side-systems/

Peter

Looking at the first product in detail it looks as if Steve would want to use it upside down.

[whipdry]

1 hour ago, ollypenrice said:

Looking at the first product in detail it looks as if Steve would want to use it upside down.

Yes Olly it does look like it, here's another picture from the website;

Guess it's OK to use upside down. 

 

[gorann]

And the Optec one looks really nice and seems to be able to carry a bit more weight than the JTD sold by FLO. But then it is also more expensive and may have to be imported from the US.

[ollypenrice]

5 hours ago, gorann said:

And the Optec one looks really nice and seems to be able to carry a bit more weight than the JTD sold by FLO. But then it is also more expensive and may have to be imported from the US.

The Cassady is also  a work of genius if you can find one second hand.  It was pure flook that a friend was in a dealer's shop and saw one second hand. He rang me to see if he should grab it for me.

Olly