Any-one using a dual set up?

[carastro]

I have had the idea recently to mount my ED80 onto my ED120 (instead of mounting my ST 80 guidescope), and using a finderguider instead. I have an NEQ6.

I thought I might be able to capture data with 2 scopes simultanously, particularly given the small amount of clear skies we have here.

I've already done the set up, and got the finderguider adapter and this seems to be working well.

However on first inspection, even though the ED80 and ED120 are bolted together (by their mounting rings) and seem to be perfectly parallel, the FOV in the camera does not seem to be the same and I am not talking about orientation. i.e. the core of M42 was bang in the middle of one camera, but right over to one side on the other.

I have only done this once quickly, but I wondered whether there is something I have overlooked, and/or whether I would be better mounting the upper scope into guide rings so I can move the position, or even use one of these adapters:

http://www.firstlightoptics.com/guide-cameras/skywatcher-guidescope-mount.html

Would be interested to hear back from any-one with experience of this.

Regardless of whether I can get this to work for dual imaging, I think this is generally a better arrangement for me anyway, as it saves me having to change the whole set up when I want to use different scopes - I don't know why I didn't think of it before, plus the finderguider is now lower and I don;t have to wait so long for it to clear the POD dome before I can start imaging.

Thanks

Carole

[ollypenrice]

Yves and I tried to do a side by side version with a 14 inch ODK for L and Ha and a 7 inch Photomak for colour with a smaller pixel camera. It proved to be beyond us! The Mesu Mount 200 could handle the considerable mass and guide well but one scope always trailed. We had one of them mounted on a Cassady version of the little adjuster in your link. The Cassady one is a monster... We think that with a setup like this it is vital to get both scopes parallel not only with each other but with the polar axis of the mount, otherwise you seem to get some kind of 'differential cone error' if I can put it like that.

But with smaller scopes I think you'll crack it. Steve Richards has it working and the other person to talk to would be Greg Parker over on PAIG.

You will need some way of adjusting the scopes relative to each other. I think Steve uses the adjuster like the one in your link, or something similar. I tried using guide rings (good ones) once for this purpose with the FSQ85 and they didn't hold still. The other way would be to use shims or oversize drillings but if the adjuster is beefy enough that would be easiest. The Cassady monstrosity would tax an EQ6 on its own!! It's well made, though.

Olly

[perfrej]

I too am thinking along these lines. I think that shimming is the way to go. Get the cone error out of the first scope and then find a landmark far away and sync the second scope with the aid of that. Luckily, my mount reports he cone error so it is easy to iron it our with thin shims.

/per

[carastro]

Thanks Per and Olly.

Not being too technical, can I check I have understood what you say correctly.

Shims: I assume these are wedges of some sort, I was thinking about adding an extra washer behind one of the fixing bolts, could this be what you mean?

cone error: Do you mean focus.

I did think of asking Greg Parker.

Might contact both him and Steve Richards.

Had a hilarious night on Wednesday when i decided to try out the finder guider and the QHY8L for the first time and did not intend to go for the whole rig first time out. But as it was all going so well decided later to add the Atik to the 2nd scope with an Ha filter. Having an Ha filter on I had to move to a bright star for focus, and - oops - that prompted a merian flip. All the cables got tangled up and after some fumbling around had to call it a night.

Will start it all up simultaneously next time and make sure the cables are well positioned. As I won't have to keep changing scopes now, I could perhaps do a bit of fixing down of cables, something I have been reluctant to do before.

find a landmark far away and sync the second scope with the aid of that

Yes I was thinking of doing that, but the trouble is I don't have any really distant landmarkes from where I live as it's all houses and buildings. But I guess it's only for alignment, so I guess the furthest away item will have to do.

Carole

[perfrej]

Shims are thin object that you stack in order to get spacing. I just shimmed my scope to get the cone error away A shim is very thin and has the shape applicable to the object it is to space. A very thin square or rectangular plate with a hole in the center would be a good shim to get a tube ring away from its mounting plate. A washer is a shim, for sure, when used as such.

Now, cone error is how much your scope is off from being perpendicular to the Dec axis. Think of it like this:

You have two tube rings holding your tube to the vixen or losmandy plate. Just for fun, add a washer on the fastening bolt of ONE of them. You scope now points a little off from the Ra, and the angle against Dec is no longer 90°. You have introduced cone error.

/per

[carastro]

Thanks for that clear explanation Per.

I did as you suggested put in an eyepiece in the daylight today and found that indeed the scopes are not exactly aligned. So I have spent part of this afternoon mounting the 2nd scope into guide rings as I thought it would be worth giving it a "go".

Meanwhile I E mailed Greg Parker and recently got a reply from him to say YES he does exactly that, uses guide rings for his other scopes, so hopefully another step forward.

Next step is to orientate the scopes and cameras so the images are framed the same. I'll have to find a way of marking the set up as I need to de-rig from time to time to go to astro camps.

Thanks for your help.

Carole

[laser_jock99]

Getting two scopes pointing the same way is always going to be a bit of engineering problem. Some kind of adjustment will be required on one of the scopes. You'll probably need slotted holes on the outer scope ring and shims to allow height adjustment.

I'm thinking about builing a three scope rig- but it will involve having a custom 3-scope clamp machined.

[Wobbly Bob]

Hi Carole, My main rig is a side to side arrangement. having bought two very nice clamps from Altair Astro, I turned the cross bar verticaly then put a spirit level on the two clamps tightening gently so as to keep them both level. I then scribed a line along each side of the clamps onto the crossbar for future refrance. So now all I need are some brass (or Aluminium foil ) shims either end to adjust the up/down of the scope, hence the referance lines as you will have to loosen the clamp bolts to insert the shims. After a bit of trial and error this should work, it did for me.

Failing that, the jolly old tube rings.

[steppenwolf]

I have a system like this working very well indeed as Olly has suggested. I have a WO FLT 98 with an SXVF-M25C and a WO Megrez 72D with an SXVF-H9 with filter wheel and OAG. These are mounted on a side by side ADM bar with the Megrez 72D mounted on the SW adjustable unit that you linked to. I much prefer this to using adjustable tube rings,

Sent from my iPhone from somewhere dark .....

[carastro]

_{Thanks Bob and Steve. I do have a side by side bar as I used to use my set up this way, but unfortunately it doesn't work for me as I get clash with the pier plate with it sticking out sideways, so I abandoned this method and went piggy back and have had no such problems since.}

_{I didn't realise you were the same Steve Richards as on another forum I chat on - and I've met you (SGL7) and you were very helpful - 2 pitches away - obviously didn't recognise you from your photo - duh.}

_Carole

[Jessun]

It proved to be beyond us!

To the point that you've given up on the idea alltogether?

What makes this setup more prone to errors than a simple scope plus guide scope take on it? It must come down to serious DF in your case Olly and Yves? A cone error is really a pointing error rather than a source for tracking error if I have the mechanics right in my head - until I suppose you have a big gap between the FOV's and one start being affected by atmospherical diffraction before the other does. Once the mount turns all turns with it. Then again you do some serious sub times...

I hope you get it to work Carole, as I some day might try the same - I don't want it to be difficult

/Jesper

[steppenwolf]

_{so I abandoned this method and went piggy back and have had no such problems since.}

If you are going to piggy back (and there's no reason why you shouldn't as it is obviously working for you), I would go with shimming the second telescope. I have done this before and I just bought some cheap 'feeler gauges' for the task.

I didn't realise you were the same Steve Richards as on another forum I chat on - and I've met you (SGL7) and you were very helpful

Yup that's me I'm afraid.......

[ianaiken]

Hi Carole I use side by side with my 100 ED/QHY8L and 80 ED/Atik314L+ on an NEQ6. Like Steve I also use the SW Adjustable on the 80ED and this means I can get both scopes lined up with the star in the middle of the FOV on both. My finderscope with QHY5 I mount in the middle of the scopes in guiderings which means Ican also adjust that so the same star is central.

Right now I may be having issues with flexure when not imaging at the Zenith but it may just be Polar Alignment, I am not too sure. My data leans toward PA. If I ever get a clear sky I should be able to figure that out. This is forecast for Tuesday.

[carastro]

^{Thanks for all the advice every-one. It seems that there are quite a number of people doing this and I have benefitted from this thread.}

^{Many thanks - watch this space. (duh - pun - yuk).}

^Carole

[JamesF]

I am interested to see how you get on. It's an idea I had some time back (not that I'm planning to do it just yet -- it was just curiosity having seen the WASP telescope array on a television programme).

I was wondering about filter wheels. Do you not bother? Do you still use them, but stick with manual ones because they won't change so often? If the latter perhaps you could just use a sliding "tray" rather than a wheel?

And if you made it work with two telescopes, would you then get that niggling temptation to try it with three?

James

[carastro]

Hi James,

I do have a filter wheel - in fact I have 2 - one for narrowband and one for LRGB, but I am new to this and still learning. But with the lack of clear skies I have been doing Ha only and adding it to my old DSLR images which still show more noise than desirable.

I then thought why not get a OSC to use instead of the DSLR.

Then the idea came to me that if I have two imaging scopes and 2 CCD cameras, why not image twice as much data in one go.

Not sure when I will get around to doing more with LRGB imaging. Maybe when we start to get more regular clear nights I guess.

Yes will report back. Don't think I'll be tempted to do a triple set up.

Carole

[ian_bird]

Hi

I use one of these:

https://www.teleskop...pe-bis-7kg.html

Can highly recommend them (I have two).

Will be having a go with my WO FLT98 and WO 72 Megrez (LRGB plus HaII) one fine day (Always assuming we ever get any).

Cheers

Ian

[ianaiken]

I have side by side but I had to upgrade to losmandy and also cassidy tandem bar with tgad which is very useful for aligning scopes. I believe my differential flexure I had is completely gone now I just need to drift align again now that the scopes not moving.

My 10kg weight is right on the end of the neq6 long extension bar but weight does not seem to be an issue for the limited imaging I've done this year.

[ianaiken]

Here's my current setup:

[perfrej]

Uh! Nice electronics cabinet. I like IP-classed stuff and use the same kind of box, IP-65.

Nice job!

/per

[ianaiken]

Uh! Nice electronics cabinet. I like IP-classed stuff and use the same kind of box, IP-65.

Nice job!

/per

Thanks :-) its only taped shut at the moment until I stop fiddling then ill put the screws in

[ollypenrice]

To the point that you've given up on the idea alltogether?

What makes this setup more prone to errors than a simple scope plus guide scope take on it? It must come down to serious DF in your case Olly and Yves? A cone error is really a pointing error rather than a source for tracking error if I have the mechanics right in my head - until I suppose you have a big gap between the FOV's and one start being affected by atmospherical diffraction before the other does. Once the mount turns all turns with it. Then again you do some serious sub times...

I hope you get it to work Carole, as I some day might try the same - I don't want it to be difficult

/Jesper

Sorry to be so late with this reply, Jesper. We felt that something was going on which was beyond our comprehension. No big surprise in my case but Yves is brighter than I am!

Internet research showed that others had also tried and failed with long FL tandems. I don't think cone error is just pointing error. It will translate into guiding error when you guide with one scope which is not perfectly aligned with its partner, and with RA and DEC. I'm out of my depth here but I think that with perfectly parallel scopes and no cone error you could do it. But with reflectors (mirror shift) how easy is that going to be?

Olly

[Gina]

I'm getting set up for dual imaging - see my thread in "Imaging - Discussion" forum :- http://stargazerslou...ghts-and-ideas/

I have a pair of Atik 314L+ mono CCD cameras, a pair of Evostar ED80s and pairs of lenses for widefield. I have done dual imaging in the past with a pair of EOS 1100Ds with lenses. ATM I have one filter wheel - an Atik EFW2 but I'm making a second one myself. ATM I'm using a filter tray for the second camera.

Dual imaging widefield rig construction :- http://stargazerslounge.com/topic/188108-widefield-dual-imaging-rig/

Filter wheel thread :- http://stargazerslounge.com/topic/130744-home-made-remote-controlled-filter-wheel/