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gnomus

Pelican in Ha - First Real Test of Dual Rig

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I've finally managed to put my dual rig together. It is 2 x WO Star 71s and 2 x Moravian G2-8300 cameras. I have a Chroma 3nm filter in one of the cameras and decided to go for a 5nm Astrodon in the other. This is Ha data from both cameras - 8 x 20 minutes from each - for a total of 5 hours 20 mins.

I was keen to see if the rig was functional so combined the subs from both scopes/cameras.  There was some fun capturing the calibration frames.  I cannot make it 'dark' in my roll-off shed, so I prefer to shoot my calibration frames through the night.  Unfortunately, one of my calibration frame runs went well into daylight and I decided to reshoot some darks and the bias frames from that camera.  Of course I got my cameras confused and ended up with 399 bias frames on one and 0 on the other.  I hate getting old.

With the 3nm and 5 nm filters, just a quick stretch ended up showing a reasonable result and so there was less opportunity for me to spoil the image.  However, I am in the process of getting some OIII and SII and so should be able to present a messed-up version in the not too distant future.

Ha_DSE_MTx1920.thumb.jpg.cfb40ae79e523720b0d6279d615e407f.jpg

Edited by gnomus
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Just now, wxsatuser said:

....

The dual rig should do really well.

After all the trouble I've gone to, it better had!!!!  :hmh:

Thanks for the encouragement.

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You will be ok, your previous stuff has been very good, don't see why it should'nt continue.
As to those senile moments, have had a few myself recently, part of the learning curve. :wink2:

Been thinking along the same lines with the Samyang but need a second camera as well. :help:

It's a mad game this AP. :biggrin:

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2 minutes ago, wxsatuser said:

You will be ok, your previous stuff has been very good, don't see why it should'nt continue.
As to those senile moments, have had a few myself recently, part of the learning curve. :wink2:

Been thinking along the same lines with the Samyang but need a second camera as well. :help:

It's a mad game this AP. :biggrin:

Second camera, second set of filters, second focuser, second this, second that, second the other ......  it soon gets very complicated (and expensive).

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Glad that you have the dual rig up and running Steve..... I'd be interested to hear your thoughts on the difference between the 3nm and 5nm Ha. That's a great looking image .... They're great at hoovering up the data aren't they? :)

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Well that worked then! Well done on getting this up and running, Steve. Having run a dual rig system myself, I know only too well how complicated it can be but this image shows that you have it all looking good.

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Well done Steve & Lis: a terrific & beautiful mono image. I look forward the the HST rendition.

I certainly do not under estimate the challenge presented by a dual rig . . . the opportunity it brings for hoovering photons is tremendous and hats off to you both for rising to the challenge.

I look forward to hearing more tales of oh, loads of subs on one camera and none on the other :homework:.

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Excellent Steve, my similar dual setup is still WIP, in the process of making the last alignment adjuster, also acquired a WO Megrez 72 + ff/fr so may be able to have 3 scopes running eventually.

Dave

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39 minutes ago, swag72 said:

Glad that you have the dual rig up and running Steve..... I'd be interested to hear your thoughts on the difference between the 3nm and 5nm Ha. That's a great looking image .... They're great at hoovering up the data aren't they? :)

Thanks Sara.  The difference between the 3nm and the 5 nm is ~£200.....  On a serious note, I have read (and been confused by) a lot of discussions here (but mostly elsewhere) about whether you should go for 3s or 5s.  I formed the impression (maybe wrongly) that if you could afford them the 3s were superior in OIII and SII, but the 3v5 debate was more complex in Ha because of the NII issue.  I only just have a grasp of these things.  I had a set of 3nm Chromas for the first Moravian.  I felt it might be helful to have one extra for the second rig and felt that the 5nm Ha was the obvious way to go.

For those interested I have a full set of Baader LRGBs in both wheels.  I have split my Chroma 3nms so that I have Ha and SII in one wheel and OIII in the other.  The wheel that has the 3nm Chroma OIII is the one I put the 5nm Ha Astrodon in. 

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37 minutes ago, Davey-T said:

Excellent Steve, my similar dual setup is still WIP, in the process of making the last alignment adjuster, also acquired a WO Megrez 72 + ff/fr so may be able to have 3 scopes running eventually.

Dave

I salute you.  I found it difficult enough getting two going at once.  

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Hi Steve

Nice deep image. Dual imaging is certainly the answer in our fickle skies. Just a question? How have you set up your dual rig, side by side perhaps and more importantly how have you managed to align the two scopes?

 

Steve

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17 minutes ago, gnomus said:

I salute you.  I found it difficult enough getting two going at once.  

Well I haven't actually done any proper dual imaging yet, just enough to verify that 2 of everything works happily together.

Been making some scope adjusters to get them all orthogonal and aimed in the same direction, and I'm on the third incarnation of the wiring loom, still got a couple of weeks to sort it before the dark returns.

Dave 

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17 minutes ago, sloz1664 said:

Hi Steve

Nice deep image. Dual imaging is certainly the answer in our fickle skies. Just a question? How have you set up your dual rig, side by side perhaps and more importantly how have you managed to align the two scopes?

 

Steve

Thanks Steve.  The scopes are set up side by side and are aligned with one of these - https://www.firstlightoptics.com/misc/jtd-dual-rig-telescope-alignment-saddle.html

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50 minutes ago, gnomus said:

Thanks Sara.  The difference between the 3nm and the 5 nm is ~£200.....  On a serious note, I have read (and been confused by) a lot of discussions here (but mostly elsewhere) about whether you should go for 3s or 5s.  I formed the impression (maybe wrongly) that if you could afford them the 3s were superior in OIII and SII, but the 3v5 debate was more complex in Ha because of the NII issue.  I only just have a grasp of these things.  I had a set of 3nm Chromas for the first Moravian.  I felt it might be helful to have one extra for the second rig and felt that the 5nm Ha was the obvious way to go.

For those interested I have a full set of Baader LRGBs in both wheels.  I have split my Chroma 3nms so that I have Ha and SII in one wheel and OIII in the other.  The wheel that has the 3nm Chroma OIII is the one I put the 5nm Ha Astrodon in. 

Can you post up a comparison of the 3nm and 5nm?

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Congrats on your dual rig!

It would be very interesting to see a 1/1 comparison between these 2 filters. Since you have identical scopes/ ccd's / imaging conditions a direct comparison makes sense.

Is there a lot of difference in star size and contrast between both filters? Are you autofocusing with these scopes? If so, do you use different focus exposure times?

Thanks,

Pieter

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25 minutes ago, swag72 said:

Can you post up a comparison of the 3nm and 5nm?

 

22 minutes ago, pietervdv said:

Congrats on your dual rig!

It would be very interesting to see a 1/1 comparison between these 2 filters. Since you have identical scopes/ ccd's / imaging conditions a direct comparison makes sense.

Is there a lot of difference in star size and contrast between both filters? Are you autofocusing with these scopes? If so, do you use different focus exposure times?

Thanks,

Pieter

Give me a few minutes and I will do it.  I am autofcussing with both scopes.  One one (the 'older' rig) I had calculated filter offsets, so I focus with Lum and then apply the offset.  I haven't got around to doing that with the new setup yet, so I use 20s bin2 exposures for NB.

Edited by gnomus

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3nm vs 5nm.  I stacked the x 3nm and 8 x 5nm separately.  Then I applied a couple of HT stretches in PI, making sure I applied identical stretches to each stack.  No other processing was done.

3v5.thumb.jpg.a2580ffb19d65f188b41067f02043408.jpg 

 

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Mmm. now that's interesting and potentially money saving!!! Thanks for doing this comparison Steve :)

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No problem Sara.  FYI I did a quick comparison in PI just looking at star size.  3nm on the left again and 5nm on the right.  There seems no question that the stars are a bit smaller on the 3nm (note this is 4:1 zoom).  But my initial reaction was that the 5nm looked a bit more 'contrasty'.  Is that what you are seeing?

stars_size.thumb.jpg.3cbd206ffac89f9b95e6a5fbb51b58ab.jpg

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I certainly agree about the star size. To my eye there seems to be a little more detail in the 3nm..... But not by a lot :) 

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A little more detail, but the 'lighter' parts of the image in the 5nm seem brighter.  Then again, maybe that is what you would expect with equal stretches.  The stars are noticeably smaller even in the posted image, I think, and certainly when you look at them full-size.  However, I would be happy with 16 (or more) of either set of subs.  I am getting only a few minutes more than 2 hours of 'Nautical Darkness', and no 'Astro Dark' at all, here at the moment.  So even with the dual rig, it took 2 and a bit nights to get the above!  (I got a small amount of OIII and SII on the third night, but certainly not enough to post yet.)   

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49 minutes ago, pietervdv said:

.... Since you have identical scopes/ ccd's / imaging conditions a direct comparison makes sense.

....

One potential fly in the ointment, of course, is that the scopes are not 'identical' - the Mk I WO Star 71 (3nm) is 5 element, whereas the Mk II (5nm) is only 4.

Edited by gnomus
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Interesting comparison Steve, if I live long enough to get 3 scopes running one will only be collecting HA so a " cheap " HA filter may restore marital harmony but I think that ship has sailed.

I did idly mention needing a third Star 71 then bought a cheap s/hand Megrez 72 pointing out how much money I'd saved, I think the neighbours ears may have recovered now :grin:

Dave

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Nice work Steve - are you running independent software for image sequence on each then? Interesting data on the Ha.  The 5nm will include some Nii which is extra signal for three when compared to the 3nm, I suspect this adds the additional contrast.  I prefer 5 to 3 having had both.

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