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Imaging with the 130pds


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Looks pretty nifty.... Im impressed!  Its much the same thing for bashing a 130p into imaging.

However, you will definitely need to make a cover for the bottom of the tube now, because there will be a substantial light leak around the edges of the primary.

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9 hours ago, Uranium235 said:

Looks pretty nifty.... Im impressed!  Its much the same thing for bashing a 130p into imaging.

However, you will definitely need to make a cover for the bottom of the tube now, because there will be a substantial light leak around the edges of the primary.

Thanks Rob. That was my inspiration although the PDS cell is a better design which made it a lot simpler.

I can get focus and the draw tube isn't intruding at all. I probably have 5mm out focus left at most. Cover is my next job along with a third locking screw in the focuser collar.

Noticed some coma in this 30s of Archturus. What are your thoughts on it?

Disappointing. I shouldn't need to play around with spacing surely?

Single__2016-01-28_05-11-30_0003_ISO800_

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5 hours ago, richyrich_one said:

Thanks Rob. That was my inspiration although the PDS cell is a better design which made it a lot simpler.

I can get focus and the draw tube isn't intruding at all. I probably have 5mm out focus left at most. Cover is my next job along with a third locking screw in the focuser collar.

Noticed some coma in this 30s of Archturus. What are your thoughts on it?

Disappointing. I shouldn't need to play around with spacing surely?

Single__2016-01-28_05-11-30_0003_ISO800_

That looks more like internal reflections than coma to me.

Welcome to the world of worrying about second-order effects ;)

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37 minutes ago, richyrich_one said:

Are you referring to the uneven halo (only way I can describe it) around Archturus itself?

I was. But now I had a chance to look at the full size image, I agree with you that it looks like a touch of coma. Sorry about that.

Have you got the spacing between the CC and the sensor correct?

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5 minutes ago, Pompey Monkey said:

I was. But now I had a chance to look at the full size image, I agree with you that it looks like a touch of coma. Sorry about that.

Have you got the spacing between the CC and the sensor correct?

No worries. :smiley:

Camera+T-ring+MPCC

What could possibly go wrong? 

I'll have to double check everything. 

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How many of you are successfully using smaller mounts with the 130pds?

I can afford a 130pds but not a new mount which means using it on my exos2 (EQ5). Now everyone seems to say that the mount is the first thing you must get right and I'm not going to disagree with that but I can't afford an HEQ5 right now. So how successfully can one use an exos2 (eq5) / 130pds combination?

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On 28 January 2016 at 07:18, richyrich_one said:

Thanks Rob. That was my inspiration although the PDS cell is a better design which made it a lot simpler.

I can get focus and the draw tube isn't intruding at all. I probably have 5mm out focus left at most. Cover is my next job along with a third locking screw in the focuser collar.

Noticed some coma in this 30s of Archturus. What are your thoughts on it?

Disappointing. I shouldn't need to play around with spacing surely?

Single__2016-01-28_05-11-30_0003_ISO800_

The star issues seem to be across the entire frame, you need to check the following:

Collimation

CC Spacing

Whether the corrector and camera is seated in the drawtube correctly (no slop or tilt).

Also, was the shot taken with any guiding? Becuause trailing can occur easily in 30s if unguided - the smaller stars close to Arcturus give the game away (as theyre all eggy in the same direction).

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On 28/01/2016 at 17:51, Thalestris24 said:

Hi

T-ring could cause problems - make sure it's the recommended one!

Louise

Thanks Louise

Recommended one? Hope you aren't referring to the Baader one at £54 :eek:

Are there cheaper 'recommended' ones?

9 hours ago, Uranium235 said:

The star issues seem to be across the entire frame, you need to check the following:

Collimation

CC Spacing

Whether the corrector and camera is seated in the drawtube correctly (no slop or tilt).

Also, was the shot taken with any guiding? Becuause trailing can occur easily in 30s if unguided - the smaller stars close to Arcturus give the game away (as theyre all eggy in the same direction).

Thanks Rob

I agree there is trailing, can't remember whether it was guided or not now. I hope not! The coma to me seems uneven, most noticable top left corner and a bit bottom right may be. I have since added a third thumb screw to the draw tube so that may help. Something I did discover, keep the thread protector(ring with the writing printed on it) on as although it doesn't affect the spacing it does keep the thumscrews niclely in the undercut on the MPCC rather than half on the shoulder and it gives you a nice flush face to mate with the draw tube. I think overall it looks better in this image with the third thumbscrew fitted but still with possible spacing issues.

Stacked and processed in PI, still learning the ropes so ignore the hot pixels. Obviously guided but stars still don't look tight to me though.:sad2:

20 x 300s

M45.thumb.jpg.1dd8e19c173560d28e9ce232b8

The T-Ring I have has an inner threaded ring held in with grub screws, it is possible that this wasn't set correctly and or unevenly set. I've had a play with it and got the dimension from the mating face on the cammera side to the mating face on the CC side to 10.8 mm all round. This, with what I believe the sensor distance from the camera mating face to be 44.5mm, gives me a total of 55.3mm. This should be in the sweet spot as far as I know.

Pretty sure collimation was good but will confirm, still a bit of a dark art to me to be honest. Going to be stripping it down to flock it and fit a secondary heater while the weather is pants so when that's all done and the skies clear I'll give it another go.

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40 minutes ago, richyrich_one said:

Thanks Louise

Recommended one? Hope you aren't referring to the Baader one at £54 :eek:

Are there cheaper 'recommended' ones?

Thanks Rob

I agree there is trailing, can't remember whether it was guided or not now. I hope not! The coma to me seems uneven, most noticable top left corner and a bit bottom right may be. I have since added a third thumb screw to the draw tube so that may help. Something I did discover, keep the thread protector(ring with the writing printed on it) on as although it doesn't affect the spacing it does keep the thumscrews niclely in the undercut on the MPCC rather than half on the shoulder and it gives you a nice flush face to mate with the draw tube. I think overall it looks better in this image with the third thumbscrew fitted but still with possible spacing issues.

Stacked and processed in PI, still learning the ropes so ignore the hot pixels. Obviously guided but stars still don't look tight to me though.:sad2:

20 x 300s

M45.thumb.jpg.1dd8e19c173560d28e9ce232b8

The T-Ring I have has an inner threaded ring held in with grub screws, it is possible that this wasn't set correctly and or unevenly set. I've had a play with it and got the dimension from the mating face on the cammera side to the mating face on the CC side to 10.8 mm all round. This, with what I believe the sensor distance from the camera mating face to be 44.5mm, gives me a total of 55.3mm. This should be in the sweet spot as far as I know.

Pretty sure collimation was good but will confirm, still a bit of a dark art to me to be honest. Going to be stripping it down to flock it and fit a secondary heater while the weather is pants so when that's all done and the skies clear I'll give it another go.

The cc spec is 55mm +/- 1mm. I seem to recall that using a low profile t-ring can give the wrong spacing. Looking at your last image I don't think you have coma now but, yes, can see a lot of hot pixels! Yeah, sometimes t-rings seem to have a tendency to fall apart - very annoying!

Louise

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Just had a closer inspection of it, and the coma seems worse on the right hand side of the image. That would suggest some tilt in the imaging plane, as a short term solution you can focus your telescope with a star placed on that side of the frame (not centrally placed), that should help balance out the field a bit.

I noticed a fair smattering of hot pixels too, but oddly - they dont seem to be travelling in the same direction across the frame. Its almost as if they are subject to a rotational pattern... was your PA good enough? or did you rotate the camera at all during the shoot?

 

Edit: The presence of coma on the right side may suggest that the spacing or placement of the corrector (in the drawtube - ie: tilt) is too close. Fortunately, the Baader does have some tolerance, so you can increase the spacing in steps of 0.5mm if possible (mine turned out to be 57.5mm). You will know when you have gone too far becuase the coma distortion will become a radial distortion.

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Marginally off topic ...

Is there a great advantage (or any advantage at all for that matter) to getting a 150pds or orion optics VX6 over a 130 pds. My wife asked me if it would be worth getting something better when I talked about the 130pds. I notice the OTA weight for the VX6 is 4.5 Kg so it's barely more than the 130pds and with an option of 1/10 wave mirrors. The 1/10 wave might not be warranted under our skies but it suggests that the overall quality _might_ be better

 

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5 hours ago, DarkKnight said:

Some pretty impressive shots here.

Is the 130P-DS now discontinued, and if so, what is it's replacement?

Definitely not discontinued, possibly just not available in Australia. The smallest astrophotography reflector appears to be the 150P-DS http://www.skywatcheraustralia.com.au/product/bkp150-otaw-dual-speed-d-150mm-f-750mm/

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7 minutes ago, jnb said:

Marginally off topic ...

Is there a great advantage (or any advantage at all for that matter) to getting a 150pds or orion optics VX6 over a 130 pds. My wife asked me if it would be worth getting something better when I talked about the 130pds. I notice the OTA weight for the VX6 is 4.5 Kg so it's barely more than the 130pds and with an option of 1/10 wave mirrors. The 1/10 wave might not be warranted under our skies but it suggests that the overall quality _might_ be better

 

Hint:

Dont get a VX6, 1/10 wave optics make no difference when it comes to DSO imaging ;)

If you want a 6" get the 150pds - or if you want the wider field (for large nebs) get the 130pds. When it comes to small newts, Skywatcher have got it licked.

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15 minutes ago, Uranium235 said:

Just had a closer inspection of it, and the coma seems worse on the right hand side of the image. That would suggest some tilt in the imaging plane, as a short term solution you can focus your telescope with a star placed on that side of the frame (not centrally placed), that should help balance out the field a bit.

I noticed a fair smattering of hot pixels too, but oddly - they dont seem to be travelling in the same direction across the frame. Its almost as if they are subject to a rotational pattern... was your PA good enough? or did you rotate the camera at all during the shoot?

 

Edit: The presence of coma on the right side may suggest that the spacing or placement of the corrector (in the drawtube - ie: tilt) is too close. Fortunately, the Baader does have some tolerance, so you can increase the spacing in steps of 0.5mm if possible (mine turned out to be 57.5mm). You will know when you have gone too far becuase the coma distortion will become a radial distortion.

I didn't spot that with the hot pixel direction!

No camera rotation so likely the PA is not great. Need to check that again as well. PHD does seem to have to correct north/south as well as east/west. Not experienced enough to know what it should be doing if everything is setup well.

Since tweaking the T-Ring it's likely I've increased the spacing a little so just waiting on a clear sky.

I do appreciate your time and experience:)

Love to get this sorted and get some proper imaging done!

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15 hours ago, Cornelius Varley said:

Definitely not discontinued, possibly just not available in Australia. The smallest astrophotography reflector appears to be the 150P-DS http://www.skywatcheraustralia.com.au/product/bkp150-otaw-dual-speed-d-150mm-f-750mm/

Cheers Peter.

I came across this one locally ... Sky-Watcher BKP 130 OTAW Dual Speed, which looks identical to the 130P-DS  ....   http://www.sirius-optics.com.au/astrophotography/astrophotography-optical-tube-assemblies/skywatcher-130-650-photo-reflector.html

The specs read the same so it may be the 'down-under' version although it doesn't appear on the local SkyWatcher site.

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13 hours ago, DarkKnight said:

Cheers Peter.

I came across this one locally ... Sky-Watcher BKP 130 OTAW Dual Speed, which looks identical to the 130P-DS  ....   http://www.sirius-optics.com.au/astrophotography/astrophotography-optical-tube-assemblies/skywatcher-130-650-photo-reflector.html

The specs read the same so it may be the 'down-under' version although it doesn't appear on the local SkyWatcher site.

The specs are the same.

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Can anyone share the picture taken with that scope but without coma corrector? I will be probably getting 130pds today but not enough money for the CC at the moment so jus by curiosity wnat to see if lack of CC will cause drama on the picture and how much of FOV will be not affected. Not much more money there is a 150pds which is not my target due to relative big focal lenght but on the other hand i believe it will give more of FOV not affected without the CC ?

Edited by Kirien
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12 hours ago, Kirien said:

Can anyone share the picture taken with that scope but without coma corrector? I will be probably getting 130pds today but not enough money for the CC at the moment so jus by curiosity wnat to see if lack of CC will cause drama on the picture and how much of FOV will be not affected. Not much more money there is a 150pds which is not my target due to relative big focal lenght but on the other hand i believe it will give more of FOV not affected without the CC ?

Depending on what camera you are using (chip size), you will have about a 50% useable field - maybe a bit less (ie: you will end up cropping half of it out) without a coma corrector. It will get real ugly towards the corners.

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