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Old 05-09-2020, 02:10 PM
Dennis
Dazzled by the Cosmos.

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UKS1 (UK Schmidt 1)

I recently replaced my JMI Motorised Focuser with the Primalucelab ESATTO 2” Focuser as I discovered that my focus was shifting over a period of 1 hour or so of imaging. The JMI focuser was loaded with the weight of a Tak x0.8 Reducer, USB Colour Filter Wheel and ASI1600 Camera. I initially thought it may be temperature related, but in the end concluded it was more likely a mechanical issue, I was simply asking too much of the JMI.

Whatever it was, it has now been fixed so as a test target, I selected one of the brighter Milky Way Globular Clusters, UKS 1 (magnitude 17.29) to compare to a previous effort, which saw me rejecting a lot of out of focus frames due to the gradual focus drift as the scope tracked the objects higher towards the zenith.

Over a couple of nights under Bortle 6 skies in Brisbane, I took the following:

LUM: 30 secs x 120 (60 Mins)
RED: 30 secs x 40 (20 Mins)
GREEN: 30 secs x 40 (20 Mins)
BLUE: 30 secs x 40 (20 Mins)
IR807: 60 secs x 30 (30 Mins)

The ‘scope is a Tak Mewlon 210 F11.5 DK with Tak Reducer/Flattener x0.8. A plate solve gave me a measured focal length of 2080mm at F9.9.

I threw all the frames into the Batch Processing Script of PixInsight, adding Bias, Darks and Flats and PI took care of the change in camera orientation and framing over the 2 nights, as I have to set up and tear down each night.

I added the IR807 as a Luminance Frame in PS CC, which brought out the faint UKS-1 and the even smaller and fainter Crouch-1 (VVV GL001), which I believe was discovered independently by Steve Crouch and professional astronomers.

Steve Crouch’s independent discovery images can be found here:
http://members.pcug.org.au/~stevec/u..._STL11K_RC.htm
http://members.pcug.org.au/~stevec/u...sta_GCL001.jpg
http://www.iceinspace.com.au/forum/s...ad.php?t=82032

The last 2 images (annotated) have been rotated 90 degrees CCW to better show the 2 faint Globs.

I wasn’t game enough to explore the depths of PI to figure out where the blue star halos were coming from in my images.

Cheers

Dennis
Attached Thumbnails
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Click for full-size image (LRGB_DBE_ABE_ABE-ATWT-Crop-1280-C.jpg)
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Click for full-size image (LRGB_DBE_ABE_ABE-ATWT-Crop-1280-D.jpg)
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Click for full-size image (LRGB_DBE_ABE_ABE-ATWT-Crop-1280-B-FR.jpg)
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Click for full-size image (LRGB_DBE_ABE_ABE-ATWT-Crouch-1.jpg)
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  #2  
Old 08-09-2020, 05:29 PM
Placidus (Mike and Trish)
Narrowing the band

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Hi!

Could you explain what the different thumbnails are? Are they "before and after fixing the focusing issue", or are they "early, middle, and late night" to show there's no shift, or are they different processing, or as Ellery Queen said, "someone else entirely"?

Perhaps you could give the different thumbs explanatory names, or perhaps you could put captions on them.

I'm assuming that the idea of the near-infrared filtered image for luminance is to take advantage of improved seeing in the near infrared. If so, perhaps you could edit your post accordingly.

Regardless, any single one of them looks magnificent. Well done!

We have a 20 inch PlaneWave, with their three inch throat focuser, carrying about 20 kgs of FLI PL16803 camera, 8 position 50 mm square filter wheel, off axis guider, guide camera, and lots of power and data cables. As supplied, that flops about all over the place, with gross camera tilt as the scope tracks in RA, and resultant marked change in focus. We added a radially placed spring-loaded strut (think of a car's front suspension) so that the focuser can still move in and out +/- a couple millimeters, but is constrained in the RA direction to stay exactly on-axis. That was chalk and cheese. The key point is that the focuser wasn't moving in and out, it was flopping sideways. (The attached photo shows an earlier version with an Aspen camera. The new camera is heavier and the strut system much stronger again).
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Last edited by Placidus; 08-09-2020 at 05:52 PM.
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  #3  
Old 08-09-2020, 05:38 PM
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h0ughy (David)
DOGHOUSE REBORN

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Feint obscure and another trophy captured
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Old 08-09-2020, 08:33 PM
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Zubenel (Wes)
Awe and Wonder

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Faint , Obscure and if I'd known I could have eyeballed it for you Dennis Well maybe
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Old 09-09-2020, 08:01 AM
Dennis
Dazzled by the Cosmos.

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Quote:
Originally Posted by Placidus View Post
Hi!

Could you explain what the different thumbnails are? Are they "before and after fixing the focusing issue", or are they "early, middle, and late night" to show there's no shift, or are they different processing, or as Ellery Queen said, "someone else entirely"?

Perhaps you could give the different thumbs explanatory names, or perhaps you could put captions on them.

I'm assuming that the idea of the near-infrared filtered image for luminance is to take advantage of improved seeing in the near infrared. If so, perhaps you could edit your post accordingly.

Regardless, any single one of them looks magnificent. Well done!

We have a 20 inch PlaneWave, with their three inch throat focuser, carrying about 20 kgs of FLI PL16803 camera, 8 position 50 mm square filter wheel, off axis guider, guide camera, and lots of power and data cables. As supplied, that flops about all over the place, with gross camera tilt as the scope tracks in RA, and resultant marked change in focus. We added a radially placed spring-loaded strut (think of a car's front suspension) so that the focuser can still move in and out +/- a couple millimeters, but is constrained in the RA direction to stay exactly on-axis. That was chalk and cheese. The key point is that the focuser wasn't moving in and out, it was flopping sideways. (The attached photo shows an earlier version with an Aspen camera. The new camera is heavier and the strut system much stronger again).
Hi Mike & Trish

Thanks for looking and commenting, I appreciate it.

I guess I got too excited with fixing my focus drift problem and newly acquired PixInsight skills that I assumed everyone on IIS would know about Steve Crouch's co-discovery of a faint GC.

Here is an inventory of the frames:
  • #1 is a slight crop of the FOV with the ragged stacking edges cropped.
  • #2 through #4 are just tighter crops of UKS-1 showing how small and faint this sucker is.
  • #5 and #6 are full res crops of the region around UKS-1 and Steve's VVV GL001, rotated 90 deg CCW to frame them better.

The IR807 Filter data revealed the GC's - nothing shows up on the LRGB frames so these GCs only reveal their presence in the IR region.

I did try IR642 and not much showed up, but IR742 did begin to reveal some fuzzy data on UKS-1, with the strongest signal in IR807.

It was so satisfying to have finally solved my focus drift problems and to take a deeper dive into PI - it is such a breathtakingly adept image processing tool, or set of tools.

Cheers

Dennis
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  #6  
Old 09-09-2020, 08:03 AM
Dennis
Dazzled by the Cosmos.

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Quote:
Originally Posted by h0ughy View Post
Feint obscure and another trophy captured
Thanks David, I was such a happy chappie having solved my focus drift problem which had really prevented me from doing much DSO work, and aligned with my new found knowledge of PI, I am an astronomer reborn.

Cheers

Dennis
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Old 09-09-2020, 08:05 AM
Dennis
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Originally Posted by Zubenel View Post
Faint , Obscure and if I'd known I could have eyeballed it for you Dennis Well maybe
Thanks Wes, let me know how the operation goes in fitting IR807 filters to your eyeballs.

Cheers

Dennis
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Old 09-09-2020, 08:07 AM
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multiweb (Marc)
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Some pretty deep imaging there Dennis. Pushing the envelope.
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Old 09-09-2020, 10:22 AM
Dennis
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Originally Posted by multiweb View Post
Some pretty deep imaging there Dennis. Pushing the envelope.
Thanks Marc, the ESATTO Motorised Focuser, @Focus3 in The Sky X Pro and PixInsight have awakened me from a deep DSO slumber.

I had become a bit disillusioned with focus drift problems and marching noise across my frames (I never dithered), but now I have discovered the delights of injecting an @Focus3 run into my series, dithering between frames and processing in PI, my enthusiasm is renewed.

Cheers

Dennis
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Old 10-09-2020, 08:51 AM
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multiweb (Marc)
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I had a look at the product video at primaluce. That guy cracks me up every time he says focuser. He should be R-rated.

It's a reallly nice bit of kit and low profile too. Little out of my price range but I'm still looking at it. What are you doing to me Dennis!

No sag or flexure at all?
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Old 10-09-2020, 08:59 AM
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Derek Klepp
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Great results Dennis.Its good you solved the problem.
Derek
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  #12  
Old 10-09-2020, 10:25 AM
Dennis
Dazzled by the Cosmos.

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Quote:
Originally Posted by multiweb View Post
I had a look at the product video at primaluce. That guy cracks me up every time he says focuser. He should be R-rated.

It's a reallly nice bit of kit and low profile too. Little out of my price range but I'm still looking at it. What are you doing to me Dennis!

No sag or flexure at all?
Hi Marc

When I did my investigation is offered the least back-focus distance in the range I thought were suited to my needs. Paul at Sidereal Trading was very helpful and provided excellent service.

Like you, I love the over the top Hollywood performance of Filippo, but it was the Ferrari-red colour that finally sold me.

The Mewlon, even with the Tak Reducer/Flattener still produces distorted stars towards the edge of the filed but they look to be even across the extremes of the frame so no evidence of sagging with the Tak x0.8 RF, SX USB 7 slot FW and ASI1600mm Pro.

Cheers

Dennis

EDIT: I also liked the Primaluce Labs systems approach, with the many adapters and accessories available, plus an upgrade path as new components (e.g. Rotator) become available.

Last edited by Dennis; 10-09-2020 at 10:39 AM.
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  #13  
Old 10-09-2020, 10:26 AM
Dennis
Dazzled by the Cosmos.

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Originally Posted by Derek Klepp View Post
Great results Dennis.Its good you solved the problem.
Derek
Thanks Derek, it is satisfying when you can fix something like this as often, there are so many components, that it can be challenging to chase down the offending part(s).

Cheers

Dennis
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