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Russe

Imaging with the 130pds

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Hi,

That's looking really good. ?

Secondary collimation is a pain with the PDS, I used flats to get the rotation right in the end, and it worked quite well.

John

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2 hours ago, JohnSadlerAstro said:

Secondary collimation is a pain with the PDS

+1. To make it less so, be sure to obviate the need for allen keys -tilt- and place a teflon plastic milk carton washer -rotation- between the secondary stalk and the three adjusters. HTH.

IMG_20181228_124723.thumb.jpg.5cd68548a7acb83b4b3126ef3095657e.jpg

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3 hours ago, JohnSadlerAstro said:

Hi,

That's looking really good. ?

Secondary collimation is a pain with the PDS, I used flats to get the rotation right in the end, and it worked quite well.

John

Hmm, can you please explain this part in detail? As I spent lots of time placing the secondary using Chesire and col.cap and I dont think I managed to place it perfectly :)

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8 hours ago, JohnSadlerAstro said:

Hi,

That's looking really good. ?

Secondary collimation is a pain with the PDS, I used flats to get the rotation right in the end, and it worked quite well.

John

Thanks!

Flats with ccdware ccdinspector?

Edited by jjosefsen

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47 minutes ago, Susaron said:

What's the reason of the rca female plug into the tube? I missed something.

Possible future diy secondary heater if the dew shield doesn't cut it.. can do really thin wires out to the plug, and then attach it to my dew controller with that plug.

It's inline with the spidervane, so shouldn't produce any additional diffraction.

Edited by jjosefsen

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1 hour ago, Susaron said:

What's the reason of the rca female plug into the tube? I missed something.

 

21 minutes ago, jjosefsen said:

Possible future diy secondary heater if the dew shield doesn't cut it.. can do really thin wires out to the plug, and then attach it to my dew controller with that plug.

It's inline with the spidervane, so shouldn't produce any additional diffraction.

As in here:

FN2008c-2.jpg

Close up of a lacerta newton reflector. Very clever design, as it minimizes diffraction.

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7 hours ago, wimvb said:

 

As in here:

FN2008c-2.jpg

Close up of a lacerta newton reflector. Very clever design, as it minimizes diffraction.

Exactly!

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Understood.

Well this evening I am going to suffer 1 degree and 75% humidity, I will make some pictures.

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45 minutes ago, Susaron said:

Understood.

Well this evening I am going to suffer 1 degree and 75% humidity, I will make some pictures.

:grin: yesterday I suffered -5 degrees and a frost covered setup. But that was with a 150PDS, so not for this thread. ?

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On ‎28‎/‎12‎/‎2018 at 13:31, RolandKol said:

Hmm, can you please explain this part in detail? As I spent lots of time placing the secondary using Chesire and col.cap and I dont think I managed to place it perfectly :)

19 hours ago, jjosefsen said:

Thanks!

Flats with ccdware ccdinspector?

Hi,

As far as I know it isn't a standard method of collimation, I had to develop it after my Cheshire showed the scope as collimated but my subs showed severe coma and distortion across the upper right hand third of the fov.

This drawing sort of explains the idea, sorry about the quality! :D 

IMG_20181229_121821.thumb.jpg.3b605c74bb7bab0d5c7559abe1a1b938.jpg

The main concept is that coma and *secondary* light-cone misalignment are related when primary misalignment is removed. Image coma and vignette are in the same places as each other, when the primary is collimated relative to the secondary. In other words, the method can only adjust the secondary and therefore requires use of a Cheshire to keep the primary constantly aligned with the secondary throughout the process.

To get a flat, I simply take a quick shot through the scope with my laptop screen open in Notepad, and then take the result into GIMP or StarTools to do a full desaturation and a savage clip/stretch. This was the result from the scope before any secondary adjustments, bear in mind that at this point it was "perfectly" collimated according to the Cheshire *and was rotated/centred almost perfectly, too*.

The dark gradients were indeed in the same place as the bad coma, and they fell in the position I had predicted.

before.thumb.jpg.4e2b3421daff79ea97bfc19ce020ea19.jpg

As shown on the diagram, I then worked out which direction on the photo was which direction for the secondary, then started to adjust. Throughout the process the corrections were perfectly logical and followed my 'hypothesis'. ;) Note that the same stretch has not been applied to each flat, I altered the black point etc to optimise each one for the section I was trying to clean up. Shots 1-3 below show me getting the vertical (horizontal for the secondary) axis correct, then numbers 4-5 show me rotating the secondary into place.

1801030668_BothCorreccted1.thumb.jpg.22138a36b7d54dd3a36a0b530a0c57a4.jpg348033137_BothCorreccted2.thumb.jpg.8d6245d2f76f332034446c20e7099555.jpg1157278778_BothCorreccted3.thumb.jpg.db4f21135740584dc12645a02dbdeb5b.jpg1932484833_BothCorreccted4.thumb.jpg.fd1748673613866c3ccbdaf001923775.jpg210274668_BothCorrected5.thumb.jpg.c6862c12310b11ce551788e9d9d9d0ff.jpg

After a bit of work I got this ^.

Most of the adjustment I had to make was rotation on the secondary, (up is to the right on the photos, so it was drooping a bit) and a little bit of centring with the vanes; I made sure that the primary was correctly adjusted after each movement of the secondary before I took the flat to estimate mis-collimation. I was then able to get almost entirely coma-free images. 

Hope this helps :) 

John

 

Edited by JohnSadlerAstro
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That's a new approach to collimation. Just 2 questions:

1. How is your collimation now according to the Cheshire?

2. Can you post a pic taken down the drawtube, showing how the secondary is aligned to the focuser?

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1 hour ago, wimvb said:

That's a new approach to collimation. Just 2 questions:

1. How is your collimation now according to the Cheshire?

2. Can you post a pic taken down the drawtube, showing how the secondary is aligned to the focuser?

Hi,

1. The collimation was "correct" according to the Cheshire on all of the images, with the secondary centred and the primary dot lined up etc. However, it has been around 8 months since I collimated last, and I think things have drifted a little, theres a tad more coma than usual in some parts of my latest subs.

2. I'm planning to re-collimate next week in time for the new moon using this method so I will post up some shots once its properly done, but here's what it looks like atm. :)

 00001IMG_00001_BURST20181229160555.thumb.jpg.f1ea1ff9a20736a1137c7d859b0a680b.jpg

John

Edited by JohnSadlerAstro
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2 hours ago, JohnSadlerAstro said:

Hi,

As far as I know it isn't a standard method of collimation, I had to develop it after my Cheshire showed the scope as collimated but my subs showed severe coma and distortion across the upper right hand third of the fov.

This drawing sort of explains the idea, sorry about the quality! :D 

IMG_20181229_121821.thumb.jpg.3b605c74bb7bab0d5c7559abe1a1b938.jpg

The main concept is that coma and *secondary* light-cone misalignment are related when primary misalignment is removed. Image coma and vignette are in the same places as each other, when the primary is collimated relative to the secondary. In other words, the method can only adjust the secondary and therefore requires use of a Cheshire to keep the primary constantly aligned with the secondary throughout the process.

To get a flat, I simply take a quick shot through the scope with my laptop screen open in Notepad, and then take the result into GIMP or StarTools to do a full desaturation and a savage clip/stretch. This was the result from the scope before any secondary adjustments, bear in mind that at this point it was "perfectly" collimated according to the Cheshire *and was rotated/centred almost perfectly, too*.

The dark gradients were indeed in the same place as the bad coma, and they fell in the position I had predicted.

before.thumb.jpg.4e2b3421daff79ea97bfc19ce020ea19.jpg

As shown on the diagram, I then worked out which direction on the photo was which direction for the secondary, then started to adjust. Throughout the process the corrections were perfectly logical and followed my 'hypothesis'. ;) Note that the same stretch has not been applied to each flat, I altered the black point etc to optimise each one for the section I was trying to clean up. Shots 1-3 below show me getting the vertical (horizontal for the secondary) axis correct, then numbers 4-5 show me rotating the secondary into place.

1801030668_BothCorreccted1.thumb.jpg.22138a36b7d54dd3a36a0b530a0c57a4.jpg348033137_BothCorreccted2.thumb.jpg.8d6245d2f76f332034446c20e7099555.jpg1157278778_BothCorreccted3.thumb.jpg.db4f21135740584dc12645a02dbdeb5b.jpg1932484833_BothCorreccted4.thumb.jpg.fd1748673613866c3ccbdaf001923775.jpg210274668_BothCorrected5.thumb.jpg.c6862c12310b11ce551788e9d9d9d0ff.jpg

After a bit of work I got this ^.

Most of the adjustment I had to make was rotation on the secondary, (up is to the right on the photos, so it was drooping a bit) and a little bit of centring with the vanes; I made sure that the primary was correctly adjusted after each movement of the secondary before I took the flat to estimate mis-collimation. I was then able to get almost entirely coma-free images. 

Hope this helps :) 

John

 

Thank you John, very interrestign approach!

I plan on giving collimation a whirl tonight, will be interresting to see how it all goes.

I've been reading various sources of information, and Astro Baby's seem to be pretty well thought out so going by that tonight. :)

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2 minutes ago, jjosefsen said:

Thank you John, very interrestign approach! 

I plan on giving collimation a whirl tonight, will be interresting to see how it all goes.

I've been reading various sources of information, and Astro Baby's seem to be pretty well thought out so going by that tonight. :)

Thanks!

Yeah, those are well written and explained.

I wouldn't recommend trying my method for now, it needs some more work to 100% prove that it works and to sort out some miscalculations etc which cropped up! ;) :D 

John

Edited by JohnSadlerAstro

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IMG_20181229_214207.thumb.jpg.7fe26412c88c4b5dff68df36840d82f3.jpg

This is taken through the 2" concenter eyepiece, looks pretty good I think. If I understand it is normal for the "shadow" to be slightly elongated on a f5 scope..?

I don't know how you guys take such good pictures through those collimation tools.. but naked eye, all three mirror clips are about equally visible as well.

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1 hour ago, jjosefsen said:

This is taken through the 2" concenter eyepiece, looks pretty good I think. If I understand it is normal for the "shadow" to be slightly elongated on a f5 scope..?

I don't know how you guys take such good pictures through those collimation tools.. but naked eye, all three mirror clips are about equally visible as well.

1

Simply, try using a smartphone! just like you did with concenter :)

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18 hours ago, JohnSadlerAstro said:

Hi,

As far as I know it isn't a standard method of collimation, I had to develop it after my Cheshire showed the scope as collimated but my subs showed severe coma and distortion across the upper right hand third of the fov.

This drawing sort of explains the idea, sorry about the quality! :D 

IMG_20181229_121821.thumb.jpg.3b605c74bb7bab0d5c7559abe1a1b938.jpg

The main concept is that coma and *secondary* light-cone misalignment are related when primary misalignment is removed. Image coma and vignette are in the same places as each other, when the primary is collimated relative to the secondary. In other words, the method can only adjust the secondary and therefore requires use of a Cheshire to keep the primary constantly aligned with the secondary throughout the process.

To get a flat, I simply take a quick shot through the scope with my laptop screen open in Notepad, and then take the result into GIMP or StarTools to do a full desaturation and a savage clip/stretch. This was the result from the scope before any secondary adjustments, bear in mind that at this point it was "perfectly" collimated according to the Cheshire *and was rotated/centred almost perfectly, too*.

The dark gradients were indeed in the same place as the bad coma, and they fell in the position I had predicted.

before.thumb.jpg.4e2b3421daff79ea97bfc19ce020ea19.jpg

As shown on the diagram, I then worked out which direction on the photo was which direction for the secondary, then started to adjust. Throughout the process the corrections were perfectly logical and followed my 'hypothesis'. ;) Note that the same stretch has not been applied to each flat, I altered the black point etc to optimise each one for the section I was trying to clean up. Shots 1-3 below show me getting the vertical (horizontal for the secondary) axis correct, then numbers 4-5 show me rotating the secondary into place.

1801030668_BothCorreccted1.thumb.jpg.22138a36b7d54dd3a36a0b530a0c57a4.jpg348033137_BothCorreccted2.thumb.jpg.8d6245d2f76f332034446c20e7099555.jpg1157278778_BothCorreccted3.thumb.jpg.db4f21135740584dc12645a02dbdeb5b.jpg1932484833_BothCorreccted4.thumb.jpg.fd1748673613866c3ccbdaf001923775.jpg210274668_BothCorrected5.thumb.jpg.c6862c12310b11ce551788e9d9d9d0ff.jpg

After a bit of work I got this ^.

Most of the adjustment I had to make was rotation on the secondary, (up is to the right on the photos, so it was drooping a bit) and a little bit of centring with the vanes; I made sure that the primary was correctly adjusted after each movement of the secondary before I took the flat to estimate mis-collimation. I was then able to get almost entirely coma-free images. 

Hope this helps :) 

John

 

Hi John, Great explanation there. You mentioned the "elongated stars on upper right". Now that's a problem I've been facing with my astrograph. I've tried using the Gary Seronik method that you've described though a modernised manner. I still need to check mine on real stars though.

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Last picture of the year, I still can not find the reason for the astigmatism of the main mirror, and some coma I have, though the spacing is correct.

IC405 Flamming Star Nebula, 37x5min subs with the QHY168C+IDAS LPS+SW130PDS+Baader MPCC+AZEQ5+ZWO 30mm guide tube + ASI385MC. Captured with APT and processed with Pix. From my point of view it still needs 2 more hours to be perfect.

Cheers.

 

 

IC405_wtmrk.jpg

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Does anyone know of a design for a 3d printed bahtinov mask for the 130pds? Google and thingiverse yielded nothing..

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Last Saturday the temperature stood all the session between -2º and 1º Celsius, as I was point to Auriga close to the zenith, frost started to appear over my main mirror.

I have designed a support to hold a small 12V fan on the rear, fitted through the mirror cell fixed screws. I attach the .stl from Catia. I still need to send it to the 3D printer, so no final check is done.

 

SoporteVentilador.stl

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So this is the scope roughly focused on stars (just managed before clouds). Do I need to chop it all off, roughly 15mm or do I leave some to protrude into the tube?

IMG_20190103_201606.jpg

Edited by jjosefsen

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This is mine before:

RTteRTZ0_d3x_1824x0_wmhqkGbg.jpg

This is afterwards with a bit of black over the raw metal cut bits to prevent reflections - circumcision courtesy of RolandKol:

zffZi7l07Lfu_1824x0_wmhqkGbg.jpg

HTH

Carole 

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