Imaging with the 130pds

[matt_baker]

On 17/01/2019 at 20:06, Whistlin Bob said:

Always a bit tricky imaging under a bright moon, but even more so when you’re in clumsy mode. Last night I managed to disconnect the power from my mount whilst aligning. Twice! Then I dropped an eyepiece by slewing the scope without having it fixed properly (fortunately it landed on the rubber eye cup). Finally I spent ages trying to work out why I couldn’t focus my guide-scope until the penny finally dropped that I was twiddling with the locking ring and not the focuser. So I’m taking this picture as a victory of the scope over its owner!

15x 10 min subs – Canon 600d – 130 pd-s- 7nm Ha filter.

 

If I'm honest, I think that taking 10 minute subs with a non-cooled camera is a bit overkill and will bring in a lot of thermal noise, due to the sensor increasing temperature over time.

I reckon more 5 minute subs will do better but that's just my opinion

If the camera was cooled, then yes of course take long exposures.

[Stub Mandrel]

On 17/01/2019 at 20:06, Whistlin Bob said:

Always a bit tricky imaging under a bright moon, but even more so when you’re in clumsy mode. Last night I managed to disconnect the power from my mount whilst aligning. Twice! Then I dropped an eyepiece by slewing the scope without having it fixed properly (fortunately it landed on the rubber eye cup). Finally I spent ages trying to work out why I couldn’t focus my guide-scope until the penny finally dropped that I was twiddling with the locking ring and not the focuser. So I’m taking this picture as a victory of the scope over its owner!

15x 10 min subs – Canon 600d – 130 pd-s- 7nm Ha filter.

 

Nice one Rob. I'm suffering major guilt for only getting one 5-minute sub(!) over the last two weeks ?

[Whistlin Bob]

17 hours ago, matt_baker said:

If I'm honest, I think that taking 10 minute subs with a non-cooled camera is a bit overkill and will bring in a lot of thermal noise, due to the sensor increasing temperature over time.

I reckon more 5 minute subs will do better but that's just my opinion

If the camera was cooled, then yes of course take long exposures.

Hi Matt- yes the theory would suggest that, but I've tried this in practice and the longer exposures are giving me better results. I initially tried 5 minute exposures when I got the Ha filter and have gradually built up to ten and the results are definitely better. I think the cold weather helps!

[Whistlin Bob]

5 hours ago, Stub Mandrel said:

Nice one Rob. I'm suffering major guilt for only getting one 5-minute sub(!) over the last two weeks ?

It's hard going out in the cold sometimes- especially if the weather is uncertain. 

[jjosefsen]

Hi,

I could use a bit of an opinion on this, I can't decide if this is tilt or spacing.. I don't think it is collimation, because that looks pretty much bang on as far as I can tell at least.

CCD Inspector did say there was a little tilt, but with my limited knowledge I am not sure if it is enough to give these effects.

To me it looks like something is affecting the right side of the image, and a little top left too.

Any ideas?

 

[Adam J]

2 hours ago, jjosefsen said:

Hi,

I could use a bit of an opinion on this, I can't decide if this is tilt or spacing.. I don't think it is collimation, because that looks pretty much bang on as far as I can tell at least.

CCD Inspector did say there was a little tilt, but with my limited knowledge I am not sure if it is enough to give these effects.

To me it looks like something is affecting the right side of the image, and a little top left too.

Any ideas?

which way is gravity pointing in respect to the image taking camera orientation into account?

How are you attaching the camera? Just the original two thumb screws?

Have you checked the tension / preloading on the draw tube?

I would say this is tilt but need to know the above to be sure. It would have to be quite bad to cause issues like these on such a small sensor.

It cant be spacing alone or you would have the same problem in all three corners.

Adam

 

Edited January 19, 2019 by Adam J

[Susaron]

That x shape stars is astigmatism. The same thing I suffered. Check the distance to the coma corrector and also relief a little bit the clips on the main mirror cell as they are hardly tighten and can create stress on the mirror.

[Adam J]

A couple of my recent efforts with the 130PDS the top one is a Bi color of the heart consisting of 70x240s Ha and 70 x 240s OIII using my ASI1600MM Pro and 5nm Astrodon Filters.

The Second image is 100 x 30s Lum and 40x 30s RGB per channel on M42.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thanks for looking,

Adam

Edited January 19, 2019 by Adam J

[Adam J]

22 minutes ago, Susaron said:

That x shape stars is astigmatism. The same thing I suffered. Check the distance to the coma corrector and also relief a little bit the clips on the main mirror cell as they are hardly tighten and can create stress on the mirror.

Yes. I have also seen an over compressed coma corrector cause this.

Adam

[jjosefsen]

23 minutes ago, Adam J said:

Yes. I have also seen an over compressed coma corrector cause this.

Adam

First of all, great shots Adam! I particularly like the Heart / Fish head.. Have you considered shooting a little RGB to replace the stars?

How exactly does one over compress a coma corrector? Screw it in too tight?

[jjosefsen]

49 minutes ago, Susaron said:

That x shape stars is astigmatism. The same thing I suffered. Check the distance to the coma corrector and also relief a little bit the clips on the main mirror cell as they are hardly tighten and can create stress on the mirror.

Whoops! I did tighten it all up quite firm that night, will go loosen it now.

[Adam J]

Just now, jjosefsen said:

First of all, great shots Adam! I particularly like the Heart / Fish head.. Have you considered shooting a little RGB to replace the stars?

How exactly does one over compress a coma corrector? Screw it in too tight?

Exactly. Screwing it too tight, although I have only seen an example that was with a baader click lock. The optics are very snug to the metal barrel.

Adam

[Adam J]

4 minutes ago, jjosefsen said:

Whoops! I did tighten it all up quite firm that night, will go loosen it now.

Problem is that with only two screws you will get tilt also as you tighten up the corrector. I added a third screw to get even pressure around the barrel and stop it from tilting. You also have to tighten them evenly in small amounts like with the head gasket on a car . Same procedure with the colimation tool or you will tilt that.  If none of that then as above check the primary mirror clips.

Edited January 19, 2019 by Adam J

[jjosefsen]

Then it might be because I over tightened the screws when putting the cc.. I'm scared of the camera falling out. Will check next time.

I do plan to add a third screw, just need to buy the tools and screw.

Thanks for the input! ?

Edited January 19, 2019 by jjosefsen

[lnlarxg]

130pds on planetary. I love this scope (sometime I do hug and kiss it), proper solid partner earlier for the total lunar eclipse. 

10s shot at iso340 from canon 6d

 

 

Edited January 25, 2019 by lnlarxg

[carastro]

Great Lunar eclipse image. 

Carole 

[happy-kat]

Love the lone star bottom left.

[jjosefsen]

Outstanding blood moon!

[jjosefsen]

Pheeew so I had the 130p-ds out last night again.. So far this little project is proving extremely frustrating!

 

The other day I spent all night redoing collimation as I still didn't have great stars, and suspected tilt.

I recentered secondary, adjusted tilt in focuser, and got what I believed was a good result when looking down my concenter eye piece.

Flats were also looking much better and evenly illuminated, so I figured I was good to go.

 

Last night I set up, and immediately I had what looked like wrong spacing in my CC, didn't have this issue before! Took camera, fw, and CC back ind, took it apart, meassured it and it was correct - 55.5mm..

Back outside camera in and now it looked ok again, but stars in the corners had strange artifacts. I spent an hour checking collimation again with eyepiece and defocused stars and it looked fine in the center of the image..

Finally I chucked the laser collimater in, and it was off - I adjusted it with the laser and took anokther shot - suddenly the stars were pretty good all around!! ?

 

Attached is the unedited RGB master of M37, only 30m of each channel..

Stars look a bit funky towards the bottom right still.

 

The thing is when I check collimation through my concenter just now, it looks completely bonkers and nothing like I would expect!!

This thing is driving me mad, and I am just about ready to chuck it in a box and dig out the good old ED80...

[RolandKol]

30 minutes ago, jjosefsen said:

Pheeew so I had the 130p-ds out last night again.. So far this little project is proving extremely frustrating!

 

The other day I spent all night redoing collimation as I still didn't have great stars, and suspected tilt.

I recentered secondary, adjusted tilt in focuser, and got what I believed was a good result when looking down my concenter eye piece.

Flats were also looking much better and evenly illuminated, so I figured I was good to go.

 

Last night I set up, and immediately I had what looked like wrong spacing in my CC, didn't have this issue before! Took camera, fw, and CC back ind, took it apart, meassured it and it was correct - 55.5mm..

Back outside camera in and now it looked ok again, but stars in the corners had strange artifacts. I spent an hour checking collimation again with eyepiece and defocused stars and it looked fine in the center of the image..

Finally I chucked the laser collimater in, and it was off - I adjusted it with the laser and took anokther shot - suddenly the stars were pretty good all around!! ?

Attached is the unedited RGB master of M37, only 30m of each channel..

Stars look a bit funky towards the bottom right still.

The thing is when I check collimation through my concenter just now, it looks completely bonkers and nothing like I would expect!!

This thing is driving me mad, and I am just about ready to chuck it in a box and dig out the good old ED80...

not sure about concenter, 

but  secondary mirror is a real battle... especially without experience... but once done, - do not touch it anymore!
I was not able to place back my secondary for awhile.... I even though I bough a spoiled Cheshire  or my focuser is way off... but it looks like my battle is won
btw, your 7 sisters looked very nicely, not sure why you were not happy with collimation at that time?....

[Adam J]

4 hours ago, jjosefsen said:

Pheeew so I had the 130p-ds out last night again.. So far this little project is proving extremely frustrating!

 

The other day I spent all night redoing collimation as I still didn't have great stars, and suspected tilt.

I recentered secondary, adjusted tilt in focuser, and got what I believed was a good result when looking down my concenter eye piece.

Flats were also looking much better and evenly illuminated, so I figured I was good to go.

 

Last night I set up, and immediately I had what looked like wrong spacing in my CC, didn't have this issue before! Took camera, fw, and CC back ind, took it apart, meassured it and it was correct - 55.5mm..

Back outside camera in and now it looked ok again, but stars in the corners had strange artifacts. I spent an hour checking collimation again with eyepiece and defocused stars and it looked fine in the center of the image..

Finally I chucked the laser collimater in, and it was off - I adjusted it with the laser and took anokther shot - suddenly the stars were pretty good all around!! ?

 

Attached is the unedited RGB master of M37, only 30m of each channel..

Stars look a bit funky towards the bottom right still.

 

The thing is when I check collimation through my concenter just now, it looks completely bonkers and nothing like I would expect!!

This thing is driving me mad, and I am just about ready to chuck it in a box and dig out the good old ED80...

Welcome to imaging with a Newtonian, did you really think that it was going to be as easy as a ED80?

Now imagine doing the same thing but needing to be more accurate in colimation due to using a much larger sensor.

I think that if you are mostly after perfect stars then you are better off with the ED80, but its a slower scope so you wont get the faint stuff in the same detail or as fast as you do with the 130PDS without longer integration.

I would be happy with what you have here.  How was your tracking it looks like you might have had some drift across the image as a whole?

The only other thing I would note is that the most likely reason that you are getting different results between the two colimation devices is that they are being held differently by the stock 2inch clamp as discussed before.

Adam

 

 

[jjosefsen]

4 minutes ago, Adam J said:

Welcome to imaging with a Newtonian, did you really think that it was going to be as easy as a ED80?

Now imagine doing the same thing but needing to be more accurate in colimation due to using a much larger sensor.

I think that if you are mostly after perfect stars then you are better off with the ED80, but its a slower scope so you wont get the faint stuff in the same detail or as fast as you do with the 130PDS without longer integration.

I would be happy with what you have here.  How was your tracking it looks like you might have had some drift across the image as a whole?

The only other thing I would note is that the most likely reason that you are getting different results between the two colimation devices is that they are being held differently by the stock 2inch clamp as discussed before.

Adam

 

 

Well no I didn't expect it to be as plug and play as a frac, or everyone would use one. Part of the reason I got this one, but went for a higher end CC was that I wanted to see how I got on with a reflector, expecting to do ok, and then to go for something like an 8" F3.9 if it worked out.

That plan is on hold for now ?

I think my problem is with the secondary still..

The extra speed of this scope is very nice to be honest, and nice to work with.

[wimvb]

7 hours ago, jjosefsen said:

I wanted to see how I got on with a reflector, expecting to do ok, and then to go for something like an 8" F3.9 if it worked out.

The faster the scope, the more critical is collimation, squareness and focusing. So, if you find f/5 a handfull, f/3.9 will be more so.

[alacant]

14 hours ago, Adam J said:

concenter eye piece

Hi

I don't think it's a regular collimator is it? Instead, how about a simple Cheshire sight tube? One with cross hairs so you can get the secondary in place, even better. No need to square anything or do a star test. Have another read of the collimation myths:

If you want perfect -small- stars right into every corner, it's gonna have to be the 4 element gpu

But IMHO, just as well correcting coma and tilt in software.

Anyway, good luck and clear skies.

Edited January 30, 2019 by alacant
gpu not gpl

[alexbb]

I should've posted some images made with the 130PDS here too. I'll just link now to the last one.

I must admit that the SW coma corrector does add some extra halos and I must invest in a Baader MPCC. I found that I need some extra adapters for my current setup in order to screw the CC inside of the focuser with an adapter instead of just putting it in an eyepiece holder. Neither the ASI1600 + the ZWO filters help too much. Besides the occasional halos resulted when a bright star is nearby, I get microlensing halos too. I'll just have to live with this for a while.

The Orion nebula shot with the 130PDS at the beginning of the Orion season: