M13 LRGB with 130pds

[alexbb]

Good evening to you all,

Last night I acquired 30x180s on each RGB so now I have a total of 37x180s each RGB, 60x60s lum from last year, 55x180s lum from this year and some shorter exposures for the core. That means ~5:33h of RGB and 3:45h of lum.
All taken with the ASI1600MMC and the 130PDS newton, horrible gradients when using the light pollution filter. I mean really horrible and uneven gradients. I also have a horizontal line at about 1/4 from the top reflected from somewhere.

The image below was stacked and merged with APP, I also made a synthetic lum from the RGB and included it in the final lum file.

Processing can be improved, for sure, but I have also another thought. Would maybe another 6h of luminance data be worthy on this target? Or should I move to something else, maybe M3 or M92?

Clear skies,

Alex

Astrobin: https://www.astrobin.com/341636/

Edit: almost 4 more hours of lum.

Edit2: 7 more hours of lum.

[Scott]

love the star colours

 

[pipnina]

12 minutes ago, moise212 said:

Good evening to you all,

Last night I acquired 30x180s on each RGB so now I have a total of 37x180s each RGB, 60x60s lum from last year, 55x180s lum from this year and some shorter exposures for the core. That means ~5:33h of RGB and 3:45h of lum.
All taken with the ASI1600MMC and the 130PDS newton, horrible gradients when using the light pollution filter. I mean really horrible and uneven gradients. I also have a horizontal line at about 1/4 from the top reflected from somewhere.

The image below was stacked and merged with APP, I also made a synthetic lum from the RGB and included it in the final lum file.

Processing can be improved, for sure, but I have also another thought. Would maybe another 6h of luminance data be worthy on this target? Or should I move to something else, maybe M3 or M92?

Clear skies,

Alex

And annotated: http://nova.astrometry.net/user_images/2041951#annotated

An amazing image moise

How are you liking the 130PDS? I have been contemplating one myself for an imaging setup and would love to hear opinions from an owner. I'm also curious as to what mount you use with it.

Knowing me I would move on to a new target if I had made an image like that. The gradient moving outwards reminds me of gradients I get with my camera lenses if I don't take my flats properly, so it could be worth experimenting with that.

[alexbb]

Thank you, Scott, Pipnina!

I somewhat like the 130PDS as it gathers a lot of light compared to my other scopes, but I have some mysterious issues with it. Besides that horizontal line, the gradients through the LP filter are so uneven that I don't even know where to start from. The G and B filters calibrate almost perfectly. The R a little worse, but... still better. I don't think that is the filter solely as I don't have such issues with it and other scopes. Same camera, filter wheel, etc.

I tried to take the flats with a tshirt pointing at the sky, pointing at an even illuminated surface, pointing at a full bright laptop screen, same issue.

I have to try the L filter instead of the LP one (IDAS-P2) and rule out at least the filter issue.

By the way, the scope is also flocked and the mirror moved a bit away from the bottom.

Other than this, I don't like the screw locking mechanism to hold the camera assembly, but if I tight them, it's ok.

The scope + camera + 8 position FW + OAG doesn't really balance properly, but it's at the limit.

I'm using it on an AZ-EQ5 mount and I correct it with a SW coma corrector which reduces the FL to ~588mm. I would prefer a better mount, with this one I can guide at 0.8-1.3" RMS usually, depending on the seeing. I didn't really want a heavier mount when I bought this one.

I might try maybe only one more night with the L filter so then I would reach 6-7 hours of luminance. That should do and I could also find out if the filter causes the weird issues.

[alexbb]

I added almost 4 more hours (106x120s) shot through the L filter. The weird gradients are gone; the horizontal line, not. Anyways, I managed to push it away to a certain degree. I edited the first post.

I will gather data on this target on 2 more moonless nights this season and I will call it an image.

[celestron8g8]

Gorgeous !! Got the companion too !

[alexbb]

Thank you, Ron!

[tooth_dr]

Stunning image. Loving the colours and big background galaxy. Fantastic. 

[alexbb]

Thank you, Adam!

[Jedi2014]

Hi Alex,

very nice rendition. I like the crisp look of the cluster. And colors are wonderful.

Jens

[alexbb]

Thank you, Jens!

[alexbb]

This is it. For a total 20.4 hours of data, 333min of RGB only, the image is at the bottom of the original post.

Thanks for looking!
Alex

[Adam J]

On 29/03/2018 at 21:59, moise212 said:

I'm using it on an AZ-EQ5 mount and I correct it with a SW coma corrector which reduces the FL to ~588mm. I would prefer a better mount, with this one I can guide at 0.8-1.3" RMS usually, depending on the seeing. I didn't really want a heavier mount when I bought this one.

 

If you are getting reflections it will be from the SW coma corrector they are notorious for it. 

I have the 130PDS, the ASI1600mm pro and use the Baader MPCC Mk3, I dont see these issues. 

[alexbb]

3 minutes ago, Adam J said:

If you are getting reflections it will be from the SW coma corrector they are notorious for it. 

I have the 130PDS, the ASI1600mm pro and use the Baader MPCC Mk3, I dont see these issues. 

In the images above I don't see too big reflections on the brighter stars. However, this doesn't seem to be the case with my O3 (Optolong) filter which is terrible with the reflections and, to a smaller extent, neither with the Ha filter.

So the first bad factor are my narrowband filters, then the coma corrector. I did get some horrendous gradients with the IDAS P2 LP filter, but with the L filter it seems manageable.

Other issues arise towards the corners, I believe due to the small-ish secondary which I'm planning to replace at the next full moon.

I think I didn't have yet imaged a very bright star with the LRGB filters to have a realistic opinion about how they perform, however, I believe I won't invest too much any more in this scope. It is flocked already, the primary is moved a bit inwards, I will replace the secondary and cut a bit from the focuser. If still not satisfied, I will go for a larger and much better made 6" or 8" F4 newt or the refractor way.