M13 Globular cluster in Hercules

[AstroMuni]

Here is my attempt on capturing M13 last weekend. Consists of just 30mins worth of data taken with the ASI224mc on the Celestron Astromaster 130EQ OTA mounted on HEQ5 pro. Stacked in SIRIL and processed using a combination of Siril & Gimp.

Comments and suggestions welcome 🙂

Edited July 1, 2022 by AstroMuni

[ollypenrice]

So much is right in this image. The star colour is great, the background is flat and neutral except for that small bit bottom right, which would be an easy fix. Neither of these things is at all easy to get right.

Where it could be better is in the focus, which I strongly suspect to be a little off. How did you focus? A Bahtinov mask is an inexpensive and reliable solution. Focus also needs checking regularly.

Olly

[Ratlet]

18 minutes ago, ollypenrice said:

So much is right in this image. The star colour is great, the background is flat and neutral except for that small bit bottom right, which would be an easy fix. Neither of these things is at all easy to get right.

Where it could be better is in the focus, which I strongly suspect to be a little off. How did you focus? A Bahtinov mask is an inexpensive and reliable solution. Focus also needs checking regularly.

Olly

There is a wonderful sense of depth to this capture as well.

[vlaiv]

26 minutes ago, ollypenrice said:

Where it could be better is in the focus, which I strongly suspect to be a little off. How did you focus? A Bahtinov mask is an inexpensive and reliable solution. Focus also needs checking regularly.

That is probably not going to happen as AstroMaster 130 has spherical mirror at F/5. What you are seeing is not focusing error but rather spherical aberration:

https://www.celestron.com/blogs/knowledgebase/does-my-astromaster-130-have-a-spherical-or-parabolic-mirror-what-is-the-difference

[ollypenrice]

1 minute ago, vlaiv said:

That is probably not going to happen as AstroMaster 130 has spherical mirror at F/5. What you are seeing is not focusing error but rather spherical aberration:

https://www.celestron.com/blogs/knowledgebase/does-my-astromaster-130-have-a-spherical-or-parabolic-mirror-what-is-the-difference

Ah yes, I'd overlooked that fact.

Olly

[vlaiv]

@AstroMuni

Although telescope has spherical mirror - it does not mean you can't take images with it. You just need to work within its limitations. This means no high resolution work (or you can but image will look a bit out of focus).

What you can do is make mosaics with it. If you reduce resolution to 1/3 of present - you will get rather sharp and good looking image - like this:

 

Now for a moment imagine that this small image is just central part of large image - with larger fov resembling something like this:

I'd say that no one could say that such image is lacking focus or anything like that.

Trick is just to make 3x3 mosaic with your camera (and bin this data x3). It is a bit more involved but result will be much better.

[alacant]

2 hours ago, AstroMuni said:

30mins worth of data

30 minutes. Amazing. Well done.

I had a go using your png. Try deconvolution on the linear file and you should be in business. You've loadsa detail:

Edited May 23, 2022 by alacant

[AstroMuni]

15 hours ago, vlaiv said:

Trick is just to make 3x3 mosaic with your camera (and bin this data x3). It is a bit more involved but result will be much better.

Thanks. One for next time 🙂

[AstroMuni]

14 hours ago, alacant said:

Try deconvolution on the linear file and you should be in business. You've loadsa detail:

Yes, there is lots of data in there for 30mins and I was amazed. Which software did you use for deconvolution and what settings. I had applied default deconvolution on this image in Siril.

[AstroMuni]

16 hours ago, ollypenrice said:

Where it could be better is in the focus, which I strongly suspect to be a little off. How did you focus? A Bahtinov mask is an inexpensive and reliable solution. Focus also needs checking regularly.

I have and do use the Bahtinov mask. I focus before doing a session, but its hard with the standard focuser on the Astromaster and its not an easy task (I'm no great DIY expert) to replace this one with a better focuser. And as Vlaiv has already said, I am dealing with a spherical mirror after all so I have those limitations

But hey make the most of what I have is my policy, until I upgrade.

[ollypenrice]

31 minutes ago, AstroMuni said:

I have and do use the Bahtinov mask. I focus before doing a session, but its hard with the standard focuser on the Astromaster and its not an easy task (I'm no great DIY expert) to replace this one with a better focuser. And as Vlaiv has already said, I am dealing with a spherical mirror after all so I have those limitations

But hey make the most of what I have is my policy, until I upgrade.

Ignore my doubts about focus. I think you must be getting close to what the system can deliver. Good going.

Olly

[Clarkey]

8 hours ago, AstroMuni said:

But hey make the most of what I have is my policy, until I upgrade.

There was a 130 PDS on AB&S which might be worth a punt.