How to improve to the next level? M101.

[SteveBz]

Hi Guys,

I didn't expect to be able to take photos at this time of year, but in fact it has been fine.  Just seems a bit warm for the poor old DSLR, which is pumping out noise.  I'm writing to get some suggestions on what to do next.  Here is an image of M101 taken over two of the last three nights (22nd and 225th June) at ISO400 on a Nikon D5000 DSLR with coma correction and light pollution filter. 

It's 63 3-minute lights (3h9m), plus darksx40, flatsx100 and biasx100.  Scope is Celestron 200mm f/5 Newtonian with goto EQ5 mount.  Guiding is QHY5 + guidescope + PHD2.  The nights had different temperatures by about 10 degrees (12C and 20C).  I took darks both times, but my DSLR does not have a sensor temperature indicator so I had to use the ambient temperature, which is only approximate.  The second night was warmer and noisier.

Processing is as follows:

1. Stack RAWS from each night separately with matching darks (pls flats and biases) with DSS to get calibrated files for the whole period.
2. Stack calibrated files from all nights to produce single .fts image.
3. Apply ARCSINH stretch and colour balance (from SIRIL package) and save as .tif
4. Import into GIMP.
5. crop.
6. Use 'Curves' to stretch everything upward in a single arc.
7. Use 'levels' iteratively to balance colour and darken sky.
8. Use 'Curves' again to apply an S-curve, to darken sky and stretch Galaxy and stars further.
9. Export to .png and .jpg for posting.

So I can still see a lot of noise, much of which is fixed pattern. 

So my real question is, how do I take this to the next level? 

Thanks in advance.

Steve.

 

 

 

[Wyvernp]

Without spending any extra money;

 - Dither if you aren't already.
 - Can't think of anything else

Other than that a cooled CMOS/CCD is a fantastic upgrade in a lot of ways but it is an expensive one, more so if you decide on mono. But you'll be able to have a dark frame library so will save time not having to take them every time as well as greatly reduced noise.

[SteveBz]

1 hour ago, Wyvernp said:

Without spending any extra money;

 - Dither if you aren't already.
 - Can't think of anything else

Other than that a cooled CMOS/CCD is a fantastic upgrade in a lot of ways but it is an expensive one, more so if you decide on mono. But you'll be able to have a dark frame library so will save time not having to take them every time as well as greatly reduced noise.

Thanks for that.  I guess that's what I was worried about.  I was planning to fix my dithering, sometimes I do, sometimes I don't but I had difficulty sorting out the settle time.  I also thought of going OAG, but the cost of a new camera like a zwo asi290 is also quite high.

But I've been thinking about getting a cooled camera for a while, it's just out of my pocket at the moment.  Which one in the ZWO range would you recommend?  (I'm raspberry pi based, so it has to have a linux driver.).  I do think that's really the correct choice.

I was also wondering if there was some post-processing I could do to help, like splitting into layers and using despeckle, or high-bandpass filters etc, before recombing?

I've seen this stuff done, getting great results, but I don't really know what the method is.

Regards,

Steve

[SteveBz]

1 hour ago, Wyvernp said:

Without spending any extra money;

 - Dither if you aren't already.
 - Can't think of anything else

Other than that a cooled CMOS/CCD is a fantastic upgrade in a lot of ways but it is an expensive one, more so if you decide on mono. But you'll be able to have a dark frame library so will save time not having to take them every time as well as greatly reduced noise.

Actually, possibly QHY too. I've tried both manufacturers and they both work eventually.

[Wyvernp]

1 minute ago, SteveBz said:

Actually, possibly QHY too. I've tried both manufacturers and they both work eventually.

Personally I use a QHY163m and am very happy with it. very little noise, no or unnoticeable amp glow and it uses the same sensor as the ASI1600. Although I think the drivers / software is a little less polished than the ZWO range. But it is considerably cheaper.

For your 1000mm focal length you should be fine with a guidescope as long as its focal length is no  around 4x less than the main scope, and even then it will depend on the pixel size of your cameras.

Have you check astronomy.tools? they have a good ccd suitability calculator which you can use to match up your scope to camera.

[SteveBz]

33 minutes ago, Wyvernp said:

Personally I use a QHY163m and am very happy with it. very little noise, no or unnoticeable amp glow and it uses the same sensor as the ASI1600. Although I think the drivers / software is a little less polished than the ZWO range. But it is considerably cheaper.

Nice, I'll check it out.

33 minutes ago, Wyvernp said:

For your 1000mm focal length you should be fine with a guidescope as long as its focal length is no  around 4x less than the main scope, and even then it will depend on the pixel size of your cameras.

I sort of agree.  The OAG would just be for show really.  I think I could get a similar effect by eliminating my mirror-flop during collimation.

35 minutes ago, Wyvernp said:

Have you check astronomy.tools? they have a good ccd suitability calculator which you can use to match up your scope to camera.

No I'll check it.

I see you're local. I'm going to PM you.

Steve.

[GiorgioF]

Dither. Take bias and not dark. Do not use the light pollution filter. Keep histogram at the middle. 

Galaxies are emitting in the whole light spectrum. Using a light pollution filter you cut also a bunch of signal.

Flat will avoid the gradients.

;)

[SteveBz]

2 minutes ago, GiorgioF said:

Dither. Take bias and not dark. Do not use the light pollution filter. Keep histogram at the middle. 

Galaxies are emitting in the whole light spectrum. Using a light pollution filter you cut also a bunch of signal.

Flat will avoid the gradients.

Hi Giorgio,

Thanks for your reply:

Dither => Ok. Seems right.

Bias not dark => Why?  I took bias AND dark.

LP Filter => Really? I'll try.

Flats => I have flats, but perhaps I should take new ones.

Regards,

Steve.

[GiorgioF]

28 minutes ago, SteveBz said:

Hi Giorgio,

Thanks for your reply:

Dither => Ok. Seems right.

Bias not dark => Why?  I took bias AND dark.

LP Filter => Really? I'll try.

Flats => I have flats, but perhaps I should take new ones.

Regards,

Steve.

About bias, just try. I was sceptical about since I tried after a friend suggested me (I was still with a Nikon d700 stock. Once saw the result, I never went back, even with the canon baader.

dither + bias has same effect as dark. There is some study around with a lot of explanation. I trust on my eyes.

If you are in high light polluted area like me, flat will help a lot. Post-production will be more easy.

 

[SteveBz]

 

22 minutes ago, GiorgioF said:

About bias, just try. I was sceptical about since I tried after a friend suggested me (I was still with a Nikon d700 stock. Once saw the result, I never went back, even with the canon baader.

dither + bias has same effect as dark. There is some study around with a lot of explanation. I trust on my eyes.

If you are in high light polluted area like me, flat will help a lot. Post-production will be more easy.

 

I looked at your photos and they are really nice, so I'll try your suggestions.

How did you get the ones with no stars?

Tx.

Steve.

[GiorgioF]

Nice? Oh, thank you! Living in a high pollution area, with really few chances of clear sky, I try to get as much as possible from my poor data.

The starless version is done in pixinsight with the starnet+ process. It's a sort of plugin as it's not included in the main software but it's fantastic.

[Wyvernp]

4 minutes ago, GiorgioF said:

Nice? Oh, thank you! Living in a high pollution area, with really few chances of clear sky, I try to get as much as possible from my poor data.

The starless version is done in pixinsight with the starnet+ process. It's a sort of plugin as it's not included in the main software but it's fantastic.

There is a standalone version too, not used it as I'm a pixinsighter... 

available here https://sourceforge.net/projects/starnet/files/v1.1/

I think theres a pretty good thread on it here

 

 

[SteveBz]

6 minutes ago, GiorgioF said:

Nice? Oh, thank you! Living in a high pollution area, with really few chances of clear sky, I try to get as much as possible from my poor data.

The starless version is done in pixinsight with the starnet+ process. It's a sort of plugin as it's not included in the main software but it's fantastic.

OK, I don't have Pi, so I just have to mock up what people do in other products on GIMP.

Regards

Steve.

[SteveBz]

1 minute ago, Wyvernp said:

There is a standalone version too, not used it as I'm a pixinsighter... 

available here https://sourceforge.net/projects/starnet/files/v1.1/

I think theres a pretty good thread on it here

 

 

Great there's a Linux version. I'll try it.

[SteveBz]

40 minutes ago, Wyvernp said:

There is a standalone version too, not used it as I'm a pixinsighter... 

available here https://sourceforge.net/projects/starnet/files/v1.1/

I think theres a pretty good thread on it here

 

 

And here it is:

50 minutes ago, GiorgioF said:

The starless version is done in pixinsight with the starnet+ process.

Great job guys.

Steve.

[Wyvernp]

Good work! Although as soon as you mentioned you were after the linux version I knew it wouldn't be long before we saw the results.

Oh by the way, I'm always happy to share my imaging data if anyone wants to practice with it. 

[GiorgioF]

22 minutes ago, SteveBz said:

And here it is:

Great job guys.

Steve.

Good one. Try also on nebular subject. There you can have a more impactful effect.

[Wyvernp]

 

17 hours ago, GiorgioF said:

Good one. Try also on nebular subject. There you can have a more impactful effect.

I just did this as part of the processing for my veil mosaic, although I prefer it with stars it does have quite an impact.

[GiorgioF]

2 hours ago, Wyvernp said:

 

I just did this as part of the processing for my veil mosaic, although I prefer it with stars it does have quite an impact.

In this way you have free hands to elaborate the nebulosity and more stretch options. Th n you can put back stars with a maybe more light process and keep them small. 

Btw, great image!