M57 Hit a bit of a wall.

[SteveBz]

Hi Guys,

I feel I've hit a bit of a wall with my imaging generally.  Here's an example with M57.  At a distance (like this) it looks quite nice, but as you drill down (see below), the detail is just not there.

This is the best 2.5 hours of three hours imaging last night.

• Temperature about 17 C.
• ISO 1600.
• D5000 Nikon
• 90 x 120secs guided with dithering.
• BIASES & FLATS,
• DARKS a bit old.  Probably need to retake them. 
• Stacked with Siril with dark optimisation.
• asinh stretch x500
• photometric color balancing
• deconvolution
• levels.

Here's a crop.  As you can see the first star (the white dwarf) in M57. Is just visible, but the second one to the West of the first one (the right on the photo).  Is hardly visible.

I don't feel anything went wrong last night.  The focusing was pretty much there, the guiding was OK.  I think the collimation is OK, although I'm never quite sure.

The camera is old, uncooled and no thermometer in the sensor, so I can only go by the ambient temperature.

And really, apart from spending 5k on an equipment upgrade, I don't see what I can do.  Has anyone tried drizzel?

Thanks for your ideas.

Steve.

 

[bottletopburly]

 Hi try dropping iso to 400 for better dynamic range  http://dslr-astrophotography.com/iso-values-nikon-cameras/ ,and more data try for at least 4hrs min the more the merrier and try longer subs if possible i tend to use 240 sec subs 

[MarkAR]

I think this is mostly a case of focal length or lack of. Might be worth getting a TeleVue Powermate.

If you have dithered whilst imaging, it would be worth trying drizzle. You could then probably crop in closer.

[SteveBz]

11 minutes ago, bottletopburly said:

 Hi try dropping iso to 400 for better dynamic range  http://dslr-astrophotography.com/iso-values-nikon-cameras/ ,and more data try for at least 4hrs min the more the merrier and try longer subs if possible i tend to use 240 sec subs 

Hi @bottletopburly,

Thanks for that chart, I've seen it (or a similar one) before, and I have tried a number of different ISOs, 400, 800 and 1600.  I felt my darks came out better (for reasons I don't understand) and that my camera noise (which is always a limiting factor) was less at 1600.

Do you feel dynamic range is a problem here?  What are the symptoms?  I always imagined it was just a matter of how much you could stretch it.

Thanks for your input.

Regards

Steve.

[SteveBz]

14 minutes ago, MarkAR said:

I think this is mostly a case of focal length or lack of. Might be worth getting a TeleVue Powermate.

If you have dithered whilst imaging, it would be worth trying drizzle. You could then probably crop in closer.

I did borrow a TeleView from a friend last year and I did get a better image.  I might think about investing in a Big Barlow later this year.

Regards,

Steve.

[bottletopburly]

It’s all to do with signal to noise you gain nothing with a higher iso  ,assuming the D5000 is iso invariant .

[SteveBz]

On 31/07/2020 at 10:50, MarkAR said:

I think this is mostly a case of focal length or lack of. Might be worth getting a TeleVue Powermate.

If you have dithered whilst imaging, it would be worth trying drizzle. You could then probably crop in closer.

So I tried drizzling, I'm not sure there's any difference.  What do you think?

Steve.