Deep sky imaging advice

[Celestron4]

I have an image of M51 taken over two nights in the last month. It currently stands at about 2 hrs with of 3 minute exposures and I am planning to add more the I next get the chance. I would like to be able to get more detail (bring out the dust lanes, etc) and was wondering how to do this. Should I be looking at a filter of some sort?

My imaging scope is a Celestron Nextstar Evolution 6 and I am using an unmodified Canon EOS 1100d DLSR to take the images. According to the Clear Outside app, I have class 4 Bortle skies if this helps.

 

[JoshHopk]

I believe that for dust lanes and other faint details, you may have to use longer exposures. 

I’m unsure if a Ha or other filters would bring any benefits.

[Celestron4]

Thanks for the advice. I am looking at Ha filters but am using an unmodified DLSR so not sure how well it would work. Longer exposures is something I am definitely looking at trying. 

[tomato]

Lots of shorter exposures will work better than fewer longer ones, particularly if you are not using a dedicated Astro camera with cooling, as you are with your DSLR.

A Ha filter needs longer exposures as it is collecting light at a very narrow band of wavelength, specifically from hydrogen emission nebulae. This won’t be needed however to pick out dust lanes in galaxies, you just need more total exposure time. Class 4 sky is OK, try to image when the moon is out of the way, as this will improve the quality of the data.

How does your 2 hours of data look on M51? I bet there are some dust lanes visible already.

[Celestron4]

here is some detail. I may have gone slightly overboard with the sharpening but still seems to be lacking colour. Would Ha make much much difference or is it just a limitation with the camera that I am using? 

[Celestron4]

Have you got any advice on how to improve the image?

[johngm]

13 minutes ago, Celestron4 said:

Have you got any advice on how to improve the image?

Is this any better ?

 

 

[happy-kat]

I think that's a very good image and you have good star shapes which can be challenging with altaz imaging on your mount.

I would watch the background as that is very dark and you could be loosing some faint detail.

Edit- link removed OP is using an EQ mount

Edited May 22, 2020 by happy-kat

[johngm]

Obviously, i was only working with a JPEG image. Just did a curve adjustment to the Highlights of the Red channel in PS, and increased Saturation and contrast.

John 

[johngm]

3 minutes ago, happy-kat said:

I think that's a very good image and you have good star shapes which can be challenging with altaz imaging on your mount.

I would watch the background as that is very dark and you could be loosing some faint detail.

You might like this thread.

https://stargazerslounge.com/topic/228101-the-no-eq-dso-challenge

Yes, i'll second that. Great image, but careful about clipping the data. As regards acquiring more data,  more is good 👍

John

[MarkAR]

To start with I think you might have some pretty good data. You could take some more exposures at say 4 mins which will help a little with the fainter dust lanes.

When it comes to post processing, little by little is better. Don't try to make the background too dark as you will hide faint dust as well as any left over background noise. 

Push colour curves around gently to see what works best, the same with sharpening. 

[wimvb]

You have a very nice image already. As for the use of an Ha filter; this is ONLY of use if you image emission nebulae. With an unmodified dslr it's utterly useless.  Some unmodified cameras are sensitive to Ha, but most need to be modified to allow Ha imaging. As suggested by others, capture more data. I think you need at least 4-6 hours more for the really faint stuff. If your 3 minutes exposures lift the histogram on the lcd screen of your camera, from the left side, then don't change the exposure time. But if you see read noise in your subs, then increase the exposure time to, say, 5 minutes.

[Celestron4]

Thanks for the advice! I will have a go with longer exposures next time 8 get a clear night. It’s the colour on the smaller galaxy that on some images seems to be a bright orange. Not sure how to get that with my setup. I have a celestron AVX equatorial mount and I use PHD2 for auto guiding  if that explains the star shapes. Would a light pollution filter help at all?

[MarkAR]

I think the colour will come with more exposures and careful processing. A light pollution filter will mean taking even longer exposures as they cut out a fair bit of light. I wouldn't use one now if you are going to add the data to the first batch.

[DaveS]

A lot more data will certainly help, and will enable you to bring out the colour. Depending on where you are within Bortle 4 you may not need any kind of LP filter. As Wim has said, your DSLR isn't sensitive enough to H-alpha to pick up the HII regions. They are there but need a larger scale and mono camera with a NB filter to bring them out.

[carastro]

Modifying your camera, if probably the best way to improve you image, but if you don;t want to get it modified, I would suggest you buy one already modified from CheapAstrophotography.  It is really an uphill battle trying to use an unmodified DSLR for Astrophotography.  You have done well though, in what you have already captured.

Carole