Jump to content

Banner.jpg.b83b14cd4142fe10848741bb2a14c66b.jpg

First dso advice please.

SkyExplorer

By SkyExplorer
in Imaging - Discussion

Recommended Posts

SkyExplorer

SkyExplorer

Posted
Posted

It looks like its going to be fairly clear tonight so I want to try and get out to image a dso.

Can anyone suggest a good dso for a beginner or are they all the same in terms of ease of caputuring ? (maybe a silly question)

Maybe something near the constellation of cygnus, like M27, M39 or NGC7000 as it failry high up in the sky early on and so should not suffer as much from light pollution??

I'm going to be using my HEQ5, with 80ED and Canon 450d at ISO800, with this in mind should I take a series of say 120x30 second subs?

Should I also take say 10 dark frames before I start, 10 half way thorugh and 10 at the end?

Any advice welcome:)

Steve

Link to comment
Share on other sites
  • Replies 45
  • Created
  • Last Reply
mark7331

mark7331

Posted
Posted

M27 is quite a good target and high in the sky at the moment so the seeing should be ok although it may be a little small for your field of view. What about M45 - the Pleiades. It's bright, large and you can take images of the whole thing and portions depending on your fov. :)

EDIT: and yes take darks so that they're at the same temperature as the lights. We'll need a DSLR user to comment on the ISO but lots of light subs are good. :(

Mark

Link to comment
Share on other sites
mark7331

mark7331

Posted
Posted

Sorry didn't really think about the time! I have a bit of a cold and the brain isn't firing on all cylinder(s) :) M45 will be in a good position at around 9:30pm ish.

A couple of other ideas that are up there now.

M13: The Great Cluster in Hercules is really bright and one of those "take your breath away" objects.

M31: The Andromeda Galaxy - really huge and bright.

Have a good one and let us know how you get on.

Link to comment
Share on other sites
SkyExplorer

SkyExplorer

Posted
  • Author
Posted

Well I got out, (it was quite warm outside compared to the other night) and started off with 15 dark frames at 30seconds each. I then pointed to M13 and started taking my light frames, to start with 70x30second subs. I then took 10 more dark frames followed by another 50x30sec subs followed by another 10 dark frames.

I used RAW and ISO800 (as advised by George from my other thread).

The last 20 subs were ruined as M13 had just managed to go behind the tall shrub we have in the garden (that's getting chopped down at the weekend :)) Although I'm sure the wife will have something else to say about that :( !!

So I then pointed the scope at M31 and took a test 2 minute sub to see if I could see any trails, it all looked okay so I took 20x2min subs of M31 followed by 5x2min darks.

How many bias frames do I need? 10?

Now to the processing :)

Link to comment
Share on other sites
mark7331

mark7331

Posted
Posted

Sounds like you captured plenty of lights of M13 and a good number of darks. The number of darks for your M31 images (5?) is a bit low but should be ok.

The bias signal is already present in your dark frames. Darks are bias plus noise generated during the exposure so you don't need any bias frames. You only use them if your going to "stretch" your darks i.e. use them for a different exposure length.

The last 20 subs were ruined as M13 had just managed to go behind the tall shrub we have in the garden (that's getting chopped down at the weekend :mad:) Although I'm sure the wife will have something else to say about that :) !!

I have a Hawthorne that's just about to suffer the same fate! Anyway - tell your wife it's all in the name of science! :D

What are you using for processing? In my opinion it's is more complex than capturing the data!

Mark

Link to comment
Share on other sites
SkyExplorer

SkyExplorer

Posted
  • Author
Posted

yeah, the 5 darks for M31 are a bit low, but M31 was a bit of an after thought as I had some time left after capturing M13 and I wanted to see if I could get 2 min subs unguided.

What are you using for processing? In my opinion it's is more complex than capturing the data!

My thoughts exactly Mark. I've downloaded DSS, so I'll try and stack the images, although not sure if there are any better settings in there other than the defaults.

As for processing I have Gimp GIMP - The GNU Image Manipulation Program which is a great little tool, but at this stage it only support 8 bit images, v3 will support 16-bit.

Do I need to consider doing anything else? I will need to reduce the orange glow from the images at some point as well.

Link to comment
Share on other sites
mark7331

mark7331

Posted
Posted

I think DSS defaults will be ok. It pays to experiment though. GIMP is ok but as you said 8-bit.

I've struggled with processing, and still do to some extent, but recently downloaded the demo of PixInsight and one of a major benefits is that you can convert the data (including darks) into 32-bit floating point format. It means that any stretching etc is done on a more subtle level. You don't get grainy images after processing. It's a few quid and a bit complicated but you get 50 ish days to try it. It would also help remove "background" noise like moon wash and gradients and I found that PI aligned the subs much better than anything else I've used.

Maybe worth a try?

EDIT: The 5 darks are still ok though and I'd be interested to see one of the 2 minute lights to see how well your tracking is unguided. :)

Mark

Link to comment
Share on other sites
SkyExplorer

SkyExplorer

Posted
  • Author
Posted
The 5 darks are still ok though and I'd be interested to see one of the 2 minute lights to see how well your tracking is unguided.

So would I :) Have not seen them yet, took them last night packed the kit up and went to bed. Hopefully they will be okay when I look at them later. I hope they are in focus :mad: I did zoom on using live view on the laptop and focused on vega as it is nice and bright.

Link to comment
Share on other sites
astroimpulse

astroimpulse

Posted
Posted

Looking forward to seeing these.

As for the shrub...you're lucky. The perfect place for an Obs in my garden means the beloved two apple trees will be in the way of S-W views. There is no chance in hell I'd be allowed to chop them down.

Such a big garden and not a good place to put an Obs :mad:

Anywho...I've subscribed to this thread so I'm looking forward to your results :)

Link to comment
Share on other sites
astroimpulse

astroimpulse

Posted
Posted

10Mb jpeg...

Oops. Sent instead of go advanced :)

10Mb jpeg will more than likely mean too large in dimensions. Reduce it to around 600 wide for easy viewing or a bit larger. No need to compress these days. But I suspect it's around 2-3000px wide?

Link to comment
Share on other sites
astroimpulse

astroimpulse

Posted
Posted

Open it in PS. Click control and L. Select red from the drop-down channel box, pull the black (left slider) up to the beginning of the peak. Do the same for green and blue and the image will improve just from that simple tweak. Lots more can be done but it's a fast way to improve drastically.

Link to comment
Share on other sites
SkyExplorer

SkyExplorer

Posted
  • Author
Posted

Thats just one 2 min sub. I don't have PS and Gimp (which I do have) only supports 8 bit images.

I just stacked M13 and when I opened it in Gimp almost all the detail went.

Just looked at photoshop web site and they offer a free trial, is it CS5 that I want??

Link to comment
Share on other sites
astroimpulse

astroimpulse

Posted
Posted

To be honest, I have no experience of Gimp on Linux so I don't know if that's fine for your needs (instead of getting PS).

I would have thought it would be as every time I mention to my linux pals I'm thinking about going there they mention gimp.

Does it have the ability to edit curves and levels?

One of the more experienced astrophotographers will chime in for sure.

But looks like a lot of detail from just 2mins. I did the quick level tweak and it's bought out a lot of detail :0

Link to comment
Share on other sites
astroimpulse

astroimpulse

Posted
Posted

This is a super quick tweak (under 10 seconds). It needs a lot more balancing but it's a good example of what a difference a minor change to just part of the levels will do.

The guys who use Deep Space Stacker will be the best to advise on that as I haven't used it...yet :)

Edit: By super quick I mean under 10 seconds. A lot more can be achieved.

post-21451-133877497336_thumb.jpg

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.