Imaging the Pleiades

[gonzostar]

Hi Thinking about my nect project

With my set up, 102mm APO F7 refractor, with a unmodded canon 70d Camera on aAvx mount

I am after some hints on this project. Mainly do i for long exposures say 3-5 mins to capture the nebulosity around the stars. But the saturate the pixels with the brighter stars.

Or lots and lots of say 30s light frames?

Any opinions much appreciated

 

Cheers

Dean

[Star101]

Having just done the 600s subs using my ATIK 4120EX OSC camera and fairly pleased with the results. I have decided to try again while Pleiades is easily available. using much shorter 30s subs instead.

Here is my 600s M45. https://www.astrobin.com/367718/?nc=user

It's a matter or personal preference but, I think shorter exposures would be better.

 

 

[JohnSadlerAstro]

Hi,

I went for 2-3min subs on my attempt a year ago, I didnt get anywhere near enough data though, and at the time I wasn't dithering so the image wasn't a massive success. I was able to capture quite a bit of the nebulosity, it really is (comparatively) very bright but for the broader areas of nebula around the cluster you will probably be needing 5 min subs. Hopefully this will help give an idea of what you can capture.  

[gonzostar]

21 minutes ago, Star101 said:

Having just done the 600s subs using my ATIK 4120EX OSC camera and fairly pleased with the results. I have decided to try again while Pleiades is easily available. using much shorter 30s subs instead.

Here is my 600s M45. https://www.astrobin.com/367718/?nc=user

It's a matter or personal preference but, I think shorter exposures would be better.

Thats a cool image i would very happy if i could get near that quality  

 

 

[gonzostar]

23 minutes ago, JohnSadlerAstro said:

Hi,

I went for 2-3min subs on my attempt a year ago, I didnt get anywhere near enough data though, and at the time I wasn't dithering so the image wasn't a massive success. I was able to capture quite a bit of the nebulosity, it really is (comparatively) very bright but for the broader areas of nebula around the cluster you will probably be needing 5 min subs. Hopefully this will help give an idea of what you can capture.  

I like this image to. Certainly worth ago. Thanks for showing the image.  

[StuartJPP]

I used 3 minute subs on an f/4 scope (lens) using an unmodified canon 5D Mark 3 a while ago and found that was the sweet spot for me. The sweet spot being able to get enough data on each sub, not losing too much time on lost subs and getting enough subs for stacking algorithms to do their job (>25 or so). I was also unguided at the time and felt going longer than 3 minutes would have introduced too much drift.

F/7 is nearly 4x as slow as f/4 so personally I would stick with longer subs. Of course it also depends on the ISO you are using...don't want to oversaturate the stars.

This was imaged in a fairly dark area in Scotland.

 

 

[ollypenrice]

I think the easiest way is to look at the linear subs from any given exposure time. This will show you the extent of any saturation in the bright stellar cores. Using a CCD camera with deep wells I found no need to go shorter than 15 minutes. So I'd try the longer subs, which go deeper in search of that wonderful nebulosity, including some faint reds, and look at the cores. If the stars are looking like large saturated blobs before stretching then shoot a quick set of shorts as well. You'll only be using the brightest parts of the short subs so there is no need to worry about noise, meaning a few will do. Make sure that you really are looking at the linear data though. Some capture programmes will apply an auto stretch. This must be disabled.

This http://www.astropix.com/html/j_digit/laymask.html will explain how to combine them.

Olly

[gonzostar]

14 hours ago, StuartJPP said:

I used 3 minute subs on an f/4 scope (lens) using an unmodified canon 5D Mark 3 a while ago and found that was the sweet spot for me. The sweet spot being able to get enough data on each sub, not losing too much time on lost subs and getting enough subs for stacking algorithms to do their job (>25 or so). I was also unguided at the time and felt going longer than 3 minutes would have introduced too much drift.

F/7 is nearly 4x as slow as f/4 so personally I would stick with longer subs. Of course it also depends on the ISO you are using...don't want to oversaturate the stars.

This was imaged in a fairly dark area in Scotland.

 

 

Thanks for link to thread. That truly is a great image. I am thinking of using ISO800. Unfortunately i am not in the deepest darkest Scotland, but the outskirts of glareish Brighton. Also i will be using a IDAS-D2 filter. So experiments needed  but thanks for the pointers Will start off with 3min subs and see how goes. Hopefully tonight!

[gonzostar]

9 hours ago, ollypenrice said:

I think the easiest way is to look at the linear subs from any given exposure time. This will show you the extent of any saturation in the bright stellar cores. Using a CCD camera with deep wells I found no need to go shorter than 15 minutes. So I'd try the longer subs, which go deeper in search of that wonderful nebulosity, including some faint reds, and look at the cores. If the stars are looking like large saturated blobs before stretching then shoot a quick set of shorts as well. You'll only be using the brightest parts of the short subs so there is no need to worry about noise, meaning a few will do. Make sure that you really are looking at the linear data though. Some capture programmes will apply an auto stretch. This must be disabled.

This http://www.astropix.com/html/j_digit/laymask.html will explain how to combine them.

Olly

Thanks Olly for your suggestions. I guess by Linear subs does that mean RAW unprocessed? Sorry for silly question. Because of the LP around these parts i will use the IDAS-D2 filter. But will try 3min possibly 5min  light subs. May be in the end go shorter. Part of the excitement of this hobby is the experimentation. 

Thanks for the link though will follow that through and give it a good go  

 

Cheers

Dean

[MartinFransson]

I went for loads of exposure on my DSLR M45. Not really knowing what was the optimal sub length I tried a few different, ranging from 3 to 8 minutes @ISO800 on my Canon 1100D. Here is 31*3 min + 87*5 min + 55*8 min, a total of 15+ hours. Granted this image is a bit over processed (I really wanted to bring out the dust), but it was taken at f/4 and the stars are not all that saturated so longer exposures are not a problem. For me, it was more the skyglow that limited the exposures.

If I had to do it again, I would probably stick with 3 or 5-minute exposures only, depending on the number of subs I could gather in my wanted time frame. I´d want at least 60-80 subs.

 

[gonzostar]

Thanks for your reply and link. very useful imfornation. Last night i had a hour or so gap before clouds rolled in and moon got to high. I tried various sub lenghts from 30s to 300s. I  think 3mins is good for my set up and LP conditions in my area. The histogram peaks (green and blue) where roughly half way.

How ever i did try a 5min light frame. The histogram was 3/4 to the right, Does this look to "washed out " to get a suitable picture.

MAYBE_LIGHT_300s_800iso_+13c_20181028-21h32m58s556ms.CR2

Would you think i could use 5 min exposures? I am using iso 800 as i already have darks for these settings

 

Thanks for help 

Dean

 

[ollypenrice]

Don't do this experiment in the moon time. Only do it when it's dark.

Olly

[gonzostar]

 

Thanks Olly, Here it only seems to be clear when its moon time  

[ollypenrice]

6 minutes ago, gonzostar said:

 

Thanks Olly, Here it only seems to be clear when its moon time  

This month it seems that we have the same problem!

Olly

[gonzostar]

Yes, but doesn't your darkest of dark sites block out the moon? ? 

[ollypenrice]

On ‎29‎/‎10‎/‎2018 at 21:45, gonzostar said:

Yes, but doesn't your darkest of dark sites block out the moon? ? 

If only...