Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Advice on Pleiades and DSS

  • Please log in to reply
11 replies to this topic

#1 Simon D.

Simon D.

    Vostok 1

  • -----
  • topic starter
  • Posts: 107
  • Joined: 31 Jan 2013
  • Loc: Canada

Posted 14 January 2020 - 06:50 PM

I’m planning the above for my next target, using a Canon 500mm f4 and unmodded Canon 5D IV, on an HEQ5, unguided.  I can get up to 2 minutes, which should be enough on a bright target. A couple of questions.  1) on this target, do folks take a second set of lower exposures to combine so they dont blow out the stars, or do you not worry about it? 2) if you do take a second set of lower exposures for the star cores, is there a way to automatically stack them in DSS with the other exposures to have one HDR image, or do you need to stack them separately  and combine after in Photoshop. PS I’ve downloaded a trial of Startools, so if that can merge the 2 sets, please let me know.  Thx



#2 Gipht

Gipht

    Vanguard

  • *****
  • Posts: 2,139
  • Joined: 12 Nov 2016
  • Loc: Prescott Valley, AZ.

Posted 14 January 2020 - 07:48 PM

I recently did Pleiades with at 330mm focal length, with a 70mm refractor using 2 minutes subs.  My results were fairly good for star color, with the brighter stars clipped.  At 500mm with a smaller aperture, my guess is that you will do better  in that regard then I did.  If you decide to take a second set at a reduced exposure  time, you can stack them  separately and then blend  them, or you can stack them all as one stack.  DSS allows you to click which light frames to stack, or you can group your stacks together.  Group tabs  appear at  the bottom  once you enter the first set of lights.  If you stack them separately, you probably will want to select a single reference frame in one of the stacks so everything can be overlaid easily.  To do this, right click on the desired light frame and a drop down menu will appear with reference frame at the top.

 

Here  is a link to a youtube video on HDR combine in Star Tools:  https://www.youtube....h?v=WqYim2phWLo

 

The darker your skies, the better the results will be.

 

Good luck!


  • Stephen S. likes this

#3 JDShoots

JDShoots

    Mariner 2

  • -----
  • Posts: 217
  • Joined: 03 Aug 2019
  • Loc: Pennsylvania, North East

Posted 15 January 2020 - 12:45 AM

I did the same thing, 500 f4 unmod'ed unguided, except Nikon.  I shot at 5.6 with 60 sec subs, all 2 and a half hours of it.  There is a lot of dust out there, so plan for a lot of subs.   I suppose if you are in a dark site, that is less important.  

 

A point to note with the StarTools trial version, you can't save you finished image.  I missed that when I tried it the first time.   But I liked it so I bought it, and used it on M45, this was my first attempt at The Pleiades, and second target using startools.  

 

This image was the first time I saw these huge diffraction spikes(but it was only my 4th target ever), I like them some people hate them.  They are a byproduct of the blown out stars and stopping down a little.  But these stars are so bright.  

I was also surprised to see the "straight" lines in the nebulosity, thought I made a mistake, so watch for that too:)  

 

Have fun! 

 

original.jpg



#4 the Elf

the Elf

    Vanguard

  • *****
  • Posts: 2,043
  • Joined: 06 Sep 2017
  • Loc: Germany

Posted 15 January 2020 - 06:27 AM

This is an unmodded Canon 800D at ISO 400, scope is f/6. As I post the link I see the description is wrong. It is 19x 4 minutes. Going to correct when I'm home. No shorter subs involved. The cores of the brighter stars are saturated but I don't mind. If you image at ISO 400 as well you can probably use 45sec or so at f/4. For other ISOs correct accordingly. For my non ISO invariant T3i I used 2 minute subs at ISO 800.

http://elf-of-lothlo...eiades2018.html

full res linked in the description



#5 Simon D.

Simon D.

    Vostok 1

  • -----
  • topic starter
  • Posts: 107
  • Joined: 31 Jan 2013
  • Loc: Canada

Posted 15 January 2020 - 03:51 PM

This is an unmodded Canon 800D at ISO 400, scope is f/6. As I post the link I see the description is wrong. It is 19x 4 minutes. Going to correct when I'm home. No shorter subs involved. The cores of the brighter stars are saturated but I don't mind. If you image at ISO 400 as well you can probably use 45sec or so at f/4. For other ISOs correct accordingly. For my non ISO invariant T3i I used 2 minute subs at ISO 800.

http://elf-of-lothlo...eiades2018.html

full res linked in the description

That’s super helpful.  Thanks.  Love your processing on it too. 



#6 Simon D.

Simon D.

    Vostok 1

  • -----
  • topic starter
  • Posts: 107
  • Joined: 31 Jan 2013
  • Loc: Canada

Posted 16 January 2020 - 08:22 AM

I did the same thing, 500 f4 unmod'ed unguided, except Nikon. I shot at 5.6 with 60 sec subs, all 2 and a half hours of it. There is a lot of dust out there, so plan for a lot of subs. I suppose if you are in a dark site, that is less important.

A point to note with the StarTools trial version, you can't save you finished image. I missed that when I tried it the first time. But I liked it so I bought it, and used it on M45, this was my first attempt at The Pleiades, and second target using startools.

This image was the first time I saw these huge diffraction spikes(but it was only my 4th target ever), I like them some people hate them. They are a byproduct of the blown out stars and stopping down a little. But these stars are so bright.
I was also surprised to see the "straight" lines in the nebulosity, thought I made a mistake, so watch for that too:)

Have fun!

original.jpg


Thanks. Which ISO did you use?

#7 JDShoots

JDShoots

    Mariner 2

  • -----
  • Posts: 217
  • Joined: 03 Aug 2019
  • Loc: Pennsylvania, North East

Posted 16 January 2020 - 09:39 AM

Thanks. Which ISO did you use?

ISO 200.  60" f5.6 and still had clipped highlights in the large stars.  

160 lights, 35 darks, 41 flats, and 130 bias frames.  



#8 Hesiod

Hesiod

    Gemini

  • *****
  • Posts: 3,490
  • Joined: 13 Jan 2013

Posted 16 January 2020 - 11:47 AM

I take a picture of Pleiades last fall (eos1100d @ ISO800, 230mm @f/4.2), with my rudimentary camera took 120" subs; probably could do better on brighter stars through a more accurate use of masks but was too lazy

gallery_215679_10936_1060600.jpg

 

I was more interested in the surrounding dust, so was more than willing to sacrifice the brightest stars for the sake of simplicity.


  • Smithry3 and Topographic like this

#9 the Elf

the Elf

    Vanguard

  • *****
  • Posts: 2,043
  • Joined: 06 Sep 2017
  • Loc: Germany

Posted 17 January 2020 - 01:40 PM

@Simon D.:

looking at this diagram

http://photonstophot... EOS 5D Mark IV

I'd recommend ISO 400 for your camera. It is a bit difficult to read. First ignore ISO 50, it is obviously extended. Also all the inter ISO are generally not good for astro. If you look at the full ISO (100, 200, 400, 800, etc.) and draw a line through them you see the line flattens in the upper end at ISO 100 and 200  and has a constant slope from ISO 400 on. The start of the constant slope is the best ISO for astro.

Unless you like the spices don't stop down your lens. If it needs to be stopped down for better performance get an aperture ring (stop ring? How is it called?) that is put in the filter thread to stop it down, leaving the internal aperture fully open. The effect on image quality is the same but without spikes.

Can someone who understands what ring I mean post a link? Can't find any. Thx!


Edited by the Elf, 17 January 2020 - 01:40 PM.

  • Ivo Jager likes this

#10 DubbelDerp

DubbelDerp

    Messenger

  • *****
  • Posts: 426
  • Joined: 14 Sep 2018
  • Loc: Upper Peninsula of Michigan

Posted 17 January 2020 - 01:58 PM

Step-down ring. They’re readily available online and cheap.

Here’s a link to a set, but you can usually get them in a large step increment as well, like a 58-52mm.

https://www.amazon.c...2xpY2s9dHJ1ZQ==
  • the Elf likes this

#11 DubbelDerp

DubbelDerp

    Messenger

  • *****
  • Posts: 426
  • Joined: 14 Sep 2018
  • Loc: Upper Peninsula of Michigan

Posted 17 January 2020 - 02:12 PM

I did 60-seconds at ISO 800 for mine with a Canon T3i/600D. The stars are definitely saturated, so dropping the exposure to 30 seconds or reducing ISO to 400 probably would have controlled it better. But I also really wanted to show the background dust. This was at 360mm f/6. I think it would be tough to blend in a stack of shorter exposures with all the background nebulosity without introducing weird halos around the brighter stars, but I'm sure it could be done in PS/GIMP.

M45 first attempt

 


  • the Elf likes this

#12 Simon D.

Simon D.

    Vostok 1

  • -----
  • topic starter
  • Posts: 107
  • Joined: 31 Jan 2013
  • Loc: Canada

Posted 20 January 2020 - 11:13 AM

@Simon D.:

looking at this diagram

http://photonstophot... EOS 5D Mark IV

I'd recommend ISO 400 for your camera. It is a bit difficult to read. First ignore ISO 50, it is obviously extended. Also all the inter ISO are generally not good for astro. If you look at the full ISO (100, 200, 400, 800, etc.) and draw a line through them you see the line flattens in the upper end at ISO 100 and 200  and has a constant slope from ISO 400 on. The start of the constant slope is the best ISO for astro.

Unless you like the spices don't stop down your lens. If it needs to be stopped down for better performance get an aperture ring (stop ring? How is it called?) that is put in the filter thread to stop it down, leaving the internal aperture fully open. The effect on image quality is the same but without spikes.

Can someone who understands what ring I mean post a link? Can't find any. Thx!

Thx Elf




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics