Canon 60DA

[astrodude]

I have been imaging with a canon entry level (500D) DSLR for a couple of years and recently I bought a Canon 60DA. When I use it the sky background becomes very bright very quickly which washes out the target I am trying to image. I have seen some great images taken with a Canon 60da, I wonder if any members use this camera - am I doing something wrong.

[frugal]

The 60Da will be more sensitive, so it will be captuing more light, it will also be more sensitive at the red end of the spectrum which will be bringing in more signal. I have a stock 60d and I can manage 900 second exposures under semi-rural light pollution conditions. The images look very bright and washed out if i look at them in Canon's DPP or Adobe Bridge, however when they are stacked together and stretched the data is all there.

[astrodude]

Thanks for your reply Frugal, up until now I have not been guiding so I have been using relatively short exposures of 2-3 minutes. This means the sky background seems fairly dark and "nice" to look at in the freshly captured images. At 3 minutes on the 60DA the background is light grey and it makes the target difficult to see. So I do not need to worry about this? I thought perhaps I was doing something wrong. 

[wxsatuser]

How dark are your skies?

If you have LP then the exposures will be short, an LP filter will get you longer subs.

Out of interest.......what settngs and what scope/lens.

[astrodude]

Guernsey, west coast. So the skies are pretty dark. The only filter I use is a clear glass one to protect the camera chip. I am using a william optics FLT132 which is F/7. I try to image at about ISO 800 or 1600. It is just such a difference between a normal Canon DSLR and the DA. I can't help thinking I have a setting wrong.  

On a slightly different note; how do I list my equipment at the bottom of the post?

[Davey-T]

I find DSS produces very light images from the 60Da but look normal in P'Shop.

A lot of astro imaging is trial and error to find the best settings, at least you have a head start with dark skies

If you click on your user name you can edit your profile and signature.

Dave

[iksose7]

White balance maybe? It should be set to tungusten or some word along those lines! 

What time you image can make a big difference as well, or if the Moon is in the sky or getting ready to rise.

Callum

[astrodude]

Thanks Dave. I think you are right, it is more trial and error. I need a good run of clear dark skies. 

[astrodude]

Thanks for your input Callum. I do avoid imaging when there is a bright moon. White balance, I will try that. I have always used the auto setting, I was never sure what exactly to set it to. I will try tungsten next time. 

[frugal]

For reference, here is a single 900s frame just opened up in Photoshop, shrank to 20% of its original size and saved as a PNG:

You can see the histogram of the image aswell:

Looking closely at the histogram there is a tiny amount of white clipping, but only a very small amount. The final image looked like this:

[frugal]

Guernsey, west coast. So the skies are pretty dark. The only filter I use is a clear glass one to protect the camera chip. I am using a william optics FLT132 which is F/7. I try to image at about ISO 800 or 1600. It is just such a difference between a normal Canon DSLR and the DA. I can't help thinking I have a setting wrong.  

On a slightly different note; how do I list my equipment at the bottom of the post?

I always image at ISO 400. There are a load of articles out there showing that for DSLRs the ISO is just a gain multiplier added to the actual value stored on the CMOS (http://www.blackwaterskies.co.uk/2014/01/do-high-isos-make-dslrs-more-sensitive.html). The hard work by other people shows that in general ISO400 is the first ISO that has a multiplier >1.

All you are doing when you shot at ISO1600 is multiplying the recorded value by a fixed value, if that new value is greater than the maximum then it will get clipped at the maximum. So if we say for simplicity's sake that ISO200 has a gain of 0.5, ISO400 a gain of 1 and ISO1600 a gain of 4. Then if a pixel on the CMOS records a value of 200, the ISO200 shot will have a final value of 100, the ISO400 will be 200 and the ISO1600 800. If the maximum value that can be stored is 512, then the ISO1600 value will be clipped at 512 and you will have lost all of the extra information.

So we are both shooting at the same target, and I am using ISO400, and you are using ISO1600, I can probably have exposures 4 times as long as you can.

If you want to list your equipment, then you need to go to your settings and edit your signature.

[frugal]

Thanks for your input Callum. I do avoid imaging when there is a bright moon. White balance, I will try that. I have always used the auto setting, I was never sure what exactly to set it to. I will try tungsten next time. 

I think he is pulling your leg. You should always shoot astro-photography in RAW. In RAW the white balance is just a piece of information in the header, it does not actually change any information in the image, that is left to the image processing program which reads the white balance information and applies a tint to the image.

[astrodude]

Thanks for the example. I am going to have to experiment. Not having the facility to routinely guide I think I am used to short exposures on a less sensitive camera. The information about ISO numbers is interesting. I noticed from your picture you used ISO400. This I imagine is the real value of guiding, being able to use a lower ISO and a less grainy/noisy image.

I do always shoot in RAW and process these. I set the white balance by eye to something that looks pleasing more than anything else. The white balance might affect the preview of the image though when viewed on the camera or laptop software. I use Backyard EOS, I wonder if the downloaded image it shows is a jpeg conversion? mmm never considered that before. I will have to look at the manual.

[astrodude]

Just read the article in Blackwater Skies on ISO. It is very  good.But it has left me with one question though, in the RAW files is any ISO setting applied? While outside in the cold I have always relied on the preview image to judge my settings. If going above ISO 400 is just a case of multiplying the data, should I routinely image in ISO400 and adjust this post processing? The question is whether the multiplier is applied before recording the RAW image. 

[Davey-T]

Nice scope, I have WO110FLT and it's a super scope, the AZ EQ6 should be capable of over 5mins unguided if properly polar aligned.

I generally leave my 60Da on ISO400 unless there's a reason not to.

Dave

[wxsatuser]

I always use ISO 1600 and at a pinch 800......400 has produced banding in the past.

White balance is daylight but it's not critical for RAW.

Exposure should be somewhere between 20 to 40% of the histogram, tops 50%.

[iksose7]

I think he is pulling your leg. You should always shoot astro-photography in RAW. In RAW the white balance is just a piece of information in the header, it does not actually change any information in the image, that is left to the image processing program which reads the white balance information and applies a tint to the image.

Ha! I actually wasnt pulling his leg :/ i always set it to tungsten because thats what i always read in the tutorials when i started this hobby a few years back. Thanks for clearing that up though! Ya learn something new every day

Callum

[astrodude]

Yes the FLT is a lovely scope, it is my pride and joy. I still go back to the ZS66 though, it produces really bright wide angle images. I also have been able to get up to 5 minutes unguided, particularly on the ZS66, even stretched it to six minutes at a pinch if I do not stray too far from the CNP and put up with a small amount of elongation. It is all down to setting up the scope, polar aligning, PEC training and the target location. With the 60DA though I am thinking I should look at guiding next and imaging at ISO400. 

The issue of ISO is interesting. I have always gone for 1600/800. But I have always based this on what the preview looks like. I shall try both next time and compare the raw files. The 400 may not look so good, but perhaps if the information is still there it just needs faith and experience/skill in the post processing. I have imaged at 400 to get the bright centres of targets and have never noticed any banding at all. But that is on my 500D, I have only used my 60DA a couple of times so far and the increased brightness has thrown me.

Thank you for all your comments, it is really helpful.  

Jean

[Davey-T]

Glad your'e enjoying yourself I'm hankering after the new WO Star 71 to piggy back on top of the 110 for a wider field.

Dave

[astrodude]

Ha ha, Callum I like your alien on a tractor!

[iksose7]

Ha ha, Callum I like your alien on a tractor!

Thanks dude

Callum

[astrodude]

Dave,

I think the WO Star 71 will be a fantastic scope. I look forward to seeing some pictures from it when you get it!

[ollypenrice]

What the histogram needs is balanceing so that the top left hand side of the peak is the same distance from the right in each channel. You do this by moving the black point slider (lower left) to the right. I think that when you've done that the image will look a lot more normal. I don't know the 60Da but modded DSLRs generally give a very red image until the histo is balanced.

Olly

[Davey-T]

The issue of ISO is interesting. I have always gone for 1600/800. But I have always based this on what the preview looks like. I shall try both next time and compare the raw files. The 400 may not look so good, but perhaps if the information is still there it just needs faith and experience/skill in the post processing. I have imaged at 400 to get the bright centres of targets and have never noticed any banding at all. But that is on my 500D, I have only used my 60DA a couple of times so far and the increased brightness has thrown me.

Thank you for all your comments, it is really helpful.  

Jean

You can set the Live view simulation enabled / disabled,  Enabled tries to show the actual image, Disabled shows it at normal LCD brightness to make it easier to see.

Check to see which one you have it on if your going to use Live View to judge exposure.

Dave