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Old 27-10-2011, 06:55 AM
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hotspur (Chris)
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This would be 'amp glow'?

Hello.

I am going to be using my Canon 450D for astrophotography.I have a external power supply that is custom made for it,currently under construction.

I have some strange artifacts of light along top of images,we figured the red/pink splodge is amp glow,is this correct??,and a strange 'greenish' light
along top to left of pink-this I am told is caused by light coming through view finder,and can be stopped by covering it.Might be a bit hard to see here,but its a strip of light along top when dark frame subtract done,it comes up as jet black.

With the new external power supply,this would eliminate amp glow??attached is a four minute sub for examination.

Thanks Chris
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Old 27-10-2011, 07:00 AM
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h0ughy (David)
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do a 4 min dark. no the power supply wont remove the amp glow and you do have to cover the view finder with something to block all light
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Old 27-10-2011, 08:16 AM
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hotspur (Chris)
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re amp glow

I have noticed it on the darks as well,HOughy.

Here is a image that is a stack of subs and darks (four minutes each).I have manipulated the image to show the artifacts along top.I am told the long 'dark ridge' is from the light going through the view finder,but still not sure what the 'pink' is-is it amp glow?? or caused from something else that needs to be addressed.

Assuming the 'long dark' ridge' was caused by light coming through the view finder-that can be solved fairly simply.The 'pink' is much less noticeable after the darks have been added in DDS.Are there any other thoughts on this 'pink' splodge and how it can be eliminated??

I have non of these things when using 50D.

Thanks for any suggestions-Chris
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Old 27-10-2011, 08:34 AM
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The camera should have come with a strap. On the strap is a little cover designed to clip on the viewfinder. When I used my 40D for imageing in the past I always left this little cover in place. Stops the light problem.
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Old 27-10-2011, 09:55 AM
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hotspur (Chris)
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re viewfinder cover

Yes,Terry-I seem to have lost my neck strap -(I never use one-prefer hand strap).

But I found this on ebay

http://www.ebay.com.au/itm/230475533...84.m1423.l2649

for only a couple of dollars with postage,I can take the cup off and black out the gap for view finder and slide on and off as required.
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Old 27-10-2011, 10:07 AM
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As Houghy said - look at a dark taken with the camera off the scope, front cap on and viewfinder covered, with the camera in a dark box and what you will see is the amp glow.

The external power supply doesn't get rid of amp glow - the heat of the amp is there regardless of how the camera is powered and that heat is "seen" on the sensor as these pink splodges.

What you do avoid by using the external power supply is the heat that is generated as a LiPo battery discharges causing a similar heating of the sensor.

Certainly impressed with your cluster image - the autoguiding seems to be working brilliantly!

DT
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Old 27-10-2011, 10:07 AM
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I get the same pink blob and it's not on every pic - it may be from the LCD display - wind the display down to minimum if you need to see it - and it may be eliminated
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Old 27-10-2011, 11:05 AM
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re amp

Thanks David and Jen.

Yes will do that test David.Jen you mention 'wind the display down to minimum'
what is that? not familiar with that,I'll read the manual.

The second image I have posted here,the pink splodge is fairly minimal,and I could crop image.The 'dark ridge' was more of a concern-but general opinion is that it is light coming through view finder,which can be fixed.

Thanks David-yes the cluster come out well,did a few images of it,all the same.
Not sure why the guiding started to get better-may be the defocusing of the guide star helped a fair bit.

I hope I've made the right decision here choosing the 450D, I did notice the balance of gear seemed better with it rather than 50D,and the guided images much better.Hop these artifact issues can be solved.


The other reason I chose this camera,is its less valuable than 50D,and I see astrophotography as a secondary interest from now on.

Cheers Chris
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Old 27-10-2011, 11:30 AM
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Quote:
Originally Posted by hotspur View Post
Yes,Terry-I seem to have lost my neck strap -(I never use one-prefer hand strap).

But I found this on ebay

http://www.ebay.com.au/itm/230475533...84.m1423.l2649

for only a couple of dollars with postage,I can take the cup off and black out the gap for view finder and slide on and off as required.
At that price it is a good experiment.
Do you use a red headlight? The intermittent pink splodge can come from looking at the camera during expsures with the headlight.
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Old 27-10-2011, 12:05 PM
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hotspur (Chris)
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yes,Terry-its certainly a cheap item,I am now thinking-leave the cup on that item and simply have some material to go over the cup and attach with a rubber band-if I have to look through the viewfinder-this arrangement an easily be taken off and on as needed.

Still not sure what this 'pink light' is.But should be able to minimize its affect.
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Old 27-10-2011, 12:36 PM
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Hi Chris,

It looks like ampglow to me, however people in this older thread say that the 450D should not produce any noticeable amp glow in a 4 minutes sub like that...
I'd be interested to know how you get on!

Cheers,
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Old 27-10-2011, 01:35 PM
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Quote:
Originally Posted by irwjager View Post
Hi Chris,

It looks like ampglow to me, however people in this older thread say that the 450D should not produce any noticeable amp glow in a 4 minutes sub like that...
I'd be interested to know how you get on!

Cheers,
Hi there Ivo.

I'd like to know what it is too!

I did the test David Trappet mentioned,in that I put camera in box covered view finder,lens cap on.covered the box.So it was in compete darkness.

The result was exactly the same-pink up towards to corner and green along top.Is there anyway to eliminate the effects of this in any PP??

I may have to look at buying a second hand 400D,or try another 450D one day.Certainly a lot of headaches in astrophotography!!!
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Old 27-10-2011, 02:27 PM
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Well, I don;t get it on every pic so I'm not sure how it happens
I can take a run of say 10 4 min shots and the first and 4th may have the marks on them
sometimes a dark as well - when the dark is subtracted I get an intense black in that area with a red changeover line above where the green was - the pink blob seems togo intense balck too
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Old 27-10-2011, 04:04 PM
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yes-that is it Jen-but I get it all the time!!

My thoughts are-seeing this issue is unfixable.I'll use the 450D on the scope and just crop the affected area off,and use the 50D with 10-22 mm lens for wide field.I'll have to purchase or get built a external power supply for the 50D.
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Old 27-10-2011, 05:53 PM
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All of these problems can be taken care of by properly and carefully calibrating your light frames.

Take a large number of darks, say, 16-25, and the same in flat lights/darks.

The problem will be resolved.

H
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Old 30-10-2011, 08:44 AM
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Quote:
Originally Posted by Octane View Post
All of these problems can be taken care of by properly and carefully calibrating your light frames.

Take a large number of darks, say, 16-25, and the same in flat lights/darks.

The problem will be resolved.

H
Ok,I have contacted the gentleman that makes light boxes.When you mention 'flat light/darks' are these different darks that you take with camera on scope with cape on? When you do light frames-do take these just after you have taken your subs? Or can they be done the day after?

Thanks Chris
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Old 30-10-2011, 10:35 AM
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http://www.iceinspace.com.au/forum/s...ad.php?t=82149
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