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Old 28-03-2015, 01:27 PM
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Stonius (Markus)
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Silly Question

Hi everyone,

Just starting out and I have a silly question. I know from my other photographic efforts that dust on the sensor is a no-no. Thats why DSLRs have self cleaning sensors.

But when photographing at prime focus or through a mount, the camera body is just open to the elements. Do people have issues with dust getting into the camera body?

Secondly, I have recently gotten one of the mounts that allows a DSLR to shoot through the eyepiece, using the eyepiece to focus the image onto the sensor as a lens would. Here again, the sensor is perhaps even more exposed to the elements, but it also concerns me that without any kind of shielding from light, it's possible that you could get fogging or reflections from incidental light entering the camera between the eyepiece and the camera (say from a careless flick of a torch or perhaps, even a streetlight, where I am).

Or maybe I'm just using the mount wrong or need an extra bit of gear? Some sort of flange to close the gap between the camera body and the eyepiece?

I'm mostly looking at planetary objects, as I live in the city.

Although, I did experiment with prime focus the other day, just for the hell of it, to see what would happen and was very suprised to be able to pull a shot of Eta Carinae, which I have attached. Now, I have to say, I'm completely in awe of some of the amazing pics that have been posted here by you guys, and I know mine is very noisy and unspectacular by normal standards, but I can't help feeling a little stoked considering it's;

a) my first attempt
b) I still dont know the ins and outs of atrophotography software. I didnt even know I was supposed to take dark frames, light frames, etc.
c) It was taken on a bog- standard 8" Dob. No tracking
d) It was taken about 50m from Punt Road in Central Melbourne

Considering all of the above, I wouldn't have thought an image like this was even possible. So thank you patron saint of Astromony, whoever you are. Would that be Carl Sagan? :-)

However, I'm also unsure of whether that dim nebulosity is actually an internal reflection of a streetlight creeping into the top of the tube. There are supposed to be dark dust lanes there. Hmmm.

I know I have completely the wrong gear for this sort of thing, but I think I might just keep playing to see what's possible :-)

-Markus
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  #2  
Old 28-03-2015, 11:25 PM
raymo
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Hi Markus, Dust on the sensor is only a very occasional problem when using prime focus, [ I personally have never had it happen], provided that when the camera has no lens fitted, it is laid down face down.
If the mount you refer to for utilising the scope's eyepiece is a bracket that allows you to put the camera up close to the eyepiece, [afocal
method], you focus the eyepiece first, put the camera with it's lens fitted
up to the eyepiece, and finally focus the camera.
The other kind of adaptor allows you to put your eyepiece of choice into
it and attach it to the camera with a T-ring.[ eyepiece projection method].
At the very beginning don't bother with separate darks, flats, etc: just
enable the camera's noise reduction features, and it will take a dark after each exposure is completed. The colours in your image are strange, but
that is for later. Eta Carina does have a large area of nebulosity around it.
raymo
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Old 29-03-2015, 12:52 AM
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Stonius (Markus)
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Thanks Raymo! :-)
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