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Old 19-12-2008, 12:19 AM
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Tandum (Robin)
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HA Imaging with a modified DSLR.

Sorry, I know I've started this thread before, but the last one spun off to something about modified DSLR cameras.

I have a modified DSLR camera and taking HA images without the mod is difficult if not impossible.

I got myself a HA filter and can't get myself a decent image. It appears I received a 7nm filter instead of the 13nm Filter I thought I ordered. I know there was total confusion on the sellers website when I ordered as the listed 2" price was really the 1.25" price and it went on and on from there. But I digress. I got the 2" badder filter in the end.

Even though it's been so overcast and stormy I've managed to use it twice, and I have spend dusk till dawn on both occasions trying every combo going to get a detailed image and I've failed badly.

AlexN is posting me his 13mn filter for a try out. Time will tell there.

Is a 7nm HA filter too narrow for a modified DSLR ?

Here are a couple of images that gained a result. HHead was 20 minute subs @ 1600, M42 was 15minutes @ 800. All other attempts are crap. Notice how huge the numbers are .. 20minutes @ 1600 ..... and I ran them through neat image first.

Is anyone else doing narrowband on a DSLR?
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Last edited by Tandum; 19-12-2008 at 01:04 AM.
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  #2  
Old 19-12-2008, 04:24 AM
gbeal
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Robin,
I don't think the 7Nm is too narrow, I use one. Yes the 13Nm will be "easier" to use but in some respects the effect will be lost.
Try it, but be aware the Ha in a OSC chip will require looooooooong exposure.
I use 15 minutes on a regular basis, and often 20 to 30 minutes.
Mine is not too different to a modded DSLR, it is a QHY8, so it only the cooling that differs. Attached is the current work in progress. Only about an hour and a half so far. More, much more, to go. Poor weather doesn't help.
Gary
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Old 19-12-2008, 07:53 PM
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seeker372011 (Narayan)
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I have used both a 13nm Astronomik and a 7 nm Baader with my Canon 300D modded

not a problem

need longer exposures and focusing was a bit of a challenge hard but a Bahtinov mask has just simplified focusing enormously
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Old 21-12-2008, 07:53 PM
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Tandum (Robin)
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Cheers guys, Looks like I need more time to screw around with it. I have a mask for focus but framing can be a challenge when a 5minute sub shows no image. I should have the pier in by the new year which will make polar even more stable and then we'll see how much noise comes out of a 30minute sub on a 40D
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Old 21-12-2008, 10:20 PM
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something wrong if you cant see something in 4 to 8 seconds-you must be mega out of focus

I have found that using a bahtinov mask on a very bright star-eg Sirius works

need only 4 secs at ISo 800 to get an image..you should see an image in 5 min for sure
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Old 21-12-2008, 10:41 PM
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Tandum (Robin)
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I can focus with my mask on a star just fine, it's framing shots that are a problem. Here's an example. Image.jpg is 3x20minutesubs@1600 which is pretty much what I see during a framing shot. 2244.jpg is image.jpg stretched in PS with green/blue removed and that's what I'm used to seeing in a short framing shot. It's simply taking a lifetime to get photons onto the sensor. To compare, I added a single frame shot of helix I shot a couple of months back. It's obviously there.
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Last edited by Tandum; 21-12-2008 at 11:13 PM.
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