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Old 04-03-2010, 07:53 AM
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iceman (Mike)
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PST with a DSLR or DMK

Hi guys

I'm thinking about getting a solar scope, and have been reading about PST's and finding that there is difficulty getting a DSLR or webcam to focus (not enough back focus).

Most of those threads were from 2005/2006, so I just want to ask:

1. Is it still a problem?
2. What are the potential solutions to use a DSLR and/or a DMK for solar imaging with a PST?

I'd much prefer to get a full-disc image with a DSLR rather than have to do mosaics.

Cheers
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  #2  
Old 04-03-2010, 08:12 AM
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[1ponders] (Paul)
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I've used the DMK, Mike and found I had to grind the shoulder on my 1.25 adapter off to get the camera close enough to achieve focus. From memory the only way I could do it otherwise (and i can't remember if i tried this with the canon) was to use a barlow.

Using the canon (and you may need a modded one with increased Ha sensitivity) you are only getting to use 1 in 4 pixels, though there may be some bleed across wells.

go here http://astro-nut.com and download the Solar Primer PDF. You will find all you need in there including processing and false colour images
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Old 04-03-2010, 08:16 AM
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Quote:
Originally Posted by [1ponders] View Post
I've used the DMK, Mike and found I had to grind the shoulder on my 1.25 adapter off to get the camera close enough to achieve focus. From memory the only way I could do it otherwise (and i can't remember if i tried this with the canon) was to use a barlow.
hmm thanks, that should be ok. I'm happy to grind down the adapter.

Quote:
Using the canon (and you may need a modded one with increased Ha sensitivity) you are only getting to use 1 in 4 pixels, though there may be some bleed across wells.
I have a modded 40D now, so will that work ok? How will it attach to the PST?

Quote:
go here http://astro-nut.com and download the Solar Primer PDF. You will find all you need in there including processing and false colour images
Thanks - will have a look!
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Old 04-03-2010, 08:19 AM
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[1ponders] (Paul)
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to attach it to the PST you will need a T - 1.25" adapter to screw into your T ring of your camera. I really don't see how you will get the chip close enough to be able to achieve focus though. If i had some sun today I'd test it out today for you
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Old 04-03-2010, 08:28 AM
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[1ponders] (Paul)
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http://www.astro-nut.com/sun-pst.html
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Old 04-03-2010, 08:31 AM
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Yeh I read that today, but it just talks about a ToUcam - not a DSLR.
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Old 04-03-2010, 08:32 AM
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Originally Posted by [1ponders] View Post
to attach it to the PST you will need a T - 1.25" adapter to screw into your T ring of your camera. I really don't see how you will get the chip close enough to be able to achieve focus though. If i had some sun today I'd test it out today for you
Cool, would appreciate that whenever you get the chance.

It sounds like it may not be possible though.
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Old 04-03-2010, 08:39 AM
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Part 1 and 2 of this gives a bit more info using a DSLR
http://www.astro-nut.com/ir-mod.html
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Old 04-03-2010, 08:41 AM
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I'd like to get the chance too. Would you like to borrow our rain for awhile?
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Old 04-03-2010, 08:54 AM
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Hi Mike,

I have explained a number of ways to get a DSLR to work on my DOB with great success in getting the CMOS element closer the mirrors, I am wondering how many other scopes have the same features.

Check if the 1.25" barrel can be unsed, if yes then find out what the thread is see if there is a Thread converter to "T". I was lucky to find the Skywatcher already had a T Thread on the outside giving me the extra inch closer to the mirrors.

I think the Barlow would work a treat though as it worked well on my DOB.
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Old 04-03-2010, 08:59 AM
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A DMK 41 does the job beautifully, Mike!

Al.
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Old 04-03-2010, 11:32 AM
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A DMK 41 does the job beautifully, Mike!

Al.
How much of the disc do you get in the FOV?
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Old 04-03-2010, 11:55 AM
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How much of the disc do you get in the FOV?
all
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Old 04-03-2010, 12:09 PM
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all
Sweet!
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Old 04-03-2010, 12:21 PM
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Yep! Matt wastell has the DMK31 and just misses out on the full disc, but my 41 does the job with room to spare. ...and you can stack frames to compensate for seeing... which is not as convenient on the dslr.

Al.
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Old 04-03-2010, 12:27 PM
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True dat - except that you can't print it nice and big, like you can with a DSLR
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Old 04-03-2010, 12:32 PM
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well Mike go and get your self the new Canon 550D - 18mp full HD video as well as the stills
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Old 04-03-2010, 01:36 PM
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True dat - except that you can't print it nice and big, like you can with a DSLR
Hmmm... with the resolution you'll get at 40mm aperture you might not want to print it too big either...

What you need is an SM90 scope and the 550D!

Al.
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Old 04-03-2010, 10:30 PM
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Aside from the focus issues the PST EP adapter is not geared for holding a DSLR of that weight. The screw is made of plastic. I tried using my DSLR on my solar Max and found it took terrible images that were red and resolved very little and slipped due to the screw fixing. With a Solarmax 90 you need the straight through version so the blocking filter is located in the scope and not in the diag. The best advice is use a DMK41, or perhaps get a monochrome large format camera and try that. The imaging circle of the PST is quite small too with the blocking filter it employs. It will seriously vignette your DSLR images too.

For my money I would use the larger DMK, and is in fact my next camera purchase for doing whole sun portraits.
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Old 15-03-2010, 06:11 AM
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iceman (Mike)
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Quote:
Originally Posted by [1ponders] View Post
I've used the DMK, Mike and found I had to grind the shoulder on my 1.25 adapter off to get the camera close enough to achieve focus. From memory the only way I could do it otherwise (and i can't remember if i tried this with the canon) was to use a barlow.
Hi Paul

Can you elaborate on this a bit more?

Did you literally just use a hacksaw to cut the 1.25" nosepiece in half, or is it something else?

How much did you take off?

How does the PST actually focus? Does it move the internal element or something? Because the eyepiece doesn't appear to move when I use the focus knob.

Cheers
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