PST with a DSLR or DMK

[iceman]

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

[[1ponders]]

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

[iceman]

hmm thanks, that should be ok. I'm happy to grind down the adapter.


I have a modded 40D now, so will that work ok? How will it attach to the PST?


Thanks - will have a look!

[[1ponders]]

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

[[1ponders]]

http://www.astro-nut.com/sun-pst.html

[iceman]

Yeh I read that today, but it just talks about a ToUcam - not a DSLR.

[iceman]

Cool, would appreciate that whenever you get the chance.

It sounds like it may not be possible though.

[[1ponders]]

Part 1 and 2 of this gives a bit more info using a DSLR
http://www.astro-nut.com/ir-mod.html

[[1ponders]]

:lol: I'd like to get the chance too. :) Would you like to borrow our rain for awhile?

[mswhin63]

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.

[sheeny]

A DMK 41 does the job beautifully, Mike!:P

Al.

[iceman]

How much of the disc do you get in the FOV?

[h0ughy]

all

[iceman]

Sweet!

[sheeny]

Yep!:thumbsup: 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.

[iceman]

True dat - except that you can't print it nice and big, like you can with a DSLR :)

[h0ughy]

well Mike go and get your self the new Canon 550D - 18mp full HD video as well as the stills;)

[sheeny]

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!:D:P

Al.

[Paul Haese]

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.

[iceman]

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

[[1ponders]]

If you have a look at the image I posted you will see that the nose piece has been ground down at the shoulder near the camera body. I used a dremel to remove the shoulder. That meant I could get the DMK about 3 or 4 mm closer to the pst. The whole adapter new fits right into the PST no with the camera sitting on hard on top of the Eyepiece holder of the pst. I have np getting focus now

[iceman]

ah ok I understand now.

Thanks I'll give that a try.

[sheeny]

Yeah I did the same mod to my nosepiece under Paul's expert remote guidance and encouragement.:) I used a bench grinder though. I found I also had to shorten the nosepiece as well. I think it measured something like 6-7mm longer than Paul's and stopped the camera getting as close as I needed it. If you do have to shorten the nosepiece, use an old piece of hacksaw blade to clean out the thread after you've ground it.:thumbsup:

Al.