1st attempt with the PST

Great image Al
I cant get an image out of the 350D at all!

Dave your gonna need to modify that 350d if you want to do HA imaging through it. The stock filter only passes about 10% of HA light. If this is something you fancy, Michael O'Connell will be popping over to modify his 350d soon. Why not make it a job lot!

Dave

It belongs to my other half and she's just seen this and the quote was something like "over my dead body!!!!!!!!!!"

BTW
Does anyone know where I can get a 300d 2nd hand then I'll do the mod. Is that the one involving removing the filter from the CMOS??


DaveG

Dave,

Hold fire for a bit. I understand canon are bringing out the successor to the 350d in the next couple of weeks. When that happens you'll see a flood of second hand 350d's on the market.

BTW if you ever fancy borrowing my modded 300d just to try it out and see how much better it is that would be no problem.

Saying that, I'm pretty sure you could pick up a 300d dirt cheap on ebay. The procedure on the 350d and the 300d is almost identical. I've experience at both of these having done my own 300d and both myself and Jed Glover modded his 350D. It really is a lot simpler and far less scary than people seem to think.

Hi,

More details on how you did it. Was it prime focus, afocal, e/p proj. Did u process the image seperately for proms and disc?????

BTW, how did you finally manage to get the camera to focus? Hope you didn't break anymore wrenches!

I'd better explain about the wrenches first

One of the first things I tried to do with the PST was to take images through it. But neither my toucam nor 350D could focus through it. So I asked Michael how he did it. It turns out that in order to get the webcam to focus you need to remove the eyepiece holder extension tube. olding the toucam in place with masking tape without an adaptor also works, just!

Eventually, after much struggling with wrenches I managed to get the eyepiece holder away from the main scope. Coronado had glued the thing in place. Next I just had to separate the eyepice extension tube. No joy with any wrenches I had so I got a pair of 'baby boa' strap wrenches to do the job. The strap on this wrench according to their website "is reinforced with 33 industrial quality fibre strands it is strong enough to pull a small car". However Coronado had glued the extension in place with glue that could stick a ford fiesta to the ground, and the strap wrench snapped while trying to separate the bits. It turns out that coronado have changed the design of the eyepiece holder slightly and I have a filter in a different place than Michael does, mine also clearly is held together with a stronger glue. At this point I raised a white flag to coronado and put the scope back together again and opted for plan B.

Michael had pointed out an accessory that included a 20mm Kelner, and a way to connect that to a T-ring. I already had an attachment for connecting an eyepiece to a tring so I just reied that, my PST came with a 20mm Kelner. Still no joy - I could not get focus. After asking around it seemd that getting a 40mm T-ring extension tube would do the job. Which arrived from telescope service the other day. Still couldn't focus! I had to move the eyepiece out about 5mm to get the image to focus, so I'll just change the barrel on the eyepiece.

Finally I was able to get an image in focus. For the shot above I just guessed the focus from looking through the viewfnder. It fills the 350D frame quite nicley as you can see below.


Full resolution: static.flickr.com/73/205292844_a3b9101450_o.jpg flickr doesnt let you upload raws.

As for processing I took what is probably the simplest approach.

1. Split the image into RGB components.
2. Tweak the green until you can get the surface detail
3. Tweak the red to get prominance detail.
4. Copy disk image onto prominance image.
5. Colour to taste.

Things I can think of to improve this offhand are:
1. Focus properly!
2. Experiment to see which exposures work best from proms and which for surface details.
3. Use a difference layer to merge the green and red images rather than cut and paste.

As for the camera I dont think any modification is needed for Solar HA work. For deepsky it would be. You'll have noticed that I mentioned using the green channel for surface detail. Obviously there is no green in a HA image! Whats happening is that the red cells are saturated and bleeding slightly into the adjacent green cells. This sounds a very bad way to image but there are twice as many green cells on an RGB chip as there are red. The layout is RGBGRGBG rather than RGBRGB as you might expect. So by using the green channel you are getting twice as much data as the red channel. From what I've read using the spilled over green chanel gets more useable data than using a properly exposed red image.

So why don't you need to mod the camera to take the filter out? Well even if it is blocking 90% of the light, enough is getting through to fill the red cells to overflowing.

Why might you do the mod? Two reasons that I can think of. 1. You could do shorter exposure times. I think 1/8s is fine with a good tripod and shutter release. 2. Newtons rings. They were a cool oddity in physics class but annoyingly show up in the viewfinder of the camera, though I didn't notice them while processing the image. I've read that this is caused by the filter in the camera, and so removing the filter _may_ remove the problem. But like I say, I didnt spot this issue in the images.

Hope that answers peoples queries! I can post pics of my eyepiece and adaptor steup if anyone wants.

Cheers,
~Al

Hey Albert,

Where did you manage to pickup the Boas? I've just searched all over Galway for one - none of the tool houses even heard of them!
I can't believe how strong the glue they use is! The extension came off easily with my previous PST, but this is something else altogether.
This new version of the PST makes it impossible to get to prime without a barlow

By the way, has anyone found out what that new in the extension tube is? It doesn't seem to be a blocking filter as it is easy quite easy to focus on terrestrial objects through it.

Thanks,

Trev

Hey Albert,

Where did you manage to pickup the Boas? I've just searched all over Galway for one - none of the tool houses even heard of them!
I can't believe how strong the glue they use is! The extension came off easily with my previous PST, but this is something else altogether..

Some place online, I'll see if I can find the reciept... I saw them in B&Q not long ago though. try asking for a strap wrench or a chain wrench.

I got the eyepiece holder off eventually, but splitting off the extension tube was impossible. Since it has some filtering components I just gave up on it.

I never really got the hang of imaging with the PST, I might invest in a celestron neximage at some point. Others have had success with them. My toucam has passed on... I dont even bother using the DSLR with it too much as I find the focussing very hard to get right. I dont know how Michael manages it!