200p DSLR focus

[bottletopburly]

Just follow Anthony’s advice that all you need no more expense the stock 1.25 eyepiece holder unscrews as it is made from two parts you need bottom piece as in Anthony’s piccy screw that into t-ring attach to camera insert into focus tube , tighten and good to go 👍

[miguel87]

50 minutes ago, david_taurus83 said:

I'll take your word for it as it's your scope! I had the old blue tube and I had to fit a low profile focuser for my 600D.

 

There is a whole host of people online modifying their 200p just so a dslr will reach focus.

[Anthony1979]

13 minutes ago, miguel87 said:

So all these camera t rings are a standard 2 inch thread?

Thus should go straight onto my focusser?

Why do people have issues with focussing a 200p and dslr then?

Yes i use both canon and nikon both rings are different but the threads are the same

[david_taurus83]

2 minutes ago, miguel87 said:

There is a whole host of people online modifying their 200p just so a dslr will reach focus.

The stock focuser left very little room for inward focus. So some people modify the tube by moving the mirror up so the focal plane reaches the camera sensor. Others, like myself, fitted a lower focuser. I've never used the PDS focuser like you have so I cant comment on it.

I think the reason your not getting the answer on the barlow question is because it's not really 'the done thing' . By increasing the focal length to 2000mm you are really going to struggle to frame and image anything. Even 1m is quite demanding. But of course, it's entirely your choice what you do with your own kit and fair play if you can get some nice pictures. People commenting saying try the t adapter are only trying to help and make things easier for you.

[miguel87]

Ok great,

Thanks for all the replies, shame the sky isnt looking good enough to try it out.

Will post an image on here if it works.

👍

[miguel87]

2 minutes ago, david_taurus83 said:

The stock focuser left very little room for inward focus. So some people modify the tube by moving the mirror up so the focal plane reaches the camera sensor. Others, like myself, fitted a lower focuser. I've never used the PDS focuser like you have so I cant comment on it.

I think the reason your not getting the answer on the barlow question is because it's not really 'the done thing' . By increasing the focal length to 2000mm you are really going to struggle to frame and image anything. Even 1m is quite demanding. But of course, it's entirely your choice what you do with your own kit and fair play if you can get some nice pictures. People commenting saying try the t adapter are only trying to help and make things easier for you.

Thanks, good info.

I have taken nice pictures with the barlow in place because even tho it is a 2x barlow I dont think it is working at 2x. The spacing from barlow glass to camera sensor is probably different to a normal eyepiece so it would be difficult to work out exactly how much the barlow is affecting the magnification.

This picture is using the barlow lens and dslr...

[alacant]

39 minutes ago, miguel87 said:

Why would I buy something I dont have instead of using a barlow that I do have?

Unless you simply want to photograph the moon and bright planets, imaging at 1000mm focal length is challenging enough as it is. Using a Barlow will not only make the task more tricky, the results you obtain are unlikely to be anywhere near those which you would obtain with the correct adaptor.

Cheers

[CraigT82]

3 minutes ago, miguel87 said:

Thanks, good info.

I have taken nice pictures with the barlow in place because even tho it is a 2x barlow I dont think it is working at 2x. The spacing from barlow glass to camera sensor is probably different to a normal eyepiece so it would be difficult to work out exactly how much the barlow is affecting the magnification.

This picture is using the barlow lens and dslr...

You can work out your focal length...  all you need to know is the angular size of the object in the image (moon), how many pixels across it occupies in the image (use photoshop or gimp) and what you pixel size is. 

[miguel87]

4 minutes ago, alacant said:

Unless you simply want to photograph the moon and bright planets, imaging at 1000mm focal length is challenging enough as it is. Using a Barlow will not only make the task more tricky, the results you obtain are unlikely to be anywhere near those which you would obtain with the correct adaptor.

Cheers

Ok thanks well these are the things I didnt know. I didnt know that I didnt have the correct adaptor. I will try it at 'prime focus' next time.

 

Edited April 22, 2020 by miguel87

[miguel87]

3 minutes ago, CraigT82 said:

You can work out your focal length...  all you need to know is the angular size of the object in the image (moon), how many pixels across it occupies in the image (use photoshop or gimp) and what you pixel size is. 

Angular size in the image is not possible to calculate? Depends how close I hold the picture to my face.

Oh sorry you mean the actual moon not my picture

Edited April 22, 2020 by miguel87

[8324689]

I chopped my 200p to focus! 

 

I took off 5 cm - in retrospect I would have taken off 2.5 cm

Edited April 22, 2020 by 8324689

[miguel87]

6 minutes ago, 8324689 said:

I chopped my 200p to focus! 

 

I took off 5 cm - in retrospect I would have taken off 2.5 cm

That's what I thought and have read previously.

I am now lead to believe I dont need to chop or use a barlow and I can just use prime focus at the empty focusser?

Have you tried this?

[8324689]

I didn't try it maybe take off the focus and see where you would you focus with a DSLR. you can get it modified and shim the sensor closer.  

 

canon DSLR have a mark with the sensor lies see where that gets in focus to see what your options are. Low-profile focus cost £160 is it worth it? 

 

Get a friend to help and see with a measuring tape where you gain focus. 

Then decide what option you will go with as there are many

Edited April 22, 2020 by 8324689

[8324689]

I'm guessing you have a blue 200p?

 

What the people before me are suggesting may well work you just need to get down really low

[Viktiste]

I did not have to cut my 200P to achieve focus with a Canon550D. Mounted like this:

[8324689]

13 minutes ago, Viktiste said:

I did not have to cut my 200P to achieve focus with a Canon550D. Mounted like this:

My 550d worked but not 450d

[miguel87]

12 minutes ago, Viktiste said:

I did not have to cut my 200P to achieve focus with a Canon550D. Mounted like this:

Brill thanks. I have the black 200p too. The only difference in our setup would be the two speed focusser (depth looks pretty similar) and my camera is an entry level pentax but I dont know how much difference that would make.

Out of interest and planning my test run, what sort of FOV do you get with that set up?

[DaveL59]

if you do find you need to adjust the scope, rather than cutting the OTA you might achieve the same effect cheaply by replacing the collimation and lock screws with longer ones and also springs to suit the extra length. That'd move the mirror cell up the tube to shift the focal plane and also be easy to return to factory later if you wanted to sell it on. I did this on my TAL-1 when adapting it to use standard 1.25-in eyepieces, am sure it'd work on your SW200 also.

You may find that you'll need an extension tube to use it for visual once done though depending on the amount of back-travel there is in the focuser.

[miguel87]

4 minutes ago, DaveL59 said:

if you do find you need to adjust the scope, rather than cutting the OTA you might achieve the same effect cheaply by replacing the collimation and lock screws with longer ones and also springs to suit the extra length. That'd move the mirror cell up the tube to shift the focal plane and also be easy to return to factory later if you wanted to sell it on. I did this on my TAL-1 when adapting it to use standard 1.25-in eyepieces, am sure it'd work on your SW200 also.

You may find that you'll need an extension tube to use it for visual once done though depending on the amount of back-travel there is in the focuser.

No the 200p needs the opposite of an extension tube, that's why some people cut them or get low-profile focusses.

I like the idea with the mirror but I hope it doesnt come to that. It would also mean the secondary wouldnt see all of the primary so some aperture would be lost.

Thanks.

[DaveL59]

I meant for visual use if you move the mirror, you'd need an extension to bring the eyepiece back away from the secondary to hit focus  Moving the mirror up the tube brings the focal point up the focuser tube to compensate for lack of in-focus travel, but doing this for a camera has the potential drawback of rendering the scope not usable for visual, hence an extension for the eyepieces.

Moving the mirror by say 25mm isn't going to lose you much aperture so I'd not worry about that too much, 6 bolts and 3 springs for around £10 vs how much for a low-profile focuser...? Your call tho  

Edited April 22, 2020 by DaveL59

[Viktiste]

The EOS 55D has close to the same "flange backfocus" as you Pentax K-r. So I am guessing you will achieve focus, but there is only about 1 cm left to move the focuser in. Bear in mind I have the stock focuser, I don't know the details of your focuser.

To find your field of view google your cameras pixel size and resolution and plug that and the 200P details in here: http://astronomy.tools/calculators/field_of_view/

[miguel87]

4 minutes ago, DaveL59 said:

I meant for visual use if you move the mirror, you'd need an extension to bring the eyepiece back away from the secondary to hit focus  Moving the mirror up the tube brings the focal point up the focuser tube to compensate for lack of in-focus travel, but doing this for a camera has the potential drawback of rendering the scope not usable for visual, hence an extension for the eyepieces.

Moving the mirror by say 25mm isn't going to lose you much aperture so I'd not worry about that too much, 6 bolts and 3 springs for around £10 vs how much for a low-profile focuser...? Your call tho  

My call is neither! Honestly I wouldnt dream of changing mirror screws or anything like that. If it came to that I just wouldnt bother with AP. All I want to know is what is the best I can do with what I have already and it might be fun to take some photos. For me, visual is king.

I just thought, hold on, I have a telescope, I have a half decent driven mount, a DSLR and a T-ring adapter, why havent I at least tried to take some photographs other than the moon

I'm feeling positive that the dimensions of my DSLR are pretty normal and I should be able to reach prime focus. If I cant, I will just stop there!

[Anthony1979]

43 minutes ago, 8324689 said:

My 550d worked but not 450d

My 450d works on my 150

[Anthony1979]

47 minutes ago, miguel87 said:

Brill thanks. I have the black 200p too. The only difference in our setup would be the two speed focusser (depth looks pretty similar) and my camera is an entry level pentax but I dont know how much difference that would make.

Out of interest and planning my test run, what sort of FOV do you get with that set up?

This is about the same distance mine comes out

[miguel87]

17 minutes ago, Viktiste said:

The EOS 55D has close to the same "flange backfocus" as you Pentax K-r. So I am guessing you will achieve focus, but there is only about 1 cm left to move the focuser in. Bear in mind I have the stock focuser, I don't know the details of your focuser.

To find your field of view google your cameras pixel size and resolution and plug that and the 200P details in here: http://astronomy.tools/calculators/field_of_view/

I punched in the numbers (I think) and it seems a pretty good area, very similar to my 32mm eyepiece.