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dawson

Small image

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dawson

Jupiter, when visible, is quite small on my laptop when i use my webcam directly onto the telescope.

To get a larger image, which would result in a crisper image, using a 2x Barlow (i've only got the standard one which came with the scope (skywatcher 127 mak-cassegrain)) or going 2x with the software and zooming in with the web cam?

Thanks

James

Edited by dawson

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dawson

Whats the difference between a barlow and a powermate? I'm going to look on google too.

James

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Brantuk

A lens will always give a crisper image than electronic enlargement in my experience (subject to atmospheric conditions at the time of course). :)


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dawson

I'd love a bigger one.

I'll play with the Barlow option first. Last time i tried the Barlow i just couldn't find Jupiter again; will adding the Barlow alter the focus much?

James

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Brantuk

You will have to refocus after adding the barlow because effectively you are changing the focal length of the scope (doubling it). This increases the magnification you are using - and also reduces the field of view. That's why the object that you previously found without the barlow suddenly disappears out of the eyepiece.


 


The problem is accurate finding - which depends on the finder magnification, fov, and getting it accurately centered and aligned in harmony with the main tube. To put it simply - align the finder and the scope with the highest possible magnification you can for the greatest accuracy.


 


Eg. If want to image at around 200x magnification with your scope (which has fl-1500mm) then do the finder alignment with an 8mm eyepiece in the scope (gives 187.5x mag) or use a barlow and a 16mm eyepiece.


 


It is reckoned that a webcam is roughly equivalent to using a 6mm eyepiece - if you barlow it then it becomes roughly 3mm yielding 500x mag (ambitious in your scope). If you just use webcam only you'd get 250x mag (which is about enough in UK average seeing). And also with your scope the max practical magnification quoted is 254x - so you're working on the limit really - you'd need an exceptionaly clear night.


 


Pop your scope and camera details in here to get a good idea of what the webcam sees : http://www.12dstring.me.uk/fov.htm


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Graham

A 2x Powermate will give a crisper image :) there's one on ABS. That's what I use-I sometimes wonder though whether I would get away with using a 4 x Powermate with my scope for an even bigger image??

http://www.astrobuysell.com/uk/propview.php?view=66732

 

Felix I have used a 5x barlow on Jup with my 200 Newt and the spc.

This is the result.

 

 

Edited by Graham

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Graham

A 2x Powermate will give a crisper image :) there's one on ABS. That's what I use-I sometimes wonder though whether I would get away with using a 4 x Powermate with my scope for an even bigger image??

http://www.astrobuysell.com/uk/propview.php?view=66732

 

Felix - I have used a 5x Barlow with my 200 Newt and the SPC.

Edited by Graham

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catman161

Nice one graham-good images, how did you get it to focus properly with a 5 x Barlow on?

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Graham

Never had a problem with focusing.


I used an Antaries 5x Barlow.


Pat technically speaking it was pushing the boundaries of the scope but if you don't try you never know.


Edited by Graham

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Brantuk

The 200P has two varieties: fl=1200 and fl= 1000.


 


I only know cos I'm getting one tomorrow lol. :)


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Brantuk

1200's the dob (1000x mag) - the other is the EQ mounted ota (833x mag) - both optimistic to say the least in UK seeing lol :)


 


(probably could be done in the Arizona desert)


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Graham

Pat my Helios 200 is an F1000.


If I remember correctly focus was achieved at around 20 - 30 mm from max inward focus travel.


If you want it exact I can set it up again and measure it.


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Brantuk

12DString says it's possible with Graham's gear Pat (assuming 12DString is working ok) - it sure looks possible on a good night. :)


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Graham

12DString says it's possible with Graham's gear Pat (assuming 12DString is working ok) - it sure looks possible on a good night. :)

 

Well excuse me if I start taking humbridge to this conversation.

I know bloody well it works I have the photos to show for it.

:angry: :angry: :angry:

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Graham

I still find it hard to beleave i can not achieve focus with x3 at 2350 be as angry as you like GRaham ,with my 300p fl1500mm i could not focusmwith my x3 tal thats why i find it hard for me to, take in

Pat

 

Pat it is not a fact of getting angry.

I answer a question with a straight fact of what I have used and it is being openly questioned.

I am not in the habit of creating fantasies.

If my word is not good enough then fine.

In future I just won't bother to pass on the information I have gained from pushing the boundaries of what can be achieved.

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Brantuk

I'm not doubting you Graham - I'm trying to drag up numbers to show Pat it's possible with your scope. He's interested because the stated maximum practical power potential for the 200P is 400x and you are working at 833x magnification. I know you've proven it with the pics and it's a cracking shot. I'm sure everyone would like to know how the numbers work because we'd all like to get a pic like that. Sorry if you've read me wrongly. :)


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Graham

No probs Kim.


Its been a bad few months for me and it just got a whole lot worse so I am a bit touchy at the moment to say the least.


If my reaction was over the top then I too must apologise to all.


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