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Old 06-01-2009, 06:31 PM
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CCDCalc how to add Camera Lens?

Hi All,

I am trying to work out FOV for my Camera lens and SXVF-h9 combo. How can i cauclulate the FOV etc using CCDCalc? Can someone tell me what values i must enter for Apperture, FL, etc in CCDCalc for a given camera lens?


Is there some other program out there that is simpler to use?

Also how can i add a Camera Lens to Starry Night or CDC etc?

I would also like to know the math to calculate this for myself. IF someone is willing to explain the math.

Regards
Fahim
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Old 06-01-2009, 06:51 PM
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Ok check and see if i have this correct.

Lens 135 f2.8 prime. If used at F2.8
Then the Aperture is 135/2.8 and FL is 135. Is this right?
If used at F4 then Aperture would be 135/4 and FL is 135.
So for each F setting I would need to create an entry in CCDCalc. Is that correct.

Also I would I assume have to add any extra distance added by my CCD Camera to Lens adapter.

I have ordered a Starlight Xpreess to EOS adapter and a EOS to M42 adapter. Using this combo I am hopping to be able to use both my EOS lens and any future M42 lens I can bargain hunt down.

I found to useful sites to track down Sensor to Lens Distance requirments
http://www.markerink.org/WJM/HTML/mounts.htm
and
http://www.ayton.id.au/gary/photo/photo_lenses.htm (under lens mount adapters).

Regards
Fahim
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Old 06-01-2009, 07:22 PM
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Fahim, you are correct, CCD_Calc requires separate entry for each aperture, or F-setting.

Be aware, that FOV does not depend of aperture. It does depend only of lens FL and sensor size.
Also, FOV does not depend of adapter (unless adapter contain lenses, which I hope yours does not. In that case, there should be factor known, to calculate the final FL).
Aperture will affect the final photo, in terms of required time to record certain stellar magnitude.
It will also affect the appearance of extended sources (nebulae), however as F-setting.



I am using Cartes du Ciel, to show the FOV of particular lens.. there is a button (red concentric circles). If you right-click it, the table will appear wher e you can enter various eyepieces and CCD FOV's.

Last edited by bojan; 06-01-2009 at 08:09 PM.
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Old 06-01-2009, 07:41 PM
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Bojan, yes but this CCDCalc program seems to rely on you entering the FL as a ratio so the Aperture must be given for it to calculate the FL.
One other thing I dont know if it is a bug in CCDCalc, but does Bining the CCD increase the FOV? CCDCalc only shows an increased ImageScal in terms of Arcsec/pixel resolution but the FOV does not change. Is this right or is there a bug in CCDCAlc.
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Old 06-01-2009, 08:11 PM
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Bining can not change the FOV, it can only change the scale (pixel/arcsec)
I will have a look...
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Old 06-01-2009, 08:13 PM
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Yyou can enter FL and adjust aperture or F-setting.
I am now having version 1.415 on the screen.

I think Cartes du Ciel is much more useful for this task (not so nice looking though).
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Old 06-01-2009, 08:14 PM
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The focal length of the lens won't vary with the adaptors you use. They only provide the necessary "spacing" between the lens and the CCD. The lens will still be a 135mm FL.
Binning will only affect the pixel resolution not the field of view.

To do the calcs yourself:
The FOV is directly related to the CCD chip size and the FL of the lens.
FOV = ArcTan (CCD chip length/FL of lens)
ie for a 20mm chip on a 135mm fl lens the FOV = arctan(20/135)= 8.4 degs
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Old 06-01-2009, 08:19 PM
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Nope, bining does not change anything, as it should be.
No bugs.
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Old 06-01-2009, 08:24 PM
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Ok I have got it now. Only the FL and Size of Chip matters. But for CCDCalc I will need to work out the Apperture just for entry purposes.
I can understand now why binning does not change anything as the Chip size is still the same. So a Lens can only give you one FOV, unless you use a barlow or reducer (With lens).

How do Macro Extension tubes work then? What is there purpose, as they dont have any lens in them, but one would assume they do increase the FL.
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Old 06-01-2009, 09:22 PM
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Correct.

Macro extension tubes are here to increase the distance between sensor and lens, so that lens could focus on objects that are closer.

There is formula:

1/FL = 1/A +1/B

where A and B are distances between optical centre of the lens and object and sensor.
If you work it out a bit, you will see how it works...

Last edited by bojan; 06-01-2009 at 09:33 PM.
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  #11  
Old 12-11-2009, 03:33 AM
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> Is there some other program out there ..

Sure! You are welcome to visit my site and to download my software at:
http://www.astrodigital.net/download.../download.html

Don't forget to sign my Guestbook ;-)

Thanks!

Bye
Panagiotis
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