Re: Suresh Mohan commented on Suresh Mohan's photo

[aarthi pa]

Hi Suresh,

Thanks for replying. I own a celestron 6N reflector scope. I think the best images I have seen so far is that of the moon and saturn. I haven't got into the photography part yet. Did you say these were pictures taken from your webcam? How do you get this kind of definition?

Also, I was wondering if i should buy a televue's powermate or a barlow.

The sales guy at OPT replied
"For your telescope I would recommend the 2x powermate over the 2.5 or larger.  This would still allow for a usable amount of magnification from the 20mm you currently have and allow use with other eyepieces you decided to get in the future.  The difference in the 2x over the rest is just the magnification and that’s it.  With the 5x it would be great if you only used low power eyepieces and did not want to invest in higher magnification eyepieces.  The 2x will give you a higher power for what you have plus for future higher power eyepieces."
 
What do you suggest?

Regards,
Aarthi

On Thu, Jun 10, 2010 at 10:16 PM, Picasa Web Albums <picasawe...@google.com> wrote:

New comment after your comment By Suresh Mohan Suresh Mohan Jun 10, 2010 9:43:19 AM Hold on !these are web cam images and i hope u did not meant to compare with your visual images, in case u need an explanation pls contact me on my mail or yahoo groups Post reply Unsubscribe from this conversation

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[drsureshmohan]

If u already have a good set of eye pieces just go for the 2x
powermate. When u use a webcam u take multiple exposures of the same
object ie about 100 frames of Saturn or moon. Here is some funda .

The nature of light itself is to be noisy, because it arrives in
packets , the random arrival times of these packets cause noise.
Since light packets arrive at a random, noise also arrive randomly !!
But here is the good part Noise though reaches the the CCD will only
be a fraction of the signal.In fact noise is the square root of the
signal! Since that is the case a stack of 2 frames will have signal
to noise ratio of 1.4(sq root of 2) a stack of 100 frames will have a
S/N ratio of 10 ! A stack of 1600 frames it will be 40, higher the SN
lesser the noise or grain that u see ; my pic of Saturn has 1600
frames ie a stack (stacking is done thro free software called
registax) hence i got good resolution and i was using a 10 inch with 2
barlow ie focal lenght of 1600

Hope this helps

Suresh

On Jun 18, 12:07 pm, aarthi pa <pa.aar...@gmail.com> wrote:
> Hi Suresh,
>
> Thanks for replying. I own a celestron 6N reflector scope. I think the best
> images I have seen so far is that of the moon and saturn. I haven't got into
> the photography part yet. Did you say these were pictures taken from your
> webcam? How do you get this kind of definition?
>
> Also, I was wondering if i should buy a televue's powermate or a barlow.
>
> The sales guy at OPT replied
> "For your telescope I would recommend the 2x powermate over the 2.5 or
> larger.  This would still allow for a usable amount of magnification from
> the 20mm you currently have and allow use with other eyepieces you decided
> to get in the future.  The difference in the 2x over the rest is just the
> magnification and that’s it.  With the 5x it would be great if you only used
> low power eyepieces and did not want to invest in higher magnification
> eyepieces.  The 2x will give you a higher power for what you have plus for
> future higher power eyepieces."
>
> What do you suggest?
>
> Regards,
> Aarthi
>
> On Thu, Jun 10, 2010 at 10:16 PM, Picasa Web Albums <
>

> picasaweb-nore...@google.com> wrote:
> >  [image: Picasa Web Albums] <http://picasaweb.google.com/>

> >  New comment after your comment
>

> > <http://picasaweb.google.com/lh/sredir?uname=drsureshmohan&target=PHOT...>
> > By Suresh Mohan<http://picasaweb.google.com/drsureshmohan?feat=comment_notification>
> >    Suresh Mohan<http://picasaweb.google.com/drsureshmohan?feat=comment_notification>

> > Jun 10, 2010 9:43:19 AM
> >  Hold on !these are web cam images and i hope u did not meant to compare
> > with your visual images, in case u need an explanation pls contact me on my

> > mail or yahoo groups    Post reply<http://picasaweb.google.com/lh/sredir?uname=drsureshmohan&target=PHOT...> Unsubscribe
> > from this conversation<http://picasaweb.google.com/lh/editCommentSubscription?target=PHOTO&u...>
> >  Unsubscribe <http://picasaweb.google.com/lh/settings#emaildigest> from
> > these notifications.

[sathya kumar prasanna]

and all this while I was under the asumption that the electronics got noise because of the heat. umm.... thanks for the gyan doctor. it really helped clear things up.

Sathya

> > these notifications.

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[Suresh Mohan]

Hi Sathya,

 You were not wrong at all. After all there are two types of noise 1 Shot noise which I discussed below and 2 System noise from CCD which is repeatable and hence be subtracted and finally Read noise ie due to the pixel not being able to count the electrons properly.

Suresh

 

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