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Bill Keicher

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#1 zoltrix

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Posted 26 February 2021 - 06:54 AM

Hi all

I download the pdf by Bill Keicher

https://visns.neocit...17SolarEclipse/

Providing maximum exposures over AZ mounts

I wonder whether it is on optimistic side

My declination in Milano is 46°

If so I dont see any reason for an EQ mount

I could set 30 secs exposures time everywhere apart from a small portion of the sky

In the book "Astrophotography on the go " the scenario was quite different

What's your experience ?

Do you follow, with success, Bill's suggestions ?

#2 alphatripleplus

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Posted 26 February 2021 - 09:41 AM

I download the pdf by Bill Keicher

https://visns.neocit...17SolarEclipse/

Providing maximum exposures over AZ mounts
 

I don't see any reference to maximum exposures for Alt-Az mounts in that link - it appears to discuss only viewing a solar eclipse. 

 

Do you have the correct link?



#3 S.Boerner

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Posted 26 February 2021 - 11:11 AM

It is buried  in there but you'll need to search the page for Bill Keicher to find it.

 

FWIW I read the article in question years ago and really liked it. I made a post about it in 2019 here:
https://www.cloudyni...er#entry9581390


Edited by S.Boerner, 26 February 2021 - 11:14 AM.

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#4 alphatripleplus

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Posted 26 February 2021 - 11:34 AM

Thanks, I'll take a closer look and see if I can spot it.



#5 donstim

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Posted 26 February 2021 - 01:02 PM

Why not just link the actual document?  https://visns.neocit...Rotation V3.pdf

 

Note that these plots were made for a camera with a small sensor diagonal size (6mm). The amount of rotation at the diagonal's edges will be greater for a larger sensor. And he doesn't fully explain why a maximum amount of blur allowed of 10 micrometers is appropriate..


Edited by donstim, 26 February 2021 - 01:14 PM.


#6 zoltrix

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Posted 26 February 2021 - 01:53 PM

apologize for incorrect addressing
ok, the plots were made for a 6 mm sensor but this is about the size of mid priced cmos
A great portion of the sky should be accessible even with AZ mount
in the book "astrophotograpy on the go " the scenario does not seem to be so favorable, , unless I misinterpreted something
What about your experience ?

#7 roelb

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Posted 26 February 2021 - 07:26 PM

When I started EAA I took care of the maximum exposures as a function of the part in the sky: Attached File  Field Rotation.pdf   52.77KB   9 downloads

But now, using SharpCap, I don't bother with those restrictions but limit the sub exposure times to maximum 60 s.


Edited by roelb, 26 February 2021 - 07:26 PM.


#8 zoltrix

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Posted 27 February 2021 - 07:52 AM

Hello

The table posted by roeld is the one of the book "astrophotography on the go"
As you can see it seems there is a substantial difference with Bill's plot
Take a north or south oriented celestial object , 30 secs exposures, 50° declination
the former declares 50° maximum altitude the latter up to 75°
It should not depend upon the size of the sensor since the book is focused on economic set up
Anyway, from your experience, which one provides the most realistic informations ?


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