[Aavso-photometry] Beginner Questions..

[Chuck Pullen]

Another alternative to a wedge if you really feel you can't live  
without alt-az is a field de-rotater for your camera/filter wheel / 
focuser.  I think they are now available for Meade SCTs.  However, I  
can't believe that a wedge from Meade wouldn't be much less  
expensive.  Or make your own based on your latitude. You will have to  
address balance in declination, so plan on a counterweight system  
from either Losmandy or gen up something yourself (I used some scuba  
weights I had laying around with cable ties...  Nothing but the  
finest in my observatory!

Chuck Pullen

>
> Message: 1
> Date: Fri, 03 Aug 2007 08:15:07 -0400
> From: arne <arne at aavso.org>
> Subject: Re: [Aavso-photometry] Beginner CCD Questions..
> To: Derek C Breit <breit_ideas at hotmail.com>
> Cc: Aavso-photometry at mira.aavso.org
> Message-ID: <46B31C4B.9030808 at aavso.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Derek C Breit wrote:
>> So from what I see, essentially I might be able to do, essentially, a
>> whole lot of work to come up with essentially what the Visual  
>> observers
>> can do, only I *might* be able to achieve a bit better precision and
>> accuracy by using the CCD Charts on stars mag 11 and brighter..
>>
>> This does not really fit in with anything listed on the AAVSO  
>> website..
>> Not following a star beyond the reach of the Visual observers, that's
>> for sure..
>>
>> So, I will just familiarize myself with the process, so that when  
>> I buy
>> or build a wedge, I will be ready to do something worthy of  
>> reporting..
>>
>> Hopefully that doesn't take me another 5 years..
>>
>> For now, I just can't see going to all this trouble when I can  
>> just do
>> visual, and I have no real interest in putting the mobile 12"  
>> scope on a
>> wedge.
>>
>> So back I go into my corner to watch..
>>
> One of the first things in every book about CCD observing is the
> warning that you should have an equatorially mounted telescope
> with a good drive system.  You have invested thousands of dollars on
> a nice LX200, and more thousands on a CCD camera; you should be
> willing to spend a few more dollars on a wedge.  It will help your
> visual observing as well, after all.
>
> There are a lot of people who have to limit their exposure times,
> usually because their telescope drive is not capable of holding
> steady for long periods.  They do just fine.
> If you limited yourself to 30-second exposures with your current
> alt-az system, you can do one-percent photometry at 13th magnitude,
> which may not be fainter than you can do with your eye, but 10-20x  
> more
> precise.  That is one reason you bought the camera, right?  As  
> mentioned
> by others, you can also derotate and stack multiple images to go
> fainter - a bit of extra work that you would avoid with the wedge,
> but not impossible.
>
> Any telescope with any CCD system is capable of doing quality  
> photometry.
> You may have to initially limit yourself to a particular subset of
> projects, which will expand as you improve your system.
>
> I do not understand your comment about "this does not really fit in  
> with
> anything listed on the AAVSO website".  You might give more details
> as to what you mean.
> Arne
>
>

Chuck Pullen
pullenc at gmail.com