Re: [APML] Guiding (was M101)

["Steve Lindsey" <stevelindsey@earthlink.net>]

Scott,

What's the fl of your TV101NP?  I thought it was considerably less than my 
TEC which may accomodate guiding with the small BORG.  Mine is 980mm and the 
TV85 I guide with is at about 600.  BTW when I have my G11 set up right I'm 
getting about 0.2 to 0.3 pixel average errors which corresponds I believe to 
about A1's in ST4 speak (which is better than I've ever done guiding an SCT 
for sure!).

Steve

----- Original Message ----- 
> Greg, Steve,
> I am using the Mini Borg 60mm with my ST4 and it seems to like it a lot. I
> haven't had any problems using it the last few times out since I made the
> switch. It's light and very compact, the main reason I made the switch to
> keep my AP400GTO from overloading. Since I moved to the larger AP mount it
> still working great, A0's and A1's.
>
>
> Scott Hammonds
> www.creatorsview.com
>
> -----Original Message-----
> From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] 
> On
> Behalf Of Greg Hartke
> Sent: Wednesday, May 04, 2005 7:01 PM
> To: Steve Lindsey; Discussion of Film Astrophotography
> Subject: Re: [APML] Guiding (was M101)
>
> Hi, Steve,
>
> I've been imaging with my 152 mm f/7 refractor so the focal length is 1064
> mm. I think the focal length with the Mini Borg is adequate for most 
> imaging
> applications with the STV but I'm not so sure about the ST-4. Then again,
> with the 60 mm and a 300 mm focal length (I think it's f/5, too), that 
> might
> work with the ST-4. I used to know how well the ST-4 performed its
> centroiding computation but I lost those figures when I my old computer
> died. (D'oh.) Let's think a second... At 300 mm focal length, the image
> scale is (to lowest order) 0.0033 radians per millimeter. Let's assume a
> pixel size of 7.4 microns = 0.0074 mm. This says that one pixel 
> corresponds
> to to an angle of 2.47 radians = 0.001413 degrees = 5 arcseconds at the
> focal plane. If the centroiding is performed to 1/5th of a pixel (a
> reasonable and, I think, slightly pessimistic guess), then you'll get
> something like 1 arcsecond guiding accuracy. Hmm. Might be marginal.
> Everyone I've noticed going the compact guidescope route these days has 
> been
> using an STV. Has anyone here tried guiding with an ST-4 at something like
> 300 mm focal length?
>
> Regards,
>
> Greg
>
> ----- Original Message -----
> From: "Steve Lindsey" <stevelindsey@earthlink.net>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Wednesday, May 04, 2005 6:26 PM
> Subject: Re: [APML] Guiding (was M101)
>
>
>> Greg,
>>
>> I thought of getting a 60mm BORG for guiding but thought the focal length
>> with an ST4 was getting low for imaging at 980mm with my TEC.  What fl do
>> you image at guiding with the BORG/STV combo?
>>
>> Steve
>
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