Re: [APML]: Recommendations for ST-4 Accessories

[Jerry Lodriguss <jml@astropix.com>]

deMike wrote:
>>  I am planning to order the ST-4 to use as a guider
>>with the following system:
>>
>>   AP 600 (early, non "E") mount
>>   AP 130mm F/6 refractor
>>   AP 80x900mm Guidescope
>>
>>  Are there any recommendations from this group
>>for additional accessories that would help in the
>>autoguiding or setup?


Chris wrote:
>The #1 accessory that you need is a Spectra Flip Mate!!!  You can't use the
>ST4 without this... 8)


Sure you can!  With this stable a mount and a refractor, you don't need the
Flip Mate. 

If you had some SCT with mirror flop, on one of those "forked" mounts, then
probably you would!

Here's a trick: 

First couple of times out, focus your guidescope and ST-4 with the
readouts, maximizing the number readouts, but not oversaturating the chip
(say over 75).

After you are familiar with this method of focusing, on a night of really
good seeing, focus the ST-4 by the numbers. Take a little time to really
nail it. 

Then place your guiding eyepiece in the guidescope with a barlow attached.
Then (here's the trick part), focus the eyepiece by sliding it in and out
of the barlow. Then lock it down really good, like with two set screws.

Next time you go out, it will be parfocal with the St-4, and you can focus
it, and center the star in the guiding eyepiece box at the same time,
therefore focusing the St-4 and centering the guidestar on the chip.

If you spend the money on a guiding eyepiece and barlow instead of a
flipmate, at least you will have a fall back position if your ST-4 doesn't
work some night for some reason. You will also need a guiding eyepiece
anyway for when you drift polar align.

Also, I find with the ST-4, the AP 130EDT, and a 12mm guiding eyepiece and
3x barlow, I know exactly how faint of a star I can guide on at a one
second integration with a boost of 3 or 4 in the brightness Adjust average
mode. With this setup,  IF I can the star in the guiding eyepiece, I can
guide on it.

Jerry