Focus, Flats and NGC 80

No moon, the evening started with thin cirrus clouds that disappeared, I think an hour or so after sunset.  With those kind of clouds, I’m never sure, I think they are actually there to make halos and generally degrade the image, but you can’t see them.  I thought good enough for a focus run with FocusMax.  I did find that the focuser wants to be connected to Maxim or FocusMax, but not both.  So I connected to FocusMax and pretty much just ran the “First Light” routine.  I selected a 4th mag star in Pegasus, and began the run.  The routine built a pretty straight slope from the left, and as the star approached focus, it had an obvious bloom spike.  The curve bottomed, went up, then back down, then up again in a fairly tidy rounded W shape.  FocusMax didn’t like the bloom; the routine failed.  The recommendations were for a “fairly bright star”, mag 3-5.  A nearby 5th mag star had the same result.  But when I ran it with a 6th mag star, the routine ended with a very tidy vee curve.  The wizard then did a sample auto-focus, which was pretty far off.  The curves are written to a system_profile file, which had some old runs in it; I deleted the old runs and made another v curve.  Then the autofocus routine came in fairly close.  I ran about 6 V curves which all looked pretty similar.  After re-reading the documentation, I see I should manually expand the in-out range of the focus run and use smaller intervals, which should provide a more accurate focus.

I shot a luminance series (10- 120 sec) on a  field that looked interesting in TheSky, in what I assumed to be Pegasus, but turned out to be Andromeda. The East side of the Great Square is really right on the border. The field includes NGC 80, and about 22 other galaxies including NGC 81 and 83.  not exactly showcase objects, but a very rich neighborhood!  I think the focus still needs work, and also still have somewhat oval stars in the east-west direction.  Pixinsight actually tidies those up via data rejection.

Field centered on NGC 80; 10 – 120 sec luminance with 12″ Meade LX200 and ST-10XME. Calibrated and stacked in Pixinsight, linear adjustments in Photoshop.

I set up a white foam core flat field target at Park 1 position on the wall of the hut.  It’s illuminated with a 15 watt incandescent lamp in a floor fixture that’s aimed at a white foam core target on the opposite wall.  For remote operation, I can turn on the light via a web switch. (not set up yet)  It gave a well exposed flat field in a 1 second exposure.  It seems like there should be a good way to objectively analyze how flat the field actually is.  The line analysis tool in Maxim showed an apparently symmetrical distribution vertically and horizontally.  Also the color temperature of the illumination is maybe 3200K – a low wattage bulb mixed with bounce from unpainted plywood –  so there are color implications.    Never the less, the flat seems to do a good cosmetic, at least, job of correcting the light images.

2 thoughts on “Focus, Flats and NGC 80”

  1. Nice blog on the AP1200. I have been using one for a few years now but have not attemped to use PemPro with Maxim and a planetarium program. Would you be willing to share what you have learned concerning the required cables? Can you use the same RS-232 cable for Maxim’s Observatory control and PemPro?

    • The AP1200 is connected with RS-232 to COM 1 (serial to USB adapters would work fine). The key is the AP ASCOM driver, which all other software FocusMax, Maxim, PEMPro, and theSky connect to. The driver is a server that handles all mount commands from all connected software via the single serial cable. The AP-GTO group on Yahoo is the ultimate source of all wisdom on connection issues.


Leave a Reply