First attempt at M5 - first image at new house

[Gem]

Hi!

Just moved to the next suburb in Canberra. The new place has a great courtyard for astronomy (but isn't very even).

Here is the first image. It still needs more processing (my wife is too busy with the move to process it atm :rolleyes:).

I find it tricky balancing exposure times for globs so that the core is still nice. :(

Scope: 9.25" SCT
Mount: CGEM
Camera: ATIK 320E
Guiding: 80mm with QHY5 and using PHD
Stacking: AstroArt
Exposures: 70 x 30 sec plus darks + bias

[blink138]

heh grant did you try and focus on a bright star first?
despite it being a little awkward i seem to get a good focus just using the cameras viewfinder
pat

[Gem]

I used a bah-mask to achieve focus on a bright star. I think part of the problem is guiding at 400mm focal length while I image at 2350mm.

Here is the wife-processed image...

[blink138]

ooh thats quite a nice glob, perth is "supposed" to have a clear day and night tomorrow, i might check this one out
pat
by the way grant why is there a problem guiding and imaging at different focal lengths?
i will need to know these things soon enough so i am glad you have mentioned it
pat

[Gem]

No problem at different lengths - just that 2350 is really long compared to 400. The shorter the main scope's focal length, the more forgiving it is of errors in tracking. It is easier to image at shorter focal lengths. :)

[blink138]

ah i see what you mean..... i tried some at f6.3 and things happen an awful lot quicker!
pat

[graham.hobart]

Nice glob!
The rough rule is supposed to be guide down to roughly one third the focal length of your imaging scope or something like that, saying that I guide quite well with a modified finder scope on a 900mm FL refractor.
I think it gets much more unforgiving when you are +1000 FL
The image scale becomes an issue as well if you use a small finder as guider but then try and guide a 2000+FL scope.
You can try binning the guide image but essentially the rule of thumb keeps you happy.
keep em coming'
:DGraz

[bmitchell82]

Guiding is a tricky one, back in the days where auto guiding wasn't avalible same FL was the way to go, as when it moved the then your actual movements where small compared to the film

With the advent of modern guiding software and CCD's well you can get sub pixel guiding.

here (http://www.iceinspace.com.au/forum/showthread.php?t=90791) is a picture of a GSO RC10 guided with a Orion Finderguider and SSAG on a EQ6 (properly tuned) and properly polar aligned. Sure its not pin point, but considerin the Finder is 200mm and the RC is 2000 mm... its doing damn fine!

here (http://brendanmitchell.net/?p=386) is my take on guiding more focused towards OAG but you can get a bit of a background on my findings.

[alistairsam]

Hi Grant,

I think the issue here is more with focus than guiding, as your exposures are only 30 secs. Agreed, the long FL will require a longer FL at the guidescope and your FL ratio is around 1/6th, but I'd suggest getting the focus sorted out first.
what did the phd guiding graph look like?
Just take short exposures adjusting the focuser each time till you get the sharpest result possible without the mask and compare the before and after.

[Gem]

I use a bah-mask to focus. Obviously I can always do better, but the focus wasn't too bad. Unfortunately, my dew heater is going full bore to keep the Canberra frost from setting in... so the SCT isn't well cooled down.

[graham.hobart]

Brendo!-Love your work!
Fancy tuning up me old EQ 6?
Focus is truly the golden abalone here. This is the issue I have most consistent issues with personally, as I have never been really happy with what came out of the other end after trying my damn hardest. Use a mask, use your eyes, use software (FWHM or HFD) I remember a post Leon did some time back about just taking your specs off and squinting-sort of a mammalian diffraction mask!
Gem, you count yourself lucky you have her indoors to do all the processing, so you can concentrate on the looking at the beautiful night sky, taking some pictures (and drinking some fine hooch to keep the mozzies away)
The slope is steep and expensive, but it is well worn and pats on the back make it an easier climb. :thumbsup:
Graz from Taz

[jjjnettie]

Congrats on your first light from your new home. :)
Your wife does a wonderful job with the processing.

[Gem]

Thanks.

Good news! I just order a Celestron 6.3 reducer/corrector. Should help things a bit! :)

[Astromet]

good job! try to sharpen the focus a little more;)