Ghost of Jupiter

[AstroJunk]

NGC 3242 taken with a GSTAR-EX through SDM006!

It's my first night out with my new toy, so I don't know what I'm doing. Random settings and the AVI bunged through registax using defaults. A little added contrast, but that's it:thumbsup:

[jase]

Great work :thumbsup:. A very suitable target for your FL (2540mm). You've resolved some nice detail in the outer shell. This scope would be dynamite mounted on a large GEM or equatorial tracking platform - produce some exquisite narrowfield images with an AO unit. Looking forward to seeing more of your work.

[Bassnut]

Wow, thats hard to image, nice work!.

[Ric]

What a beauty, a great first light for your new toy. I have yet to capture a decent image of the ghost, quite a tricky little beggar.

Cheers

[iceman]

Excellent work Jonathan! The g-star coupled with that large aperture will let you get some real faint stuff.

Very nice work.

[davidpretorius]

hey thats realy good!

[AstroJunk]

That's about as good as it got for the night - there was a rather large shiny moon after all! It promises to be a fun toy. I'll have to get more scientific tonight.

[rogerg]

Nice shot :thumbsup: That was one of the first objects I photographed with my ST7.

[AstroJunk]

This one is much better - avi from a second run i had.

[Rodstar]

Just out of interest, Jonathan, how does that object look to your eyes as a visual object through SDM 6?

It is one of the most impressive objects I have seen through my scope. To my eyes, the inner shell looks a turquiose colour, and the outer shell a lilac/light purple colour

[AstroJunk]

Yeah, it's lovely isn't it!

The camera is much more light sensitive than the eye, so it can get more detail, but on a good night there is still plenty of detail to be seen visually, and in colour for a change.

I have become much more interested in planetaries since getting some serious light gathering ability - I'm planning to see how many I can track down.

[jase]

Reflecting on this scope further (no pun intended)... it would be a prime candidate for CCD TDI methods as you don't need to guide or at least not very accurately. I suspect a dedicated astro CCD would provide you with more image depth than the g-star, but I haven't had any experience with the latter. Can help out with CCD TDI techniques if desired.
Do you know what the image circle is on the scope?

[AstroJunk]

I've heard of TDI - sounds an interesting technique, and i'll look into it when I have a clue what I'm doing! I was going to have a go at autoguiding tonight to see if any degree of accuracy is possible with ServoCat.

How do I calculate/measure the image circle?

[Dr Nick]

Nice shot! ;)

[skeltz]

wow what a nice looking scope!
hmm nice scope ...avater...astrojunk????
anyway mate looks like a very nice toy:thumbsup:

[AstroJunk]

Tonights effort - this time with a barlow making a fl of 5080mm

Max gain and using 128x integration. Processed in registax, 50 frames, default settings with darkframe subtraction. No further modification!

For interest, I've added the colour from hubble to the second image. I hadn't appreciated how asymetrical the outer shell was.

I'm hooked!!!

[jase]

Magnificent images. 5080mm is stoking it! Your seeing is undoubtedly good or at least your arcsec/pixel combo suits the conditions very well.



Image circle at the focal plane is defined by two factors. Firstly, the i.d of your focuser. If you’re using a typical 2” (50mm) focuser then obviously you’ll never get an image circle larger than this. Most astrographs have a 3” (76mm) or 4” (101mm) focuser to cater for larger format chips. Secondly, how much of the light is usable or put another way - the flatness of your light path. Commonly, coma in parabolic mirrors distort the edge of the FOV, thus the full light path can’t be utilised without some form of flattener in place. I did have a formula for calculating field flatness in an optical design, but it was based on a refractor’s objectives. As you’d expect, this also depends on chip size. It is typical, that even if you have a large 4" focuser, the image circle will not be 101mm. An example of this is the Takahashi FSQ, it uses a 4" focuser, but the image circle is 88mm.