f6.3 m42 not right

[blink138]

hello members slowly but surely getting there!
anyhow can somebody explain this phenomenon? i was so excited about the amount of information from an f6.3 reducer, each individual frame looks fantastic but see whats happened
an f6.3 stack of the tarantula looks the same
1000d and only a load of 15 sec exposures (12)
thanks in advance
pat

[Starcrazzy]

You say the individual subs dont have the ring??.. Must be a stacking issue then..
Nice shot though, good detail..

[blink138]

thanks starcrazzy
i have included one 15 sec light..... perhaps it is there on this photo or it could just be the glow from m42 itself?

[matty84]

hey Blink,
I think the problem is vignetting, what size t-piece for your camera are you using is it 1.25inch or 2inch.It seems that the chip might be covered by either your t-piece or a extender or something, i would be looking at getting 2 inch adapters or t-piece so that the chip of the camera can gather all the light. Also flat fielding corrects for vignetting which is something to look into.
Matt

[multiweb]

What you see is vignetting. Flat fielding will easily fix that.

[blink138]

thanks for your reply matt
i purposely went out and bought the hotec 2" adapter
strangely the photos are ok at the native f10 as i have asked for help on a few of those over the last week
i hope it has got nothing to do with the reducer in the system.... that would be a major bummer because the information at f6.3 is amazing
pat

[blink138]

ah i have just seen marcs reply also........ so how can i do this flat fielding?
sorry but these are the first times i have EVER used a dslr
pat

[multiweb]

Just take a couple of pictures of an evenly illuminated surface like the sky at dawn/dusk or a white laptop screen or lightbox, EL-sheet, etc... There are many ways to do it. Search on these forums for lighboxes, etc... There's a basic tut on flat fielding in this site resources and articles section.

[blink138]

thanks matt and marc
will just two be ok.... and do i need a set time of exposure?
pat

[multiweb]

You'll need to combine a stack. I usually stack 80 subs. More info here (http://www.iceinspace.com.au/63-211-0-0-1-0.html).

[blink138]

thanks marc, seems complicated, but if thats what we all have to do then so be it
pat

[multiweb]

It does sound complicated but it really isn't once you get used doing it. Calibration is well worth your learning and your images will improve ten folds as your data acquisition is already excellent.

[blink138]

wow thanks marc!
pat

[BlackWidow]

I think your focal reducer is too far away from your camera. I had the same trouble with my Lx200 when I had the reducer at the back of the scope. Now I have it in front of the T- mount near the camera. It has fixed the problem. Where you place the reducer will change the F:stop so you might not get the full f:6.3, but you won't see a great deal of change.




Regards
Mardy

[blink138]

thats very interesting too mardy
i have put a fair bit of research into this and i know there is a lot of discussion about the subject on the various blogs...... however i purposely ordered the moonlite focuser that was designed to house the f6.3 reducer, so that had better not be the problem!
pat