M81 M82 Saturday morning from Beckenham

[The Thing]

Meade LX90 8" 9 x 4m subs, Minolta Dynax D7, Orion Skyglow SCT filter, Baader Alan Gee II Telecompressor, guided with SPC900NC with B/W chip modification and PHD. Processed in Deep Sky Stacker and The Gimp.

The SkyGlow filter causes excess vignetting with the Alan Gee Telecompressor as it screws on the back of the SCT and moves the CCD away from the Telecompressor (reducer/flattener).

[JohnP]

looking not too bad Dunc - loads of detail in m82...

John.

PS - your avatar is really annoying I keep thinking windows is still downloading something.....!

[The Thing]

Thanks. Better transparency and more practice required.

p.s. the avatar is annoying me as well. Time for a change.

[MarkS]

Well done Dunc.

M82 has come out better than M81 for some reason.  The M82 colours have come out well.

The background consists of a large curved "sweep".  What causes that I wonder  -  did you need to de-rotate the subs before stacking?   

So you're using a B&W modded SPC900 - did you mod it yourself?

Mark

[Rocket Pooch]

Good start Dunc, guiding looks pretty good and the image is composed well, so I think it should work out quite well, was the focal reducer a .67?

[RobertM]

Looks very good for a start Dunc, it'll be much easier when you've sorted out that vignetting with the FR.

[The Thing]

The image is full scale and has been cropped. The galaxies are right at the edge of the field, top and bottom of frame, off centre to get away from the amp glow. The arc is a residue of the vignetting which I would have hoped would have been removed by the flats.

It's hard to know what the FR ratio is with the Baader. There is nothing supplied with it to tell you what different combinations of bits result in with different SCTs. The unit fits inside the baffle tube which is neat and you have to use their adaptor to attach the T-mount to the SCT which gives you the correct distance for a DSLR (I suppose - no notes supplied). It has two extension tubes to move the lens assembly to different points in the baffle tube to produce different f ratios. Only one tube can be used with the LX90 8" as there is a baffle inside the tube preventing the unit going that far in. Of course this means that the distance of the lens unit to the CCD is variable invalidating my earlier supposition. So it shouldn't matter that I have inserted a screw on SCT light pollution filter in the light train as far as distance is concerned.  However the arc that has been noticed is a residue of vignetting that doesn't occur if the light pollution filter is omitted.

The light pollution filter has accentuated the colours a lot. Maybe a bit too much.

I modified the SPC900 myself. It was easy once I had bought a smaller soldering iron! LX mod next I think.

I need another clear night to have another go, I think it will be M82 as there is so much more detail to see.

Thanks for all the nice feedback!

[Fay]

Duncan there is a lot of detail in M82. It seems well  focused, and if you could get rid of the swirly lines it would be quite nice!!

[The Thing]

Another blast, better framing but let down by wind and clouds. 23x 4mins same set up as before but using an artificial gradient removal rather than flats. All the details are in the gallery http://gallery.orpington-astronomy.org.uk/displayimage.php?pos=-734

[MarkS]

The background looks a lot better on that one and it's well composed.  I love the "picture postcard" frame and description on the image.  It makes it look quite professional.  How do you do that?  With Photoshop?

The stars away from the centre seem to be suffering a bit from either coma or rotation - I didn't notice that in the earlier image.

Mark

[The Thing]

The flashy border is done with a Gimp plugin, part of Astro plugins 0.6 by some German guy, the link is in my gallery entry. Its very easy.

I think over application of the star rounding plugin has resulted in the non-roundness of some of the stars, also I need to be more selective when I include subs - I tend to use a 'more the merrier' approach rather than weeding out the carp :-} If I get some time today will reprocess to see if I can improve things.

[Ian]

do we need to be changing the society name to the orpington astronomical and fish botherers society? I am concerned with the number of fish being pulled out of imaging rigs.

Note, Schmidt Cassegrain telescopes are not an substitute for a properly heated and maintained aquarium. Even if you do get to enjoy your piscine companions when it's cloudy.

[Rick]

I love the "picture postcard" frame and description on the image.  It makes it look quite professional.

That sort of thing is fine for a version you're going to print out on nice high-quality paper or card, but it tends to look rubbish when the image is re-sized for on-line display at less than full resolution, so I discourage it for images in the gallery. At least in this case the annotation is clear of the actual image...

[Mike]

Note, Schmidt Cassegrain telescopes are not an substitute for a properly heated and maintained aquarium.

A SCT can make a very nice home for your aquarium fish. Just make sure it is 100% full of water so there are no air bubbles and make sure you keep the water clear so it does not upset your image. Cold water fish are better if you keep your SCT in the garage and also heated water can cause strange distortion in your images.

The fish make interesting diffraction spikes, but as they move around you can average them out from frame to frame.

[Ian]

you'll have to be damn quick changing whatever you've got screwed into the back. Something to try at DSC perhaps?

[MarkS]

... application of the star rounding plugin has resulted in the non-roundness of some of the stars ...

Doesn't sound like a very useful plugin!

[The Thing]

Doesn't sound like a very useful plugin!

It could be very useful - but it has a lot of sliders to play with and some non-obvious captions. But it does play with your stars in real time so you can see the effects. Better to start with round stars though!

[Mike]

What's the point of a star rounding plug-in if you need to start with rounded stars to ebing with?

[The Thing]

Latest attempt. Now has 1 hour of subs. Processed in Deep Sky Stacker and then GIMP. Darks, flats and bias frames applied. Getting better

[MarkS]

Dunc,

That looks really dim on my PC - I can't see any detail.

Mark

[The Thing]

Mark, On my PC and laptop it looks dim but OK. How does the previous image look to you? My screens are calibrated using Panatone Colorvision. Maybe I am dimming them down too much to darken the sky.