Stub Mandrel

14x bigger is magnification where I come from The problem is perceived 'magnification' of a astronomical image is a relative, not absolute, term. This is because we don't compare the image to the original object by putting them side by side, but by viewing the object as we see it unaided and holding the new image close to our eyes. As we can move towards or away from the real image its angular size changes so it can appear larger or smaller than the actual object depending on where we put it so we can't use this comparison meaningfully. When viewing a virtual image through a scope the situation is simple, as magnification is the increase in the angle subtended by the viewed object. This is because we see the virtual image at a fixed angular size. However, real images DO have a magnification - macro photography is defined as when the real image is larger than the original object, which depends on object-lens distances being less than the focal length of the lens. As Olly has pointed out, astronomical images are projected at vastly SMALLER sizes than the real thing - compare the size of a moon image with the real moon! The actual magnification of the real image is a tiny fraction. Judging the perceived magnification of such an image is like saying a sound is 20dB loud - it only has meaning if you know how loud the 0dB reference value is. A meaningful comparison is therefore between the image size given by some refernce lens (conventionally 50mm for a film SLR or 70mm for a typical APSC sensor) and the telescope. Rather than confusing beginners by saying longer scopes don't magnify, the simple explanation is: The size of the image is directly proportional to the focal length of the scope or lens, so all other things being equal (i.e. using the same camera or eyepiece) if you double the focal length the image will appear twice as large. To judge the 'magnification' of a telescope, divide its focal length by the focal length of the lens you are comparing it to, but bear in mind this figure may not be meaningful in the context of someone else's setup.

It's really nice data, you need to keep playing with it

A close look shows some stars against the nebulosity have dark haloes as well... sorry! As for ideas, only photoshop ones... Noel's Increase Star Colour and the soft-light & luminosity trick

Nice detail, but a bit short on colour.

You can stretch the image if the scale isn't quite the same. If my instructions seem complicated, be assured it's more difficult than that, I find it can take several tries! Very easy to align on the wrong star near the beginning.

Photoshop makes it very hard to work with split images, it's much easier in photoshop which has simple commands to split to various sets of channels and automatically recombine them. You may need to change the mode to grayscale first. Yes transparency is done with a slider when the layer is highlighted in the layer manager. You need to: Paste Ha on top of RGB Select Ha layer Set transparency Zoom in Choose transform tool Align the same star on both images at (say) stop right. Enable free transform (edit menu) Reposition the rotation centre (little crosshair at centre of image) on top of the aligned star (can take a while to find them when zoomed in!) Pan to opposite corner Type in different rotation amounts until the images register (you can go down to 0.05 degree in PS2, which is about good enough) Choose another tool and apply the transformation. Remove the transparency and set the mode to luminance. Adjust transparency to get the effect you want. To blend Ha only with the red layer you would split to RGB, do that on the red image, then recombine them.

I have to image it after it climbs above the house and before it hits the tree, roughly limiting most objects to 2 hours a night. I have vastly more data, but not all from the same scope and some of it is badly centred so only four nights have it more or less central in the FOV.

Looks the Biz! Why not 'bin' the numbers from the vane? I assume you will classify them into 16 or 32 sectors so you can draw a wind rose with the data. You just need to decide which reading defines the lower bound of each sector and use a series of compares to increment the right bin (and identify the current direction).

It took me four or five nights over two years! My 'RGB Challenge' entry just uses the final night's data and seems to be better on its own!

In recommended settings choose 'super pixels' this switches off debayering so red won't be affected by green and blue channels. This is so you can easily separate it later by splitting the final image into RGB layers and 'losing' G and B. It will be 1/4 the size of a normal DSLR image (1/2 as wide, 1/2 as tall). Stack as normal. Open photo editor and split channels to RGB, be surprised how much detail is in the G & B channels, but delete them and save R as a mono TIFF. If you later stack RGB data to provide colour to go with it you can use super pixel mode to get a colour image the same size to combine with it.

Got me to buy mine too. We should be on commission!

@jjosefsen that's very nice. I'm banging my head against 6 hours data for M33 and I can't get a decent colour balance.

Looking at those data, I wonder if the chip is slightly off-centre to the magnet axis?

Most likely the magnetic field is far from symmetrical.

In the dark, a USB B will fit snugly into an ST4 socket...

It's a headache to get it working and to set up all those extra wires, but once it's working, it's a joy!

Just seen the next page of comment heading towards a similar conclusion...

Unless it's sending and endless stream of 0xFF because something is stuck high?

No, just a very bad picture of M52

1200mm will give an image scale 24 time larger than a 50mm lens would, or for a crop sensor with a 70mm kit lens, 1200/70 = 17 times larger. You should only need more magnification if hunting very small targets. It will greatly increase the exposure times needed, which doesn't matter for bright planets. M52 is a pretty small DSO, this it using my 1200mm 150Pl with no additional magnification but using 'drizzle' to get a larger image scale.

Sorry, no - a 1200mm scope will work just like a 120mm telephoto.

Optical illusion - you can get the same 'foreshortening' by cropping a wide angle shot All the principles applying to digital apply once you project or print that film negative! For a 35mm film image to have the same FOV as we see, it needs to be just 12mm F/L. However, when looking through a film-based 35mm camera with a 50mm lens the view will be more or less identical to what you see with the naked eye - hence it being seen as 1:1.

Yes that's the simple truth, but you said the dreaded word 'magnification' and that gets the assembled masses dancing with the angels on the head of a pin.

Aha - the toothpaste tube approach! I imagine that gives very strong prints I haven't gone above 0.2 with a 0.4 nozzle, I must see how my printer handles things like that.

Out of curiosity what layer thickness are you using on the white parts? (I realise this is an area where a good solid print matters more than superb surface finish!)