G4AQB ASTRO WIKI

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Please add or edit your astro-imaging TOP TIPS to share!

Astro Imaging with a Skywatcher 130m

I have had the SkyWatcher 130M since March last year now and tried various things out to try to get the best out of the scope with my Toucam Pro II. I use Registax, Paint Shop pro and Photoshop to stack and enhance the images from the 130M. I must admit that I really like the scope for the price! Here are some tips that you might want to try when imaging Planets (or anything else really!) with the 130M:

Consider buying some more plossl eyepieces and definately a good quality 3x Barlow. I got them from Scopes n Skies.

Use a small spirit level placed on the assessory tray to level the mount before polar aligning.

Use a Red Spot Finder, makes polar alignment much easier and more accurate. Scopes n Skies sell one with the two holes which fit the 130M. I find that with the Red Spot Finder, just aligning onto the pole star and starting the RA Motor will usually track for quite a long time when imaging a planet.

Use good quality batteries for the RA motor Drive (Alkaline or Duracell)

A motorised focusser is worth it's weight in gold with the 130M, makes focussing without shakes so much easier! I got mine from www.switchedsystems.co.uk

I use my Toucam straight into the eyepiece holder or barlow, but I use a 10mm eyepiece with a parfocal ring to set the focus of the eyepiece with that of the webcam when finding and focussing Mars.

Stack as many avi's as you can in Registax and tick 'Gaussian' when using the wavelets...it's less harsh and nicer!

Imaging with a Toucam Pro II Webcam

The Philips Toucam Pro II (from PC World) has a sensitive CCD sensor and is great for imaging. It looks different because I had mine modified for long exposure images and put in a black box. The original lens that was fitted to the webcam is unscrewed and removed and this is replaced with a nosepiece (available from most astro dealers) The webcam is then used instead of an eyepiece and pushed into the draw tube. You first find your object with the eyepiece , then replace the eyepiece with the webcam. It's a bit tricky at first, especially getting the focus right! For Deep Space imaging no magnification is used at all, but for planetary imaging I use the barlow lens to make the image larger. You can also project an image from an eyepiece into the webcam, but i've never had much success with that method, so I use the webcam at prime focus. I also use a Logitech 3000 webcam which also works well, it has a CCD sensor as well.

With a webcam the images captured are video frames, you just use the software that comes with the camera and record a movie of say, 1 minute and you set the camera to 10 frames per second. You will then have 60 x 10 = 600 frames (ie 600 still images) These are then 'Stacked' one on top of another and processed using a piece of software called REGISTAX. This will then give you a final image which you save as .jpg or .bmp The more frames you capture for stacking, the better the image...well... in theory! I also use another program to capture called K3CCD which has a useful tool for changing the laptop screen into night vision. Small point but don't be surprised if you can't see the image straight away in the webcam even if you know it's there. You will need to focus OUT by quite a way in a lot of cases before the image becomes visible.

Here are some useful websites:

http://www.ukastroimaging.co.uk - Great guys - will answer any questions for starting out!

http://www.pk3.org - K3CCD Website

http://registax.astronomy.net/ REGISTAX Software

Some Assorted Tips

- Redlight astro torches are expensive - buy an LED rear brake light for a bike from a pound shop and save loads!

- Drilling holes in the patio for the feet of your mount to mark its position (and not collapsing the mount) means you can get away without drift aligning every time

- When trying to find a guidestar with a the two oversized guidescope ring type mountings, centre the OTA with the screws in the far ring then back off those in the ring closest to you completely. You can then wobble the scope around to find a star and screw them back in!

- When using a toucam for guiding don't use the preview in GuideDog to find a star. Use VRecord - it updates more often than guidedogs once a second.

- Your mount will be more stable if you keep the masses close to the axis. Mount the guidescope next to the OTA, not on top of it to keep it as close to the pivot as possible.

Tips For DSLR Users

- Putting the camera in a sealed plastic bag with silica gel stops dew forming on the sensor when going indoors to a warm house

- Remember you need to stack lots of Darks so as not to re-introduce noise into your stacked image. On a cold winters night (around 2-3 deg C) you can pack up early and stick the camera in the fridge to keep taking darks. Just remember to take the light bulb out.

- If your camera has an "auto rotate" function turn it off, otherwise your darks will not align properly.

- For long exposures (5mins or more) cover the eyepiece of the DSLR to stop light getting in.

Polar Alignment and Tracking of your scope

From the beginning, I'll start with Polar aligning - contrary to popular belief among non-astros, Polaris isn't actually EXACTLY on the North pole of the sky. It is VERY close though, about 3/4 of a degree away - that 3/4 of a degree makes a difference to imagers taking long exposures, but for the purposes of visual observing, it is near enough to make very little difference as far as tracking is concerned.

To align an equatorial mount to the Pole, you should first set the Declination to 90 degrees, orientation of the Right Ascension (RA) shouldn't matter in theory, but I always position the mount upright (with the weight rod pointing straight up/down) Lock the Dec and RA in position, and do the following adjustments without altering Dec or RA You then need to point the tripod and mount more or less North, and angle the head upwards to an angle that matches your lattitude - this is usually done with screws in front, and behind the mount, low down near where it attaches to the tripod. Almost all EQ mounts have a scale on the side, so you can get this fairly close. Then fine-tune it, so it is pointing at Polaris (or at the actual pole if you know where to find it - I'll explain that later) - You can either look through the scope to find Polaris (the Pole) or use the 'polarscope' if your mount has one. Left/right fine tuning can be done two ways - better EQ mounts have two screws (one each side) that you can use, or if the mount doesn't have those, you need to loosen the bolt underneath the head - turn carefully, left or right - then re-tighten it When you have Polaris (or the Pole) centred, lock those off - you are now polar aligned - do not move the tripod, or alter those settings for the duration of the observing session - use only RA and Dec axes to find your targets.

The TRUE pole:- As I said earlier, this is ABOUT 3/4 of a degree away from Polaris - It is in the direction of Kochab (the brightest star at the other end of Ursa Minor - Kochab is about halfway between Polaris, and the far end star of the 'Plough's handle) - What I do, is to look and see where Kochab is from Polaris, and mentally 'mark' the direction - then through the scope, I offset Polaris about 3/4 of a degree AWAY from the direction of Kochab, towards the edge of the field of view (remembering to allow for how the scope flips the image). I know that with my 25mm plossl, this is right on the edge of the field of view in my 900mm focal length scope, and just over 4/5 of the way to edge of the FOV as seen through my 750mm focal length scope. This method gets me near enough to the true North Pole that an object will stay in the field of view for at least 30mins, at HIGH magnification, when tracking with a motor. If you need more accuracy than that, you can learn to 'drift align' at a later date.

Tracking When a mount is polar aligned, the scope will follow the motion of a star across the sky by slowly rotating ONLY the RA axis - a motorised mount will automatically rotate the RA axis at the correct rate - If you have no motor, you can do it manually by twisting only the RA control knob - this is actually very easy to do - if you don't touch the control, you will see the star slowly move across your field of view, it's easy to match that movement by rotating the RA knob - becomes second nature after a while.

In short.. You point the RA axis at the Pole - and basically the Dec setting relates to how far an object is away from the Pole (+90 is North Pole, 0 is the celestial equator, -90 is the South celestial Pole) - The RA setting relates to how far around the celestial sphere an object is - by turning the RA control, you are following the track around the celestial sphere that an object moves.

That lot LOOKS longwinded - but as you do it yourself, the understanding soon comes to you - it's easier in practice, than it looks written down.

Polar Alignment with the Skywatcher 130

The FOV with your SkyWatcher 25mm eyepiece works out at almost exactly 2 degrees. So, centre to edge = 1 degree, which means that just over 3/4 of a degree (distance from Polaris to NCP) will be just over 3/4 of the way from the centre of your FOV, to the edge.

In short - If you get Polaris just over 3/4 of the way from the centre to the edge of you field of view (in your 25mm eyepiece) - in the direction AWAY from Kochab - then you will be pointed almost exactly at the North celestial Pole.

Should look like this

IMPORTANT - when deciding which direction Polaris should be from the centre, remember to allow for the way that your scope flips the image.

Good Luck

Carlos

(Thanks for your contribution Carlos! - Steve)

Some tips for imaging with a WebCam

For planetary imaging, a CCD Webcam - the Philips Toucam Pro II can be used without any internal modifications by simply unscrewing the webcam lens fitting and replacing with 1.25" nosepiece adaptor. I bought mine from Steven Mogg in Australia [1] The webcam is then pushed into the focuser instead of an eyepiece. This works fine for imaging the Moon, but for planets like Mars, Jupiter and Saturn I simply add a barlow between the webcam adaptor and the focus unit. I found that a 3x barlow seems to give the best results, however, the problem with using a barlow is that just touching the scope to adjust the focus causes the image to move out of the field of view. To stop this from happening I decided to add a remote focuser unit from [2] it is very easy to fit on the Skywatcher 130 and you can focus without touching the scope!

You can probably see on my photos that the webcam is in a 'black box' with a small fan mounted in the box. I sent my Toucam Pro II to have it modified so that you can take long exposure pictures needed for imaging Deep Sky Objects. As I mentioned, this is not needed for planetary imaging because the planet is bright and does not require long exposure. I fact all I do to capture images of planets is to record AVI video frames using either the software that comes with the webcam or download a copy of K3CCD Tools http://www.pk3.org/k3ccdtools/ this will allow you to capture and 'stack' each AVI video frame automatically. I also use another program called Registax 4 that I use to get the best results. http://www.astronomie.be/registax/

Hope this info is useful. My early attempts of taking photos of planets with a webcam were disappointing, but I quickly found that my images improved by 'trying out' and capturing as many AVI frames as possible with the webcam to 'stack' in Registax. I found that capturing around 2000 frames of video set at 10 frames per second gave good results. If you look at my pictures of Mars on my website you can see my learning curve! Good luck and remember..don't be put off by your first pictures, keep trying!