HELP! Questions in relation to tracking mount and capturing Saturn

[04Stefan07 (Stefan)]

Was out tonight from between 21:30 and midnight tonight. The plan was to capture some video of Saturn using my NexImage. I came across a few problems and wanted to ask for your help and maybe advise me on how to overcome these issues.

1) Using a Webcam/CMOS camera what is the best way to capture a planet?

I am using both SharpCap and iCap software.

The Moon is easy to capture obviously because it is a much bigger object in the night sky. The NexImage has a 5MP sensor so I put it on the max resolution, max gain and exposure in order to locate Saturn. I then focus it using the electronic focuser then I put the gain and exposure down and slowly minimise the resolution and increase the FPS (I tend to use offset on the x and y axis to keep Saturn centered). This is fine capturing it without using a Barlow but I want to get Saturn bigger so I chucked in a 2xBarlow and this is when it got hard.

2) Now that the image is zoomed in a lot more it is hard to centre Saturn. I was able to centre it but for some reason even though I have a mount that tracks objects in the night sky, on the screen Saturn is moving??!?!?!?! . It moves until it goes off screen. This only appears to happen when using the 2x Barlow. I double checked if the telescope is tracking and it is so I have no idea why Saturn stays centred!

3) Once I had Saturn centered and all ready to record I hit the record button and Saturn vanished. What the hell?!?!?!

4) Also what is software trigger?? I pressed it and I think it froze the image.

I did capture some video in the end but they didn't turn out good. I think this was due to the poor seeing conditions. No clouds tonight what so ever but seeing conditions were poor.

Can anyone help me? I know I can get decent shots of the Moon but I would like to also get decent shots of Saturn and Jupiter. Once I do I will feel better about doing Astrophotography.

I found this random photo on the Internet.

http://www.amazon.com/gp/customer-me...e=UTF8&index=1

That was taken with the same telescope as mine but with the older 1.4MP NexImage and 2x 2 Barlow Lenes.

I am sure I capable of taking something similar if not better with the NexImage 5.

I hope I can get a confidence boost

[04Stefan07 (Stefan)]

Anyone?

[rogerco (Roger)]

You don't say how well you had aligned the mount and whether or not the mount has goto tracking capability. I did exactly what you are doing back in march with the same results. without the barlow you will get away with rough alignment and just tracking. With the barlow you will need either to have goto tracking the planet for you (after a three star alignment) or you will need to have done a reasonable drift alignment. The fact that the mount can rotate to match the earth's movement will not keep the planet in the centre of the field of view if it isn't aligned. Sorry if I am stating the obvious.

[04Stefan07 (Stefan)]

Originally Posted by rogerco

You don't say how well you had aligned the mount and whether or not the mount has goto tracking capability. I did exactly what you are doing back in march with the same results. without the barlow you will get away with rough alignment and just tracking. With the barlow you will need either to have goto tracking the planet for you (after a three star alignment) or you will need to have done a reasonable drift alignment. The fact that the mount can rotate to match the earth's movement will not keep the planet in the centre of the field of view if it isn't aligned. Sorry if I am stating the obvious.

I did a Solar System Align (using Saturn to align the telescope). The mount does have a GoTo tracking ability.

[Lee]

Saturn does move relative to the stars of course, but your movement sounds a lot more than this.... are stars moving out of FOV similarly? - if so you need to sort out your polar alignment.
The Barlow will just magnify errors and make the drift faster...

[04Stefan07 (Stefan)]

Originally Posted by Lee

Saturn does move relative to the stars of course, but your movement sounds a lot more than this.... are stars moving out of FOV similarly? - if so you need to sort out your polar alignment.
The Barlow will just magnify errors and make the drift faster...

The weird thing is Saturn does not appear to move at all when I just have the high-powered eyepiece in because of the tracking but with the NexImage in it moves.

Could it be a software issue?

[OzEclipse (Joe Cali)]

It isn't the difference between the motion of Saturn and the stars. Saturn only moves about 12 degrees per year relative to the background stars. 2 minutes per day and only 15 arc seconds during your 3 hr observing session.

It's probably a balance issue caused by the weight of the camera or flexure if the camera is mounted in the barlow or flexure of the focuser..

Weigh the camera and put an identical weight on the opposite side of the tube and the same distance from the dec attachment point (ie down near the mirror)

Try this without the barlow. Even so. the focuser might not be strong enough to hold the camera. It might be flexure. During the day, put the camera on the scope and slew the scope to point at a fixed object. Turn off the drive and see if the image moves. Turn on the drive, slew to look at a fixed object in a different direction, repeat the test.

Good luck.

Joe

[04Stefan07 (Stefan)]

I will try all these tips mentioned here once there are some clear skies!

Cheers

[sil (Steve)]

Definitely seems a balance issue. I had the same on my 102SLT until I rebalanced during the day with my imaging cam attached. Also make sure the tripod is level (I assume it has the same bubble level as the 102SLT) as that upsets the balance. Don't forget to plug in all the cables you need for imaging as the weight of the cable from the cam will come into play with the balance, as will the slack of the cable...it if gets caught on the tripod or you have it pulled tight to a computer a long distance away this will add tension to the scope so it'll drift.

On the barlow front, the more magnification you add the more the seeing degrades for imaging (or an eyepiece). It's also adding more weight (and increasing the distance the camera is away from the balance point. So tracking will be even further put off.

You may also want to take a look as trying out FireCapture. I've switched to using that rather than SharpCap. Has some handy features, and cropping the resolution down to what I need gives me more frames per second for capture. It's not as stable and its more processor intensive but I definitely prefer it for now (I always avoided looking as I assumed it was for Firewire cameras only, but its not).

How good your image ends up now will be up to your processing skills